Posts about: "Engine Failure (All)" [Posts: 410 Pages: 21]

An FCOM available in the net says that the FMC doesn\x92t accept Vr entry lower than Vr min or V1 min.

The "requirement" for TCMA was "specified" by the FAA. Manufacturers seeking certification of aeronautical products subject to the requirements then had no choice but to design and instal systems that met the FAA's certification requirements.

I'm pretty sure it's clear what "sources", other than TCMA systems if any, have "authority to issue an engine shutdown command", though it does depend on what you mean by "engine shutdown".

Lead Balloon:



“The "requirement" for TCMA was "specified" by the FAA. Manufacturers seeking certification of aeronautical products subject to the requirements then had no choice but to design and instal systems that met the FAA's certification requirements”.

I think that has already been established upthread.


“I'm pretty sure it's clear what "sources", other than TCMA systems if any, have "authority to issue an engine shutdown command", though it does depend on what you mean by "engine shutdown".”

I don’t think that is clear at all. The shutdown hypothesis, if true, both engines, makes it likely that they were commanded to do so. While the discussion has centered around the TCMA subsystem, if other subsystems have the ability to do that, they need to be defined and looked at as well.

There\x92s at least N2 overspeed protection that actually uses the same hardware as TCMA to stop the noise. There might exists crosstalk and inhibit for the N2 overspeed protection if the N2 overspeed protection has shut down the other engine. In fact it\x92s not confirmed that no such crosstalk exists in 787 TCMA system. It would complie with \x94no single fault should cause\x85\x94 certification requirements. Other than that I see no practical difference in the propability of TCMA and N2 overspeed protection to shut down both engine during take-off.

Think about this accident from 100,000 feet. In other words, DON\x92T think about the specific root cause. We have almost no factual information to ponder at the moment but we can still ask a larger question: How did an experienced crew in a modern aircraft find themselves in a situation from which there apparently was no escape? Given the redundancies, fault tolerances, crew training, and engineering and operational controls present in modern aviation, how could it be that they happily took off in an airplane and flew it into an unsurvivable event just moments later?

This isn\x92t the first one either. On February 9, 2024 a Challenger 600 manuevering to final at Naples FL, (APF) lost both engines simultaneously and crashed on a highway short of the runway. The NTSB final report isn\x92t out yet so we don\x92t know that cause either, but the situation was the same. SOMEhow, a highly experienced crew found themselves in a situation from which there was apparently no escape. Whatever the cause was, how did it go un-detected until it produced an accident? (It\x92s NTSB accident number ERA24FA110. You can find that thread on PPRUNE by searching on Challenger 600. The preliminary NTSB report contains interesting readouts from the FDR. Yes, they lost both fans simultaneously.) I\x92m not suggesting these two accidents have related causes, I\x92m only observing that both crews apparently had no way out.

I\x92m asking, \x93Whatever the flaw was that initiated these events, how did it remain un-known *until* it produced an accident?\x94 We test and re-test modern aircraft for every imaginable failure mode during the design, certification, and production process. We train and re-train techs, mechanics, flight crew, and everybody else that touches the airplane to be sure a high level of performance and safety is not compromised. Think bigger. Think about \x93the system\x94 as a whole. Apparently the system missed something. What are we not seeing?

My condolences to all who were lost. Please keep in mind that except by the grace of God it could have been any one of us on that terrible day.

NASA retired, licensed since 1971.

A better question would related to this accident would be have you ever shut down the wrong engine below 200 feet AGL in the sim. I strongly suspect the answer would be zero percent.

I still consider the forward truck tilt is a massive clue to a C system Hydraulic failure prior to wheels-up, which must have been caused by loss of electrics (since C is solely electrically powered), so I am still wondering if hydraulic failure happened before or after the loss of thrust.

While thinking about the consequences of a total hydraulics failure around time of rotation (caused by a suspected dual engine failure), here is a new observation. I searched the previous threads to see if anyone lese had noticed it.





In the rooftop video, as it's just approaching the treeline, there are spoiler deflections visible just behind the engines on each wing.

