Posts by user "BugBear" [Posts: 21 Total up-votes: 5 Pages: 2]

Originally Posted by A320 Glider

Can I just clarify: the 787 has FBW and certain flight envelope protections. If the pilots suffered a dual engine failure after takeoff, they would pull back to stretch the glide as the computers will not allow the aircraft to stall. This is effectively what Sully did when he kissed it into the Hudson like a pro.

In any other aircraft, if you lose thrust in all your engines, you would be pushing the nose down immediately!

Originally Posted by TURIN

Good spot, but it is possible the actuator that operates the door is damaged.
Unlikely, but possible.
This does add more credance to the complete power loss scenario.

Originally Posted by TURIN

Do you mean this one?

Boeing 787 Makes Emergency Landing

Originally Posted by dbenj

I agree. It is intriguing that we have none of the radio communication released. As a result, we do not have confirmation of what was actually said during the Mayday call, and no ability to deduce who was the PF and PM.

Originally Posted by SpaceQuality

Also a newcomer here, but an experienced private pilot, Software Engineer with a degree in Aerospace Computer Science and former Head of Quality for Satellites and Interplanetary Missions. We have already seen bad software solutions and the results thereof in the 737 MAX accidents, which makes me wonder, if the TCMA can reach a state, where unintended engine shutdown is possible.

There is one system implemented in the 787, that has the authority to shut down the engines, based on software subsystem decision. Interestingly - according to the description in the patent below - the same TCMA software package determines the shutdown decision, in both redundant subsystems.

Excerpt from the Patent:
"Malfunctions in aircraft power plant thrust control systems can result in uncontrollable high engine power levels that are potentially hazardous or catastrophic for aircraft operation. A particularly hazardous situation is when a thrust control system failure results in one of the aircraft's engines continuing to operate at a high power condition and not responding to a throttle command to reduce power during takeoff, approach or landing. Typically, when this failure mode occurs, the actual thrust either increases to a significantly higher than commanded thrust and/or remains at a high level when the thrust levers are set for low thrust....

In one preferred embodiment the present invention is directed to a system and method for detecting and correcting a thrust control malfunction in an aircraft engine. The system includes an electronic engine control (EEC) unit that includes a first processing subsystem and a second processing subsystem, and a thrust control malfunction accommodation (TCMA) circuit included in the first processing subsystem and the second processing subsystem. Additionally, the system includes a TCMA software package executed by the first processing subsystem and the second processing subsystem, thereby providing redundant execution of the TCMA software package.

The method of the present invention compares the engine's actual power level with a threshold contour defined by the TCMA software package. When the TCMA software package determines that a thrust control malfunction has occurred, based on the engine's power level exceeding the threshold contour, the engine is shut down by the TCMA circuit.
The present invention is still further directed to an electronic engine control (EEC) unit configured to detect and correct an aircraft engine thrust control malfunction using an active-active functionality. The EEC includes a first processing subsystem for unilaterally monitoring engine operation and shutting down the engine when a thrust control malfunction occurs, and a second processing subsystem for unilaterally monitoring engine operation and shutting down the engine when a thrust control malfunction occurs."

Just my 20 cents

Originally Posted by Mr Optimistic

From tdracer
However, TCMA is only active on the ground (unfamiliar with the 787/GEnx TCMA air/ground logic - on the 747-8 we used 5 sources of air/ground - three Radio Altimeters and two Weight on Wheels - at least one of each had to indicate ground to enable TCMA). TCMA will shutdown the engine via the N2 overspeed protection - nearly instantaneous. For this to be TCMA, it would require at least two major failures - improper air ground indication or logic, and improper TCMA activation logic (completely separate software paths in the FADEC). Like I said, very, very unlikely.

Originally Posted by Alty7x7

Philosophically, it is primarily pre-V1. It prevents uncommanded high thrust when you are trying to chop the thrust on a RTO. Overthrust can generally get you off the ground post V1, as can (stating the obvious on a pilot forum) a single-engine loss post V1. So OK to shut down post V1 if still on ground.

Originally Posted by scouse104

Could this potentially be tied to the 51 day reboot bug that was previously addressed? Specifically the part about \x93engine operating indications\x94

According to the directive itself, if the aircraft is powered on for more than 51 days this can lead to "display of misleading data" to the pilots, with that data including airspeed, attitude, altitude and engine operating indications.

Originally Posted by njc

OK, but even if we do assume that there was a major electrical fault which brought down the main supplies: multiple posts in this thread have already asserted that this would not cause the shutdown of the engines, and that even if the fuel pumps failed, suction would keep the engines running.

Originally Posted by FlightDetent

I am curious to learn what power source drives the high-pressure fuel pumps in the engine. If there is such a thing, I suppose there would.

Gearbox? This is at odds with a possible cascading electric failure that (might have) caused a loss of engine fuel feed.

To my understanding on my ancient plane and engine design, the HP pumps that feed the nozzles are driven mechanically, which enables gravity feeding among other scenarios, but also assures the fuel supply is independent of whatever happens upstream of the nacelle. Except for LP/fire shut-off cocks.

Originally Posted by benjyyy

There have been conflicting reports about the call to ATC. Original reports quoted the Captain saying "Mayday...no thrust, losing power, cannot lift". But I've seen reports today stating the call was simply "Mayday, Mayday" and then no further response.

Difficult to confirm so I wouldn't put too much weight behind it until something more official is released.

Originally Posted by Calldepartures

Not sure I would rely on the Times of India as a reliable source, but this is what they have reported...

Ahmedabad police confirmed the pilot's chilling distress call. It reached air traffic control (ATC) seconds before all communication ceased. Top officials said the jet had nearly exhausted the 3.5km runway at Sardar Vallabhbhai Patel International Airport - usually, 2.5 to 3km is needed for a wide-bodied jet.

"The longer runway roll hints at a possibility of the aircraft not having adequate thrust for take-off," said a source close to the investigation. "The facts can be ascertained only after the black box is decoded."