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MindMap Gallery flight performance
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flight performance
This is a mind map about flight performance. The main contents include: 7 aircraft landing performance, 6 aircraft cruise performance analysis, 5 climb and descent, 4 takeoff, 3 regulations and airports, 2 thrust and power, 1 basic flight principle.
Edited at 2024-04-02 21:19:11
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flight performance
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This Valentine's Day brand marketing handbook provides businesses with five practical models, covering everything from creating offline experiences to driving online engagement. Whether you're a shopping mall, restaurant, or online brand, you'll find a suitable strategy: each model includes clear objectives and industry-specific guidelines, helping brands transform traffic into real sales and lasting emotional connections during this romantic season.
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- Outline
flight performance
1 Basic flight principles
1. flight speed
Indicated airspeed/indicator speed (IAS): indicates dynamic pressure
Corrected Airspeed (CAS): Indicated airspeed corrected for position error and instrument error
Equivalent Airspeed (EAS): Corrected airspeed corrected for air compression error, the most accurate airspeed
Characterization of dynamic pressure size
True speed (TAS): the true speed of an aircraft relative to the air at altitude
Mach number (M): the ratio of true speed to local speed of sound
stall speed
Vs1g: corresponds to the maximum lift coefficient, overload coefficient n=1
Vs: Lift decreases rapidly, overload coefficient n<1
2. Force
total resistance
Parasitic resistance: proportional to CAS
Induced resistance: inversely proportional to CAS
The greater the weight, the greater the total resistance and the greater Vmd (minimum resistance speed)
In non-smooth configuration, the greater the total resistance, the smaller Vmd
Vmd is the dividing point between speed instability and stability
3. Force relationship of aircraft during flight phase
Constant speed horizontal straight flight
L=W T=D
Steady rise
T=D Wsinθ L=Wcosθ
steady decline
D=T Wsinθ L=Wcosθ
decline
D=Wsinθ L=Wcosθ
tanθ=D/L=1/K=H/Range
turn
W=L·cosφ n=1/cosφ
2 Thrust and power
1. Jet engine thrust changes with flight speed
Since the effects of the inlet momentum drag and the stamping effect cancel each other out The thrust of a low bypass ratio engine jet engine basically does not change with the flight speed.
Since the stamping effect can no longer fully compensate for the thrust reduction effect caused by the inlet momentum drag The thrust of high bypass ratio engines will decrease as flight speed increases
2. As altitude increases, air density decreases, air flow decreases, and thrust decreases
3. Thrust force changes with temperature
When T≥ISA 15℃, the engine first reaches the turbine gas temperature limit Temperature increases, thrust decreases, climb weight limit decreases
When T≤ISA 15℃, the engine first reaches the speed limit and is in the platform thrust stage. Thrust does not change with temperature and does not affect climb limit weight
4. Engine thrust setting
V(TO/GA＞MCT＞MCL＞MCR＞IDLE＞RESERVE) Takeoff, accelerated climb, climb, cruise, descent roll, landing, rejected takeoff
Maximum take-off/go-around operating status (TO/GA) Take-off/Go around
The maximum thrust state is also the worst working condition of the engine.
Use time limit ≤5min
Maximum continuous thrust state (MCT) Maximum Continuous Thrust
The maximum thrust state in which the engine can operate continuously, with no time limit for use
Can be used as the working state after the first shot fails. Ensure that the aircraft can climb quickly or fly at the highest possible altitude
Approval level
Maximum climb operating status (MCL) Maximum Climb
Rated throttle, no usage time limit
After TO/GA ends, use this status to climb to the altitude of route cruising.
Maximum cruise operating condition (MCR) Maximum Cruise
The maximum thrust that can be used during cruise, no time limit for use
For long and long distance flights
Reduced thrust/reduced power take-off status (FLEX/DERATE) Take-Off-Flexibility/Derated
Use according to the aircraft takeoff weight and airport conditions (when ATOW ≤ MTOW)
Minus rated power method
advantage
Improve operational safety
① Reduce engine load and extend engine service life
② Improve engine reliability, reduce the probability of engine failure during takeoff, and reduce the engine stall rate in the air
Increase efficiency
① Reduce the maintenance cost of maintaining the engine and reduce the cost of engine use
②Increase release reliability and passenger satisfaction
Reduce noise on both sides of the take-off profile and reduce environmental pollution
Hypothetical temperature (flexible temperature) method
advantage
①When go-around thrust is needed, full power go-around thrust can be used
②In the continued and interrupted takeoff performance when the first engine is stopped, due to the difference between the true airspeed at the flexible temperature and the true airspeed at the actual temperature, there is an additional safety margin for the live thrust takeoff
③ Take off on a longer dry runway with a larger take-off weight
shortcoming
①Subject to some restrictions: A. To satisfy Tref＜Tflex (reference temperature of the engine＜selected flexible temperature) B. Tactual＜Tflex (actual temperature＜reference temperature of engine) C. Tref＜MAX(Tflex): The selected flexible temperature ≤ the maximum flexible temperature (the temperature corresponding to when the maximum available takeoff thrust is reduced by 25%), and the thrust reduction cannot be greater than 25% of the maximum thrust, reduce the thrust The rear throttle shall not be less than the maximum ascent throttle
②Cannot be used to pollute runways
Idle working status (IDLE)
It is used in the descent or glide state of the route. It is the working state of the minimum speed at which the engine can maintain a stable and continuous working state.
Reverse working status (RESERVE)
Working state for landing and aborted takeoff, which helps reduce the load on tires and brakes
5. power
As true airspeed increases, the available power of a jet engine increases
The available power of the propeller piston engine first increases and then decreases as the true air speed increases.
Vmp=0. 76Vmd (minimum power speed < minimum resistance speed)
3 Regulations and Airports
1. Determination of performance
Measure performance
Before a new aircraft is put into commercial use, manufacturers must use prototypes to measure flight performance. The measured flight performance data include parameters such as takeoff distance, landing distance and flight gradient under aircraft configurations with flaps/slats/landing gear in different positions, with all engines working, and with single engine failed. The average value of each parameter is the measured performance
Overall performance
The average performance data that fleets of the same type should achieve when flying according to the requirements of the flight manual (no safety margin is provided)
net performance
The total performance is obtained by subtracting a safety margin issued by the appropriate regulatory agency.
Net performance is greater than the total performance required
①The landing distance requirement is longer
② The rising gradient is smaller
③The descent gradient is larger
2. Performance regulations (CCAR-121, 135)
Takeoff roll available distance (TORA)
The distance on the airport surface from a point in the direction of takeoff at which an aircraft can begin its takeoff roll to the nearest point at which it cannot carry the weight of the aircraft under normal operating conditions.
Clearance Road (CWY)
An area along the takeoff direction beyond the available distance for takeoff roll
TODA-TORA
Take-off distance available (TODA)
The available distance for takeoff is equal to the length of the runway plus the length of the clearway (TORA CWY)
1.5 times the available distance for takeoff roll (1. 5×TORA)
Stop Road (SWY)
The aircraft can safely decelerate and taxi in this lane without causing injuries to the passengers or damage to the aircraft structure.
