Air India 787 crashes on take off 2

[LittleInch]

A full 787-8 has crashed shortly after take off in ahmedabad.

Basically barely got off the ground then look like its trying to land in this video.

Air India flight to London Gatwick crashes in Ahmedabad with more than 240 people onboard – latest updates

Plane for flight AI171 was carrying 242 people including 169 Indians and 53 Britons, says Air India

www.theguardian.com

Specualtion that they pulled flaps up instead of gear up and basically didn't have enough lift so it looks like a gentle stall right into a built up area.

Looks to be flaps up, slats/ nose flaps down and gear down which is very odd.

 

[Alistair_Heaton]

I have never seen a perm mag generator for powering the fadec depicted in any aircraft electrical block diagrams.

 

[TugboatEng]

On our diesel engines our alternators (permanent magnet generators or whatever) were found to not be very reliable so many of our vessels run battery chargers off the AC electrical system. That was fine in the 1990's when the battery chargers were the mag-amp or transformer based chargers. However, the solid state chargers have become popular and they are not reliable. I say charger but these are really power supplies that use batteries as filters. In my fleet I replace failed solid state chargers in critical applications with mag amp units from a specific vendor.

Another question, is breaker trip sequencing a part of commercial aircraft certification? It's starting to show up in a narrow portion of marine side.

 

[Alistair_Heaton]

Yes but it's airframe certification, not engine.

This is the issue with the MAX they grandfathered it when it was none compliant. But the local Boeing certifiers put it through.

 

[LittleInch]

The other idea skulking around is some fault or override on the TCMA system designed to cut engine power when on the ground and engines at a different power level to where the throttle lever were.

Now it take a whole lot of holes to line up in the Swiss cheese, but as we've seen before, this is possible once in 15 years.

The shutdown being triggered somehow by Gear up is part of this hypothesis.

The silence from the investigation is unnerving.

 

[Alistair_Heaton]

That sounds like the issue for the shut down on landing of the a220 after pilot over riding the automatics and causing confusion.

It's maybe the reason why airbus opted for an in the gate and make it very special the pilots ever touch the power levers.

Airbus had issues at the beginning with the logic. There was some suspect reports on various events in hindsight to stop all fleets being grounded. They got away with it.

 

[LittleInch]

They appear to have been able to download the FDR and CVR from the crashed units in Delhi on Wed 25th June.

Hopefully they start giving some decent answers soon.

 

[Garbage1]

As the brain behind the engines, the FADEC monitors, protects and controls the aircraft propulsion system in real time. The FADEC 3 is on board many commercial aircraft such as the Airbus A318, A319, A320, A321 and A380, Boeing 737NG, 747-800, 767, 777 and 787 Dreamliner, as well as on military platforms such as the Airbus A400M.

"Modes" in FADEC reminds me of "Mission Profiles" in Phased-Array Radars. If you did not boot system in correct 'Mission Profile' the radar could not deal with incoming threat. Basically 'Mission Profile' means you need to know what threat you are trying to address, before you boot the radar, to launch the correct software. This sounds like FADEC modes, and if in incorrect mode or programmed-in incorrect information, then you end up with FADEC responding incorrectly in a very critical moment.

FADEC aka 'micro-manager'

FADEC 3 - 3rd generation Full Authority Digital Engine Control

The FADEC 3 engine control unit provides aircraft electronic engine protection and reduces the pilot's workload. It offers lower costs of ownership and facilitates maintenance management.

www.safran-group.com

 

[SnTMan]

"It was the FADEC".

That's not saying much of anything, you ask me

 

[MechinNC]

Just a basic question from a non-pilot, non-aero engr:

Say some computer decided to roll back power (and does this actually move the levers? I think it does..). Pilot notices levers pulling back and says heck no, I need power NOW. And shoves levers to max thrust.

Who is in control at that point? Will engines respond to the pilot input, or will they respond to what ever the software wants?

May be key here...

 

[Roga50]

Why is fuel cut so important that it needs to be the front and center most switch?

