Something weird going on

[Bubblehead]

The last few days I've noticed the following:

P51 Mustang smoking and on fire shortly after takeoff.
Smoke coming out of jet fighter exhaust as it takes off (no fire this time)
A cloud surrounding the aircraft as it sits on the runway ready for take off.

Note:  Does not happen to all aircraft.
           Does not happen all the time to the same    aircraft.

Only thing I was doing before all these start to happen was I was loading some add-on sceneries. However, I removed those sceneries and nothing has changed. Is this an FSX problem or an add-on problem. Also I get this warning on the top left corner of my screen saying " Aircraft not defined". What does that mean?

[Tomcat5]

Turn off "engine stress causes damage" or something in realism settings.  You are over stressing your piston engine's manifold.

[B_7772]

When flying the default P-51, you can only go full throttle for a short amount of time.

[Bubblehead]

That cured it. I unchecked the engine damage box in the Realism. That also cured the other problems such as trailing smoke and the clouds surrounding the aircraft at take off.

Thanks.

[Brett_Henderson]

Leave engine damage turned on, and just fly it carefully