Posts about: "Flaps vs Gear" [Posts: 61 Pages: 4]

The assumption that engines were producing thrust because noise was heard isn't warranted.

Studies show that for aircraft landing with engines at landing thrust, 30 - 50% of the noise generated is from the landing gear and flaps down, so if the aircraft here had engines at low thrust setting, as appears to be the case, then the sound heard approaching could have been in large part due to the landing gear and flaps, which were down.

Ahh, thanks! I agree 99%. But if what you say is correct, then isn't this a design flaw? I also don't understand why you'd do Gear Up and Flaps Down at the same time, if the flight was otherwise proceeding normally? But if you're being hypothetical, sure, the pilot might actually be able to induce an electrical failure. I can't comment.

Anyway, let's say we know what's supposed to happen when an engine-driven generator (or its GCS) quits. (Which incident do you refer to?) That's what all the redundancy is designed to address. And maybe that's exactly what did happen - a generator / GCS failed at high load in a high ambient temperature. But possibly the failure then highlighted a pre-existing but undetected fault in the switching system itself. With the generator working normally for (months?), everything seemed fine. Sadly, there are always possibilities that the designers don't consider, or are too hard (too expensive, etc) to address.

Gear and flaps are both hydraulic, and the hydraulic pumps typically act as effective fault-containment - a hydraulic failure or excess load doesn't result in excess demand on the electric side; the pump just starts to run out of output flow/pressure.

In addition, the 787 has four main generators and I believe the switching is segregated into at least two controllers, on top of the four separate generator control units.

And again, electrical failure should not cause engine failure - consider QF32 where the wiring to the engine was mostly severed and they had to drown it with a fire truck.

It's not. Boost pumps should be more-or-less unnecessary at sea level.

I believe the valves are almost all bi-stable power-open power-close. When not powered, they remain in the last commanded position.

The valves are located in the spar (hence being called 'spar valves'. The fuel tank is immediately above the engine so it is a very short pipe for suction feeding. Tail mount engines are potentially a different story...

A Prelimnary Report must be prepared within 30 days, but does not need to be public. May or may not have CVR/FDR data.

Ok, thanks for clarifying. Of course, an overload will simply cause the hydraulic pressure relief valves to activate. There will be a moderate increase in motor current when bypassing, but the electrical side should be fully able to cope with that. Should be! I'm suggesting here that there was a fault somewhere in the electrical supplies that effectively derated some part of it, and that maybe the GearUp load was too much for it on this occasion.

Thanks for confirming the 4 gens. So there's probably quite a bit of switching required. Not sure how that's done, but I guess robust contactors are required. And even these can fail. Systems usually cannot tell that a contactor has failed on the open side until it's switched. So, a switchover may have been done, but a failed contact meant the backup generator wasn't connected. Who knows, so many possibilities.

Sure, I agree, absolutely shouldn't. Yeah, the A380... Possibly (I suggest likely), the A380 uses different logic from the B787. In the Airbus case, maybe they prioritised keeping the fuel on over shutting it off in emergency. So, severing the Airbus Cutoff signal leaves the fuel on. Boeing may use the opposite priority, that Emergency Shutdown takes precedence over Engine Running, so cutting the signal turns the engine off. I don't know, but don't think the Airbus incident necessarily applies here.

I don't think either of us was debating that. I accept it as a fact.

Okay! Many thanks for that! Of course, it very much complicates the picture, and I'm very puzzled as to how the Fuel Cutoff Switches and Valves operate. Apparently, the TCAM system shuts off an errant engine on the ground at least, but my concern is not with the software but the hardware. It obviously has an Output going into the Fuel Shutoff system. If the TCAM unit loses power, can that output cause the Cutoff process (powered by the engine-dedicated generator) to be activated? I guess that's the $64 billion question, but if MCAS is any example, then: Probably!

My first post here...I feel I need to, due to some posts I have read. As a 787 pilot who has flown Embraer, Airbus, 767 and the 787-8/-9, I am saddened by many of the posts on this thread.

Some of you should be ashamed.

