What happens here? Icing? 4 time same flight, same nose-down crash

[SupraJari]

OK, I've flown this leg four times now, everytimes it ends with nose-down and crash. The leg was EEKA-ULOO and I was flying with real weather from Xplane.

This was my first recording inside Xplane and I didn't notice resolution was so bad 640*

https://www.dropbox.com/s/jg3hoa5kq9a1jw4/LES_Saab_340A - 2021-03-21 11.12.46.avi?dl=0

This is weather from littlenavmap (pic1):

As I started my descent from 18000ft I turned on de-ice (the settings can be seen on video at start 00:05 , prop max, engine on, auto-cycle cont, pitot heat).

-Steady descent 1000fpm towars 3000ft IAF PS009 I think)

-flying into cloud at 01:10 things start wobbling, AP can handle no biggie. Wind is steady 19 knt from from 5 o'clock

-01:20 see speed jumps around and soon I decide to increase power

-01:45 pretty much stablized again, 01:51 as you can see weather was a mess.

-02:50 speed start to drop. Wind didn't change (at least on EADI).

After that I have no idea what happened, but it happened 4 times on a row. As seen no trim issue (this was discussed recently), trim is at 1 or so.

-03:10 here we go, AP can't handle it anymore. Switching to manual flight, full throttle. VS is 3500fpm.

I was about to turn to approach for RW19 and wind was from 200.

Any comments welcome.

 

 

Edited March 21, 2021 by SupraJari

[SupraJari]

Short reply, tried to takeoff from same airport ULOO, real weather. Didn't get over 4000ft until same symptoms and nose-down. Same settings for de-ice. This time trim was out of limits when AP gave up but I corrected it ASAP.

Edited March 21, 2021 by SupraJari

[Milan Bogicevic]

Now that you say it i noticed that on cont auto cycling anti-ice lights cycle only once and not again(maybe a bug?), altho i didn`t fly into serious icing yet since tha last update only through some light rains. Might test later with custom weather.

[SupraJari]

I think it's supposed to run on timer (there's timer-light?)  I though that it would run constantly too but I monited it and it didn't.

Milan, try to take off NOW from ULOO  really bad...

[Milan Bogicevic]

I might later, sadly cant right now.

[SupraJari]

Here's the weather now, trying takeoff once more.

 

Edited March 21, 2021 by SupraJari

[N1K]

Looks very much like an ice induced stall.
Only thing I can spot immediately is HP BLD valves should be open with the boots on.
Around the 30 second mark the power is probably bordering insufficient to inflate the boots and would have triggered a master caution, ice protection, timer light on.
Don't think its modeled.

Personally I would suggest x-plane ice accumulation is incredibly aggressive, and they use some 1940s rubbish logic when it comes to boot de-ice.
it was most likely what would have been severe icing if it built up as quick as XP does.

 

 

 

Edited March 21, 2021 by N1K

[JGregory]

2 hours ago, Milan Bogicevic said:

Now that you say it i noticed that on cont auto cycling anti-ice lights cycle only once and not again(maybe a bug?), altho i didn`t fly into serious icing yet since tha last update only through some light rains. Might test later with custom weather.

There is a 3 minute gap interval cycles.

[N1K]

Playing around with it under those conditions:
The ice accumulation ratio, hopefully I'm wrong, is the percentage of ice compered to the aircraft weight by the looks of the internet?
If that is the case, then X-Plane is adding 8 ton per minute in ice to that airframe.
Super duper extreme ungodly apocalyptic severe icing encounter.

 

Edited March 21, 2021 by N1K

[sirtopper]

I use this fantastic addon which allows you to deice before you depart

https://forums.x-plane.org/index.php?/forums/topic/166672-de-icing-tool/

 

and then this equally useful addon which pops up a diplay of any icing occuring on your aircraft.

https://forums.x-plane.org/index.php?/files/file/50510-popup-icing-display/

These might help

[sirtopper]

3 hours ago, SupraJari said:

OK, I've flown this leg four times now, everytimes it ends with nose-down and crash. The leg was EEKA-ULOO and I was flying with real weather from Xplane.

This was my first recording inside Xplane and I didn't notice resolution was so bad 640*

https://www.dropbox.com/s/jg3hoa5kq9a1jw4/LES_Saab_340A - 2021-03-21 11.12.46.avi?dl=0

This is weather from littlenavmap (pic1):

As I started my descent from 18000ft I turned on de-ice (the settings can be seen on video at start 00:05 , prop max, engine on, auto-cycle cont, pitot heat).

-Steady descent 1000fpm towars 3000ft IAF PS009 I think)

-flying into cloud at 01:10 things start wobbling, AP can handle no biggie. Wind is steady 19 knt from from 5 o'clock

-01:20 see speed jumps around and soon I decide to increase power

-01:45 pretty much stablized again, 01:51 as you can see weather was a mess.

-02:50 speed start to drop. Wind didn't change (at least on EADI).

After that I have no idea what happened, but it happened 4 times on a row. As seen no trim issue (this was discussed recently), trim is at 1 or so.

-03:10 here we go, AP can't handle it anymore. Switching to manual flight, full throttle. VS is 3500fpm.

I was about to turn to approach for RW19 and wind was from 200.

Any comments welcome.

 

 

Difficult to see on the video but it looked like your Hi pressure bleed valves where closed. Not sure if this would have affected these systems

The systems which require bleed are:

• Wing & stabilizer inflatable boot deicing

• Engine split lip & inlet guide vane anti-icing

 

[SupraJari]

I think you are right, those valves might have been "untouched" and by default they are closed. This is mostly because built-in checklist does not mention anything about them until "Approach" (HP Valves "Set"...umm ok). Also after landing checklist says "HP Valves (CLOSED)".

I think checklist is missing setting them to AUTO somewhere. I did some reasearching and seems that they should be set to AUTO before takeoff?

More info about ice protection of Saab 340:

https://sites.google.com/site/sf340com/iceprotection

[JGregory]

I just checked the de-ice systems in the Saab and they are working as they should.  If you are unhappy about the way ice accumulates I suggest you file a report with Laminar.

[N1K]

9 hours ago, SupraJari said:

I think checklist is missing setting them to AUTO somewhere. I did some reasearching and seems that they should be set to AUTO before takeoff?

They go with the boots.

Entering Icing conditions (+5c and visible moisture)

Engine anti-ice on, boots continuous and HP auto.

-6c Props to norm, -12c props off then up to max.

 

Exiting icing

Props can go straight to off

5 mins later engine anti ice off

9 minutes later or temp +6c boots off and HP closed.

 

 

The problem you have is Laminar for some reason believe in ice bridging, so they coded boots to do nothing initially until there is a heap of ice on the plane, by that point its already struggling. Combined with the rate it accumulates it will quickly overwhelm the aircraft. Turboprops typically don’t have that much power to overcome it.

[SupraJari]

17 hours ago, JGregory said:

I just checked the de-ice systems in the Saab and they are working as they should.  If you are unhappy about the way ice accumulates I suggest you file a report with Laminar.

My mistake (HP valves off), I see no reason to complain. My only question at the moment is: Should built-in checklist include setting HP valves to Auto at certain point (like before takeoff)?

I've got lot of new info from this thread, thanks to all. N1K, will include that to my checklist