Go Back  PPRuNe Forums > Flight Deck Forums > Rumours & News
Reload this Page >

Flaperon washes up on Reunion Island

Rumours & News Reporting Points that may affect our jobs or lives as professional pilots. Also, items that may be of interest to professional pilots.

Flaperon washes up on Reunion Island

Old 22nd Aug 2015, 19:22
  #581 (permalink)  
 
Join Date: May 2014
Location: Colorado
Posts: 17
In all the simulator tests we conducted, the aircraft begins a turn shortly after fuel exhaustion. The turn evolves into a very steep spiral descent with bank angles close to 90 degrees in some cases. Phugoids were also observed. Speeds over the 500 KIAS (instrument display limit) were observed. Those were "indicated", not true. True airspeed was probaly close to Mach 1 in some cases observed (off the chart).
AirLandSeaMan is offline  
Old 22nd Aug 2015, 20:07
  #582 (permalink)  
 
Join Date: May 2011
Location: NEW YORK
Posts: 599
To Lemain:


I recognize sea water has sharp salinity and temperature differences, but am very skeptical that an object would just accidentally achieve such a fine tuned buoyancy as to make that relevant. It sure does not work for submarines, even though they have every incentive to make it happen.


To Airlandseaman:


I'd thought that the RAT would provide enough power to maintain wings level flight. Your simulator reference suggests that this is incorrect.
That seems a very material insight. Thank you for clarifying this issue.
etudiant is offline  
Old 22nd Aug 2015, 20:35
  #583 (permalink)  
 
Join Date: May 2014
Location: Colorado
Posts: 17
Here is a short editted piece from 4 hours of sims.

tinyurl_dot_com/oboepvg
AirLandSeaMan is offline  
Old 23rd Aug 2015, 02:21
  #584 (permalink)  
 
Join Date: May 2011
Location: NEW YORK
Posts: 599
To Airlandseaman:


Unfortunately the link: tinyurl_dot_com/oboepvg does not work.
etudiant is offline  
Old 23rd Aug 2015, 02:27
  #585 (permalink)  
 
Join Date: Nov 2009
Location: flying by night
Posts: 504
try tinyurl(.)com/oboepvg (without the parentheses)

Last edited by deptrai; 23rd Aug 2015 at 07:04.
deptrai is offline  
Old 23rd Aug 2015, 07:11
  #586 (permalink)  
 
Join Date: Apr 2009
Location: Oakland, CA
Age: 68
Posts: 427
I'd thought that the RAT would provide enough power to maintain wings level flight
Possibly true but for that autopilot must be ON. But with both engines out I suspect autopilot will switch off automatically and human intervention would be required to re-engage it. However I am not 777 pilot so can't tell for sure.
olasek is offline  
Old 23rd Aug 2015, 08:44
  #587 (permalink)  
 
Join Date: Jul 2008
Location: Skating away on the thin ice of a new day.
Posts: 1,032
olasek,

I'm hoping for a 777 engineer or pilot to step in here with how it actually works and to what extent, but the 777 has, iirc, quite a bit of envelope protection / stability augmentation built in without A/P engagement.

I am sure the RAT will power at least part of that system and if not the battery.
ampclamp is offline  
Old 23rd Aug 2015, 09:49
  #588 (permalink)  
 
Join Date: May 2014
Location: In thin air
Posts: 186
While I'm not " a 777 engineer or pilot", based on the available documentation my understanding is that the following happens after flame-out of both engines due to fuel exhaustion:

- all generated electrical power is lost, leaving only battery power,
- on battery power pitot heat is lost, the fly-by-wire flight control system (FCS) considers the airspeed unreliable and reverts to secondary mode,
- in FCS secondary mode envelope protection, turn coordination and TAC are lost, and the autopilot disconnects.
- the APU starts automatically and provides electrical and hydraulic power, until it too flames out when the fuel remaining in the supply line is exhausted,
- the RAT deploys and provides electrical and hydraulic power, restoring pitot heat and allowing the FCS to return to normal mode,
- with the FCS in normal mode the AP can be re-engaged by the pilot.

Standing by to be corrected by someone more competent than I am ...

P.S.
Here is another simulator "test" for comparison: Geoffrey Thomas reporting Flight MH370 simulation

Last edited by Gysbreght; 23rd Aug 2015 at 12:20. Reason: P.S.
Gysbreght is offline  
Old 23rd Aug 2015, 13:18
  #589 (permalink)  
 
Join Date: May 2014
Location: Colorado
Posts: 17
The tests I conducted with Paul were in an operational Thales simulator (Class D) and Paul (in the left seat) is (was, but now retired) a senior capt (7 years on the B777-200) at a major US airline w/ over 20,000 hrs TT. He knows the plane inside and out. I've spent many hours discussing MH370 with Paul, starting back in May 2014. Also many hours with another retired SR capt on 747s. With no pilot intervention, there is no AP or AT control after the second engine flames out, even after the APU starts.
AirLandSeaMan is offline  
Old 23rd Aug 2015, 13:29
  #590 (permalink)  
 
