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BA056 JNB-LHR Incident.

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BA056 JNB-LHR Incident.

Old 19th May 2009, 14:52
  #101 (permalink)  
 
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Willit Run

How much are you prepared to bet??
Group A retracting on the take off roll and stick shaker as soon as air/ground sensing signals weight off wheels.
B73
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Old 20th May 2009, 10:33
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Ladies &/or gentlemen, there's a part of this story I've not seen mentioned here yet that happened after the initial emergency was over and the aircraft was safely up in the air.

I'm not prepared to say owt yet until I'm sure I won't be dropping someone in deep poo, but do keep an ear out for something that took place before the aircraft landed again.

As an aside, it's nice to see that you professionals can bitch and snipe at each other the same way members of music, photography and motorcycle forums do.

Cheers all,

A fare paying passenger.
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Old 20th May 2009, 12:15
  #103 (permalink)  
 
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A wild guess to i sit in the back on your 1st post, aircraft headed for London as is normal on that route, after some time, Joburg was selected as next landing, fuel was off loaded during flight, aircraft then landed back at Joburg, appears a great job was done by all.

But if you know different, please tell !
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Old 20th May 2009, 20:13
  #104 (permalink)  
 
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I can't wait for this.............. spill the beans then sit in the back. The FDR and CVR have been back in the UK for a week, what do you know that BA/CAA don't???
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Old 20th May 2009, 22:54
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I see an Emergency AD coming out as a result of this. From all the posts looks like the aircraft did as designed. Well of course except for it happening in the wrong flight phase!

I appreciate also the reason behind the thrust rev amber indication needs to be fully investigated but the config change to the aircraft is the more pressing issue.

I would imagine a interim measure which would call for the deactivation of the auto flap function for the LEDs then in future a modification that would incorporate throttle lever position into the logic that the FCUs use for the auto flap function. But both of these would take some time to produce the necessary Service Bulletins.

As an engineer I could see a short term fix to prevent the change in config that this aircraft suffered from and that would be to arm the alternate flaps during the take off roll. Then once in the air deselect and operate the flaps normally.
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Old 21st May 2009, 08:21
  #106 (permalink)  
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jimpy

Would it be possible to programme the FCUs so that the auto function of the LEDs is only active when either flap 25 or 30 is selected?

Dave
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Old 21st May 2009, 17:53
  #107 (permalink)  
 
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Any chance you could tell "I sit in the back" that he has failed his probation on the grounds of being ludicrous and ban him.
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Old 21st May 2009, 20:27
  #108 (permalink)  
 
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B747-200 OA411 - Gear retraction during stall

Regarding the issue of the drag effect of the landing gear doors opening up during gear reatraction, I think that many people are unaware of this old, very similar, incident of Olympic Airways back in the 70s with the 747 classic.

On 12-8-1978 the OA411 flights from Athens Hellinicon (LGAT) airport experienced an engine flameout (engine two) during takeoff (at v1).
Additionally even though the takeoff procedure included the use of "water methanol injection" providing additional thrust during the very hot Athens august afternoon, due to cockpit miscommunication, the flight engineer turned off the injection just around V1.

The airplane eventually took off at Vr at the end of the runway just barely managing to pass the first hill (209ft) at 215ft (climb rate less than 200ft/min). During climb, engine 3, also suffered damage and become inoperational.
Under pilot's orders, the landing gear was not retracted due to the fear of drag from the huge landing gear doors opening. This was against company SOPs.

He continued on a level flight aiming for the nearest uninhabited hill near Piraeus but the flight engineer did manage to get a bit more power, thus increasing IAS and letting him reach the sea where he began dumping fuel and eventually retracting the landing gears performing a successful go-around.

Boeing did run the scenario many times in simulators all resulting in a crash ...
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Old 22nd May 2009, 03:35
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If memory serves me correctly, it was British Airways which was involved in a similar incident many years ago.

A foreign object (manual?) had been left just forward of the thrust quadrant prior to departure. When the TOGA switches were pushed, the thrust levers advanced and the reverser knobs struck the object pushing them upwards.

There is a mechanical interlock which prevents the reverse levers moving upwards to reverse idle with the forward thrust levers more than a few degrees from idle. However, the reverse levers do move upwards a little bit (6 degrees or so). This is enough to trigger the first set of switches for reverser activation (and the LE flaps). Or rather, it used to be. An Airworthiness Directive and an associated Service Bulletin (SB 747-27A2356) was raised to modify/change some components to make the activation of this first switch set occur at 10 or so degrees rather than 6 degrees. The reverser levers will not physically move to 10 degrees with the forward levers out of idle.

