7 - Performance and Flight Planning Flashcards
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What is the definition of aircraft Basic Weight (BW) ?
Empty aircraft with all its basic equipment plus a declared quantity of unusable fuel and oil.
Note: For turbine-engined aircraft and aircraft not exceeding 5700 kg, the maximum authorized basic weight may include the weight of its usable oil
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What is the definition of aircraft Variable Load (VL)?
The weight of the crew, crew baggage, and removable
units, Le., catering loads, etc.
Variable load = APS - basic weight
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What is the definition of Aircraft prepared for service (APS) weight?
APS = basic weight + variable load
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What is the definition of an Aircraft’s Payload?
Passengers and/or cargo.
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What is the definition of an Aircraft’s Disposable Load?
The weight of the payload + fuel.
Disposable load = TOW - APS
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What is the definition of an Aircraft’s Ramp Weight (RW)?
Ramp Weight (RW) is the gross aircraft weight prior to taxi.
RW = TOW + fuel for start and taxi
Note: RW must be within its structural maximum (certificate of airworthiness)
weight limit.
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What is the definition of an Aircraft’s MTOW?
MTOW. Maximum takeoff weight (MTOW) is the maximum gross weight of the aircraft permitted for takeoff.
Note: Sometimes a performance-limited MTOW (i.e., short runway, obstacle clearance) may limit the aircraft to a weight less than its structural maximum (certificate of airworthiness) weight.
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What is the definition of an Aircraft’s MLW?
Maximum landing weight (MLW) is the maximum gross
weight of the aircraft permitted for landing.
Note: Sometimes a performance-limited MLW (i.e., short runway, obstacle clearance) may limit the aircraft to a weight less than its structural maximum (certificate of airworthiness) weight.
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What is the definition of an Aircraft’s ZFW?
Zero fuel weight (ZFW) is a wing loading structural maximum weight.
Thus the maximum ZFW determines the maximum permissible payload.
ZFW = payload + APS
ZFW = MTOW - fuel weight.
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What factors determine the loading (weight and balance) of an aircraft?
The factors that determine the loading (weight and balance) of an aircraft
are
1. To ensure that the following combined component weights do not exceed the aircraft’s overall gross weight limitations, i.e., MTOW, ZFW, structural maximum (certificate of airworthiness)
- The distribution of the weights ensures that the center of gravity is within its limits to longitudinally balance the aircraft.
Carrying out the weight and balancelloading calculation for an aircraft
is essential for a safe flight.
Takeoff and Climb
What is the takeoff run available (TORA)?
Takeoff run available (for all engine operations) is the usable length of the runway available that is suitable for the ground run of an aircraft taking off. In most cases this corresponds to the physical length of the runway.
Takeoff and Climb
What is the takeoff run required (TORR)?
Takeoff run required (for all engine operations) is the measured run (length) required to the unstick speed (VR ) plus one-third of the airborne distance between the unstick and the screen height.
The whole distance is then factored by a safety margin, usually 15 percent.
Takeoff and Climb
What is the runway clearway?
The clearway is the length of an obstacle-free area at the end of the runway in the direction of the takeoff, with a minimum dimension of 75 m either side of the extended runway centerline that is under the control of the licensed authority.
Note: The clearway surface is not defined and could be water.
It is an area over which an aircraft may make a portion of its initial climb
to a specified height, i.e., to the screen height, 35 ft.
Takeoff and Climb
What is the takeoff distance available (TODA)?
Takeoff distance available (for all engine operations) is the length of the usable runway available plus the length of the clearway available,
within which the aircraft initiates a transition to climbing flight and attains a screen height at a speed not less than the takeoff safety
speed (TOSS) or V2•
TODA = usable runway + clearway
Takeoff and Climb
What is the takeoff distance required (TODR)?
Takeoff distance required (for all engine operations) is the measured distance required to accelerate to the rotation speed (VR ) and thereafter effect a transition to a climbing flight and attain a screen height at a speed not less than the takeoff safety speed (TOSS) or V2.
The whole distance is factored by a safety margin, usually 15 %.
Takeoff and Climb
What is screen height?
Screen height relates to the minimum height achieved over the runway before the end of the clearway should an engine failure occur on takeoff.
The screen height also marks the end of the takeoff distance.
Takeoff and Climb
How high is the screen height for propeller and jet aircraft?
The screen height for propeller-engined aircraft in dry conditions is 50 ft.
Note: Most propeller aircraft have an increased accelerate/stop distance in wet conditions but no change in V1 or screen height.
The screen height for jet aircraft in dry conditions is 35 ft.
Note: Less than propeller aircraft due to the lower CL of the jet aircraft’s swept wing.
In wet conditions, the jet aircraft’s screen height is reduced to a minimum of 15 ft in most cases.
This is so because when an engine failure occurs at the worst point, i.e., after V1 (wet or dry) and prior to VR , a proportion of the airborne distance is added to the ground run.
(See Q: How does screen height change with a wet VI? page 191.)
Note: V2 will only be achieved at 35 ft; therefore, at a reduced screen height of 15 ft the aircraft speed will be less than V2 .
Thus screen height relates to engine failure scenarios and changes with runway conditions for jet aircraft, i.e., 35 ft for 1 engine inoperative/ dry conditions and 15 ft for 1 engine inoperative/wet conditions.
Takeoff and Climb
What is the runway stopway?
The stopway is the length of an unprepared surface at the end of the runway in the direction of the takeoff that is capable of supporting an aircraft if the aircraft has to be stopped during a takeoff run.
Takeoff and Climb
What is the emergency distance available (EMDA)/accelerate stop distance available (ASDA)?
Emergency distance available (also known as the accelerate stop distance available, or ASDA) is the length of the takeoff run available, usually the physical length of the runway, plus the length of any stopway
available.
That is,
EMDA/ASDA = usable runway + stopway available
Takeoff and Climb
What is the emergency distance/required (ED/EDR)?
Emergency distance required is the distance required to accelerate during the takeoff run on all engines to the critical speed, V1 at which point an engine failure is assumed to have occurred, and the pilot aborts the takeoff and brings the aircraft to a halt before the end of the runway or stopway if present; i.e., RTO.