Acceleration Stop Available Distance (ASDA)
The distance on the surface of an airport along the takeoff direction from "the point at which the aircraft can begin its takeoff roll" to "the furthest point at which the aircraft can safely decelerate and roll to a complete stop in an emergency"
RWY SWY=TORA SWY
Balance the field
The available distance for take-off and the available distance for acceleration and stop are equal (TODA=ASDA)
The length of the clearance lane and the stop lane are equal (CWY=SWY)
3. Performance classification
Transport category aircraft (CCAR-25)
Normal, utility and aerobatic aircraft
Commuter aircraft
5 Climbing and descending
climb
rising characteristics
Angle of ascent
The rising angle (γ) is the angle between the rising trajectory and the horizontal plane
sin γ=T-D/W=remaining thrust/weight
When the rising angle is not large, rising gradient = T-D/W = remaining thrust/weight
Vx: Maximum rising angular velocity
The speed at which the maximum ascent angle and maximum ascent gradient is obtained is called the maximum ascent angular speed or steep ascent speed.
Since the lift angle (γ) depends on the residual thrust, the steep lift speed Vx is the speed when the residual thrust is maximum (generally refers to a jet aircraft)
propeller aircraft
Vmx=Vmd(maximum rising angular speed=minimum resistance speed)
Influencing factors
aircraft weight
Aircraft weight↑ → remaining thrust↓ → γ↓
Aircraft configuration
Extending the flaps and landing gear will cause the total drag to increase, resulting in
As the residual thrust decreases, the lift angle decreases
The maximum rising angular speed Vx is reduced
pressure altitude
The change pattern of jet engine thrust as altitude increases will lead to
The angle of rise decreases
Maximum angular velocity Vx (as indicated airspeed) remains constant
Accelerate and turn
rising rate
The aircraft's vertical speed. In aviation, the unit of ascent rate is usually feet per minute (ft/min), which can be read from the vertical speed indicator (VSI).
Rise rate = available power - required power/W
Vy: maximum ascent rate speed
The speed at which an aircraft can achieve its maximum rate of ascent is called the maximum rate of ascent speed or rapid ascent speed
Since the rising rate depends on the residual power, the maximum rising rate speed Vy is the speed when the difference between the available power and the residual power is the largest.
P (available) = F▪v (available power = thrust × true speed)
Jet Vy
The speed at which the maximum residual power can be obtained corresponds to the maximum rise rate. This speed is Vy, which is greater than Vx.
Vy>>Vmp
At low altitude, Vy>>Vmd
Influencing factors
aircraft weight
As the weight increases, the remaining power decreases and the rate of rise decreases
Note: The minimum rate of climb speed Vy will increase as the weight of the aircraft increases
Aircraft configuration
As the flap setting increases or lowers the landing gear, the total drag curve will move up and to the left, and the required power curve will also move in the same direction.
As the residual power decreases, the rise rate also decreases
The maximum ascent rate speed Vy will become smaller
high
The higher the altitude, the residual power and ascent rate decrease
Vy (TAS) increased slightly
V(CAS) decreases
ceiling
Theoretical ceiling
A theoretical altitude at which an aircraft's rate of ascent is zero.
Vy is always greater than Vx, unless Vy≥Vx at the theoretical ceiling altitude
Because it takes an infinite time for the aircraft to rise to this altitude and reach the corresponding Vy, this is only the height that the aircraft can theoretically reach.
Practical ceiling
The altitude at which the aircraft's maximum rate of ascent drops to a certain value. This specific value varies depending on the aircraft type
Jet aircraft: 500ft/min
Propeller aircraft: 100ft/min
rising chart
Upward strategy
Gives the corrected airspeed and Mach for the climb, such as 240kt/M0.74
At lower altitudes, the aircraft maintains its specified corrected airspeed as it rises and the angle of attack remains constant, so the aircraft's true airspeed and Mach number increase.
rising performance chart
ground distance
1||| Calculate true airspeed TAS first
2||| Then calculate the ground speed GS
GS=TAS-HW (headwind) GS=TAS TW (tailwind)
3||| Finally, calculate ground speed × time = distance on the ground
Fuel consumption
1||| Look up the table and compare the data to get the fuel consumption corresponding to the altitude.
linear interpolation
2||| Correct fuel consumption based on air bleed and anti-icing conditions
weight to climb to top
Brake weight minus corrected fuel consumption
decline
drop characteristics
Angle of descent
The descent angle (γ) is the angle between the descent trajectory and the horizontal plane
sinγ=D-T/W=residual resistance/weight
The speed corresponding to the minimum descent angle
Since the descent angle depends on (D-T)/W, when the difference between resistance and thrust is the smallest, the descent angle is the smallest.
At the minimum resistance speed Vmd, the remaining resistance is the smallest
So for a jet aircraft, the minimum angular velocity of descent is Vmd
rate of decline
The speed corresponding to the minimum descent rate
At the minimum power speed Vmp, the aircraft's descent rate is minimum. Flying at this speed, the aircraft can obtain the maximum endurance time (the longest time in the air)
The speed corresponding to the maximum descent rate
In order to obtain the maximum descent rate, both the descent angle and flight speed should be as large as possible, so the maximum descent rate is usually obtained at high speed.
Since the use of the resistance device has a speed limit, the speed at which the maximum descent rate is obtained ≤ the operating limit speed MMO/VMO
decline
Unmotivated descent. For non-gliders, this means the engine is no longer providing power
glide gradient
Gradient=D/L
Descending with minimum glide angle and maximum glide distance in calm wind means
The lift-to-drag ratio L/D must be the largest
The flight speed must be the minimum drag speed Vmd
Factors affecting glide angle
aircraft weight
Maintaining the minimum drag speed Vmd, the aircraft's lift and drag increase in the same proportion. The increase in weight will not affect the aircraft's lift-to-drag ratio, glide angle, and glide distance.
But it should be noted that the minimum resistance speed is also different when the weight is different: the greater the weight, the greater the minimum resistance speed
Flaps and landing gear
Using flaps will increase the drag, which will reduce the lift-to-drag ratio and increase the glide angle.
wind
against the wind
The glide angle increases and the distance to the ground decreases.
Flight speed > minimum drag speed, flight time will be reduced to obtain the maximum ground distance in headwind
tailwind
Reduce the glide angle and increase the distance to the ground
Degraded performance chart
Descending distance Distance
Falling time
DropFuelFuel
Corrected according to the following conditions
Engine anti-icing
Total anti-icing
ISAtemperature
low altitude conditions
6 Aircraft cruise performance analysis
1. Cruise performance analysis: mainly studies the range and flight time of the aircraft
Endurance: The amount of time an aircraft can remain in the air after running out of available fuel.
Range: The horizontal distance traveled by an aircraft in a predetermined direction when it runs out of available fuel.
Influencing factors
wind
Favorable winds increase range
Headwinds shorten voyage
The temperature rises, the engine fuel consumption rate increases, and the fuel mileage and range are shortened.
In non-smooth configuration (with landing gear extended and flaps opened), the aircraft resistance increases, the required thrust increases, the lift-to-drag ratio decreases, and the fuel mileage and range are shortened.
Deviation from optimal cruising altitude, reduced fuel mileage and range
Main parameters of civil aviation aircraft cruise status
cruising altitude
cruising speed
Cruise power and thrust
Net range: end of takeoff stage (35ft above the ground) → approach and landing (1500ft above the ground)
Block fuel consumption: sliding out of the apron → sliding into the apron, the fuel consumption in between is called block fuel consumption, and the elapsed time is called block time.
Range fuel ratio SR (Specific Range): the distance flown per unit of fuel consumption
The greater the fuel mileage, the longer the range
Fuel range ratio = distance / fuel = true air speed / fuel flow = TAS / FF
Jet aircraft range fuel ratio
Maximum range speed = 1. 32·Vmd
At this cruising speed, flight consumes the least fuel and has the longest flight distance.