Join Date: Jan 2008
Location: UK
Age: 65
Posts: 294
Any simulator should behave the way the aircraft manufacturer designed the aircraft to work and how they believe it does work as built. MH370 is so bizarre with no really credible or incredible (except aliens?) explanation I question whether we should place total confidence on the sim for this disappearance.
Lemain is offline  
Old 23rd Aug 2015, 14:25
  #591 (permalink)  
 
Join Date: May 2014
Location: Colorado
Posts: 17
For all but one test, we ran the tanks dry with a 700-800 lb fuel imbalance (~4-5 mins), all hands off. The RAT fires up first, and the APU came on line about 20 seconds later. In one sim, we had a successful auto restart of one main engine that lasted about 2 seconds. Very violent reaction by the aircraft. Airplane banked about 80 degrees. We also tested the case for simultaneous flameouts with similar results. We found that it does not matter which engine flames out first. The plane always starts a post fuel exhaustion turn based on the pre fuel exhaustion rudder trim position dialed into the TAC.

It should be noted that we conducted no tests for any cases where it was assumed that a pilot was in control. We were focused on the ghost plane scenarios. Obviously, if a pilot was alive and engaged, then there are an infinite set of possibilities to simulate. Could have augured in very fast, changed course or glided for 80NM. But for the pilotless scenario, the sim's make it pretty clear that a fast, steep spiral descent is highly likely, ending in a very high energy impact. Such a scenario is consistent with the final BFO values that correspond to ~4500 ft/min descent rate at 00:19:29 and 15,000 ft/min at 00:19:37. At these descent rates, a very high airspeed is required, consistent with possible flutter and loss of the flaperon at some altitude before the main impact. Loss of the flaperon in flight could best explain the lack of impact damage. The flaperon could have “floated down” and made a relatively benign impact while the rest of the airplane hit very hard.
AirLandSeaMan is offline  
Old 23rd Aug 2015, 14:50
  #592 (permalink)  
 
Join Date: May 2014
Location: In thin air
Posts: 186
At these descent rates, a very high airspeed is required, consistent with possible flutter and loss of the flaperon at some altitude before the main impact.
It doesn't.

EDIT 1:
The quoted descent rates do not require a very high airspeed. In the AF447 accident similar rates of descent were achieved and maintained throughout the descent at very low airspeeds. The quoted descent rates are entirely compatible with a recovery from a low airspeed condition.

Besides, according to Inmarsat engineers in the Journal of Navigation "it is prudent to discount the measurements between 18:25:34 and 18:28:15 inclusive, and the one at 00:19:37."

EDIT 2:
ALSM wrote: "With no pilot intervention, there is no AP or AT control after the second engine flames out, even after the APU starts. " Since my reply has mysteriously disappeared, I repeat that ALSM's observation confirms the system operation as I described it earlier.

Last edited by Gysbreght; 23rd Aug 2015 at 16:21. Reason: EDIT 2
Gysbreght is offline  
Old 23rd Aug 2015, 16:07
  #593 (permalink)  
 
Join Date: Jul 2010
Location: Valencia, Spain
Age: 77
Posts: 29
If a plane is descending in an uncontrolled unpowered spiral it is likely to also be slipping and only pressure ASIs will work but any slip may cause them to underread considerably. Can a simulator take this into account? I doubt it since such a condition would be outside the scope of using a simulator.
Ka-2b Pilot is offline  
Old 23rd Aug 2015, 16:19
  #594 (permalink)  
 
Join Date: May 2014
Location: Colorado
Posts: 17
Gysbreght:

You have taken my comment completely out of context. Yes, it is true that 447 and 8501 both demonstrate that a high descent rate is possible with a low forward airspeed. In those cases, a pilot was causing the planes to stall. But I was clearly referring to the case we observed in the simulator, where the speed was observed to exceed the instrument limit (500kts indicated), and no human was in control. Both the vertical speed (descent rate) and the forward airspeed observed in the simulator were consistent with the Inmarsat BFO observations, and that is factual, notwithstanding Inmarsat's reluctance to accept the final two BFO values (even though they do accept the other 500+ values used in the analysis). The only reason Inmarsat was initially reluctant to accept those values was that, at the time, they did not fully understand the implications of the uncompensated vertical speed on the AES Doppler compensation. Victor I pointed this out very early (June 2014 I believe), and ATSB later came to be somewhat more inclined to believe these numbers.
AirLandSeaMan is offline  
Old 23rd Aug 2015, 16:22
  #595 (permalink)  
 
Join Date: Mar 2002
Location: Florida
Posts: 5,207
Lemain

Any simulator should behave the way the aircraft manufacturer designed the aircraft to work and how they believe it does work as built. MH370 is so bizarre with no really credible or incredible (except aliens?) explanation I question whether we should place total confidence on the sim for this disappearance.
I'm not sure what your point is in bringing this statement about simulators?

