Baltic CS-300 uncommanded dual engine shutdown

[andrasz]

"A safety feature unknown to the pilots and operator stopped both engines immediately after landing on the runway"

There is quite a discussion going on at AVH, surprised it made no ripples here. Anybody in a position to shed more light ... ?
http://avherald.com/h?article=4ea5172d&opt=0

[Anti Skid On]

That would have made a go-around "interesting".

I know little about the type or its systems; could this be electircal, thinking if there is a switch on the main gear for spoiler deoplyment and it somehow sent a signal to the FMC/AT

[andrasz]

From what I gather, based on the AVH reporting it was clearly not a bug but a feature. There was some logic in place that commanded the shutdown of both engines after WoW due to perceived or real throttle failure, probably to avoid a possible S7 / Gol scenario. The key issue is that the existence of this "feature" was unknown to the pilots and operator. Does this sound familiar from somewhere... ?

[Fursty Ferret]

TCMA, innit? Having said that no one on the 787 knew about it until it surprised a crew in Japan with a dual-engine shutdown on the landing roll and we got an airworthiness bulletin.

I've just searched the FCOM and there's very little about TCMA in there - you have to go to the unapproved and uncontrolled Trent 1000 i̶d̶i̶o̶t̶s̶ pilot's guide directly from Rolls Royce if you want more than one line of text and a bullet point.

[DaveReidUK]

WoW appears to be a necessary condition for this bug/feature mode. It clearly isn't (on its own) a sufficient one.

[golfyankeesierra]

So they not only stole the B787 nose, the B777 tail and the A330 wing(-lets) designs, they also stole that weird TCMA software!? Serves them well!

[tdracer]

Does sound rather like a TCMA (Thrust Control Malfunction Accommodation) activation. For those who may not know, TCMA is intended to shutdown an engine that remains at high power uncommanded, with the throttle at or near idle. It was the result of a regulatory mandate that deemed single failure caused Uncontrolled High Thrust (UHT) on the ground to be catastrophic (and hence not certifiable). Since all turbine engine fuel controls have a single failure that can result in UHT (e.g. the fuel metering valve goes hard over), Boeing developed TCMA. TCMA is only active on the ground (and at least on Boeing installations has very robust air/ground logic). The TCMA logic is resident in the FADEC software.
My understanding of the 787 Trent event was that the pilots did some very strange movement of the thrust levers while exiting reverse thrust that confused the TCMA logic and caused the dual shutdown - presumably that logic has been updated.

With regard to this event, I'd be more interested in why they apparently got dual engine thrust lever position fault...

[TheEdge]

....with the autopilot and the autothrottle engaged, the flight crew retarded the thrust levers to the idle position resulting in a disengagement of the autothrottle.

That's not how you normally disengage A/THR in an Airbus, i dont know about the 220 btw.

[Rug]

Which Airbus are you basing your statement on? The ones I know, it's exactly how you disengage the A/THR - usually on landing but also if you wish to use manual thrust and the engines are already at idle.

[Roj approved]

That is one way of Disconnecting the A/THR in the situations you described, another is to set the required thrust, or match the lever position to the current thrust setting and then press one of the "Instinctive Disconnect Buttons" located on the Thrust levers.

On the B787, and I believe other Boeings, you have the ability to retard the Thrust Levers during any phase of flight, the Thrust mode goes to HOLD, and the thrust delivered will be matched to the lever position, then you reset the levers to the commanded thrust, and the A/T takes over again. It is common practice to have to do this on descent as the aircraft will struggle with the VNAV Path as it sets a higher thrust than it needs for the descent.

Coming from the Airbus it was a bit weird, but you get used to it and can be useful in certain situations.

[Rug]

Indeed, Roj. I was referring only to the point that retarding the levers to idle was not a "normal" way to disengage the A/THR - could have been a little clearer that it's only one particular way of going about it normally on the Airbus types I'm familiar with.

I also have no idea how the A300 goes about things which is why I was curious and thought there may be something new to learn.

[Roj approved]

No worries Rug, we are all here to learn, and like you I am curious about this incident, it’d get your attention for sure.

[Timmy Tomkins]

And if performance required reverse thrust on landing?

[DaveReidUK]

Rug

I'm guessing you don't really mean A300.

[FlightDetent]

As correctly stated in the thread title, it is an Airbus-in-law afterall.

Dual TL resolver fault should not really be happening on this new generation.