Effect of weight
As the cruise progresses, fuel consumption and aircraft weight decrease
Fuel mileage SR gradually increases
Maximum range cruise Mach number, long range cruise Mach number gradually decreases
Fuel flow FF (Fuel Flow): the amount of fuel consumed by the aircraft per unit time
Thrust is proportional to fuel flow
Fuel consumption rate SFC (Special Fuel Consumption): The amount of fuel consumed per unit time to generate unit thrust is an important indicator of the engine.
Under low temperature conditions, the jet engine's speed is within the range of 90 to 95% of its design speed, and the fuel consumption rate is the lowest.
During the cruise stage, the maximum lift-to-drag ratio K depends on the angle of attack α and the Mach number M. The greater the Mach number M, the smaller the maximum lift-to-drag ratio K; M·K is called aerodynamic efficiency
Maximum Range Cruise (MRC): Cruise at the corresponding Mach number, with the longest cruise time
Long Range Cruise (LRC): A greater increase in speed at the expense of a smaller decrease in fuel mileage
Long range cruise is 1% less than maximum range cruise (SRᴸ=99%SRᴹ)
Determination of optimal cruising altitude
At a given weight and Mach number, the area and airflow adiabatic number of the wing are both constant.
As the pressure altitude increases and the air pressure decreases, the lift coefficient needs to be increased, that is, the angle of attack is increased, and the fuel mileage first increases and then decreases.
The altitude at which maximum SR can be obtained is called the optimal cruising altitude
The weight decreases, the fuel mileage increases, and the corresponding optimal altitude increases. The decrease in lift results in a decrease in cruise resistance and a decrease in required thrust.
The voyage altitude corresponding to LCR is higher than that corresponding to MCR
Staircase cruise
Below the 290 level, each climb shall not exceed 2000ft; Above altitude level 290, each climb shall not exceed 4000ft.
Maximum operating altitude of civil aviation transport aircraft
Maximum cruise altitude: the maximum altitude that can be maintained using maximum cruise thrust
Climb ceiling: Use maximum climb thrust to climb to the altitude corresponding to the specified remaining climb rate.
Bounce ceiling height: the corresponding height when buffeting occurs under a given load factor
Bounce ceiling (BC): Severe buffeting of the aircraft structure due to airflow separation
Low-speed jitter: At large angles of attack, the airflow separation point moves back and forth quickly within a certain range, and the lift generation point and size change drastically, causing jitter.
High-speed jitter: There is a supersonic zone on the wing surface during cruise. As the Mach number increases, the shock wave intensifies. Due to its unstable position, the lift position oscillates and changes, causing jitter.
The aircraft's available flight speed range is determined by low-speed jitter and high-speed jitter. As altitude increases, the available speed range shrinks; Generally, the maximum altitude corresponding to a margin of 1.3g is called the jitter ceiling. At this altitude, when the aircraft slopes to 40°, high-speed and low-speed jitter occur simultaneously.
Bounce chart
1||| Determine the low-speed and high-speed speed ranges where chattering occurs
2||| Determine the altitude at which buffeting occurs—the aerodynamic ceiling
3||| Determine the overload (slope) at which buffeting occurs
Wind speed factor table
Determine the optimal cruising altitude based on cruising altitude and aircraft weight
Cruise performance chart
1||| Determine fuel mileage and fuel flow based on aircraft weight and cruise altitude
2||| Corrected fuel mileage and fuel flow for engine anti-icing, total anti-icing, and low air flow
3||| Conversion between ground distance and air distance: air distance = (ground distance × true air speed) ÷ (true air speed wind direction correction amount)
2. Economy Cruising and Cost Index
airline cost structure
Direct Operating Charge (DOC)
Composed of fuel costs, time costs, and regular costs
DOC=Q oil Q when Q is determined
Q oil = C oil × W oil; Q time=C time×T
Flying at the economic Mach number is called economic flying or lowest cost operation, with the lowest direct operating expenses
DOC first decreases and then increases as the Mach number M increases.
Mmo＞M economy＞Mmrc
Indirect Operating Charge (IOC)
Cost index CI: the ratio of hourly cost to fuel cost
A high cost index indicates high time costs or low fuel prices, so increase the flight speed appropriately. It can reduce the expenditure on time (profit) > the expenditure on fuel (loss); the economic cruise M number is large
A low cost index indicates high fuel prices or low hourly costs, so the speed should not be increased too much; the economic cruise M number is small.
The cost index is zero, which means that regardless of time cost, the M number of economic cruises = the M number of long-distance cruises
The cost index is the maximum value, then the M number of economic cruise is the maximum flight speed
CI is between 30 and 80, economical cruising≈LRC
The relationship between range and take-off weight, fuel capacity and commercial load
First voyage range (maximum payload range): flight distance ≤ economic range range To increase the range within this range, you only need to increase fuel and do not need to reduce the payload.
Subject to maximum zero fuel weight
Second range range (maximum fuel range): The distance is greater than the economic range and the maximum take-off weight can be maintained; To increase the range within this range, the only way is to reduce the cargo load to increase fuel; Cannot be determined by CI (M economy), generally use MRC for cruising
Limited by maximum brake weight
Summarize
Within the first and second ranges, as the voyage increases, the payload first remains unchanged and then decreases; The fuel load keeps increasing, and the total take-off weight first increases and then remains unchanged; Aircraft should fly within the economic range
Within the economic range, use CI to determine the economic Mach number
Apart from economical voyages, cruising with MRC is the most economical
The third flight range (transfer range): To increase the range within this range, the only way to increase the payload is to reduce the take-off weight
Limited by maximum fuel
3. Performance Analysis of Engine Failure on Route
Drifting procedure
① After one engine fails, balance the aircraft and select the remaining engine thrust as the maximum continuous thrust; ② During the climb or cruise process, adjust the aircraft speed to a favorable drift speed; ③Climb or descend at a favorable drift speed until reaching the drift ceiling limit
Drift ceiling: the maximum altitude that can be flown while maintaining drift (levelling altitude)
Stopping a single engine requires deducting a certain climb gradient: 1. 1% for a two-engine aircraft, 1. 4% for a three-engine aircraft, and 1. 6% for a four-engine aircraft.
For three-engine and four-engine aircraft, a certain climb gradient must be subtracted when parking two engines, 0. 3% for three engines and 0. 5% for four engines
Requirements that the net flight path should meet
（1） There is a positive gradient at an altitude of at least 300m above all terrain and obstacles within 25km on both sides of the intended flight path; After engine failure, there is a positive gradient at an altitude of 450m above the airport where the aircraft will land.
（2） The aircraft is allowed to continue flying from the cruising altitude to an airport where it can land in accordance with the prescribed requirements, and can vertically transcend all terrain and obstacles within 25km on both sides of the intended flight path with a margin of at least 600m; After the engine failed, there was a positive gradient at an altitude of 450m above the airport where the aircraft was to land.
