June 19, 2025, 18:55:00 GMT
permalink Post: 11906268
One thing that just came to my mind: We are scratching our heads why that happened after the type is in service for almost 15 years with millions of flight hours and surely hundred thousands of T/Os and landings.
What if it takes something to be worn/used after many years to get that kind of failure? The AI 787 was 11 years old. We have been discussing the fuel switches, but there are thousands of other parts that might contribute to such a failure in connection with some other problem.
What if it takes something to be worn/used after many years to get that kind of failure? The AI 787 was 11 years old. We have been discussing the fuel switches, but there are thousands of other parts that might contribute to such a failure in connection with some other problem.
Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Fuel (All) Fuel Cutoff Switches
June 19, 2025, 22:17:00 GMT
permalink Post: 11906440
You may be surprised to learn that aircraft sometimes need full thrust on the ground.
TCMA requires that the pilot pulls the thrust levers back to idle, and that the engine fails to spool down to idle as commanded. Only then will it shut off the engine (on the ground).
Pilots try to avoid pulling the thrust levers back to idle when they're taking off.
For that reason, TCMA has never triggered during take-off before.
TCMA requires that the pilot pulls the thrust levers back to idle, and that the engine fails to spool down to idle as commanded. Only then will it shut off the engine (on the ground).
Pilots try to avoid pulling the thrust levers back to idle when they're taking off.
For that reason, TCMA has never triggered during take-off before.
Subjects: None
June 19, 2025, 22:23:00 GMT
permalink Post: 11906444
ONCE AGAIN: I don't think that is what happened - it's just an example of a chain of events triggered by worn out and/or older equipment. Both failures would never happen on a new aircraft.
Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Fuel (All)
June 19, 2025, 22:31:00 GMT
permalink Post: 11906447
Subjects (links are to this post in the relevant subject page so that this post can be seen in context): EICAS FADEC Generators/Alternators
June 19, 2025, 22:39:00 GMT
permalink Post: 11906453
Even if it's possible - there is not enough time to do so in this phase of the flight. Doing a full restart of one engine will take 1-2min. That means it will need a couple thousand feet.
Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Relight
June 20, 2025, 12:25:00 GMT
permalink Post: 11906921
Looking at water in the fuel tank: It's hard to believe that there was enough much water in the center fuel tank to stop both engines. On the day of the crash VT-ANB only flew DEL-AMD, a 1h flight that did not use the center fuel tank. However, the day before the plane came in from CDG with 9h of flight time. That flight would surely have used the center fuel tank. That means a large amount of water would have accumulated in the center fuel tank during just one day and two sectors.
Subjects: None
June 20, 2025, 17:18:00 GMT
permalink Post: 11907146
tdracer posted - "
Commanded engine cutoff - the aisle stand fuel switch sends electrical signals to the spar valve and the "High Pressure Shutoff Valve" (HPSOV) in the Fuel Metering Unit, commanding them to open/close using aircraft power. The HPSOV is solenoid controlled, and near instantaneous. The solenoid is of a 'locking' type that needs to be powered both ways (for obvious reasons, you wouldn't want a loss of electrical power to shut down the engine). The fire handle does the same thing, via different electrical paths (i.e. separate wiring)."
Search this thread for "HPSOV" if you need confirmation of the quote.
Note there are two shut off fuel valves per engine - the HPSOV and the Spar valve. Both stay where they are if power is lost.
Search this thread for "HPSOV" if you need confirmation of the quote.
Note there are two shut off fuel valves per engine - the HPSOV and the Spar valve. Both stay where they are if power is lost.
Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Fuel (All) Fuel Cutoff Switches High Pressure Shutoff Valve Spar Valves
June 20, 2025, 23:08:00 GMT
permalink Post: 11907388
Hello, this is my first post on pprune; as a 787 pilot I\x92m also puzzled by this accident. All seem to agree that for some reason there was a complete electrical failure and RAT deployment. With a complete electrical failure all six main fuel pumps fail. Each engine also has two mechanically driven fuel pumps. On takeoff, if there is fuel in the center tank, it will be used first, pumped by the two center tank pumps.
