Performance

What is TORA?

• It stands for Take Off Run Available
• It is the runway length available for takeoff

What is clearway?

• It is an area beyond TORA, free of obstructions (over ground or water), over which an aircraft can reach the screen height in the event of an engine failure on takeoff

Note: Not every runway has a clearway

What are the clearway limitations?

• Clearway must be less than or equal to 50% of TORA
• Clearway must be at least 152 m (500 ft) wide

What is screen height?

• It is the minimum height that an aircraft must achieve before the end of TODA in the event of an engine failure on takeoff
• For propeller aircrafts screen height is always 50 ft
• For jet aircrafts screen height is 35 ft for a dry runway and 15 ft for a wet runway

Note: Although screen height for wet runways is reduced to 15 ft, V₂ must still be achieved by 35 ft

Background info:

• The reason why screen height for jet aircrafts reduces from 35 ft to 15 ft on a wet runway is because of reduced V₁
• On a wet runway, V₁ reduces in order to allow for reduced braking capability
• This means however that in case of an engine failure at V₁, the time taken to accelerate to V_r with one-engine-inoperative would be increased, and therefore TODR would be increased
• Screen height of 15 ft compensates for the increased TODR and allows aircraft to achieve screen height within TODA

What is TODA?

• It stands for Take Off Distance Available
• It is the runway length available for takeoff plus the length of the clearway (TORA + Clearway)

What is stopway?

• It is an area beyond TORA in which an aircraft can be safely stopped in the event of a rejected takeoff

Note: Not every runway has a stopway

What is ASDA?

• It stands for Accelerate Stop Distance Available
• It is the runway length available for takeoff plus the length of the stopway (TORA + Stopway)

What is balanced V₁?

• The V₁ that results in TODR equal to ASDR is called balanced V₁
• If an engine failed just prior to V₁ the point at which the aircraft would come to a complete stop in the STOP case would be the same with the point at which the aircraft would reach the screen height in the GO case
• Balanced V₁ gives the minimum field length required for a given weight, called balanced field length. Any lower V₁ would increase TODR as it would take longer for the aircraft to accelerate to V₂ with one-engine-inoperative and any higher V₁ would increase ASDR due to higher energy absorption by the brakes
• In essence, balanced V₁ improves field length limited takeoff performance (FMC speeds are based on balanced V₁)

Note:

• Field length can be limited by either ASDR, TODR or 115% of all-engine TODR
• If an engine failed exactly at V1, you may not be able to reject the takeoff within ASDR
• This is because of minimum recognition time required between the engine failure and initiation of RTO (i.e. engine failure at V1 means that the first action to reject takeoff would be taken after V1)

What is unbalanced V₁?

• Any V₁ that results in TODR different than ASDR is called unbalanced V₁
• Unbalanced V₁ allows for higher takeoff weights by taking advantage of any runway and clearway or stopway available in excess of balanced field length
• A lower than balanced V₁ allows for higher brake energy limited weights due to lower energy absorption by the brakes, whereas a higher than balanced V₁ allows for higher obstacle and climb limited weights due to faster acceleration to V₂
• In essence, unbalanced V₁ is the optimum V₁ if you are not field length limited

What is the reason for the “80 kts” or “100 kts” (depending on the aircraft type) call during takeoff roll?

Incapacitation check

• If a pilot is incapacitated at this point, the aircraft should be considered unsafe to fly (rejecting the takeoff is considered safer than continuing) and therefore takeoff should be rejected

Airspeed crosscheck

• If CPTs and FOs speeds do not agree at this point, the aircraft should be considered unsafe to fly (rejecting the takeoff is considered safer than continuing) and therefore takeoff should be rejected

Marks the point of transition from the low speed phase to the high speed phase of the takeoff roll

• The significance of this is that the reasons to reject a takeoff differ depending if the failure happens at low speed (below 80 or 100 kt) and high speed (above 80 or 100 kt)
• There are much fewer reasons to reject a takeoff at high speed than they are at low speed

What is V₁?

• V₁ is the takeoff decision speed
• It is the maximum speed at which the pilot must take the first action to reject the takeoff and the minimum speed to continue the takeoff in the event of an engine failure
• If the pilot has not initiated the rejection of takeoff by V₁, then the Go decision has already been made

Note: This is the reason why captains remove their hand from the thrust levers immediately at the V₁ call

What is V_r?

• V_r is the takeoff rotation speed
• It allows to achieve V₂ by 35 ft above the takeoff surface in the event of an engine failure on takeoff

What is V₂?

