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Loosing speed midflight


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Hello,

 

today I had a loose of speed midflight from EDDF to ESGG and the plane started to descent. I already had reached the cruising altitude. With a SAT -48 / TAT -37 and no visible moisture I would rule out icing. This is the state during the started descent:

prob1.thumb.PNG.c11e6d95301ae54625c5716b1c753881.PNG

 

So I disabled the AP and took over the control of the plane. I noticed that the stab trim has some very high value (around 14). So i corrected the trim and the plane stabilized:

prob2.thumb.PNG.00d23d014112a5785b1c38c702dfaa45.PNG

 

So I activated the AP again, but it then immediality put the trim back to 14 which again destablized  the plane:

prob3.thumb.PNG.b9d8d7664c6a5b98a894dc2133123b64.PNG

 

This problem remained during the rest of the flight. So any idea why the stab trim went bonkers?

And what could be the reason to loose speed midflight? I did not open the settings menu, so we can also rule this out.

 

Marcus

 

 

 

 

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  • marcus_77 changed the title to Loosing speed midflight

Hello. I have the same issue. During cruise at FL200, I started losing altitude. I also noticed that the Stab trim was set to max by the autopilot. I had anti-ice on the whole flight and the SAT and TAT weren't even that low.

My plane's center of gravity seemed alright and within boundaries. Not sure what else might cause the problem. I'm using Honeycomb Alpha Yoke and Bravo Throttle if it makes any difference.

 

Apologies for the blurry image, I was flying at night. In any case, I think you can still see the Stab trim is at max.

 

20210620215434_1.thumb.jpg.6eaaa8f59cc8daa160f5f6701e02aed5.jpg20210620215446_1.thumb.jpg.90bcad688d7a139353361cbcb3e65d08.jpg

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I can see by the pictures that these are piloting errors and not bugs!

Watch your speeds more carefully and correct the thrust manually, as there is no autothrottle.

 

If you corrected the situation with the AP disengaged, then try switching the FD to off and on again before re-engaging the autopilot. If you don't do that the  autopilot will mess up again......... bug or somekind of memory function???

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I have not had such a problem, but in the FSX and P3D past of the CRJ, when the speed dropped in cruise, the AP would first try to maintain FL by raising the trim to maximum. If the pilot does not increase the thrust, the speed will drop more and more until stall occurs.

 

After switching off the AP at this max. position, I could no longer change the trim with the keyboard as usual, only the buttons on the yoke reacted and I could set the trim back to normal values.

 

No AntiIce on FL200, or did you receive an Ice warning?
AntiIce costs valuable thrust.

 

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vor 1 hour , Danny Vincken sagte:

I can see by the pictures that these are piloting errors and not bugs!

Watch your speeds more carefully and correct the thrust manually, as there is no autothrottle.

 

If you corrected the situation with the AP disengaged, then try switching the FD to off and on again before re-engaging the autopilot. If you don't do that the  autopilot will mess up again......... bug or somekind of memory function???

I know that there is no autothrust. And as you may notice, there was an N1 of 84.5 and an N2 of 87.9 which I would assume should be sufficient to maintain speed. So maybe the plane was overloaded, but on the other hand it was no problem to reach the cruising altitude of FL390. The ZFW was 27750kg and fuel was 3649kg. The weight was definitely set via the tablet as this was a VA flight which is not recorded if the weight is not according to the briefing.

Could the strong tailwind be a problem?

 

Regarding the stab trim: well, I would assume that the control of the stab trim is a closed loop so such a "memory function" would be a really strange feature. But maybe one of the RW pilots can explain why it does this here.

I will try to disable/enable FD next time this happens (which will hopefully be not too soon).

 

Does the Aerosoft support have any opinion on this?

 

Marcus

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1 hour ago, Hoffie3000 said:

No AntiIce on FL200, or did you receive an Ice warning?
AntiIce costs valuable thrust.

 

After Reading through the FAQ, I realised this may have been the cause of my issue. 

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Anti Ice on at FL200 should not take away so much thrust as to be unable to fly level, don't be fooled by a FAQ telling you something silly like that. We would never be able to get anywhere in the real CRJ if that was the case.