The whole emergency distance is factored by a safety margin, normally 10 percent.
Note: The use of reverse thrust in the EDR calculation differs from authority to authority but usually it is not factored in the EDR calculation.
ED is sometimes referred to as an accelerated stop distance.
The EDR must not exceed the EMDA.
Takeoff and Climb
Explain balanced and unbalanced fields.
A balanced field exists when TODA = ASDA or, in other words, when the end of the clearway is the end of the stopway, and the aircraft achieves the screen height over the end of the runway in all cases.
Takeoff and Climb
What is the purpose of using balanced field calculations?
The purpose of using a balanced field calculation is to optimize the V2 climb performance (second segment) with a correct V1/VR speed from a single performance calculation/chart without having to perform a
second and separate increased V2 calculation and then readjusting the VR calculation.
Takeoff and Climb
How can a stopway extend beyond the clearway?
A stopway sometimes may extend beyond the clearway if the length of the clearway is limited because of an obstruction within 75 m of the runway/stopway centerline.
(See Q: What is the runway clearway? page 185.)
However, this obstruction does not limit the stopway, which only needs to be as wide as the runway.
Takeoff and Climb
What is the significance of the 40- to 100-knot call during the takeoff roll?
The 40- to 100-knot call during the takeoff roll is used to check the requirements that need to be established by the called speed.
These requirements include
1. Directional control surface (vertical tailplane) starts to become effective with all engines operating.
- Takeoff engine pressure ratio (EPR) should be set by this check speed so that the pilot is not chasing engine needles for a prolonged period during the takeoff roll.
- Cross-check the airspeed indicator gauges to ensure their accuracy and reliability.
In addition, type-specific requirements also might need to be established by the takeoff roll check speed.
Takeoff and Climb
What is VMU speed?
This is the minimum demonstrated unstick speed at which it is possible to get airborne on all engines and to climb out without hazard.
Takeoff and Climb
What is the critical speed?
Critical speed is the lowest possible speed on a multi-engine aircraft at a constant power setting and configuration at which the pilot is able to maintain a constant heading after failure of an off-center
engine.
VMCG/A/L are particular configurations and stage of flight critical speeds.
Takeoff and Climb
What is VMCG speed?
VMCG is the minimum control speed on the ground for a multiengine aircraft at a constant power setting and configuration, at and above which it is possible to maintain directional control of the aircraft around the normal / vertical axis by use of the rudder to maintain runway heading after failure of an off-center engine.
(See Q: How would you teach a student about VMCG/A? page 192.)
Takeoff and Climb
What is V, speed?
V1 is the decision speed in the event of an engine failure during the takeoff roll, at which it is possible to continue the takeoff and achieve the screen height within the
normal takeoff distance available or to bring the aircraft to a full stop within the emergency distance available (accelerate stop distance).
The takeoff must be abandoned with an engine failure below V1 , and the takeoff must be continued with an engine failure above V1
Note: If the TOW is limited by TODA, TORA, or EMDA, the V1 speed relates to a single point along the runway where the pilot will have the decision to continue or abort the takeoff in the event of an engine failure.
V1 cannot be less than VMCG; V1 cannot be greater than VR or VMBE.
Takeoff and Climb
How does weight affect the V1 speed?
lf the field length is limiting, the greater the aircraft weight, the lower is the V1 speed. This means that the lower V1 speed provides a greater
stopping distance while ensuring that V1 remains greater than VMCG and VMU.
If the field length is not limiting, the greater the aircraft weight, the higher is the V1 speed, providing V1 remains less than the VMBE speed and the field length emergency stopping distance is not compromised.
Takeoff and Climb
What is the difference between a dry V1 and wet V1?
A recommended wet V1 for contaminated conditions is the dry V1 - 10Kts.
Thus wet V1 is a lower speed than dry V1.
This speed may be less VMCG.
Takeoff and Climb
How does a contaminated runway (Ice and rain) affect distance and V1 speed
For a given aircraft weight on a contaminated runway, the emergency distance required is increased because of a reduced braking ability.
Also a contaminated runway has a slower acceleration, and therefore, the
TORR is increased, which limits the stopping distance available ifthe
takeoff is field-length-limited.
Takeoff and Climb
How does screen height change with a wet V1?
Screen height is reduced for a jet aircraft using a wet V1.
This is due to a portion of the airborne distance being added to the ground run as a result
of the increased ground run used between the wet V1 and VR if an engine
failure occurs at the worst point, i.e., just after the wet V1 and prior to VR.
Note: However, most propeller aircraft have no change in V1 and
screen height in wet conditions.
Takeoff and Climb
What is VMBE speed?
Maximum brake energy speed (VMBE) is the maximum speed on the ground from which a stop can be accomplished within the energy capabilities
of the brakes.
(See Q: Describe brake energy limits, page 203.)
Takeoff and Climb
What do you do if V1 is greater than VMBE?
If the VI speed exceeds the maximum brake energy speed (VMBE), then the aircraft’s takeoff weight has to be reduced until the V1 speed is less than or equal to VMBE to ensure that the aircraft does not exceed its brake energy limit.
(See Q: Describe brake energy limits,
page 203.)
Hence VMBE can limit VI and thus MTOW, especially on
downward-sloping runways with a tailwind.
An aircraft will have a set weight reduction for each knot of speed.
Note: Vr and V2 need to be redetermined for the lower aircraft weight.
Takeoff and Climb
What is VR speed?
Vn (rotation speed) is the speed at which the pilot initiates rotation during the takeoff to achieve V2 at the screen height, even with an engine failure. VR cannot be less than 1.05 VMCN1.1 or 1.05 VMU.
Takeoff and Climb
What is the relationship of V1 and VR?
Vr is either greater or equal to V1 but never less than V1.
Takeoff and Climb
What is Vs speed?
Vs (stall speed) is the speed at which the airflow over the wings will stall.
The stall speed varies with aircraft weight and configuration.
The stall speed is the reference speed for the other performance speeds, i.e., V2, Vref etc.
Takeoff and Climb
What is Va speed?
Maneuvering speed.
