Posts about: "Relight" [Posts: 106 Pages: 6]

In my opinion ( and we all know the cliche about opinions ), there are only two plausible explanations.
1. Dual engine failure/damage due to multiple bird strikes somewhere immediately after V2 and liftoff.
Given the suddenness of the situation the gear could well have been overlooked by the PM who would be checking out the engine parameters only at this point in time. Flaps were in 5 position. No doubt about that.
Take off thrust used was for Optimum thrust
( meaning minimum thrust for take off given runway and environmental conditions ). That accounts for the full runway length being used. This is policy. That means minimum thrust used for take off to meet 2nd segment climb gradient at almost MTOW.
Loss of total thrust, RAT may or may not have deployed. At 650, AMSL no chance of any relight or turn back. Rest is history.
This also corresponds to the thud heard by the survivor about 30 seconds after takeoff.

2. Loss of thrust in only one engine and degraded performance in the other. Again, due to bird strike. Thereby not allowing even level flight.
Gear staying down could have been overlooked by mistake OR left down intentionally forseeing an impending ground contact by PIC and trying to minimize damage to his airplane.
Eitherways it added to additional drag and if anything, only accelerated the process of ground contact.
Given the above conditions safe flight would have been close to impossible. If not completely impossible. He neither had the airspeed not the altitude to make a 180 or even look for a safer place to put her down.
Refer the last Concorde flight/crash.

A very very sad day for aviation indeed \x85 🙏

At this stage, at least two scenarios seem highly plausible:

1. Technical issue

Airliners rely on air/ground logic , which is fundamental to how systems operate.

There have been numerous crashes and serious incidents linked to this logic functioning incorrectly.

Some engineering tests require the air/ground switch to be set in a particular mode. If it's inadvertently left in engineering mode—or if the system misinterprets the mode—this can cause significant problems.

• On the ground , if the aircraft is incorrectly in air mode , some systems may be unavailable—such as wheel brakes, reverse thrust, or ground spoilers.
  
• In the air , if the aircraft is mistakenly in ground mode , flaps might auto-retract, and various layers of system protection may be disabled.
  

In the case of the ANA 787, it appears the engine shutdown occurred during the landing roll, possibly when the TCMA system activated.

2. Pilot misselection of fuel control switches to cutoff

This is still a very real possibility. If it occurred, the pilot responsible may not have done it consciously—his mindset could have been in a different mode.

There’s precedent: an A320 pilot once inadvertently shut down both engines over Paris. Fortunately, the crew managed to restart them. Afterward, the pilot reportedly couldn’t explain his actions.

If something similar happened here, then when the pilots realized the engines had stopped producing thrust, pushing the levers forward would have had no effect. It’s easy to overlook that the fuel switches are in the wrong position—they're far from the normal scan pattern. And with the ground rushing up, the view outside would’ve been far more commanding.

Speaking personally, when I shut down engines at the end of a flight, I consciously force myself to operate each fuel switch independently and with full attention. I avoid building muscle memory that might lead to switching off both engines in a fast, well-practiced habit.

If this is a technical issue, I assume we’ll know soon enough.

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.

Combining all the bits and pieces of info from this thread so far, IMO we can theoretically sequence it thus using the video from the left:

00:18 Rotation. Normal takeoff config.
00:24 Gear up starts. per Raffael with FF.
......... FR24 ADSB last transmission (71ft, 172kt) just before runway threshold. Matches with video aircraft altitude at 1/2 wingspan.
......... ? Full power flameout leaves N2 ~ 60%; Airspeed < 200k so N2 will decay to 15% in 8-10s?
......... ? Takeoff EGT of 900C needs 25-35s to fall below 250C ?
00:27 Gear up stops. per Raffael with FF. Bogies tilted.
......... ? APU starts. 20-55s to 95%N?
......... Per 787 dual-engine fail/stall memory items, PM initiates Fuel Cutoff and Run.
00:28 Visible loss of thrust. Alt ~ 200ft using aircraft wingspan as measure.
......... Matches with eyewitness "within 5-10s ... it was stuck in the air".
......... Per 787 dual-engine fail/stall memory items, PM initiates RAT Switch for 1s. Whether auto or manual, the RAT initiates.
......... RAT "bang" heard by survivor
......... RAT coming online accounts for eyewitness "lights started flickering green and white".
......... Per 787 QRH below 1000ft, PF makes no change to Main Landing Gear and flaps, aircraft pointed straight for best glide.
00:31 Descending visibly, somewhere beyond the runway threshold. Alt ~ 200ft using aircraft wingspan as measure.
......... ? Because EGT > 250C FADEC blocks fuel (T-HOT hot restart inhibit?) so no relight though N2 > 15% ?
......... 787 glide ratio between 16:1 to 25:1 with MLG down, Flaps 5. About 15-20s and 3-5000ft of glide from 200ft?
......... Some flap accounts for the ground pictures.
00:34 ? N2 has presumably decayed to 15%, FADEC flips to X-START: airspeed outside envelope? No hope of relight now.
......... PM/PF transmits Mayday?
......... Video showing RAT deployed.
00:46 APU reaches some fraction of 95%N (APU sound accounting for survivor's perception of thrust?).
00:48 Impact. 4200ft from descent start, 3990ft from airport boundary road. 17s from visible descent start.

if this is a valid sequence, the only remaining question is why the dual-engine failure at ~200ft agl?

with condolences to the families and people affected.

