During cruise airspeed suddenly decreases

[Kebas]

Hi all,

I've flown many flights in this great A2A aircraft without problems, but now I don't understand whats happening?
I did this flight 2 times and it happened also both times on about the same distance.
The flight was from PAJN to CYZT in Canada with Active Sky as weather engine.
Weather was a little cloudy and sometimes some rain.
Cruise altitude is 11000 feet en outside temp at this height is about -17 dgr. C.
Autopilot is on with NAV and ALT hold.
Pitot Heat and Prop De-Ice are both on.
Props on 75% percent and leaned as usual at about 38 percent.
After about 400nm the airspeed starts to degrease without any reason I know.
The sound of the engine is normal. Temps and Cyl. Pressure normal. Prop speed stays the same.
The airspeed drops further and further and I can do nothing to stop this.
At least the airspeed drops below 80 knots, so I have to do an emergency landing or crash!
The dropping from about 120 to 80 knots is in about 8 to 10 minutes.

I've installed the latest update.
I tried to change the mixture, decrease the altitude, change the prop setting. No succes.
Could it be Icing? But how to prevend this?

Anyone a suggestion what might the cause of this?

Thanks in advance.

[Hook]

Symptom of icing. Get above it, get below it, turn around or land. Avoid freezing rain.

Hook

[Kebas]

Symptom of icing. Get above it, get below it, turn around or land. Avoid freezing rain.

Hook

Thanks for the confirmation Hook.
I thought on this.