Maneuvering speed is the airspeed at which maximum elevator deflection causes the stall to occur at the air-frame’s load factor limit.
Va for maximum aircraft weight is specified in the flight manual
Takeoff and Climb
What is VMCA speed?
VMCA is the minimum control speed in the air for a multi-engine aircraft in the takeoff and climb-out configuration, at and above which it is possible to maintain directional control of the aircraft around the normal /vertical axis by use of the rudder within defined limits after the failure of an off-center engine.
(See Q: How would you teach a student
about VMCG/A? page 192.)
Takeoff and Climb
How does VMCG/A vary with center of gravity position?
An aft center of gravity position requires a higher VMCG/A.
(See Qs: What is VMCG/A speed? pages 189 and 192; How would you teach a student about VMCGIA? page 192.)
The turning moment acts around the center of gravity, and if the center of gravity is in the aft position, the vertical tailplane (rudder)
moment arm will be shorter, and therefore, the vertical tailplane turning moment is less for a given airspeed. Thus the aircraft requires a
higher minimum control speed (VMCG/A) with an aft center of gravity position.
A forward center of gravity will have a longer arm, and therefore, the vertical tail plane turning moment is greater for a given speed, and thus the aircraft can have a lower “‘MCG/A.
Takeoff and Climb
If VMCG is limiting for the weight of the aircraft, what can you do?
Reduce takeoff thrust.
The vertical tail plane (rudder) turning moment is used to oppose/balance the asymmetrical thrust yawing moment to maintain directional control.
Therefore, by reducing thrust, any off-center engine
loss during the takeoff run.
Takeoff and Climb
What is the relationship between VMCG and V1?
VMCG has to be equal to or less than V1
, thus ensuring that the aircraft can maintain directional control with an off-center engine failure at or above V1’ when the aircraft is committed to the takeoff and
directional control of the aircraft is essential for safe operation.
Takeoff and Climb
If you had an engine failure between V1 and VR and you had a maximum crosswind, which engine would be the best to lose, i.e., upwind or downwind engine?
Upwind engine.
This is so because the crosswind would then oppose
the yawing moment of the downwind engine. (See Q: How does a crosswind affect the critical engine? page 60.)
Takeoff and Climb
What is V2 speed?
V2 speed is the takeoff safety speed achieved by the screen height in the event of an engine failure that maintains adequate directional control and climb performance properties of the aircraft.
Note: V2 is also known as the takeoff safety speed (TOSS).
V2 cannot be less than Vs X 1.20 and VMCA X 1.10.
Takeoff and Climb
What is the relationship between Vs and V2?
V2 is equal to or greater than 1.2 X V:s”
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What is the difference between YMCA and V2?
VMCA must be less than V2.
Normally, V2 is equal to or greater than 1.1 X VMCA.
VMCA relates to the airborne directional control of the aircraft in the event of an off-center engine failure.
V2 relates to the directional
control and a minimum climb performance of the aircraft in the event of an engine failure.
Takeoff and Climb
What is V3 speed?
V3 speed is the all-engine-operating takeoff climb speed the aircraft will achieve at the screen height.
Takeoff and Climb
What is V4 speed?
V4 speed is the all-engine-operating takeoff climb speed the aircraft
will achieve by 400 ft, and is used as the lowest height where acceleration
to flap retraction speed is initiated.
Takeoff and Climb
What are the main variables (conditions) that affect an aircraft’s takeoff and
landing performance?
An aircraft’s takeoff and landing performance is subject to many variable
conditions, including
1. Aircraft weight
- Aircraft flap setting
- Aerodrome pressure altitude
- Air density/density altitude (temperature and pressure altitude)
- Humidity
- Wind
- Runway length, slope, and surface (including wet or icy conditions)
Takeoff and Climb
How does aircraft weight affect takeoff performance?
Increased aircraft weight results in a greater takeoff distance required (TODR) and a reduced net takeoff climb gradient.
Takeoff and Climb
How does the use of flaps affect the aircraft’s takeoff performance?
Small takeoff flap setting is used for the takeoff to maintain an adequate airborne climb performance.
However, large takeoff flap settings may be used to reduce the ground takeoff run as much as possible as long as the climb performance to the screen height is not compromised when the field length (runway) is limiting or the
runway surface is poor.
Conversely, no flaps may be used when takeoff
distance is limiting.
The principles of flap deployment on the takeoff performance for both swept- and straight-wing aircraft is similar, but the effects are much more acute for swept-wing aircraft.
Therefore, the use of takeoff flap deployment is much more rigid on swept-wing aircraft, whereas
straight-wing (turboprop) aircraft have more flexibility and variation
among clifferent aircraft types.
Takeoff and Climb
How does pressure altitude affect takeoff performance?
A high aerodrome elevation (high pressure altitude) decreases an aircraft’s
performance and results in an increased takeoff distance required
(TODR).
Therefore, high means a decrease in performance that results in either more takeoff distance required or a lower takeoff weight.
Takeoff and Climb
How does air density (rho)/density altitude (pressure altitude and
temperature) affect the takeoff performance?
An increase in density altitude (decrease in air density) increases
the takeoff distance required (TODR).
Therefore, hot and high mean a decrease in performance that results in either a greater TODR or
a lower TOW.
Takeoff and Climb
How does humidity affect takeoff performance?
High humidity decreases air density, which decreases an aircraft’s
aerodynamic (CL ) and engine performance and results in an increased
TORD required for a given aircraft weight.
(See Q: How does density
altitude affect the takeoff performance? page 198.)
Therefore, hot, high,
and humid mean a decrease in performance that results in either a greater TODR or a lower TOW.
Takeoff and Climb
How does wind affect the takeoff performance?
Wind has a profound effect on the takeoff performance of an aircraft.
An aircraft may experience either a headwind, tailwind, or crosswind.
(See Q: What are the crosswind limitations on an aircraft? page 200.)
Headwind. A headwind reduces the takeoff distance required for a
given aircraft weight or permits a higher TOW for the TORJD available.
Thus the greater the headwind, the better is the aircraft performance.