With a total hydraulics failure, the pilots control column using direct wiring, will only control this spoiler pair and the stabiliser. The RAT does not control this spoiler pair (hydraulically), only the most inboard spoilers pair. Its an interesting observation because it means this spoiler pair were being deflected electrically, either by the battery or RAT. But if the RAT provides emergency C hydraulic power why didn't the RAT powered spoilers deflect instead? Does this mean the RAT was unable to provide emergency hydraulic at such low airspeed?

I think this also re-affirms the critical loss of power (dual engine failure), and rules out many other theories. It tragically lost all power, both engines, all hydraulics and electrics (apart from battery and RAT).

I am wondering if anyone else has noticed other flight control deflections?

(Tried posting link to youtube but unhelpfully frames entire video)

Water was mentioned earlier in the previous iteration of this thread, as I recall by one of the most well respected contributors on the forum and an expert in flight testing and certification issues. There have been a couple of well known incidents of flight deck screens going blank due to all sorts of electrical problems caused by water ingress into the E&E bay, fortunately in daytime vmc and not on particularly electric jets, and both I believe at rotation. The one I recall had it’s L1 door left open during a black rainstorm in Hong Kong. It’s also been said that total electrical failure can’t result in in a double engine failure on the 787, but I wonder what multiple sequelae could result from such water contamination with an aeroplane that relies so much on electrical power and software? Another very remote probability but many accidents and incidents are. I don’t even know if there was any inclement weather before this flight, maybe someone could confirm?

Just looked…..none by the looks of things so skip that theory, apologies.

I didn't read that thread, but having flown the aircraft (challenger 600 type), I believe the consensus is that the Captain reaching underneath the thrust levers to actuate the flaps can (and has) resulted in the "triggers" on the back of the thrust levers being engaged- if this is done while the FO is bringing the thrust to idle, it can result in going below the idle stop to cutoff. In other words, the engines were inadvertently shut down.

But I agree that the complete, simultaneous loss of thrust on both engines has to be an astronomical probability, and the cause is going to be interesting to say the least.

I also agree that any one of us could be put in a horrible position within seconds that would be very hard to recover from- the older I get and the more hours I spend in the air, this starts to spend more time in one's consciousness, unfortunately.

BTW calling the crew " highly experienced" is a bit of a stretch IMO, the Captain certainly was, but 1100 hours isn't even enough for an ATP in most countries. For all we know it was not a factor, of course.

PS, what is an SLF??

I need to correct one of my previous posts, I was going down the path of a mismanaged engine failure after V1, however it's been demonstrated to me that this aircraft will fly away on one engine even with the gear down with better than minimum climb gradient requirement. Quite astonishing actually.
That just leaves deliberate act not necessarily intentional, fuel vapour lock and automatically commanded engine shutdown.
I hope the rat is found soon so we know for sure if both engines were in fact lost.

The 787-8 landing gear retraction is primarily hydraulic, using the center hydraulic system for the main operation. However, the alternate gear extension system utilizes a dedicated electric pump to pressurize fluid from the center hydraulic system for gear extension. Obviously due its size and weight and staged retraction, the effort required to raise and stow the gear greatly exceeds that required for extension.

The main gear retraction/extension is controlled by the center hydraulic system.

It is apparent that the hydraulics failed when the engines shut down after breaking the down-locks and leaving the Main Landing gear bogeys in the tilt position, ready for a next step internal stowage and door closure (that was now never to happen). It is therefore apparent that the dual engine failure and consequent automated RAT extension was precipitated by this gear selection or retraction cycle and thus likely to be either WoW micro-switch or 5G Radar altimeter-effect associated. Due to accumulator depletion, the electric pump load would have spiked to replenish it. This may have precipitated the dual engine shutdown due to an unfiltered electrical surge affecting the Ground/Air microswitches (or a local 5G transmission affecting the RADALT) and resetting the TCMA.