This crash reminds me of the crash of a 747 Military Transport plane at an airbase in Afghanistan.

Shortly after TO, the cargo shifted, the plane became very tail heavy and stalled a few hundred feet in the air. It was the weirdest sight. For what seems a few seconds, the plane just seemed to hang there, presumably on engine thrust.

In this crash, the problem also seems to occur soon after rotation, as if something inside moved in response to its change in attitude. Maybe a loose connection on a main bus cable that moved... Maybe only a millimetre. Or a tool left inside an electrical cabinet slid somewhere it shouldn't. The possibilities are numerous, and without a lot more information, there's no way to know what caused this. I suspect a major electrical fault, probably intermittent.

How long would it take to restart those engines after a Fuel Cutoff flame out? Is that what happened, just before impact?

There should not be a max pre-start EGT limit in-flight - that should only occur on the ground for a pilot-initiated Autostart where the starting EGT redlines are lower than for in-flight.

In-flight, the Autorelight function should attempt to restart the engine as soon as a flameout is detected, and for an engine flaming out at high power it might catch it before it even goes sub-idle. Generally, Autorelight will continue attempting until some cutoff N2 at which time it will stop attempting, or if the pilot move the fuel switch to Cutoff. And while the EEC is still powered (via its own PMA) down to roughly 10% N2, the ignition exciters required for Autorelight do get their power from the airplane.

Thank you for the correction.

Could this mean that because there doesn't seem to have been any recovery once descent started, there was no fuel flow to support autorelight? Or that there was fuel flow and autorelight may have succeeded but there wasn't enough thrust generated before impact? From the video total descent time was only 17-20s. I guess what I'm asking is what would be the total cycle time if the first autorelight succeeded: flameout -> autorelight -> useful thrust? And if the PM executed dual-engine fail memory item fuel cutoff to run, how would that change the sequence?

Almost all catastrophic accidents that are not deliberately initiated require multiple causes. It’s extremely unlikely that both engine condition switches or fire switches were accidentaly actuated during a routine rotation and initial climb. However it’s stil possible that the crew did actuate those switches (intentionally or unintentionally) in response to some anomaly experienced at that time. Thus it’s not impossible that electrical system malfunction was the first link in a sequence that led to removing the fuel supply to both engines. The most obvious one is that crew thought that they had dual engine failure due to lost of main electrical power and initiated a double engine restart bycling the engine condition levers.

The purpose of this post is not to promote the above as a possible cause of the accident, but to remaind people that a (proven) mechanical fault does not rule out pilot error and vice versa.

I keep reading this theory and I'm baffled. You think the PF is going to attempt a dual engine shutoff and relight during the initial climb based on a hunch that the engines have quit, all without even a sideways glance to see what N1 is or a short word with the PM?

I don't want to believe it either. It defies belief but given certain confirmation bias (sim), panic and inexperience by the FO, it's not beyond the realms of possibility. It explains both the RAT and loss of lift. The alternative right now is a catastrophic electrical failure that wiped out the engines or engine control leading to loss of thrust, or a dual engine failure due to birds, fuel contamination or FOD. They are also valid, though IMO less likely.

You clearly had no prior training and instructing experience in Bharat🥴

To simplify the chicken/egg:

Tdracer earlier confirmed that an airplane electrical power loss would allow engines to keep running , because 1) engines are fully-capable of suction feed operation in takeoff envelope (if boost pumps lost), and 2) the EECs are powered by their own PMAs when running and to substantially below idle (I recall roughly 10% N2). Airplane powers the EEC for ground starts, prior to PMA coming online, and as backup to the PMA after that.

Related:

Engine igniters are powered by the aircraft. So theoretical full loss of aircraft power would disable Autorelight upon a flameout. Ignitors typically don't make the cut for most-essential battery-only loads because it would also take an engine flameout, and the airplane past V1 in ground roll can fly fine on one engine that can achieve takeoff thrust.

Autorelight is relevant - if there was a single-engine failure post V1, autorelight will attempt to relight the engine, so there is no need for a pilot to try to cycle the fuel switch to reset the EEC (potentially grabbing the wrong one), or to otherwise intervene. In such a circumstance, they need to trust their training. I've heard accounts that the most likely pilot instinct in such a situation would be to push the throttle(s) forward.