3 ways to fly after leveling
1. Keep flying at the drifting speed. As the fuel consumption decreases, the weight of the aircraft decreases and the altitude of the aircraft continues to increase. (Always maintain maximum altitude, longer flight time)
2. Maintain altitude after leveling off. As fuel is consumed and the weight of the aircraft decreases, the speed will gradually increase to long-range cruising speed, and then maintain long-range cruising speed. (Flight time can be shortened)
3. After leveling, immediately lower the altitude to the MRC/LRC altitude corresponding to the weight, and then fly at the same altitude. As the weight decreases, the speed gradually decreases (Maximum range)
Drift performance chart
Line table
①Calculate ISA deviation based on altitude and temperature (-6. 5℃/1000m, 2℃/1000ft)
② Determine the cruise altitude based on ISA deviation and aircraft weight
③According to the ISA deviation and whether anti-icing is turned on, correct it first to get the total ceiling
④According to the aircraft weight and ISA deviation, the net ceiling is corrected on the basis of the total ceiling
sheet
① Find the corresponding drift ceiling based on the aircraft weight and ISA deviation
②The air distance is obtained based on the ground distance and headwind and headwind conditions.
③Determine the required fuel based on the distance in the air and the weight of the aircraft
Curve table
①According to the aircraft weight and ISA deviation, the equivalent total weight is obtained
②Determine fuel consumption and time based on leveling height and equivalent total weight
③Determine the forward distance based on time and headwind and headwind components
4. Analysis of oxygen supply performance for cabin pressure relief during route
oxygen supply system
（1） chemical oxygen system
Pull down the mask to use and do not stop
Oxygen flow is determined only by time and not by cabin altitude
Oxygen supply time is available in several different specifications: 12, 15, and 22 minutes.
Maximum flight profile scheduled
（2） gas oxygen system
Select the number of oxygen bottles according to customer requirements
Oxygen flow depends on altitude, the lower the altitude, the less oxygen flow
Oxygen supply time depends on the number of oxygen bottles and flight profile
The cabin altitude is lower than 10,000ft and there is no oxygen flow
7 Aircraft landing performance
1. landing operating speed
1. Restricted speed: Vᴹᶜᴸ (minimum control speed for landing). When the engine suddenly stops, the pilot can maintain flight and the minimum approach speed with a slope of no more than 5°
The aircraft approaches and lands in the most critical configuration with all engines
The center of gravity is in the most disadvantageous position
The aircraft is trimmed according to the approach status with all engines working.
Operating engines set to go-around power
2. Minimum selectable speed (flaps 3°): Vls＝1.3Vs≥Vmcl (use to 50ft above the ground)
3. Landing approach reference speed Vref: the speed to maintain a safety margin for landing (minimum landing speed 50ft above the ground when landing with full flaps)
Vref=1.3Vs≥1.23Vsr0
4. Final approach speed Vapp: runway threshold speed, the speed that the aircraft should reach when it descends to 50 feet and crosses the runway head. Flaps/slats in landing position, landing gear down
Vapp=Vref wind correction (No corrections for tailwinds, corrections for headwinds)
Vapp=1.23Vs1g
5. Touchdown speed Vtd: the speed of the aircraft at the moment of landing
Landing weight increases, Vtd increases
Air density decreases and Vtd increases
The ground angle of attack is large and Vtd is reduced.
2. landing distance
Landing: The process from 50 feet above the airport entrance to a complete stop
1. Available landing distance LDA ≤ runway length TORA
（1） There are no obstacles on the landing path, LDA=TORA
Stop. Clearways are not used for landings
（2） If there are obstacles on the landing track, the runway inward movement distance is defined as the 2% angle between a point on the runway and the top of the obstacle plus 60m.
2. Certified landing distance CLD: the distance from 50 feet above the runway to the distance required to achieve a complete stop on the runway
Braking measures (without using reverse thrust)
brake
spoilers
anti-lag system
Vapp=1.23Vs1g
Consider conditions
ISAtemperature
Runway without slope
dry runway
3. Actual landing distance RLD: represents the best performance of the aircraft under actual conditions
Certified landing distance safety margin
Braking measures (reverse thrust can be used)
brake
spoilers
anti-lag system
Consideration scope
condition
Meteorological and runway conditions
Dry runway: RLD dry=1.67×CLD dry
Wet runway: RLD wet=1.15×1.67×CLD dry=1.9205×CLD dry
Pollution runway: RLD pollution=Max{1.15×CLD pollution, RLD wet}≤LDA
actual approach speed
temperature, slope
weight, configuration
Use: automatic braking, automatic landing system, HUD head-up display
3. Main factors affecting landing distance
1. The greater the landing weight, the longer the landing distance
2. The higher the airport pressure altitude and temperature, the longer the landing distance.
3. The approach height is too high
The touchdown point moved forward and was too high according to visual inspection, resulting in a longer landing distance.
Resulting in delayed touchdown of the aircraft, resulting in drifting and increased distance in the air
4. Approach speed is too high
Landing distance increases
Aircraft delayed touchdown, long landing distance
It is easy to slip on the water surface
5. flap angle
The larger the flap angle, the shorter the landing distance, but the smaller the go-around gradient.
At high altitude airports, the flaps are used at a smaller angle
6. With and against the wind
4. Use of landing braking measures
The purpose of solid grounding: trigger the braking system as soon as possible
Braking system composition
1. Braking (provides 70% resistance)
Automatic braking: controls brake pressure according to predetermined deceleration rate
1||| Short delay time and short landing distance
2||| Reduce the workload of the crew
3||| The brakes are continuous and stable, reducing wheel wear and extending the life of the brake device.
Manual braking can be used to obtain maximum braking force
2. Brake anti-lag system (prerequisite: the pilot applies the brakes steadily)
By adjusting the brake pressure, the wheel is maintained at an optimal slip rate of 10%
3. spoilers
flight spoilers
1||| Increase flight resistance, slow down or increase glide rate
2||| Auxiliary ailerons for lateral operation
Ground spoiler: destroys wing lift, increases drag to slow down, and enhances braking ability
4. Reverse thrust (used during high-speed rolling phase)
Produce reverse thrust and quickly decelerate
Release when the speed is reduced to below 60 or 70 knots
When using automatic braking, the main function is to avoid wear and tear on the braking system
Using manual braking or wet runway conditions will significantly shorten the landing distance.
Precautions
（1） Establish a stable approach and avoid high speeds and altitudes
（2） Ground firmly and lower the front wheel as soon as possible after touching the ground
（3） Brake the aircraft quickly after touchdown
5. Factors limiting maximum landing weight
1. Maximum certified landing weight: a fixed value in the aircraft performance manual and does not change due to actual conditions
2. Available site length limit
runway conditions
Dry runway: RLD dry=1.67×CLD dry
Wet runway: RLD wet=1.15×1.67×CLD dry=1.9205×CLD dry
Pollution runway: RLD pollution=Max{1.15×CLD pollution, RLD wet}≤LDA
Field length and weight limit
Line table
Based on available landing distance, Runway dry and wet conditions, Downwind and headwind conditions, Airport pressure altitude determines maximum landing weight
sheet
1||| The wind correction field length is obtained based on the available landing distance, headwind and headwind.
2||| The maximum landing weight is obtained based on the wind correction field length and airport pressure altitude.
3. Missed approach climb gradient limits
6. Use of Landing Performance Analysis Table
4 take off
1. definition
The aircraft starts from the brake release point at the end of the runway and accelerates until the aircraft is higher than 1500 feet above the ground. Complete the transformation from take-off to route climb configuration, and the ascent height reaches the specified value required by regulations And the speed is not lower than Vfto (Vfto≥1. 25Vs, 1.18 Vsr) process
2. Take-off stage
Field stage
The process of the aircraft accelerating and taxiing to a height of 35ft above the ground, and the speed is not lower than the safe take-off speed V₂
channel stage
From 35ft above the ground to no less than 1500ft above the ground, the speed increases to no less than 1.18 Vsr, The climb gradient meets the minimum gradient requirements stipulated by regulations, and the stages of landing gear retraction and engine power state transition are completed.
