Performance

• Mandatory Performance
• Minimum laid down performance to be met by an aircraft for grant of
Certificate of Airworthiness
• Operational Performance
• Performance specified by the manufacturer for the day to day operation
• Demonstrated Performance
• Performance recorded during demonstration flights for obtaining Certificate of
Airworthiness

Where can you find these performances documented?

Which performance is more conservative?
 Mandatory Performance

• Gross Performance: Certification

• Average performance expected to be achieved by a fleet of aircraft type
• Net Performance: Obstacle clearance
• Performance obtained by reducing the gross performance in a specified manner
➢ Variation in Operating techniques/ maintenance practices
➢ Degradation of aircraft performance due to ageing of the fleet
➢ Deviation of environmental conditions from those assumed
 VMCG - Minimum control speed on the ground

VMCG is the CAS during the take-off run, at which, when the critical
engine is suddenly made inoperative, it is possible to maintain control of
the aeroplane with the use of the primary aerodynamic controls alone to
enable the take-off to be safely continued using normal piloting skill
 VMCG - Minimum control speed on the ground

VMCG must be established, with:

• The aeroplane in each take-off configuration (or, at the option of the applicant,
in the most critical take-off configuration)
• Maximum available take-off power or thrust on the operating engines
• The most unfavorable center of gravity
• The aeroplane trimmed for take-off
• The most unfavorable weight in the range of take-off weights
• With rudder pedal force not exceeding 150 lbs
• Assuming 7kt crosswind from INOP engine side

VMCG ≤ VEF VMCG ≤ V1

 VMCA - Minimum control speed in air

VMCA is the calibrated airspeed, at which, when the critical engine is

suddenly made inoperative, it is possible to maintain control of the
aeroplane with that engine still inoperative, and maintain straight flight
with an angle of bank of not more than 5 degrees
 VMCA - Minimum control speed in air

• VMCA may not exceed 1.2Vs with

• Maximum available take off power or thrust on the engines
• The most unfavorable center of gravity
• The aeroplane trimmed for take-off VR ≥ 1.05 VMCA
• The maximum sea-level take-off weight
• The aeroplane in the most critical take-off configuration existing along the
flight path after the aeroplane becomes airborne, except with the landing gear
retracted
• The aeroplane airborne and ground effect negligible
• During recovery the aeroplane may not assume any dangerous attitude
or require exceptional piloting skill, alertness, or strength to prevent a
heading change of more than 20 degrees
Effect of PA on VMC
 VMCL - Minimum Control Speed during
Approach and Landing

• VMCL, the minimum control speed during approach and landing with
all engines operating, is the CAS at which, when the critical engine is
suddenly made inoperative, it is possible to maintain control of the
aeroplane with that engine still inoperative, and maintain straight
flight with an angle of bank of not more than 5º
• VMCL must be established with:
• The aeroplane in the most critical configuration (or, at the option of the
applicant, each configuration) for approach and landing with all engines
operating
• The most unfavorable center of gravity
• The aeroplane trimmed for approach with all engines operating
• The most unfavorable weight, or, at the option of the applicant, as a function of
weight
• Go-around thrust setting on the operating engines
VMCL - Minimum Control Speed during Approach
and Landing
 VMU - Minimum Unstick Speed

• VMU is the CAS at and above which the airplane can safely lift off
from the ground and continue with the take-off without getting into
critical conditions
• This speed is required to be demonstrated during the certification
process
• There are two speeds to be demonstrated One with all engines
operative and second with critical engine switched off on the take-off
roll before getting airborne
 VMU - Minimum Unstick Speed

• VMU is the lowest CAS at which it is demonstrated that the aircraft

can get airborne, with both engines (VMUn) or with OEI (VMUn-1)
at take off thrust, and attain speed V2 by 35’ height
 VMU - Minimum Unstick Speed

• For the demonstration of VMU, the test pilot starts a normal take-off
• At a low speed, the pilot pulls and holds the control stick fully back
• The airplane starts a slow rotation to an angle of attack where the CL
Max value is reached or till the rear fuselage touches the runway
• The pitch attitude is maintained until Lift-off if fuselage touches
• For the trials and demonstration flights, the tail is protected by a
dragging device
• Such planes whose tail portion touches the ground, are referred to as
‘Geometrically limited’ planes
• Airplanes whose tail may not touch the ground on the process of
achieving max lift coefficient, are referred to as ‘Aerodynamically
limited’
 Minimum Unstick Speed

• The value is referred to as VMU (n) with all engines operating and VMU
(n-1) with one engine inoperative
• To find the value of VMU (n-1), the same exercise is repeated. During
the process of take-off roll, at a speed just above VMCG, the critical
engine is made inoperative
• Regulations specify that sufficient lateral control to prevent the engine
or wing touching the ground is also necessary
VLOF ≥ 1.04 VMU (N-
VMU (n) ≤ VMU (n- 1)
1)
VLOF ≥ 1.08 VMU (N)
 Stall Speed

CL

n=1g
CL
MAX
n<1g

AO
VS1g VS A
CAS
 Stall Speed

• Air Velocity over wing increases with AOA, consequently air pressure
decreases & lift coefficient (CL) increases
• Flying at constant level, an increase in CL results in decrease of
required speed
• Indeed, the lift has to balance the aircraft weight, which can be
considered as constant at a given time
 Stall Speed

•The speed cannot decrease beyond a

minimum value. Above a certain angle of
attack, the airflow starts to separate from
the aerofoil
•CL increases up to a maximum CLmax, and
suddenly decreases when the angle of
attack is increased above a certain value
•This phenomenon is called a stall
 Stall Speed
• A320 family has a low speed protection feature (alpha limit) that
flight crew cannot override
• Airworthiness authorities have reconsidered the definition of stall
speed for these aircraft
• All operating speeds must be referenced to a speed that can be
demonstrated by flight tests, which is designated as VS1g
• For aircraft models certified at VS (A300/A310),
V2min = 1.2 VS
• For aircraft models certified at VS1g (Fly-By-Wire aircraft),
V2min = 1.13 VS1g
VS = 0.94
VS1G
 VMBE – Maximum Brake Energy
Speed
• When takeoff is rejected, brakes must absorb and dissipate the heat
corresponding to aircraft’s kinetic energy at the decision point (KE =
1/2.TOW.V12)
• “A flight test demonstration of the maximum brake kinetic energy
accelerate-stop distance must be conducted with no more than 10% of
the allowable brake wear range remaining on each of the aeroplane
wheel brakes”

