There appears to be an element of incriminating VGS instructors when it comes to the use of carb heat and associating this with engine problems. I'm not sure what evidence these conclusions are based on?
Squawking7700, I have met and worked with many VGS instructors, who over the years have displayed exceptional knowledge in all areas when operating the Vigilant. Operation of the aircraft was always carried out in accordance with regulations in force at the time as I'm sure is the case today.
I would be interested to know what aircraft type you refer to regarding the instructor's use of carb heat at all times.
