UNITED STATES ARMY AVIATION CENTER FORT RUCKER, ALABAMA JUNE 2008

Transcription

1 UNITED STATES ARMY AVIATION CENTER FORT RUCKER, ALABAMA JUNE 2008 STUDENT HANDOUT (LOT 11) TITLE: AH-64D Rotors/Vibration Analysis FILE NUMBER: 11-XXXX-4.0 This Package Has Been Developed For Use By: AH-64D Maintenance Test Pilot Course Proponent For This Tsp Is: United States Army Aviation School Fort Rucker, AL FOREIGN DISCLOSURE STATEMENT: This product/publication has been reviewed by the product developers in coordination with the Ft. Rucker foreign disclosure authority. This product is releasable to students from foreign countries on a case by case basis Distribution authorized to U.S. Government agencies and their contractors; Critical Technology August 10, Other requests for this document will be referred to Department of the Army, PEO Aviation Apache, SFAE-AV-AAH-LI, Apache Attack Helicopter, Bldg. 5681, Suite 174, Redstone Arsenal, AL COMM (256) or DNS

2 TERMINAL LEARNING OBJECTIVE: At the completion of this lesson you (the student) will: ACTION: Identify the characteristics of the AH-64D rotor system. ACTION: Given an AH-64D helicopter, a Maintenance Support Device (MSD), with TM Longbow/Apache Interactive Electronic Technical Manual (IETM) software, TM , TM CL, and TM MTF. STANDARD: In accordance with TM Longbow/Apache IETM, TM , TM CL, and TM MTF. D-4

3 PFN 011-XXXX-4.0 A. Enabling Learning Objective 1 ACTION: Identify the characteristics of the Rotor Systems. CONDITIONS: Given a written test without the use of student notes or references. STANDARD: In accordance with TM and TM APACHE/LONGBOW (IETM). 1. Learning Step/Activity 1: Identify the purpose, location, and description of the rotors. Figure 1. AH-64D Rotor System a. Rotor System The purpose of the rotor system is to provide lift, thrust, directional flight, and anti-torque control for the helicopter. The main rotor assembly consists of the main rotor head assembly and the main rotor blade assembly. The tail rotor assembly consists of the tail rotor head assembly and the tail rotor blade assembly. D-5

4 Figure 2. Main Rotor System (1) Main Rotor System The main rotor system provides lift and directional flight for the helicopter. It is mounted on the static mast above the main transmission and is a single, four-bladed, fully articulated main rotor assembly. It has a diameter of 48 feet and turns in a counterclockwise rotation. Flight loads developed by the main rotor are transferred to the airframe through the static mast and mast support base. D-6

5 PFN 011-XXXX-4.0 Figure 3. Main Rotor Head Assembly (a) Main rotor head assembly The main rotor head provides a means to mount, drive, and control the main rotor blades. It also provides feathering, flapping, and lead-lag movement of each blade. It weighs approximately 607 pounds and is approximately 78 inches in diameter. D-7

6 Figure 4. Main Rotor Hub Assembly Cutaway (1) (b) Main rotor hub assembly major components: 1) Hub subassembly 2) Upper and lower load plates 3) Stretch strap assembly 4) Lower shoe 5) Seals and retainer (upper, center, and lower) 6) Tapered roller bearings (upper and lower) 7) Feathering bearing stud 8) Feathering bearing housing/striker plate D-8

7 PFN 011-XXXX-4.0 Figure 5. Main Rotor Hub Subassembly (c) Hub subassembly The hub subassembly provides for attachment of the upper and lower load plates, the stretch strap assembly, and the lower shoe. The hub subassembly also provides alignment points (feathering bearing stud attach holes) for the pitch housing assembly feathering and flapping axes. The hub is aluminum alloy forging and contains the air vehicle sling attach bushings and the droop stop liner. D-9

8 Figure 6. Main Rotor Hub Assembly Exploded View (d) (e) (f) Upper and lower load plates The upper and lower load plates provide the interconnects for the strap assembly to the hub and carry the centrifugal loads received from the main rotor blades through the strap assembly to the hub. The load plates are installed between the hub subassembly and the lower shoe. Stretch strap assembly 1) The strap assemblies transmit centrifugal loads from the main rotor blades to the hub and allow for mechanical pitch change, flapping, and feathering motions of the blades. 2) Each assembly is made of 22 V-shaped stainless steel laminates stacked one on top of the other. Each laminate is separated by a spacer, consisting of a Teflon strip, and cellophane at the inboard mounting point. 3) The strap assemblies mount between the upper and lower load plates between the hub subassembly and lower shoe. The strap assemblies are installed using special one-time-use Pre-Load Indicating (PLI) washer sets. Lower shoe assembly The lower shoe secures the upper and lower load plates and strap assemblies to the hub subassembly. It also provides attachment lugs to drive the scissors assemblies and housing ports for the droop stop follower assemblies. The lower shoe is mounted on the lower part of the hub assembly. D-10

9 PFN 011-XXXX-4.0 Figure 7. Seals and Tapered Roller Bearings (g) (h) Seals and retainers (upper, center, and lower) The seals and retainers prevent grease from leaking past the upper and lower tapered roller bearings. 1) The upper seal is mounted in the hub assembly between the upper tapered roller bearing and the hub retaining nut. It is held in place by a corrosion resistant steel retainer. 2) The center seal is mounted into the hub subassembly between the upper tapered roller bearing and the lower tapered roller bearing. 3) The lower seal is mounted below the lower tapered roller bearing and is held in place by a retainer. It rests against the static mast liner. The lower retainer is an aluminum alloy plate that contains eight holes. Four of the holes go through the retainer and are used for removal of the retainer. The other four holes are threaded approximately ¾ of the way through and are used to mount the ground brush assemblies. Tapered roller bearings (upper and lower) The tapered roller bearings carry the radial and axial loads, allowing the main rotor head to rotate around the static mast. The upper tapered roller bearing is installed between the upper and center seals on the hub subassembly. The lower tapered roller bearing is installed above the lower seal on the hub subassembly. D-11

10 Figure 8. Feathering Bearing Stud (i) Feathering bearing stud The feathering bearing stud secures the feathering bearing housing assembly to the hub subassembly. There are four studs mounted diametrically opposed to the hub subassembly. They are threaded on both ends; one end has a rectangular key at the end of it. The key aligns with a retainer that prevents the stud from rotating once installed. D-12

11 PFN 011-XXXX-4.0 Figure 9. Feathering Bearing Housing Assembly (j) Feathering bearing housing/striker plate The feathering bearing housing provides the pivot point for the main rotor blade flapping and feathering action and provides the mounting point for the pitch housing assembly. The feathering bearing housing prevents lead/lag of the pitch housing assembly by using the rigidity of the strap assembly coupled with the feathering bearing. 1) The feathering bearing housing is located between the pitch housing assembly and hub subassembly, and is mounted on the feathering bearing stud. The feathering bearing housing is made of an aluminum alloy with a spherical elastomeric bearing mounted in the center. 2) The striker plate mounted at the lower inboard surfaces of the feathering bearing housing assembly provides the contact surface for the droop stop follower assembly s roller to ride on during startup, pitch changes, and shutdown. It also provides the adjustment of blade static droop angle. The striker plates are made of corrosion-resistant steel plate and can be shimmed for adjustment of the main rotor blade static droop angle. D-13

12 Figure 10. Main Rotor Head Assembly Components (k) Main rotor head assembly components: 1) Pitch housing assembly 2) Lead-lag link assembly 3) Damper assembly 4) Ground brush assembly 5) Droop stop follower 6) Feathering bearing housing assembly D-14

13 PFN 011-XXXX-4.0 Figure 11. Pitch Housing Assembly (l) Pitch housing assembly The pitch housings provide the means for controlling the main rotor blade pitch angle. It also provides mounting and interfacing for the stretch strap assembly (outboard end), lead-lag link, and damper assemblies. The pitch housing is attached to the feathering bearing housing assembly. The pitch housings must not weigh more than 26.9 pounds. Each opposing pitch housing must be within 1.5 pounds of the opposite one. The striker strips provide a contact point in the event of excessive pitch housing lead-lag movement. The bonding wires provide a connection from the pitch housing to the main rotor hub subassembly, which assists in preventing the build-up of static electricity on the rotor blades and pitch housings. D-15

14 Figure 12. Lead-Lag Link Assembly, Hinge Pin, and Bearings (m) Lead-lag link assembly, hinge pin, and bearings The lead-lag link, hinge pin, and bearings provide mounting of the main rotor blade and, in conjunction with the damper assemblies, allow lead-lag movements of the main rotor blades. The lead-lag link assembly, hinge pin, and bearings also secure the outboard end of the strap assembly and pitch housing assembly. They are mounted to the outboard end of the pitch housing. The bearings are flanged aluminum alloy assemblies, which secure the steel hinge pin, and allow the lead-lag unit to pivot fore and aft. There are two retainers, one on top and one on the bottom, which secure the bearing assembly in the pitch housing to ensure they do not rotate. D-16

15 PFN 011-XXXX-4.0 Figure 13. Damper Assembly (n) Damper assembly The main rotor dampers control lead-lag movements of the main rotor blades and prevent mass unbalance (unequal blade spacing). There are two dampers per pitch housing, one on the leading edge and one on the trailing edge. They are mounted between the inboard end of the pitch housing assemblies and the lead lag links. The dampers are constructed of an elastomeric rubber compound bonded to a center metal plate, sandwiched and bonded to two outer plates. The outboard end has a threaded insert (heli-coil) for an adjustable rod end bearing. D-17

16 Figure 14. Ground Brush Assembly (o) Ground brush assembly The ground brush assembly transfers static electricity from the main rotor hub to the static mast preventing static electricity build-up from causing erosion of the tapered roller bearings on the main rotor hub. The ground brushes are mounted on the lower seal retainer and are 180 apart from each other. D-18

17 PFN 011-XXXX-4.0 Figure 15. Droop Stop Follower and Feathering Bearing Housing Assembly (p) Droop stop follower and feathering bearing housing assembly 1) Droop stop follower assembly The droop stop follower restricts downward blade flap excursion (one blade down, opposite blade up). The droop stop follower assembly limits downward coning (all blades down simultaneously). The droop stop follower is installed in the lower shoe assembly and held in place by the droop stop ring. The striker plate mounted at the lower inboard surfaces of the feathering bearing housing assembly provides the contact surface for the droop stop follower assembly roller. 2) Droop stop ring The droop stop ring works in conjunction with the droop stop follower assembly. It restricts main rotor blade downward coning and downward blade flap excursion. The droop stop ring is mounted in the lower portion of the lower shoe, and is held in place by the four droop stop follower assemblies. D-19

18 Figure 16. Main Rotor Hub Assembly Cutaway (2) (q) Main rotor hub retention and drive components 1) Hub retention nut and hub retention ring 2) Drive plate and drive plate cover 3) Flexible support assembly 4) Main rotor blade assembly D-20