V1 ≤ VMBE
 VTIRE – Maximum Tire Speed

• The tire manufacturer specifies the maximum ground speed that can
be reached, in order to limit the centrifugal forces and the heat
elevation that may damage the tire structure
• For Airbus aircraft it is 195 knots
VLOF ≤
VTIRE
• This places a limit on Vr and thus on Takeoff Weight and V2
 VEF – Engine Failure Speed

• VEF is the CAS at which critical engine is assumed to fail

• VEF must be selected by the applicant, but may not be less than
VMCG
 V1 - Decision Speed

• It is the maximum CAS at which the crew can decide to reject

the take-off, and be sure that the aircraft will stop within limits
of the ASDA
• Will the aircraft stop accelerating after VEF ?

VMCG ≤ VEF ≤ V1
 VR - Rotation Speed

• VR is the speed at which the pilot initiates the rotation, at the

appropriate rate of about 3o per second
• VR in terms of calibrated air speed may not be less than
• V1
• 105% VMCA
• The speed that allows reaching V2 before reaching a height of 35 ft above the
take-off surface, or
• A speed that, if the aeroplane is rotated at its maximum practicable rate will
result in a satisfactory VLOF

VR ≥ 1.05 VMCA
 VLOF - Lift-off Speed

• VLOF is CAS at which the aeroplane first becomes airborne

• Speed at which lift overcomes the weight
• VLOF must not be less than 110% of VMU in AEO condition and not less than
105% of VMU determined at the thrust-to-weight ratio corresponding to the OEI
condition
• For geometrically limited aircraft margins can be reduced
• In the particular case that lift-off is limited by the geometry of the aeroplane, or
by elevator power, the above margins may be reduced to 108% in the AEO case
and 104% in the OEI
 V2 - Take off Climb Speed

• V2 is the minimum climb speed that must be reached at a height of 35 ft

above the runway surface, in case of an engine failure
• V2min, in terms of CAS, may not be less than:
• 1.13 VSR (For Airbus FBW VSR is 1-g stall speed VS1G)
• 1.10 VMCA
• V2 in terms of CAS, must be selected by the applicant to provide at least
the gradient of climb required by JAR, but may not be less than
• V2min
• VR plus the speed increment attained before reaching a height of 35 ft
above the take-off surface
 V2 - Take off Climb Speed

V2 ≥ 1.10 VMCA V2 ≥ 1.13 VS1G (Airbus FBW aircraft)

Speed Summary
 VLS - Lowest Selectable Speed

• As a general rule, during flight phases, pilots should not select a speed
below VLS, defined as 1.23 VS1G of the actual configuration
• This rule is applicable during LDG
• During LDG pilots have to maintain a stabilized approach, with a
CAS of no less than VLS down to a height of 50 ft above the
destination airport

VLS = 1.23 VS1G VLS = 1.3 VS, For aircraft other than FBW
GS Mini
GS Mini
GS Mini
GS Mini
Vref (landing reference speed or target threshold speed)
 GS Mini

• Winds are rarely constant during an approach, thus, the aircraft Ground
Speed should never drop below GS Mini during approach

• Therefore, aircraft IAS must vary while flying down, in order to cope
with gusts or wind changes

• To make this possible for A/THR or Pilot, the FMGS continuously

• Computes IAS Target Speed
• Which ensures that the aircraft Ground Speed is at least equal to GS Mini
• Uses instantaneous wind component experienced by the aircraft
• IAS Target Speed = GS Mini + Current HW Component
GS Mini
 GS Mini
VAPP = VLS + wind correction

GS mini = VAPP – Tower wind

IAS Target Speed = GS Mini +

Current HW Component

Target Speed Ltd by VApp in

case of Tail Wind or if
instantaneous wind is lower
than Tower Wind
 VMO/MMO – Maximum operating limit speed

• These are the speeds that may not be deliberately exceeded in any regime
of flight (climb, cruise, or descent)

• For A320-200:
VMO = 350 kt (IAS)
MMO = M0.82
 VLO - Landing Gear Operating Speed

• VLO may not exceed the speed at which it is safe both to extend and to
retract the landing gear, If the extension speed is not same as the
retraction speed, the two speeds must be designated as VLO(EXT) and
VLO(RET) respectively

• For A320-200:
VLO RET (Landing Gear Operation :
Retraction)
220 kt (IAS)
VLO EXT (Landing Gear Operation :
Extension)
 VLE - Landing Gear Extended Speed

• VLE may not exceed the speed at which it is safe to fly with the
landing gear secured in the fully extended position

• For A320-200:
VLE (Landing Gear
Extended)

280 kt /M0.67
FCOM Ref
FCOM-DSC-22_10-5-2- P 1-10/10
FCOM Ref
FCOM Ref
FCOM Ref
FCOM Ref
 Runway

• Runway is a defined area on a land aerodrome prepared for landing

and takeoff of aircraft
• It is a rigid or flexible rectangular area, on concrete or asphalt, used for
takeoff and landing

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 Runway Strip /RESA

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 RESA

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 Aerodrome Reference Code

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 A320 Reference

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 Declared Distances

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 Clearway

• The runway may be extended by an area called the clearway

• The clearway is an area beyond the runway, which should have the
following characteristics
• Be centrally located about the extended centerline of the runway, and under the
control of the airport authorities
• Be expressed in terms of a clearway plane, extending from the end of the
runway with an upward slope of not exceeding 1.25 %
• Have a minimum width of not less than 152 M (500 feet)
• Have no protruding objects or terrain
• Threshold lights may protrude above the plane, if their height above the end of
the runway is 0.66 m (26 in) or less, and if they are located on each side of the
runway

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 Takeoff Distance Available (TODA)

• The takeoff distance available (TODA) is the length of the takeoff run
available plus the length of the clearway available
• Take off distance must not exceed the TODA, with the clearway not
exceeding half of the TORA
• The takeoff distance must not exceed the takeoff distance available

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 Takeoff Distance Available (TODA)

