1 / 20

Which of the following speed limits are applicable for transport category (CS-25) aircraft: VMO, VNE, MMO, VNO?

  • A

    VMO and VNO

  • B

    VNE and VNO

  • C

    VNO and MMO

  • D

    VMO and MMO

Refer to figure.
The speeds referred to in the question are different operational speed limits applicable to aircraft certified under CS-23 and CS-25. These speed limits are based upon design speed limits defined during the certification process. The relevant design speed limits are:

VC - The design cruising speed - the maximum cruising speed. The aircraft is certified to fly at this speed even at the limits of the acceleration range for the particular aircraft category, positive and negative. Above VC, the aircraft structure may be damaged even if operating within the certified acceleration range (e.g. -1.0 g to 2.5 g for CS-25).

VD - The design dive speed - this is the maximum speed for which the aircraft is certified. Flight above this speed may lead to structural failure, and flutter of aircraft surfaces may be experienced. VC must not be more than 80% of VD. The aircraft may not be certified to fly within the entire acceleration envelope at VD (for CAT aircraft certified under CS-25, VD is only tested from 0 g to 2.5 g).

Operational speed limits are then defined for CS-23 or CS-25 aircraft as follows:

CS-23

VNO - The maximum structural cruise speed - This speed must not be greater than VC. It is shown to the pilot on the ASI as the beginning of the yellow arc, where the green arc ends. It must also be less than 89% of VNE

VNE - The "never exceed" speed - Equal to 90% of VD, to allow a safety margin below the maximum speed for which the airframe has actually been tested at (VD). This margin is small however, so the pilot must never exceed VNE, hence its apt name. On an ASI, VNE is denoted by a red line at the end of the yellow speed range.

CS-25

VMO- The maximum operating speed - Must not be greater than VC. Unlike VNO, this speed must not be intentionally exceeded at any stage throughout the flight. Expressed as an EAS.

MMO- The maximum operating Mach number - At high altitude as Mach number increases, MMO becomes the limiting speed, expressed as a Mach number. Above this speed, high speed buffeting may be experienced.

So the relevant speed limits for transport category aircraft are VMO and MMO.

Your Notes (not visible to others)



This question has appeared on the real examination, you can find the related countries below.

  • Austro Control
    2
  • Czech Republic
    1
  • Portugal
    1