19 PFN 011-XXXX-4.0 Figure 17. Main Rotor Hub Retention Nut Installation (r) Main rotor hub retention nut and hub nut retention ring The hub retention nut and hub nut retention ring are mounted on the static mast within the main rotor head. The hub retention nut and hub nut retention ring are used to attach the main rotor head assembly to the static mast. The hub retention nut threads onto the static mast on top of the bearing retainer. The hub nut retention ring is placed on top of the retention nut so that its tangs line up with the slots in the static mast. The hub retention nut is then rotated slightly so that the holes in the retention ring align with the holes in the retention nut. The retaining bolts are then torqued in a sequence that applies equal pressure to the bearing retainer and preloads the upper and lower tapered roller bearings. When complete, the retaining bolts are safety wired in groups of three. D-21

20 Figure 18. Main Rotor Drive Plate Installation (s) Main rotor drive plate The drive plate transfers rotating motion from the main rotor drive shaft to drive the main rotor head assembly. The drive plate is bolted on top of the main rotor hub and splined directly to the main rotor drive shaft. The drive plate seal and packing retain the grease lubricant in the drive plate to lubricate the drive shaft splines. D-22

21 PFN 011-XXXX-4.0 Figure 19. Flexible Support Assembly Installation (t) Flexible support assembly The flexible support allows the main rotor drive shaft to float inside the static mast. The assembly is constructed of a rubber inner core bonded to a metal center and outer frame. The flexible support is installed inside the upper end of the main rotor drive shaft and is bolted to the main rotor drive plate cover. D-23

22 Figure 20. Main Rotor Blade Assembly Dimensions (u) Main rotor blade assembly The four main rotor blades provide the lift and directional flight capability for the helicopter. They are installed on the main rotor head lead-lag links. Each blade is 20 feet, 10 inches long, and 21 inches wide. Each blade weighs 157 pounds and this number is normally stenciled to the right of the Center of Gravity (CG) marker on the blade. A swept tip on the blade aids in better lift capability and reduces noise. D-24

23 PFN 011-XXXX-4.0 Figure 21. Main Rotor Blade Root Assembly (1) (v) Main rotor blade root assembly components 1) Six titanium root fittings 2) Five upper and five lower stainless steel doublers 3) Aluminum alloy closing rib 4) The six root fittings, closing rib, doublers, and skin are bonded together and secured by four bolts; bolts also allow for the installation of balance weights. 5) The extreme inboard portion of the root fitting has four mounting lugs to secure the blade to the lead-lag link. D-25

24 Figure 22. Main Rotor Blade Sectional View (w) Main rotor blade construction The blade forward section is a four-cell unit consisting of stainless steel spars bonded over preformed fiberglass tubes. 1) The single-piece No. 1 spar forms the leading edge. 2) The No. 2 and 3 spars are two-piece spars (top and bottom). 3) The No. 4 spar is formed by a single piece of stainless steel. 4) A stainless steel balance bar runs the entire length of the blade. 5) Four fiberglass preformed tubes are bonded to the inner skin of the spars to retard crack propagation. 6) The blade aft section consists of a Nomex honeycomb core bonded to an upper and lower fiberglass skin bonded. The aft section of the blade is bonded to the No. 4 spar. 7) The trailing edge consists of a one-piece stainless steel skin bonded to a Nomex honeycomb core. The trailing edge is bonded to the blade aft section. One inch of the trailing edge is a bendable tab used to adjust the in-flight tracking characteristics of the rotor blades. D-26

25 PFN 011-XXXX-4.0 Figure 23. Main Rotor Blade Swept Tip 8) Main rotor blade swept tip The main rotor blade swept tip consists of a removable leading edge tip. Screws along the upper and lower surface secure the removable leading edge tip. The swept tip consists of six upper and lower stainless steel doublers and a fiberglass fabric core. Two sets of preset tip weights are installed in the blades and covered by the swept tip. The swept tip also provides a attachment point for blade targets used during rotor blade tracking or phasing. D-27

26 Figure 24. Blade Attachment Pin 9) Blade attachment pins The blade attachment pins attach and secure the main rotor blades to the lead-lag links of the main rotor head. The pins are installed through the main rotor, the lead-lag links, and blade retention fittings. The attachment pins are expandable type pins that have an adjustment nut for setting the proper closing force and a safety latch that secures them in the closed position. D-28

27 PFN 011-XXXX-4.0 Figure 25. Tail Rotor System b. Tail Rotor System The tail rotor system provides anti-torque and directional flight heading capability for the helicopter. The tail rotor head is installed on the tail rotor gearbox output shaft and uses a single, four-blade, teetering, tail rotor blade assembly. The tail rotor assembly is 9.2 feet in diameter and turns in a clockwise rotation. The blades have a narrow angle spread of 55. D-29

28 Figure 26. Tail Rotor Head Assembly (1) Tail rotor head assembly The tail rotor head provides attaching points for the tail rotor blades and the means to drive the blades. The tail rotor head is mounted to the curvic coupling on the tail rotor gearbox output shaft and is secured by three stud/nut combinations. (2) Tail rotor head assembly components (a) (b) (c) (d) Fork assembly The fork assembly provides mounting points for the tail rotor hubs. Elastomeric bearings The four elastomeric bearings allow the hubs to teeter (seesaw) on the forks. The bearings are bonded on the output end of the forks. Tail rotor hubs The two tail rotor hubs provide a mounting point for the tail rotor blades and are installed on the fork assembly. Strap assemblies The two strap assemblies provide a means for installing the tail rotor blades to the tail rotor head assembly. The strap assemblies transmit loads from the tail rotor blades to the head assembly and allow the feathering motion of the blades. The strap assemblies pass through the hub and are mounted to the center of the hub with threaded bushings. The strap assembly is made from 22 stainless steel laminates. D-30

29 PFN 011-XXXX-4.0 Figure 27. Tail Rotor Blade Assembly (3) Tail rotor blade assembly The four tail rotor blades provide anti-torque and the thrust to maintain the desired direction of flight. The tail rotor blades are mounted over the hub and secured to the strap assembly by a PLI washer, bolt, and nut combination. Each tail rotor blade is inches long and 10 inches wide. Each tail rotor blade has tip weights installed under the tip cap for adjustment of tail rotor blade balance. Other components that are included with the tail rotor blade assembly include the following. (a) (b) (c) Pitch horn The pitch horn is riveted to the root fitting and provides attachment for the pitch change links, the de-ice blanket electrical receptacle, and the static bonding cable. The pitch horn contains a steel bushing to attach the pitch change link. Root fittings The root fittings are made of aluminum forgings, with four, aluminum doublers. The root fitting and doublers are joined to the spars by adhesive bonding and metal fasteners. Self-lubricating Teflon bearings Two self-lubricating Teflon bearings are bonded to the inside diameter of the root fitting. The bearings allow blade rotational movement around the hub. The inboard section of the root fitting provides the blade attachment point. D-31

30 Figure 28. Tail Rotor Blade Construction (4) Tail rotor blade construction The tail rotor blade construction is similar to main rotor blade construction. (a) (b) Tail rotor blade No. 1 spar is made of stainless steel, which forms the leading edge. Each spar is lined with unidirectional bonded fiberglass to retard crack propagation. The tail rotor blade No. 2 and No. 3 spars are made of aluminum alloy. The No. 3 spar has 11 aluminum honeycomb stiffeners bonded into the spar to add strength to the blade. D-32

31 PFN 011-XXXX-4.0 CHECK ON LEARNING 1. Flight loads developed by the main rotor are transferred to the airframe through the: ANSWER: 2. The striker plate mounted at the lower inboard surfaces of the feathering bearing housing assembly provides: ANSWER: 3. The main rotor pitch housings must not weigh more than and each opposing pitch housing must be within of the other. ANSWER: 4. The main rotor dampers control lead-lag movements of the main rotor blades and prevent: ANSWER: 5. The purpose of the drive plate is to: ANSWER: D-33

32 B. Enabling Learning Objective 2 After this lesson you will: ACTION: Identify the characteristics of the main rotor blade phasing procedures. CONDITIONS: Given a written test without the use of student notes or references. STANDARD: 1. Learning Step/Activity 1 In accordance with TM and TM APACHE/LONGBOW (IETM). Figure 29. Main Rotor Blade Phasing a. Main Rotor Blade Phasing Phasing the main rotor blades aligns the four main rotor blade assemblies to each other. This establishes a 90 relationship between the blades and ensures satisfactory spanwise balance of the rotor assembly. Careful performance of phasing procedures will permit dynamic balancing in the shortest time. D-34

33 PFN 011-XXXX-4.0 Figure 30. Target Assembly Installation b. Blade phasing equipment consists of the phasing target assembly (with bubble level), phasing tool (support), and telescope or laser with a battery pack. (1) Phasing target assembly The phasing target is a reference point for blade alignment; in other words, the reference point to level the blade. The target is installed on the tip cap of the blade being aligned. The target is an L-shaped aluminum bracket with two mounting holes and a leveling bubble mounted on the top. (2) Phasing tool The phasing tool provides mounting support for the laser or telescope. The tool is installed on the main rotor hub with laser or telescope pointing toward the target. (3) Telescope The telescope provides precise alignment and is mounted on the phasing tool. The telescope is an optical tube with internal crosshairs. (4) Laser with battery pack The laser provides pinpoint accuracy for alignment. The laser is mounted on the phasing tool and is a tube-shaped laser designator with optional battery pack. (5) Installation of the phasing tools D-35

34 The phasing target is installed with the vertical centerline facing inboard and the bubble level facing upwards. The phasing tool may be used with either the laser or the telescopic sight. This procedure is performed on each blade. Figure 31. Blade Phasing Procedures c. Blade Phasing Adjustment The phasing of the blades is accomplished by adjusting the adjustable rod ends of the main rotor blade dampers where they attach to the lead-lag unit. The rod ends are adjusted so the target picture is centered on the target. D-36

35 PFN 011-XXXX-4.0 CHECK ON LEARNING 1. Phasing the main rotor blades aligns the four main rotor blade assemblies to: ANSWER: 2. Where is the blade-phasing target installed? ANSWER: 3. What is the function of the phasing tool? ANSWER: 4. Blade phase adjustments are made where? ANSWER: D-37

36 C. Enabling Learning Objective 3 After this lesson you will: ACTION: Identify the characteristics of the Rotor System Displays. CONDITIONS: Given a written test without the use of student notes or references. STANDARD: 1. Learning Step/Activity 1 In accordance with TM and TM APACHE/LONGBOW (IETM). Figure 32. MPD Engine Page a. Rotor System Displays (1) A monopole sensor in the main transmission monitors the revolutions per minute (rpm) of the main rotor. The signal it generates is sent to the System Processor (SP). The crew can read the main rotor rpm percentage (N R %) on the Engine page (101% = 292 rpm). D-38

37 PFN 011-XXXX-4.0 Figure 33. Up Front Display (UFD) (2) When the SP determines that the main rotor rpm is above 105% or below 95%, it generates a signal to display a warning message on the MPDs and UFDs. It also illuminates the master warning light and initiates a voice warning to the crew. The ENG page and associated warning will be displayed on the left MPD in each crewstation. (a) (b) (c) (d) (e) UFD warning: LOW ROTOR RPM 1) Displayed on the UFD in each crewstation. 2) Warns the crew whenever the main rotor speed decreases below 95%. UFD warning: HIGH ROTOR RPM 1) Displayed on the UFD in each crewstation. 2) Warns the crew whenever the main rotor speed exceeds 105%. MPD warning: LOW ROTOR RPM Warns the crew whenever the main rotor speed decreases below 95%. MPD warning: HIGH ROTOR RPM Warns the crew whenever the main rotor speed exceeds 105%. Voice message warnings of main rotor status. 1) ROTOR RPM LOW 2) ROTOR RPM HIGH D-39