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 Takeoff Distance

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 Takeoff Run

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 Takeoff Run

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 Takeoff Run
• Runway without clearway
• The takeoff run is equal to the takeoff distance, whatever the takeoff
surface (dry or wet)
• With a wet runway, the takeoff run with one-engine out is always equal
to the takeoff distance with one-engine out (from brake release to 15
feet)
• Therefore, a clearway does not give any performance benefit on a
wet runway, as the TOR is always more limiting (TORA is less than
TODA)

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 Takeoff Run Available (TORA)

• The takeoff run available (TORA) is the length of the runway which is
declared available by the appropriate authority and suitable for ground
run of an aircraft taking off
• TORA is either equal to the runway length, or to the distance from the
runway entry point (intersecting taxiway) to the end of the runway
• The takeoff run must not exceed the takeoff run available

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 Loss of Runway Length
Due to Alignment
• Aircrafts typically enter the takeoff runway from an intersecting taxiway
• The aircraft must be turned so that it is pointed down the runway in the direction
for takeoff
• JAA regulations require that an operator must take account of the loss, if any, of
runway length due to alignment of the aircraft prior to takeoff
• Lineup corrections should be made when computing takeoff performance, anytime
runway access does not permit positioning the aircraft at the threshold
• TOD/TOR adjustment is made, based on the initial distance from the beginning of
the runway to the main gear, since the screen height is measured from the main
gear
• ASD adjustment is based on the initial distance from the beginning of the runway
to the nose gear

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 Loss of Runway Length
Due to Alignment

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 Loss of Runway Length
due to Alignment

• Runways with displaced takeoff thresholds, or ample turning aprons should not
need further adjustments
• Accountability is usually required for a 90 degrees taxiway entry to the runway
and a 180 degrees turnaround on the runway
• Tables contain the minimum lineup distance adjustments for both the accelerate-go
(TOD/TOR) and accelerate-stop (ASD) distance cases that result from a 90
degrees turn on to the runway and a 180 degrees turn maneuver on the runway

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 Loss of Runway Length
due to Alignment

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 Loss of Runway Length
due to Alignment

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 Stopway
• The runway may be extended by an area called the Stopway
• The Stopway is an area beyond the runway, which should have the
following characteristics
• At least as wide as the runway, and centered upon the extended centerline of
the runway
• Able to support the aircraft after an abortive takeoff, without causing structural
damage to the aircraft
• Designated by the airport authorities for use in decelerating the aircraft during
an abortive takeoff
• ASDA is the length of the TORA plus the length of the Stopway, if
such Stopway is declared available by the appropriate authority and is
capable of bearing the mass of the aircraft under the prevailing
operating conditions
7/16/2019 65
 Accelerate Stop Distance

• The accelerate-stop distance (ASD) on a dry runway is the greater of

the following values
• ASD N-1 dry : Sum of the distances necessary to
• Accelerate the aircraft with all engines operating to V EF
• Accelerate from V EF to V 1 (1 second) assuming critical engine fails at V and the pilot
takes the first action to reject the takeoff at V 1
• Come to a full stop (ASD must be established with “the wheel brakes at fully worn limit
of their allowable wear range”)
• Plus a distance equivalent to 2 seconds at constant V 1 speed (no additional distance for
aircrafts manufactured pre amendment 25-42)

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 Accelerate Stop Distance

7/16/2019 67
 Accelerate Stop
Distance Available (ASDA)

7/16/2019 68
 Influence of V1 on TOD/ TOR

• For a given takeoff weight, any increase in V1 leads to a reduction in

both TOD N-1 and TOR N-1
• The reason is that the all engine acceleration phase is longer with a
higher V1 and consequently in case of an engine failure occurring at
VEF the same V2 can be achieved at 35 feet at a shorter distance
• On the other hand, TOD N and TOR N are independent of V1 as there
is no engine failure, and thus no consequence on the acceleration
phase and the necessary distance to reach 35 feet

7/16/2019 69
 Influence of V1 on ASD

• On the contrary, for a given takeoff weight, any increase in V 1 leads

to an increase in both ASD N-1 and ASD N
• Indeed, with a higher V1 the acceleration segment from brake release
to V 1 is longer, the deceleration segment from V 1 to a complete stop
is longer and the two second segment at constant V 1 is longer
• The minimum takeoff/rejected takeoff distance is achieved at a
particular speed is called “balanced V1” and the corresponding field is
called “balanced field”

7/16/2019 70
 Influence of V1 on ASDA

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 Take Off Path

• The takeoff path extends from a standing start to a point at which the
aircraft is at a height
• Of 1500 ft above the takeoff surface, Or
• At which the transition from the takeoff to the en-route configuration is
completed and the final takeoff speed is reached, whichever is higher
• Takeoff distance starts from brake release to a point at which the
aircraft reaches 35 ft above runway surface (Ground Zero)
• Takeoff flight path begins 35 ft above the takeoff surface at the end of
the takeoff distance
• Both definitions assume that the aircraft is accelerated on the ground to
VEF, at which point the critical engine is made inoperative and
remains inoperative for the rest of the takeoff
 Take Off Segments and Climb Requirements

• The takeoff flight path can be divided into several segments, which are
characteristic of a distinct change in configuration, thrust and speed
• The configuration, weight, and thrust of the aircraft must correspond to
the critical condition prevailing in the segment
• Flight path must be based on the aircraft’s performance without
ground effect
• An aircraft is considered to be out of ground effect, when it reaches a
height equal to its wing span
Take Off Segments
 Gross and Net Take Off Flight Paths

• Runways may have surrounding obstacles which must be taken into

account prior to takeoff, to ascertain that the aircraft is able to clear
them
• A vertical margin has to be considered between the aircraft and each
obstacle in the takeoff flight path
• This margin, based on a climb gradient reduction, leads to the
definitions of the Gross Takeoff Flight Path and the Net Takeoff
Flight Path
• Gross Flight Path is the takeoff flight path actually flown by the
aircraft
• Net Flight Path is the Gross takeoff flight path minus a mandatory
Gross and Net Take Off Flight Paths
 Minimum Acceleration Height

