Engine Problem - Aborted TO

[craig_read 43]

Hi,Before I start this post, I'd like to stress that I am certain this is not a bug with the PMDG 747.. But it was the weirdest thing I've seen (and kinda fun because I wasn't expecting it)..So.. what happened? Well I was about to start a long haul flight from Heathrow to Singapore.. as QANTAS.. I'd done all my pre-flight prep.. weights etc.. programmed my route, SID.. setup my performance parameters.. did my push and began taxiing to the hold, flipped on autothrottle ready for TO/GA.. 9R in this instance.. Got to the hold, strobes on landing lights on as I lined up... (LNAV, VNAV armed, TO/GA, TO/GA set as current modes.. F/D on etc etc.. flaps down 20 Green) everything was perfect.. as usual.. everything was going fine..So.. time to go.. given clearance.. engines slowly advance to 70% N1.. hold them there... everything stable.. heading just to the left of the centreline.. perfect.. TO/GA switches pressed.. THR REF on PFD.. levers advance to TO Thrust (in this case full thrust, no de-rate as I was very heavy).... 80knots.. and HOLD on the PFD... then I heard an engine spooling down.. looked at my upper EICAS.. and sure enough engine 3 was ramping down to idle.. HOLD still active on the PFD... I wasn't going to get the speed required for T/O now.. and V1 hadn't been called so it was abort time..Pulled off onto the taxi way.. checked everything over.. it looked ok.. nothing unusual... so I made sure I was good to go again.. and taxied back to the holding point for 9R.. As before.. going well.. THR REF.. then HOLD.. 80 knots.. 100knots.. 120knots... engine 3 then began to spool down.. another abort required!.. Rolled off the high speed exit.. and checked it over.. Now I'd got a brake overheat and wasn't going anywhere this time.. so it was a very.. gentle limp back to the nearest ramp..I had no idea what caused it.. some funny glitch in MSFS I was sure.. perhaps a rogue signal here or there.. I've never EVER seen it before it was quite odd... could only conclude MSFS sent a signal to the A/C saying I'd moved my throttles and therefore moved the throttles to idle..I subsequently took off without issue.. I've been flying with these same settings since getting this A/C for FS9 with my throttles for a good few months now.. will keep an eye on it in future..But overall is was quite good fun.. a problem was the last thing I was expecting because I never have failures set ON... Having one during the TO roll was something I was not expecting at all..Just thought I'd share that with you guys.. Like I said.. I'm not asking for "support" on this issue.. I am pretty sure after reflection I can guess what the culprit is (not PMDG).. Just thought you'd like to hear the story..CheersCraig

[downscc 1,327]

I guess if it were a Speedbird flight you'd just keep going on three, unless they've re-evaluated their procedures since that KLAX-EGLL flight.I've had a few odd things happen that I could never reproduce or isolate. I've suspected something like the panel state so I never create a new flight from the panel of an other saved flight and the oddities have decreased. If I create a flight I make a new panel state.. even if it is "exactly" just another cold and dark one.

[tf51d 284]

Did you check your failures settings? Maybe they are set to random?

[craig_read 43]

Dan,Must say your post did make me chuckle.. As captain in command I decided flying on 3 wasn't a good idea.. lol... Yeah normally I have no problems, I've not managed to reproduce it since actually.. it's all a bit strange but all good fun.As for my failure settings Tom.. they are set to off.. I think it's got something to do with a funny signal from my throttles.. Although I'm not entirely sure because I didn't move them during the takeoff after the TO/GA switch was pressed..Like I said.. it's not an issue for support to clear up.. It's not an A/C fault.. it's one of those strange things that MSFS does.. or perhaps it's just my PC..CheersCraig

[tunnelcat 1]

You may have the old 'noisy controller' input problems. If you have 'controls override' checked in the PMDG options, AFDS section, you will get weird behavior with both the A/T and A/P. My 747 was doing PARTIAL, no alarm (silent) disconnects of both the A/P and A/T during the takeoff phases. One of these glitches showed up as an engine going to idle during takeoff. Real exciting to say the least. It occurred with either engine 2 or 3 (or both) mostly in my case.You can either uncheck both of those boxes in the PMDG AFDS menu or set a larger dead zone for your controllers to filter out any input spikes.Kim

[craig_read 43]

Yeah I think it is the noisy controller issue.. just one of those things.. I have a bit of a sensitive rudder too so I've totally re-calibrated things and everything it a lot smoother..CheersCraig