38 Check On Learning 1. What does the UFD Warning LOW ROTOR RPM indicate? ANSWER: 2. What does the UFD Warning HIGH ROTOR RPM indicate? ANSWER: 3. When the SP determines that the main rotor rpm is above 105% or below 95% what does it do? ANSWER: D-40

39 PFN 011-XXXX-4.0 D. Enabling Learning Objective 4 After this lesson you will: ACTION: Identify the characteristics and causes of helicopter and Rotor System Vibrations. CONDITIONS: Given a written test without the use of student notes or references. STANDARD: 1. Learning Step/Activity 1 In accordance with TM and TM APACHE/LONGBOW (IETM). Figure 34. Types of Vibrations a. Very Low Frequency Vibrations For the AH-64D, vibrations in the range of 0 3 Hz are attributable to aircraft handling qualities. These vibrations feel like a gentle yawing, or rolling, or most often, porpoising (pitching) of the aircraft. NOTE: Very low frequency vibrations do not exist in the AH-64D because it does not use a soft pylon mounting structure or adjustable main rotor trunnion. b. Low Frequency Vibrations Low Frequency (LF) vibrations occur at a frequency of 3 to 10 cycles per second. Examples include lateral vibration and vertical vibration at the once-per-revolution frequency of the main rotor. (1) Main rotor one-per-revolution vibrations (1P) feel like a rocking (lateral) or bouncing (vertical) motion. D-41

40 (2) Main rotor 1P vibrations are caused by the main rotor system being out of track or balance. (a) (b) Blade-to-blade mass balance differences (spanwise or chordwise) normally result in one-per-revolution lateral vibrations. Out of track conditions, which result from differences in lift between main rotor blades, will be felt as a one-per-revolution vertical vibration. NOTE: It may be necessary to accept a blade slightly out of track to eliminate a one-per-revolution vertical vibration. (c) (d) (e) The one-per-revolution vibration exists in the AH-64D (4.86 Hz) and is likely to be the type of vibration most frequently encountered during vibration analysis. The one per revolution vibration is the only main rotor vibration component, which is directly controllable through prescribed maintenance procedures. Main rotor 2P vibrations (9.72 Hz) are also normally in this frequency range. c. Medium Frequency Vibrations Medium Frequency (MF) vibrations occur at a frequency of cycles per second and feel like chatter or shudder. (1) Main rotor 4P vibrations and tail rotor 1P vibrations are normally in this frequency range. (2) Normal main rotor 4P vibrations are felt when the helicopter passes through translational lift or during high G maneuvers. (3) Abnormal main rotor 4P vibrations may be caused by worn or loose components in the rotor and control system. (4) Normal tail rotor 1P vibrations are the result of blade-to-blade mass balance differences resulting in rotor imbalance about the center of rotation. These vibrations are in the plane of rotation and are minimized by performance of tail rotor ground balance maintenance. (5) Abnormal tail rotor 1P vibration, which cannot be controlled through normal tail rotor dynamic balance, may result from worn or loose tail rotor components. (6) For the AH-64D, main rotor 4P is at Hz; tail rotor 1P is at Hz. (7) Main rotor 4P is normal when associated with translation or high dynamic rotor loading. (8) AH-64D tail rotor 1P, when associated with rotor dynamic balance, is controllable. Therefore, under normal conditions for a properly maintained aircraft, tail rotor 1P should not be sensed. d. High Frequency Vibrations High Frequency (HF) vibrations occur at frequencies of 25 to 100 cycles per second. They feel like a buzz or hum, most often noticed by crewmembers through their feet. (1) Normal high frequency vibrations are associated with higher harmonics of the main rotor and tail rotor rotational speeds. For the AH-64D, main rotor 8P (38.95 Hz) and 12P (58.44 Hz), and tail rotor 2P (47.25 Hz) and 4P (94.50 Hz) are the most prevalent frequencies. D-42

41 PFN 011-XXXX-4.0 (2) Abnormal high frequency vibrations may be associated with tail rotor drive shaft imbalance. For the AH-64D, these frequencies are 60 and 80 Hz, the rotational speeds of the intermediate and tail rotor drive shafts. Maintenance cautions are triggered by excessive vibrations at these frequencies as a part of the permanent, fulltime tail rotor gearbox vibration monitoring system. Vibration of the tail rotor drive shafts should be minimized as soon as possible to prevent potential additional or catastrophic failures of the tail rotor system. e. Very High Frequency Vibrations Very High Frequency (VHF) vibrations occur at a frequency of greater than 100 cycles per second. They feel like a buzz or hum and may be audible. (1) May be caused by any high-speed rotating component (fan, generator, driveshaft, etc.) or malfunctioning pressure relief valves and similar items. (2) This type of vibration should be eliminated or minimized as soon as possible to prevent potential catastrophic failures of the associated system or component. (3) Gear clash frequencies trigger the tail rotor vibration warning system. Figure 35. Vibration Source Chart f. Vibration Source Chart This chart provides a quick reference for the vibration frequencies and associated components on the AH-64D. D-43

42 CHECK ON LEARNING 1. What are vibrations in helicopters typically classified by? ANSWER: 2. What type vibration will you likely expend most of your analysis efforts on to eliminate or minimize? ANSWER: 3. Normal main rotor 4P vibrations are felt when: ANSWER: 4. Very high frequency vibrations occur at a frequency of greater than: ANSWER: D-44

43 PFN 011-XXXX-4.0 E. Enabling Learning Objective 5 After this lesson you will: ACTION: Identify the characteristics of the main rotor system track and balance procedures. CONDITIONS: Given a written test without the use of student notes or references. STANDARD: 1. Learning Step/Activity 1 In accordance with TM and TM APACHE/LONGBOW (IETM). a. Main Rotor Adjustments (1) Main rotor track and balance maintenance is performed to minimize, specifically and exclusively, main rotor 1P vibration. Other main rotor vibration components are not directly controlled or affected by track and balance maintenance. (2) The main rotor adjustments that can be used for control of 1P vibration are: (a) (b) (c) Pitch links Hub weights Blade tabs Figure 36. Pitch Link Assembly 1) Pitch change link adjustments D-45

44 a) Prior to loosening the jam nuts on the pitch change link, mark the barrel for reference. b) To determine which way to turn the pitch link barrel to raise or lower the blade, grasp the barrel with the right hand, thumb extended up. Turning the barrel the same direction as your fingers are pointed will raise the blade up. Turning the barrel in the opposite direction will lower the blade. Figure 37. Polar Chart (PCL Lat) c) Pitch links are adjusted during track and balance to reduce vertical vibration and track spread. 1 Ground track and balance (101% N R and collective full down) a b c Pitch links are adjusted to reduce track spread. For this condition, a one flat adjustment results in approximately 0.4 inch at the tracker viewing point. In addition to affecting track, pitch link adjustments also result in a change to lateral vibration. For example, a one flat change to blade No.1 will result in approximately 0.04 Inches Per Second (IPS) change in lateral vibration in the direction of approximately 16 on the polar chart. If necessary, a pitch link move may be accompanied by a weight move to counter any increase in lateral vibration. D-46

45 PFN 011-XXXX-4.0 d Pitch link moves, to control track spread, also affect vertical vibration. Controlling track spread normally controls ground vertical vibration, although this is not the direct intent for ground track and balance. Figure 38. Polar Chart (PCL Vert) 2 Forward flight track and balance a b c d Pitch links are adjusted primarily to reduce vertical vibration with a secondary objective of reducing track spread. For example, at 140 Knots True Airspeed (KTAS), a one flat change to blade No.1 changes vertical vibration by approximately 0.25 IPS, in the direction of approximately 250 on the polar chart. In other words, in order to reduce a 1P vertical vibration of 0.25 IPS at 140 KTAS with a phase angle of 250 using blade No.1 pitch link, you would shorten blade No.1 pitch link by 1 flat. Lengthening blade No.3 pitch link by 1 flat has the same effect. A one flat change to a pitch link will result in approximately 0.8 inch of track change at 140 KTAS as measured by the Universal Tracking Device (UTD). D-47

46 Figure 39. Main Rotor Tab Bending Stations 2) Blade tab adjustments a) The main rotor blade has 11 stations (pockets 0 through 10) starting with pocket 0, which is 6 inches inboard of the electrostatic discharger. Each pocket is 10 inches in length. b) Maximum allowable tab edge bend is 5. Do not bend tab more than 5 from 0 position on tab bending tool. c) Pockets 0 through 3 are not routinely used. Adjust pockets 0 through 3 with caution (only half degree at a time, not to exceed 1 total), only if pockets 4 through 10 are inadequate to bring 1P vibration within limits. d) Pockets 4 through 10 are for in-flight vibration and track of KTAS. e) Tab bend corrections called out on the diagnostics display will refer to the start of a continuous bend. For example, if the display recommends 1 up at pocket 4 10, the bend should start at pocket 4 and continue through pocket 10. 3) Tab bending a) Place the tab adjustment tool in the center of the tab pocket to be bent. Tab pockets 0 through 10 are 10 inches in length, starting 6 inches inboard of swept tip. Do not bend inboard of pocket No.10. D-48

47 PFN 011-XXXX-4.0 b) Do not make bends in opposite directions in adjacent pockets. It is preferable to remove an upward bend (reset to 0º) if the adjacent pocket requires a downward bend. c) Any noticeable deformity (kinks or sharp edges caused by the tab bending tool) is cause for rejection of the blade. d) Maximum tabbing should not exceed 5 to prevent tab damage and/or tab washout with increasing aircraft flight hours. e) Do not bend the trim tab outboard of pocket 0. This area is very sensitive for tracking. f) Avoid bending tab between pockets 0 and 3 unless absolutely necessary. g) Do not bend tab inboard of pocket 10. h) Bending a tab up raises a blade. Bending a tab down lowers a blade. i) The tab adjustment is divided into three regions which reflect the differences in the sensitivities with speed: 1 Pockets 4 10 are used primarily to control vibration and track from KTAS. 2 Pockets 6 10 are used primarily to control vibration and track from KTAS. 3 Pockets 8 10 are used primarily to control vibration and track at 140 KTAS. NOTE: Any tab bend affects vibration and track at all speeds; but, for example, the effect of a pocket 8-10 bend at 60 KTAS is much less than its effect at 140 KTAS. j) The Aviation Vibration Analyzer (AVA) triggers the 3 tab regions as follows: 1 Pockets 4-10 are turned on if the track change of any given blade between hover and 80 KTAS is 0.5 inch or more. 2 Pockets 6 10 are turned on if the hover to 120 KTAS track change is 0.5 inch or more. 3 Pockets 8 10 are turned on if the hover to 140 KTAS track change is 0.5 inch or more. D-49