• The aircraft must reach V 2 before it is 35 ft above the takeoff surface and must
continue at a speed not less than V 2 until it is 400 ft above the takeoff surface
• At each point along the takeoff flight path, starting at the point at which the
aircraft reaches 400 ft above the takeoff surface, the available gradient of climb
may not be less than1.2% for a two-engine aircraft
• Below 400 feet, the speed must be maintained constant to a minimum of V2
 Minimum Acceleration Height

• Above 400 feet, the aircraft must fulfill a minimum climb gradient, which can be
transformed into an acceleration capability in level flight
• The regulatory minimum acceleration height is fixed to 400 feet above the
takeoff surface
• During the acceleration segment, obstacle clearance must be ensured at any
moment
• The operational minimum acceleration height is equal to or greater than 400
feet
 Maximum Acceleration Height

• The Maximum Takeoff Thrust (TOGA) is certified for use for a

maximum of 10 minutes, in case of an engine failure at takeoff, and
for a maximum of 5 minutes with all engines operating
• The Maximum Continuous Thrust (MCT), which is not time-limited,
can only be selected once the enroute configuration is achieved
• As a result, the enroute configuration must be achieved within a
maximum of 10 minutes after takeoff, thus enabling the
determination of a maximum acceleration height
 Take off Turn Procedure

• Some airports are located in an environment of penalizing obstacles,

which necessitate turning to follow a specific departure procedure
• Turning departures are subject to specific conditions
• JAR-OPS does not permit track changes up to the point at which the
net takeoff flight path has achieved a height equal to one half of the
wingspan but not less than 50 ft above the elevation of the end of
TORA
• Thereafter, up to a height of 400 ft, it is assumed that the aircraft is
banked by no more than 15 ᵒ, but not more than 25 ᵒ may be scheduled
• An operator must use special procedures, subject to the approval of the
Authority, to apply increased bank angles of not more than 20 ᵒ
Minimum Height to Initiate a Trk
Change
 Obstacle Clearance During a Straight Take off

• An operator shall ensure that the net takeoff flight path clears all
obstacles by a vertical distance of at least 35 ft
• Though the minimum required climb gradient during the second
segment must be 2.4 % for a two-engine aircraft, net flight path
limitations may require the second segment gradient to be greater than
2.4 % and consequently the Maximum Takeoff Weight may have to be
reduced accordingly
• This is a case of obstacle limitation
 Obstacle Clearance During a Turn

• fAR regulation does not consider any additional vertical margin during
a turn, as the bank angle is limited to 15 ᵒ
• As per JAR-OPS, any part of the net takeoff flight path in which the
aircraft is banked by more than 15 ᵒ must clear all obstacles by a
vertical distance of at least 50 ft
 Structural Weights

WEIGHT TAXY WEIGHT

TAXY FUEL
TAKE OFF WEIGHT (TOW)
TRIP FUEL
FUEL RESERVES LANDING WEIGHT (LW)

TOTAL TRAFFIC LOAD ZERO FUEL WEIGHT (ZFW)

CATERING, NEWS DRY OPERATING WEIGHT (DOW)

PAPERS
OPERATIONAL EMPTY WEIGHT
CABIN EQUIPMENT (OEW)
CREWS MANUFACTURER’S EMPTY WEIGHT
(MEW)
PROPULSION
SYSTEM
STRUCTURE
ZFW = DOW + traffic load
TOW = DOW + traffic load + fuel reserve + trip fuel
LW = DOW + traffic load + fuel reserve
7/16/2019 85
 Determination of Max Take Off Weight
(Structural Weight Limits)

Calculate max pay load possible if FOB is 11T at brake release including Trip fuel
of 6.5 T. Assume DOW 42.5T Max Take off Weight = 73500 Kgs Max Landing Wt
= 64500 Kgs and MZFW = 61000 T

7/16/2019 86
 Determination of Max Take Off Weight
(Structural Weight Limits)

Calculate max pay load possible if FOB is 11T at brake release including Trip fuel
of 6.5 T. Assume DOW 42.5T Max Take off Weight = 73500 Kgs Max Landing Wt
= 64500 Kgs and MZFW = 61000 T
MZW LIMIT STRUCTUCTURAL STRUCTURAL
WEIGHT TAKE OFF LIMIT LANDING LIMIT
KG WEIGHT KG WEIGHT KG
STRUCTURAL LIMIT 61000 73500 64500
WEIGHT

7/16/2019 87
 Determination of Max Take Off Weight
(Structural Weight Limits)

Calculate max pay load possible if FOB is 11T at brake release including Trip fuel
of 6.5 T. Assume DOW 42.5T Max Take off Weight = 73500 Kgs Max Landing Wt
= 64500 Kgs and MZFW = 61000 T
MZW LIMIT STRUCTUCTURAL STRUCTURAL
WEIGHT TAKE OFF LIMIT LANDING LIMIT
KG WEIGHT KG WEIGHT KG
STRUCTURAL LIMIT 61000 73500 64500
WEIGHT

Take off fuel 11000 --- Trip Fuel 6500

Max TO Wt (least of the 3)

Operating Weight
(DOW + Take off fuel)
= (MAX TRAFFIC/PAY
LOAD)
7/16/2019 88
 Determination of Max Take Off Weight
(Structural Weight Limits)

Calculate max pay load possible if FOB is 11T at brake release including Trip fuel
of 6.5 T. Assume DOW 42.5T Max Take off Weight = 73500 Kgs Max Landing Wt
= 64500 Kgs and MZFW = 61000 T
MZW LIMIT STRUCTUCTURAL STRUCTURAL
WEIGHT TAKE OFF LIMIT LANDING LIMIT
KG WEIGHT KG WEIGHT KG
STRUCTURAL LIMIT 61000 73500 64500
WEIGHT

Take off fuel 11000 --- Trip Fuel 6500

Max TO Wt (least of the 3) 72000 73500 71000
Operating Weight
(DOW + Take off fuel)
= (MAX TRAFFIC/PAY
LOAD)
7/16/2019 89
 Determination of Max Take Off Weight
(Structural Weight Limits)

Calculate max pay load possible if FOB is 11T at brake release including Trip fuel
of 6.5 T. Assume DOW 42.5T Max Take off Weight = 73500 Kgs Max Landing Wt
= 64500 Kgs and MZFW = 61000 T
MZW LIMIT STRUCTUCTURAL STRUCTURAL
WEIGHT TAKE OFF LIMIT LANDING LIMIT
KG WEIGHT KG WEIGHT KG
STRUCTURAL LIMIT 61000 73500 64500
WEIGHT