Tailwind. A tailwind increases the takeoff distance required for a
given aircraft weight or requires a lower TOW for the TORJD
available. Thus the greater the tailwind, the worse is the aircraft
performance. It is for this reason that a takeoff with a tailwind
shows very poor airmanship.
Takeoff and Climb
What are the recommended adjustments to headwind and tailwind
components when calculating the takeoff and landing field length
performance?
Not more than 50 percent of the reported headwind or not less than 150 percent of the reported tailwind should be used to calculate the
takeoff or landing performance.
These adjustments provide a safety margin to the reported wind
that covers acceptable fluctuations of the actual wind experienced.
Takeoff and Climb
What are the crosswind limitations on an aircraft?
The aircraft must not take off or land in a crosswind that exceeds its certified maximum crosswind limitation for the aircraft type to safeguard directly the directional and lateral control and indirectly the
takeoff run performance of the aircraft.
For crosswind component calculations, see Chapter 9, “Flight Operations
and Technique,” page 283.
Takeoff and Climb
How does the runway length, surface, and slope affect takeoff performance?
*Runway length:
The length of the available runway is one of the
performance limitations that restricts the maximum weight ofthe aircraft.
The greater the runway length, the greater is the acceleration the aircraft can gain, and higher is the lift off speed (VR ) the aircraft
can obtain.
And because the VR speed is related to aircraft weight,
it can be seen that the longer the runway available, the greater is
the possible aircraft takeoff weight.
Runway surface:
A hard and dry runway surface allows good acceleration
on the ground and therefore reduces the takeoff run required
for a given aircraft weight or allows a higher aircraft weight for a
given runway length.
On other surfaces, e.g., grass or wet contaminated
hard surfaces, the acceleration is retarded on the ground, and therefore, the takeoff run and distance required are increased.
Runway slope:
A downward slope allows the aircraft to accelerate
faster; therefore, the takeoff run and distance required for a given
aircraft weight are reduced or a higher maximum takeoff weight is
possible for a given runway length compared with a level runway.
An upward slope hinders the aircraft’s acceleration; therefore, the take off run and distance required for a given aircraft weight are
increased or the aircraft maximum takeoff weight is reduced for a
given runway length compared with a level runway.
Takeoff and Climb
When are you not permitted to takeoff from a wet runway?
You are not permitted to take off from a wet (contaminated) runway when
1. The aircraft anti-skid system is inoperative.
- The standing water level is above a specified limit.
- Any other type-specific restrictions
Takeoff and Climb
Describe field length limits.
The most restrictive field length available from either
- The all-engine-operating runway length
- The runway emergency distance length available, or
- The one-engine-inoperative runway length
…limits the aircraft’s MTOW (or MLW) so that it meets the required TOR/D performance given the ambient aerodrome conditions of pressure altitude and temperature (density).
Takeoff and Climb
Describe the weight, altitude, and temperature (WAT) limits.
The weight, altitude, and temperature (WAT) conditions limit the aircraft’s
MTOW (or MLW) so that it meets the required second segment (and missed approach) climb gradient performance with one engine inoperative given the ambient aerodrome conditions of pressure altitude
and temperature (density).
Takeoff and Climb
What guaranteed altitude / height would you be able to achieve at MTOW
WAT-limited conditions with one engine inoperative?
The minimum height an aircraft would be able to achieve given these
conditions would be the circuit height, i.e., 1500 ft.
Takeoff and Climb
What is an assumed / flexible temperature?
An assumed/flexible temperature is a performance calculation technique used to find the takeoff engine pressure ratio (EPR) setting for an aircraft’s actual Takeoff weight.
This is known as a
reduced/derated
thrust value.
In many cases, the aircraft takes off with a
weight lower than the maximum permissible takeoff weight.
When this happens, an assumed temperature performance technique presents a method of calculating a decreased takeoff thrust that is adapted for the aircraft’s actual takeoff weight.
This is done by calculating the corresponding assumed/flexible temperature (higher than the actual air temperature) from the weight, altitude, and temperature (WAT)
performance graph by using the aircraft’s actual takeoff weight as if it were the performance-limiting MTOW against the actual aerodrome
altitude to find the limiting temperature.
Takeoff and Climb
Describe tire speed limits.
Tire speed limit restricts the aircraft’s maximum takeoff weight (MTOW) given the ambient aerodrome pressure altitude, temperature,
and wind conditions so that the VR (liftoff speed) is less than the maximum rated ground speed limit for the tires to protect against the
tires blowing out during the takeoff roll.
Takeoff and Climb
Describe brake energy limits.
The brake energy capacity limits the aircraft’s maximum takeoff weight (MTOW) given the ambient aerodrome pressure altitude, temperature,
wind, and runway slope conditions so that VI does not exceed VMBE to ensure that the aircraft’s brake system has sufficient energy
to dissipate and stop the aircraft’s inertia from VI under most operating
conditions. (See Q: What is VMBE speed? page 191.)
Takeoff and Climb
How are reverse thrust, antiskid, and braking applied to stopping distance?
Reverse thrust:
In general, the performance gained by using reverse
thrust is not applied to takeoff emergency stopping distance
(EMDR) or landing stopping distance, although a 10 percent safety
factor is commonly applied to landing distance in the event of an
inoperative thrust reverser.
Antiskid:
The performance gained by using the antiskid system is
applied to both takeoff distance and landing stopping distance. If
the antiskid system is inoperative, then takeoff from a wet run-i
way is normally prohibited, and the landing calculation has a!
large safety factor calculated to its landing distance required, usually!
about 50 percent.
Braking. Maximum braking performance is applied to both takeoff
emergency stopping distance (EMDR) and landing distancel
required.
Takeoff and Climb
Describe the difference between net and gross flight paths/performance.
The difference between the net and gross flight paths/performance is
as follows:
The gross performance is the average performance that a fleet of aircraft should achieve if maintained satisfactorily and flown in
accordance with the techniques established during flight certification
and subsequently described in the aircraft performance manual.
Gross performance therefore defines a level of performance that any aircraft
of the same type has a 50 percent chance of exceeding at any time.
The net performance is the gross performance diminished to allow
for various contingencies that cannot be accounted for operationally,
e.g., variations in piloting technique, temporarily below-average performance,
etc.
