Perfo Briefing 737

B737B737PerformancePerformanceTakeoff & LandingTakeoff & 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

• 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 Gross 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

What is the Net Takeoff Flight Path ?

Takeoff Performance Basics

• The Net Gradient would be calculated as follows:

p% x D

Distance = D

Net Gradient

Gross Gradient

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

RUNWAY

MAX1.25%

CLEARWAY

STOPWAY

TORA

ASDA

TODA

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 BasicsThe Takeoff Phase is from brake release to 1500 ft or the

point where the last obstacle has been cleared, if higherThree 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

V1

Takeoff Speeds

“…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)

V1 “official definition”

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.

V1

V1

VEF

VEF

V2

35’

Takeoff Speeds

• 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

VR

Takeoff Speeds

V2

• 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

-16 -8 0 +4 +8

1 sec

2 Engine

SPEED OF ENGINE FAILURE RELATIVE TO VEF

HE

IGH

T A

T E

ND

OF

TO

DA

35 Ft

10 Ft

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:

VEF V1

VEF V1

V1

Actual All-Engine Takeoff Distance (As Demonstrated in Tests)

Actual All-Engine Takeoff Distance x 1.15

One Engine Inoperative Takeoff Distance

One Engine Inoperative Accelerate-Stop Distance

35 ft

35 ft

V > V2

V2

15% Safety Margin

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

V1

MTOW

ACCELERATE STOP

ACCELERATE GO

BALANCED V1

RANGE OF POSSIBLE WEIGHTS

Fixed Runway Length

JAR 25 Takeoff Flight Path

35 ft

V2

Lift-Off Gear RetractedFlap retraction

400 Ft Min Clean

1500 Ftor

Clear of Obstacles

1st Segment 2nd Segment 3rd Segment 4th Segment

V2 Acceleration Clean

TO Thrust

Max 5 min

MCT

TWIN >0 2.4% accelerationor 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

35 ft

35 ft

35 ft

35 ft

1st Segment 2nd Segment 3rd Segment 4th Segment

Net Flight Path

V2

Gross Flight Path

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

35 Ft

Minimum Net Acceleration Height

Minimum Gross Acceleration Height

400 Ft

Extended Second Segment

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)

1st segment:>0%140 – 150 kts

2nd segment:2.4% 1000ft @ 150kts150 ft/NM 7 NM

3rd segment:Accel 150kts 220 kts0.23m/s² 8 NM

4th segment:1.2% 1500ft @ 220kts70 ft/NM 7 NM

3'00" 2'30" 2'00"0'30"

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

21600 ft

300 ft

3000 ft

3000 ft

3000 ft

300 ft

width = 0.125 x D

Obstacle Clearance Flight Path

Obstacle Clearance

• Bank Angle has a large effect on the climb performance and therefore Obstacle Clearance

0 15 30

BANK ANGLE

GRADIENT

2.4%

1.8%0.6%

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 VSR

• 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

Vs 1.13Vs 1.28Vs

Drag Curve

Given TOW

TO Flaps

Gear UP

EAS

Drag

Depending on Flap Setting,

the Max Angle Speed is

typically 1.13 VS + 15 to 30 Kts



• 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 TakeoffAssumed temperature

MAXTOW

TempOAT

Flat ratedthrust EGT

limitedthrust

If the actual TOW is lessthan the maximum weightfor the actual temperature,we can determine an assumedtemperature, at which theactual weight would be equalto the maximum allowed TOW

Having determined thisassumed temperature, wecan compute the take-off thrust for that temperature

ActTOW

Assumedtemperature

AllowedTOW

• 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 TakeoffLimitations

Reduced Thrust TakeoffIt’s safe

OAT = 30°Cweight is MTOW

OAT = 10°CASS. TEMP = 30°Cweight is MTOW

V1

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:WeightAltitude 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

50 ft

Actual Landing Distance

V = 1.23 VS1G

Dry Factor = 1.67

Required Landing Distance Wet Factor = 1.15

Wet Landing Distance = 1.15 x Required Landing Distance

Landing Distance 60% Runway Length

Approach Climb

What is Approach Climb ?

2.1%

Approach Climb

• Aircrafts are certified to conduct a missed approach and satisfy a Gradient of 2.1% - GROSS

• The configuration is: One Engine InoperativeGear 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 OperatingGear DownLanding 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 InoperativeGear UpGo 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

98 Ft

2.5% NET

MAP

+ 0.8%

+ 0.6%

3.9% GROSS


Some specific procedures require a Net gradient of more than 2.5%. This will be indicated on the Chart


• 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


• The case of an engine failure during Go-Around is not considered as this is deemed a remote possibility!!!

…but what if you lose one on the go-around from a normal approach ?...

Landing Performance Data

D

Fn

EAS

Both Engines

5 x5 xThrust

Available on 1 Engine

75%

• With Twins, the Approach Climb will be the most limiting

Which is the more restrictive?


• 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)

THE END

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