The document discusses speeds that are important for takeoff performance of JAR 25 aircraft. It defines key speeds such as stall speed, minimum control speeds on the ground and in the air, engine failure speed, minimum unstick speed, lift-off speed, maximum tire speed, and maximum brake energy absorption speed. It also discusses operative speeds used for takeoff including decision speed (V1), rotation speed (VR), and takeoff safety speed (V2). Factors that can affect takeoff performance and speeds are also summarized such as flap setting, runway slope, wind, density altitude, aircraft systems, and runway contamination.

1. 1. SPEEDS
Performance JAR 25

2. SPEEDS
 JAR 25 aeroplanes
 Factors affecting takeoff
 Speeds
• Vs : stall speed
• Vmcg : minimum control speed on the ground
• Vmca : minimum control speed airborne
• Vef : critical engine failure speed
• Vmu : minimum unstick speed
• Vlof : lift off speed
• Vmaxtire : maximum tire speed
• Vmbe : maximum brake energy absorption speed
 Operative speeds: V1 – Vr – V2

3. JAR 25 AEROPLANES
Performance Class A aeroplanes (certified under FAR/JAR 25):
• All multi-engine turbojet powered aeroplanes.
• Multi-engine turboprops with a seating configuration of more
than 9 seats, or a MTOW > 5700 Kg.

4. FACTORS AFFECTING TAKEOFF
Factors affecting takeoff performance are those affecting one or more
of the forces involved in this phase of flight :
Lift
Weight
Drag Thrust
Fr

5. FACTORS AFFECTING TAKEOFF
Those factors are:
 Flap setting
 Runway slope
 Wind
 Density altitude
 Aircraft systems
 Runway contamination

6. FACTORS AFFECTING TAKEOFF
Acceleration distance with flaps 0º
Acceleration distance with flaps 15º
CL effect
CD effect
FLAP SETTING

7. FACTORS AFFECTING TAKEOFF
RUNWAY SLOPE AND WIND
Runway slope and wind affect takeoff distances and speeds.
Therefore, the pilot sometimes has to calculate what is known as
“corrected runway length”, and then use that value in other graphs.

8. FACTORS AFFECTING TAKEOFF
DENSITY ALTITUDE
Density altitude has a considerable influence on takeoff distances and
speeds, since TAS values and engines performance depend on it.
DA effects will be discussed later on.
AIRCRAFT SYSTEMS
Engine bleed may reduce thrust available in about 10%. This will
clearly affect takeoff performance. Other circumstances such as anti-
skid inoperative may affect also.

9. FACTORS AFFECTING TAKEOFF
RUNWAY CONTAMINATION
A contaminated runway can dramatically affect takeoff performances.
Specific calculations of speeds and distances have to be done before
taking off from a contaminated runway.
Under certain circumstances operation of the aircraft may be
forbidden.

10. SPEEDS
 JAR 25 aeroplanes
 Factors affecting takeoff
 Speeds
• Vs : stall speed
• Vmcg : minimum control speed on the ground
• Vmca : minimum control speed airborne
• Vef : critical engine failure speed
• Vmu : minimum unstick speed
• Vlof : lift off speed
• Vmaxtire : maximum tire speed
• Vmbe : maximum brake energy absorption speed
 Operative speeds: V1 – Vr – V2

11. SPEEDS
STALL SPEED (Vs)
Defined as minimum steady flight speed at which the aircraft is
controllable, with null thrust and the centre of gravity at the forward
limit, or the 94% of the Vs1g determined in the same conditions,
whichever is greater.
ONE-G STALL SPEED (Vs1g)
Minimum calibrated airspeed at which the aeroplane can develop a lift
force (normal to the flight path) equal to its weight, whilst at an angle
of attack non greater than that at which the stall is identified.
 Vs1g is always greater than Vs (about a 6%).

12. SPEEDS
MINIMUM CONTROL SPEED ON THE GROUND (Vmcg)
After an engine failure, Vmcg is the minimum speed during takeoff at
which it is possible to maintain directional control with only the use of
primary aerodynamic controls, to enable the takeoff to be safely
continued, assuming:
• Takeoff configuration
• Critical engine failure
• Remaining engines at takeoff thrust
• MTOW and CG at the most unfavourable position (aft limit)
The maximum demonstrated separation from the runway centreline will
be no more than 30 ft, and the rudder forces may not exceed 150 lb.

