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Air Asia Indonesia Lost Contact from Surabaya to Singapore

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Air Asia Indonesia Lost Contact from Surabaya to Singapore

Old 7th Feb 2015, 07:49
  #3081 (permalink)  
 
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It would be good if pilots could easily download sim scenarios for these newsworthy incidents, and work through them.
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Old 7th Feb 2015, 11:34
  #3082 (permalink)  
 
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AirAsia flight QZ8501: Bodies of two pilots found in cockpit, one retrieved - South-east Asia News & Top Stories - The Straits Times
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Old 7th Feb 2015, 12:46
  #3083 (permalink)  
 
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Pushing Over

I know that there are a LOT of posts as far (agreement is probably going too far) to the effect that pushing forward, or anything less than 1.00 positive G is uncomfortable, unfamiliar, non-intuitive, and frowned on by management. But it seems pretty clear that poster opinion agrees that there are circumstances when this action is appropriate and even immediately mandatory.
Aerodynamics 101: The stall speed at 0 'g' is 0 kts. Therefore if you have the elevator authority to push to zero 'g' you will unstall the wing at any airspeed. The nose will drop, the airspeed will increase and when comfortably above Vs1g, gently roll wings level and raise the nose to the horizon. If you don't have elevator authority to push forward enough to unstall the wing, ROLL the aircraft (90+ bank if need be) and convert that pitching 'up' moment away from the horizon into a pitching 'up' moment across (or down from) the horizon to get the nose to drop and airspeed to increase.
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Old 7th Feb 2015, 15:52
  #3084 (permalink)  
 
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Yes Bleve, the concept of zero stall speed at zero "g" does not seem to be instinctive to pilots that have never worked beyond 30 degrees of bank. If I may add to your post -

"If you do not have elevator authority to push forward enough to unstall the wing - get that authority by trimming forward and reducing thrust if needed".

If the nose does not do as you command it in a 320, the trim is yours!
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Old 7th Feb 2015, 17:36
  #3085 (permalink)  
 
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Perhaps all that is needed is... automatics sensing approach to stall .... as the aircraft approaches stall the THS could stop trimming nose up
You mean like the A320 does?
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Old 7th Feb 2015, 18:53
  #3086 (permalink)  
 
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@IanW;
#3109, http://www.pprune.org/rumours-news/5...ml#post8857067, "Had the THS motored to neutral in the AFR447 case the aircraft would probably have pitched nose down and might have been recovered. "
Point-of-information: - the THS would have motored from -13.5 to about -2 had the stick been held fully-forward for a sufficiently long period and very likely the aircraft could have been recovered. Also, manually rotating the trim wheel disengages the autotrim permitting a quicker setting of the THS. When released from manual movement in a few seconds it returns to auto and begins to take into account control inputs, but by that time recovery actions are theoretically taking place and the THS would follow-up with the SS orders.
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Old 7th Feb 2015, 19:00
  #3087 (permalink)  
 
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Originally Posted by NigelOnDraft View Post
You mean like the A320 does?
Exactly Nigel, but perhaps you should continue with the quote. When it _is_ stalled the A320 just keeps the THS where it got to, if it motored to neutral it could help a lot. Unless you can think of a reason after the stall why the THS should stay nose up at all.
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Old 7th Feb 2015, 19:32
  #3088 (permalink)  
 
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anything less than 1.00 positive G is uncomfortable, unfamiliar, non-intuitive, and frowned on by management.
I guarantee that meeting the surface of an ocean @10,000fpm is even more uncomfortable...

If the nose does not do as you command it in a 320, the trim is yours!
Every part of an aircraft should ALWAYS do as its commander commands it - else he does not '...have final authority as to the disposition of the aircraft...' as required by the Chicago Convention.

How on earth did we end up designing and accepting aircraft that the pilot cannot COMPLETELY override if necessary, and automation that confuses, confounds, and when the fecal hits the turbine, leaves you to recover from an unusual and precarious situation requiring counter-intuitive actions?
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Old 7th Feb 2015, 19:48
  #3089 (permalink)  
 
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When it _is_ stalled the A320 just keeps the THS where it got to, if it motored to neutral it could help a lot. Unless you can think of a reason after the stall why the THS should stay nose up at all
How do you definitively define "it is stalled"? To a high enough degree of integrity you can remove pitch control from the pilot?
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Old 7th Feb 2015, 19:48
  #3090 (permalink)  
 
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Inquisitor

Spot on

The aircraft i've operated, and there has been quite a number, If all else failed I could be pretty sure of having a set of primary controls to manipulate to the desired effect. This now seems to be no longer the case.

Indeed how was it ever certified in it's present state??
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Old 7th Feb 2015, 20:11
  #3091 (permalink)  
 
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Quote:
Perhaps all that is needed is... automatics sensing approach to stall .... as the aircraft approaches stall the THS could stop trimming nose up
You mean like the A320 does?
NOD-only true for the 99.999% of the time you are in Normal Law. In Alternate law-Not true. During an upset, you are very likely to end up in Alternate law.

