B737 Performance Takeoff & Landing Last Rev: 02/06/2004
Takeoff Performance Takeoff Performance Basics Definitions: Runway Takeoff Distances Definitions: Takeoff Speeds JAR 25 Requirements Engine failure Optimisation improved climb Reduced takeoff
Takeoff Performance Basics What is the Gross Takeoff Flight Path? It is the vertical flight path that a new aircraft flown by test pilots under ideal conditions would achieve. It is adjusted for the Minimum Engine. It starts where the aircraft passes 35ft and ends at a minimum of 1500 ft What is the Net Takeoff Flight Path? This is the vertical flight path that could be expected in operation with used aircraft. It also starts at 35ft and ends at a minimum of 1500ft
Takeoff Performance Basics The Net Gradient would be calculated as follows: Gross Gradient p% x D Net Gradient Distance = D
Takeoff Distances RUNWAY - This is the ACN capable hard surface CLEARWAY - This is an area, under the control of the airport, 152 m (500 ft) minimum width, with upward slope not exceeding 1.25%. Any obstacles penetrating the 1.25% plane will limit the Clearway STOPWAY - A surface capable of supporting the aircraft in an RTO. Its width must be greater than or equal to that of the runway. It may not be used for landings
Takeoff Distances CLEARWAY RUNWAY STOPWAY TORA ASDA TODA MAX 1.25%
Takeoff Distances TORA- TakeOff Run Available. This is the physical runway limited by obstacle free requirements ASDA - Accelerate-Stop Distance Available. This is the distance available for accelerating to V1 and then stopping. It may include the physical runway and any stopway available TODA - TakeOff Distance Available. This is the distance available to achieve V2 at the appropriate screen height. It may include physical runway, stopway and clearway Note: Not more than ½ the Air Distance may be in the Clearway (Air Distance is distance from lift-off to 35 ft) The Takeoff Run is defined as the distance from brake release to ½ the Air Distance Wet Runway calculations do not allow use of Clearway
Takeoff Performance Basics The Takeoff Phase is from brake release to 1500 ft or the point where the last obstacle has been cleared, if higher Three basic limitations must be taken into account: Field Length Climb Gradients Obstacle Clearance Other limitations are also restrictive and are covered during discussion on these basic limitations. They are: Structural Tire Speed Brake Energy
Takeoff Speeds V 1
Takeoff Speeds V1 official definition pilot's initiation of the first action (e.g. applying brakes, reducing thrust, deploying speed brakes) to stop the aeroplane during accelerate-stop tests JAR 25.107(a)
Takeoff Speeds V1, the Takeoff «action» speed, is the speed used as a reference in the event of engine or other failure, in taking first action to abandon the take-off. The V1 call must be done so that it is completed by V1. V2 VEF V1 35 VEF V1
Takeoff Speeds V R VR is the speed at which rotation is initiated, so that in the case of an engine failure, V2 will be reached at a height of 35 feet using a rotation rate of 2º-3º / second Regulations prohibit a RTO after rotation has been initiated, thus VR must be greater than V1. VR V1
Takeoff Speeds V 2 V2 is the takeoff safety speed. This speed will be reached at 35 feet with one engine inoperative.
Takeoff Speeds Effects on the screen height of continuing a takeoff with an engine failure prior to VEF 35 Ft 10 Ft 2 Engine 1 sec -16-8 0 +4 +8 SPEED OF ENGINE FAILURE RELATIVE TO VEF
Takeoff Speeds V1(MCG) - The Minimum Ground Control Speed This is the speed at which, in the case of a failure of the Critical Engine, it is possible to control the aeroplane by aerodynamic means only without deviating from the runway centreline by more than 30 ft, while maintaining takeoff thrust on the other engine(s). Maximum rudder force is restricted to 68 Kg (150 lbs) In demonstrating V1(MCG), the most critical conditions of weight, configuration and CG will be taken into consideration Crosswind is not considered in V1(MCG) determination Obviously VEF must be greater than V1(MCG), or the aircraft would be uncontrollable on the ground with an engine inoperative: VEF V1(MCG)
Takeoff Speeds VMC - The Minimum Control Speed This is the speed, when airborne, from which it is possible to control the aeroplane by aerodynamic means only with the Critical Engine Inoperative while maintaining takeoff thrust on the other engine(s) The demonstration is made with not more than 5º Bank into the live engine, Gear retracted (as this reduces the directional stability) and the most Aft CG (as this reduces the Rudder Moment.) (VMC may increase as much as 6 Kts. / º Bank from demonstration with wings level and Ball centred)
Field Length Criteria The Takeoff distance required for a given weight and given V1 is the greater of three different distances: Actual All-Engine Takeoff Distance x 1.15 Actual All-Engine Takeoff Distance (As Demonstrated in Tests) V1 35 ft V > V2 15% Safety Margin One Engine Inoperative Takeoff Distance VEF V1 V2 35 ft VEF V1 One Engine Inoperative Accelerate-Stop Distance
