L337 - Simply put, you are out over the bush at about 100' doing 195kts, climbing.

Sorry mate := but there is a town called Kempton Park which is north of 03L perimeter, starts around 500m from threshold - stretching 7kms north and around 4-5 kms either side of flightpath out. I live in this town and believe me, this incident has made quite an impact on thousands of aviation/JNB-airport employed people living in this town...:\

Dear me. I retract the word "bush" and would like you all to insert "Kempton Park" in it's place.

The point I was trying to make is that you are not over the runway. So if the you touch down again you are not going to "bounce" off a nice friendly runway. But bounce into "Kempton Park".

It stopped at 32.8 feet radio.

But the key question is what was the time betwen the two heights? I speculate that it was looooonger than normal.

Also, I believe that the raising of the gear resulted in the air-ground logic switching to Air mode, which resulted in the LED's driving to the normal positions by 160ft radio.

It just may be that raising the gear was a superb decision that guaranteed the successful outcome, much as raising the flaps to 20 greatly assisted the outcome for BA38.

M.Mouse said

L337 has beat me to it with a fine explanation:D

Perhaps if you were desperate to know the answer to this question, you could have asked on the BA section of the BALPA forum where there is a long running thread on the JNB incident or indeed the tech part of said forum.

Or perhaps you were afraid that such a question could potentially be observed as a slight to the actions of the crew on the day!

The DFDR will make interesting reading indeed.

Would guess the L/E waited for gear in air mode via the tilt prox sensors/logic, but guess it could be gear leaver position or position of gear.

Question, when L/E deploy, does lift reduce in the early stage on the 747, I would guess it does ? anyone know ?

Da Dog

At no point have I criticised the crew and nobody has actually confirmed whether the gear was raised immediately or not and if it wasn't at what point it was raised. It may well be the case that the stick shake caused them to leave the gear where it was and they then raised it when the stick shake stopped. Plainly whatever the crew did worked.

I do not subscribe to the view that they would have had sufficient time to analyse the situation, decide that they MIGHT have to shut down two engines, and that raising the gear while near to a stall was the lesser of two evils.

The BALPA forum consists of a thread almost entirely composed of unqualified congratulations so hardly the place to discuss the merits of various courses of actions but then it made your attack easier.

Full Wings said:So raise the gear, temporary increase in drag, lower the nose to maintain airspeed, er..........

I'm off. I will just have to learn to blindly praise every perfect crew before the facts are known rather than try and learn from the incident whether anything done was less than optimum, albeit successful, just in case I am faced with the unthinkable which, as has been pointed out, is outside the scope of any known procedure.

M.Mouse,

The point I was trying to make was that, If you had asked the question I referred to on the BALPA forum I am 100% confident that you would have got a swift and concise answer, instead you elect to labour the point on an open, anonymous forum.

I can't think why.

have I touched a nerve?

I have as little idea about what actually happened as the next guy. I am simply glad this incident did not turn into a nasty accident.

Surely you would be unable to raise the gear (without using the over-ride) if the air-ground logic was still in ground mode.

Were the REV indications only present once airborne, or did they show during the takeoff roll? It could be that the inboard and midspan LE flap groups retracted during the takeoff roll, but then re-deployed once the gear tilted as it got airborne? Pneumatic movement of the flaps is relatively quick, but would still not be in position for a short period of the initial airborne time (during which the stick shaker would likely activate).

A swift and concise answer on the BALPA forum? I am still laughing at that one.

Nope. Just when attacks get personal it is time to go.

I am sad for you M.Mouse that you hold your work colleagues in such low esteem, I know of many high caliber trainers who would have been happy to answer your question either in public or with a private message.;)

However I suspect you already knew the answer;)

The auto retract of the l/edge flaps is only armed on the ground. Therefore when the aircraft became airbourne this signal from the Thrust Reverse relays would have been lost and the l/edge flaps would have deployed again.

About 10 secs for L/Edge flaps to transit, and (from memory) about 16 secs for the gear to (physically) transit. (a little bit longer for the EICAS indication).:8
GS-Alpha see post 17:ok:

M. Mouse - have you flown a jumbo or other heavy four engined aircraft? Perhaps you are used to flying a twin around where the potential loss of 50% of your thrust is no great problem. You don't need me to tell you that it's different in a jumbo. You are implying the crew responded in Pavlovian fashion, raising the gear simply because that's what they always did with no thought I'd analysis. I suspect any competent 744 crew on seeing 2&3 rev amber after V1 can make a pretty good snapshot call as to what the biggest threat to the aircraft was. If you had two unreliable engines on your 777 after take off would you faff around with a T-DODAR trying to work if raising the gear would help I'd hinder?

Aircraft due to leave JNB later this evening to ferry back to LHR. Both nos 2&3 reversers are/will be locked out!

Let a just culture prevail:ok:

Let's not rush to judgement or excessive praise, and take the 'no blame' route.

That said, if anyone can let me know the tail number of a/c in question I think I'll let it do a few sectors without me!

Sir George Cayley

I read PPRuNe in the hope of learning what I didn't know I did not know. And whenever I am lucky enough to find the limits of my knowledge before they bite me, I return to my company issued Boeing 744 CD-rom, a poor cousin to the erstwhile manuals.

I also read PPRuNe in the hope of re-learning what the passage of time has caused me to unwittingly and unwillingly forget. There's been a lot of forgetting going on in my overfull, greying head lately.

A few critical points have been taken from this very important thread:

One is the undeniable fact of it being populated by some very testy and apparently uneducated people on the matter of aviation who seem uncommonly keen to discredit tried and true procedures, to question proper process, or to nit pick well worded posts written by highly experienced pilots commiting the inexcusable crime of not naming an obscure and forgettable grouping of dim lights he has overflown on countless departures over the wider bush that is Africa.

Another is that the BA036 crew did an outstanding job.

Most importantly, my thirst for knowledge has been reinvigorated by a sense of self preservation. Fate is the hunter, and though I know the B744 airplane well, I don't know it as well as I'd like. Given it is my chariot in the workplace, I am forced to review my training in the case of being faced with the unthinkable.

I don't know how this incident would have transpired were I on the flight deck any more than I know how this afternoon's flight will ultimately work out until the brakes are set to park on the second and final stand.

Anything could happen, according to Boeing.

Which is sufficient reason to review my CD-rom, hateful disc of plastic that it is; to rely not on prayer but experience, training and a cool head, and to hope that my clear thinking cap with its well receded hairline is firmly latched if and when events become as unpredictable as they did for the BA crew departing Jo'berg.

PW

Well said.

There, but for the grace of God, go us all.

G-BYGA? According to Heathrow & Gatwick Airport Movements it went out on 10 May but didn't arrive back on 12 May.

I would be willing to bet that the gear retraction was in progress when the stick shaker was activated. ONce you notice an increase in altitude from the baro and radio, up comes the gear!

I have seen some mind blowing wierd things happen when moisture condenses on the logic cards. Cool avionics, then a blast of hot humid air , condensation happens.

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

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.

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 !

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???:mad::mad::mad:

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.

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

:E 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.

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 ...

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

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....

Pinkman

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.

Old Aero Guy

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.

I stand corrected!

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).

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 ...

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).

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.

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

Boeing 727, Cleveland, crew forgets LE slats on T/O, all dead. No difference?
The shaker on this recent T/O? Explain.

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)....

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.