I'm not familiar with the 787, but with Airbus, those switches are used for the normal startup of the engines and also for the normal shutdown. Think of them as an "engine on-off switch." Internally, those switches send commands to the computer to perform a sequence of events, so it's not just a fuel cutoff. (on Airbus, there is also a mode knob between/below the switches which modifies their functionality related to engine starting).

 

[Garbage1]

Just a basic question from a non-pilot, non-aero engr:

Say some computer decided to roll back power (and does this actually move the levers? I think it does..). Pilot notices levers pulling back and says heck no, I need power NOW. And shoves levers to max thrust.

Who is in control at that point? Will engines respond to the pilot input, or will they respond to what ever the software wants?

May be key here...

I am non-pilot, non-aero engr, but from a system engineering perspective, all my reading says FADEC is in control and input from pilot on throttle is just a request by pilot, and FADEC will ignore input, if it does not agree. FADEC is not in control of BTB buss transfers in my reading, rather BCPU is in control of that function. If BCPU detected increased load on one engine VFSG, it would be in control of load transfers. It would appear BCPU had to be involved in electrical power loss to both engines and all 4 VSFGs, and if so, then it would seem that would force a rebooting of FADEC? Have no idea if FADEC moves throttle handle in over ride situation?

 

[Roga50]

Just a basic question from a non-pilot, non-aero engr:

Say some computer decided to roll back power (and does this actually move the levers? I think it does..). Pilot notices levers pulling back and says heck no, I need power NOW. And shoves levers to max thrust.

Who is in control at that point? Will engines respond to the pilot input, or will they respond to what ever the software wants?

May be key here...

On Airbus, the thrust levers do not move by order of the computer (not sure on 787 though). On the airbus, the thrust lever setting is more of a "thrust limit" most of the time, when AutoThrust is enabled. (but moving to the full throttle position, called TOGA, will force full throttle, overriding the autothrust computer decisions; autothrust remains "armed" in this position and will take back over once the throttles are moved back to the normal [climb detent] range). With autothrust, the computer can vary the thrust as needed but the levers do not move. There are indications on the screen in front of the pilot (upper left corner above the artificial horizon) that tells the pilot what the computer is doing with the thrust. The computer does have the ability to "lock" the thrust into full throttle (called TOGA LOCK) if certain conditions are exceeded--the pilot must temporarily disengage autothrust [controlled by a button on the throttles or a button on the autopilot panel] to reset that condition).

This video explains it pretty well for the A320:

 

[Garbage1]

From link below:

"Disadvantages of FADEC system
1. Full authority digital engine controls have no form of manual override available, placing full authority over the operating parameters of the engine in the hands of the computer.
2. If a total FADEC failure occurs, the engine fails. (both the channels fail)
3. Upon total FADEC failure, pilots have no manual controls for engine restart, throttle, or other functions.
4. Single point of failure risk can be mitigated with redundant FADECs (assuming that the failure is a random hardware failure and not the result of a design or manufacturing error, which may cause identical failures in all identical redundant components).
5. High system complexity compared to hydro mechanical, analogue or manual control systems.
6. High system development and validation effort due to the complexity.
7. Whereas in crisis (for example, imminent terrain contact), a non-Fadec engine can produce significantly more than its rated thrust, a FADEC engine will always operate within its limits."

Full Authority Digital Engine Control - FADEC

Full Authority Digital Engine Control - FADEC is concerned about some very sophisticated and precise combinations of various electronic devices together. FADEC is a computer system coupled with sensors and actuators which is completely capable of controlling the complete engine by itself.

www.aircraftnerds.com

 

[MechinNC]

I understand that a complete FADEC failure would take out the engine. That seems unlikely as there are two units per engine, and I think two channels per unit, with gen power dedicated to FADEC and associated engine controls from engine gearbox.

My question is mostly that if other software systems in the aircraft, or in FADEC itself, decide to do a roll-back of thrust, can the pilot over ride that with shoving the thrust levers forward?

Seems like the Airbus system allows for such.