The RADALT? Another plausibility? Because of the furore over a spasticated frequency allocation by the US FCC, the US FAA had finally “bought in” and declared that individual nations and their airline operators were responsible for their own 5G frequency spectrum allocations and for taking essential steps to ensure mitigation of the interference effects upon aircraft automated landings and other critical systems caused by their own national approved 5G spectrum decisions. It was admittedly a situation calling for extensive modifications to (and shielding for) the three radar altimeters fitted for redundancy considerations to all modern airliners... for Category 3 ILS approach and landing in zero/zero visibility conditions. The RADALT also features in many air-ground sensing applications. (eg the 747-8).

This was an unusual FAA “passing of the buck” to manufacturers such as Honeywell etc. (to sort out with client operators). But then again, it was not the US FCC’s right to dictate the specific 5G frequencies internationally. These spectrum allocations now vary over the wide selection of 5G phones available (and also nationally). 5G Radar Altimeters constitute a part of the ground/Air sensing that changes the TCMA from ground mode (able to fuel-chop engines) to the air mode (inhibited from doing so)... Ground activation is acceptable ...where fuel chopping of uncommanded thrust can prevent runway sideways excursions or runway length overruns. The question now becomes: “Is it more (or less) safe having an automated fuel-chopping capability on BOTH your left and right, rather than leaving it to the pilot to react via his center console fuel cut-off switches... in the unlikely event of a runaway engine after landing (or during an abandoned take-off)?

5G Frequency Variations

The frequencies of 5G phones vary nationally based on the frequency bands allocated and used by different carriers in each country. In the United States, for example, carriers such as AT&T, Verizon, T-Mobile, and others use a combination of low-band, mid-band, and high-band 5G frequencies. Low-band 5G frequencies typically range from 600 MHz to 1 GHz, mid-band 5G frequencies range from 1.7 GHz to 2.5 GHz, and high-band 5G (mmWave) frequencies start at 24 GHz and go up to 40 GHz . These frequencies are allocated by regulatory bodies such as the Federal Communications Commission (FCC) and can vary between countries based on spectrum availability and regulatory decisions. In other countries, the specific frequency bands used for 5G may differ, leading to variations in the frequencies supported by 5G phones. Additionally, the deployment of 5G networks can also influence the frequencies used, with some countries focusing more on sub-6 GHz bands while others prioritize mmWave technology.

5G interference? It may be an avenue worth exploring?

I still think that the small black area is the back of the engines visible through the small gap of the extended flaps.

Furthermore: The small hydraulik pump of the RAT only powers some of the flight controls that are powered by the center hydraulic system. The ones powered by the engine driven pumps will not work once the engine(s) failed.

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.

Very subjective, and I agree it it could look like a slotted gap between the wing and flaps, except the shadow is confined to exactly where that spoiler pair is located. You don't see it where the rest of the flap is. It would be good to hear other opinions about what we are seeing here . Is it wing, flap, gap or spoilers?


I don't understand your point here. The RAT hydraulic powers very specific flight controls like the stab, rudder, outboard ailerons and one specific pair of spoilers - the inboard most spoilers. Have a look at this schematic (at 3:55) youtu.be/DFbOLNduutI?si=siPnQ9oHMbLgp64K&t=235 (not publishing link as it fills the frame). The spoiler pair I mentioned above (visible in the video) are only powered by L hydraulics and electrical. Assuming L hydraulics was lost by dual engine failure, then this spoiler pair can only have been electrically powered...hence the conclusion it's either powered electrically by the Battery or electrically powered by the RAT. That spoiler pair is not connected to the RAT hydraulics.

Does a Boeing 787 go from HOLD TO/GA to THR REF/VNAV SPD at 400' AGL/AAE, like older versions of the Boeing?

If so, what if the WoW stayed in ground mode, for whatever reason, how would that affect

1) Retraction of the landing gear (it didn't retract, as obvious in videos released)

2) The transition from HOLD to THR/REF at 400' (they reached just barely over 400' AGL before leveling, then descending)

I am also thinking that Air India would follow Boeing procedures in that the left seat pilot will move their right hand away from the thrust levers at V1, and thus, at 400', the thrust levers are not guarded or monitored?

Even if thrust levers were pushed forward, is there some kind of logic related to FMC and-or FADEC or other involved systems, which regardless of thrust lever position commands IDLE thrust to the engine?

