71: OVERSPEED PREVENTION AND RECOVERY

Question 1

During normal operations, the aircraft may temporarily exceed VMO/MMO due to following possible causes:

Answer 1

• Environmental factors like wind gradients, turbulence, wake turbulence etc
• Maintaining speed above ECON
• Managed DES in case of commencing descent after the FMGS computed TOD
• Managed DES with winds not entered in FMGS for cruise & descent

Question 2

OVERSPEED PREVENTION TECHNIQUES
The overspeed prevention technique should be used if significant speed variations are encountered close to VMO/MMO during the flight.

Answer 2

1. Keep the AP and A/THR engaged.
2. Decrease the Speed Target / Select lower
   speed, to increase margin to VMO/MMO, if
   needed (not below green dot)
3. Monitor speed trend. (trend arrow on the PFD)
4. Use speed brakes as needed with due
   monitoring.

Question 3

OVERSPEED RECOVERY TECHNIQUES
Apply the overspeed recovery technique if the aircraft exceeds VMO/MMO.

Answer 3

1. Keep the AP engaged (in order to minimize the
   vertical load factors).
2. Extend Speed Brakes to the most appropriate lever
   position, depending on the overspeed situation.
3. In addition, keep A/THR engaged and CHECK that
   the thrust reduces to idle.
4. If the A/THR is OFF, set the Thrust Levers to idle.
5. Once the speed is below VMO/MMO with a
   sufficient margin, retract the speed brakes and
   select a suitable speed target. Ensure A/THR is
   engaged and recover flight path smoothly.

Question 4

ACTIONS IF THE HIGH SPEED PROTECTION ACTIVATES AND DISCONNECTS THE AUTOPILOT:
The autopilot may automatically disconnect due to the activation of the HSP. This usually happens only in the case of severe/prolonged VMO/MMO exceedance. When the Mach or speed decreases close to VMO/MMO, the HSP protection deactivates, the aircraft remaining in manual flight mode.

Answer 4

1. The flight crew can smoothly adjust the pitch attitude but without overreacting, especially at high altitude.
2. Flight crew should keep speed brakes extended because they are compatible with HSP.

Question 5

Learning from In service events:
A recent analysis by Airbus showed that the handling of overspeed was not always done in accordance with the recommended techniques provided in the Flight Crew Techniques Manual (FCTM). On flights with a V MAX exceed, the following flight crew errors were highlighted:

Answer 5

• Numerous manual autopilot disconnections
• No reduction of speed target
• No use of speedbrakes