Posts about: "Gear Lever" [Posts: 50 Pages: 3]

Incorrect. Aircraft is a 787-8. It is does not have the early MLG door opening feature fitted to 787-9 & -10.

Isn\x92t the gear door feature exclusive to the -9 and -10 variants, not on the -8?

I'm posting some YT-links to show that 787-9 gear doors indeed open on lift-off, while the -8 gear doors open only when gear up is actually selected. I also include links to a 787-8 and a -9 that keep their LG down after departure. The 8 doors are not opening. The 9 doors do open again regardless and indeed close again about 30 seconds after lift-off.

1. 787-8 LG retraction: boogies tilt forward, doors open, boogies tilt inward: 2. 787-9 LG retraction: doors open on lift-off, boogies tilt forward before inward: 3. 787-8 LG kept down: doors remain closed: 4. 787-9 LG kept down: doors open and close again about 30 secs after lift-off:

On item 1, the TCMA issue should have been fixed, it does fit the sort of issue that occurred here. TDRACER can talk to that, and has done in 2019 and again in post 792. As to flap auto retraction, the B787 like all Boeings has a gated flap lever, and the flaps are only able to move independent of the lever by flap load relief. That would not have caused a loss of thrust, and in this case it is evident that the event is a thrust loss not a CL loss.

On item 2, the video shows no asymmetry at any time, so there is only a symmetric failure of the engines possible. Back on a B747 classic, you could chop all 4 engines at the same time with one hand, on a B737, also, not so much on a B777 or B787. I would doubt that anyone used two hands to cut the fuel at screen height. Note, there was a B744 that lost one engine in cruise when a clip board fell off the coaming. Didn't happen twice, and it only happened to one engine.


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Neila83 is correct, the gear tilt pre retraction is rear wheels low, and at the commencement of the selection of the retraction cycle (generally), the first thing that happens is the inboard MLG doors start to open below the wheel well and then the bogie is driven to front wheels low. (There is also an option that the inboard gear doors start to open early as a result of WOW sensing to improve the SSL climb limit). [my bad, for the B788 Capt Bloggs informs us the gear door sequence is after the tilt, not before, the B789 has the before tilt, the option for the door open at rotate is separate]

The inboard doors do not appear to have opened in this case, yet, the gear is forward wheels down. This appears to be out of sequence. TD may have better knowledge on the options that exist with the B788, but this is not looking good at this time.

There is enough in the way of anomalies here to end up with regulatory action, and airlines themselves should/will be starting to pore over their systems and decide if they are comfortable with the airworthiness of the aircraft at this moment. A latent single point of failure is not a comfortable place to be. Inhibiting TCMA might be a good interim option, that system could have been negated by having the ATR ARM switches....(Both)... ARM deferred to the before takeoff checks. The EAFR recovery should result in action within the next 24-48 hours. Boeing needs to be getting their tiger teams warmed up, they can ill afford to have a latent system fault discovered that is not immediately responded to, and the general corporate response of "blame the pilots" is not likely to win any future orders.

I think we are about to have some really busy days for the OEM.


Not sure that Neila83 is that far off the mark at all.

777/787 driver here.

Reading a few posts about an APU-to-pack takeoff, or a packs off takeoff on a 787, because of the hot weather, makes me shake my head.
There is no bleed air on the 787. A packs off takeoff, or an apu to pack takeoff, is never done. There isn’t a procedure in the fcom to describe it. It is also pointless. The packs are electrical.

Then the gear.
When you lift off the runway, the gear doors open REGARDLESS of gear lever position. If you do not raise the gear within 30 seconds, the gear doors close again and you keep the gear down as you apparently desire. In the video, the gear doors are closed again as the airplane flies into the suburb. This requires normal hydraulics in system C, which was apprently available as the doors are closed again.

takeoff performance:
I entered all relevant weather parameters into my performance tool for Ahmedabad VAAH, rwy 23, 42 degrees C and no wind, qnh 1005.
It comes up with flaps 10 as optimum, albeit for a 787-9 (don’t have the possibility to calculate for the 787-8) But even the 787-9 is able to depart with flaps 5 in those conditions. Max tow around 230tons.

I previously speculated the forward truck tilt was proof the gear had been selected UP and the retraction sequence was interrupted.

I’m not so sure now and believe there is a different conclusion from this non-normal gear position.

In normal retraction sequence the gear doors open almost instantaneously after the forward truck tilt. It does seem coincidental the tilt was completed while no indication of the doors opening is visible on the rooftop video, which would suggest hydraulic failure at that exact moment; this precise timing of interruption in the retraction sequence feels unlikely. So is there a more likely answer for the forward truck tilt that does not involve movement of the gear lever?