Take off fuel 11000 --- Trip Fuel 6500

Max TO Wt (least of the 3) 72000 73500 71000
Operating Weight 42500+11000 = 53500
(DOW + Take off fuel)
= (MAX TRAFFIC/PAY 17500
LOAD)
7/16/2019 90
 Take Off Weight

• Minimum of
• Take Off Limited Weight
• Structurally limited take off weight
• Performance limited weight for a given field length
• Enroute Obstacle Clearance Limit Weight
• Landing Weight
• Structural limitation (Max Ldg Wt)
• Performance limiting Ldg Wt
• Go Around Limiting Weight
• Approach climb limiting weight (OEI)
• Landing climb limiting weight (AEO)

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 Factors affecting Field Length Limit Weight

• Head wind increases TOW

• Increase in PA & Temperature reduces TOW

• Runway contamination reduces TOW

• Low pressure tire reduces TOW

7/16/2019 92
 Factors of Influence : Configuration

• Flaps increase lift... T/O Runs are reduced.

• Drag also increases ………. Effect ?

• Flaps increase drag... CONF 1+F

• T/O gradient decreases. CONF 2
CONF 3

7/16/2019 93
 Factors affecting Climb Limit Weight

• Higher V2/Vs ratio, better Climb limit TOW

• Higher flaps reduces the climb gradient, reduces TOW

• PA & Temperature increase, reduces TOW

• Lower flaps, better Climb limit TOW but poor Field limit TOW, on
longer runway preferred. Higher flaps, poor Climb limit TOW, better
Field limit TOW, preferred on shorter runway.
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 Factors of Influence : Runway Slope

Must not exceed ± 2%.

Positive slope increases T/O distances

+
2%

-
2%
Negative slope decreases T/O distances

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 Factors of Influence : Bleeds

• Air for AC and Anti Icing tapped is from airflow behind compressor
• Reduction in net flow to turbine
• Reduction in total mass flow accelerated by turbine
• Resultant reduction in thrust
• Air conditioning & Air heated Anti Icing system bleed the airflow

7/16/2019 96
 V1/VR Range

• V1 should always be less than VR

• VR depends on weight, max V1 value not fixed
• Regulatory max V1/VR ratio is equal to one
• It has been demonstrated than at a V1 speed less than 84% of VR
renders take off distances too long and there for doesn’t provide any
performance advantages
0.84 ≤ V1/VR ≤ 1

• “Any V1/VR increase (or decrease) should be considered to have the

 V2/VS Range

• Minimum V2 by regulation,
• V2min = 1.2 VS (A300/A310)
• V2min = 1.13 VS1G (FBW Aircrafts)
• So, (V2/Vs)min = 1.2 or 1.13
• Stall speed depends on weight, so min V2 not a fixed value; min v2/vs
ratio known for aircraft type
• High V2 value requires long T/O distances and results in reduction in
climb performance
• Hence V2/VS ratio is limited to a value
• V2max = 1.35 VS1g (A320 family)
•So, (V2/VS)max = 1.35
 V2/VS Range

1.13 ≤ V2/VS ≤ 1.35

“Any V2/VS increase (or decrease) should be considered to have the same
effect on takeoff performance as a V2 increase (or decrease)”
 V1/VR Selection
• For a given V2/VS, VR is governed by V2
• Higher V2 needs higher V1
• This gives shorter TOD (by increasing AEO acceleration segment)
• So higher V1/VR results in better climb performance
• V2 & VR relation ???
• For different V2/VS ratios, V1/VR can be varied as per VR
• Min V1/VR = 0.84, Max V1/VR = 1
• For V1/VR < 0.84 TOD becomes very long without proportionate
gains
• For V1/VR > 1 , VEF becomes meaningless
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 Influence of V2/Vs on MTOW

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 V2/Vs Selection

•VS ~ AUW ~ VS1G

•=> For a given WT and CONFIG, V2/VS depends on
V2 (since VS is fixed)
•Too low V2 – Less Margin from stall
•Too high V2 – TOD ↑, improved climb performance
offset by near obstacles
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 Need for Optimization

• Large aircraft operate under a wide range of

• Weight – variation in load, fuel
• Configurations – Aerodynamic / Operational requirement
• CG- Longer fuselages, Fuel burn-offs
• Thrust options
• Manufacturer’s/Regulators’/Operators’ regulations govern aircraft performance
during all phases of flight
• Structural Weight limits : MSTOW, MLW, ZFW
• Minimum Fuel – CAR
• Performance Limited Airfields – T/O & Ldg

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 Performance Optimization
•Take off optimization
• Parameters of Influence
• Thrust – Flex / Derate
• Cruise
• Altitude
• Speed
• Landing optimization
• Parameters
• Approach climb
• Landing performance

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 Parameters of Influence

•Sustained Parameters
• cannot be changed
•Free Parameters
• Selection optional
• Takeoff speeds represent the
most important source of
optimization and MTOW gain

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 Parameters of Influence

• Runway related
• TORA, TODA, ASDA : field length concept
• Line up adjustments: length decrement in
• TOD : from main wheels to end of runway
• ASD : from nose wheel to end of r/w
• Slope : acts differently on TOR & ASD (± 2%)
• Condition: optimum friction required for acceleration and
deceleration

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 Parameters of Influence
• Sustained parameters
• Wind
• HWC : 50%
• TWC :150%
• Altitude
• Pressure Altitude
• Temperature
• Engine performance : Flat Rating
• Aerodynamic performance : Control Response
• Behavior of tires , brakes (Vmbe)
• Contaminants
• Surface friction
• Precipitation drag

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 Factors of Influence: Contaminants

• Contaminants:
• Hard contaminants:
• Compacted snow
• Ice
These reduce frictional
forces
• Fluid contaminants:
• Water
• Slush These reduce friction forces, BUT cause
• Loose snow precipitation drag, spray impingement
drag and aquaplaning

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 Factors of Influence : Contaminants

• Contaminants - Precipitation drag is made of:

