B737
Performance
Takeoff & Landing
Last Rev: 02/06/2004
Takeoff Performance
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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
V1
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
VEF
V1
V1
35’
Takeoff Speeds
VR
• 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
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
35 Ft
2 Engine
10 Ft
1 sec
-16
-8
0
SPEED OF ENGINE FAILURE RELATIVE TO VEF
+4
+8
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
V > V2
35 ft
15% Safety
Margin
One Engine Inoperative Takeoff Distance
VEF V1
VEF V1
One Engine Inoperative Accelerate-Stop Distance
V2
35 ft
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
Flap retraction
400 Ft Min
Gear Retracted
Lift-Off
V2
V2
Clean
Acceleration
TO Thrust
35 ft
TWIN
1500 Ft
or
Clear of Obstacles
Clean
MCT
Max 5 min
1st Segment
2nd Segment
3rd Segment
>0
2.4%
acceleration
or 1.2% avail.
4th Segment
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
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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)
4th segment:
1.2%  1500ft @ 220kts
70 ft/NM  7 NM
3rd segment:
Accel 150kts  220 kts
0.23m/s²  8 NM
2nd segment:
2.4%  1000ft @ 150kts
150 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
width =
0.125 x D
300 ft
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%
0.6%
1.8%
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 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
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
Flat rated
thrust
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
EGT
limited
thrust
Act
TOW
OAT
Assumed
temperature
Temp
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
Margin at V1
OAT = 10°C
ASS. TEMP = 30°C
weight is MTOW
V1
RTO execution operational margin
Landing and Go-Around
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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
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 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:
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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
5x
Thrust
Available on
1 Engine
75%
EAS
• With Twins, the Approach Climb will be the most limiting
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)
THE END