48 Figure 40. Polar Chart (8 10 Vert) D-50

49 PFN 011-XXXX-4.0 Figure 41. Polar Chart (6 10 Vert) Figure 42. Polar Chart (4 10 Vert) k) Tabs are primarily used to reduce one per-rev-vertical vibration in forward flight with a secondary objective of reducing track spread. 1 At 140 KTAS, a 1 change to blade No.1 pockets 4 10 will result in approximately a 1 IPS vertical 1P vibration change, in the direction of about 250 on the polar chart. 2 In other words, a 1 downward bend in blade No.1 pockets 4 10 will reduce to 0 a 1 IPS vertical vibration with a phase angle of 250, measured at 140 knots. An upward bend in blade 3 (opposite blade), pockets 4 10 will have the same effect on vibration. 3 A 1 bend in pockets 4 10 will change the blade track at 140 KTAS by approximately 1 1/2 inches as measured by the UTD (which equates to about 3 inches at the blade tip). D-51

50 Figure 43. Main Rotor Sensitivities of Blade Track Height to Tab Bend l) Keep tab bends to a minimum. D-52

51 PFN 011-XXXX-4.0 Figure 44. Balance Weight Main Rotor Blade (d) Blade weight adjustments 1) Corrections are made by adjusting weight stack-ups at the main rotor blade root attaching point. 2) Nine weights maximum may be attached at the blade root, not to exceed 1017 grams. 3) The mass of the weights depends on the material and are approximately: a) grams (0.060 inch tungsten) b) grams (0.063 inch 301 cres.) D-53

52 Figure 45. Polar Chart (Wt Lat) 4) Weights are used primarily to reduce 1P lateral vibration on the ground and at a hover. For flat pitch on the ground at 101% N R, a 113 gram (one -3 weight) weight change made to blade No.1 will change lateral vibration by approximately 0.05 IPS in the direction of approximately 165 on the polar chart. 5) Adjustments are not made because of lateral 1P vibration in forward flight tends to be consistent with hover and ground lateral 1P vibration. Therefore no correction are needed. D-54

53 PFN 011-XXXX-4.0 Figure 46. Polar Chart (Wt Vert) 6) Weights also affect forward flight 1P vertical vibration. For example, addition of one -3 weight (113 grams) to blade No.1 will change vertical vibration at 140 KTAS by approximately 0.05 IPS in the direction of approximately 240 on the polar chart. As a result, weights may be used by the AVA algorithm to reduce forward flight vertical 1P vibration. D-55

54 Figure 47. Aviation Vibration Analyzer (AVA) (3) Rotor system track and balance using the AVA (a) (b) (c) The AVA analyzes rotor system vibrations at the 1P frequencies of the main and tail rotors and recommends maintenance procedures to correct the vibrations. The AVA is a lightweight portable test set that is designed to operate with a minimum of in-flight operator interface. The AVA performs the following functions: 1) Measures, records, and processes vibration and blade position information. 2) Diagnoses information and supplies maintenance personnel with corrective actions for minimization of Main Rotor (M/R) and Tail Rotor (T/R) 1P vibrations and M/R track spread. 3) Maintains a database of measurements and diagnostic outputs for the complete track and balance exercise. 4) Can also be used to acquire frequency measurements for general vibration trouble-shooting. D-56

55 PFN 011-XXXX-4.0 Figure 48. AVA Basic Kit (d) AVA system components 1) Component case marked AVA BASIC KIT contains the following components: a) Data Acquisition Unit (DAU) b) Control And Display Unit (CADU) c) Universal Tracking Device (UTD) d) Credit Card Memory (CCM) device e) Interconnection cables f) Accelerometers and mounting brackets g) Optical rpm sensor and bracket 2) Component case marked AH-64 ADAPTER KIT with the following components: a) Main AH-64D-to-AVA interface cable b) AH-64D UTD mounting bracket (e) Equipment requirements for performing AH-64D track and balance of main and tail rotors. 1) Rotor track and balance accessories kit D-57

56 2) Aircraft mechanic tool kit 3) AVA track and balance system items a) DAU in canvas carrying case b) CADU c) 10 ft CADU to DAU cable d) UTD e) 25 ft UTD cable f) AH-64D UTD bracket g) 6 ft AH-64 to DAU cable h) AH-64D aircraft setup file (installed in CADU) i) Accelerometer cables (1 each 50 ft and 2 each 25 ft) j) Accelerometers (3) k) Optical rpm sensor l) Optical rpm sensor mounting bracket m) Main and tail rotor balance weights (as required) n) Lockwire (0.032 inch diameter) Figure 49. Data Acquisition Unit (DAU) (4) AVA setup for main rotor D-58

57 PFN 011-XXXX-4.0 (a) DAU installation 1) Install the DAU in its canvas carrying case to the outboard side of the CPG s left armor plate, with the connectors facing up and the ON/OFF switch forward. 2) Secure the DAU with the canvas straps and D-rings. 3) Ensure the DAU is OFF. Figure 50. Blade Tracking Test Port 4) Connect the AH-64-to-DAU cable ( ) to the blade tracking test port located below and aft of the CPG s right Sensor Surveying Unit (SSU). a) Ensure the FCR Select switch is in the TRACK position. b) Route the AH-64-to-DAU cable behind the CPG seat and connect it to the DAU connectors marked MULTI CH, TACHO 1, and 28 Vdc. c) Connect the CADU-to-DAU cable ( ) from the CADU to the DAU connector marked CADU. d) Ensure the TRACKER MODE switch on the DAU is in the DAY position. D-59

58 Figure 51. Tracker Installation (b) (c) Tracker installation 1) Secure the UTD and mount bracket to the LEFT side EFAB, with the arrow pointing in the direction of main rotor rotation. 2) Remove panel 5L90. 3) Connect the tracker cable to the DAU connector labeled TRACKER. 4) Route the opposite tracker cable connector through the opening at 5L90. 5) Connect the tracker cable to the UTD. 6) Pull the cable slack into the CPG compartment and store behind the CPG seat. 7) Reinstall panel 5L90 with the tracker cable routed through the notch (notch opening up). CADU initialization 1) Press QUIT on the CADU until all selections are undefined. 2) Use the cursor keys to highlight Aircraft Type, and then press DO. 3) Use the cursor keys to highlight AH-64D2, and then press DO. 4) Tail number is highlighted. Press DO. 5) Use the cursor keys to highlight a tail number or enter a new tail number, then press DO. 6) Flight Plan is highlighted. Press DO. D-60

59 PFN 011-XXXX-4.0 (d) 7) Use the cursor keys to highlight the desired flight plan, and then press DO. Aircraft accelerometer bypass installation NOTE: It is strongly recommended that this bypass procedure be used to minimize the chances of error from a faulty Signal Processor Unit (SPU) and/or bad on-board accelerometers. 1) Install one of the Wilcoxon 991D accelerometers ( ) from the AVA kit to the same longitudinal airframe member to which the lateral on-board accelerometer is mounted in the pilot station above and just aft of the pilot s head. a) Mount the accelerometer in the lateral direction to one of the existing holes with the connector in the same direction as the on-board accelerometer (connector to the pilot s right). b) Connect one of the AVA accelerometer cables ( or ) to the accelerometer. c) Route the cable down the left hand side of the pilot compartment, securing it with tie wraps to prevent interference with the pilot s controls, and through the pass-through to the CPG compartment. d) Connect the cable to the DAU connector labeled ACC1. 2) Install a second Wilcoxon 991D accelerometer ( ) from the AVA kit in the CPG station to the same vertical member to which the on-board vertical accelerometer is attached. a) Lift out the CPG communication control panel. b) Mount an accelerometer to the L-bracket ( ). c) Connect one of the AVA accelerometer cables ( or ) to the accelerometer. d) Mount the accelerometer and L-bracket ( ) to one of the nutplate-backed holes on the aft outboard side of the vertical member adjacent to the on-board vertical accelerometer, with the connector and cable pointing down. e) Route the accelerometer cable up through the instrument panel, along the right hand side of the CPG station, and behind the CPG seat to the DAU. f) Connect the cable to the DAU connector labeled ACC2. g) Reinstall the CPG communication control panel. NOTE: It is very important that the lateral accelerometer in the pilot station be connected to ACC1 and the vertical accelerometer in the CPG station be connected to ACC2. Swapping these two connections will prevent track and balance of the aircraft. NOTE: It is very important that the lateral accelerometer in the pilot station be mounted such that its connector is to the right and that the vertical accelerometer in the CPG station has its connector pointing down. The wrong accelerometer orientation will prevent track and balance of the aircraft. D-61

60 NOTE: To avoid tracker errors, touch up any shiny spots (i.e. leading edge erosion) on the underside of each blade, from the start of the swept tip to pocket 10, with flat black spray paint. Figure 52. Taping of Blades (e) Night-time operations 1) Place a 5-foot strip of reflective tape on the underside trailing edge (trim tab) of each main rotor blade. 2) Ensure that the tape is as smooth and straight as possible. 3) Place the TRACKER MODE switch on the DAU to the NIGHT position. (5) Track and balance main rotor (a) Track and balance of the main rotor blades should be performed when any of the following occurs: 1) One or more blades have been changed 2) One or more tip caps have been changed 3) One or more pitch control rods or rod end bearings have been changed 4) The main rotor hub has been replaced or disassembled 5) 1P vibration levels are objectionable NOTE: In order to ensure the main rotor 1P vibration states are as good as they can be for as long as they can be, the aircraft should be tracked and balanced in the external stores configuration in which it is intended to be flown following track and balance maintenance. D-62

61 PFN 011-XXXX-4.0 An aircraft with good 1P vibration levels in one wing stores configuration may have vibrations in excess of specification levels in another configuration. (b) Main rotor ground track and balance accomplishes the following: 1) Establishes a starting point for main rotor vibration analysis 2) Adjusts pitch change links to achieve main rotor blade track within 1/4 inch (high blade to low blade) 3) Makes balance corrections by adjusting weight stack-ups at main rotor blade root attaching point 4) Adds or subtracts main rotor blade weight to achieve a balance of 0.20 IPS or less NOTE: Ground track settings are likely to be affected by adjustments for in-flight vibration reduction. Adjustments to achieve a "satisfactory" ground track may not be required if troubleshooting a previously acceptable rotor system. 5) Ground track and balance limits a) The AVA will show the following limits for ground track and lateral vibration: 1 Track: 0.25 inches high blade to low blade 2 Lateral Vibration: 0.20 IPS NOTE: Consider these goals rather than hard limits. Extra time spent to get measurements below these values is not an efficient use of time, as both ground balance and track will be disturbed to some extent in order to bring in forward flight vertical vibration and hover lateral vibration. 6) Perform ground track and balance measurement as follows: NOTE: Ground measurements are to be taken with the collective stick in full down position. D-63