• Displacement drag:
Produced by the displacement of the contaminant fluid path by
the tire.
• Spray impingement drag:
Produced by the spray thrown up by the wheels (mainly those of
the nose gear) onto the fuselage.
2 effects:
• Improve the deceleration rate:
positive effect (in case of rejected takeoff)
• Worsen the acceleration rate:
negative effect (for takeoff)

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 Summary of Speed Optimization

• The highest possible MTOW

• Sustained Parameter
• Free Parameter
• Regulator
• Company
• The optimum V2/Vs ratio
• The optimum V1/VR ratio (mean/minimum)

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 Thrust Setting/EGT Limits

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 Flex Concept

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 Flex Concept

• If ATOW is less than MTOW it is possible to determine the

temperature at which the needed thrust would be the maximum thrust
for this temperature
• This temperature is called flexible temperature (TFlex) or assumed
temperature

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 Fuel Burn : Flex Take Off

The increased time at low level offsets the slight

reduction in fuel flow induced by the lower thrust

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 Enroute Segment

• Enroute segment is the portion of the flight path from 1500 ft above
takeoff surface till 1500 ft above landing surface
• Net Flight Path is the flight path along which with one engine
inoperative and the other at MCT, the climb gradient is 1.1% less than
gross climb gradient available
• The net flight path during the enroute segment must clear all
obstructions within 5 nm of the track by 1000 ft during climb/1000 ft
over plains/2000 ft over mountainous regions and 2000 ft during
descent
• There should be a positive climb gradient at 1500 ft above landing
surface
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 Lateral/Vertical Clearance

• 9.3 km (5nm) on either side the intended track

• Wider margin of 18.5 km (10Nm) if the navigational accuracy does not
meet the 95% containment level
• Vertical clearance is the margin between the net flight path and the
obstructions
• The enroute net flight path is determined from the AFM and must take
into account the meteorological conditions, wind and temperature
prevailing in the area of operations
• Moreover, if icing conditions can be expected at the diversion level,
the effect of the anti-ice system must be considered on the net flight
path
 Maneuver Margin

• When smooth flow of air over the top surface of the wing becomes
turbulent, vibrations are felt on the horizontal stabilizer and could lead
to violent oscillations of the airframe
• Separation of airflow prior to a low speed stall can cause airframe
buffet
• Buffeting occurs at pre-stall in the low speed range and at the
onset of shock wave in the high speed range
• Aerodynamic buffet is not only a “stall warning”, it can also cause
damage to aircraft structure
 Maneuver Margin

• High speed/shock wave induced buffet has more potential for damage
and is best avoided
• In normal flights, it needs to be ensured that there are no buffeting
conditions severe enough to cause excessive fatigue to crew
• Considering passenger comfort and adequate margin from buffet onset,
speeds have to be maintained within the buffet limits specified
 Pre Stall Buffet

• The speed at which the pre-stall buffet occurs (low speed buffet)
increases with
• Weight
• Reduction in configuration
• Angle of bank (or load factor which is equal to Lift/Weight = Secant of bank
angle)
• CG in more forward position
• Pressure Altitude (when speeds are expressed in Mach Numbers)
 Shock Wave Induced Buffet

• Buffet due to onset of shock wave (high speed buffet) occurs at a

specific Mach No related to Mcrit
• Allowing for a safety margin, a lower Mach No is chosen as the upper
maneuver limit
• This upper limit Mach No marginally reduces with increase in bank
angle
• The aircraft cannot fly below stalling speed (which is a CAS)
• Stalling speed increases with increase in load factor (proportional to
the square root of the load factor)
 Shock Wave Induced Buffet

• Limit load factor cannot be breached and stalling speed would

continue to increase till this limit is reached
• At high speeds, with increase in load factor, the limiting Mach number
falls
• This combination defines a buffet boundary
• The aeroplane may operate at any combination of speed and load
factor within the envelope defined, but not outside it
 Coffin Corner

• Coffin Corner is the altitude at which stall speed equals Mcrit for a
given weight and load factor
• It is difficult to keep the aeroplane in stable flight at this altitude
• As an aeroplane climbs, with increase in altitude, stalling speed is
initially constant and then starts increasing (due to compressibility)
• It also increases rapidly with increase in load factor
 Coffin Corner

• At higher altitude, the buffet boundary thus becomes much more

severe
• Above a certain altitude, the high speed buffet boundary may intersect
the stall boundary (low speed buffet), defining what is typically known
as the “coffin corner”
• In this situation if speed is reduced, aeroplane would stall and if speed
is increased it would experience high speed buffet
• This altitude is called aerodynamic ceiling
 Low Altitude Maneuver Margins

• At low altitudes i.e. during T/O, circling and approaching for landing,
speeds are low and hence upper limit Mach No is never encountered
• At these altitudes stick shaker speeds associated with various
Flaps/Slats configuration and landing gear have to be considered,
taking into account the maximum bank requirements for obstacle
avoidance and for following approach procedures
 High Altitude Maneuver Margins

• Aerodynamic Ceiling is the altitude at which there is only one speed at

which the aircraft can fly (with a LF of 1 g)
• Operating an aircraft at its aerodynamic ceiling would leave no safety
margin
• In 1 g flight the aircraft would be always at the point of stall
• No maneuver would be possible and the aircraft could stall if it
experiences even a small gust of wind
• As per regulations a minimum buffet margin of 0.3g is required
• At high altitudes, aircraft are flown in clean configuration and at high
speeds (in terms of Mach Number)
 High Altitude Maneuver Margins

• At the altitude selected for cruise, there should be adequate maneuver

margin, catering for a bank angle corresponding to a load factor of at
least 1.3g
• On the other hand, for a given altitude it is essential to know the
following limits:
• The range of speeds within which no buffet occurs at the bank required for
normal maneuvers
• The max bank at which flight can be continued without occurrence of buffet
 Specific Range

• Specific range is the distance flown per unit of fuel

• Specific range = Nm/kg or TAS/Fuel Flow
 Specific Fuel Consumption

• Specific fuel consumption (SFC) in a jet aircraft is the fuel flow per
unit of thrust
• The SFC is only an engine consideration and is not affected by drag,
which is an airframe consideration
• In a turbojet engine, SFC is lowest when the air temperature is low and
the engine is running at optimum RPM (approximately 90 to 95% of
Max RPM)
• Engine is most efficient at high altitude where the thrust required to
overcome drag is approximately 90 to 95% of the thrust available
 Optimum Altitude for Maximum Range

