Posts about: "Gear Retraction" [Posts: 243 Pages: 13]

Still no one talking about the landing gear position?

A 787-8 with the landing gear down should have the bogey tilting upwards. Clearly in the video, the bogey is tilting downwards, which would indicate something on the aircraft is not working 100% as it should.

I know the -9 and -10 have a different landing gear retraction sequence with gear doors etc etc, but watch any normal 787-8 take off and look at the angle of the MLG bogeys and compare the the incident video.

The aircraft can still climb away with the gear down albeit at a slower rate. The TOGA switch is used on the ground to take off. Take Off Go Around. The autothrottle can be overridden by pushing the thrust levers forward and holding or by disconnecting with switches on the thrust levers.

Although the gear bogie isn\x92t in the initial post-liftoff position, if you can see the retraction mechanism operating in a 787 It first tilts the bogie forward. I\x92d therefore consider that a \x93gear up\x94 switch was activated but the action failed \x97most likely due to hydraulic pressure loss. In the second video (left-side view), I could interpret that gear retraction begins around 24 s and then halts before 27 s, exactly when the aircraft stops climbing.

Just my two cents, from the perspective of an aircraft engineer with a background primarily in Airbus.​​

Let\x92s be careful about absolutes. Emirates 521 and Turkish 1951 are both examples of crews not firewalling the thrust levers despite low energy. The late pitch up could be due to the onset of a stall not an order from the crew.

TCMA is function which can reduce thrust on both engines simultaneously. It had done so in error in the past resulting in an AD. It uses air/ground logic so that it only operates on the ground, however note that at the point of thrust loss the gear is still down without any movement of the gear or doors. I would expect gear retraction to start before that height. Could we imagine an air/ground logic fault inhibiting gear retraction and allowing TCMA, which triggered (for whatever reason!) causing dual thrust loss? I would expect this to be in the realms of a combination of failures shown to be extremely impossible, but\x85

Firstly, I don\x92t think an inadvertent selection of flaps up caused this accident. I think it\x92s a red herring that seemed plausible initially but it is not consistent with the RAT being deployed, and the evidence for the RAT is strong.

To answer your broader question though, how could such an error happen? It happens because us simple humans learn how to do actions to the point where we don\x92t have to think about them anymore. This allows us to effectively automate routine tasks and save our brains for more novel tasks. The problem arises when we trigger the wrong automatic action in response to a cue. You ask for gear up, I know I need to select the gear up, I know where the gear handle is and what it looks and feels like, yet something goes wrong in the wiring of my body and instead, the flap-up automatic action is run. It\x92s run before I have consciously thought about it.

Sound far fetched? Well it has happened numerous times. I\x92ve seen someone do exactly that, select the flap instead of the gear, and there are incident reports publicly available. All modern passenger jets have a similar layout of the flap lever and the gear lever with the gear looking like a wheel and the flap looking like a wing, yet this error can still happen.

Have you ever gone to put something in the fridge that should\x92ve been put in the cupboard? I\x92d bet that most people have made that weird error at some point in their lives, and yet the fridge doesn\x92t look like the cupboard and they\x92re nowhere near each other.

Having experience of many crash sites over a long career, taking off without flaps with the config horn/ warning blaring (or not if u/s) is a possibility Also selecting flaps up, instead of gear up at the positive rate of climb call, is also not unheard of and has happened. Both engines failing/ losing power at rotation/ initial climb out would be extremely rare, but not impossible. With the descent and lack of climb clear, unless a mistake of retracting flaps instead of gear, why wasn't the gear selected up as dragging that around is only going to end one way.
he sound from the well documented video would suggest the engines were running, but were certainly not selected to TOGA/ full power which you might expect when faced with high buildings growing larger in the windshield.
Due to the tail section being relatively intact, the CVR/ DFDR will be downloaded very soon, if not already, so we will all know shortly....

that\x92s why the switches and levers are designed like this. The gear lever is round like a wheel and the flap lever is, well flap shaped. Mixing up switches was/is common. Happened to me in my training pulled the mixture full out instead of carb heat on my approach. Immediately realised the change in the engine and pushed it back in before it cut out completely and engine started up again. Change of underwear required.

In of a 787 take-off, first the inner main landing gear bay doors open, and then the bogies tilt downwards. In the first video of the crash, the bogies appear to be tilted downwards but said doors remain closed?

early doors then after a certain time they close. Or gear left down for brake cooling in the MEL

That is a -9. On -9 and -10s the inboard gear doors open at lift off automatically without gear up being selected. The accident aircraft was a -8 and does not have that feature. Main gear bogies tilt nose down, then gear doors open, then retraction as seen in this video

The video of the crash shows the gear tilted down, which should mean gear up was selected, however something kept the sequence from continuing (loss of hydraulic pressure for example).

Discussed here

And another: https://www.gov.uk/aaib-reports/aaib...319-111-g-ezew

In an Airbus the flap lever is even further away from the gear lever than in any Boeing, yet still it happened! Action slips are just that and to blindy say that moving the flaps before gear is impossible, just because they are in a different location is incredibly naive. Next time you pour orange juice in your tea because you were thinking about something else and grabbed the wrong carton will you decry it impossible?