It is improbable that the net performance / flight path
will not be achieved in operation, provided the aircraft is flown in
accordance with the recommended techniques, i.e., power, attitude,
and speed.
Takeoff and Climb
Describe the departure profile segments (sectors) 1 to 4.
The various segments and other terms relating to the takeoff flight
path are as follows:
Reference zero:
Defined as the ground point at the end of the takeoff
distance, below the net takeoff flight path screen height.
First (sector) segment:
Extends from the reference point (35-ft height)
to the point where the landing gear is retracted at a constant V2 speed.
Second (sector) segment.
Extends from the end of the first segment
to a gross height of between at least 400 ft and a usual maximum of
1000 ft above ground level (AGL) at a constant V2 speed.
Third (sector) segment:
Assumes a level-flight acceleration during
which the flaps are retracted in accordance with the recommended
speed schedule.
Fourth and final (sector) segment:
Extends from the third segment level-off height to a net height of 1500 ft or more with flaps up and
maximum continuous thrust.
Takeoff and Climb
What is climb gradient?
Climb gradient is the ratio, in the same units, expressed as a percentage of change in height divided by horizontal distance traveled.
The climb gradients on performance charts are true gradients for the all-up
weight (AUW) of the aircraft, which allows for temperature, aerodrome
pressure altitude, and aircraft configuration.
That is, they are achieved
from true rates of climb, not pressure.
Takeoff and Climb
Describe the net takeoff flight path (obstacle clearance).
The net takeoff flight path is the true height versus the horizontal distance
traveled from reference zero, assuming failure of the critical
engine at V1 and it is used to determine the obstacle clearance by a
specified minimal amount, normally 35 ft.
Takeoff and Climb
What is the typical jet takeoff technique and the various flight path options?
The takeoff flight path is based on the following technique and options:
The flight path begins at reference zero, where the jet aircraft has attained a height of 35 ft (in dry conditions) and V2 after failure of its
critical engine at V1 Landing gear retraction is completed at the end of the first segment, and the climb is continued at V2 with takeoff flaps and takeoff thrust on the operating engine(s) until the second- to third-segment level-off transition takes place at either
(1) a minimum gross height of 400 ft or
(2) the maximum standard gross height,
usually 1000 ft.
After option 1 or 2, the aircraft is then accelerated in level flight,
flaps are retracted, and acceleration is continued to the final segment,
where the climb is reassumed on maximum continuous thrust
or (3) the maximum height, which can be reached using either…
(1) takeoff thrust for its maximum period after the brakes are released,
usually 5 minutes, or
(2) maximum continuous thrust to an unrestricted
height.
Option 3 is used to clear distant obstacles, i.e., in the normal third segment
using an extended V2 technique to gain a greater climb gradient.
(See Qs: What is an extended V2 climb? page 207; Why is an extended
V2 climb used? page 207.)
Takeoff and Climb
What does it mean if a takeoff weight is limited by an obstacle in the
second segment?
If an aircraft is said to be takeoff-weight-limited by an obstacle in the
second segment, this means that the aircraft’s takeoff weight has to
be reduced to ensure an adequate climb performance at a normal V2
speed to clear any obstacles below the second- to third-segment leveloff
height.
Takeoff and Climb
What can you do if an aircraft is limited by a close-in obstacle in the second
departure profile segment?
If an aircraft is limited by an obstacle in the second segment because
its climb performance is insufficient to clear the obstacle(s), then
either of the following flight procedures or a combination thereof can
be used to improve the aircraft’s climb gradient and thus clear the
close-in obstacle(s):
- Increase takeoff flaps (remaining in the takeoff flap range)
- Reduce takeoff weight to a level that achieves the required climb
gradient that clears the obstacles - Increased V2 climb, maintaining takeoff weight (See Q: What is an
increased~? page 206.) - Maximum angle climb profile [See Q: Describe maximum angle ~)
climb profile, page 207.]
Takeoff and Climb
What is an increased V2?
An increased V2 is a technique for improving an aircraft’s climb gradient
performance in the second segment by increasing the V2 climb speed.
That is, increasing the V2 base speed increases lift because lift is a function
of speed, and for a given weight, an increased Vz speed will provide
an increase in lift, thus producing a greater net climb gradient.
Thus an increased V2 climb allows higher obstacles to be cleared in the second
segment climb-out profile.
Note: An increased V2 speed requires either a greater than normal takeoff distance (TOD) or a reduced aircraft weight.
Takeoff and Climb
When is an increased V2 climb profile used?
An increased V2 climb profile technique can only be used if the takeoff
weight is not restricted by field length limits so that some or all of
the excess field length can be used to increase takeoff speed VR and
thus V2 speed.
Increased V2 technique is used for the following reasons:
- To achieve a greater obstacle clearance performance with an
improved takeoff climb gradient without reducing takeoff weight - To allow a higher aircraft takeoff weight that achieves the standard
(minimum) takeoff’ climb gradient corresponding to the required
obstacle clearance gradient
The use of increased V2 techniques usually is prohibited on wet
runways.
Takeoff and Climb
What can you do if an aircraft is limited by a distant obstacle in the third
departure profile segment?
If an obstacle in the third segment limits an aircraft because the obstacle
in question is higher than the second- to third-segment level-off
height, then either of the following flight procedures or a combination
thereof can be used to clear the distant obstacle(s):
- Extended V2 climb profile technique (See Q: What is an extended V2
climb? page 207.) - Reduce takeoff weight to a level that achieves the required climb
profile and clears the obstacle - Flight path climbing turns to avoid the obstacles
Note: The distance and height of the obstacle dictate the procedures
available. However, these vary with different aircraft types because of
different performance capabilities.
Takeoff and Climb
What is an extended V2 climb?
An extended V2 climb is one in which the aircraft’s second-segment
climb; i.e., at V2 and takeoff flaps, is either
(1) continued to the highest possible level-off height, allowing for acceleration and flap retraction, if applicable, which can be reached with maximum takeoff thrust on all operating engines for its maximum time limit, normally 5 minutes, or (2) continued to an unlimited height with maximum continuous thrust, instead of takeoff thrust, that meets the aircraft's minimum acceleration and climb gradient requirements in the takeoff flight path above 400 ft.