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8 hours ago, CRJay said:

Anti Ice on at FL200 should not take away so much thrust as to be unable to fly level, don't be fooled by a FAQ telling you something silly like that. We would never be able to get anywhere in the real CRJ if that was the case.

Thanks for your input. As I'm not a real world pilot, I don't really know what else to attribute the fault to. I'm just hoping someone had the same issue and found out what's the cause and fix or if someone can point out what I did wrong with the flight. 

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On 6/22/2021 at 1:31 PM, Danny Vincken said:

I can see by the pictures that these are piloting errors and not bugs!

Watch your speeds more carefully and correct the thrust manually, as there is no autothrottle.

 

Would be interested to know how you judge the issue as pilot error based on screenshots AFTER the initial issue and pictures that are showing a clear stab trim problem...

 

3 hours ago, mori_art said:

Thanks for your input. As I'm not a real world pilot, I don't really know what else to attribute the fault to. I'm just hoping someone had the same issue and found out what's the cause and fix or if someone can point out what I did wrong with the flight. 

 

I have no idea either unfortunately. The stab trim definitely should not just pop to the last position used by the autopilot once you have corrected it and then engage the autopilot again, so something is wrong there. But the initial loss of speed makes no sense, the only thing I can think of is this 'ghost' speed brake problem, where it extends without the plane telling you it is extended. If you encounter the issue again, perhaps try cycling the speed brake with a keyboard or button command to see if that helps.

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12 hours ago, CRJay said:

I have no idea either unfortunately. The stab trim definitely should not just pop to the last position used by the autopilot once you have corrected it and then engage the autopilot again, so something is wrong there. But the initial loss of speed makes no sense, the only thing I can think of is this 'ghost' speed brake problem, where it extends without the plane telling you it is extended. If you encounter the issue again, perhaps try cycling the speed brake with a keyboard or button command to see if that helps.

Thanks. I'll try readjusting the speed brakes to extend and retract the next time I encounter the issue. As much as I'm careful with throttle input, I'll also watch out for the Anti-ice and use it when it's actually needed. I did leave it on the entire flight so that was careless. Still, I enjoy flying the CRJ surprisingly even more than A32NX. Much more interactive. I appreciate your help.

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17 hours ago, CRJay said:

Would be interested to know how you judge the issue as pilot error based on screenshots AFTER the initial issue and pictures that are showing a clear stab trim problem...

 

I have made 100+ flights with the plane, and i encountered the problem a few times. it occurs when the throttle setting is to low for maintaining level flight on a specific altitude. To compensate the A/P pitches up resulting in further speed loss as it tries to maintain altitude, so the A/P pitches up some more etc etc... till the point the plane can't keep it's altitude anymore. At that point applying more throttle doesn't help anymore, you need to disengage the autopilot and lower the nose and speed up. 

 

Now to your question: i can see it is pilot error because of the speeds showing on the pics, because at that point (<170 kts) you are way to late with applying more throttle.

Is there a bug re-engaging the A/P after this issue?..... yes there is!

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No. we simply have never seen this.  Nor have any of out testers seen thus.

 

As so often in MSFS we suspect control binding play a role. Delete all, bind only the most essential and see if you still see this.

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Thanks for the reply. So the binding of moving the trim up/down may be the problem?

When I think about it, two questions arise:

What type of control binding would that be that is only active when the AP is active?

When such a binding would be the problem, why is the AP still active? Moving the stab trim manually (it’s bound to two keys at my TCA  Stick) would cause the AP to disable, right?


And shouldn’t such a problematic binding cause issues in every flight?

 

Marcus

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  • Aerosoft

Some of the default MSFS control bindings might not work exactly like they should with the CRJ since CRJ uses custom code. So it might not interact correctly with other systems like autopilot in some cases.

Speedbrake is another binding that could put full speedbrakes for the aircraft aerodynamically without any visual sign that you have speedbrakes deployed.

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i have also had this issues multiple times. 

i am surprised that mathjis you are saying none of your testers saw this or came across this. my autopilot does the same issue the OP describes, even in clear weather, proper load and balance etc. 

