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-   -   AOA stall warning indicator (https://www.pprune.org/tech-log/495514-aoa-stall-warning-indicator.html)

ATC Watcher 14th Sep 2012 14:01

AOA stall warning indicator
 

How to counter turbulence, worth 1000 diagrams, Enjoy.

Can someone explain the AOA/stall warning indicator seen at 03:27 ? never seen one before. I understand 1,3 VS ( approach speed) but the yellow/black zone ?
Just curious.

Pilotage 14th Sep 2012 14:16

Looks like it's just been divided into ~1.3Vs, "slow", "stupidly slow", and "you've stalled you idiot".

Machinbird 14th Sep 2012 14:49


Looks like it's just been divided into ~1.3Vs, "slow", "stupidly slow", and "you've stalled you idiot".
That is looking at it with a 1 'g' airline mentality. The word 'slow' is a misnomer. The airspeed is likely quite OK for flight.

This is an aircraft that is maneuvered aggressively.
Stay out of the Red zone and you are flying.
If you pull it into the red zone and it begins to depart, push it forward until you are out of the red zone.
The cross hatch area tells you that you had better have this gage in your scan and to pull smoothly to avoid nasty surprises while maneuvering.

Lyman 14th Sep 2012 15:02

'The cross hatch area tells you that you had better have this gage in your scan and to pull smoothly to avoid nasty surprises while maneuvering."

This is where Bonin was, three seconds into manual control.

If Bonin had anything to look at that would have helped, perhaps it should have been red.

HazelNuts39 14th Sep 2012 16:08


Originally Posted by Machinbird
The cross hatch area tells you that you had better have this gage in your scan and to pull smoothly to avoid nasty surprises while maneuvering.

I would think the cross hatch area means that stall warning is active. You should relax your pull until you're out of it.

Pilotage 14th Sep 2012 16:30


Originally Posted by Machinbird (Post 7413629)
That is looking at it with a 1 'g' airline mentality. The word 'slow' is a misnomer. The airspeed is likely quite OK for flight.

This is an aircraft that is maneuvered aggressively.
Stay out of the Red zone and you are flying.
If you pull it into the red zone and it begins to depart, push it forward until you are out of the red zone.
The cross hatch area tells you that you had better have this gage in your scan and to pull smoothly to avoid nasty surprises while maneuvering.

Well it was labelled 1.3Vs, but strictly just as Vs will always be at the same AoA so will 1.3Vs if you work through the maths.

So it still holds true at, say, 2g.

As of-course do your comments.

P

Machinbird 14th Sep 2012 16:55


I would think the cross hatch area means that stall warning is active. You should relax your pull until you're out of it.
In the airline sense of the word that is true. If you are pulling to miss a ridge, then there is still more performance available. They do likely activate the stick shaker or stall warning horn in that range assuming they are using one in that aircraft.
http://www.pprune.org/home.comcast.n...-Indicator.JPG
http://www.pprune.org/home.comcast.n...-Indicator.JPG

Intruder 14th Sep 2012 19:02

Another possibility is the crosshatch is the pre-stall buffet area. The top of that area may equate to min sink speed...

ATC Watcher 15th Sep 2012 09:52

Thanks for your guesses, so far I came too. I expected someone here might have flown the Canadair or at least been in a cockpit and asked the question.

For instance is the indicator a simple outside sensor reader, or a more sophisticated device coupled to the flaps settings ?
Because seen the aircraft flaps size , Vs must vary a lot with out without them, (and as you can see on the video, they almost always apply some flap seetings during their manoeuvres.)

Intruder 15th Sep 2012 17:57

The sensor is likely a simple wind vane. Since there are no leading edge devices, stall AOA is likely very close to the same value, relative to the leading edge, whether the flaps are up or down or in between.

In Navy airplanes I flew that had leading edge devices, there were markings on the AOA gauge to discriminate between clean and dirty stall AOA. Still, a simple (or sometimes a bit more sophisticated) wind vane was the basic sensor.


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