Blaming the pilots before anyone has any idea what transpired.Short takeoff, improper flap/no flap setting, retracting the flaps instead of the gear, shutting down the wrong engine. In ANY other situation these actions would be laughable, and an insult to proffessional pilots the world over. Some commenting about the flaps even after pictures have shown that the flaps are extended. Also numerous people posting regarding shutting the wrong engine being shut down without any evidence to back this up. Videos clearly showing that the RAT was extended indicates that something very serious/catastrophic happened prior to this hull loss. People...this is the Proffessional Pilot's Rumour Network...Not the National Enquirer!!! I would urge everyone to WAIT for the report. Unbelievable.

Experienced 777 driver. Have tried to solve the puzzle. Looked carefully at the video in this article many times - see below and use full screen.

I might see a small puff of smoke and a smoke-ring just before they pass the shed. Indications of en enginefailure. I also see the wings tilt briefly - a few degrees - towards left. Correct procedure after enginefailure is to tilt the wings about 3 degrees toward the engine that is still running. I also see them climb at a - it seems - too high angle for the actual conditions if engine has failed. That will kill the nescessary engineoutspeed in a few seconds and be hard to recover from. If - and I say if - they in this stressed situation managed to shot down the wrong engine following the engineout procedures the RAT would come out. That would probably preoccupy them so much they forget everything about gear and flaps.. It is a situation I believe most experienced 777 / 787 pilots would recognise as a possibility and would explain everything. But this is pure speculation. Lets wait and see what the investigation teams find out...

https://www.aerotime.aero/articles/a...w-so-far-crash

Every airline training course I have had stressed never touching a critical item below 400 feet. That was later changed to 1000 feet at my airline. . I can\x92t conceive of the crew shutting a engine down in the first 8 seconds of flight.

@T28, sorry, I wasn't questioning the "experience" of Seven-Five, I was questioning his comment about doing (and messing up) the engine failure drills with the jet barely of the ground, as if it was SOP for him or his operation. That's crazy. As for an experienced airline referring to bank angle as "tilt", I'll say no more!

Increasingly, the posts in this thread are becoming more ridiculous as time goes on. The hampsterwheel bearings will soon explode. IMO it should be locked.

"I might see a small puff of smoke and a smoke-ring just before they pass the shed."

I originally wondered about that ... until an old colleague sent me this short clip of a triple kicking up dust rotating in the same location

For your consideration: (20 second clip)

Speaking as a B787 Captain..... There is so much rubbish and stupid suggestion being written here.

This aircraft was airborne for a grand total of 22 seconds, half of which was climbing to no more than 150' aal.

- No Flaps? Due to the setup of the ECL it is physically impossible to go down the runway without some sort of take-off flap set. The T/o config warning would have been singing it's head off. Despite assertions to the contrary I have seen no video clear enough to detect a lack of flaps.

- RAT out? Almost impossible, I have seen no quality footage that definitively witnesses the RAT being out. Those who think they car hear a RAT type noise might be listening to a motorcycle passing or similar. It takes a triple hydraulic failure or a double engine failure to trigger RAT deploment. They happily went through V1 without a hint of rejected take off so as they rotated the aircraft was serviceable. These are big engines, they take a long time to wind down when you shut them down. I have never tried it however engine failure detection takes 30s or for the aircraft to react and they were not even airborne that long.
- Flaps up instead of gear? The B787 flaps are slow both in and out. Given that the 'Positive rate' call is not made the second the wheels leave the ground, a mis-selection of flaps up would not cause any loss of lift for at least 20 seconds, by which time they had already crashed. I believe the gear remained down not because of mis-selection but because of a major distraction on rotate.

Discounting the impossible, two hypotheses remain:

1. Invalid derate set through incorrect cross-checking. Trundling down the runway takes very little power to reach Vr. It is only when you rotate that you create more drag and discover that you do not have sufficient thrust vs. drag to sustain a climb. Or....
2. Put 200' as the altitude target in the FCU. Immediate ALT capture and all the power comes off. PF is still hand flying trying to increase pitch but is already way behind the aircraft.

It could be after this that Boeing are forced to review the B787 practice of exploring the very edges of the performance envelope.

