Go Back  PPRuNe Forums > Flight Deck Forums > Tech Log
Reload this Page >

AF447 final crew conversation - Thread No. 1

Tech Log The very best in practical technical discussion on the web

AF447 final crew conversation - Thread No. 1

Old 27th Oct 2011, 03:13
  #441 (permalink)  
 
Join Date: Aug 2005
Location: fl
Posts: 2,561
When you learn to fly by instruments you need to ignore what your body feels. Vertigo will kill you if you let it. JFK JR did just that when he went in his graveyard spiral. I have been there and know what it feels like but when it happened I knew if I didn't believe those instruments and went by my instincts I was dead. I was laying over half sideways fighting the instinct to go with my body which felt upright and that self survival instinct vs. believe the instruments. We were IFR in a Lear Jet at high altitude and didn't have a lot of time to sort things out. Pilot experience actually flying, not monitoring an autopilot, sometimes pays off. It would be interesting how much stick time these two had. Monitoring the autopilot doesn't count.

My buddy was flying the empty Lear Jet and decided he wanted to hand fly it while I was balancing fuel with my head sideways when I saw everything going bad and took over. It ended up ok but could have been a disaster for us. I couldn't sit up straight until we descended below the clouds.

Seems like if the PNF had been more agressive he could have prevented what the PF caused by holding full back on the SS.
bubbers44 is offline  
Old 27th Oct 2011, 05:06
  #442 (permalink)  
 
Join Date: Oct 2005
Location: Europe
Posts: 23
Just a wild stab at "fuzzy" logic from non-professional:

They were going down and they could not understand what is going on for an extended period of time. That can mean that by that time they also ceased to trust some of their instruments. So what did they believe from the data they were seeing or assuming? That can be deduced from the only constant in their behavior: "stick held fully back" most of the time. In any dangerous situation with unreliable information present, you are relying only on those information that you assume to be most reliable, and you are doing only what is most important for the moment. You will stop falling that way only if you have forward speed, so that must be what they thought to be most reliable of the important information. It is very difficult to assume that all THREE pilots could miss the very possibility of stall, regardless of their training and practical experience. One, yes, but all three, no. However, if you are sure that you have forward speed, there is no stall, so that neatly explains both facts. If it is really true that they tried other things, but stubbornly insisted without changing only on that one action, than that is what all three of them believed.
PaleBlueDot is offline  
Old 27th Oct 2011, 05:09
  #443 (permalink)  
 
Join Date: Aug 2011
Location: Grassy Valley
Posts: 2,123
Once stabilised, there is no 'acceleration', and one does not feel velocity, but one can hear it. There were no CUES, the STALL was abnormal. They felt more or less as they would have felt on the ramp. There were fluctuations in VS, and these would have added to the confusion, imho. Accelerating from the top of climb would have likely been exhilarating, but reaching 100 knots down in vertical velocity would not take long. The ship showed manageable, if not pleasant characteristics (in the descent, STALLED), again a confusion in territory one has been led to believe is mysterious, and unavailable to the BUS.

When stable at 1g, the Vertical speed would not be believable, it would be hard to accept. Close to the surface, the pilots comments were limited to specific altitudes, not their vertical speed. Again, they had no instrumentation or feel that suggested their predicament. No "believable instrumentation", that is. So get a grip, and lose the feigned shock; in that cockpit, no one would know what was happening. Acting like these three were too thick to sense the obvious is ridiculous. Nothing was 'obvious' and I feel no flyer would have had a clue.

What mystifies me is the power they carried throughout. If too fast, and in some kind of descent, closing the levers would be second nature. Is there a remote possibility They were in Autothrottle? Could they have been in Autopilot? At any time after the first loss of it?

Have BEA rejected with proof that the climb was uncommanded, or partially so?
Lyman is offline  
Old 27th Oct 2011, 05:36
  #444 (permalink)  
Green Guard
Guest
 
Posts: n/a
Monitoring the autopilot doesn't count
one of.... if not ...the best statement so far
 
Old 27th Oct 2011, 08:12
  #445 (permalink)  
 
Join Date: Sep 2010
Location: Mildura
Posts: 76
I'm not sure if this has been asked or discussed previously, but do the pilots have a GPS or INS based groundspeed readout on their displays? Also i was under the impression that heavy jets are equipped with AoA sensors?

Would not a very low groundspeed and high AoA readout cause the assumption of a stall? especially seeing as these readouts would not be related to the Pitot system if it was faulty.

Sorry if this is unrelated or has been discussed I have not followed this from the beginning and have not flown anything more complex than piston twins.
TriMedGroup is offline  
Old 27th Oct 2011, 09:06
  #446 (permalink)  
 
Join Date: Jun 2009
Location: Australia
Posts: 49
One G ?