Section I
It starts from the reference zero point (35ft) and ends when the landing gear is fully retracted (the landing gear retraction action can start before the channel section I)
The flaps are in the take-off position and the engine is in TO/GA (take-off/go-around operating status), The speed is between V₂~V₂＋20kt
Section II (climbing section at constant surface speed)
From the landing gear fully retracted to a height of not less than 400ft
The flaps are in the take-off position and the engine is in TO/GA (take-off/go-around operating status), The speed is between V₂~V₂＋20kt
If there are obstacles on the channel, you should cross the obstacles before entering section III of the channel.
Section III
Reduce the angle of rise or level off to increase the speed of the aircraft
According to the specified flap retraction speed, retract all the flaps in several times, and at the same time increase the speed to the full retraction speed of the flaps.
Often use MCL (maximum rising working state) or MCT (maximum continuous working state) This state is often used for climbing after an engine is stopped.
Section IV
Increase to the prescribed speed and keep the indicated speed up to no less than 1500ft
Use MCL (maximum rising working condition) or MCT (maximum continuous working condition)
total ascent gradient
Ascent gradient calculated from Flight Performance Manual
Total takeoff flight path: flight path obtained from the total ascent gradient (actual path)
net ascending gradient
A safety margin is subtracted from the total ascent gradient. That is, the ascending gradient after the decrease in the ascending gradient caused by the pilot control error and changes in aircraft performance is taken into account.
Net takeoff flight path: The takeoff path obtained from the net ascent gradient
Safety margins stipulated by regulations: 0.8% for two engines, 0.9% for three engines, 1.0% for four engines
3. Takeoff speed
speed limit
Stalling speed: Vs, Vs1g (Stalling speed)
Vs1g: corresponds to the maximum lift coefficient, overload coefficient n=1
Vs: Lift decreases rapidly, overload coefficient n<1
Minimum control speed
Minimum control speed in the air: VMCA (Minimum control speed airborne)
In flight, if a key engine suddenly fails at this speed, the minimum speed at which the pilot can maintain a stable straight flight of the aircraft using normal control skills is the corrected airspeed.
control requirements
The slope towards the side of the working engine is ≤5°
Rudder pedal force ≤150lb
Course change ≤20°
Vmca≤1.2Vs
Influencing factors
The higher the airport altitude and temperature, the lower the speed.
The greater the weight, the slower the speed
The better the rudder surface effect, the smaller the speed
Minimum ground control speed: VMCG (Minimum control speed ground)
During the takeoff roll, if the key engine suddenly stops and the other engines are in takeoff mode, the pilot can maintain the minimum speed for stable straight-line taxiing by using aerodynamic control surfaces (steering wheel and rudder) and normal control skills. is the corrected airspeed.
Operational requirements
Rudder pedal force ≤150lb
Lateral offset ≤30ft
Minimum ground speed: VMU (Minimum Unstick speed)
The minimum speed at which an aircraft can leave the ground in the maximum allowable ground pitch attitude, expressed as corrected airspeed, is the minimum speed at which the aircraft can safely leave the ground and continue takeoff without the tail of the aircraft scraping the ground when all engines are working or one engine fails.
The vertical component of the thrust of the whole engine is greater than the vertical component of the thrust when the first engine fails, and the lift required for the full engine to lift off the ground is less than the lift required when the first engine fails to lift off the ground.
Vmu(n-1)≥Vmu(n)
Engine failure speed: VEF (Engine failure speed)
The critical engine failure speed Vef is the corrected airspeed assuming critical engine failure and must be selected by the applicant
Vef≥Vmcg
Maximum braking energy speed: VMBE (Maximum brake energy speed)
The maximum speed at which the brakes convert all the aircraft's kinetic energy into heat energy without attenuating the braking performance.
The aircraft's kinetic energy depends on its weight and the ground speed at the decision point
The heavier the aircraft, the smaller the maximum braking energy speed Vmbe
For a given weight, the corrected airspeed corresponding to the maximum ground speed is not the same under different conditions of air density and wind speed.
Maximum tire speed: VTire (Maximum tire speed)
It is the maximum achievable ground speed specified by the tire manufacturer in order to limit the centrifugal force and internal and external pressure differences that may damage the tire structure.
When operating at a high-temperature plateau airport, the air density is low, which will result in a higher true speed above the ground for the same surface speed above the ground, making it easier to be restricted by tire speed.
Running speed
Takeoff decision speed: V₁ (Take-off decision speed)
Expressed by corrected airspeed, the distance to continue takeoff and the distance to abort takeoff will not exceed the distance available for takeoff.
In case of engine failure during takeoff roll
If the speed is less than V₁, the flight will be terminated
The speed is equal to V₁, choose to continue takeoff or abort takeoff (Decision time ≤ 1s)
If the speed is greater than V₁, continue taking off
ΔV＋Vmcg≤V₁≤Vmbe≤Vr
Front wheel lifting speed: Vr (Rotation speed)
The purpose of wheel raising is to increase the angle of attack of the aircraft, obtain sufficient lift, and shorten the taxiing distance.
The wheel lifting rate is 3°/s (Vr→Vlof)
Impact on takeoff
If Vr is too large, the aircraft will need to consume more time and distance to accelerate, and it will leave the ground before reaching the predetermined attitude.
If Vr is too small, the aircraft will not have enough lift to reach the predetermined attitude after leaving the ground, which may easily cause the aircraft to hit the tail or leave the ground at a low speed.
limit
V₁≤105%Vmca≤Vr
Ensure that the aircraft reaches V₂ before it is 35ft above the ground
If the aircraft heads up at the maximum practicable nose-up rate at a certain speed, then The obtained Vlof ≥ 110% Vmu (n-1), a safety margin of 10% higher than the stall speed; And ≥105%Vmu(n), a safety margin of 5% higher than the minimum safe control speed
Guaranteed Vlof≤Vtire
The effect of air density on it
At an airport with low temperature and low altitude (high air density), Vr≥1. 05Vmca
At an airport with high temperature and high altitude (low air density), Vr≥1. 1Vmu
Ground speed: VLOF (Lift-off speed)
Definition: The instantaneous speed at which an airplane accelerates to the point where lift equals gravity.
limit
Whole hair: Vlof≥1. 1Vmu(n)
Single shot: Vlof≥1. 05Vmu(n-1)
Safe take-off speed: V₂ (Take-off Climb speed)
Definition: The minimum speed that the aircraft should reach at 35 feet above the ground after the critical engine fails at V₁
speed limit
Maintain sufficient safety margin above Vmca and stall speed
V₂≥(V₂)ᵐⁱⁿ
1. 1Vmca
1. 2Vs or 1. 13Vsr
(V₂)ᵐⁱⁿ = MAX
Vr ΔV (Vr plus the speed gain gained before reaching 35ft above the takeoff runway)
V₂=MAX
(V₂) Influencing factors of ᵐⁱⁿ
Air density
In the case of high air density, it is limited by Vmca (generally subject to restrictions)
When the air density is small, (V₂)ᵐⁱⁿ is limited by Vsr and decreases
flaps
retract flaps
weight
weight reduction
will cause the stall reference speed Vsr to decrease
Situation restricted by Vmca
①The outside temperature is low
②The air pressure at the airport is low
③The flap setting angle is large
④The aircraft is light in weight
Final takeoff speed: VFTO (Final take-off speed)
Selected by the applicant to provide at least a climb gradient required by "CCAR (25.121)"
Speed limit: Vfto≥1. 18Vsr
Minimum landing control speed: VMCL (Minimum Control Landing Speed)
Landing approach reference speed: Vref (Landing Approach Reference Speed)
Final approach speed: VAPP (Final Approach Speed)
Ground speed: VTD (Touch Down Speed)
Vef＜V₁≤Vr＜Vlof＜V₂
4. Takeoff distance
Relationship between required and available takeoff distances
The distance required for the aircraft to take off cannot exceed the distance provided by the runway
Takeoff weight is limited by runway length
Available distance
Available distance for takeoff roll: TORA (Take Off Running Available)
Equal to the length of the runway, or the length from the runway entry point (cross taxi point) to the end of the runway
TORA=RWY
Clearance Road: CWY (Clear way)
space extension area outside the runway
characteristic
On an extension of the runway centerline and controlled by the airport authority
Extending from the end of the runway, the slope does not exceed 1.25%
Width not less than 500 feet
No protruding terrain or obstacles
Length must not exceed half the distance available for takeoff roll
Available distance for takeoff: TODA (Take Off Distance Available)
TORA CWY
RWY CWY
TODA=
Once an obstacle passes through the space extended by this plane, the clearway will no longer be used. At this time, TODA is equal to TORA.