• V₂ is the takeoff safety speed
• It is the minimum speed to be flown during the 2nd takeoff segment, that provides adequate climb performance and directional control in the event of engine failure on takeoff
• It should be achieved by 35 ft above the takeoff surface

Note: V₂ is flown during engine-out operations and not during normal operations. During normal operations initial climb speed is usually V₂+10 or V₂+20 depending on aircraft type

Background info:

• V₂ is the minimum speed to be flown in case of EFATO (Engine Failure After Take Off) and not always the target speed
• Flight directors will command pitch attitudes that result in V₂ or speed at which the engine failure happened, whichever is higher (usually limited to V₂+20 or V₂+15 depending on aircraft type)

What is V_mcg?

• It is the minimum control speed on the ground (IAS and not ground speed)
• At or above this speed, it would be possible to continue the takeoff and maintain directional control using the rudder only (i.e. no nose wheel steering) if the critical engine failed during takeoff
• This is why V₁ must always be equal or greater than V_mcg

Note:

• V speeds always refer to IAS and not TAS or Groundspeed
• The reason is because the aerodynamic performance of the aircraft (e.g. rudder effectiveness) is related to the kinetic energy of airflow (dynamic pressure) from which IAS is calculated, and not the True Airspeed of the aircraft or its speed over the ground

Background info:

• V_mcg  allows for 30 ft deviation from centerline
• V_mcg is calculated based on 0 crosswind
• This is the reason why the upwind engine of a twin-engine jet aircraft is not considered critical engine (see more information on chapter Aircraft General Knowledge)

What would be the implications of an engine failure at V_mcg when taking off with crosswind?

Failure of upwind engine will result in worse handling characteristics. Let’s see why:

• During takeoff roll (jet aircraft), if crosswind is from the right, we are going to need opposite (left) rudder to maintain centerline and aileron into the wind (right) as required to keep the wings level
• If engine no2 fails during takeoff roll (right engine), we are going to need even more left rudder to maintain directional control and V_mcg does not account for that
• Therefore, failure of the upwind engine during takeoff roll will result in worse handling characteristics than V_mcg accounts for

What is V_mca?

• It is the minimum control speed in the air
• At this speed, full rudder deflection would be necessary to maintain wings level in the event of failure of the critical engine (using only the primary flight controls)

[New] What is the relationship between V_mca and V_r?

• V_r must always be greater than V_mca (V_r greater than or equal to 1.05 V_mca )

What is the relationship between V_mcg and V₁?

• V_mcg must always be less than or equal to V₁

What is the relationship between V₁ and V_r?

• V₁ must always be less than or equal to V_r

What is the relationship between V_mca and V₂?

• V_mca must always be less than V₂ (1.1 x V_mca less than or equal to V₂)
• The difference between these speeds, is that V₂ provides adequate climb performance in the event of an engine failure

How does V₁ change on a non-dry runway?

• It decreases in order to allow for reduced braking capability on a non-dry runway

How do takeoff speeds vary with weight?

• The heavier the aircraft the higher the takeoff speeds
• This is because as weight of the aircraft increases, a greater amount of lift is required in order to get the aircraft airborne, which is achieved by increasing the takeoff speeds

Why does V₁ increase with increasing weight?

• Higher weight means higher lift required for the aircraft to get airborne which means higher V_r
• As V_r increases, V₁ needs to be increased as well
• This is because if V₁ did not increase, it would increase the time needed to accelerate to V_r with one-engine-inoperative should an engine failure occurred at V₁

Note:

• If field length limited, it is important to understand that field length is limited by both ASD and TOD, and although a lower V₁ would reduce ASD, it would increase TOD
• The V₁ that minimizes the field length required for takeoff is the balanced V₁ (i.e. ASD = TOD) which increases with increasing weight

How do takeoff speeds vary with flap settings?

• The higher the flap settings the lower the takeoff speeds
• This is because higher flap settings increase S (wing surface area) and Cl (coefficient of lift) of the wing, which results in lower takeoff speeds required in order to generate the same amount of lift

How does fuel burn vary with flap settings?

• The higher the takeoff or landing flap settings the higher the fuel burn
• This is due to increased drag

How would you configure for a field length limited takeoff?

• Use higher flap settings because they would result in reduced takeoff speeds
• By lowering the V₁ you increase the remaining field length available in the STOP case
• By lowering the V_r and V₂ you can liftoff and achieve V₂ and screen height faster in the GO case

How would you configure for a climb or obstacle limited takeoff?

• Use lower flap settings because they would result in less drag and an increased V₂ which in turn leads to better climb performance

Note: In case of Obstacle limited TOW, acceleration height is increased to extend the second takeoff segment

What are the four takeoff segments in the event of an engine failure?