Takeoff and Climb
Why is an extended V2 climb used?
An extended V2 climb is used to clear distant third-segment obstacles
that are higher than the normal second- to third-segment level-off
height, which is typically between 400 and 1000 ft.
An extended V2 may only be used to clear the last obstacle in the flight
path so that a normal third-segment acceleration and final-segment
profile can be achieved.
(See Q: What are the typical jet takeoff technique
and various flight path options? page 204.)
Takeoff and Climb
Describe a maximum-angle (Vx) climb profile.
Maximum- or best-angle climb (Vx) is the steepest angle or highest
gradient of climb used to clear close-in obstacles over the shortest
horizontal distance.
Takeoff and Climb
Describe the minimum-rate (Vy) climb profile.
Maximum- or best-rate climb (Vy) is the highest vertical speed that
gains height in the shortest time.
Takeoff and Climb
Describe the cruise climb profile.
The cruise climb profile is a compromise between the best en route speed profile and the best climb profile-most commonly used by commercial traffic.
It provides faster en route performance, a more comfortable aircraft attitude, better aircraft control due to lower angle of attack,
and greater airflow over the control surfaces.
Takeoff and Climb
What climb departure uses the least trip fuel?
The best rate of climb (Vy) departure uses the least trip fuel because it
ensures that the aircraft reaches its optimal cruise altitude as quickly
as possible, and therefore, the aircraft spends a greater part of its
flight time at its optimal altitude than with any other climb profile.
The optimal en route altitude has the best aerodynamic and engine
performance qualities.
By being at this optimal cruise altitude as long
as possible, the best fuel economy and specific fuel consumption (SFC)
are obtained for the largest percentage of the flight (trip), and therefore,
the least trip fuel is used.
(See Q: Why does a jet aircraft climb as
high as possible? page 69.)
Takeoff and Climb
A reduced-power climb uses more or less trip fuel, and why?
A reduced-power climb uses more trip fuel.
This is so because using a
reduced-power climb means that the aircraft has a slower rate of ascent
and therefore takes longer to reach its cruise altitude.
Consequently, it
spends less time at its optimal cruise altitude and thus uses more
trip fuel.
Note: Remember that at its optimal cruise altitude an aircraft experiences
the best aerodynamic and engine performance, which results
in the best fuel economy (SFC).
(See Q: Why does ajet aircraft climb as
high as possible? page 69.)
Takeoff and Climb
A derated takeoff will use more or less trip fuel, and why.
A derated takeoff uses more trip fuel.
This is so because, as with a
reduced-power climb, the aircraft has a slower initial rate of ascent and therefore takes longer to reach its transition to its en route climb
profile and then its cruise altitude.
Consequently, it spends less time
at its optimal cruise altitude and therefore uses more trip fuel.
Note: Remember that at its optimal cruise altitude an aircraft experiences
the best aerodynamic and engine performance, which results
in the best fuel economy (SFC).
(See Q: Why does ajet aircraft climb as
high as possible? page 69.)
En Route Performance and Flight Planning
What is VRA/MRA speed?
VRA/MRA is an airspeed for rough air conditions, or turbulence penetration
speed.
The rough airspeed is recommended for flight in turbulence
that is based on the aircraft’s VB speed (design speed for
maximum gust intensity).
It provides speed protection against the two
possibilities that stem from the effects of a disturbance in rough air
conditions.
In other words, the VRA/MRA speed is high enough to
allow an adequate margin between the aircraft stall speed and also
low enough to protect against structural damage from a high-speed
gust disturbance.
En Route Performance and Flight Planning
What is VMO/MMO speed?
VMO/MMO (lAS velocity/Mach) is the maximum operating speed
permitted for all operations. It is normally associated with jet aircraft.
En Route Performance and Flight Planning
What is VNO speed?
VNO (lAS velocity) is the normal operating speed permitted for all
normal operations. It is normally associated with propeller aircraft.
En Route Performance and Flight Planning
What is VDF/MDF speed?
VDF/MDF (IAS velocitylMach) is the maximum flight diving speed for a
jet aircraft.
It is established as the highest demonstrated speed during
flight certification trials.
En Route Performance and Flight Planning
What is VNE speed?
VNE (IAS velocity) is the never-exceed velocity.
It is associated with
propeller-driven aircraft and is a higher speed than the VNO speed, which
can be used when operationally desired but must never be exceeded.
En Route Performance and Flight Planning
What is the absolute ceiling?
The absolute ceiling is an aircraft’s maximum attainable altitude/flight
level at which the Mach number buffet and prestall buffet occur coincidentally.
This scenario is known as coffin corner.
(See Q: What is coffin
corner? page 26.) Therefore, an aircraft is unable to climb above its
absolute ceiling. The absolute ceiling is determined during flight
certification trials.
En Route Performance and Flight Planning
What is a maximum service ceiling?
The maximum service ceiling is an aircraft’s’ imposed en route maximum
operating altitude/flight level, which provides a safety margin below
its absolute ceiling.
En Route Performance and Flight Planning
Define maximum endurance and maximum range with reference to the drag curve.
The total drag generated by an aircraft is high at both high and low
airspeeds.
At high airspeeds the total drag is high because the aircraft
experiences a lot of profile drag, and at low airspeeds the total drag is
high because the aircraft experiences a lot of induced drag.
Minimum
drag occurs at an intermediate speed (VIMD).
This is presented by
an aircraft’s drag curve.
(See Qs: What is drag? page 6; Describe the
two major types ofdrag and their speed relationship, page 6; Describe
the drag curve on a propeller/jet aircraj’t, pages 7 and 8.)
Maximum endurance:
This is achieved by flying at the maximum endurance
airspeed, which is the indicated airspeed that relates to
the thrust required to balance the minimum drag (VIMD) experienced
by the aircraft. Minimum drag (VIMD) is the lowest point/airspeed
on the drag curve.
