Stall during climb

[Bidartarra]

Hello everyone,

Today I tried a derated climb profile to 37000ft, the issue I encountered was passing 30000ft, the plane stopped to climb and the A/T just rolled to idle out of the blue.

I had to disconect the AP but was never able to disconnect the A/T, I did the following

-Nose down

-VNAV deselected

-SPEED selected and manual selection of a speed

After that the plane was holding 30000ft nicely so I decided to give the A/P another shot, it didn't go that great :

I deselected the derated climb profile and reconnected the A/P what happen then was:

-Trim rolling full backwards

-Pitching Up over +4000ft/min (I saw that value fly by)

I stopped the flight then.

 

Did that happened to anyone?

 

[Litjan]

12 minutes ago, Bidartarra said:

Hello everyone,

Today I tried a derated climb profile to 37000ft, the issue I encountered was passing 30000ft, the plane stopped to climb and the A/T just rolled to idle out of the blue.

I had to disconect the AP but was never able to disconnect the A/T, I did the following

-Nose down

-VNAV deselected

-SPEED selected and manual selection of a speed

After that the plane was holding 30000ft nicely so I decided to give the A/P another shot, it didn't go that great :

I deselected the derated climb profile and reconnected the A/P what happen then was:

-Trim rolling full backwards

-Pitching Up over +4000ft/min (I saw that value fly by)

I stopped the flight then.

 

Did that happened to anyone?

 

Woah, that sounds like quite the ride! I fortunately haven´t experienced anything like that, and without a video of it (to see what modes you were in exactly) it is very hard to reconstruct what was going on... If you can recreate the experience with distinct steps to take so I can reproduce it, I would be very interested to hear them so we can fix that happening.

Thanks for the report, Jan

 

[Bidartarra]

3 hours ago, Litjan said:

Woah, that sounds like quite the ride! I fortunately haven´t experienced anything like that, and without a video of it (to see what modes you were in exactly) it is very hard to reconstruct what was going on... If you can recreate the experience with distinct steps to take so I can reproduce it, I would be very interested to hear them so we can fix that happening.

Thanks for the report, Jan

 

Hey, thanks for getting back to me Jan.

It was indeed quite a ride haha, I will try to recreate the flight and report back, it never happened before so I was quite surprised.

[Bidartarra]

So, I did try again today .

I was able to get to the Cruise altitude this time although I struggled and had to disconect VNAV and use V/S instead as the speed was falling behind the target and the plane couldn't keep up.

I'm gonna do some more digging because I think that:

1. I may have poorly choose my crz altitude (too high)

2. Or the climb profile is inappropriate (max thrust was 92.7 IIRC)

So back to the manual it seems

Edited October 10, 2016 by Bidartarra

[xm10922]

Reading your thread here I somewhat had a similar occurance.
I haven't done much flying lately so it might have been pilot error. Did a flight from PDX to SFO. I was climbing through FL270 for FL350 when the plane slowed down out of nowhere. The AT was engaged, AP was in VNAV and LNAV and was climbing nicely. Suddenly I noticed the airspeed decreasing slowly while I still was in the climb.
Engine Power was allright with N1 at ~92% (I did not select any derate) but still the plane was loosing airspeed (and groundspeed). It was quite windy with a side wind of ~90kts but that still wouldn't make the Aircraft loose so much speed.

I disconnected the AP, switched off the Auto Throttle, leveled off, matched the Auto Throttle, went full power and the plane was flying normally again. Activated AP and AT again, set LNAV and VNAV again and the plane was flying as it was supposed to again.

Will do the same flight again if I find time to and if anything out of the ordinary happens, I'll record it.

Edited October 20, 2016 by xm10922

[Tom Stian]

8 minutes ago, xm10922 said:

Reading your thread here I somewhat had a similar occurance.
I haven't done much flying lately so it might have been pilot error. Did a flight from PDX to SFO. I was climbing through FL270 for FL350 when the plane slowed down out of nowhere. The AT was engaged, AP was in VNAV and LNAV and was climbing nicely. Suddenly I noticed the airspeed decreasing slowly while I still was in the climb.
Engine Power was allright with N1 at ~92% (I did not select any derate) but still the plane was loosing airspeed (and groundspeed). It was quite windy with a side wind of ~90kts but that still wouldn't make the Aircraft loose so much speed.

I disconnected the AP, switched off the Auto Throttle, leveled off, matched the Auto Throttle, went full power and the plane was flying normally again. Activated AP and AT again, set LNAV and VNAV again and the plane was flying as it was supposed to again.