• Segment 1: starts from screen height and ends when gear is fully retracted
• Segment 2: starts from gear retraction and ends at acceleration height (which cannot be less than 400 ft AAL). Minimum climb gradient for the 2nd segment is 2.4% for twin-engine aircrafts and minimum speed to be maintained is V₂
• Segment 3: starts from acceleration height and ends when flaps are fully retracted
• Segment 4: starts from flaps up and ends when the aircraft reaches the MSA

Note: The four takeoff segments refer only to engine-out operations and not to normal operations

What is assumed (or flex for Airbus) temperature?

• It is a method of calculating our takeoff performance based on a higher temperature than the actual one (assuming a higher temperature)
• Flat rated jet engines are designed to produce constant (flat) thrust up to a certain temperature set by the manufacturer
• Above this temperature, takeoff thrust is going to be reduced
• Assumed temperature results in reduced thrust for takeoff which increases engine’s life and reduces maintenance costs
• Reduced thrust will also result in higher TORR (i.e. longer ground roll required for takeoff)

Background info:

• There is a common misconception that assumed (or flex) temperature results in reduced fuel burn due to less thrust being used, but that’s not the case. In fact, the opposite is true
• The reason why assumed temperature results in increased fuel burn, is because as less thrust is used for takeoff and climb, it will take longer for the aircraft to reach its optimum altitude
• This means that it will spend more time at lower altitudes and less time at its optimum altitude, where it is most efficient
• Reduced maintenance costs however outweigh the increased fuel burn

What is V_x?

• It is the maximum angle of climb speed
• You would use this speed to gain altitude in the shortest distance (e.g. clear an obstacle)

Background info:

• For jet aircrafts, V_x is equal to the minimum drag speed

What is V_y?

• It is the maximum rate of climb speed (it is higher than V_x)
• You would use this speed to gain altitude in the shortest time (e.g. if ATC instructs you to expedite your climb)

What is the difference between VMO and MMO?

• VMO is the aircraft’s maximum operating speed
• MMO is the aircraft’s maximum operating Mach number
• At lower altitudes the aircraft is limited by IAS (VMO) whereas at higher altitudes it is limited by Mach number (MMO)
• For example, Boeing 737NG has a VMO of 340 kts and MMO of 0.82
• Up to approximately 26000 ft which is called the crossover altitude, the aircraft is limited by 340 kts IAS
• Above this altitude Mach 0.82 would be more restrictive

What is VNE?

• It is the never exceed speed for propeller aircrafts

What is VNO?

• It is the maximum normal operating speed for propeller aircrafts

[New] What is V_mcl?

• V_mcl is the minimum control speed for approach and landing
• At this speed, full rudder deflection would be necessary to maintain wings level in the event of failure of the critical engine and with the operative engine set at go around thrust

[New] What is V_ref?

• V_ref is the landing reference speed
• It is equal to 1.3 x stalling speed in landing configuration (V_s0)

Note:

• V_ref is always greater than or equal to V_mcl
• This ensures adequate aircraft directional control in the event that the critical engine fails on final approach leading to go around

[New] Why is it important to be accurate with your speed during approach?

• Landing at a speed higher than the calculated touchdown speed will increase the landing distance (10% higher speed will increase landing distance by approximately 20%)
• Flying below V_ref brings the speed closer to V_s0 (stalling speed in landing configuration). It also reduces safety margins in the event of an engine failure requiring a go around as V_ref is always greater than or equal to V_mcl and ensures adequate directional control

How do flap settings affect landing distance?

• Higher flap settings decrease landing distance due to more drag and lower approach speeds

[New] If you need to land with flaps up due to a flap malfunction, how will this affect landing distance required?

• Higher landing distance will be required due to higher touchdown speed and less drag

How does the ground effect affect landing distance?

• It increases the landing distance due to increased lift and reduced drag due to runway surface blocking the wing tip vortices left behind the wings

How does weight, pressure altitude, temperature, wind and pressure affect takeoff and landing performance?

Weight:

• Increased weight reduces takeoff and landing performance (due to higher speeds)

Pressure altitude:

• Higher pressure altitudes reduce takeoff and landing performance (due to decreased air density and reduced thrust available – same IAS but higher TAS)

Temperature:

• Increased temperature reduces takeoff and landing performance (due to decreased air density)

Wind:

• Headwind improves takeoff and landing performance (due to lower groundspeed)

Pressure:

• Higher pressure improves takeoff and landing performance (due to higher air density)

What is the effect of headwind on takeoff performance?

• Headwind reduces aircraft’s ground speed and therefore it is capable of achieving liftoff faster, using less runway for its ground run
• For example, if V_r is 140 kts and headwind is 30 kts, the ground speed at which rotation will be initiated will be 110 kts

What is the effect of headwind on landing performance?