Stop: SWY (Stop Way)
Areas outside the runway
characteristic
At least as wide as the runway, with the centerline on the extension of the runway centerline
Ability to support aircraft during aborted takeoff without causing structural damage to the aircraft
Designed by the airport authority to be used only to slow down aircraft during aborted takeoff
Available distance for acceleration and stopping: ASDA (Accelerate Stop Distance Available)
Prerequisite for use is a declaration by the airport authority that the stopway can carry the weight of the aircraft under prevailing operating conditions
TORA SWY
RWY SWY
ASDA=
Pre-sliding section
Runway length lost due to aircraft colliding with the runway
length
Available distance for takeoff roll TORA=runway length RWY-pre-taxi section A
Available takeoff distance TODA = runway RWY clearway CWY - pre-slip section A
The two distance adjustments are based on the initial distance from the runway head to the main wheel (rear wheel), because the barrier height (takeoff end distance 35ft) is measured from the main wheel
Available acceleration and stopping distance ASDA = runway RWY stopway SWY - pre-slip section B
Calibration of this distance is based on the distance from the runway head to the nose wheel
The influence of clearway CWY and stopway SWY on takeoff weight
Both can increase the takeoff weight of the aircraft, but require adjustment of V₁
Condition
A. Regardless of whether to continue takeoff or abort takeoff, it can only be carried out within the scope of the runway.
B. There is a clearway to allow the aircraft to continue taking off under greater weight conditions. In order to accommodate the aborted take-off, V₁ needs to be reduced
C. There is a stop lane that allows the aircraft to abort takeoff under heavier weight conditions. In order to continue taking off, V₁ needs to be increased.
required distance
Distance required for takeoff: TODR (Take Off Distance Required)
wet noodles
Continued takeoff distance on wet runway
On wet pavement, the distance from the brake release point to the aircraft 15ft (4.6m) above the ground Assume that the critical engine failure occurs at Vef and is identified at V₁
Distance required for takeoff from main road surface
Total take-off distance on main road surface (TODᴺ ᵈʳʸ) Full engine operation: from the brake release point to the vertical point of the aircraft 35ft (10.7m) above the ground 115% of the distance traveled
Continued takeoff distance on main road surface (TODᴺ⁻¹ ᵈʳʸ) First engine failure continues: The distance traveled from the point where the brakes are released to the vertical point where the aircraft is 35 feet above the ground Assume that the critical engine failure occurs at Vef and is identified at V₁
TODᵈʳʸ
Full hair work: TODᴺ⁻¹ ᵈʳʸ=D(from BRP to 35ft)
One round failure: 1. 15×TODᴺ ᵈʳʸ=D (from BRP to 35ft) 15%
TODᵈʳʸ≥ Max
TODᴺ⁻¹ ᵂᵉᵗ=D(from BRP to 15ft)
TOD ᵂᵉᵗ=Max
Distance required for takeoff roll: TORR (Take Off Running Required)
Dry road noodles
Full launch rolling distance on main road surface (TORᴺ ᵈʳʸ) Full engine operation: Under 115% full engine operation condition, the horizontal distance from the point where the brakes are released to the equidistant point between the departure point and the point where the aircraft reaches 35 feet above the ground
Continued takeoff roll distance on dry road surface (TODᴺ⁻¹ ᵈʳʸ) First engine failure continues: The horizontal distance from the point where the brakes are released to a point equidistant between the departure point and the point where the aircraft reaches 35 feet above the ground Assume that the critical engine failure occurs at Vef and is identified at V₁
TOR ᵈʳʸ
Full hair work: TORᴺ ᵈʳʸ=[D(from BPR to Vlof) ½D(from Vlof to 35ft)]×1. 15
Continuation after first round failure: TORᴺ⁻¹ ᵈʳʸ=D(from BPR to Vlof) ½D(from Vlof to 35ft)
TORᵈʳʸ≥Max
wet noodles
Full launch flying distance on wet track surface Full engine operation: Under 115% full engine operation conditions, the horizontal distance from the point where the brakes are released to the point equidistant from the point of departure from the aircraft to the point 35ft above the ground
Continued takeoff roll distance on wet runway First engine failure continues: the horizontal distance traveled from the time the brakes are released to when the aircraft is 15 feet above the ground. Assume that the critical engine failure occurs at Vef and is identified at V₁
TOD ᵂᵉᵗ
Full hair work: TODᴺ ᵂᵉᵗ=[D(from BPR to Vlof) ½D(from Vlof to 35ft)]×1. 15
Continuation after one shot fails: TODᴺ⁻¹ ᵂᵉᵗ=D(BPR to 15ft)
TOR ᵂᵉᵗ=Max
Distance required to accelerate to stop: ASDR (Accelerate Stop Distance Required)
Dry road noodles
The sum of the following distances (one shot fails)
i. Accelerate the aircraft from standstill to the distance covered by Vef under full engine operating conditions
ii. Assuming that the key engine fails at Vef and the pilot takes the first action to abort the takeoff at V₁, the distance covered by accelerating from Vef to the maximum possible speed during the aborted takeoff (which can be considered as V₁)
iii. The distance covered from the maximum speed defined in paragraph (ii) to the aircraft coming to a complete stop
iv. Plus the distance covered by moving at a constant V₁ speed for 2 seconds
The sum of the following distances (full hair work)
i. Under full-engine operating conditions, the maximum speed possible during accelerating the aircraft from standstill to aborted takeoff (can be considered as V₁). During this process, it is assumed that the pilot takes the first action to abort takeoff at V₁. distance
ii. The distance covered from all engine operation to the aircraft coming to a complete stop
iii. Plus the distance covered by moving at a constant V₁ speed for 2 seconds
wet noodles
Except for the road surface conditions, everything else is the same as the main road surface. The distance based on the total performance under full engine operation and first engine failure conditions are still considered.
Special Instructions
（1） The delay between Vef and V₁ is 1s
（2） ASD must be determined based on flight testing at 90% wear and laboratory testing at 100% wear.
（3） On a dry runway, reverse thrust should not be used to determine ASD
（4） For a test wet track, the acceleration and stopping distance ASDᵂᵉᵗ is the largest of the following three values:
ASDᵈʳʸ, ASDᴺ⁻¹ ᵂᵉᵗ, ASDᴺ ᵂᵉᵗ
（5） Except the runway is wet.