• Turbojet range is greatest at high altitude due to both, engine and

aerodynamic considerations
• As altitude increases, the TAS increases(for the same IAS)
• From engine consideration (low SFC) also optimum altitude is high
• However, SFC starts to increase at very high altitude when the engine
RPM exceeds optimum RPM (approximately 90 to 95% of maximum
RPM), placing restriction on optimum altitude
 Long Range Cruise

• For commercial operations, flying faster than best range speed would
enable more revenue earning flights in a specific time period resulting
in higher profits
• Balance between cost related to flying time and cost of fuel (more fuel
is burnt if aircraft flies faster) evolves into long range cruise (LRC)
speed that is approximately 4% faster than best range speed
• At LRC speed, the aircraft would cover 99% of the SAR
• LRC profile can be selected through the aircraft’s flight management
system or selected based on computation using paper documents
 Drift Down

• Drift Down Profile is carried out by selecting MCT on live engine and
following the shallowest descent path by maintaining best L/D speed
• At gross level off altitude, thrust available with one engine inoperative
just equals the drag when flying at best L/D ratio
• It depends on weight and temperature
• DDS for best L/D angle of attack depends only on instantaneous
weight
 Gross & Net Drift Down Flight Path

• The Gross Drift Down Flight Path is the flight path actually flown by
the aircraft after engine failure
• The Net Drift Down Flight Path represents the Gross flight path minus
a mandatory reduction
• The one-engine-inoperative net flight path data must represent the
actual climb performance diminished by a gradient of climb of 1.1%
for two-engine aero planes
 Cruise Mach Profile - Cost Index (CI)

• Takes into account the relationship between fuel and time related costs
in order to minimize the trip cost
• Calculated by the airline for each sector
• Affects the speeds (ECON SPEED/MACH) and cruise altitude (OPT
ALT)
• CI is the ratio of flight time cost (CT ) to fuel cost (CF)
• CI = CT /CF (kg/min)
• CI=0 corresponds to maximum range whereas the CI=999 corresponds
to minimum time
 Econ Spd/Mach

• The FMGS computes the optimum target speed (ECON SPD/MACH)

as a function of
• Cost index (CI)
• Cruise flight level (CRZ FL)
• Gross weight (GW)
• Wind and temperature models
• Performance factor
 Optimum & Maximum Altitude

• Optimum altitude is the altitude at which the airplane covers the maximum
distance per kilogram of fuel (best specific range)
• It depends on the actual weight and the deviation from ISA
• Maximum altitude is defined as the lower of
• Maximum altitude at maximum cruise thrust in level flight and
• Maximum altitude at maximum climb thrust with 300 ft/min vertical speed
 Optimum & Maximum Altitude

• The flight crew should choose a flight level that is as close to the optimum
as possible
• As a general rule, an altitude that is 4 000 ft below the optimum produces a
significant penalty (approximately 5 % of fuel)
• Flight 8000 ft below the optimum altitude produces a penalty of more than
10 % against trip fuel
 Optimum Flight Level

• The most economic flight level for a given cost index, weight and
weather data
• Compromise between fuel and time saving
• For simplification purposes, the FCOM /QRH gives the OPT FL at a
given Mach number
• It does not consider the CI, therefore the FMGS & FCOM /QRH
values are different
 Enroute Optimization

• Speed to fly
• Time Cost CI = Time cost
• Fuel Cost
Fuel cost
• Altitude to fly
• Optimum Performance Level
• Wind Altitude trade off
• OEI Strategy
• Performance
• Time
• Obstruction

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 Landing Optimization : Distance

• LDA is the declared distance available for landing

• RLD is the landing distance calculated for dispatch of flight
considerations taking into account deterioration by including a
dispatch factor
• IFLD is the landing distance required based on existing conditions
• FLD caters for operational variations of technique & reported
conditions

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 Landing

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 Landing

• Stabilised approach at VLS

• 50 ft above the threshold
• Airborne phase
• Ground phase
• Complete stop
• (No credit for – Spoilers and reversers on dry runway)

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 Definitions

• VLS is the lowest selectable speed

• 1.23 Vs1g of the actual configuration
• Final Approach Speed (VAPP) : Speed during landing, 50 ft above the
runway surface
• Flaps/Slats in ldg config
• LG extended
• Limited by VLS so that VAPP > VLS
• VAPP = VLS + Wind correction

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 Definition

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 Landing Performance

• Required Landing Distance (RLD) at Dispatch

• RLD is the Regulatory Reference to be used for Dispatch Landing
Performance Computation

• RLD should be ≥ 1.67 ALD

• Can be checked using the EFB and Tables given in FCOM (corresponding to
the MSN number & Conf)

• Increments to RLD for Automatic Landing are given at FCOM

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 Definition

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 Definitions

Approach Climb
Aircraft Configuration
• One engine inoperative
• TOGA thrust
• Gear retracted
• Slats and flaps in approach configuration (Conf 2 or 3 in most cases)
• 1.23 VS1g ≤ V ≤ 1.41 VS1g and check that V ≥ VMCL
• Gradient = 2.1%

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 Definitions

Landing Climb
• All engines thrust available 8 seconds after initiation of thrust control
movement from minimum flight idle to TOGA thrust
• Gear extended
• Slats and flaps in landing configuration (CONF 3 or FULL)
• 1.13 VS1g ≤ V ≤ 1.23 VS1g and check that V ≥ VMCL
• Gradient = 3.2%

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 Landing Optimization : Weight

• Landing Performance limited:

• Structural Limits
• Distance
• Speeds
• Influence of Parameters
• Approach Climb limited
• Climb capability in case of No Landing / Aborted
• OEI
• Landing gear up
• Regulatory Minimum Climb gradient : 2.1%

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 External Parameters Influence

• Pressure Altitude
• Approach speed is equal to 1.23 VS1g. But, the corresponding TAS
increases with the pressure altitude
• PA ↑ ρ ↓, TAS ↑
• Consequently, the landing distance will also increase
• TOGA thrust, used for go-around, decreases when pressure altitude
increases.
• PA ↑ engine thrust ↓
• Therefore, in the event of a go-around, a decrease in engine thrust implies a
decrease in the air climb gradients, which means that:
• PA ↑ Landing Distance ↑, Air Climb Gradient ↓
 External Parameters Influence