• Headwind decreases aircraft’s ground speed and therefore will touchdown at a lower ground speed
• This decreases the kinetic energy the brakes need to absorb in order to stop the aircraft and therefore decreases the landing distance

Note: Kinetic energy varies proportionally with the square of the aircraft’s speed (kinetic energy=1/2 x m x V²). This means that a 10% higher airspeed on touchdown would lead to 21% higher kinetic energy for the brakes to absorb. This emphasizes the importance of landing at the correct speed, especially on short fields.

[New] What percentage of the headwind and tailwind component are takeoff and landing performance calculations based on?

• 50% of headwind component and 150% of tailwind component

What are the three types of energy that pilots have to manage during the flight?

• Kinetic energy (speed)
• Potential energy (altitude)
• Chemical energy (fuel)

• Kinetic energy: The higher the speed, the higher the aircraft’s kinetic energy. Kinetic energy can only be converted to potential energy (e.g. during terrain escape maneuver, we pitch up to change airspeed for altitude)
• Potential energy: The higher the altitude, the higher the aircraft’s potential energy. Potential energy can only be converted to kinetic energy (e.g. if high on profile, we change altitude for airspeed to regain the path)
• Chemical energy: Fuel in the tanks lets the engines produce thrust. We can use thrust to convert it to potential or kinetic energy (speed or altitude)

Hoes does runway slope affect takeoff and landing performance?

• A positive runway slope will reduce aircraft’s acceleration on takeoff (reduces takeoff performance) and increase aircraft’s deceleration on landing (improves landing performance)
• The opposite is true for a negative runway slope

Background info:

• Runway slope is calculated by calculating the difference between the elevation of the two thresholds of the runway (ft) and then dividing this difference by the runway length (ft)
• For example if threshold elevation for RW 15 is 500 ft and RW 33 is 350 ft, that gives us a difference of 150 ft
• If runway length is 7500 ft, that gives us a runway slope of +2% for RW 33 and -2% for RW 15 (150/7500=2%)
• This means that for every 100 ft of the runway, runway height increases by an average of 2 ft

What is hydroplaning speed and how is it calculated?

• Hydroplaning speed is the minimum groundspeed at or above which the aircraft will start hydroplaning (wheels start skidding and brakes lose effectiveness)
• Hydroplaning speed depends solely on the tire pressure of the wheels (hydroplaning speed=9 x square root of tire pressure)
• The higher the tire pressure the higher the hydroplaning speed

Note:

• Hydroplaning speed is the minimum groundspeed at or above which the aircraft will start hydroplaning. If hydroplaning has started, then it can continue at speeds much lower than the hydroplaning speed
• Hydroplaning can occur even on wet runways (i.e. less than or equal to 3 mm of water)

Background info:

• To protect against hydroplaning, aircrafts are fitted with anti skid system which, as its name implies, prevents against skidding of the wheels
• The way it does that, is by releasing pressure to the skidding wheels until they start rotating again
• Once they start rotating, then brake pressure is applied again
• This results in optimum braking

What is the 3 Kelvin spread rule?

• If temperature is 3° C or less and dew point spread (i.e. difference between temperature and dew point) is 3° C or less, the runway may be more slippery than anticipated
• It is a rule of thumb used to anticipate worse runway conditions than reported by ATIS/ATC during winter operations

Up until what point can you execute a go-around?

• Up until selecting reverse thrust
• Once reverse thrust has been selected, you are committed to land

Background info:

A go-around executed below minimums is called a rejected landing if initiated prior to touchdown or a balked landing if initiated after touchdown

How do you convert wind speed in m/s into kts?

• As a rule of thumb, knots are approximately double the m/s (e.g. 5 m/s is 10 kts)

What vertical speed do you need to maintain a 3° glide path with groundspeed 150 kts?

• 750 ft / min (required vertical speed is approximately half the ground speed x 10, for 3° glide path)

If wind is coming from the left on takeoff, what rudder do you use?

• Right rudder (opposite rudder in order to maintain centerline and aileron into the wind to keep the wings level)

What is the crosswind component if you are taking off on runway 03 with wind 010/20 kts?

• As a rule of thumb, you take the difference of the wind direction with the runway, add 0.2 and multiply it by the wind speed
• For this example the crosswind component would be 0.3-0.1=0.2+0.2=0.4×20=8 kts

What is the crosswind component if you are taking off on runway 03 with wind 060/20 kts?

• By using the abovementioned rule of thumb, the crosswind component for this example would be 0.6-0.3=0.3+0.2=0.5×20=10 kts