Lyman, this one G thing confuses me. One G is what you get when your NOT falling, ie what the bus uses to fly level I've read, and what you'd feel on your bum. I'd have thought that falling at their rate you would "weigh" a fair bit less all the way down. Not suggesting that would matter in all the confusion, but physics interests me.
Air Tourer is offline  
Old 27th Oct 2011, 09:28
  #447 (permalink)  
Green Guard
Guest
 
Posts: n/a
true...but only during acceleration
after certain speed is achieved = the drag and weight are same, no more accelaration and you have a pure 1 g
 
Old 27th Oct 2011, 09:58
  #448 (permalink)  
 
Join Date: Jun 2009
Location: Australia
Posts: 49
Wait/ Weight

I'm sure your right but I'm talking about the people in the a/c. Does that work for them? I'm thinking about the astronauts free falling in a jet nosing over, or astronauts in orbit, speed constant yet no 1g for them.
Air Tourer is offline  
Old 27th Oct 2011, 10:39
  #449 (permalink)  
 
Join Date: Jan 2008
Location: UK
Posts: 116
The astronauts are weightless only while the aircraft is 'bunting' over, accelerating downwards, and pushing negative 'g'.

In orbit, the vehicle is constantly accelerating downwards (a process offset by its speed).
Aileron Drag is offline  
Old 27th Oct 2011, 12:33
  #450 (permalink)  
 
Join Date: Aug 2009
Location: Germany
Age: 63
Posts: 1,809
Lyman, this one G thing confuses me. One G is what you get when your NOT falling, ie what the bus uses to fly level I've read, and what you'd feel on your bum. I'd have thought that falling at their rate you would "weigh" a fair bit less all the way down. Not suggesting that would matter in all the confusion, but physics interests me.
No need to go in a aircraft for experiment sensations of vertical displacement
Try an elevator (if never experienced !) and you will understand .. and it's cheapest than an aircraft experience
jcjeant is offline  
Old 27th Oct 2011, 12:44
  #451 (permalink)  
 
Join Date: Nov 2010
Location: FR
Posts: 478
jcjeant: spot on. Air Tourer, I concur, the elevator test is good. I tested that on a ground to 35th floor in a business tower, because I was amazed by how "smooth" the ride was, however quick. I used my smartphone accel sensor to check how many g I "took" in this elevator.
~1.15 max when accelerating from ground level or descelerating arriving at ground
~0.85 min when descelerating at top or accelerating from top to ground
1 g stable during the stabilised phase of the "ride" (=no "falling" nor "going up feeling", except for the ears)

About the sensation by the ears: nope, the plane was pressurized, i.e. constant cabin pressure above 8000ft

Last edited by AlphaZuluRomeo; 27th Oct 2011 at 16:03. Reason: adding precisions
AlphaZuluRomeo is offline  
Old 27th Oct 2011, 12:49
  #452 (permalink)  
 
Join Date: Jan 2008
Location: lancs.UK
Age: 73
Posts: 1,196
Please forgive what may well be a crass comment from a non-pilot who lacks the benefit of those hundreds of hours of professional training.

It would appear the crew were in "unusual attitude " situation.

Logic, to me, dictates that, if the aircraft was in the cruise prior to the upset, the trim and power were set for stable flight.

It would seem elementary, that no matter how much increased power was applied, continued back-pressure on the controls must result in either a loop (repeated until the stick is returned to the "balanced flight" position) OR the angle of climb would increase until the power available balanced gravity(+ lift) at which point the thing drops out of the sky ,tail down, presumably with reduced thrust available due to the abnormal airflow around and through the engines. (effectively a high-speed stall?)


It's easy to sit pontificating, but it seems they forgot the fundamental physics of flight and sat in a blind funk of panic.

No, I'm not a "simmer"
cockney steve is offline  
Old 27th Oct 2011, 13:44
  #453 (permalink)  
 
Join Date: Feb 2008
Location: Tunbridge Wells, UK
Age: 42
Posts: 109
OR the angle of climb would increase until the power available balanced gravity(+ lift) at which point the thing drops out of the sky ,tail down, presumably with reduced thrust available due to the abnormal airflow around and through the engines. (effectively a high-speed stall?)
This wouldn't happen while stall protection is still available (which as far as I'm aware it was). I think it's far too simple to assume that the PF had, for some reason, temporarily forgotten the physics of flight. Far more likely to be a combination of factors including (though not limited to); severe spatial disorientation, confusing messages from the a/c and possibly the belief that pulling back on the stick was the best way to recover that particular a/c from the situation he believed it to be in.
TurboTomato is offline  
Old 27th Oct 2011, 14:08
  #454 (permalink)  
 
Join Date: Mar 2009
Location: Phoenix, AZ USA
Age: 62
Posts: 0
I'm amazed at the amount of "needless" speculation for a relatively simple event. The PF simply failed to respond correctly to what should have been a non event. Had he followed his training and flown pitch and power then this is just one of dozens of similar incidents that plagued the 330/340 series.

His error was compounded by the senior pilots (on flight deck) failure to exercise command authority even though he knew the PF was over-matched by the situation.

