Also I presume you have excluded more obvious reasons such as icing. This one gave me lots of trouble in my King Air 350, until I figured out I have to repeat that single surface de-icing cycle every now and then.
Also I presume you have excluded more obvious reasons such as icing. This one gave me lots of trouble in my King Air 350, until I figured out I have to repeat that single surface de-icing cycle every now and then.