47
votes
Is it practical to intentionally stall an aircraft to execute a fast, controlled descent?
It isn't practical for a number of reasons:
Intentional stalls are inherently dangerous. Stall-spin accidents are a major cause of accidents, stall recognition and recovery are taught specifically to ...
- 49.1k
36
votes
People in a rollercoaster or falling elevator feel the rapid descent, so why don't pilots in the cockpit?
You only feel the acceleration downward. In roller-coaster this sensation is maximized for maximum thrill. A stall isn't instant: some parts of the wing can be stalled while the rest still provides ...
- 26.9k
32
votes
Accepted
How does an A330 detect stall without airspeed?
Stalls occur based on a wing's angle of attack rather than the aircraft's airspeed. (In fact, one of the basic facts that all pilots learn in their initial training is that an airplane can stall at ...
- 22.2k
31
votes
Accepted
On Air France 447, what would have been the lowest altitude to initiate recovery after the stall developed?
For the stalled flight to recover, the nose needs to be pointed in the airstream, and then the aircraft pulled up with load factor below the ultimate load. From the accident report:
The recordings ...
- 57.7k
30
votes
People in a rollercoaster or falling elevator feel the rapid descent, so why don't pilots in the cockpit?
You only feel the plunging sensation during the initial downward acceleration. Once stabilized at a constant rate of descent, things feel normal again. The other thing is, the amount of vertical ...
- 103k
22
votes
How can a pitot tube freeze when it's heated?
Captain Bill Palmer, in his book "Understanding Air France 447" has a section dedicated to answering that very question as it pertains to AF447. Although there is no way to know for certain he puts ...
- 27.5k
21
votes
Accepted
Is it practical to intentionally stall an aircraft to execute a fast, controlled descent?
You don’t need a new technique
You don’t normally stall jetliners. And in a crisis the last thing you want to do is learn a new technique.
Besides, they already have a trained practice for descending ...
20
votes
Accepted
What does the autopilot do if activated in a stall condition?
In the AF447 accident, the autopilot disconnected because of inconsistent airspeed:
Temporary inconsistency between the airspeed measurements, likely following
the obstruction of the Pitot probes by ...
- 43.9k
19
votes
Would mechanical indicators have helped in the Air France 447 incident?
Unfortunately, if there had been a jazz band in the cockpit singing "The plane is stalling" it wouldn't have helped. If Moses had been in there carrying a stone tablet newly-carved by God himself ...
- 12.6k
19
votes
Is it practical to intentionally stall an aircraft to execute a fast, controlled descent?
Normally, a stall and controlled flight are mutually exclusive.
That AF447 would descend as it did has to do with the relaxed static stability of the A330 and its rear cg location as well as the ...
- 217k
18
votes
Accepted
Could the GPS be used to aid the autopilot with speed?
GPS speed is already available to the crew, although not in an easy to see place. It isn't designed to cross-check other instruments because it is showing entirely different information. The winds ...
- 57.5k
17
votes
Could the GPS be used to aid the autopilot with speed?
The main issue is that we can only get groundspeed from GPS data. Winds aloft aren't known exactly at a particular place, so they could be rather inaccurate -- certainly not enough to leave to the ...
- 10.4k
16
votes
Would mechanical indicators have helped in the Air France 447 incident?
@mike rodent I've read your comments on this post and they seem rather strong in tone to me. I'm joining the discussion here to hopefully explain to you why your ideas are not going to work as you ...
- 39.1k
14
votes
Is it practical to intentionally stall an aircraft to execute a fast, controlled descent?
It is smarter to roll onto your side and maintain unstalled flight, executing a emergency spiral descent. G loads on the wings are much lower as there is no need to maintain altitude, only to control ...
- 14.2k
13
votes
Accepted
Why did AF447 never return to normal law?
If the system detects anomalies for more than about ten seconds, alternate law becomes locked in for the remainder of the flight.
The system detected a change in the median value of the three ...