Maximum range:
This is achieved by flying at the maximum-range
airspeed. This is the indicated airspeed that balances a value of drag
slightly higher than the minimum drag point (best endurance speed)
that achieves a greater range for a given quantity offuel because the
benefits of the increased airspeed outweighs the associated increase
in drag and fuel consumption.
En Route Performance and Flight Planning
What is the difference between maximum-range cruise (MRC) and
long-range-cruise (LRC)?
Maximum-range cruise:
This is the speed at which, for a given weight
and altitude, the maximum fuel mileage is obtained. It is difficult to
establish and maintain stable cruise conditions at maximum-range
speeds.
Long-range cruise:
This is a speed significantly higher than the maximum-
range speed, i.e., 10 knot..’l (M 0.01), which results in a 1 percent
mileage loss at a constant altitude. The long-range cruise schedule
requires a gradual reduction in cruise speed as gross weight decreases
with fuel burnoff.
En Route Performance and Flight Planning
What is a cost index?
A cost index (Cl) is a performance management function that optimizes
the aircraft’s speed for the minimum cost.
Cost indices form part of a company’s stored route and are inserted
into the flight management computer (FMC).
They take into account
specific route factors such as the price of fuel at the departure and
destination airports so that the aircraft is flown at the correct speed to
balance the fuel costs against the dry operating costs.
An incorrect CI
will always cost more money.
En Route Performance and Flight Planning
How is range increased when flying into a headwind?
Range is increased when flying into a headwind because the best
range speed will be a little faster, and the airspeed represents the rate
of distance covered. Therefore, range will be increased with a headwind.
The increased fuel flow is compensated for by a higher speed,
allowing less time en route for the headwind to act.
En Route Performance and Flight Planning
A flight carried out below its optimal altitude has what results on jet
performance?
The aircraft uses more fuel because the engines are designed to
achieve their best specific fuel consumption (SFC) at a high operating
rpm, which can only be achieved at high (optimal) altitudes.
(See Q: Why does a jet aircraft climb as high as possible? page 69.)
It takes less time because by flying at a constant MN, which is normal
practice at high altitudes, i.e., above FL260, the local speed of sound
(LSS) increases the lower the altitude because LSS is a function of temperature.
En Route Performance and Flight Planning
What is a cruise (step) climb?
A cruise (step) climb occurs when an aircraft in the cruise loses
weight due to fuel burn, which allows the aircraft to fly higher; therefore,
a cruise (step) climb is initiated to climb the aircraft to its new
maximum altitude.
En Route Performance and Flight Planning
What are the normal en route operating performance limitations for
an aircraft?
The normal en route operating performance limitations for an aircraft are
- En route obstacle/terrain clearance with one or two engines inoperative.
- Maximum range limit.
- Extended twin operations (ETOPS) time limit.
En Route Performance and Flight Planning
Explain a typical fuel plan for a trip.
A typical fuel profile for a flight would include sufficient fuel for the
following:
- Takeoff and climb at takeoff thrust
- Climb to the initial cruise altitude at maximum continuous thrust.
- En route cruise, including intermediate step climbs
- Descent to a diversion point (go-around point) over the destination
aerodrome - Contingency fuel
- Diversion to over an alternative aerodrome
- An instrument approach and landing
- An additional amount of holding fuel may be required if the destination
is an island with no alternative or you are arriving at a
major airport at its busiest period, e.g., London Heathrow between
0700 and 0930.
En Route Performance and Flight Planning
What is island holding fuel, and when is it used?
Island holding fuel is a quantity of fuel uplifted usually in place of
diversion fuel that allows an aircraft to hold over a destination aerodrome
for an extended period of time.
It is often associated with sorties
to remote islands, e.g., Easter Island, where there is no diversion
option and there is a possibility of a delayed landing due to adverse
weather patterns.
En Route Performance and Flight Planning
Explain fuel howgozit?
Fuel howgozit is a comparison of the actual fuel remaining against the
planned fuel remaining along the flight path.
At any stage of flight an
estimate of the fuel difference can be obtained, and it is ideal to show
any trends, such as increasing fuel burn.
Note: Fuel howgozit charts also can be used to plan the position of
the point-of-no-return (PNR) point.
En Route Performance and Flight Planning
What is the critical point?
The critical point, or equal-time point, is the en route track position
where it is as quick (time) to go to your destination as it is to turn back.
The critical point (CP) is calculated as a distance and time from the
departure airfield using the following formula:
Distance to CP = DH/O+H
D is total distance,
H is ground speed Home
0 is ground speed Out.
Time to CP = dist to CP/O
En Route Performance and Flight Planning
How does the wind affect the position of the critical point?
The critical point moves into the wind.
Given still air conditions, the critical point (CP) between two aerodromes
is simply the halfway point.
However, the effect of wind displaces
the critical point to one side or the other of the midpoint.
Flying into a headwind moves the CP closer to the destination aerodrome, and flying
with a tailwind moves the CP closer to the departure aerodrome.
This is so because the CP is the equal time point to reach an airfield, and
therefore, ground speed is all-important, and ground speed is TAS x Wind Speed
En Route Performance and Flight Planning
What is the most important diversion question to ask in an emergency?
The most important question to ask in an emergency given two diversion
aerodromes is, Which aerodrome is the quickest to get to?
En Route Performance and Flight Planning
What is the point of no return (PNR)?
PNR (point of no return) is the last point on a route at which it is possible
to return to the departure aerodrome with a sensible fuel reserve.
Normal PNR points are based on the aircraft’s safe endurance.
The all-engine PNR formula is
Time to PNR = EH/OxH
E - safe endurance time
H - ground speed home.
O - ground speed out.
Distance to PNR = time to PNR x O
En Route Performance and Flight Planning
Where are you likely to need a point of no return (PNR)?
PNR calculations are important for aircraft for which diversion airfields
are not readily available, e.g., over large water areas such as the
Pacific Ocean.
It is crucially important to have a PNR point if you elect to carry island holding fuel instead of diversion fuel because you become solely committed to landing at our destination once you pass
the PNR point.
Note: PNR points are not really required on a route over land with
diversion airfields available en route.
Descent and landing
What is the landing distance available (LDA)?