62 Figure 53. CADU-1. (c) CAUD-1 1) Use cursor keys to select GROUND from the Flight Plan menu. 2) Enter the Measure mode by pressing F1. 3) Limits may be toggled LIMITS OFF to LIMITS ON by pressing F4. NOTE: LIMITS ON (F4) will present a list of any measurements that exceed ground limits once the measurement is complete. a) Verify Fpg101 is highlighted. b) Press DO when the aircraft is stable at flat pitch and 101%. c) Re-verify that the aircraft is at the required test state and press DO again. d) Verify the tachometer frequency is 4.86 ±0.2Hz for 101% N R. e) The AVA will acquire track and vibration data. NOTE: If the tracker is facing into the sun, a tracker error may result. If an error results, reposition the aircraft so the tracker is pointing away from the sun, and retake the measurement. f) After the measurement is complete, review the Limit Screen and press QUIT. D-64

63 PFN 011-XXXX-4.0 g) Highlight FINISH and press DO. h) Highlight Main Menu (to display and review the ground data or to take another measurement), or Diagnostics (to calculate corrections). NOTE: It is recommended to review the acquired data (by first going to the Main Menu) before executing diagnostics in order to better understand and manipulate the diagnostics to obtain the best solution. Displays provided in the diagnostics branch are limited. i) Review the measured data (Refer to TM &P). j) Perform GROUND diagnostics (Refer to TM &P). NOTE: If measurements are within or reasonably close to limits, it is recommended that no adjustments be performed based on ground measurements only. Additional fine-tuning at this time is not an efficient use of time. 4) Adjust the main rotor blades for ground track by using dual engine torque. a) If dual engine torque is less than 15%, use Edit Adjustables to turn off the highest blade and compute new corrections, which will adjust the other three blades up to the highest blade. b) If dual engine torque is greater than 20%, use Edit Adjustables to turn off the pitch link adjustment for the lowest blade and compute new corrections, which will adjust three blades down to the lowest blade. c) For torque between 15% and 20%, use the AVA default solution. NOTE: Aircraft GROUND track and balance requirements must be completed prior to performing in-flight track and balance. (d) Main rotor flight track and balance 1) Utilizes a series of flight conditions as test points to determine vibration levels and support calculation of corrections. 2) Weights, pitch links, and blade tabs may all be utilized in the vibration and track solution. 3) The AVA will show the following limits for flight track and vibration: a) Lateral vibration on ground: 0.20 IPS b) Lateral vibration in hover: 0.15 IPS c) Vertical vibration in forward flight: 0.3 IPS d) Ground and hover track: 1 inch high blade to low blade e) Forward flight track: 1.5 inches high blade to low blade NOTE: Forward flight conditions are to be flown at true airspeeds. 4) Perform FLIGHT Track and Balance Measurement a) Use cursor keys to select FLIGHT from the Flight Plan menu. D-65

64 b) Enter the Measure mode by pressing F1. c) Limits may be toggled LIMITS OFF to LIMITS ON by pressing F4. d) Highlight the desired flight condition (Fpg101, Hover, 60, 80, 100, 120, and 140 KTAS). e) Press DO when the aircraft is stable at the required test state. f) Re-verify that the aircraft is at the required test state and press DO again. g) Verify the tachometer frequency is 4.86 ±0.2Hz. h) The AVA will acquire track and vibration data. NOTE: If the tracker is pointed towards the sun, the AVA may give a tracker error and may indicate partial next to the measurement condition. Re-orient the aircraft away from the sun, and repeat the measurement for that condition. Figure 54. (e) CADU-2 1) After the measurement is complete, review the Limit Screen. a) This information can be useful in determining whether or not to proceed to the next higher flight condition. D-66

65 PFN 011-XXXX-4.0 NOTE: Do not proceed to next higher flight condition if track spread exceeds 3 inches, vertical 1P vibration is excessive (1.2 IPS or more), or hover or ground lateral exceeds 0.4 IPS. AVA diagnostics will still give corrections for those flight conditions measured. b) Press QUIT to exit out of the limits screen and return to the measurement screen. c) The next test state will be highlighted. d) Press DO twice to start measurement and repeat until all flight conditions have been obtained, or until vibration and/or track precludes advancing to the next higher speed. NOTE: If any test state has a failed or partial message next to the prompt, the AVA did not get a complete set of data for this test state. Arrow back to the test state and repeat the measurement until all test states have done next to them. NOTE: Autorotation rpm verification should be done as soon as the aircraft is capable of a forward airspeed of 80 to 100 Knots Indicated Airspeed (KIAS). Large autorotation adjustments may disturb 1P track and balance. Figure 55. (f) CADU-3 1) If data has been acquired for all seven conditions of the FLIGHT plan, the measurement screen will automatically exit: D-67

66 a) Highlight Finish and press DO to exit out of Measurement mode, or b) Highlight Continue and press DO to return to the measurement screen (to display measurements from an individual flight condition, or to repeat a measurement), or 1 Highlight Main Menu (to display and review the measured data), or Diagnostics (to calculate corrections). 2) If data has not been acquired for all seven conditions, but vibration or track precludes going to the next higher airspeed or no further data is to be taken, press QUIT to exit the measurement screen, and select Save and Exit to save measured data. 3) Review the measured data (Refer to TM &P). 4) Perform FLIGHT Diagnostics (Refer to TM &P). D-68

67 PFN 011-XXXX-4.0 CHECK ON LEARNING 1. The main rotor adjustments available for control of 1P vibration are: ANSWER: 2. During ground track and balance (101% N R and collective full down) pitch link moves, to control track spread, will also affect: ANSWER: 3. During forward flight track and balance, pitch links are adjusted primarily to reduce with a secondary objective of reducing? ANSWER: 4. What are main rotor blade tab adjustments primarily used for? ANSWER: 5. When should the autorotation rpm verification be done? ANSWER: D-69

68 F. Enabling Learning Objective 6 After this lesson you will: ACTION: Identify the characteristics of the tail rotor system balance procedures. CONDITIONS: Given a written test without the use of student notes or references. STANDARD: 1. Learning Step/Activity 1 In accordance with TM and TM APACHE/LONGBOW (IETM). Figure 56. Polar Chart (Tail Rotor) a. Tail rotor balance procedures (1) Tail rotor adjustments (a) (b) (c) In-plane vibration in the vertical direction at the 1 per rev frequency of the tail rotor (23.6 Hz) as measured at the top of the tail rotor gearbox is minimized during tail rotor dynamic ground balance by adjusting tail rotor tip weights. One 11-gram weight (-7 part number) added to outboard blade No.1, for example, will change the vertical gearbox 1P vibration by approximately 0.6 IPS in the direction of about 160 on the polar chart. One 11-gram weight added to inboard blade No.1 would change 1P vibration by approximately 0.4 IPS in the direction of about 120 on the polar chart. D-70

69 PFN 011-XXXX-4.0 Figure 57. Balance Weights Tail Rotor Blade NOTE: The manufacturer, to achieve static span-wise balance originally installs tail rotor tip weights. These same weights are also manipulated during tail rotor dynamic ground balance. Typically, there should be around 120 grams (±20 grams) in each (forward and aft) tip pocket in order to maintain the original span-wise balance characteristic. CAUTION Never remove all the weights from the tail rotor blade tips. This can result in vibration large enough to cause significant structural damage to the aircraft. (2) Tail rotor balance weights (a) Three different size weights are used for balancing the tail rotor. 1) gram (0.012 Cres) 2) gram (0.032 Cres) 3) gram (0.060 Cres tungsten) 4) Four bolts hold the weights in two separate mounting points requiring two bolts for each mount point. 5) One-half of required weight correction should be made at each mount point. 6) Tail rotor pitch change links are nonadjustable; tail rotor track cannot be changed. D-71

70 b. AVA setup for tail rotor (1) DAU installation (a) (b) (c) (d) (e) (f) Install the DAU in its canvas carrying case to the outboard side of the CPG s left armor plate, with the connectors facing up and the ON/OFF switch forward. Ensure the DAU is OFF. Connect the AH-64-to-DAU cable ( ) to the Blade Tracking Test Port located below and aft of the CPG s right SSU. Ensure the FCR Select switch is in the TRACK position. Route the AH-64-to-DAU cable under the CPG seat and connect it to the DAU connectors marked MULTI CH, TACHO 1, and 28 Vdc. Connect the CADU-to-DAU cable ( ) from the CADU to the DAU connector marked CADU. Figure 58. Install Optical rpm Sensor c. Install optical rpm sensor (1) Mount the optical rpm sensor ( ) to the bracket. (2) Mount the optical rpm sensor mounting bracket ( ) on the tail with the aft panel screw in the aft-most of the four bracket holes. (3) Route the optical rpm sensor cable down the tail and forward through panel 5L90 to the DAU. (4) Connect the optical rpm sensor cable to the DAU connector marked TACHO2. D-72

71 PFN 011-XXXX-4.0 NOTE: Ensure that any tape remaining from previous balance operations is serviceable or completely removed and replaced to ensure an accurate tachometer signal to the DAU. NOTE: The blade with the reflective tape is referred to in the AVA diagnostics as the #1 outboard blade. The other blades are addressed as #1 inboard, and #2 outboard and inboard, following the direction of rotation. (5) Place a single 5-inch strip of reflective tape on either outboard blade, on the inboard side of the blade root end. The tape should be placed with the span of the blade, with approximately half on the tubular root section and half on the blade proper. Figure 59. Install Tail Rotor Accelerometer d. Install tail rotor accelerometer (1) Remove the top-most nut on the tail rotor gearbox. (2) Mount the accelerometer mounting bracket ( ) to the gearbox so that the accelerometer will be vertical with the cable connector up. (3) Install accelerometer ( ) on the accelerometer mounting bracket. (4) Connect accelerometer cable ( ) to the accelerometer and route the cable down the tail and with the optical rpm sensor cable forward through panel 5L90 to the DAU. (5) Connect the accelerometer cable to the DAU connector marked ACC 4. D-73

72 Figure 60. Tail Rotor Accelerometer. e. Tail Rotor Accelerometer (1) Mount the accelerometer mounting bracket ( ) to the gearbox so that the accelerometer will be vertical with the cable connector up. (2) Install accelerometer ( ) on the accelerometer mounting bracket. (3) Connect accelerometer cable ( ) to the accelerometer and route the cable down the tail and with the optical rpm sensor cable forward through panel 5L90 to the DAU. (4) Connect the accelerometer cable to the DAU connector marked ACC 4. f. Tail rotor balance procedure (1) Operate helicopter at 101% N R, flat pitch. (2) Turn on DAU. (3) Turn on CADU. (4) Press QUIT on the CADU until all selections are undefined. (5) Select AH64D2, from the Aircraft Type menu. (6) Enter the Tail Number menu and select a previous tail number or enter a new one (up to seven digits). (7) Enter the Flight Plan menu and select tail. D-74

73 PFN 011-XXXX-4.0 (8) Select tail70 and take the measurement at 70% N R if excessive T/R 1P vibration precludes running up to 101%. Figure 61. T/R Measure Mode (9) Enter the MEASURE mode and verify fpgtl as the selection. D-75

74 Figure 62. Measuring Mode (10) Press DO on the CADU when the pilot is stable at 101% N R, flat pitch. Reverify pilots at the required test state and press DO again. The AVA will acquire vibration data. The screen will display **MEASURING** while the unit is acquiring data. When vibration data is acquired, the display will return to a selection display. D-76