I suspect it’s more likely that C hydraulics lost power prior to rotation, as a consequence the truck could not tilt rearward during rotation as it normally should. Therefore it’s probable it always stayed in a neutral or forward tilt position from the take off run until we see it in the rooftop video. If the gear was behaving normally, and the crew had omitted to retract, it should be hanging rearwards. Watch any 787-8 takeoff video and you can see at rotation all 4 main wheels stay on the runway as the aircraft rotates. Just after wheels up they tilt rearwards. It’s a very subtle position change.

If the gear was always in a neutral or forward truck tilt position then this undermines the theory that retraction sequence was interrupted. It insinuates the C hydraulic and electrical failure happened prior to main wheels lift off.

For this reason I believe we cannot assume that gear UP was selected nor that retraction was interrupted. I’m seeing lots of social media posts which suggest the forward tilt means gear was in retraction and I don’t believe it was now.

I think the truck tilt position is key to understanding the timeline of system failures and whether the automatic RAT deployment was triggered by power failures or engine(s) failure. The question remains, did loss of center hydraulics happen before or after loss of thrust?

Incorrect. Aircraft is a 787-8. It is does not have the early MLG door opening feature fitted to 787-9 & -10.

I originally was onboard with the truck tilt seen in the one video being proof that the gear handle was selected rather than the flap handle. But after watching several videos and an "endless" web search for info, I also have started to think that there was a problem before the gear handle was moved.

In a normal retraction, the main gear doors begin to open before the truck tilt is complete (roughly when the gear trucks are "level", seen around 8-10 second marks of this video ). The nose gear doors open at the same time the main gear tilt starts (seen in Jetstar video linked below). It's too blurry in the video/stills of the accident aircraft to definitively say the nose doors are not open, but I'd say no. And it's pretty much a certainty that the main gear doors are not open. And finally I think it is also pretty clear that the main gear trucks are tilted down to the retract position.

I have no confirmation of this, but I read (or heard someone say in a video) that the truck tilt actuator was a "single acting" actuator, meaning hydraulic pressure held it in the toe up position and it was spring loaded to the retract position. Which means if hydraulic pressure was lost due to loss of power to the electric driven center hydraulic system, then the main gear trucks would tilt forward on their own without moving the gear handle. The Jetstar burst tire video somewhat backs this up, in that the blown tire caused a leak to the center hydraulic system and an alternate extension was required (thus the reason the main doors are down during the landing). No hydraulic pressure means the main gear trucks remained pointing nose down during the landing. Video here

As a pilot with 40+ years of professional flying, currently on the B777, and with some background in modelling aircraft performance, I've got a few observations, having read all posts.


Flaps & Takeoff

The flaps were out for takeoff, which was normal: normal rotation rate, right place on the runway. Debris also shows the flaps were out at impact. The plane's flight path completely matched what you'd expect from a flight with flaps set correctly.


Flight Controls & Pilot Action

To my mind, the controls were clearly working right up to the very end of that tragic flight. This also strongly suggests the plane never had any asymmetric thrust, because there's no sign of yaw, rudder, or big aileron/spoiler movements. The pilots seemed to guide the plane accurately and consistently, just like an experienced crew would. It looks like they were highly skilled from the start: immediately after rotation, they lowered the nose a bit to keep the plane flying. They also bleed off speed to avoid ground contact. Eventually, with no speed left, the plane descends, but it still looked like they were in control. The instinctive pitch-up right before impact is what a lot of pilots would do.


ANC

Why transmit to ATC ? beautifully described by EGPI10BR


Aviate: The aeroplane has decided it doesn\x92t want to do that any more

Navigate: Not many options on where to go

Communicate: May as well let people know it\x92s going to be a bad day and to get there ASAP.


Booster Pumps

Engines don't actually need booster pumps at sea level to get takeoff thrust. (tdracer)


Restart

There's no noise of the engines spooling up at impact. The mobile phone footage just has the RAT noise, normal airframe sounds, and impact noises. I didn't hear any engine spooling up. That witness talking about a "revving, starting noise" sounds to me like he was trying to describe the RAT noise, which we're all pretty familiar with now.


Engine Spool Down

When I did this for real in an actual plane (we had an uncontrollable engine, but also three good ones), stuck at about 30% maximum thrust, at 220 knots, it was an instantaneous spool-down \x96 really dramatic. The yaw came on so suddenly it felt like a heavy catering truck had slammed into us at speed.


Engines

They appear to get the plane to the correct speed and position on the runway as commanded, then at a time very close to rotate they stop providing thrust. The rest of the flight is consistent with gliding flight.