I do not believe the aircraft was recoverable by the time the Captain returned to the flight deck however I do believe his failure to assume command (as PF) was an incorrect decision.

There is no indication that the initial climb was anything other then a response to stick inputs by the PF. Further the trim was a response to his continued application of control input. There was no autopilot or system induced "runaway trim". The aircraft was perfectly flyable from the moment AP disconnected until it hit the water.

At the end of the day the lesson is simple...the more you en devour to remove the aviator from aviation the more likely you are to have this type of end result.
SLFinAZ is offline  
Old 27th Oct 2011, 14:43
  #455 (permalink)  
 
Join Date: Dec 2007
Location: Pasadena
Posts: 633
g=1 when falling with no acceleration.

You feel weightless only when you're accelerating down. When you're falling at a steady speed you feel 1g.

The elevator comment is absolutely right: when cruising between floors, you can't tell you're moving. The light and heavy gut feeling only comes when the elevator speeds up or slows down.

Astronauts are free-falling continuously around the earth: the earth is just curving away so they don't hit it. They are accelerating towards the centre of the earth under gravity at 1g, but so is the space station, so they feel neither weight not a reaction force from the walls.

If you're falling steadily, with weight balanced by drag, and so no acceleration - either when `free-fall' parachuting at terminal velocity, or aboard AF447 - your gut feels like it would sitting on the couch.

Added:

Although you would feel like you were sitting on the couch, it would be a couch tilted back against the wall.

A plumbline would show your attitude, although you'd need a hanging spring balance to confirm there was no acceleration to confuse the result. There may also have been enough shaking to make that ineffective.

If the captain had clung to a handle rather than strapping into a jumpseat, that might have been enough to convince him of the nature of the situation, as his feet would have dragged aft compared with his head to balance.

Last edited by awblain; 28th Oct 2011 at 18:12. Reason: Added note
awblain is offline  
Old 27th Oct 2011, 16:03
  #456 (permalink)  
 
Join Date: Jan 2011
Location: West Lothian
Posts: 4
ok here goes, virgin poster so go easy on the flames, eh ...

As i understand it, this aircraft was descending "straight? and level" at 10,000 ft/min therefore its AoA was pretty much 90. Would it have made a blind bit of difference if the stick was fully forward in this situation as the air going over the elevator wasnt coming from an influencable direction. -- i just made that word up !!!

When i read further in the thread that having low slung engines prouduces a pitching up affect with power, then "stick forward and full power" would seem, to my little mind anyway, have bugger all chance of saving the souls in that situation anyway.

Power at idle and "this is your captain speaking, could everyone onboard run like hell up to the front of the aircraft" ... might have had more chance of getting the thing back to controlled flight.

mind... 1st post so go easy.
captin_tea is offline  
Old 27th Oct 2011, 16:13
  #457 (permalink)  
 
Join Date: Nov 2010
Location: FR
Posts: 478
Originally Posted by captin_tea View Post
As i understand it, this aircraft was descending "straight? and level" at 10,000 ft/min therefore its AoA was pretty much 90.
Ahem... no. Incorrect assumption. "straight and level" doesn't imply "with zro forward speed". Only if you have "straight and level + zro forward speed" will your AoA be ~90
Actual AoA from AF447 can be read easily on the published FDR traces, it was never close to 90.

However:
- given the situation, indeed TOGA was bad, Idle would have been better
- given the situation, indeed all pax in front would have help; no idea if it would have been significant
AlphaZuluRomeo is offline  
Old 27th Oct 2011, 16:22
  #458 (permalink)  
 
Join Date: Feb 2009
Location: Toronto, Canada
Posts: 25
Re: 1g felt?

The BEA interim report #3 shows the last data before impact of 1.012 g Nz, -.17 Nx (lateral), -.10 Ny (longitudinal). 16.2 deg nose up, 5.3 deg L roll, -10912 fpm. The traces show Nz typically between 0.9 and 1.1, with occasional increases to around 1.2, during about the last 2 1/2 minutes of flight.
Edit: Ground speed 107 kts, so it wasn't close to a 90 deg descent.

So, yes, the descent was in a pretty much a "1g environment".
pchapman is offline  
Old 27th Oct 2011, 16:37
  #459 (permalink)  
 
Join Date: Jan 2011
Location: West Lothian
Posts: 4
Actual AoA from AF447 can be read easily on the published FDR traces, it was never close to 90.
Ground speed 107 kts, so it wasn't close to a 90 deg descent.
ok, ma bad. still trying to get my head round how it could have had forward speed with a nose up attitude and that rate of sustained descent. however - thats my head and my problem.
captin_tea is offline  
Old 27th Oct 2011, 17:34
  #460 (permalink)  
Per Ardua ad Astraeus
 
Join Date: Mar 2000
Location: UK
Posts: 18,582
Heck - I just keep on seeing that bird..................................anyone got a 12-bore?
BOAC is offline  

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information

Copyright 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.