One thing that will interfere with achieving the necessary near 0 g in a nose high upset (which must be maintained until the aircraft is actually nose low and flying again) is an excessively trimmed THS.
(There is a good possibility that the THS trim was a factor in the Air Algerie failure to recover from its stall and roll off.)


P.S. I know you know the A320 systems very well.
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Old 7th Feb 2015, 20:20
  #3092 (permalink)  
 
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Sop Monkey

"The aircraft i've operated, and there has been quite a number ..."

Evidently not an Airbus, seeing your questions about A320 spoilers, which no-one bothered to answer (because G;ggle would have clarified all in 5 min).

How was it ever certified? Because the FAA certified it, that's why. You think jet transports should still be designed with wires pulling the control surfaces?
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Old 7th Feb 2015, 22:26
  #3093 (permalink)  
 
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When it _is_ stalled the A320 just keeps the THS where it got to, if it motored to neutral it could help a lot. Unless you can think of a reason after the stall why the THS should stay nose up at all
How do you definitively define "it is stalled"? To a high enough degree of integrity you can remove pitch control from the pilot?
When the stall warning sounds?

i.e., if the stall warning goes off, THS must automatically roll forward to at least neutral asap (or go nose-down if you -- controversially -- want to simulate a stick-pusher)

Of course, this should be something not needed to be left to automation
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Old 7th Feb 2015, 22:34
  #3094 (permalink)  
 
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When the stall warning sounds?

i.e., if the stall warning goes off, THS must automatically roll forward to at least neutral asap (or go nose-down if you -- controversially -- want to simulate a stick-pusher)
So if as I rotate on takeoff, the Stall warner erroneously sounds, the THS drives the aircraft into the ground

PS
...to at least neutral
What is "neutral" in airliner terms?
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Old 8th Feb 2015, 01:14
  #3095 (permalink)  
 
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Originally Posted by NoD
How do you definitively define "it is stalled"? To a high enough degree of integrity you can remove pitch control from the pilot?
How do you suddenly bother about that ... ?
How do Airbus definitively define "it is going to stall" ? To a high enough degree of integrity Airbus can remove pitch control from the pilot ?
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Old 8th Feb 2015, 01:25
  #3096 (permalink)  
 
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So if as I rotate on takeoff, the Stall warner erroneously sounds, the THS drives the aircraft into the ground
I was just putting the logical result of Ian W's suggestion into words as it is an interesting idea and I try to keep an open mind -- but I don't think the solution is more automation, hence why I put "controversially" and why I ended how I did.

I won't get into a fight, since you drive A320s and I don't, but AFAIK existing stick pusher logic includes an altitude minimum (e.g. Q400 only activates > 200 feet AGL), so there's no reason you would not implement equivalent logic *if* you were to do this.
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Old 8th Feb 2015, 02:21
  #3097 (permalink)  
 
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A stick pusher is a stall identifier, it is not a stall warning.
They are two different systems.
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Old 8th Feb 2015, 06:43
  #3098 (permalink)  
ekw
 
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So lets say 2 in every 10 pilots are aces, 3 are average and 5 are dunces. Which group does automation help and which group would be less affected by more automation? The logic is simple surely?

Last edited by ekw; 8th Feb 2015 at 06:52. Reason: comments too far fetched
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Old 8th Feb 2015, 10:01
  #3099 (permalink)  
 
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Air Asia Indonesia Lost Contact from Surabaya to Singapore

For those suggesting Stick pushers, or a mechanism to set a neutral tail plane at the stall consider this: To have arrived at that situation in the first place a failure has occurred, quite probably with one of the systems that would have been providing the information that the recovery system would be using!

In order for a recovery system to have any validity it would need aircraft data from a COMPLETELY independent source, actually SEVERAL independent sources.

Now, if you are going to do that why not just take those sources and use them to supply data to the original fly by wire so you don't stall in the first place.
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Old 8th Feb 2015, 11:13
  #3100 (permalink)  
 
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Isn't the real story here that airlines / manufacturers want to fully automate flight. Pilots and crew are seen as expensive.

And so Airbus has tried to start that process. It couldn't go all the way fully-automated because there would be huge resistance from passengers / crew / regulators, but it has implemented a beginning.

The Airbus system comes with a manual of how to use it, makes it sound so easy ... however if something goes wrong it is unclear how to resolve the situation because the system's many secrets are not made available and in an emergency you have seconds to understand what's going on under the hood.

Airbus does not want pilots to be able to switch the system off at will, because that would derail the business plan of full automation.

For the bean counters, it's just money. Lives lost though regrettable are just a matter of insurance.

Automation seems the trajectory of the economy ... unless something changes. And we are now in an intermediate phase were there is an inevitable dishonesty about what is occurring, because automation is being phased in semi-covertly.

If the pilots / crew make a fuss, or passengers / airlines are scared ... then it will slow things down. If new plane technologies come through that require pilots, it will slow things down. If pilots were seen once again as part of the experience, it will slow things down. If the world gets richer suddenly it will slow things down.
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