Finally - there was talk earlier about accidentally cutting the fuel switches - and it was duly noted that they have to be pulled out over the detent, so very unlikely. The same cutoff effect could be achieved with the engine fire handle(s), right behind the fuel switches on the pedestal - though they are an upward pull, so also not subject to inadvertent or accidental engagement.

I told you this re translation 3 days ago but the post was deleted then again 2 days ago see post 993.
Notwithstanding the possibility that recollection of the traumatised survivor may be unreliable it seems clear that he thought the engines were spooling up before impact. I think he deserves the benefit of the doubt that he might be right.

Possible auto relight but too late?

There was a comment very early in the thread (couldn't locate just now so assume hoovered up by the hard-working Mods) where someone postulated that the late "flare" we see in the video was possibly a pitch-up moment as the engines relit and the pilots went from a glide to a climb posture.

I don't want to review the video again -- personally, I suspect the "revving" the survivor heard was the sound of the RAT spooling up, and that the pilots were flaring as the ground approached in the vain hope of setting her down gently. Just sharing the OPs suggestion as it relates to your comment

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.

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.

Here are a few thoughts as to why an apparent dual engine failures could have occurred. Although the left and right engines are largely independent from each other they would respond to the same external input events. Am ignoring birds trikes or flight crew mishandling in this scenario. The question is what independent external events could result in both engines winding down during a critical portion of the flight in response to identical inputs.

There is one potential scenario I can envisage, but for now let's work backwards. If the EEC detects a condition that requires an auto relight / restart condition thr logic falls into two conditions.

Firstly is the engine in the in-flight restart envelope? At take off condition the answer would be no. Nowhere near. Therefore it would fall back to re-engaging the start motor. However this can only be done when the HP spool is at very low sub-idle condition. Therefore the EEC would command both the fuel and ignites to turn off until starter motor engagement conditions are met. That would take a very long time.

So what could cause the EEC to consider it is in restart/relight condition?
Normally it would require a flame out condition, detecting reduced pressures and/or slowing spool rpm's. For both engines to detect these conditions at the same time seems highly implausible though. Alternatively we need to consider a single input into both engines. One potential area for this to occur would be an abnormal aircraft power supply issue. An overcurrent or potential frequency change that may affect the engine power supply modules that fail in such a manner that they physically fail resulting in the EEC inability to change and utilise alternative aircraft or engine power supply in a clean transfer, or a software misinterpretation of what has happened; if for example the EEC's were momentarily depowered.
Of course the design is supposed to be tolerant of such events but when dealing with power/signal interruptions the software tries to be tolerant to an extent before doing anything and not all failure modes are as clearly defined as a spec sheet would suggest. Whilst aircraft power supplies (or an aircraft supplied signal) are not always wholly independent a particular type of failure could have been received by both engines and therefore both engines rolled back toward sub-idle.

The simplest answer: Lo Lvl Alt Cap; Thrust to Idle; Startle Factor; Inappropriate Memory Items : ( RAT deployed; insufficient time for Eng relight.

Non-aviation engineer here: I have a question about the low level altitude capture theory that I've been a bit hesitant to ask, since no-one else seemed to be bringing it up.

My understanding of altitude capture is that the autopilot will automatically adjust both thrust and pitch to intercept the requested altitude. However to my eyes there is very little pitch adjustment in the CCTV video of the plane taken from behind, until the very end of the video when it pitches up somewhat (obscured by buildings, more visible in the smartphone video). Please correct me if I'm wrong but I'd have thought that if the autopilot was trying to capture a very low altitude it would start pitching down (quite noticeably!) to do so, not remain at what looks like 10+ degrees nose-up. I honestly struggle to reconcile what I'm looking at in the video with an attempt to level off at 0ft, 200ft, or any of the other mentioned low-level altitudes.

Also maybe I'm missing something 787-specific but generally doesn't the autopilot have to be activated for the aircraft to automatically attempt to capture the pre-selected altitude? That was the case in this incident involving a Dash 8 and a target altitude of 0 feet that I am reading about ( https://www.gov.uk/aaib-reports/aaib...-dash-8-g-ecoe ). I'd have thought the PF would still be hand-flying the departure at the point that things went wrong, considering that the gear hadn't even been retracted yet...

Engines generally deliver hydraulics while running down, as they operate down to a much lower speed than the generators do. Useful flight control power might be available from windmilling alone (hence why the 747 didn't have a RAT until the -8). That's subject to similar speed issues to the RAT but the engines have much more inertia. The Virgin Atlantic 024 report (A340 partial-gear-up landing at Heathrow) notes an expected 25-30 seconds of useful hydraulics after engine shutdown.

This doesn't apply if the pumps are depressurised by a fire handle, or to allow easier engine relight.