13. SPEEDS
Max
30 ft
Engine failure
MINIMUM CONTROL SPEED ON THE GROUND (Vmcg)

14. SPEEDS
MINIMUM CONTROL SPEED AIRBORNE (Vmca)
Minimum flight speed at which the aeroplane can be directionally
controlled with engine failure, without loss of altitude, assuming:
• Critical engine inoperative
• Remaining engines at takeoff thrust
• MTOW and CG at the most unfavourable position (aft limit)
• Takeoff configuration and trim setting
• Landing gear up
• Maximum bank angle 5º towards the operative engine
• No ground effect
• Maximum force on rudder pedals is also 150 lbs (20 lbs for
continuous use)

15. SPEEDS
ENGINE FAILURE SPEED (Vef)
Vef is the calibrated airspeed at which the critical engine is assumed to
fail. Vef must be selected by the applicant, but may not be less than
Vmcg.”
All takeoff performance figures after critical engine failure are
calculated from this speed.

16. SPEEDS
MINIMUM UNSTICK SPEED (Vmu)
Vmu is the minimum speed at which the aircraft can safely lift-off and
continue the takeoff without undue hazard.
Ground effect is not considered.

17. SPEEDS
Minimum unstick takeoff test

18. SPEEDS
LIFT-OFF SPEED (Vlof)
Vlof is the calibrated airspeed at which the aeroplane becomes airborne,
if rotated at VR.
 It depends on the MTOW, flap setting and angle of attack.
 Vlof and Vmu do not appear in the flight manuals
1.05 Vmu < Vlof (1 ENG OUT)
1.10 Vmu < Vlof (all engines)

19. SPEEDS
MAXIMUM TIRE SPEED (Vmaxtire)
Vmaxtire is the maximum speed that the tires can support.
The tire manufacturer specifies the maximum ground speed that can be
reached, in order to limit the centrifugal forces and the heat elevation
that may damage the tire structure.
For almost all Airbus aircraft models, Vmaxtire is equal to 195 knots
(Ground Speed).
 Take into account that Vmaxtire may limit takeoff weight.

20. SPEEDS

21. SPEEDS
MAXIMUM BRAKE ENERGY SPEED (Vmbe)
Vmbe is the maximum speed on the ground from which a stop can be
accomplished within the energy capabilities of the brakes.
JAR/FAR 25.109(h): A flight test demonstration of the maximum brake
kinetic energy accelerate-stop distance must be conducted with no
more than 10% of the allowable brake wear range remaining on each of
the aeroplane wheel brakes.
 Vmbe depends on ATOW, DA, wind, runway slope, and the brakes
temperature at the beginning of the takeoff run.

22. SPEEDS
 JAR 25 aeroplanes
 Factors affecting takeoff
 Speeds
• Vs : stall speed
• Vmcg : minimum control speed on the ground
• Vmca : minimum control speed airborne
• Vef : critical engine failure speed
• Vmu : minimum unstick speed
• Vlof : lift off speed
• Vmaxtire : maximum tire speed
• Vmbe : maximum brake energy absorption speed
 Operative speeds: V1 – Vr – V2

23. SPEEDS
OPERATIVE SPEEDS
V1: Decision speed
VR: Rotation speed
V2: Takeoff safety speed

24. SPEEDS
DECISION SPEED (V1)
The decision speed V1 is the calibrated airspeed on the ground at
which, as a result of engine failure or other reasons, the pilot is
assumed to have made a decision to continue or discontinue the
takeoff.
V1 is the speed at which, if a failure is recognised, the distance to bring
the aeroplane to a full stop without the aid of the reverse thrust will not
exceed the accelerate-stop distance available (ASDA); or, if takeoff is
continued, the distance to a height of 35 ft will not exceed the usable
takeoff distance (TODA).
V1
Abort takeoff Continue takeoff

25. SPEEDS
35 ft
Stop
V1Vef
V1Vef
Recognition
time = 1s
Recognition
time = 1s

26. SPEEDS
B737 PFD

27. SPEEDS
V1 CONSIDERATIONS
• V1 lower limit is Vmcg (+ speed gain in recognition time).
• V1 higher limit is Vmbe.
• V1 =< VR
These factors will increase V1:
 More weight
 Higher DA
 Positive runway slope
 Headwind
 Engine anti-ice
 Lower flap settings

28. SPEEDS
ROTATION SPEED (VR)
The rotation speed VR is the speed at which rotation must be initiated in
order to attain V2 not later than at 35 ft with one engine inoperative.
The assumed rate of rotation is 3º per second.
Remember also that rotating too late or too early will increase the
takeoff run.

29. SPEEDS
TAKEOFF CLIMB SPEED (V2)
The takeoff climb speed V2 is the speed that will allow the initial climb
to be continued with a safe margin to stall and to Vmca with the critical
engine failed.
 Remember that it must be reached not later than at 35 ft.
 V2 >= 1.1 Vmca
 V2 >= 1.2 Vs
 V2 >= 1.3 Vs1

30. SPEEDS