LDA is the distance available for landing, taking into account any obstacles in the flight path, from 50 ft above the surface of the runway threshold height (fence) to the end of the landing runway.
Descent and landing
What is landing distance required (LDR)?
Landing distance required (LDR) is the distance required from the point where the aircraft is 50 ft over the runway (i.e., threshold fence height at a maximum VAT threshold speed) to the point where the aircraft
reaches a full stop.
Descent and landing
What distance along the runway is the touchdown aiming point?
1000 ft, given a 3-degree glide path. This is normally distinguished by marker board markings on the runway surface.
Descent and landing
What is the height of the aircraft over the runway threshold (fence)?
Given a 3-degree glide path and a 1000-ft touchdown, the height of the aircraft over the runway threshold fence is 50 ft.
However, larger aircraft will have a reduced clearance height due to their extended wheels.
Descent and landing
What is VMCL speed?
VMCL is the minimum control speed in the air for a multi-engined aircraft in the approach and landing configuration, at and above which it is possible to maintain directional control of the aircraft around the
normal/vertical axis by use of the rudder after failure of an off-center engine within defined limits while applying variations of power, i.e., idle to maximum thrust on the live engine(s).
Descent and landing
What is VAT/ref speed?
Velocity at threshold (VAT) / velocity reference speed (Vref) is the target approach threshold speed above the fence height for a specified flap setting
that ensures that the landing field length is constantly achieved.
VAT /Vref = 1.3 Vs in the landing configuration
VAT0 = The target threshold, all-engine operation, speed with maximum flap setting
VAT1 = the target threshold, one engine (critical) inoperative, speed
VAT2 = the target threshold, two engines inoperative, speed
Adjustments to VAT/Vref are made for headwind values.
That is, 50% of the headwind and the full gust value are added to the VAT / Vref speed up to a maximum permitted predetermined limit, e.g.,
20 knots.
Above a maximum VAT speed at the threshold, the risk of exceeding the landing field length is unacceptably high, and a go-around should be initiated.
Descent and landing
How does a fast approach speed affect landing distance?
The landing performance of an aircraft is based on specified approach
speeds (VAT / Vref).
If you approach for a landing at a speed higher than
that specified, the landing distance probably will exceed that calculated.
This can be very important if the landing distance available (LDA) is limiting.
Note: Actual approach speed below the specified approach speed should not be flown for safety reasons.
Descent and landing
How does aircraft weight affect landing performance?
Increased aircraft weight results in a greater landing distance required
(LDR).
An increased aircraft weight has the following variable effects that
increase the landing distance required:
- The stalling speed is increased with the higher aircraft weight, so
the minimum approach speed, Vref / VAT 1.3 Vs ), must be higher.
A higher approach speed requires a greater landing distance to come
to a full stop.
- The greater aircraft weight and higher approach speed result in a greater momentum of the landing aircraft and therefore require more distance to stop.
- The increased weight means that the kinetic energy (½m (V*V)) is higher, and the brakes have to absorb this greater energy, which increases the landing distance required.
Overall, an increase in weight increases the LDR.
As a guideline, a 10 percent increase in weight requires a 10 percent increase in landing
distance, i.e., a factor of 1:1.
Descent and landing
How does the use of flaps affect an aircraft’s landing performance?
Increased flap settings decrease the landing distance required.
The use of increased flap settings has the following variable effects
that decreases the landing distance required (LDR):
- Flap deployment increases lift and reduces the stalling speed (v:s).
Therefore, the approach speed, VAT / Vref (1.3Vs), is less, which results in a shorter landing distance required. - The higher the flap deployment, the greater is the aerodynamic drag that helps to slow the aircraft down, and this results in a shorter landing distance required.
- The higher the flap setting and the steeper the approach path, the lower is the forward velocity and momentum on landing, which
results in a shorter landing distance required.
Descent and landing
How does pressure altitude affect landing performance?
A high aerodrome elevation (high pressure altitude) decreases an aircraft’s performance, which results in an increased landing distance
required (LDR).
Thus hot means a decrease in performance that results
in either a greater landing distance required (LDR) or a lower landing
weight (LW).
Descent and landing
How does air density (rho)/density altitude (pressure altitude and
temperature) affect the landing performance?
An increase in density altitude (decrease in air density) decreases an aircraft’s performance, which results in an increased landing distance required (LDR).
Thus, hot and high mean a decrease in performance
that results in either a greater LDR or a lower landing
weight (LW).
Descent and landing
How does wind affect landing performance?
Wind has a profound effect on the landing performance of an aircraft.
A headwind reduces the landing distance required (LDR) for a given aircraft weight, or it permits a higher landing weight (LW) for the landing distance available (LDA).
This is so because the ground speed (GS) is reduced by the headwind (HW) for the same true airspeed (TAS).
That is,
TAS = 120 knots
HW = 20 knots
GS = 100 knot
Tailwind. A tailwind increases the LDR for a given aircraft weight,
or it requires a lower LW for the LDA.
This is so because the ground
speed is increased by the tailwind (TW) for the same TAS.
That is,
TAS = 120 knots
HW = 20 knots
GS = 140 knots
Descent and landing
How does the runway length, surface, and slope affect the landing
performance?
Runway length:
The longer the runway length and the greater the aircraft’s stopping action, the higher its VAT/Vref approach speed can be.
And because the VAT/Vref speed is related to the aircraft’s weight, it can
be seen that the longer the runway length available, the greater the aircraft’s landing weight can be.
Runway surface:
Low-friction surfaces increase landing distance
required (LDR) for a given aircraft weight because the surface does not permit effective braking.
Runway slope:
A downward slope requires a longer LD for a given
aircraft weight or a lower landing weight (LW) for a given landing distance available (LDA).
An upward slope requires a shorter
LD for a given aircraft weight or allows a higher LW for a given Runway length.
Descent and landing
What is RLW?
Restricted landing weight, i.e., the maximum landing weight for the runway length (LDA) and conditions.
Descent and Landing
What factors are taken into account on restricted landing weight (RLW)?
Engine-out overshoot performance, weight, altitude, and pressure
(WAT), runway length (LDA) and conditions.