To be as crystal clear: I am not saying this is how it happened, but it could be. Just as other things could be.

Brakes would be hot at that ground temp . Long taxi , back track and turn , turnaround time may have been short enough to have residue heat in brakes ? Do they have brake fans , or portable brake fans . If no terrain issue then maybe gear down was planned to let brakes cool ?
Any change to normal flow and having to remember things are different can cause issues . ie triggered to put something up after take off ?

Was wondering about this since bogie attitude was first mentioned a while back. Perhaps someone familiar with the electrical/hydraulic aspects of main retraction on a -8 could comment on what (or loss of what) would prevent the sequence from continuing.

Here is another video.


At 0:21 to 0:22, there appears to be an odd yellow flash around the #1 engine. This may of course also be due to the rather bad, filmed-off-a-screen video, but it occurs after liftoff and around a time when gear retraction would be appropriate.



Edit: here is another video showing the same scene in slightly better quality. The same flash is visible around 0:46.

This does not necessarily mean anything, of course, and it may as well be some reflection of the sun, but it appears to be about at the time a total power loss would have brought the known results.

In summary,

Flaps were extended, possibly flaps 5 or 15. Looks like it in the video and clearly shown post crash.

Aircraft reached a height of just over 100\x92 AGL (possibly 200\x92 if you compare wingspan to height in videos)

RAT was deployed. Seen on videos and heard conclusively.

Aircraft rotated at \x91usual\x92 spot. Comparing FR24 data from previous flights over the past week.

Aircraft took off at \x91usual\x92 speed. Comparing other flights.

FR24 data stopped being sent shortly after take off. Possibly indicating electrical fault.

Green and white flashing light reported by survivor. Possibly indicating electrical fault.

Gear bogies were at unusual angle indicating Gear selected up and then interrupted.

No smoke or flames to indicate bird strike. (Edit - still debate about this in the video above where the aircraft is behind a building)

No rudder input to indicate single engine failure.


All speculation but hopefully a pretty balanced summary from the thread so far. It would be great if there was more focus now on what might have caused above rather than talking flaps, birds, 625\x92, etc.

I have now watched a number of "normal" 787 takeoffs online and in none of them does the gear go up super early, certainly not before the 10 seconds or so where this one seems to loose power. I think the flap/gear raising is wrong personally

You're right it is frightening. In this instance they didn't avoid a sink did they and the nose wasn't raised. Flaps add drag, OK not much at a takeoff setting but a little. If you retract them without changing power and without increasing climb, speed will increase. It's physics. This plane started descending. You think a plane retracted flaps, started descending and in the process lost around 60 knots (probably more actually, that's based on an average). Also the landing gear actually appear to just start the retraction process, the bogies tilt up which is the first phase, and then it suddenly stops. So that rules out 'pulling the wrong lever'.

So much confirmation bias here. A lot of people settled on flaps being the cause at the start and are now completely blind to all the overwhelming evidence saying it had nothing to do with flaps. I don't blame you, even professionals in critical jobs fall victim to it, see various miscarriages of justice after police got fixated on one suspect and refused to accept all following overwhelming evidence to the contrary. Hopefully air crash investigators are a little more open minded, and not quite as determined to blame the dead guys.

With respect I can\x92t see that the two videos we have available to us as primary evidence are sufficient to draw any conclusions, they certainly don\x92t provide overwhelming evidence of anything other than the aircraft crashed with the inevitable horrendous consequences. Although I stand by my unsubstantiated theory that this was a flap/config issue of some sort, I\x92m only basing this on the scant evidence available publicly and I certainly aren\x92t resting my hat on it. Very much expect that there may be a root cause that nobody expects or there may be many factors at play here that have allowed the holes to match up.

One thing is for certain though and that is that, due to the number of 787 aircraft in service and the ominous nature of the event, we may see preliminary findings released fairly swiftly.

Hmm that's VERY interesting. Amazing we've all missed it, here and everywhere else I've been reading. It's certainly right about the time we'd expect something to happen to the engine, so it's a remarkable coincidence if its not related. Hmmm.

Misselection of flap, erroneous TO Performance data, dust = overrun, bird strikes\x85.all unlikely as none fit the evidence; the engines were very quiet.

The clearest bit of evidence is the RAT deployment. As someone else pointed out gear bogey position indicates Gear UP cycle had commenced.
So the most evidenced sequence of events was rotation, positive rate = gear Up; \x85.catastrophic Power Loss. Flickering cabin emergency lights and Loud bang reported by survivor (was this heard RAT deployment or another system?).

The 787 has some unique electrical/mechanical and air systems. Previous flight had issues (reported by passengers).

So the root cause of the Power failure must be down to when either the 787 gets airborne (weight on wheels switch) or when Gear selected Up. I wonder if any 787 drivers could elaborate on what electric/hydraulic/air systems are affected at the very point of wheels up or gear up ?
I\x92m wondering if the electrically powered cabin pressurisation system is affected at wheels up?