Autothrottle problem.

[Guest fullflapsplease]

Now I've combatted my earlier issue I'm now experiencing a different some what more worrying problem.I was crising across the pond at FL360 (my claculated optimum CRZ level) and whils hanging some washing up glanced across to the monitor to see that my speed had dropped into the 1st portion of the low speed buffet zone, the wins was at a constant and the speed continued to leak.The A/T made no attept to recover from the situation, it was almost like the A/T was non-existent.I had to fly with manual throttle control making small input changes to maintain the CRZ speed.Earlier in the day a frien of mine had reported a similar issue to me so I'm wondering if this is indeed a bug.I was in the PAX RR aircraft, if that makes a difference?Cheers.MarkPS: also, should the upper EICAS show CRZ in cruise or should it contine to display CLB? Mine is displaying CLB when cruising at the level inputted into the FMC.

[Guest 744nut]

Hi Mark,It happens to me often too. My workaround is: ALT hold, SPD and than VNAV. It helps if the the Left part of the FMA is empty which means that speed is not controlled by the AT. It takes the AC some time to react.hope this helpsTon

[Tabs 2,790]

Mark,Yes, the EICAS should show CRZ, not CLB. Sounds like you possibly had something messed up in the perf init section. Next time you see this happen, save the flight and email me the files...

[Guest fullflapsplease]

I'd be right in thinking this shouldn't be happening though?Is a fix being worked upon do we know, I'm sure it is ;)Mark.

[Guest fullflapsplease]

In the INIT page the CRZ level was set at FL360 I didn't go to 340 and then climb beyond that to a more optimum height.However if I had done that wouldn't the FMC just accept a new cruise altitude had been dialled in and change it automatically?Cheers again.Mark.Just thinking, if this A/T problem is going to constantly happen it could really impact on long haul jouney's people are doing for their VA's hours wise, as it's going to ruin flights, you only need to nip to the loo, make a sandwich and when you come back, bang you've stalled and plummeted to the ground???!!!

[Guest 744nut]

I guess you are right ;-)Ton

[Guest D17S]

This happens from time to time, but generally it has been at the FMC's "MAX" altitude. There's a very fine line between the FMC's MAX altitude and CRZ thrust's ability to maintain the FMC's calculated airspeed. At MAX altitude and CRZ thrust, even a feather dropping will cause the airplane to start a VERY gradual deceleration. It will slow into the stick shaker just about the time you are kickin' back for that after dinner cigar. This sounds just like what you are getting. You will notice that some of these

[Guest fullflapsplease]

Hi Sam and thanks for the reply.Right, as you can see in my attachment I was most definately at MAX ALT in fact I was OPT!!!But it has dawned on me that someting did happen, call it a flash back ;)I had to pause the flight to go and pick up my wife from work (was fling online for BAV and can't just leave the aircraft to is own devices, plus the BAV ACARS system would cancel the flight saying I'm inactive after a period of continued absence) When I got back I unpaused the flight and got a warning bell and an FMC message, the message read, FL240 MAX ALT or words to that effect.I cancelled the message as I'd never heard of it before and all seemed well however the upper EICAS had CLB on it and obviously the A/T had now failed to function.Is there a problem with pausing/unpausing the flight, didn't have this problem with just the PAX version, just since I applied the F?I was only flying to JFK from LHR GW was around 310,000 Kg's so FL360 as an optimum with moderate head winds seems around right for that weight?Any ideas welcome.Cheers.Mark.

[Guest 744nut]

"the message read, FL240 MAX ALT or words to that effect."I have it all the time after longer period of pausing the sim. Thrust mode in the FMA is out also regardsTon

[Guest Ray CYYZ]

Think I have seen what you are talking about after a pause ... I get a quick FL123 MAX ALT that appears then goes away as the bird recovers from the pause.Seems like some calculation is crunching the numbers quicker then the data is restored, but it goes away within a few seconds and has the proper FL MAX within the FMCRay

[Guest fullflapsplease]

Yeah, problem is, this aint sorting my flight out and is causing me major hours loss.Was kinda hoping the management would have helped to sort this out?Mark.

[Guest D17S]

If the left FMA stays blank, the AT is disengaged. You gotta get it back. Try swapping your pitch mode to "ALT" (hold) by pressing the MCP Alt hold button, then pressing the MCP 'SPD' button. Generally that will get the AT back on line. Now press the MCP Vnav button and you'll be back in Vnav with the appropriate thrust mode engaged. But check for a larger issue. Next time, pull up the FMC

[Guest fullflapsplease]

I did try pressing these buttons to no effect.In fact the speed hold button wouldn't even engage itself.This is clearly a bug as others are having the same problems too.My picture shows the VNAV FMC state AFTER the pause and as you can see I am not doing anything wrong by that.Would like a comment from the devs on this, they must be aware that an issue exists that requires resloving, after all, it aint jusy lil' ol' me ;)Thanks.Mark.

[Guest 744nut]

Sometimes switching from ECON to LRC mode works alsoTon

[Guest fullflapsplease]

But surely we shouldn't be having to do this?Mark.