My airline\x92s manuals don\x92t go into much detail, but I read on another site that if both the center tank pumps fail, the engine driven pumps aren\x92t able to suction feed well enough from the center tanks to sustain engine operation. If there was fuel in the center tanks, a complete electrical failure would soon lead to center tank fuel pumps failure (all fuel pumps failure as stated previously) and fuel starvation of both engines. A rescue from this situation would be an immediate selection of both center tank fuel pumps OFF (not if my airline\x92s non-normal checklists) and waiting for successful suction feed from the L and R main tanks to occur, this would take a number of seconds.
My airline\x92s manuals don\x92t go into much detail, but I read on another site that if both the center tank pumps fail, the engine driven pumps aren\x92t able to suction feed well enough from the center tanks to sustain engine operation. If there was fuel in the center tanks, a complete electrical failure would soon lead to center tank fuel pumps failure (all fuel pumps failure as stated previously) and fuel starvation of both engines. A rescue from this situation would be an immediate selection of both center tank fuel pumps OFF (not if my airline\x92s non-normal checklists) and waiting for successful suction feed from the L and R main tanks to occur, this would take a number of seconds.
Furthermore the preference of the center tank while it's filled is just by the higher fuel pressure those center pumps deliver. There is no valve that controls that, which might be triggered by switching off pumps.
Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Centre Tank Electrical Failure Fuel (All) Fuel Cutoff RAT (All) RAT (Deployment)
June 21, 2025, 00:24:00 GMT
permalink Post: 11907404
It's not possible to shut them down without power - they are already shut down by the power loss. That was exactly my point.
Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Electrical Failure
June 21, 2025, 11:52:00 GMT
permalink Post: 11907686
It is a battery, not a supercapacitor. Most commonly nickel-cadmium, because that chemistry has been used in aircraft for decades. They're safe and readily accepted by regulators. Li-ion can be used, but a "special condition" from the regulators is needed, plus the weight savings would be negligible.
The 10-minute limit has nothing to do with the battery capacity. It's to prevent the recorder from continuing to operate after an accident and thus overwriting the audio of interest. There's a timer in the RIPS module. It will stop providing power after exactly 10 minutes, regardless of state of charge.
The 10-minute limit has nothing to do with the battery capacity. It's to prevent the recorder from continuing to operate after an accident and thus overwriting the audio of interest. There's a timer in the RIPS module. It will stop providing power after exactly 10 minutes, regardless of state of charge.
https://www.geaerospace.com/sites/de...rder-3254F.pdf
Subjects (links are to this post in the relevant subject page so that this post can be seen in context): CVR EAFR RIPS
June 21, 2025, 12:30:00 GMT
permalink Post: 11907705
Without going round the hamsterwheel again does anyone have an actual reference for this? Because I've gone back through each of tdracer's very informative posts about this
see here
and there is a discrepancy in the two points he makes below in adjacent posts. Is tdracer talking about the same HPSOV valves? Can anyone confirm that with both AC power loss and and a temporary DC power loss there are no critical engine related shutoff valves that will fail safe (unpowered) in a closed position?
However, it could easily have different modes of operation (closed, electrically actuated), activated (electrically actuated), open (transition from activated + fuel pressure > 300psi).
Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Fuel (All) High Pressure Shutoff Valve
June 21, 2025, 14:17:00 GMT
permalink Post: 11907789
A full fuel load of 100t would have brought them by far over the MTOM as there is only around 8t of load left with full fuel of 100t. My guess with 242 POB and some baggage would be at least around 24t of load. Furthermore the fuel burn for tankering almost 50t for 9h would be enormous.
EDIT: Sailvi767 was quicker…
Subjects: None
June 21, 2025, 15:10:00 GMT
permalink Post: 11907830
Subjects: None
June 21, 2025, 19:07:00 GMT
permalink Post: 11907992
I have developed embedded systems for more than 20 years - most in real time applications. I wouldn’t expect FPGAs in such systems. As mentioned before modern microcontrollers can easily handle loads like that in a real time environment with guaranteed response times.
Subjects: None
June 21, 2025, 21:37:00 GMT
permalink Post: 11908084
Why should it? It\x92s part of the FADEC as are the TLA sensors.
Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Electrical Failure FADEC TLA (Thrust Lever Angle)
June 21, 2025, 23:26:00 GMT
permalink Post: 11908148
The Centre Wing Tank is as it says the centre of the wing. The top and bottom skins continue the aerofoil section through the fuselage, with the front and rear spars' webs forming the fore and aft ends. The inner surfaces of the top and bottom skins have spanwise 'stringers' (well that's what we called them at Airbus), which are 'I' sections attached to the inside to provide stiffness to the skins. The inner faces of the centre wing tank are the tank. There is no separate fuel bag.
