Performance & Structural Requirements

Performance and structural requirements.


  • IAS = Indicated Airspeed = airspeed indicator reading.
  • CAS = Calibrated Airspeed = IAS corrected for static position error.
  • EAS = Equivalent Airspeed = CAS corrected for compressibility error.
  • TAS = True Airspeed = EAS corrected for OAT and pressure altitude.
  • GS = Ground Speed = TAS corrected for wind component.
  • M = Mach number = relationship between TAS and speed of sound.


Thrust Setting

  • EPR = Engine Pressure Ratio.
  • FF = Fuel Flow.
  • MCT = Max Continuous Thrust.
  • RPM= Revolutions Per Minute.
  • OAT = Outside Air Temperature.
  • RAT = Ram Air Temperature = TAT.
  • SAT = Static Air Temperature = OAT.
  • TAT = Total Air Temperature = RAT.


  • BA = Braking Action.
  • CG = Center of Gravity.
  • µ = friction coefficient.
  • FL = Flight Level.
  • GWC = Gross Weight Chart.
  • RC = Rate of Climb.
  • RTO = Rejected Takeoff.
  • RWY = runway.
  • SL = Sea Level.
  • T/O = TKOF = takeoff.
  • TODC = Takeoff Data Computer.

Characteristic speeds

V1 = Decision speed is the speed at which, for the purpose of determining the required takeoff runway length, engine failure is assumed to be recognized and the rejected takeoff initiated. The reaction time used in the calculation is about 1 second. Thus for calculation of the required runway length, the engine failure is assumed to occur 1 s before V1. The total time for pilot actions , until full brakes are applied, is the time demonstrated during certification plus two seconds (typically 3-4 seconds).

At V1 it should be possible to either:

  1. Reject the takeoff and stop at the end of the runway.
  2. Continue the takeoff and reach 35 ft at V2 speed at the end of the runway.

VR = Rotation speed is the speed at which, for the purpose of determining required takeoff runway length, rotation of the aircraft is initiated.

VR must be determined not to be less than:

  • V1.
  • 1.05 times the minimum control speed, airborne.
  • A speed which permits the attainment of V2 prior to reaching 35 ft height at the end of the takeoff distance.
  • In upper limit for VR is set to max tire speed.

V2 = Takeoff safety speed is the speed used to determining the performance during the initial climbout. In these calculations, V2 should be reached prior to attaining a height of 35 ft above the runway surface.

Thus V2 is used in determining:

  • The required takeoff distance, prior to the end of which it should be attained.
  • The climb requirements limitations.
  • The obstacle clearance limitations.

V2 shall not be less than:

  • 1.1 times VMCA.
  • 1.2 times VS.


  • VFl up and VSl in are minimum speeds for retraction of FLAPS and SLATS after takeoff.
  • VClean is the speed to be used in the final segment of a takeoff with engine failure, i.e with “CLEAN” aircraft (after flap/slat retraction).
  • VP = Pattern speed is “maneuvering speeds” and gives better margin to stall. Used in low level holdings, procedure and circuits.
  • VP clean “PATTERN CLEAN”, normally the lowest speed with all engines running.
  • VMO Max operating IAS, limited by structural requirements.
  • MMO Max operating Mach, limited by high speed aerodynamics.

Rough Air Speed is the speed which should be used in connection with severe turbulence.

VHOLD Speed to be used during holdings. Below FL 250 the same as VP clean. FL 250-290 VP clean + 10 kt. Above FL 290 VP clean + 20 kt.

Vref is reference speed used to derive other speeds for different phases of flight by adding of fixed increments. The amount to be added are stated in the respective aircraft operating manual. When Vref is used without additional flap suffix, it is based on the full landing configuration. Occasionally it is necessary to use Vref based on other flap setting. In such cases the configuration is always indicated as a suffix (Vref 20).

Landing runway length requirements are based on Vref at 50 ft over the runway threshold.

VTH For aircraft not using Vref, landing runway length requirements are based on VTH at 50 ft over the runway threshold.

Weight Terms

BW = Basic Weight. Basic empty weight, including:

  • aircraft structure.
  • systems.
  • engines.
  • unremovable equipment.
  • unusable liquids (fuel, oil and others).
  • standard loose equipment.
  • DOW = Dry Operating Weight. Operational empty weight. Basic weight plus operational items such as crew and pantry (equipment, food, beverages).
  • LW = Landing Weight. Takeoff weight minus trip fuel.
  • MLW = Maximum Landing Weight. Weight limitation for landing, governed by structural and/or operational requirements.
  • MTOW = Maximum TakeOff Weight. Weight limitation for takeoff (brake release), governed by structural and/or operational requirements.
  • MZFW = Maximum Zero Fuel Weight. Structural weight limitation.
  • RW = Ramp Weight. Takeoff weight plus taxi fuel, i. e. weight of loaded aircraft before starting the engines.
  • TOW = Takeoff Weight. Gross weight of aircraft at brake release for takeoff, i.e. actual zero fuel weight plus takeoff fuel.
  • ZFW = Zero Fuel Weight. Dry operating weight plus total traffic load.

Fuel Terms
Ballast fuel. Non-usable fuel used for balancing purpose (only possible on some aircraft). The ballast fuel is separated from takeoff fuel (usable fuel) and loaded ia a separate tank. the fuel must not be consumed or jettisoned during flight.

Block fuel. Weight of total amount of fuel on board before starting taxi.

Burn-off fuel. Taxi fuel plus trip fuel.

Reserve fuel. Difference between takeoff fuel and trip fuel, consiting of:

  1. Route reserve
  2. diversion
  3. holding, and
  4. additional fuel

Taxi fuel. Weight of fuel to cover APU consumption, engine start and ground maneuvers until start of takeoff. Standard weights are used which are, with a few exceptions, applicable at every airport.

TOF = TakeOff Fuel. Weight of total usable fuel onboard at the moment of takeoff (brake release).

Trip fuel. Weight of the precalculated fuel consumption from takeoff to touchdown at the next point of landing.

Load Terms

Allowed traffic load. The weight remaining after the subtraction of the operating weight from the allowed takeoff weight.

Deadload. Total weight of:

  1. baggage
  2. cargo
  3. mail

Total traffic load (total payload). Total weight of:

  1. passengers
  2. baggage
  3. cargo
  4. mail

Balance Terms

  • BI = Basic Index. Center of gravity at basic weight (BW) expressed as an index value.
  • CG = Center of Gravity. Point about which an aircraft would be balanced if suspended.
  • DOI = Dry Operating Index. Center of gravity at dry operating weight expressed as an index value. Basic index (BI) corrected for the balance influence of the loads included in dry operating weight (DOW).
  • DLI = Dead Load Index. Dry operating index (DOI) corrected for the balance influence of the load in compartments.
  • LIZFW = Loaded Index at Zero fuel weight. Deadload index (DLI) corrected for the influence of passengers in cabin (fuel not included).
  • MAC = Mean Aerodynamic Chord. Imaginary reference line (chord) dividing the wing areas producing the same amount of lift. Location of CG of loaded aircraft is given as a percentage of the MAC.

Keep the spirit!

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