Any simulator is limited by both the assumptions of the designer as well as the limits of its manufactured fidelity. They do a fair job in training (a long way from being exactly true under all combinations) I would trust the simulator up to the point of upset within normal operating limits, but nothing more.
lomapaseo is offline  
Old 23rd Aug 2015, 17:21
  #596 (permalink)  
 
Join Date: Mar 2014
Location: Maine USA
Age: 77
Posts: 199
Such a scenario is consistent with the final BFO values that correspond to ~4500 ft/min descent rate at 00:19:29 and 15,000 ft/min at 00:19:37.
FWIW, the acceleration in the descent rate between :29 and :37 averages out to ~22 ft/sec/sec, close enough to 1g (~32 ft/sec/sec) to suggest near free-fall.

However, take the calculation with a grain of salt:

Besides, according to Inmarsat engineers in the Journal of Navigation "it is prudent to discount the measurements between 18:25:34 and 18:28:15 inclusive, and the one at 00:19:37."
PersonFromPorlock is offline  
Old 23rd Aug 2015, 17:32
  #597 (permalink)  
 
Join Date: May 2014
Location: In thin air
Posts: 186
close enough to 1g (~32 ft/sec/sec) to suggest near free-fall.
Actually a near zero-g push-over by an absent crew.
EDIT: Or 70 degree bank without a pilot pulling g?

Last edited by Gysbreght; 23rd Aug 2015 at 17:45.
Gysbreght is offline  
Old 23rd Aug 2015, 17:55
  #598 (permalink)  
 
Join Date: Jan 2015
Location: Near St Lawrence River
Age: 49
Posts: 198
At 00:19, the aircraft had been airborne for 7 hours and 38 minutes and fuel exhaustion was a distinct possibility. When a fuel tank was depleted, the corresponding engine would ‘flame-out’
https://www.atsb.gov.au/media/566832..._30jul2015.pdf

This suggest that the pilots were unconscious at that time, since one would not wait for complete fuel exhaustion before attempting a perfect ditching on the first try

According to Jean-Paul Troadec, former chairman of the Investigation and Analysis Bureau (BEA), the state of flaperon, even if it is not intact, indicates that there is no violent impact with the surface of the ocean. "If this had been the case with the MH370, one would have expected much smaller debris than this flaperon"
MH 370 : à Balma, l'enquête technique est bouclée - 21/08/2015 - ladepeche.fr

A non violent impact or a "Sully ditching" would imply a calm sea, nose-up attitude between 5 and 10 degrees and low rate of descent. That could only be achieved with the slats and flaps extended. Well, the flaps could be extended only with the engine running and the flaps lever manipulated consciously. With flaps extended, the dihedral angle increases, therefore the aircraft's lateral stability improves considerably, so the aircraft would not get into a spiral dive, even for 7 hours.
_Phoenix is offline  
Old 23rd Aug 2015, 18:05
  #599 (permalink)  
 
Join Date: May 2014
Location: In thin air
Posts: 186
A non violent impact or a "Sully ditching" would imply a calm sea, nose-up attitude between 5 and 10 degrees and low rate of descent. That could only be achieved with the slats and flaps extended
I agree that a "Sully ditching" requires a conscious pilot and a benign seastate. Furthermore, that pilot must be able to think beyond normal procedures and to anticipate what is required for a successful ditching with engines out. However, a nose-up attitude between 5 and 10 degrees and low rate of descent can be achieved with the slats and flaps retracted.

Last edited by Gysbreght; 23rd Aug 2015 at 18:15.
Gysbreght is offline  
Old 23rd Aug 2015, 18:14
  #600 (permalink)  
 
Join Date: May 2014
Location: Colorado
Posts: 17
FTR...The actual computed acceleration value was 0.68 Gs. There is no point debating the precise accuracy of these numbers. The only important take-away is the fact that even if the 2 final BFO numbers are off some, say 20 or even 50 Hz due to unaccounted for error, the descent rates implied by the final 2 BFO values are very high, exactly as we observed in the simulator. In addition, via pvt correspondence with a high level official at ATSB, I learned that Boeing observed similar post fuel exhaustion descent profiles.

One more point: There is not a single piece of evidence or theory that has been suggested to explain why the final 2 BFO values would not be as good as all the others used in the analysis by Inmarsat, ATSB, the IG, and everyone else that has modelled the path. There were relatively small BFO errors at 16:00 immediately following that reboot (~17 Hz) and we suspect a similar level of error likely immediately following the 18:25 reboot, but compared to the ~250 Hz change at 00:19:37, a post boot up error of 17 Hz or so is insignificant in the bigger picture: It was descending very fast!
AirLandSeaMan 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.