[BUG] A380 + stuck engines

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vasfmc
Posts: 4
Joined: 03 Feb 2011, 19:38

[BUG] A380 + stuck engines

Post by vasfmc »

Hi Folks,

We (the vasFMC team) are currently preparing a new release (version 2.1) which will also contain an 4 engine upper ECAM and FBW for the PA A380. I was doing testflights over the last weeks with your PA A380 and there is some strange behavior, which i did never encounter during my tests with your other smaller models:

During the climb, vasFMC is on OP CLB mode and the thrust is controlled by vasFMC to certain N1 values, so far so good. But, when i enter the cruise phase, when the MACH hold mode drops in, the engines won't respond to the thrust commands for about a minute.

E.g. if i have a thrust of 105% at the time i transit from the climb to the cruise phase, the engines are stuck at this value for about a minute, altough the thrust levers are slowly going to IDLE by the MACH hold A/THR mode, which is trying to hold the given CRZ mach. During that "engine stuck" phase, the speed reaches Vmax/Vmmo until the engines are responsive again and the CRZ speed is captures by the A/THR MACH hold mode.

I am quite sure, that this is no vasFMC issue, because i never experienced anything like this in any other plane, and i did testings with your A318, A319, A320 and the Posky A330 and A340.

Does anyone have a clue what is going on here?

Thanks + Best regards,
Alex Wemmer (main vasFMC developer)

Derek Mayer
Posts: 236
Joined: 02 Jul 2009, 16:13

Re: A380 + stuck engines

Post by Derek Mayer »

I have had this issue happen a couple of times, always when reducing the throttles from values above 100%. The difference between the 320 fde and the 380 fde is that the former limited N1 values at 95% or so, even at full throttle. The 380 will easily reach 110% or more at full throttle, meaning the pilot himself needs to reduce the thrust levers to maintain 95% N1. Failing that, reducing the thrust levers from their max position (about 105-110% N1) does create a delayed reaction but I really don't know why.

If you programed the gauge to maintain no more than 95% N1 at any given time (and most importantly, during the climb phase), the issue should go away.

vasfmc
Posts: 4
Joined: 03 Feb 2011, 19:38

Re: A380 + stuck engines

Post by vasfmc »

Well, it is not unusal to set >100% thrust at greater heights in real life, altough this depends on the engines mounted to the aircraft.

I am wondering if this issue goes away, if the thrust levers are not set to 100% but to 99% or such - i will give it a try...

Brett-Hill
Posts: 185
Joined: 26 Sep 2009, 23:01

Re: A380 + stuck engines

Post by Brett-Hill »

from my experience it would have to be atleast 5% lower

kevin0475
Posts: 2
Joined: 19 Sep 2010, 17:21

Re: A380 + stuck engines

Post by kevin0475 »

Any fix for the stuck engines yet?

WarthogCC
Posts: 9
Joined: 21 May 2015, 21:22

Re: [BUG] A380 + stuck engines

Post by WarthogCC »

I know this is an old post but it's relevant and the topic still exists.

I can add that it IS NOT a vasFMC issue, nor is it an Autothrottle issue. If you control the throttles manually the problem is still there. As long as you don't go past 92-93% they won't stick.

But I discovered one thing interesting: The amount of time they get stuck is exactly proportional to the amount of time the throttles were past that threshold. i.e. If you push the throttles to 95-100% for 5 seconds and then back them down, the engines will stay stuck for 5 additional seconds. If you do it for 20 seconds, they stay stuck for 20 seconds. Get the idea?

4 years later and people are still having this problem. Geez.

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