The tank is unpressurised. It is vents to atmosphere throughout the flight. There is a fuel tank inerting system which feeds nitrogen-enriched air into the ullage (air space above the fuel). On the 787 it does this on all tanks. Other airliners only do it on the centre wing tank (and any other fuselage tanks if fitted).
Entry to the tanks once they have had fuel in, generally needs breathing apparatus once it has been in service.
Pictures of the inside of a completed 787 Centre Wing Tank aren't easy to find. This shows either the upper or lower skin with its stringers.
The tank is unpressurised. It is vents to atmosphere throughout the flight. There is a fuel tank inerting system which feeds nitrogen-enriched air into the ullage (air space above the fuel). On the 787 it does this on all tanks. Other airliners only do it on the centre wing tank (and any other fuselage tanks if fitted).
Entry to the tanks once they have had fuel in, generally needs breathing apparatus once it has been in service.
Pictures of the inside of a completed 787 Centre Wing Tank aren't easy to find. This shows either the upper or lower skin with its stringers.
Subjects: None
June 22, 2025, 12:15:00 GMT
permalink Post: 11908493
With 'intact' being the crucial part of these recent posts. It is my understanding that a suitably equipped LAME can simply download the FDR data from an installed EAFR (CVR requires dismounting). So downloading as such, isn't the issue.
However more importantly, as implied by another poster 'patience' is of the essence in this thread ...
However more importantly, as implied by another poster 'patience' is of the essence in this thread ...
Subjects (links are to this post in the relevant subject page so that this post can be seen in context): CVR EAFR FDR
July 01, 2025, 11:38:00 GMT
permalink Post: 11914210
This is my latest attempt to square the circle using all the data points and minimal assumptions. The main shortcoming of the analysis is not knowing the maximum L/D and the speed for maximum LD with the gear down, flaps 5, and the RAT extended. However, if I use a reasonable number in my opinion for the L/D in that configuration and assume that the airplane is being flown at the speed for it, it will not get to the crash site. The distance from the runway of the crash site is from a previous graphic (1.55 km); the rotation point from fdr, permalink 314; 200 feet max height above the runway being generally accepted; crash site 50 feet below the runway elevation cited previously. An average speed of 180 knots is consistent with the dimensions given and 30 seconds flight time. A flare at 50 feet will briefly increase the L/D to 20, maybe even 30 (500 feet more than shown) but still not enough to make up the shortfall, In fact, with a head wind the L/D will be lower than assumed as well as if the speed being flown is higher or lower than required for maximum L/D in that configuration. In other words, there must have been some thrust available.
Subjects (links are to this post in the relevant subject page so that this post can be seen in context): RAT (All) RAT (Deployment)
July 13, 2025, 22:34:00 GMT
permalink Post: 11921745
Two notes regarding the switches:
I pulled the Honeywell data sheet. It contains dozens of different versions of the same switch. There are locking / non locking / momentary press / 2 or 3 position versions all in the same data sheet.
Furthermore they are waterproof:
They are protected from hose-directed water. They could easily withstand a cup of coffee or even a whole bottle of water.
Here is the data sheet: https://www.mouser.de/datasheet/2/18..._1-1735572.pdf
I pulled the Honeywell data sheet. It contains dozens of different versions of the same switch. There are locking / non locking / momentary press / 2 or 3 position versions all in the same data sheet.
Furthermore they are waterproof:
The robust design of the TL Series toggle is well-suited for many military, aerospace and other demanding applications where reliability is essential. These applications include environments where the panels are subjected to mechanical shock, vibration, and temperature extremes as well as environments with dust, splashing or hose-directed water.
Here is the data sheet: https://www.mouser.de/datasheet/2/18..._1-1735572.pdf
Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Honeywell
July 14, 2025, 12:17:00 GMT
permalink Post: 11922151
Even if the engine would have accelerated to TOGA - no way to fly you out of that situation being near stall speed far below Vmca, with no altitude to trade for speed on one engine.
Subjects (links are to this post in the relevant subject page so that this post can be seen in context): Fuel (All) Fuel Cutoff Switches TOGA