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

BA056 JNB-LHR Incident.

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

BA056 JNB-LHR Incident.

Old 16th May 2009, 09:30
  #61 (permalink)  
 
Join Date: Apr 2005
Location: UK
Posts: 459
Likes: 0
Received 0 Likes on 0 Posts
A few points.

1. Gear up selection will increase drag for a little while, but very soon after drag will be back where it was before and then a big reduction in drag as its all stowed away, times like this you want all the 1 and 4 EDPs and demand pumps plus all eng bleeds in working order, strange fact is the operation of the L/E will be using bleed air that the demands would like very much at that time
.
2. Gear up selection will also give a little pitch down effect, may of been a good thing on said flight.
.
3. Leaving gear down in case ground contact is made may be good in some events like a G/A, leaving gear down in this event may or may not have been good, had gear of made contact again, story could have a different ending.
.
End result was very very good, well done to all.
Joetom is offline  
Old 16th May 2009, 11:53
  #62 (permalink)  

Controversial, moi?
 
Join Date: Oct 2000
Location: UK
Posts: 1,606
Likes: 0
Received 2 Likes on 1 Post
Here we go with blow by blow analysis of what would or would not have been the best course of action before we know EXACTLY the sequence of events.

Whether they raised the gear or not I have no idea but in light of the above post if you ever watch a jumbo retract its gear it is not by any means a rapid process. It is a fact that raising the gear increases drag when the gear doors are opened during the retraction sequence and so the statement above that the aircraft would benefit from the ultimate drag reduction is fanciful if you have crashed in the meantime.

The basic facts are known, the crew flew the aircraft to a satisfactory outcome and speculation about what they should or should not have done is a waste of time until the full report is eventually published.
M.Mouse is offline  
Old 16th May 2009, 12:37
  #63 (permalink)  
 
Join Date: Apr 1999
Location: UK
Posts: 1,691
Likes: 0
Received 0 Likes on 0 Posts
IIRC there's rising ground beyond the end of the runway at JNB. If you can't climb with the gear down I'd say it's better to take a temporary sink over the flat ground and get the gear up than dogmatically stick to SOP and fly level into the approaching terrain!
Carnage Matey! is offline  
Old 16th May 2009, 13:04
  #64 (permalink)  

the lunatic fringe
 
Join Date: May 2001
Location: Everywhere
Age: 67
Posts: 618
Likes: 0
Received 0 Likes on 0 Posts
At JNB as you get airborne, in the dark, the end of the runway is already behind you. Typically V2 is 180kts. Ground speed is well over 200mph. With the nose rotating to 13 - 15 degrees, all you can see out the window is inky blackness. So it is very quickly onto instruments.

Simply put, you are out over the bush at about 100' doing 195kts, climbing. It is an interesting debate about the gear. The 744 had not stalled. It had a stick shake. So was close to a stall. With the gear now moving up you get a drag increase from the doors. No lift reduction. The gear does not affect the lift the wings are making. With the engines being fire walled, the drag increase is more than accounted for. The assumption in that statement is that they would have been using reduced thrust. It would be very unusual if they were using full power at JNB.

Wheels up or wheels down sinking into the veldt at 240mph is catastrophic. So the only reason not to raise the gear is the one of the doors, and the resulting drag increase. We could sit and debate endlessly whether the wheels should or should not have been left down, but what we do know is that the gear came up, and they flew it away to a safe outcome. So on some level, if not on all levels, the crew made the correct call.
L337 is offline  
Old 16th May 2009, 13:10
  #65 (permalink)  
 
Join Date: Apr 2008
Location: Paris
Age: 74
Posts: 275
Likes: 0
Received 0 Likes on 0 Posts
Simulate gear up drag?

There seems to be considerable debate about whether it is better to increase drag temporarily by raising the gear, or not - maybe this issue is deserving of simulation as an answer cannot be arrived at intuitively?

Edmund
edmundronald is offline  
Old 16th May 2009, 13:35
  #66 (permalink)  
 
Join Date: Dec 2003
Location: Tring, UK
Posts: 1,835
Received 2 Likes on 2 Posts
I think this discussion shows that you can't write SOPs for every conceivable occurrence and that Airmanship is thankfully still alive and well in some quarters.

I'm sure at the back of their minds was the possibility of needing to rapidly shut down an engine if it actually went into reverse (very unlikely, even at that stage, but...) and having the gear down at that point wouldn't be a great help.