• Temperature
• Engine thrust decreases when the temperature passes the reference temperature.
Therefore, in case of a go-around, the air climb gradients will decrease.
• Temp↑ Go-around air climb gradients ↓
• Runway Slope
• From a performance standpoint, an upward slope improves the aircraft’s stopping
capability, and, consequently, decreases landing distance
• Upward slope ↑Landing distance ↓
• Downward slope ↓Landing distance ↑
 External Parameters Influence

• Runway Conditions
• When the runway is contaminated, landing performance is affected by the runway’s
friction coefficient, and the precipitation drag due to contaminants
• Friction coefficient ↓ Landing distance ↑
• Precipitation drag↑ Landing distance ↓
• Depending on the type of contaminant and its thickness, landing distance can either
increase or decrease, hence it is not unusual to have a shorter ALD on 12.7 mm of
slush than on 6.3mm
 Free Parameters Influence

• Aircraft Configuration
• Engine air bleed
• Engine air bleed for de-icing or air conditioning, implies a decrease in engine thrust
• As a result, go-around air climb gradients will decrease
• Engine air bleed ON air climb gradients ↓
• Flap setting
• An increase in flap deflection implies an increase in the lift coefficient (CL), and in the wing surface.
It is therefore possible to reduce speed such that the aircraft will need a shorter distance to land
(VS1G CONF FULL < VS1G CONF 3).
• When wing flap deflection increases, landing distance decreases
• However, when flap deflection increases, drag increases thus penalizing the aircraft’s climb
performance
• Wing Flap Deflection↑ Landing Distance↓ Air Climb gradient γ %↓
• When landing at a high altitude airport with a long runway, it might be better to decrease the flap
setting to increase the go-around air climb gradient
 Flare

• From stabilized conditions, the flare height is about 30 ft. This height
varies with different parameters, such as weight, rate of descent, wind
variations…
• The pilot will retard the thrust levers when best adapted e.g. if high
and fast on the final path the pilot will retard earlier
• A prolonged float will increase both the landing distance and the risk
of tail strike
 Braking

• Ground Spoilers
• Thrust Reversers
• Wheel Brakes
 Ground Spoilers

• When the aircraft touches down with at least one MLG and when at
least one thrust lever is in the reverse sector, the ground spoilers
partially automatically deploy to ensure that the aircraft properly sit
down on ground
• Then, the ground spoilers automatically fully deploy. This is the partial
lift dumping function
• Ground spoilers contribute to aircraft deceleration by increasing
aerodynamic drag at high speed. Wheel braking efficiency is improved
due to the increased load on the wheels. Additionally, the ground
spoiler extension signal is used for auto-brake activation
 Thrust Reversers

• Thrust reverser efficiency is proportional to the square of the speed.

Recommended to use reverse thrust at high speeds
• Select maximum reverse at MLG touch down
• A slight pitch-up, easily controlled by the crew, may appear when
the thrust reversers are deployed before the NLG touches down.
• Below 70 kts, reversers efficiency decreases rapidly. Additionally,
the use of high levels of reverse thrust at low speed can cause
engine stalls. Therefore, it is recommended to smoothly reduce the
reverse thrust to idle at 70kts. However, the use of maximum
reverse is allowed down to aircraft stop in case of emergency
• If airport regulations restrict the use of reverse, select and maintain
reverse idle until taxi speed is reached
 Wheel Brakes

• Wheel brakes contribute the most to aircraft deceleration on the

ground.
• Factors affecting efficient braking:
• Load on the wheels
• Tire pressure
• Runway pavement characteristics
• Runway contamination
• Braking technique
• The only factor over which the pilot has any control is the use of the
correct braking technique
 Auto Brake System

• Designed to help the pilot in case of :

• Rejected takeoff
• Landing on short runways
• Operation with Low Visibility weather conditions
• Ensures a straight roll-out
• Optimizes landing distance on contaminated runways if
contamination is evenly distributed
• At landing, select the braking mode according to :
• Runway length
• Configuration
• Runway condition
 Auto Brake versus Pedal Braking

• Auto Brakes are preferable

• minimizes the number of application of brake, thus reduces brake wear
• provides symmetrical brake pressure, which ensures an equal braking
effect on both main landing gear wheels on wet, or evenly contaminated
runway.
• Recommended on short, wet, contaminated runway, in poor
visibility conditions and in Auto land
• LO auto brake preferred on long and dry runways
• MED auto brake preferred for short or contaminated runways
• Timely application of MAX reverse thrust will reduce the actual
operation of the brakes themselves, thus the brake wear and
temperature.
 Anti - Skid

• The anti-skid system adapts pilot applied brake pressure to runway

conditions by sensing an impending skid condition and adjusting the
brake pressure to each individual wheel as required.
• The anti-skid system maintains the skidding factor (slip ratio) close to
the maximum friction force point. This will provide the optimum
deceleration with respect to the pilot input.
• Full pedal braking with anti-skid provides a deceleration rate of 10
kts/sec
 Factors affecting Landing Distance

• Height and speed over the threshold

• Glide slope angle
• Landing flare technique
• Delay in lowering the nose on to the runway
• Improper use of braking system
• Runway conditions
 Center Of Gravity

• The Gross Weight is the sum of Dry Operating Weight, Payload and
Fuel and acts as one force through the CG of the aircraft
• Balance Chart allows determination of the overall CG of the airplane
taking into account the CG of the empty aircraft, fuel distribution and
payload
• It must be ensured that the CG is within the allowable range referred to
as the CG envelope

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 Center Of Gravity

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 Center of Gravity

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 Center of Gravity

• A more forward CG requires a nose up pitching moment obtained

through reduced tail plane lift, which is compensated for by more
wing lift
• This creates more induced drag and leads to an increased fuel
consumption
• It is better to have the CG as far aft as possible
• As a rearward shift in CG position deteriorates the dynamic stability of
the aircraft, the CG envelope defines an aft limit

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 Center of Gravity

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 Center of Gravity

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 Center of Gravity

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 Center of Gravity

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