Remember that Airbus accident where the aircraft thought it was landing, while the pilots wanted full thrust, and they crashed into a small forest because some kind of idle is all they were afforded by the system?

If the engines of this 787 thought it was in the rollout or final part of the flare, it might also command thrust levers to idle?

This does not explain the RAT, though, unless there is some weird combination of software working against each others logic.

Had the engines failed by some really random, odd reason, like birds, fuel contamination-vapor-starvation or such, wouldn't there be at least a slight bit of roll or yaw visible? Even with TAC or whatever they have on the 787, I would think even a 1 second difference in thrust reduction between the engines, a hint of yaw or roll should be visible ...

Thoughts, especially by someone who flies the 787?

Dunno, the discussion around the switch as a failure point looks spurious to me. With that used to support the idea that a possible engine shutdown was due to the master fuel valve closing.

I don\x92t really buy that, since we don\x92t know at this stage whether the engines did in fact fully shutdown, or were commanded to spool down to idle, or other lower thrust setting, both of which would produce the same result. Thoughts ?.

If we accept that the RAT was deployed, then my understanding is that this would only occur if both engines were fully shutdown, not just reduced thrust or idle.

I have read most of the thread (old and new). As a lawyer working in forensic investigations, I am constantly involved in problem-solving. My field of work also includes complex investigations related to insolvencies, which almost always require an analysis of the causes behind a specific, established outcome. In doing so, I naturally also have to deal with probabilities. However, it often turns out that the most likely or plausible explanation does not reflect what actually happened.

Many of the considerations I’ve read fail because the simultaneous failure of both engines is extremely unlikely, leading to a constant search for higher-order causes. It was suggested that an incorrect altitude setting led to an early thrust reduction. However, this would not explain the deployment of the RAT (Ram Air Turbine), especially since the thrust could have been readjusted. FADEC and TCAM are highly redundant systems, and TCAM failure is unlikely due to WOW (Weight on Wheels) logic, making a simultaneous engine failure after VR equally improbable.

With that said, and with regard to my question concerning the AD that relates to the fuel control switches (FCS), my thought—and it was nothing more than that—was that their activation becomes more probable if it can occur accidentally. That’s how I came across SAIB: NM-18-33.

Another user then brought up an iPhone. That notion would, of course, be dramatic—but how unlikely is it really that after approximately 10,000 actuations between December 2013 and June 2025, the two FCS no longer lock perfectly? Considering all of this, I find it quite conceivable that the A/T slightly reduced thrust in the first seconds after VR (e.g., if an incorrect target altitude had been entered) and that an object lying between the thrust levers and the FCS could have pushed the FCS into the “Off” position. Due to the buttons on top of the switches, which provide some resistance, it’s even possible that the object both pulled and pushed them.

But all of this is speculation. The investigation report will bring clarity.

Even if my theory is not confirmed, I still believe that the positioning and mechanism of the FCS are suboptimal. Switches of such critical importance should be better protected, and movements in the area in front of the switches (like reducing thrust) should not follow the same direction as shutting off the fuel supply. A different switching direction alone would provide more safety—especially considering that the FCS are protected laterally by metal plates.

I thought this was a very good point. There are some detailed posts discussing the TCMA patent including this post . Is it possible the TCMA software functioned exactly as specified, and the issue is input data into TCMA?

In a total electrical failure, when the system switches to emergency battery power, how are input variables like rad alt and wow switches processed? (these were inputs someone mentioned on the 747-8, have the TCMA inputs been identified yet?)

I speculate the gear truck forward tilt is a symptom of a C hydraulic failure caused by a total electrical failure around the time of VR. Once they got 10 deg nose up on the rotation, with a total electrical failure, could the FADEC receive erroneous rad alt or wow inputs, and how would TCMA handle these inputs in the transition from ground to air logic?

What is baffling is the simultaneous nature of the suspected dual engine shutdown. There is no obvious asymmetry, with the flight path or rudder movements. If the engine fuel control switches had been manually cut one at a time, there should have been some visible flightpath change or flight control response. Something happened to both engines at exactly the same time.