75 PFN 011-XXXX-4.0 Figure 63. T/R Correction Screen (11) After the last measurement is completed, press DO on "finish", press DO on "diagnostics". If the measurements are within specified limits, press QUIT to main menu and select next flight plan. If measured values exceed specifications, press DO, to enter DIAGS mode. (12) If the results are less than 0.15 IPS, no corrections are required. However, the AVA may offer corrections to smooth the rotor further, at the operator s discretion. For a tail rotor in a good maintenance state, tail rotor balance below 0.1 IPS should be easily achievable and is encouraged. (13) If results exceed 0.15 IPS, enter the DIAGS mode and perform the corrections recommended by the correction screen. Be sure to make correction shown on both screens (inboard and outboard blades). (14) Repeat measurement to verify corrections and perform additional corrections as necessary. (15) Remove track and balance equipment from the tail rotor. D-77

76 CHECK ON LEARNING 1. Where is vibration measured during tail rotor dynamic ground balance? ANSWER: 2. Can tail rotor track be adjusted? ANSWER: 3. When should all the weights be removed from the tail rotor blade tips? ANSWER: D-78

77 PFN 011-XXXX-4.0 G. Enabling Learning Objective 7 After this lesson you will: ACTION: Identify the characteristics of the rotor system special in-flight tests. CONDITIONS: Given a written test without the use of student notes or references. STANDARD: 1. Learning Step/Activity 1 In accordance with TM and TM APACHE/LONGBOW (IETM). Figure 64. Autorotation RPM a. Special tests (1) Main rotor autorotation rpm check and adjustment (a) (b) (c) The purpose of the autorotation rpm check is to ensure that main rotor autorotational rpm is correct for aircraft and environmental conditions. Perform limited test flight, including autorotational rpm check per TM MTF. Check autorotation rpm 1) Perform autorotation at 90 knots true airspeed (TM MTF). 2) Record the following information: D-79

78 a) Pressure altitude b) Outside air temperature (stabilize for 1 minute) c) Rotor rpm (N R ) d) Fuel quantity remaining 3) Determine minimum main rotor rpm from Autorotation RPM Chart. (TM MTF, Figure 5-5) a) The gross weight selected for the test in step (a) should be such as to produce an rpm within the normal operation limits of the Autorotation RPM Chart. b) The autorotation rpm established in step (a) must be equal to or up to 3% greater than the main rotor rpm determined from Autorotation RPM Chart. c) If the actual rpm is lower than the limits of the Autorotation RPM Chart, or more than 3% above the limits, the rotor blade pitch must be adjusted. Figure 65. Main Rotor Autorotation RPM Adjustment (d) Autorotation rpm adjustment 1) To increase rpm, the blade pitch must be reduced by shortening the pitch links. 2) To decrease rpm, the blade pitch must be increased by lengthening the pitch links. D-80

79 PFN 011-XXXX-4.0 3) All four pitch links must be adjusted the same amount. 4) Adjusting pitch links 1 flat equates to approximately 1% change in rpm. 5) Repeat the steps above until autorotation rpm is within specifications of Autorotation RPM Chart. 6) Repeat in-flight track from hover to V H and verify that main rotor blades are within 1/2 inch of track. If not, repeat main rotor forward flight track and balance procedure. 7) Remove track and balance accessories. (2) Maneuvering flight check (TM MTF) NOTE: If rotor vibrations are noted during any of the checks listed below, then rotor track and balance should be accomplished to correct the problem. (a) Cruise check Note vibration levels and control position at 120 KTAS straight and level flight. (b) Descent check Note any rotor instability or unusual control position at 20% torque. (c) (d) Climb check Note any rotor instability or unusual control position at maximum continuous torque. Turning flight check (3) V H level flight test 1) Used to detect worn blade dampers 2) Note any rotor instability or unusual control position, while smoothly banking to 60 at 120 KTAS. 3) A value of 0.76 IPS should be considered the maximum acceptable level during turning flight. (a) (b) (c) V H is defined as the maximum level flight speed attainable. V H will vary with available power, aircraft weight, altitude and temperature. Note any abnormal vibrations or control response. D-81

80 CHECK ON LEARNING 1. What is the purpose of the autorotation rpm check? ANSWER: 2. When must you make a main rotor autorotation rpm adjustment? ANSWER: 3. What is the Turning Flight Check used for? ANSWER: D-82

81 PFN 011-XXXX-4.0 H. Enabling Learning Objective 8 After this lesson you will: ACTION: Identify the characteristics of the rotor system special in-flight tests. CONDITIONS: Given a written test without the use of student notes or references. STANDARD: 1. Learning Step/Activity 1 In accordance with TM and TM APACHE/LONGBOW (IETM). Figure 66. Modernized Signal Processing Unit (MSPU) a. Modernized Signal Processing Unit (MSPU) (1) We will discuss the system overview, components, operation, Personal Computer- Ground Based System operation, downloading, determining health, rotor smoothing, and drivetrain. (2) The Modernized Signal Processing Unit (MSPU) is a permanently installed rotor smoothing and machinery health monitoring system. The system is part of the Apache PM s Condition Based Maintenance Program (CBM). D-83

82 (3) The system provides recommendations for corrective actions to maintain vibration levels at a minimum. MSPU will advise whenever a limit has been exceeded and recommend a maintenance action. Figure 67. The CBN Process. (4) The CBN Process (a) MSPU is composed of three primary components. 1) Onboard System: a) MSPU Line Replaceable Unit (LRU) b) Accelerometers; Tachometers; Tracker Camera, USB Quick Access Recorder (QAR) 2) Personal Computer-Ground Based Station (PC-GBS). PC-GBS runs on a PC-based Windows platform, which downloads processed data from the MSPU and interprets the data to provide recommended corrective actions. 3) Web-based infrastructure tools. a) These tools include an internet utility designed to collect data from PC-GBS software for fleet trending and engineering analyses. D-84

83 PFN 011-XXXX-4.0 Figure 68. AWR Action/Benefit (5) AWR Action/Benefit includes: (a) (b) (c) (d) (e) (f) Eliminates AVA installation for Main Rotor smoothing (with the exception of the camera). Eliminates AVA installation for Tail Rotor balance. Eliminates 50 hours bearing inspection for the Main Rotor Swashplate. Eliminates vibration checks at installation and Phase and also increases the APU mount special inspection from 250 to 500 Hours. Eliminates AVA installation for APU Clutch 50 hour check. Increase TBO from 2500 to 2750 w / Monitoring of the Forward and Aft Hanger Breaings. D-85

84 Figure 69. MSPU Kits. (6) MSPU Kits (a) (b) MSPU A and B kit ( FA) 1 unit issue per each aircraft. MSPU Ground kit ( FA) 4 unit issue per Battalion. NOTE: SPU LRU is removed but SPU cables and connectors are stowed and available for re-install of SPU if needed. D-86

85 PFN 011-XXXX-4.0 Figure 70. MSPU Description. b. MSPU Description (1) The AH64D Apache MSPU contains: (a) (b) (c) 18 accelerometers 4 tachometers The MSPU Line Replaceable Unit (LRU) is located behind the co-pilot / gunner seat 1) USB Quick Access Recorder (QAR) is located in the left hand EFAB 2) Ground Kit a) Computer b) Tracker 1 Temporarily mounted when tracking of the rotor system is required c) Tracker cable (Only use the supplied tracker cable) d) Download cables e) Weight scale f) Reflective tape D-87

86 Figure 71. Sensors (2) Sensors location (a) ACC1, Cockpit CPG Vertical (b) ACC2, Cockpit Pilot Lateral (c) ACC3, Nose Vertical (d) ACC4, Tail Gearbox Vertical (e) ACC5, Tail Gearbox Lateral (f) ACC6, Intermediate Gearbox (g) ACC7, Engine No. 1 (h) ACC8, Engine No. 2 (i) ACC9, Nose Gearbox No. 1 (j) ACC10, Nose Gearbox No. 2 (k) ACC11, Forward Hanger Bearing (l) ACC12, Aft Hanger Bearing (m) ACC13, Main Transmission Left Input D-88

87 PFN 011-XXXX-4.0 (n) (o) (p) (q) (r) (s) (t) (u) (v) (w) (x) ACC14, Main Transmission Right Input ACC15, Main Transmission Accessories ACC16, Tail Rotor Swashplate ACC17, Main Rotor Swashplate ACC18, Auxiliary Power Unit Tach1, Main Rotor Magnetic Pickup Tach2, Tail Rotor Tachometer Tach3, NR Tachometer Tach4, Generator Tachometer Bus A, 1553 Data Bus #2 Channel A Bus B, 1553 Data Bus #2 Channel B Figure 72. Accelerometers. (3) Accelerometers (a) The system has 18 Accelerometers covering all the rotating drive train components D-89

88 Figure 73. Tachometers (4) Tachometers (a) The system has 4 Tachometers 1) Pilot compartment 2) Main Rotor 3) Main Transmission area 4) Tail Rotor D-90

89 PFN 011-XXXX-4.0 Figure 74. UTD Connector and Data Port location. (5) UTD Connector and Data Port location (a) (b) Data Port and Tracker Day/Night Switch is located on the Copilot Gunner's Left Side Wall. UTD Tracker Interface panel is located at panel 5L90 & connects with tracker, bracket, & cable. D-91

90 Figure 75. Computer Interface to MSPU. (6) Computer Interface to MSPU (a) Computer Interface to MSPU is located in the CPG compartment. D-92

91 PFN 011-XXXX-4.0 CHECK ON LEARNING 1. Is the number of Accelerometers covering all of the rotating drive train components? ANSWER: 2. What is the number of system Tachometers? ANSWER: 3. Where is the Data Port and Tracker Day/Night Switch located? ANSWER: D-93

92 2. Learning Step/Activity 2 Figure 76. MSPU Operation a. MSPU Operation (1) There are three ways the MSPU collects data: (a) Monitor: 1) (SPU) Automatically collects data from critical IGB, TGB, & APU sensors every 45 seconds whenever power is applied to the MSPU and the MSPU detects aircraft NR above 90%. 2) TAC 3 is critical for the monitor mode operation. D-94

93 PFN 011-XXXX-4.0 Figure 77. Mode Collection Matrix. b. Mode Collection Matrix (a) Automatic: 1) The system automatically collects data in a particular ground or flight state as detected by MSPU acquiring 1553 data. 2) These are limited to the following modes & states. a) FLIGHT (Rotor Smoothing) FPG101, Hover, 60, 80, 100, 120,140 b) TAIL (Balance) FPG101 c) SURVEY (Drivetrain Health) FPG101, 120KTA (b) Manual: 1) (AVA) Collects data in a particular ground or flight mode as selected by the operator. 2) Data is collected using a computer running PC-GBS in-flight. This should be restricted to maintenance test flights only. D-95

94 Figure 78. PBIT Indication checks in PC-GBS c. PBIT Indication checks in PC-GBS (1) PBIT MSPU and accelerometer checks are available through the PC-GBS under the MSPU component tree. D-96