The same sort of thing could be said of the BA38 double engine failure on short finals: the QRH is written assuming that there's reasonable time available for relights, not that you're going to be on the ground in 40secs...
FullWings is offline  
Old 16th May 2009, 15:41
  #67 (permalink)  
 
Join Date: Mar 2002
Location: Florida
Posts: 4,569
Likes: 0
Received 1 Like on 1 Post
There seems to be considerable debate about whether it is better to increase drag temporarily by raising the gear, or not - maybe this issue is deserving of simulation as an answer cannot be arrived at intuitively?
It's a simple calculation in a performance deck if you have access to somebody who knows
lomapaseo is offline  
Old 16th May 2009, 18:54
  #68 (permalink)  
 
Join Date: Sep 2007
Location: Hongkong
Posts: 202
Received 1 Like on 1 Post
In the windhsear and gpws situation greater minds have determined that there should be no change in configuraton until the warnings have stopped and you're safely climbing away, gear doors produce drag...so 99% of the above is . Some infromed comment would be good...just occasionally
Sygyzy is offline  
Old 16th May 2009, 20:56
  #69 (permalink)  
 
Join Date: Dec 2003
Location: Tring, UK
Posts: 1,835
Received 2 Likes on 2 Posts
There seems to be considerable debate about whether it is better to increase drag temporarily by raising the gear, or not - maybe this issue is deserving of simulation as an answer cannot be arrived at intuitively?
It's a simple calculation in a performance deck if you have access to somebody who knows
...and can run the figures with 2/3 of the LEDs retracted...

There is the possibility that they might have needed to accelerate in ground effect before climbing, given that they were close enough to max AoA in the config. they found themselves in to trigger a stick shake. A few seconds thought (which is all they had) might have led to the conclusion that this would be easier/more effective with the wheels up?

In the windshear and gpws situation greater minds have determined that there should be no change in configuration until the warnings have stopped and you're safely climbing away, gear doors produce drag...so 99% of the above is...
I think leaving the gear down in those scenarios is more to do with possible ground contact during the recovery than with drag. If you give the terrain a glancing blow with the undercarriage rather than the engine pods, it may produce a better outcome. Keeping the wing the same section allows for a better initial ROC in the GPWS instance and a better climb rate/gradient in windshear.
FullWings is offline  
Old 16th May 2009, 21:26
  #70 (permalink)  
 
Join Date: Dec 1998
Location: UK
Posts: 289
Likes: 0
Received 0 Likes on 0 Posts
But the take-off sop is positive climb, gear up. So they may have already selected gear up before the stick shaker activated, or at the least have called for it's selection. They were faced with an unusual situation and dealt with it very well.
Propellerhead is offline  
Old 17th May 2009, 06:39
  #71 (permalink)  
 
Join Date: Apr 2004
Location: Planet Earth
Posts: 2,087
Likes: 0
Received 8 Likes on 7 Posts
SMOC, your solution (locking the LEDS) with the thrust levers in the forward position seems a good one.


Can anyone speculate as to why this is not done ?
stilton is offline  
Old 17th May 2009, 10:31
  #72 (permalink)  
 
Join Date: Dec 2003
Location: South of Watford
Posts: 147
Likes: 0
Received 0 Likes on 0 Posts
Perhaps because it would require one more layer of interlocks (and associated drills) which may cause problems when you wish to retract the flaps/slats after a normal takeoff ?
Sir Richard is offline  
Old 17th May 2009, 22:15
  #73 (permalink)  

the lunatic fringe
 
Join Date: May 2001
Location: Everywhere
Age: 67
Posts: 618
Likes: 0
Received 0 Likes on 0 Posts
Sygyzy:
In the windhsear and gpws situation greater minds have determined that there should be no change in configuration until the warnings have stopped and you're safely climbing away,
Um, No windshear. No gpws. They had a stall warning. Out over the bush in Africa. Doing 195kts. Climbing. They selected full power.They climbed away and landed with no trauma.

I would like to think that my comments were informed. I am a 744 Captain. I have over 5000 hours on the beast. And, to date, have managed not yet kill myself or any passengers. I am more than happy to admit my view of the incident is wrong. But your erudite post has yet to convince me.
L337 is offline  
Old 17th May 2009, 23:24
  #74 (permalink)  

Controversial, moi?
 
Join Date: Oct 2000
Location: UK
Posts: 1,606
Likes: 0
Received 2 Likes on 1 Post
Presumably a stall warning indicates the aircraft is approaching the stall. What are the standard stall recovery actions on the BA B747?