- 27.5k
12
votes
Accepted
Do Airbus pilots have to practice flying in alternate law?
It appears in both situations that the PF had trouble stabilizing the aircraft roll attitude.
Note that roll control is secondary when recovering from a stall.
Restoring normal pitch and roll, he ...
- 25.8k
12
votes
Would mechanical indicators have helped in the Air France 447 incident?
A flag is not really effective because a big jets stalling speed is well over 100+ knots. The flag will be blowing fully even in the stall. I'm not familiar with the ship suggestion but it sounds like ...
- 13.1k
12
votes
Accepted
What other circumstances may cause the autopilot to trip out?
What other circumstances may cause the autopilot to trip out?
There are numerous circumstances, a few at random
pilot presses the autopilot disconnect pushbutton.
applying force to control-stick ...
- 25.8k
11
votes
Would mechanical indicators have helped in the Air France 447 incident?
Wouldn't these two measures have had a good chance of providing the pilots of AF 447 with a true and totally irrefutable mental picture of what was actually going on?
No more so than the standard ...
- 24.8k
10
votes
Why Air France 447 could not reduce angle of attack?
I just finished reading this article and couldn't understand why in 3
minutes and 30 seconds even though there was no reliable speed data,
pilot could not level the plane?
If you look at this ...
- 74.2k
10
votes
People in a rollercoaster or falling elevator feel the rapid descent, so why don't pilots in the cockpit?
You are forgetting one large difference between an aircraft moving through the air (still generating some lift), and an object in free-fall. Constant velocity in a gravity well (such as on the Earth) ...
- 215
9
votes
Accepted
What improvements did Airbus make as a result of the Air France 447 accident?
What improvements did Airbus make as a result of the Air France 447 accident?
The official report has a section headed
5 - CHANGES MADE FOLLOWING THE ACCIDENT
...
5.2 Airbus
Review of the “...
- 25.8k
9
votes
Accepted
Why did Air France flight 447 fail to recover from the stall?
I‘ll attempt a very brief answer based on the report against your questions:
1) Why did the aircraft stall?
The aircraft stalled because crew pitched the aircraft up beyond the performance limit at ...
- 4,512
8
votes
Do Airbus pilots have to practice flying in alternate law?
Air France 477 was in a fully developed stall. In a normal flight attitude. All the way from 40,000 feet to the surface of the ocean. The aircraft was falling like a leaf from a tree, with an angle of ...
- 57.7k
8
votes
Accepted
How often are aircraft flown by two FO's?
I'd say this is quite common on flights that require at least 3 pilots due to length. The third pilot is almost assuredly going to be qualified as a first officer and this is the common staffing ...
- 34.8k
8
votes
What does the autopilot do if activated in a stall condition?
On just about all airplanes the Stall Protection System disengages the autopilot automatically whenever a range of parameters is exceeded. One of them is approaching stall. Generally the Autopilot ...
- 103k
7
votes
Accepted
How much can falling down due to a stall influence the angle of attack?
In AF447 the falling motion most definitely affected the angle of attack. Due to the fact that the pf did keep the stick pulled back for all but the last few seconds of the fall the aircraft was so ...
- 27.5k
7
votes
Accepted
What could these possibly incorrectly translated numbers for aircraft speed have been?
I think there is some information lost in translation.
The speeds of 13000 kmph are associated with reentry vehicles. The aircraft won't have had time to accelerate to that speeds in the first place,...
- 98.3k
6
votes
Why did the pilot flying pull back in the moments after the auto-pilot disconnected on AF447?
It's not accident speculation when it has been investigated.
The full accident report is available online with a very adequate summary on Wikipedia.
There are many reasons, but from the human factors ...
- 119k
6
votes
How much can falling down due to a stall influence the angle of attack?
Your understanding of the situation is correct: The angle of attack was beyond stall and the aircraft was in a descent which reduces the pitch attitude, so the resulting acceleration felt to the ...
- 217k
Only top scored, non community-wiki answers of a minimum length are eligible