IIRC, the TCMA is fitted to ALL 787s regardless of fitted power plant. A similar system, TCMP, may be found on (some) 777s.

Hope the descriptions below help.

TCMA (B787)Thrust Control Malfunction Accommodation

Thrust Control Malfunction Accommodation is an EEC function that provides protection against idle thrust asymmetry conditions while on the ground.

The EEC commands shutdown of the affected engine when the:

• airplane is on the ground, and
• thrust lever is at idle, and
• engine is above idle speed and not decelerating normally

The EICAS caution message ENG FAIL (L or R) is displayed with an aural beeper once the engine falls below idle speed.

TCMP (B777)
Thrust Control Malfunction Protection

The EEC provides protection against an uncontrolled high thrust malfunction during ground operation. The EEC shuts down the affected engine whe

• airplane is on ground,
• thrust lever is at idle, and
• engine is above idle speed and not decelerating normally.

The EICAS caution message ENG FAIL (L or R) is displayed when the engine falls below idle speed.
—

It's in that draft FCOM without a caveat to engine manufacturer.

Perhaps it's MELable on the RR but not GE?

Perhaps. Just seems odd to me. Thanks for the tip on the FCOM. I wordsearched "TCMA" in the FCOM earlier, but the acronym isn't used. Had to use different searchwords.

Thanks.

Thx for spotting my typo on FL, now corrected! This was posted on the closed thread 2, PM’d you the permalink.
regards

Yes, thanks, that helps.

Airborne use of reverse
 

2 Quotes:

I recall reading somewhere that one of the early jets (DC8?) could reverse two engines for descent control. (Herod)

The Trident could use reverse thrust for emergency descent, 10,000 ft/min, and before touchdown. The C17 can use reverse thrust on all engines for tactical descents at 15,000 ft/min. (Topgas)

On the DC8 it was permitted to use reverse in the air to increase RoD during a descent. This caused great discomfort due to vibration and was not encouraged. In the '70s, It also tempted an upgrading Captain on the DC-9, who had been a First Officer on the DC-8 to attempt airborne reverse thrust when on an overly steep approach to Malaga, although this was not certified on the -9. The result was loss of parts on one reverser, an emergency landing in MLG with unscheduled night stop - and failure of the upgrading.

Correct. Though I have no time flying the plane, I have dozens of hours in the DC-8-63 full sim of the airline I worked for at the time (Worldways Canada). I did many approaches in the center two engines in reverse. As there was no "back" [of the plane] I have no idea what it would have been like back there, but in left seat, it was no problem. I'm not aware that our pilots every did it in flight. I do know that a pilot once tried to back off the gate with reverse when there was no towbar available for pushback. One engine's buckets stuck in reverse and that was that for that flight. There was word that this was operationally very discouraged after that!

On the GEnx, the entire TCMA function is resident to the FADEC. It's possible to MEL dispatch with one FADEC channel inop - which effectively means only one channel of TCMA would be available. No need to have a separate MEL item.
I don't know enough about the Trent architecture to know why it needs a separate MEL item for one channel of TCMA failed.

Pardon my perhaps ignorant post, but based on what is known, as I read it....
TCMA CONSTANTLY monitors WoW and the thrust
At a possible RTO, with gear still on runway, the thrust would be closed?
Brakes on, a change of solution? Gotta avoid the overrun ?
Brakes off levers slammed full open ....
Does TCMA act too quickly.?






?
Quite

1) If the crew rejects the takeoff, and pulls the thrust lever to idle,
and then IF one of the engines does not spool down (fast enough),
TCMA will shut it off,
because an engine that's thrusting will not help with stopping,
and it might blow the aircraft sideways off the runway as the aircraft slows and rudder authority is lost.
So that is good!

2) But that did not happen, and the crew now wants to take off anyway (why....?).
PF pushes TO/GA or slams the throttle.
Now the engine is accelerating as commanded.
TCMA does not care about acceleration.

And should you be asking that in this thread? The incident here is a landing, not a take-off.
What may have happened here was
1) engines idle on glide,
2) touchdown, PF starts reversing
3) engines run up, PF undoes reverser and moves throttle to idle
4) maybe, maybe TCMA expects engine to decelerate faster from that than it does

So it's the exact opposite of a RTO, and because the throttle ends up on idle, TCMA can trigger. But on the RRTO, it ends up at full thrust, where TCMA won't trigger.

Thanks for responding.

Didn't mean to identify the other thread. Did I?

Because TCMA Constantly monitors thrust (N1), levers, and WOW, lag times become critical, yes? How long does TCMA wait, armed with instantaneous sensor input, to shut down engines ....?

It may seem that there are some questions ?? Timing is everything... Isn't an RTO at some point an emergency landing? Then if abandoned, a TO? Maybe put thrust reverse in there....?
,
Admittedly far fetched, ..... Impossible?

If there is any new information on the ANA event, discussion about that event here is appropriate. If that event has been thoroughly covered, let's let the general topic of 787 engine shutdowns pause for a little while... It is certain that a future topic will return discussion on this theme - patience......