Can't find the link I was looking for, but the following is related to this incident:

Airworthiness directives: Boeing, - Federal Register, November 25, 1998 (Nbr. Vol. 63, No. 227) - vLex

Rgds.
NSEU

Last edited by NSEU; 22nd May 2009 at 03:50.
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Old 23rd May 2009, 11:58
  #110 (permalink)  
 
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KISS

Instead of adding further complexity to the system why not just lock out the L/E auto-retract feature? It's there to prevent FOD on landing... how often does that happen in real life and how does that risk compare to what we have just witnessed in terms of likelihood and consequence? Of course it would mean someone actually getting off their bum and doing a PROPER walk round prior to the next departure....

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Old 23rd May 2009, 13:17
  #111 (permalink)  
 
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FOD isn't the primary reason for LE retraction with reverse thrust. The main concern is fatigue due to exhaust impingment on the LE while in reverse.
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Old 23rd May 2009, 13:54
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Old Aero Guy

FOD isn't the primary reason for LE retraction with reverse thrust. The main concern is fatigue due to exhaust impingment on the LE while in reverse.
That makes a lot more sense than FOD. Seeing as it's pretty rare to have enough reverse efflux to lift an object as high as a LE slat except in the rarest of conditions.
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Old 23rd May 2009, 20:42
  #113 (permalink)  
 
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I stand corrected!
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Old 23rd May 2009, 21:00
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The way I see it, LE slats are lift enhancers. If Reverse is selected, I think extra lift might be unnecessary, even counter productive. Stowing all lift enhancers seems a reasonable thing to do when your goal is to slow down. Leaving drag devices deployed likewise seems correct. (Flaps and spoilers).
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Old 23rd May 2009, 21:45
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Imagine the scenario -

On rotation you get the stick shaker and two amber R's (inidcating you have two unlocked reversers).

The crew dont know the inboard and midspan LE devices have retracted ..

It would be extreemly tempting to assume the amber R symbols above the EPR are the problem and call for an engine shutdown ...

The crew did extreemly well ...
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Old 23rd May 2009, 22:15
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The way I see it, LE slats are lift enhancers. If Reverse is selected, I think extra lift might be unnecessary, even counter productive. Stowing all lift enhancers seems a reasonable thing to do when your goal is to slow down. Leaving drag devices deployed likewise seems correct. (Flaps and spoilers).
See it any way you like, but the design purpose of the inboard and mid-span LE devices retracting with reverse selected is to prevent fatigue on said devices. It was never designed as a method lift dumping, at which it would actually be of very limited use (consider the angle of attack of the wing after touchdown).

Imagine the scenario -

On rotation you get the stick shaker and two amber R's (inidcating you have two unlocked reversers).

The crew dont know the inboard and midspan LE devices have retracted ..

It would be extreemly tempting to assume the amber R symbols above the EPR are the problem and call for an engine shutdown ...
A point that cannot be stressed enough. It's all very easy to look at this incident with hindsight and suggest you or I would have acted differently (ie gear up or not) - but in a time limited situation I think they did a fantastic job of prioritizing the flying of the aircraft. Kudos to them.
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Old 25th May 2009, 00:56
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The way I see it, LE slats are lift enhancers.
No, not exactly!

Not in the way that TE flaps are.

They principally extend the lift-curve-slope to higher incidences, but in themselves (at a given incidence) make little difference to lift

Thus at any given incidence, ground incidence in this case, as said, their retraction would make no appreciable difference
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Old 25th May 2009, 01:19
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Boeing 727, Cleveland, crew forgets LE slats on T/O, all dead. No difference?
The shaker on this recent T/O? Explain.

Last edited by Will Fraser; 25th May 2009 at 01:43.
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Old 25th May 2009, 01:46
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Will

Please read what I said carefully... !

AT A GIVEN INCIDENCE

To get the extra lift you have to increase incidence - beyond the max (or stall) incidence without them.. not the case with TE devices

So in themsleves they don't increase lift, but allow for higher incidences without flow breakdown.

The stick-shaker will vary with incidence, depending on the LE device position

Take the Barajas incident... the pilot pulled a (wing) incidence at rotation taking the aircraft into the regime requiring LE slats. They were not deployed -> stick-shaker -> without reduction in incidence -> approach to stall, loss of directional control -> stall. Maybe, if he had taken a less aggressive approach, possibly, he could have fown it off on the shaker, rather than way above. It was the extreme incidence requiring LE devices, that ensured loss of control, not loss or lack of lift per se.

Perhaps a graph showing the effect of flaps and that of LE devices will make it clearer.. a picture is worth a thousand words.

..but its late, my eyes hurt and its time for beddy byes. Ask and it shall be given (later)....

Last edited by HarryMann; 25th May 2009 at 02:00.
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Old 25th May 2009, 01:58
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My point being that altering a wing's camber on T/O will cause havoc if not done with care. I agree with all your points. Slats do ennable Lift, is what I'm sayin. I see it as raising the wing, but effectively lowering the leading edge, creating a stubby high camber high lift wing at a speed the a/c could not otherwise fly at. Are you saying the slats ennable an effective lowering of Incidence, cause that's what I'm saying.
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