I have to agree with everything here except your assertion about engine shutdown.
Even though these are big engines with plenty of inertia, when you select engine shut off they spool down very quickly if on load. IE, The generators, two per engine and hydraulic pumps, etc, being driven by the (relatively) small mass of the N2 rotor will drag the speed down very quickly, the gennies will trip offine in seconds, the pumps will quickly reduce flow and pressure.
As for what went wrong.
If the engines have stopped working there has to be a common failure mode, fuel is one but as has been said, no other aircraft has had a problem, as far as we know. FOD? It would have to be something major to shut down two GeNX engines and there would be debris all over the runway, we would know by now.
I have no idea if the RAT has deployed, I can't see it in the video and the noise could be something else.
We shall see.
There is compelling evidence that flaps are set correctly and not retracted inadvertently.
I await further evidence.
Edit to add. LAE 40 years, type rated on 737 to 787 with lots of others in between.

I’m not a 787 driver so for fear of looking dumb in front of those that are this still confuses me. Even IF they’ve mis-selected the flap setting (I still don’t think it’s been cemented on here that there is in fact a FMS/flap setting disagreement warning but i believe there is), had the wrong de-rated take off settings, selected flaps instead of gear up the 787 with massive high bypass engines, FBW and full envelope protections surely cannot let itself be put in such a low energy/high alpha regime as we saw in the videos IF it has both fans functioning normally, surely?

the pilots may have messed up royally and numerous times so those holes lined up but the plane is the final block in the chain and a 21st century all digital entirely clean sheet design was sold as being immune to such catastrophic outcomes from a few minor (consequential yes) and fairly common errors- aren’t all the protections and our procedures designed after decades of mistakes?

im having a hard time squaring how a fully functioning modern bird like this could allow for this outcome and almost whatever the pilots did outside of unbelievable inputs and the pilots are are a bit of a red herring IMO

also to add, if it turns out that this was triggered by some procedural slips from the crew, if I was an airline I\x92d seriously consider my fleet choices going forward. I\x92ve never been on the anti-Boeing bandwagon, that has been the refuge of many ignorant people over the years, but I struggle to believe an Airbus would\x92ve got itself into that situation and we know for a fact they with their protections (narrow bodies mostly) have saved multiple crews (and their pax) in recent memory. The most modern Boeing around was meant to be as safe as possible and redundant

Every airline training course I have had stressed never touching a critical item below 400 feet. That was later changed to 1000 feet at my airline. . I can\x92t conceive of the crew shutting a engine down in the first 8 seconds of flight.

"I might see a small puff of smoke and a smoke-ring just before they pass the shed."

I originally wondered about that ... until an old colleague sent me this short clip of a triple kicking up dust rotating in the same location

For your consideration: (20 second clip)

Thanks as always TDR for your excellent professional input. It is therefore so much more perplexing that even you cant logic our way out of this impasse. That is, the assumption that the aircraft experienced a double engine failure (supported by a reasonably convincing argument that the RAT deployed), and yet no plausible reason (that we can see) for such an event. So some then collectively slip into the tired and lazy theories of intentional or unintentional crew actions that 1. beggar belief (intentional), 2. defy physics (flaps instead of gear despite clear evidence to the contrary) and call into question the professionalism of a very experienced Captain and crew as well as the aircraft manufacturer (because...well its Boeing so it must be software ).

Yet, the answer must be simpler and staring us in the face since logic and experience (everything you have offered TDR), tell us that modern airliner engines generally do not just suddenly quit flying at the same time. In this regard we can recall several instances of double engine failure associated with bird strikes generally involving large birds or large flocks or both. But it seems we have discounted this theory very early in discussion. Why? Because we cant see any birds, or flocks of birds or engine flames/surges or puffs of smokes from the engines which would support this. Really?

I have read all the 100's of posts (sadly) and while some very early posters tried to analyze the imagery, I suspect the very poor quality eventually discouraged most from seeing anything of interest. However, smattered throughout this discussion from the beginning to the end there have about four posts that describe seeing something where others have not. At least two of these were related to possible smoke but which were probably just the dust blown outwards by the wingtip vortices. Two others however have mentioned possible flames and puffs of smoke.

The video of course is very poor. There should be a special place in hell for people who subject us to looking at a video with continuous zooming in and out, inability to retain focus on the subject (it was just a CCTV monitor, not the actual aircraft they had to focus on) and constant camera shake. A video of a video, and then the resolution probably reduced for social media upload. This all results in a very unwatchable record of the aircrafts departure. The only immediate information gleaned seems to be some idea of how far down the runway the aircraft was at takeoff and the parabolic curve as it very clearly described the aircrafts flight path.




Air India Flight 171 on departure
But take a look at this frame. The right engine shows an artifact (pixelation if you like) that might represent a surge flame. I can almost see a puff of smoke just inboard of the aileron that may be associated with that too.