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vor 16 Stunden , flyingravi sagte:

i have also had this issues multiple times. 

i am surprised that mathjis you are saying none of your testers saw this or came across this. my autopilot does the same issue the OP describes, even in clear weather, proper load and balance etc. 

Third or fourth tme I had the same problem... Best weather normal loading today... Green marker on performance page was ok when I started. I didn't pushed any button at the Tablet after configuration and when the problem appeared at FL380 after 25 minutes at this FL, green marker was out of view at performance page when I noticed stall...

Nose down, winning speed and when I had round about M0.73 again at FL270 I activated the autopilot and nose started to  fly to the moon.... No chance to get CRJ back to a normal control status.. :(

 

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54 minutes ago, tribejagd said:

Third or fourth tme I had the same problem... Best weather normal loading today... Green marker on performance page was ok when I started. I didn't pushed any button at the Tablet after configuration and when the problem appeared at FL380 after 25 minutes at this FL, green marker was out of view at performance page when I noticed stall...

Nose down, winning speed and when I had round about M0.73 again at FL270 I activated the autopilot and nose started to  fly to the moon.... No chance to get CRJ back to a normal control status.. :(

 

But what does you AP Mode annunciators display?  Did the AP ever actually capture the Altitude?  is it possible that it was somehow in a VS Mode trying to climb back up?  Speed mode won't pitch the nose up unless your speed is far above the speed you have selected to climb with.... so unless you turn speed mode back on and it is well below your current speed then it should not pitch up or only until it reaches the speed that it will then pitch down to capture that speed

 

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vor 38 Minuten, LesOReilly sagte:

But what does you AP Mode annunciators display?  Did the AP ever actually capture the Altitude?  is it possible that it was somehow in a VS Mode trying to climb back up?  Speed mode won't pitch the nose up unless your speed is far above the speed you have selected to climb with.... so unless you turn speed mode back on and it is well below your current speed then it should not pitch up or only until it reaches the speed that it will then pitch down to capture that speed

 

 

It was definitive a stable flight... Had this issue now again cause I started the flight again after my last post rd. about two hours ago... round about 90 minutes no problem stable at FL380... than abnormal things...  lost speed, nose down, for getting speed again, activated and deactivated spoilers (cause I have read that here in the forum) trimmed it at round about 6.8, stable flight, M0.78, activated the autopilot in speed mode, thrust was set in climb mode... CRJ tooks its nose up again flying to the moon in seconds, airplane overloaded, game over...

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25 minutes ago, tribejagd said:

 

It was definitive a stable flight... Had this issue now again cause I started the flight again after my last post rd. about two hours ago... round about 90 minutes no problem stable at FL380... than abnormal things...  lost speed, nose down, for getting speed again, activated and deactivated spoilers (cause I have read that here in the forum) trimmed it at round about 6.8, stable flight, M0.78, activated the autopilot in speed mode, thrust was set in climb mode... CRJ tooks its nose up again flying to the moon in seconds, airplane overloaded, game over...

what was the Route and "time of day ish local to the dep airport" I will give it a try a little later to see what results I get...  oh and also W/B and fuel as well so I can try to match

 

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Dear Aerosoft Support Team,

 

are you still convinced that this is a problem of bindings? We have now some other users that have a similar issue like I reported.

And please note that one user reports this issue in another thread:

 

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Sure

vor 2 Stunden , Mathijs Kok sagte:

Well bindings could most certainly be a reason!

 

But let's start with what is asked here

 

 

Sure, here is the info about the flight from my VA briefing:

DEP  EDDF/  STD  19.06.2021 11:00Z
ARR  ESGG/  STA  19.06.2021 12:40Z
ATS-ROUTE
¯¯¯¯¯¯¯¯¯
MARUN Y150 TOLGI DCT ALASA DCT GOTEX N873 LOBBI
----
FL STEPS EDDF/F390
FUEL TOTAL      3.649
ZFW       27.750

 

You can see the position where it happened in my first screenshot of my first post in this thread.

I don't know whether this has something to do with it but there additional notes about the flight:

  • Long leg between two waypoints
  • Strong tailwinds

 

BTW: Here is another user reporting the exact same issue:

Back then, it was assumed to be an an icing issue.

 

Marcus

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