Field Length Criteria The greater of the 3 distances is the JAR Field Length required If V1 is chosen such as the 1-Engine-Inoperative Accelerate-Go and Accelerate-Stop distances are equal, the necessary field length is called Balanced and the corresponding V1 is known as a Balanced V1 Balanced V1
Field Length Criteria MTOW Fixed Runway Length ACCELERATE GO RANGE OF POSSIBLE WEIGHTS ACCELERATE STOP BALANCED V1 V1
JAR 25 Takeoff Flight Path Lift-Off Gear Retracted Flap retraction 400 Ft Min Clean 1500 Ft or Clear of Obstacles V2 V2 Acceleration Clean TO Thrust MCT 35 ft Max 5 min 1st Segment 2nd Segment 3rd Segment 4th Segment TWIN >0 2.4% acceleration or 1.2% avail. 1.2%
Obstacle Clearance For Obstacle Clearance a Net Takeoff Flight Path is considered It is not demonstrated, but rather calculated from the Gross Flight Path by reducing the gradients by a safety margin: Twin 0.8% It also will take wind into account, using 50% of the Headwind Component and 150% of the Tailwind Component, thus giving a further safety margin. The Net Takeoff Flight Path must clear all obstacles by 35 Ft
Obtacle Vs Climb 1st Segment 2nd Segment 3rd Segment 4th Segment Gross Flight Path V2 Net Flight Path 35 ft 35 ft 35 ft 35 ft
Obstacle Clearance The minimum height for flap retraction is 400ft AAL (gross) TNT A B737 : we use 800 ft AAL minimum If there is a high obstacle in the 3rd or 4th segment, we could extend the second segment to ensure that the obstacle was cleared by 35ft. Provided it still remains in the 3rd or 4th Segment We now have a Minimum Gross and Minimum Net Acceleration Height which is then corrected for elevation and temperature to give a Minimum Gross Acceleration Altitude
Obstacle Clearance Extended Second Segment Minimum Gross Acceleration Height Minimum Net Acceleration Height 35 Ft 400 Ft
Acceleration Altitude The extension of the second segment and raising of the EFFRA (JAR : EOAA) is limited as takeoff thrust must be maintained until acceleration altitude is attained The Takeoff Thrust is limited to 5 minutes and this restricts the extension of second segment
Engine Failure Procedure The Standard Engine Out Procedure (EOP) is therefore: Maintain Runway Track Climb to the EFFRA at V2 Accelerate and Retract Flaps Set MCT (max 5 min after TO power setting) Climb to the 1500 ft AGL at Flap up man. speed And then???
Distance to clear 1500 ft (B737) 3rd segment: Accel 150kts 220 kts 0.23m/s² 8 NM 2nd segment: 2.4% 1000ft @ 150kts 150 ft/nm 7 NM 4th segment: 1.2% 1500ft @ 220kts 70 ft/nm 7 NM 1st segment: >0% 140 150 kts 0'30" 3'00" 2'30" 2'00"
Obstacle Clearance Only obstacles within a certain lateral distance of the flight path are taken into account in performance calculations For each runway, Obstacle Cone is constructed for Straight Ahead or Turning Engine Out Procedures (EOP) Wind is not considered therefore correct tracking is important There is not a large margin for error for a jet airplane
Obstacle Clearance Flight Path 3000 ft 300 ft width = 0.125 x D 21600 ft 3000 ft 300 ft 3000 ft
Obstacle Clearance Flight Path
Obstacle Clearance Bank Angle has a large effect on the climb performance and therefore Obstacle Clearance GRADIENT 2.4% 1.8% 0.6% 0 15 30 BANK ANGLE
Optimisation - Improved climb Depending on the design of the aircraft and on the flap setting, the maximum climb angle speed is usually 15 to 30 kts higher than 1.13 V SR However, the selection of a V2 higher than the minimum will increase TOD The V2/VS optimisation is called «Improved Climb Method» This method consists thus in increasing the climd limited TOW at the expense of the field limited TOW. It is only applicable if runway length permits In order to obtain consistent field length, V1 and VR have to increase if V2 increases: if the runway allows an increase of V2, thus an increase in TOD, it will also allow an increase of the ASD, thus also of V1
Optimisation - Improved climb Drag Drag Curve Given TOW TO Flaps Gear UP Depending on Flap Setting, the Max Angle Speed is typically 1.13 VS + 15 to 30 Kts Vs 1.13Vs 1.28Vs EAS
Optimisation - Improved climb In order to achieve the higher V2, the VR speed must be increased The V1 speed must also be increased to ensure that there is sufficient runway to accelerate, lose and engine and be able to continue the takeoff at higher weight As V1 is higher, the VMBE speed must be checked for brake energy limits as this may become limiting
Reduced Thrust Takeoff When the actual TOW is below the maximum allowable TOW for the actual OAT, it is desirable to reduce the engine thrust This thrust reduction is a function of the difference between actual and maximum TOW JAA requires that the reduced thrust may not be less than 75% of the full takeoff thrust. Specific figures may apply for different airplanes/engines
