7 - Performance and Flight Planning Flashcards

Question

Takeoff and Climb What is VMU speed?

Answer 1

This is the minimum demonstrated unstick speed at which it is possible to get airborne on all engines and to climb out without hazard.

Answer 2

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.

Answer 3

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.)

Answer 4

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.

Answer 5

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.

Answer 6

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.

Answer 7

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.

Answer 8

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.

Answer 9

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.)

Answer 10

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.

Answer 11

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.

Answer 12

Vr is either greater or equal to V1 but never less than V1.

Answer 13

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.

Answer 14

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

Answer 15

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.)

Answer 16

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.

Answer 17

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.

Answer 18

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.

Answer 19

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.)

Answer 20

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.

Answer 21

V2 is equal to or greater than 1.2 X V:s"

Answer 22

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.

Answer 23

V3 speed is the all-engine-operating takeoff climb speed the aircraft will achieve at the screen height.

Answer 24

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.

Answer 25

An aircraft's takeoff and landing performance is subject to many variable conditions, including 1. Aircraft weight 2. Aircraft flap setting 3. Aerodrome pressure altitude 4. Air density/density altitude (temperature and pressure altitude) 5. Humidity 6. Wind 7. Runway length, slope, and surface (including wet or icy conditions)

Answer 26

Increased aircraft weight results in a greater takeoff distance required (TODR) and a reduced net takeoff climb gradient.

Answer 27

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.

Answer 28

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.

Answer 29

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.

Answer 30

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.

Answer 31

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.

Answer 32

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.

Answer 33

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.

Answer 34

*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.

Answer 35

You are not permitted to take off from a wet (contaminated) runway when 1. The aircraft anti-skid system is inoperative. 2. The standing water level is above a specified limit. 3. Any other type-specific restrictions

Answer 36

The most restrictive field length available from either 1. The all-engine-operating runway length 2. The runway emergency distance length available, or 3. 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).

Answer 37

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).

Answer 38

The minimum height an aircraft would be able to achieve given these conditions would be the circuit height, i.e., 1500 ft.

Answer 39

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.

Answer 40

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.

Answer 41

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.)

Answer 42

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.

Answer 43

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.

Answer 44

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.

Answer 45

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.

Answer 46

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.

Answer 47

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.)

Answer 48

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.

Answer 49

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): 1. Increase takeoff flaps (remaining in the takeoff flap range) 2. Reduce takeoff weight to a level that achieves the required climb gradient that clears the obstacles 3. Increased V2 climb, maintaining takeoff weight (See Q: What is an increased~? page 206.) 4. Maximum angle climb profile [See Q: Describe maximum angle ~) climb profile, page 207.]

Answer 50

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. ```

Answer 51

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: 1. To achieve a greater obstacle clearance performance with an improved takeoff climb gradient without reducing takeoff weight 2. 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.

Answer 52

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): 1. Extended V2 climb profile technique (See Q: What is an extended V2 climb? page 207.) 2. Reduce takeoff weight to a level that achieves the required climb profile and clears the obstacle 3. 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.

Answer 53

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.

Answer 54

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.)

Answer 55

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.

Answer 56

Maximum- or best-rate climb (Vy) is the highest vertical speed that gains height in the shortest time.

Answer 57

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.

Answer 58

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.)

Answer 59

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.)

Answer 60

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.)

Answer 61

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.

Answer 62

VMO/MMO (lAS velocity/Mach) is the maximum operating speed | permitted for all operations. It is normally associated with jet aircraft.

Answer 63

VNO (lAS velocity) is the normal operating speed permitted for all normal operations. It is normally associated with propeller aircraft.

Answer 64

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.

Answer 65

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.

Answer 66

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.

Answer 67

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.

Answer 68

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.

Answer 69

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.

Answer 70

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.

Answer 71

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.

Answer 72

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.

Answer 73

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.

Answer 74

The normal en route operating performance limitations for an aircraft are 1. En route obstacle/terrain clearance with one or two engines inoperative. 2. Maximum range limit. 3. Extended twin operations (ETOPS) time limit.

Answer 75

A typical fuel profile for a flight would include sufficient fuel for the following: 1. Takeoff and climb at takeoff thrust 2. Climb to the initial cruise altitude at maximum continuous thrust. 3. En route cruise, including intermediate step climbs 4. Descent to a diversion point (go-around point) over the destination aerodrome 5. Contingency fuel 6. Diversion to over an alternative aerodrome 7. An instrument approach and landing 8. 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.

Answer 76

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.

Answer 77

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.

Answer 78

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

Answer 79

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

Answer 80

The most important question to ask in an emergency given two diversion aerodromes is, Which aerodrome is the quickest to get to?

Answer 81

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

Answer 82

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.

Answer 83

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.

Answer 84

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.

Answer 85

1000 ft, given a 3-degree glide path. This is normally distinguished by marker board markings on the runway surface.

Answer 86

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.

Answer 87

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).

Answer 88

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.

Answer 89

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.

Answer 90

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: 1. 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. 2. The greater aircraft weight and higher approach speed result in a greater momentum of the landing aircraft and therefore require more distance to stop. 3. 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.

Answer 91

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): 1. 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. 2. 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. 3. 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.

Answer 92

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).

Answer 93

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).

Answer 94

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

Answer 95

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.

Answer 96

Restricted landing weight, i.e., the maximum landing weight for the runway length (LDA) and conditions.

Answer 97

Engine-out overshoot performance, weight, altitude, and pressure (WAT), runway length (LDA) and conditions.