Rotate vs. Air/Ground Switching Vs Pilot action

(This is my take, it might seem counterintuitive, if you know better help) On a normal takeoff at rotation, liquids don't slide backward any more than they do during the takeoff roll itself. They slide back during the takeoff roll, and at rotation, there's actually a slight reduction in those backward forces. The main force is still pushing them back, but because the wings are now generating lift, there's more drag than when the plane was just rolling on its wheels. So, if liquids have pooled at the back of something at rotation, during and just after that maneuver, they'll actually ease forward a bit. The main force is still pushing them back, but it's less so. My take is if something sudden happens around rotation, I think it's probably more connected to something like the air/ground sensing or pilot action, but it is still possible that pooled liquids sloshing forward a little could also cause it.
Pilots have to do a few things at rotate time, pull back in the controls, not the thrust levers in error and then move the landing gear lever. Over the years there's been a few action slips, so unintended control movements.

Pooled water around the moisture barrier is just looking for a suitable access point to drain into. The 3 events I am aware of in the B744 were all during manoeuvring, 2 at rotate and one during a descending turn.


That is one conclusion (which I now suggest is unlikely), because you are assuming:

1. The hydraulic failure happened exactly when the truck had tilted forward but the split-second before the gear doors could open. That exact timing seems too coincidental.
2. The crew selected Gear Up. We have no proof of this. I speculate the crew never got as far as "Positive Rate...Gear Up" because they were already engrossed in flying the aircraft and processing their thrust problem. If an electrical problem had developed (as evidenced by the RAT deployment) the flight instrumentation would have been flickering and a flurry of silent master caution alerts would be very distracting.

I suggest it's more likely that the truck remained in a forward tilt from the takeoff run because the hydraulic failure happened prior to rotation, therefore keeping it in this unusual position. This answer does not rely on the gear lever position either. It also insinuates that their hydraulic problems occurred probably between V1 and VR. See my earlier post .

Well, in the context of the systems we're talking about here, why would it? The requirement is to "know" the actual air/ground state of the aircraft. The position of the gear lever doesn't help with that and might, if part of the voting, contribute to misidentification of that state.

A maintenance engineer looked into the gear tilt issue. The 787 has no hydraulic sequencing valves like traditional Boeings, and the bogie tilt command is simply generated by gear lever movement. So, I suppose the doors dropping before or after the gear tilting may simply be who gets there first.

That is not to say loss of hydraulics also causes "toes down" because of bogie imbalance or aerodynamics (as previously mentioned).

The landing gear lever is forward and up on the centre instrument panel, adjacent to the PFD. The two fuel control switches are aft and low, on the thrust pedestal. There's no reasonable way to confuse one for the other in terms of position, hand movement or 'muscle memory'.

I\x92m not saying this applies to this situation but it has been discussed extensively previously that despite their different positions and tactile features flaps have been raised when gear up has been commanded and vice versa

No there is not. Further investigation will likely see if the locking detents were in a decent state or not. TBQH, such a switch should be properly guarded. Like a Embraer is, like other types that one sees with switches one has to lift a guard to operate and is locked on with the guard in position. Boeing designers found out again in not making processes fool proof?

Understood - Absolutely no way of 'confusing' the two very different items in very different places. I'm suggesting more of a 'why did I just put my car keys in the fridge? issue.

Seconds count: That was with 10 seconds delay vs. 13 seconds for engine 2.

Time was spent with the verbal exchange, and then perhaps each pilot expected the other to put the switch back?

Anyway, the preliminary report also establishes that the aircraft had only 3-4 seconds of powered flight. (Would the gear lever be operated that early?) Everyone who saw that from the CCTV video, pat yourselves on the back.

Mayday call, dual engine failure, RAT deployment all confirmed.
TCMA was a red herring, the aircraft was firmly in air mode as the accident unfolded, and the thrust levers were at takeoff thrust the whole time.

For those sky gods who confidently state they would reset the cutoff switches immediately I would say that 10 seconds is not a particularly unusual time for startle effect to impair cognition, especially for something as monumental and unexpected as a dual engine failure at rotation. One reference amongst many: https://www.icao.int/Meetings/LOCI/P...Strategies.pdf

And for those who scoff at the possibility of the PM inadvertently operating the cutoff switches (which is done as frequently as operating the gear lever), I\x92d remind you that more than one Airbus has landed with its parking brake on after the PM inadvertently set it rather than arming the spoilers.

Even more serious incidents have occurred, such as the Luxair\x92s accidental retraction of the landing gear during takeoff rotation, leading to a failed liftoff:
https://avherald.com/h?article=48d1e3ae&opt=0