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Helicopter Systems | Get It Right the First Time

Posted 37 days ago ago by Admin




A few weeks ago, I conducted a Private Pilot exam in a Robinson R22 helicopter. My helicopter systems questions often begin with correlative level questions requiring the student to understand many aspects of the system to provide a comprehensive answer. This level of questioning provides a path for the applicant to demonstrate higher order of thinking skills or HOTS as the FAA refers to this in the FAA instructors handbook.

The question asked was simply how the engine separates from the drivetrain in the event of an engine failure. Although the question would seem basic when measured by the fact the person being asked just spent the past several months and more than 60 flight hours operating this same aircraft. However, the response was not just incorrect due to a slight misunderstanding that sometimes occurs during early pilot training, the answer provided was wrong to the point an incorrect component was identified. Additionally, the applicant provided a comprehensive description of how the incorrect component functions in a manner consistent with my original question.

In the Robinson R22, the sprag clutch which enables this function is located within the upper sheave or pulley. This would be the location that the v-belts travel when engaged to the drive shaft via the electric clutch. When I asked the applicant to explain how the engine disconnects from the drivetrain during an engine failure, the applicant opened the cowling and pointed at the main transmission. He further explained that the gears within the main transmission are a sprag type, and when the engine loses power the internal transmission gears collapse and the rotor continues to turn.

I understand that instructors may teach information from many differing aspects, so my initial effort was to fully understand the perspective the applicant may have been taught this information and explaining this system. After several follow-up questions and conversation on the subject, it was obvious the applicant had been taught this system incorrectly. Although other weaknesses were identified, all other systems questions were explained by the applicant correctly.

After briefing the applicant why this answer was unsatisfactory and completing the required paperwork, it was time for a healthy chat with the recommending instructor. Although the instructor understood the R22 sprag clutch function and location, he went on to describe the sprag function of the main gearbox itself. When asked where he learned this information, he stated he had studied a training manual from a multi-engine helicopter to help understand a broader selection of helicopters, and this manual described a similar sprag system at the transmission. It was the instructor’s assumption that all helicopters functioned in a similar manner.

To be clear, becoming familiar with other helicopter systems is a great way for an instructor to diversify knowledge, however departing from published training material and specific helicopter information when teaching new, influential students should be avoided. New pilots in training depend on their instructor to aid in their development of instructional primacy. When this knowledge is compromised, it’s nearly impossible for the student alone to get on track with the correct information.          

In this situation, the instructor taught two completely different systems with the intent of enhancing the student’s knowledge. Due to the student’s low experience, this effort only caused confusion, misunderstanding, and an unsatisfactory checkride! 

About Randy: 
Randy Rowles has been a FAA pilot examiner for 20 years for all helicopter certificates and ratings. He holds a FAA Gold Seal Flight Instructor Certificate, NAFI Master Flight Instructor designation, and was the 2013 recipient of the HAI Flight Instructor of the Year Award. Rowles is the owner/president of Helicopter Institute.

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