busav8r
6th May 2013, 10:36
It was recently introduced by the Airbus a "new" A320F QRH procedure for Overspeed Recovery. I don't see any problems with this "new" procedure except that I have many doubts when I think about a possible scenario of a Mmo exceedance in some particular conditions (hi GW and operating close to the max ceiling).
Everyone knows “Jacques from Airbus” built the Airbus such that it does not stall and it does not overspeed until a certain point (even tough we must remember we are in the threshold of the operating window and things happen much in line with the unsinkable Titanic).
Although it is not operationally authorized to fly deliberately outside the normal flight envelope, it is not unsafe (in isolation) and it may happen (strong head gust or engines commanded at full power in level flight and pilot momentarily not in monitor/control of the speed/trajectory). In such extreme cases the high speed protection may be activated (threshold is Mmo plus a margin less a phase advance) and the protection may command a nose-up load factor until the speed is back below Mmo.
So why such a blind procedure as Speed Brakes Lever... FULL in case of a Mmo exceedance? Why the urgency to use the SBs?
Let's imagine the following scenario: you are dodging thunderstorms and you get yourself in a situation when you encounter some solid turbulence. At this point your airspeed begins to fluctuate and your margins are now small. The flight controls becomes less effective. The engines will be “sucking wind” and the aircraft begins to wallow in the sky. Suddenly you enter Mmo and you blindly apply the QRH: Speed Brakes... Full.
Can anyone imagine what may happen next?! Not a nice feeling.
Any clever thoughts about this subject would be most welcome. Thanks.
As soon as the speed exceeds VMO/MMO, apply the following actions:
AP : KEEP ON
SPEED BRAKES LEVER....................................................... .................................... FULL
THRUST REDUCTION................................................... .............................................MONITOR
If the A/THR is OFF:
ALL THR LEVERS...................................................... .............................................IDLE
If the AP automatically disengages:
HIGH SPEED PROTECTION : ACTIVE IN NORM LAW
The activation of the high speed protection results in an automatic pitch up
in order to reduce the speed.
While the speed is above VMO/MMO:
SPEED BRAKES LEVER : KEEP FULL
PITCH ATT......................................................... ADJUST SMOOTHLY AS RQRD
When the speed is below VMO/MMO with a sufficient margin to VMO/MMO:
SPEED BRAKES...................................................... .............................................AS RQRD
If the A/THR is OFF:
ALL THR LEVERS...................................................... ...................................... MAN ADJUST
If the AP is OFF:
FLIGHT PATH........................................................ ..................................... RECOVER SMOOTHLY
In the case of severe turbulence:
Refer to PRO-SUP-91-10 Adverse Weather - Severe Turbulence
Everyone knows “Jacques from Airbus” built the Airbus such that it does not stall and it does not overspeed until a certain point (even tough we must remember we are in the threshold of the operating window and things happen much in line with the unsinkable Titanic).
Although it is not operationally authorized to fly deliberately outside the normal flight envelope, it is not unsafe (in isolation) and it may happen (strong head gust or engines commanded at full power in level flight and pilot momentarily not in monitor/control of the speed/trajectory). In such extreme cases the high speed protection may be activated (threshold is Mmo plus a margin less a phase advance) and the protection may command a nose-up load factor until the speed is back below Mmo.
So why such a blind procedure as Speed Brakes Lever... FULL in case of a Mmo exceedance? Why the urgency to use the SBs?
Let's imagine the following scenario: you are dodging thunderstorms and you get yourself in a situation when you encounter some solid turbulence. At this point your airspeed begins to fluctuate and your margins are now small. The flight controls becomes less effective. The engines will be “sucking wind” and the aircraft begins to wallow in the sky. Suddenly you enter Mmo and you blindly apply the QRH: Speed Brakes... Full.
Can anyone imagine what may happen next?! Not a nice feeling.
Any clever thoughts about this subject would be most welcome. Thanks.
As soon as the speed exceeds VMO/MMO, apply the following actions:
AP : KEEP ON
SPEED BRAKES LEVER....................................................... .................................... FULL
THRUST REDUCTION................................................... .............................................MONITOR
If the A/THR is OFF:
ALL THR LEVERS...................................................... .............................................IDLE
If the AP automatically disengages:
HIGH SPEED PROTECTION : ACTIVE IN NORM LAW
The activation of the high speed protection results in an automatic pitch up
in order to reduce the speed.
While the speed is above VMO/MMO:
SPEED BRAKES LEVER : KEEP FULL
PITCH ATT......................................................... ADJUST SMOOTHLY AS RQRD
When the speed is below VMO/MMO with a sufficient margin to VMO/MMO:
SPEED BRAKES...................................................... .............................................AS RQRD
If the A/THR is OFF:
ALL THR LEVERS...................................................... ...................................... MAN ADJUST
If the AP is OFF:
FLIGHT PATH........................................................ ..................................... RECOVER SMOOTHLY
In the case of severe turbulence:
Refer to PRO-SUP-91-10 Adverse Weather - Severe Turbulence