Am I just seeing distortion? Am I just seeing some smoke because that's where I would expect to see it?
We are all very used to seeing everything in 4K today but back in the day when everything was low res we used to join the dots. If pixels existed then something was there. If they didn't, it wasn't.
So if it's just pixels caused by distortion then they have coincidentally appeared in the tailpipe of an aircraft that crashed shortly after takeoff with a presumed double engine failure.

But surely we would see the birds? Well, not in this video. You cant even see the registration number on the side of the aircraft and that is much bigger than a bird. Haze, distortion, focus and low res, and each individual bird wouldn't even make up a pixel.

So make of this what you will, but this problem may have started on the ground. Birds strikes are very common according to Some AI pilots who interviewed for this following article but I have no idea of the authenticity of this report:

https://www.rediff.com/news/report/a...h/20250613.htm "The Air India pilots also added that Ahmedabad airport has long been known for bird activity near the runway, which could have contributed to the incident.

"This issue (of the excessive presence of birds) has been flagged multiple times," a third Air India pilot said, asking not to be named."
Of course, a single engine failure would not have brought this aircraft down, nor would it have deployed the RAT, but we can't see what happened on the left engine when the aircraft slipped behind the radio antenna building.

While these high bypass engines are designed and certified to keep running after experiencing certain types of bird strike, the effect on two engines concerns have been voiced about the contribution of certification to the mitigation of the risk hazardous bird strike in the two engine case.

This from Sky Library:
https://skybrary.aero/articles/aircr...nue%20to%20fly .

" A number of concerns have been quite widely voiced about the contribution of certification to the mitigation of the risk of hazardous bird strikes:

• The case of bird ingestion into more than one engine at the same time is not addressed directly and it is clearly extremely difficult to meaningfully estimate the probability of such an occurrence. However, it has been observed that, since some of the current standards only require that a damaged engine can be safely shut down, this circumstance should be more fully considered when determining the acceptable outcome of ingestion into single engines, especially for the twin engine case.
• It has been noted that the potential effects of bird strikes on modern electronic flight control systems and flight deck instrument displays have not yet been fully assessed.

Maybe someone can do some video enhancing of this image as others have done with the audio enhancement to give strong probability of RAT deployment.

If my suggestion can be corroborated at all, then the question of what happened next becomes somewhat easier to answer. Perhaps neither engine stopped running but they did so with limited thrust? If anything from the pilots mayday call can believed, it wasn't engines shut down..it was no thrust. So why did the RAT deploy? Cant answer that. And, I cant imagine it would be manually deployed if both engines were still running.
However, TDR did say.

"On the 767 and 747-400, when you shutdown an engine and the IDG goes offline, there is a momentary 'glitch' in the electrical power system as it reconfigures for the available power source - this is why you see the flight deck displays flicker and return, and the cabin lights momentarily flicker."

Startle factor that electrically systems were about to fail? Manually deploy RAT?

Edit: I might add, they would have found remains on the runway if this did indeed happen. But we have heard anything from anybody?

Capn Bloggs We shall see!

A mate tried gear/flap scenario in the sim earlier. Selecting flaps up (all the way) instead of the gear did not predjudice the flight path at all. They selected flaps up at normal gear retraction height and punched the AP in. The Slats remained out until 225kts (as per my post about 50 pages ago) and the aircraft climbed happily away clearing all obstacle by a good margin.

Was that using the same aircraft weight, same flaps, same ambient temperature and with the same de-rate(s) as the accident flight? Presumably he had inside information to find the appropriate numbers?

can you ask him by any chance what the outcome would be with f15 or 20 speeds, but in a F5 config and a rotation at VrF15 ?
and retract the flaps to 1 instead of gear ?
sorry I don\x92t know if that has been tested already.

A low level ALT Capture with autopilot ON would have made the aircraft pitch down quite hard. The same if flown manually and FDs followed (like Emirates). This aircraft did not pitch down.
If flown manually and pitch kept normal, the speed would initially drop, then increase as the speed dropped under the \xabcapture\xbb speed.
This aircraft was not flown pitch down into the ground.
Flaps instead of gear has been tested to be possible to fly out of.

Two engines stopped. At the same or nearly the same time.

The possible billion dollar question is why?