My manuals for the B777 categorically state do not alter the aircraft flap or landing gear configuration so does the B747 uses different procedures?
M.Mouse is offline  
Old 17th May 2009, 23:54
  #75 (permalink)  
 
Join Date: Jun 2001
Location: Peripatetic
Posts: 81
Likes: 0
Received 0 Likes on 0 Posts
My immediate concern is how the false reverse signal was generated on two of the engines. If this can be identified accurately and resolved then hopefully it renders the speculation about gear doors at 200 feet redundant. I would say RFI is a strong contender.
bobmij is offline  
Old 18th May 2009, 00:20
  #76 (permalink)  

Controversial, moi?
 
Join Date: Oct 2000
Location: UK
Posts: 1,606
Likes: 0
Received 2 Likes on 1 Post
The stick shake occurred at 12.5 feet radio.
M.Mouse is offline  
Old 18th May 2009, 02:04
  #77 (permalink)  
 
Join Date: Nov 2004
Location: Edmonton, Alberta
Posts: 17
Likes: 0
Received 0 Likes on 0 Posts
L337

Out over the bush in Africa.
Not too much bush at Joburg mate. But, as a matter of interest, what role did the runway they took off from play in the positive outcome of the event? The ends of the 21's appear to be more forgiving than those of the 03's.

BTW, I'm no pilot, only a humble chemist.
Gigajoules is offline  
Old 18th May 2009, 06:48
  #78 (permalink)  
 
Join Date: Apr 1999
Location: UK
Posts: 1,691
Likes: 0
Received 0 Likes on 0 Posts
It was a departure off the 03s.

M. Mouse - what the B777 manual says is irrelevant. The B744 has a procedure for stalls and a procedure for double engine failure, but not one fir both events simultaneously on departure. It would appear in this case the crew decided that cleaning up in case of the need to shut down one or more engines with deployed reversers was the priority over the stick shake and that demonstrably worked. The aircraft will fly just fine on the threshold of the stick shaker. It won't fly with two engines out and the gear down. Think Concorde.
Carnage Matey! is offline  
Old 18th May 2009, 08:38
  #79 (permalink)  
 
Join Date: Dec 2003
Location: Tring, UK
Posts: 1,835
Received 2 Likes on 2 Posts
It would appear in this case the crew decided that cleaning up in case of the need to shut down one or more engines with deployed reversers was the priority over the stick shake and that demonstrably worked. The aircraft will fly just fine on the threshold of the stick shaker. It won't fly with two engines out and the gear down. Think Concorde.
Makes a lot of sense. It probably wouldn't have taken much of a reduction in pitch attitude for the aircraft to make ground contact and I expect that would have been beyond the end of the paved surface...

They seem to have ended up in a similar situation to the EK flight out of MEL, i.e. passing the end of the runway in an aircraft almost too heavy to fly in its current configuration, only for completely different reasons. At that point, SOPs get put to one side and as our colleagues from the USA would say, the only option left is to "fly the airplane". Well done.
FullWings is offline  
Old 18th May 2009, 08:56
  #80 (permalink)  

the lunatic fringe
 
Join Date: May 2001
Location: Everywhere
Age: 67
Posts: 618
Likes: 0
Received 0 Likes on 0 Posts
This is a direct quote from the Boeing 744 QRH.

Procedures Beyond the Scope of the QRH

Introduction:

It is rare to encounter inflight events which are beyond the scope of
established non-normal procedures. These events can arise as a result of
unusual occurrences such as a mid-air collision, bomb explosion or other
major malfunction. In these situations the flight crew may be required to
accomplish multiple non-normal checklists, selected elements of several
different checklists (applied as necessary to fit the situation) or find little
or no specific guidance and need to rely on their own judgement and
experience. Because of the highly infrequent nature of these occurrences,
it is not practical or possible to create definitive flight crew procedures to
cover all events.
To have Engines 2 and 3 REV "Amber" (unlocked) warning lights, then have the inboard and mid LE slats retract, and then have a stall warning at rotate is beyond the scope of the QRH. This scenario is not something that forms part of any check or training in the simulator. The situation required them to rely on their own judgement and experience. There is no definitive flight crew procedure for the combination of events they were presented with.

They had no time to diagnose, they had no time trouble shoot, they were straight into "mitigate".

As we know they elected to raise the gear. They also landed safely, and nobody got hurt.
L337 is offline  

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.