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Oct
07
2024
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Posted 75 days ago ago by Admin
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About a year ago, I was conducting pilot training for a Part 135 company, which was a relatively new customer. Prior to FAA approval to conduct this training, I conducted a review of their Part 135 training program to determine their differences from our training. Most often, a VFR Part 135 helicopter operators training program is going to be quite like another. Of course, some differences will always exist. The question is whether those differences require additional training and checking.
During the review of this company’s training program, I noticed a statement regarding the conduct of autorotation training that said, “at no time shall the throttle be reduced during autorotation training maneuvers.” This immediately got my attention. My initial thought was: If you don’t close the throttle, how are you practicing autorotations?
I engaged the operator for a bit of clarity. I was advised that the company had previously incurred expenses due to an overspeed that occurred during power-off autorotation training, so a company decision was made to only lower the collective and simulate an autorotative descent profile. Is this even legal? was my initial thought. Not to mention all the attributes of a power-off autorotation, which may include high/low rotor rpm, glide variation, and the ability to recognize the initial onset of an engine failure.
I turned my thoughts on this topic into an articulatable question and engaged the FAA for an answer. The immediate response from the FAA was one of disbelief and agreement. The FAA was clear when stating “the operator must reduce the throttle or how can you complete the power recovery requirement of the maneuver?” I was relieved. I’d found support from the FAA and now a remedy to the situation was soon to be had. Not so fast!
A few days later, I received a call from a helicopter-qualified FAA Inspector that I have known and worked with on many initiatives over the years. His call was to discuss this topic and curtail any concerns I had. The FAA believed this practice didn’t take away from safety or quality of training. The Inspector provided details of his military training experience in the UH-60 Blackhawk, and how they never reduced the throttles during their autorotation training events. He stated his initial training was in a Bell TH-67 helicopter and that he had completed a multitude of autorotation’s during initial training. It was his belief that there is little difference between a power-on or power-off autorotative profile. My response: I couldn’t disagree more!
The thought that lowering the collective with power applied to the main rotor would provide equivalent training benefit is naïve at best, and in some cases ignorant of the elements involved in single-engine autorotation training.
The first major difference is recognition of an engine failure using the energy change or reaction of the airframe to the loss of power. It is the ability of the pilot to immediately recognize and react in this situation. This will ultimately allow the pilot to either successfully enter the power-off profile or lose the energy of the rotor rpm and not survive the event. Respecting that a trained and qualified helicopter pilot made the decision that these maneuvers were similar led me to ask, “How did this discussion come about?”
I was told that several operators incurred engine and rotor rpm overspeeds during autorotation training and preferred not to reduce throttle. It was the operators that believed conducting a power-on descent minimized both the chance of overspeeds due to throttle manipulation and reduced the risk of high-vertical speed accidents if the power remained on throughout the event.
Truth be told, reducing the collective in most helicopters with the throttle remaining in the power-on position will enhance the chance of an overspeed, not decrease it. Additionally in many aircraft, the engine will follow the rotor rpm and an overspeed of the engine may also occur using the power-on autorotative profile procedure. Is this preventable? Of course, with a qualified pilot or instructor that understands these variables and the required corrective actions, they can negate any overspeed issues. Training is key!
I would offer an alternative solution: Utilize a qualified instructor pilot that has the skills and ability to conduct proper power-off training and not overspeed the helicopter. This approach, utilized for decades, provides the pilot with the additional experience to accurately perceive critical engine failure elements such as low rotor rpm, ability to vary glide distance, accurate flare altitudes and timing of pitch application for ground contact, and much, much more.
In early July 2024, I engaged the helicopter community via social media asking their opinion regarding this topic. Without question, the resounding response was that power-off autorotative training is the right way to go. All the aspects of the pilots feel related to the energy of the autorotative maneuver is lost when the engine remains driving the rotor system during the descent profile. There is no correlation between a power-on and power-off autorotative descent profile other than you’re headed to the ground. To be more specific, the life savings skills that would be taught during autorotative descent training are not achievable when the throttle remains on. This dilutes the training effort.
It is important to note this discussion has nothing to do with power-on or power-off landings. Were only discussing the descent profile prior to the flare of the maneuver.
I don’t know of any high rotor RPM related autorotative helicopter crashes, but I know of many helicopter crashes with loss of life related to low rotor RPM. The use of power-on autorotative descent profiles eliminates the low rotor rpm training opportunity, thus limiting the pilot’s ability to survive such an event, especially when survival is the goal.
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