95 PFN 011-XXXX-4.0 Figure 79. Ensuring all systems are operational. d. Ensuring all systems are operational (1) At the end of a flight where a computer was not used to take data check for the following. (a) (b) Highlight A/C tail number then click on Selection Click on Select Historical Data (2) All these modes should be displayed for the date of the flight: (a) (b) (c) (d) (e) (f) BIT MSPU LRU booted BUS 1553 data is present Monitor TAC 3 is working Flight TAC 1 is working Tail TAC 2 is working Survey D-97

96 Figure 80. Inoperative TAC-3 Signal. (3) Inoperative TAC-3 Signal (a) (b) (c) At the end of a flight where a computer was not used to take data check for the following. 1) Highlight A/C tail number then click on Selection. 2) Click on Select Historical Data. Notice that for this particular flight that there was no Monitor Mode. This would indicate that TAC 3 was not operational during the flight. D-98

97 PFN 011-XXXX-4.0 Figure 81. TAC-3 (4) TAC-3 (a) (b) (c) The jumper wire is currently not part of the standard transmission wire harness and is added during the MWO installation. If the transmission is replaced, a jumper wire must be added to the new transmission wire harness. This jumper wire allows MSPU TAC-3 to read NR and triggers the "Monitor Mode" which provides the in-flight monitoring of the TR Gearbox, IGB, and APU D/S. (A wire diagram is provided in the PC-GBS). 1) If this jumper wire is not installed the "VIB GRBX" or "Vibration Gearbox" messages can not illuminate for the TR Gearbox, IGB, and APU Driveshaft: AMAM# H AMAM-01. 2) The MSPU system will pass PBIT without this wire! D-99

98 Figure 82. Tracker & Data Port. (5) Tracker & Data Port (a) (b) (c) Install the Tracker using the supplied cable. 1) Only use the supplied Tracker Cable. Connect the computer to the aircraft Data Port. Manually collect GROUND data without errors. WARNING If a MSPU LRU is moved to another aircraft you must change the tail number in the LRU. If the tail number is not set correctly. Data trending will be destroyed. This will affect the ability to troubleshoot. D-100

99 PFN 011-XXXX-4.0 Figure 83. Vib GRBX Light Operation (6) Vib GRBX Light Operation (a) Power on process 1) Not Pilot interactive. 2) Power up is automatic any time MSPU receives 115V AC power from Aircraft. D-101

100 Figure 84. PBIT Vib GRBX Msg Triggers. (7) PBIT Vib GRBX Msg Triggers (a) FAILED MSPU PBIT: 1) If the MSPU LRU or a critical accelerometer fails PBIT the VIB GBX msg remains on constant. 2) MSPU LRU and all accelerometers are evaluated in PBIT. 3) If the MSPU LRU or a critical accelerometer fails after a successful PBIT the VIB GBX msg will not illuminate until next PBIT. D-102

101 PFN 011-XXXX-4.0 Figure 85. (8) Vib GRBX Msg Operation Vib GRBX Msg Operation (a) Conditions that prevent the VIB light from ever coming on. 1) Any hardware condition that prevents the onboard system from booting will also prevent the VIB light from lighting. a) Circuit breaker open. b) MSPU internal failure. c) P1 not connected. D-103

102 Figure 86. Vib GRBX Msg Triggers (9) Vib GRBX Msg Triggers (a) MSPU Condition Indicators that light the GEARBOX VIBRATION Msg: 1) These are the items that are monitoring the IGB, TGB, APU driveshaft for both Monitor and Survey modes. 2) TAC 3 is critical for this operation. D-104

103 PFN 011-XXXX-4.0 Figure 87. Quality Assurance (10) Quality Assurance (a) MWO , 19 Aug 07 1) Weight and Balance Data Changes Made. 2) Recording and reporting of the Modification Records and report forms. D-105

104 Figure 88. MSPU Operational Check. (11) MSPU Operational Check (a) (b) (c) (d) (e) (f) (g) (h) (i) The Maintenance Operational Check (MOC) is designed to check the proper operation of the installed system. The output signal of each sensor, the integrity of the installed cable assemblies, and the electrical connection of each sensor cable to the Modern Signal Processing Unit (MSPU) will be checked. MSPU LRU will be loaded with the tail number of the aircraft the system is being installed on. Correct electrical wiring is critical to the operation of the system. Improperly connected wires will invalidate the diagnostic functions of the system. Ensure that interrupter for the TAC 2 (tail rotor) will not hit prior to starting the aircraft. Check MSPU LRU for proper 28vdc polarity. 1) Use multi-meter Boot MSPU. Check for passage of PBIT & Accelerometer bit. Check for proper accelerometer wiring. 1) Excite each accel with vib etcher while reading output via the manual mode Test Accels program (j) Check D-106

105 PFN 011-XXXX-4.0 (k) Take data with the Manual Mode. 1) Check data port functionality 2) Check tachometer functionality 3) Check tracker functionality (l) USB QAR functionality. NOTE: Refer to the MWO for details. D-107

106 CHECK ON LEARNING 1. Which TAC allows the jumper wire to read the NR and triggers the "Monitor Mode"? ANSWER: 2. The system automatically collects data in a particular ground or flight state as detected by MSPU acquiring 1553 data. These are limited to what three modes & states? ANSWER: D-108

107 PFN 011-XXXX Learning Step/Activity 3 Figure 89. MTF Operation a. MTF Operation (1) These are the Setup Configuration Step that we will follow. (a) (b) (c) GBS----Fleet Status Summery MODE Selection Measurement Control Panel for flight mode D-109

108 Figure 90. MSPU Operational Check. b. MSPU Operational Check (1) MOC common failures & remedies: (a) (b) (c) Sensor connector disconnected at junction 1) Connect cannon plug Tail pylon disconnect incorrectly wired 1) Re-pin connector TAC 2 (Tail rotor) not properly adjusted 1) Adjust IAW MWO procedures (d) Vib GRBX Msg flashes on / off continuously 1) Ground wire not installed on VIBLED RTN wire c. PC-GBS Lesson Topics (1) Setting Aircraft Tail Number (2) Downloading Data from MSPU (3) Status Hierarchy (4) Determining the Health of the Aircraft (a) Rotor Smoothing Components (b) Mechanical Components (5) Component Information & Displays D-110

109 PFN 011-XXXX-4.0 Figure 91. Setting an Aircraft Tail Number. d. Setting an Aircraft Tail Number (1) Open PC-GBS program (a) Click on the Icon in the PC-GBS title bar. This will display a menu. Select the GBS Management menu item. (b) (c) (d) (e) (f) GBS management functions require a password. (iac.vmep) The GBS Management dialog will be displayed. Select the Configure VMU button. Follow the Setup Configuration Step: 1) Once the Configure VMU button is selected, the Time Check dialog will display. 2) Select the Next> button if the time is correct or correct the time if needed. 3) Select the correct cable type on the Check Cable Connection screen. 4) Click Next> to continue. If the upload to OBS files dialog is displayed, select the No button. This will appear again after you have completed the process. The OBS Management dialog will be displayed. D-111

110 (g) (h) (i) (j) Type in the full tail number (XX-XXXXX) of the aircraft. Click on the Apply button to send the tail number to the OBS. Click done to close the OBS Management screen. Close the OBS Management screen by clicking on the Close button. Figure 92. Data Retention. e. Data Retention (1) Internal memory of the MSPU LRU (a) (b) (c) (d) Data is stored to the internal memory of the MSPU LRU and is also mirrored in the USB Drive (QAR). Data will accumulate until the memory is full and then start overwriting oldest data first. When Data is downloaded the files are marked as downloaded. 1) Data will still remain in MSPU and QAR for a set number of days before being permanently erased. Data can be re-downloaded if lost until the data retention data is expired. D-112

111 PFN 011-XXXX-4.0 Figure 93. Quick Access Recorder (QAR). f. Quick Access Recorder (QAR) (1) The QAR installation (a) The QAR is installed inside left EFAB and may be removed and used to download data to the PC-GBS without power applied to the aircraft. D-113

112 NOTE: The QAR should be reinstalled back into the same aircraft. NOTE: Recommend QAR be marked with aircraft tail number Figure 94. QAR Assembly g. QAR Assembly (1) Downloading with the QAR: (a) (b) (c) (d) (e) (f) (g) Remove the Quick Access Recorder from its bracket assembly. Power up your ground station computer and open the PC-GBS software. Insert the QAR into the USB port. In a few seconds, PC-GBS will recognize the QAR and will ask if you would like to process it. Click Yes. The data will download and import into the software automatically. The PC-GBS software will notify you when it has completed the download. Remove the QAR and place back into the same aircraft. D-114

113 PFN 011-XXXX-4.0 Figure 95. Manual Data Download Procedures h. Manual Data Download Procedures (1) For direct download: (a) (b) (c) (d) Apply power to the MSPU. The MSPU will take approximately 2 minutes to PBIT completion. Once PBIT is complete, open the PC-GBS. Select the Download button on the PC-GBS main screen. D-115

114 Figure 96. Setup Configuration Steps. i. Setup Configuration Steps (1) Validate the Correct Date & Time. (a) (b) (c) Confirm the current date, time and zone. If this information is incorrect, select the Change button and correct the information before continuing. If correct, select the Next > button to continue. D-116

115 PFN 011-XXXX-4.0 Figure 97. Setup Configuration Steps (Continued). j. Setup Configuration Steps (Continued) (1) Connecting the Download Cable (a) (b) Connect the MSPU Data Port located on the Copilot Gunner's Left Side Wall to the PC-GBS laptop using the Ethernet download cable. Select Ethernet Cable for MSPU Select Next > to Continue. D-117

116 Figure 98. Selecting Data Download k. Selecting Data Download (1) Ensure the PC-GBS / MSPU connection is complete. (2) Select the DOWNLOAD FLIGHTS button. (a) (b) By default all new flights are downloaded Other download options are available D-118

117 PFN 011-XXXX-4.0 Figure 99. Importing Data l. Importing Data (1) After downloading is complete, disconnect the download cables from the MSPU. (2) The data will then be imported into the PC-GBS. D-119

118 Figure 100. Abnormal conditions detected. m. Abnormal conditions detected (1) On the Fleet Status Summary Page, select the aircraft tail number. (2) Scroll down to the discrepant component and select. (a) Discrepant components are identified by Icon. (b) Good components are identified by Icon. (3) On the Aircraft Status Summary Page, note the Main Transmission corrective action. (a) (b) (c) The main transmission has high vibration. Inspect the main Transmission. If further assistance is desired, Contact Aviation Engineering Directorate. D-120

119 PFN 011-XXXX-4.0 Figure 101. Legend Box. n. Legend Box (1) Exceeded: (a) (2) Caution: (a) (3) Above Goal: (a) (4) Good: (a) (5) No Data: Vibration level has reached or surpassed the exceedence parameter and maintenance action should be performed. Status of vibration has exceeded the caution parameter, maintenance action is at the discretion of maintenance personnel Status of vibration has exceeded the goal. The above goal is only associated with components that require balancing. Vibration levels are below a set parameter within tolerance, no corrective action required. (a) No data for this aircraft or component. D-121