ASDᴺ⁻¹ ᵂᵉᵗ=ASDᴺ⁻¹ ᵈʳʸ
ASDᴺ ᵂᵉᵗ=ASDᴺ ᵈʳʸ
（6） Reverse thrust is not used to obtain evidence of ASD on a dry runway, but reverse thrust is required to obtain evidence of ASD on a wet runway, provided that the reverse thrust is safe and reliable.
Influencing factors
i. Objective factors
1. Airport elevation and temperature
2. runway longitudinal slope
3. Road condition
4. Wind direction and speed
5. aircraft weight
ii. Human Factors
1. V₁
2. flap position
3. Backward usage
4. Are the air conditioning and anti-icing turned on?
5. Whether the brake gear and brake anti-lag system are working
6. Use of spoilers (too early, too late, or at all)
In any case it should be satisfied: required distance ≤ available distance
TODR≤TODA
TORR≤TORA
ASDR≤ASDA
5. Aborted takeoff and continued takeoff
Maximum speed for aborted takeoff VstopMAX
During the takeoff acceleration roll, if the aircraft's key engine suddenly stops, the crew determines the fault and adopts standard braking procedures, which can bring the aircraft to a stop at the end of the runway or safety road.
Influencing factors
Takeoff weight↑, VstopMAX↓
Atmospheric temperature↑, VstopMAX↓
Airport pressure altitude↑, VstopMAX↓
Take off with the wind↑, VstopMAX↓
Continue takeoff minimum speed VgoMIN
If the engine stops at this speed, the pilot adopts the standard procedure to continue takeoff, which allows the aircraft to complete the minimum speed of the takeoff field stage (35ft above the ground, speed not less than V₂) on the outside of the clearway.
Influencing factors
Takeoff weight↑, VgoMIN↑
Atmospheric temperature↑, VgoMIN↑
Airport pressure altitude↑, VgoMIN↑
Take off with the wind↑, VgoMIN↑
The relationship between takeoff weight and field length weight limit
important concepts
Takeoff equilibrium distance and equilibrium speed
equilibrium speed
Recognition speed when the distance required to abort takeoff and the distance required to continue takeoff are equal
equilibrium distance
At equilibrium speed, the distance required to interrupt takeoff is equal to the distance required to continue takeoff (ASD=TOD)
As the weight of the aircraft increases, the equilibrium speed and equilibrium distance will increase.
balance track
A runway where the available distance for aborted takeoff and the available distance for continued takeoff are equal (ASDA=TODA), otherwise it is called an unbalanced runway
Typical balanced runway: a runway without clear lanes or stop lanes
balancing field method
Takeoff weight <field commander weight limit
The aircraft takes off with a small weight W₁, and the available distance for takeoff is greater than the equilibrium distance (TODA>BD)
Conclusion: When the take-off weight is less than the field length limit, V₁ is selected as an interval within which the take-off can be interrupted or continued. The smaller the weight, the larger the range
The equilibrium speed corresponding to this weight is often taken as the decision speed (V₁)
[V₁‹mcg›≤]Vgo min=V₁min≤ V₁ ≤V₁max=Vstop max (≤Vr and Vmbe)
Takeoff weight = Field length limit
The aircraft takes off at the limited weight W₂, that is, the available take-off distance is equal to the equilibrium distance (TODA=BD)
Decision speed V₁ unique
V₁ =V balance=Vgo min=Vstop max
If the decision speed V₁ happens to correspond to the field length and weight limit, no matter whether the pilot continues to take off or aborts the takeoff, the actual distance consumed reaches the available distance, and there is no margin.
unbalanced site method
Unbalanced runway: A runway where the distance available for aborted takeoff and the distance available for continued takeoff are not equal.
reason
（1） After determining the take-off speed (V₁/Vr/V₂) according to the balanced field method, if some take-off speed does not meet the requirements (such as V₁＜Vmcg, V₁＞Vmbe, V₁＞Vr, V₂＜1.1Vmca, etc.), it is necessary to It is necessary to adjust V₁ to meet the regulatory requirements for take-off speed, which will inevitably lead to the difference between the distance required to interrupt the take-off and the distance required to continue the take-off. In this case, it will cause the maximum takeoff weight of the field limit to be less than the maximum takeoff weight of the balancing field length limit.
（2） The use of clearways and safety lanes will also cause the distance required to interrupt takeoff and the distance required to continue takeoff to be different, resulting in an unbalanced runway. In this case, the maximum takeoff weight of the site limit will be greater than the balance field runway limit. The maximum takeoff weight should be larger
For runways with only clearway: TODA ≥ ASDA You can increase the maximum takeoff weight by reducing V₁
For runways with only stop lanes: TODA ≤ ASDA You can increase the maximum takeoff weight by increasing V₁
Effects of Clearway and Safety Lane on Takeoff Performance
Factors affecting rejected takeoff distance
V₁↑
Takeoff weight↑
Atmospheric temperature↑
Airport pressure altitude↑
Take off with the wind↑
Take off uphill↑
ASD↑
Factors for continued takeoff distance
Takeoff weight↑
Atmospheric temperature↑
Airport pressure altitude↑
Take off with the wind↑
Take off uphill↑
TOD↑,TOR↑
TORn and TODn remain unchanged
TORn-1 and TODn-1↓
V₁↑,
6. Factors limiting maximum takeoff weight
structural constraints
Maximum certified takeoff weight limit
The maximum weight allowed for an aircraft to take off due to design or operational limitations
Design weight limit
maximum takeoff weight
Maximum zero fuel weight
maximum landing weight
At no time can the take-off weight exceed the maximum take-off weight limited by structural strength.
Field length limit
The maximum take-off weight limited by the length of the field should be the smaller value of the maximum weight with one engine stopped and all-power take-off during the take-off roll.
When conducting airfield performance analysis, it is important to consider
TOR≤TORA
TOD≤TODA
ASD≤ASDA
Field length and weight limit table
Curved form
tabular form
The impact of clearways and stopways
If additional stop lanes are available and V₁ is increased, the field length limit takeoff weight can be increased
Because the available take-off distance TODA has not increased, V₁ must be increased Therefore a heavier aircraft traveling the same distance to achieve the same curtain height must choose a larger V₁
Since the acceleration-to-stop distance from ASDA is longer, aircraft with greater weight can terminate takeoff at greater speeds, meaning that increasing V₁ is feasible.
If there is additional clearway available and V₁ is reduced, the field length limit takeoff weight can be increased
Because the available acceleration-to-stop distance does not increase, if you want a heavier aircraft to accelerate to V₁ and then abort takeoff within the same ASDA, V₁ must be reduced
Since the take-off available distance TODA is longer, the larger take-off distance TODR corresponding to the heavier aircraft and smaller V₁ can be met.