Pilot DAR
One of the moderating team.

So, a fellow I don't know, infers from word on the street is that something is implicated, but can't quote directly, 'cause it's not verifiable!?!

I think a mod will delete that.... oh yeah...

Come on... We're professional aviation people! If we read that as a log entry, would we fly that plane?

There was something else in the deleted post's incorporated-by-reference blog post which seemed quite imprecise as well as suspect due to the nature of the omission. Although mentioning the NTSB's participation in the investigation, entirely missing from the blog post was any reference to the FAA - and the context was airworthiness of the type. Unless Annex 13 in effect rewrites the certification process (and I admit, not currently being posted to Montreal, maybe something changed but I missed it - kidding) the FAA, not the NTSB, handles major problems with airworthiness certifications.

Correct. The NTSB might tell the FAA that they have a concern, and perhaps make a recommendation, but it is the FAA (or equivalent national authority) who issues certification and handles airworthiness problems. I chose to not read the referenced blog post.

For those who do not know Dvid Learmount, ex pilot, long standing journalist with Flight Global, etc, see: https://www.airsafetymatters.co.uk/p...avid-learmount

The blog re Air India does refer to FADEC issues in an embedded link and the item on DGAC checks; but he does not pursue this aspect beyond -
There is a lot of credible information gathering that backs this up, but since its precise source is not certain, I will not run it here.
Meanwhile, be patient. This kind of accident is incredibly rare these days, and finding the truth behind it could not be more important.
https://davidlearmount.com

So, a couple of things: The PPRuNe rules (2&4) ask not to link to other aviation websites, just as a polite reminder to all. And, Remember, earlier up the threads we discussed not presenting information which really does not add anything of consequence to the discussion... We agree that posts which essentially say "listen to me, cause I have something to say", and there is not really a something there... are not desirable, 'just spins the hamsterwheel...

I read:

That's a hamsterwheel statement. Of course there's a lot of credible information... someone is reading flight data recorders! Its precise source is going to tell us when they're ready, 'cause they are not going to provide it faster because we're eager to hear. So it really doesn't add anything of value to state that you're not going to run it - 'cause yeah... there's nothing credible to run!

Kudos to one of our members, who is known to provide expert answers to the media on aviation events, who, for this event told the media that he would not offer an opinion yet . As was said, there are no points for being first here.

And, finally.... which thread is this one? Remember that this is not the thread for discussing the Air India accident...?

We mods really appreciate thought going into posts, which could be: "I got nothing to post, so I'll wait.".

Thanks, a member of your moderating team...

Hello everybody,
after reading the whole thread I wonder why it was impossible to start the engines again?! Even with the help from outside (technicians) it was not possible. Does the TCMA has this feature, not allowing to re-start the engines once activated?
Best regards

My first jet transport was the venerable B727. We went to work and MONITORED stuff. If an exceedance occurred or was likely, our monitoring led to actions to minimise damage. We also navigated from one aid to the next, and rarely got seriously lost. The ‘children of the magenta line’ also rarely get lost, but don’t necessarily monitor so much,and are not necessarily so flexible when, for instance, track shortening happens.

Sadly, the basics of the profession are being eroded to the point that we may be in danger of losing professional status. Don’t get me wrong, I loved some of the developments that gave us VNAV approaches and the like when prior it was a VOR or even NDB with dive and drive finales. That was/is a major improvement in safety terms. But, it comes with a cost.

That cost is complacency, and complacency kills.

With the introduction of auto induced shutdowns on start when exceedances are likely, and well documented and easily understood in the aircraft manuals we are quietly led to EXPECT that the aircraft will save itself. A quick reading of this thread indicates to me that there are still things that are either buried, or missing from the docs that we use to guide our daily work. I cannot for the life of me work out why an engine will EVER shutdown itself, except perhaps on start when the implications are ‘who cares’, because we are not even moving.

We all know that things break, failures occur. Why, for goodness sake, are we prepared to accept technical answers to problems that can be ameliorated by the unfashionable concept of active monitoring, and in doing so accept uncommanded (by flight crew) actions that impact on the operation during critical phase. I despair of what is happening to the profession and have no regrets that retirement called before all was lost. I feel that I am a dinosaur, however, some things were better in the not so distant past.

1) Because some failures happen too fast for crew to react; rotor burst due to engine overspeed being the classic example. And if you tell the crew that they must react and shut engines down in <2 seconds if they notice an anomaly, you'll have a huge number of false engine shutdowns, plus crews shutting down the wrong engine and... crashing.

2) Because a crew didn't shut down an engine that was stuck at maximum thrust, overran the runway, and wrote off the aircraft.

3) Because fuel, cost, performance, and weight savings can be achieved by running parts closer to limits, or making equipment faster-reacting (lighter) in such a way that the situation can change too fast for humans to monitor.

The inverse can be argued: if the automation can do the job equally or more reliably, why not automate it and let the crew focus on things that are more deserving of their attention?