120 Figure 102. Determining the Health of the Aircraft. o. Determining the Health of the Aircraft (1) After the download is compete, the Fleet Status Summary page will show condition of the downloaded aircraft and its individual components. (2) For Main or Tail Rotor components who s status is Green with (Above Goal) click on the component and it is recommended to make the corrective action adjustment to keep the aircraft as smooth as possible. (a) No action is required for solid GREEN. (3) Double click on any YELLOW or RED components to view the Aircraft Status Summary window for that component. (4) Inform your Platoon SGT, Company Maintenance Officer or Production Control of any YELLOW or RED components, and make appropriate entries in the Aircraft logbook. D-122

121 PFN 011-XXXX-4.0 Figure 103. Aircraft Status Summary for Individual Components p. Aircraft Status Summary for Individual Components (1) After an aircraft has been identified as having a fault, clicking on the identified component will open the aircraft summary page. (2) There are three types of faults: (a) (b) (c) Rotor smoothing Drivetrain Components MSPU PBIT failure (3) Corrective Action Block will show MSPU recommended actions / solutions if any are required. D-123

122 CHECK ON LEARNING NOTE: Conduct a check on learning and summarize the learning step/activity. Have students write their answers in the Student Handout 011-XXXX, page D-XX. Make on-the-spot corrections as necessary. 1. When Data is downloaded the files are marked as downloaded, data will remain in the and the for a set number of days before being permanently erased? ANSWER: 2. In the Legend Box, what are the five conditions? ANSWER: D-124

123 PFN 011-XXXX Learning Step/Activity 4 Figure 104. Rotor Track and Balance. a. Rotor Track and Balance (1) Details of rotor smoothing balance solutions. (a) Rotor Smoothing Solution (b) Vibration Values (c) Vibration Plot (Polar) (d) Track (If UTD was installed) (e) Trend (f) Saving Adjustment Information (2) Trending Mechanical Components (a) Against other aircraft in your fleet (b) Over time (3) Plotting vibration data (4) Trending Mechanical Components (a) Against other aircraft in your fleet D-125

124 (b) Over time (5) Plotting vibration data Figure 105. MTF/Rotor Adjustment Help. b. MTP/Rotor Adjustment Help (1) By clicking on the links in the Corrective Action box, specific help is available for the task. D-126

125 PFN 011-XXXX-4.0 Figure 106. Component Information and Displays. c. Component Information and Displays (1) Details of rotor smoothing balance solutions. (a) Rotor Smoothing Solution (b) Vibration Values (c) Track (If UTD was installed) (d) Trend (e) Saving Adjustment Information (2) Trending Mechanical Components (a) Against other aircraft in your fleet (b) Over time (3) Plotting vibration data (4) Trending Mechanical Components (a) Against other aircraft in your fleet (b) Over time (5) Plotting vibration data D-127

126 Figure 107. Components that have Balance Solutions. d. Components that have Balance Solutions (1) Corrective actions for faults that have balance or mechanical solutions are displayed in the bottom corrective action box. (2) To view the rotor smoothing vibration data or to calculate an alternate solution double click on the component fault. D-128

127 PFN 011-XXXX-4.0 Figure 108. Vibration Adjustment Page. e. Vibration Adjustment Page (1) By double clicking on the fault, a vibration value page will be displayed. (2) The Use check box can be unchecked to remove a test state from the calculated solution if desired. (3) The Quality % number indicates how consistent the collected data was for each state & sensor. 100% is the best quality data set. Retaking data or un-checking the use box is an option if the data has a low quality percentage number. D-129

128 Figure 109. Vibration Adjustment Screen. f. Vibration Adjustment Screen (1) Double clicking on the rotor smoothing tab will open the vibration adjustment screen. (2) Each main rotor blade is noted by number with a possible weight change, pitch change link, or trim tab adjustment. (3) Each box can be turned ON or OFF to change the solution given by PC-GBS. (4) Weight, trim and pitch links solutions can be modified by the operator and predicted results viewed before any adjustments are made to the aircraft. D-130

129 PFN 011-XXXX-4.0 Figure 110. Rotor Smoothing Solution Options. g. Rotor Smoothing Solution Options (1) Best Overall Solution: (a) (2) Limit solution to: (a) (3) Manual Solution: (a) Try to get all vibration values to zero (center of polar chart) with the least amount of moves. Select the number of moves to limit the solution to. Allows user to adjust solution if an alternate solution is desired. (4) Resolve to Vibration Limits: (a) (5) Algorithm (a) Try to get all values into limits with the least amount of moves. Always look at predicted polar plot to see if other than Best Overall Solution is the best move. Indicates to the User which algorithm was used to calculate the solution. D-131

130 Figure 111. Main Rotor Vibration Plot. h. Main Rotor Vibration Plot (1) Clicking on the Vibration Plot tab will open the Vibration Plot screen. (2) In this view the operator can see the predicted effect of the current rotor smoothing solution. (3) The desired effect using this polar plot graph is to move vibrations to the center and to bring vibrations to the lowest level. (4) If the default solution is changed, the Vibration plot and values should be reviewed to ensure that the vibration is being reduced to satisfactory levels. D-132

131 PFN 011-XXXX-4.0 Figure 112. Main Rotor Vibration Plot (Continued). i. Main Rotor Vibration Plot (Continued) (1) If all the in-flight verticals are closely grouped, this is GOOD! (a) (b) This gives the indication that this aircraft should be easily smoothed. If the plots are scattered across the polar chart, this can mean that the vibration source is a loose or worn component, or a faulty blade. D-133

132 Figure 113. Main Rotor Manual Adjustment. j. Main Rotor Manual Adjustment (1) 1st. PC-GBS solution gives POLAR PLOT. (a) By manually turning ON/OFF or ADDING /SUBTRACTING from the solution, you may view VMEP predictions before making adjustments to the aircraft. D-134

133 PFN 011-XXXX-4.0 Figure 114. Main Rotor Track Plot k. Main Rotor Track Plot (1) The Track tab will only be displayed if track data was collected. (a) (b) (c) (d) Measured track is shown on the top display. Predicted track from the current solution is shown on the bottom. Select the Show Table button to display actual values. Select the Plot Type drop down arrow to display other track data i.e. Lead/Lag data. D-135

134 Figure 115. Track Lead / Lag Display. l. Track Lead / Lag Display (1) The type of track data displayed can be changed to display Lead / Lag data. D-136

135 PFN 011-XXXX-4.0 Figure 116. Vibration Adjustment Trend m. Vibration Adjustment Trend (1) The Trend tab allows the user to select data to trend two or more flights vibration information to see the progress of the adjustments made to the aircraft. (2) This can aid the operator in identifying whether a vibration level is moving in the right direction and that the aircraft is responding normally. (3) Use the select data button to view available data to trend. D-137

136 Figure 117. Vibration Adjustment Trend. n. Vibration Adjustment Trend (1) Flights are selected for the trend by date and time. (2) Select States and Sensors. (3) Add appropriate states and sensors to plot. (4) Select OK to show plot in next window. D-138

137 PFN 011-XXXX-4.0 Figure 118. Vibration Adjustment Trend (Continued 2 of 2). o. Vibration Adjustment Trend (Continued 2 of 2) (1) A polar trend plot shows the trend that the adjustments have made. (2) This will aid the operator in seeing If the vibration levels are moving in the right direction. (3) In this case the 120K vibration moved in the right direction but did not reach the goal ring. D-139

138 Figure 119. Saving Adjustment Information p. Saving Adjustment Information (1) After viewing a rotor smoothing fault that has a status of Above Goal or greater, the PC-GBS software will prompt the user to save the moves made to the aircraft. (2) When leaving that fault the Finalize Adjustments Dialog box will be displayed. Figure 120. Finalize Adjustments. q. Finalize Adjustments (1) To save the adjustments called out in the Corrective Action section of the Aircraft Summary page, select the Save Adjustments button. D-140

139 PFN 011-XXXX-4.0 Figure 121. Save Adjustments. r. Save Adjustments (1) Insert the name of the person who made or will make the adjustments. (2) Select the: View Adjustments To Be Saved button to view adjustments. (3) When complete select Save Adjustments. D-141

140 Figure 122. New Corrective Action Page. s. New Corrective Action Page (1) The name that was entered in the save adjustment screen will now appear in the corrective action box. D-142

141 PFN 011-XXXX-4.0 Figure 123. Correct a Previously Saved Correction. t. Correct a Previously Saved Correction (1) If a correction is saved in error, it is easily corrected. (a) (b) Double click on the fault requiring correction to bring up the Vibration Adjustment window. Manipulate the Rotor Smoothing Solution page to the correct values to be saved NOTE: Make all adjustments YES or NO if the previously saved adjustment was not made at all. (c) (d) (e) Select the Save Current Solution button. Type the correctors name as above and press Save Adjustments to complete the action. The Corrective Action window will now indicate the new saved corrections D-143

142 CHECK ON LEARNING NOTE: Conduct a check on learning and summarize the learning step/activity. Have students write their answers in the Student Handout 011-XXXX, page D-XX. Make on-the-spot corrections as necessary. 1. In the Legend box, the Above goal icon is an indication of what? ANSWER: 2. What is the purpose of a polar plot? ANSWER: 3. A trend plot is used for what purpose? ANSWER: 4. Fleet status summary page has what information on it? ANSWER: D-144

143 PFN 011-XXXX Learning Step/Activity 5 Figure 124. Trending Mechanical Components. a. Trending Mechanical Components (1) Double clicking on the component fault will display the CI Summary plot. (2) Double click on the CI bar open the quad chart display. D-145

144 Figure 125. Reading the Quad Charts. b. Reading the Quad Charts (1) Trend Across Time (Upper Left) (a) (b) Shows the progression of a condition indicator (CI) over time. Can be used to determine how fast a fault is progressing. D-146

145 PFN 011-XXXX-4.0 Figure 126. Reading the Quad Charts (Continued 1 of 3). c. Reading the Quad Charts (Continued 1 of 3) (1) Trend Across Aircraft (Upper Right) (a) (b) Shows how a condition indicator compares to the other aircraft in your unit. Can be used to determine if a fault is much worse than all the other aircraft. D-147

146 Figure 127. Reading the Quad Charts (Continued 2 of 3). d. Reading the Quad Charts (Continued 2 of 3) (1) Condition Indicator Control (Lower Right) (a) (b) (c) Allows user to select what condition indicator is displayed in the quad chart displays. CI s are sorted by severity Hovering mouse over the condition indicator will show the value of the CI D-148

147 PFN 011-XXXX-4.0 Figure 128. Reading the Quad Charts (Continued 3 of 3). e. Reading the Quad Charts (Continued 3 of 3) (1) Data display (Lower Left) (a) (b) (c) Allows user to select what condition indicator is displayed in the quad chart displays. CI s are sorted by severity. Hovering mouse over the condition indicator will show the value of the CI. D-149

148 Figure 129. Spectral Plot. f. Spectral Plot (1) The sensor selection can be changed at the lower right corner of the window to view more components. (2) Placing the arrow over the peak of the plot and right clicking the mouse key will annotate detailed information about the point. D-150

149 PFN 011-XXXX-4.0 Figure 130. Accelerometer Noise (Ski Slope). g. Accelerometer Noise (Ski Slope) (1) On Accelerometer Check: (a) (b) (c) Torque Condition Wire splice (2) Accelerometer installation and / or wire problems may show up as a ski slope data display. D-151