Irritating attitude behavior while at cruise phase

[Alaaar]

Dear all,

I really need to resolve this issue or the constellation could be unflyable which is a shame for sure......

OK, at cruise level usually 12,000ft using the  KFC 225, the plane is shaking in a regular way also reacting to clouds normally, then suddenly without any known reason, it goes into a dive for 3,000 to 5,000 then stabilize briefly to start climbing until reaching cruise level again......Again in 5-10 minutes, it happens again using maximum decent and climb rates ......At a 250nm trip, it could happen 3-5 times ......Also at approach phase, it occurs, however, I disconnect the autopilot not to crash when I do the plane responds normally. 

I fly other planes like DC-6B, JS41, and DC-3 at similar conditions and nothing like that ever happens.

I have no clue is it the constellation issue or AS variables or something else?

Any help would be highly appreciated, please 

Alaa Riad 

[harrry]

icing?

[Alaaar]

4 hours ago, harrry said:

icing?

I have no idea I will read the manual to see about icing protection ......Thanks Harry 

[ThomasAH]

You might want to enable carburetor heat, even for aircraft who don't have this, with the "H" key. This is a known issue in FSX and probably in P3D as well.

[Alaaar]

Gentlemen, thank you for helping me, it looks like it's one of the three or all of them together, last night I made a flight and it was surprisingly normal with nothing out of the ordinary, however, you know FSX.....I have to do more flights to be sure what was really going on but your guesses were I think right, it has something to do with deicing system or carburetor heat system or simply pressing "H" at the beginning of the flight .......I will report after more testing 

Many thanks 

Alaa

[Alaaar]

Hello Again, after few flights with the Connie that appeared to be normal, it happened again the aircraft plunged about 9,000ft in less than a minute until I disconnected AP and assumed control without known reason......It's not happening to other planes I have such as PMDG and FSL and others ......FYI

[Alaaar]

OK, another update I made few flights at the Caribean about 5 or 6 of them,  it was very stable.....So to me, it's obvious that the plunging thing is because of low temperate and perhaps icy weather?..... I have no idea how to resolve it since I tried everything earlier but I thought to report back 

Many thanks