Climb gradient limit
Climb gradient limits for takeoff path
Section IV
Section III
Section II
Section I
1.2%
1.2%
2.4%
>0.0%
twin-engine aircraft
1.5%
1.5%
2.7%
0.3%
three-engine aircraft
1.7%
1.7%
3.0%
0.5%
four-engine aircraft
Climb weight limit table
Curved form
tabular form
Obstacle restrictions
Takeoff and obstacle clearance performance
total ascent gradient
The ascent gradient calculated based on the flight performance manual accompanying the aircraft model
net ascending gradient
A safety margin is subtracted from the total ascent gradient, and the ascent gradient takes into account the gradient loss caused by pilot control errors and individual aircraft performance differences.
safety margin required by regulations
Double shot 0.8%, three shot 0.9%, four shot 1.0%
Curve climb weight limit table
difference
The gradient weight limit comes from regulations and requirements for questions in each sub-stage of the total takeoff flight path, especially the gradient requirements for the second section of the flight path. This requirement needs to be met regardless of whether there are obstacles or not
The obstacle clearance weight limit comes from the regulatory requirement that the net flight path for takeoff should be higher than the height of the obstacle apex. If there are obstacles below the takeoff flight path, the aircraft will further meet the obstacle clearance requirements in addition to meeting the gradient requirements.
tire speed limit
At high temperatures, with the same takeoff weight and ground clearance at a plateau airport, when taking off with a tailwind, the aircraft's ground lift speed increases, the tire rotation speed is fast, and the centrifugal force on the tires is large.
When the tire speed reaches a certain value, the huge centrifugal force and internal and external pressure difference will cause the tire to rupture. Therefore it is necessary to consider the tire speed limit on the maximum take-off weight
Maximum braking energy limit
The taxiing speed of the aircraft when the heat energy absorbed by the brakes reaches the limit is called the maximum braking energy limiting speed.
Check if V₁ is less than Vmbe
Vmbedecrease
high takeoff weight
High pressure height
High temperature
tailwind
V₁ increases
Use small angle flaps
Use improved climb-and-takeoff control (V₁＜Vmbe)
If V₁>Vmbe, the takeoff weight and speed should be reduced according to regulations
Energy limit table
Curved form
tabular form
Maximum landing weight programming
For shorter routes, the maximum takeoff weight of the aircraft may be limited by the maximum landing weight. Modern large aircraft consume a lot of fuel, and the maximum takeoff weight limited by the designed structural strength is much greater than the maximum landing weight. If the maximum walking weight is not considered when the aircraft takes off, , taking off with a larger takeoff weight, the weight at the landing airport may be greater than the maximum landing weight.
Minimum safe altitude limit for air route
For routes flying over mountainous areas, when the mountainous area is large and it is not suitable to set up diversion points, the maximum take-off weight of the aircraft is often limited by the minimum safe altitude of the waterway. When the aircraft is in cruising flight and one engine is stopped, the ceiling of the aircraft flying at the specified speed is reduced, which may make the aircraft's ceiling at this time lower than the height of the mountain.
7. Optimization of takeoff performance
The ultimate purpose of air operators providing transportation services to passengers is to obtain profits and create value. On the basis of ensuring take-off safety, how to further increase profits is the content of take-off performance optimization.
In actual flight, in order to give full play to the performance of the aircraft, its flight performance should be optimized according to the actual situation to improve the aircraft's transportation economy.
Optimize take-off procedures and increase take-off weight
Reasonable selection of takeoff flap angle
Lowering the high-angle flaps will cause the aircraft to leave the ground at a smaller speed.
Low ground speed and short take-off run distance
The speed off the ground is small, V₂ is small, and the ascent gradient after liftoff is small.
Adjusting the flaps will affect both the field weight limit and the climb weight limit.
The skewness is small, which is detrimental to the site length and weight limit. Good for climbing gradient weight limit and obstacle crossing
Larger skewness has the opposite effect
Engine bleed air use
When the air conditioner is turned on during takeoff, part of the gas in the engine is diverted for use in the air conditioner, causing the engine thrust to decrease, thus reducing weight loss performance.
It is recommended to temporarily turn off the air conditioner when taking off to get a shorter take-off distance.
Restrictions: Due to high cabin temperature or company policy, air cannot be bleed all the time unless an auxiliary power unit (APU) is used
Methods for optimizing takeoff performance
Increase V₂ (improves climb)
Small V₂ shortens TOD
Large V₂ increases the climb gradient
Increasing V₂ requires longer time and distance to increase speed and reduces the field length and weight limit.
Increasing V₂ causes Vlof to increase, and wheel speed restrictions need to be considered.
The remaining thrust can be increased, and the take-off weight can be increased under the same gradient conditions.
As the take-off weight increases, the resistance further increases. In order to obtain sufficient residual thrust, the speed needs to be increased based on the normal V₂ corresponding to the increased take-off weight.
In order to increase V₂, it is necessary to increase Vr at the same time
Optimization of take-off speed
Takeoff with reduced thrust
Use according to the aircraft takeoff weight and airport conditions (when ATOW ≤ MTOW)
Definition: To obtain thrust reduction by directly reducing the engine rated power
Minus rated power method
Essence: Think of the engine as a smaller power engine
Each level of thrust reduction needs to be approved
advantage
Improve operational safety
① Reduce engine load and extend engine service life
② Improve engine reliability, reduce the probability of engine failure during takeoff, and reduce the engine stall rate in the air
Increase efficiency
① Reduce the maintenance cost of maintaining the engine and reduce the cost of engine use
②Increase release reliability and passenger satisfaction
Reduce noise on both sides of the take-off profile and reduce environmental pollution
There are no operational restrictions on taking off with reduced power and thrust, and can be used under any circumstances as long as the aircraft performance permits.
Take off with reduced power and increase the runway weight limit under certain circumstances
short track noodles
Wet and contaminated pavements
The runway is shortened, causing V₁ to decrease and become limited by Vmcg. The smaller the thrust, the smaller Vmcg, and the time when V₁ is restricted by Vmcg is further delayed.
When the runway is shorter, takeoff weight increases compared to full thrust takeoff
Assumed temperature (Boeing) Flexible temperature (Airbus)
Method: Obtain thrust reduction by telling the engine a higher temperature than the actual temperature
Turbofan engine thrust characteristics
Thrust increases with temperature, first remains unchanged and then decreases
When the temperature decreases, the air density increases, the engine fuel flow increases, and the thrust increases, causing the turbine temperature and speed to increase and be restricted.
advantage
①When go-around thrust is needed, full power go-around thrust can be used
②In the continued and interrupted takeoff performance when the first engine is stopped, due to the difference between the true airspeed at the flexible temperature and the true airspeed at the actual temperature, there is an additional safety margin for the live thrust takeoff
③ Take off on a longer dry runway with a larger take-off weight
shortcoming
①Subject to some restrictions: A. To satisfy Tref＜Tflex (reference temperature of the engine＜selected flexible temperature) B. Tactual＜Tflex (actual temperature＜reference temperature of engine) C. Tref＜MAX(Tflex): The selected flexible temperature ≤ the maximum flexible temperature (the temperature corresponding to when the maximum available takeoff thrust is reduced by 25%), and the thrust reduction cannot be greater than 25% of the maximum thrust, reduce the thrust The rear throttle shall not be less than the maximum ascent throttle
②Cannot be used to pollute runways
8. contaminating the runway
Displacement resistance
Sputtering resistance
water skiing
dynamic wakeboarding
condition
The equivalent thickness of accumulated water and melted snow exceeds the tire tread depth
The plane is taxiing at a speed greater than the hydroplaning speed
May result in complete loss of braking efficiency
sticky hydroplaning
condition
Wet pavement, very smooth pavement
Airport management should burn and clean up rubber deposit areas to reduce the occurrence of this problem
Rubber reduction water skiing
During the taxiing deceleration process, if the wheel locks, the friction between the grounded part of the wheel and the ground will generate a large amount of heat. The high-temperature and high-pressure steam generated will soften and restore the rubber of the wheel, causing the wheel to slip.
9. Takeoff performance chart
MTOW
V₁/Vr/V₂
Tflex
If the two are equal, it is the equilibrium distance