Reduced Thrust Takeoff Assumed temperature MAX TOW Allowed TOW Act TOW Flat rated thrust OAT EGT limited thrust Assumed temperature Temp If the actual TOW is less than the maximum weight for the actual temperature, we can determine an assumed temperature, at which the actual weight would be equal to the maximum allowed TOW Having determined this assumed temperature, we can compute the take-off thrust for that temperature
Reduced Thrust Takeoff Limitations Since thrust may not be reduced below 75% of the full thrust, a max assumed temp can be determined The assumed temperature may not be less than the OAT No reduced thrust on standing water, and on contaminated or slippery runways No reduced thrust with antiskid inop or PMC OFF No reduced thrust for windshear, low visibility takeoff
Reduced Thrust Takeoff It s safe OAT = 30 C weight is MTOW V1 OAT = 10 C ASS. TEMP = 30 C weight is MTOW V1 Margin at V1
RTO execution operational margin
Landing and Go-Around Landing Distance Approach Climb Landing Climb Procedure Design Missed Approach Gradient
Landing Distance JAR 25 defines the landing distance as the horizontal distance required to bring the airplane to a standstill from a point 50 ft above the Runway Threshold. They are determined for Standard Temperatures as a function of: Weight Altitude Wind (50% Headwind and 150% Tailwind) Configuration (Flaps, Manual/Auto-Speedbrakes, Brakes) They are determined from a Height of 50 ft at VREF on a Dry (or Wet), Smooth Runway using Max Brakes, full Antiskid and Speedbrakes but No Reversers
Landing Distance Boeing describes the braking technique as Aggressive. The Brakes are fully depressed at touchdown Runway Slope is NOT accounted for Non standard temperatures are NOT accounted for Approach speed Additives are NOT accounted for These are considered to be covered by the extra margins used to define certified landing distances
Landing Distance V = 1.23 VS1G Landing Distance 60% Runway Length 50 ft Actual Landing Distance Dry Factor = 1.67 Required Landing Distance Wet Landing Distance = 1.15 x Required Landing Distance Wet Factor = 1.15
Approach Climb What is Approach 2.1% Climb?
Approach Climb Aircrafts are certified to conduct a missed approach and satisfy a Gradient of 2.1% - GROSS The configuration is: One Engine Inoperative Gear Up Go Around Flaps (15 on 737) G/A Thrust Speed must be 1.4 VSR (Strictly speaking, the Flap Setting must be an intermediate flap setting corresponding to normal procedures whose stalling speed is not more than 110% of the final flap stalling speed)
Landing Climb What is Landing Climb? 3.2%
Landing Climb Aircrafts are certified to conduct a missed approach and satisfy a Gradient of 3.2% - GROSS The configuration is: All Engines Operating Gear Down Landing Flaps (30 or 40 on 737) G/A Thrust The speed must be 1.13 VSR and VMCL It is also a requirement that full G/A thrust must be available within 8 seconds of the thrust levers forward from idle
JAA Low Visibility Climb An Aircraft must be certified to conduct a missed approach and satisfy a Gradient of 2.5% - GROSS or the published Missed Approach Gradient The configuration is: One Engine Inoperative Gear Up Go Around Flap (15 on a 737) G/A Thrust This is only applicable if Low Visibility Procedures will be conducted with a DH of below 200 Ft or No DH
Max Landing Weight The maximum landing weight for dispatch is the least of the: Field Limited Landing Weight Approach Climb Limited Landing Weight Landing Climb Limited Landing Weight JAA LVP G/A Climb Gradient Limited Landing Weight Structural Limited Landing Weight
Procedure Missed Approach Gradient 3.9% GROSS MAP + 0.6% + 0.8% 98 Ft 2.5% NET
Procedure Missed Approach Gradient Some specific procedures require a Net gradient of more than 2.5%. This will be indicated on the Chart
Procedure Missed Approach Gradient A conflict exists between JAR 25 and ICAO JAR 25 requires a Approach Climb Gradient of 2.1% Gross and a Landing Climb gradient of 3.2% Gross ICAO requires a missed approach procedure gradient of at least 2.5% Net which may require at least 3.9% Gross And Tailwind has not been accounted for
Procedure Missed Approach Gradient but what if you lose one on the go-around from a normal approach?... The case of an engine failure during Go-Around is not considered as this is deemed a remote possibility!!!
Landing Performance Data Which is the more restrictive? D Fn Both Engines 5 x Thrust Available on 1 Engine 75% With Twins, the Approach Climb will be the most limiting EAS
Procedure Missed Approach Gradient Remember the Go-Around procedure is designed for 1 engine inop With all engines operating, this should not be a problem With 1 engine inop, generally this should not be a problem If the Go Around procedure is very different to EOP procedure, then it may be prudent to use this procedure Some airfields may specify this if terrain clearance is critical
Factors affecting landing distance (Typical)
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