Will do the same flight again if I find time to and if anything out of the ordinary happens, I'll record it.

Hi,

Did you have heavy turbulence aswell ? And when you did lose your airspeed, did your climbrate increase ?

[xm10922]

Just now, Tom Stian said:

Hi,

Did you have heavy turbulence aswell ? And when you did lose your airspeed, did your climbrate increase ?

There was turbulence, I can't remember an increased climb rate while loosing airspeed. I was more focused on the airspeed and the climb rate needle not dropping below 0. So I didn't monitor the climb rate in detail, just roughly not going below zero.

Also it was blue skies, no icing conditions / no clouds.

[Tom Stian]

7 minutes ago, xm10922 said:

There was turbulence, I can't remember an increased climb rate while loosing airspeed. I was more focused on the airspeed and the climb rate needle not dropping below 0. So I didn't monitor the climb rate in detail, just roughly not going below zero.

Also it was blue skies, no icing conditions / no clouds.

I see.

I had a similar experience with losing airspeed while climbing. I have done a ton of flights with the IXEG 733 and never had any issue with this pre XP10.50.

So I wonder if it can have anything to do with the turbulence that was introduced with XP10.50.

Edited October 20, 2016 by Tom Stian

[Morten]

If this happens again, go in replay mode and take a screenshot of the panel just prior to the problems starting and after. Make note of aircraft weight.  Also make sure you didn't accidentally deploy the speedbrakes, flaps etc

[Tom Stian]

1 hour ago, Morten said:

If this happens again, go in replay mode and take a screenshot of the panel just prior to the problems starting and after. Make note of aircraft weight.  Also make sure you didn't accidentally deploy the speedbrakes, flaps etc

Hi Morten.

Just did a quick test to illustrate the issue.

Its really struggle to handle the turbulence at FL300+

It may be the overdone turbulence provided in XP 10.50.

 

 

 

[Litjan]

Yes, please make sure you updated to the latest XP beta (10.51r2)

An excerpt from the patch note for that 10.51r1:

• Turbulence reduced when using real weather.

 

Cheers, Jan

 

[Tom Stian]

XP10.51r2 will most likley be the final version. But will wait until is marked as final. Or even better (hopefully) wait for XP11. 

[Morten]

Hmm... I see you also have a climbrate of 2-3000 fpm just prior which is very high at that altitude/weight.  Might be a VNAV/A/T/vertical profile issue.  Thanks for the video.

[Litjan]

Ok, had a bit of time to look at the video:

Something unrelated to turbulence is going on. The speed cursor is stuck at 250, yet the magenta speed bug on the EADI is close to 340. The FMA is boxed all the time (it should stop after 10s). The vertical page says ACT CRZ - indicating the plane is in cruise mode, not in climb mode....

Not sure what is happening, haven´t seen that myself.

Jan

 

[Tom Stian]

8 minutes ago, Litjan said:

Ok, had a bit of time to look at the video:

Something unrelated to turbulence is going on. The speed cursor is stuck at 250, yet the magenta speed bug on the EADI is close to 340. The FMA is boxed all the time (it should stop after 10s). The vertical page says ACT CRZ - indicating the plane is in cruise mode, not in climb mode....

Not sure what is happening, haven´t seen that myself.

Jan

 

Thats because it is a replay. So the indicators you mentioned will be a bit off.

If you want and its needed I can make a new one.

[Litjan]

17 hours ago, Tom Stian said:

Thats because it is a replay. So the indicators you mentioned will be a bit off.

If you want and its needed I can make a new one.

Ah, ok - I didn´t know that - I thought it was a live taping of the actual event. I would say let´s see if it resurfaces with the new turbulence model in 10.51r2 and on, and then we can take a look.

Thanks, Jan

 

[Tom Stian]

@Litjan @Morten

Hi again

Did a new test with the final XP 10.51.

Used the same weather and same weights/performance etc.

And the result are maybe a bit better. But the low speed at the final 5-6000ft are pretty much the same.

It looks like the real problem starts when the climb target speed change from IAS to mach around FL270.

The video is not a X-Plane replay, but the speed is increased by 6 times. I have the video in nomal speed also if needed.

 

 

Edited October 26, 2016 by Tom Stian

[Rodeo]

Quite intriguing (sorry, I have no idea what's causing the behavior, I just saw there was a video and tought "oh, shiny!")