Mark Edward Pilger - Comments

I have given much thought to what would be required to make a propeller auto-feathering. There are numerous issues to be addressed. Will there be an interlock to disable the starter motor until the prop is fully unfeathered? Can the engine run with the prop feathered without being damaged? A good friend has an aircraft that has hydraulically operated retractable gear but it has a manual release that will allow the gear to come down and lock. Will there be a similar provision for an auto-feathering prop? If not, what is the justification for the corresponding reduction in safety by not having failsafe operation? It is logical that light sport aircraft should be restricted in the complexity of their systems. As such the goal is to make the prop feathering operation transparent to the pilot. However, as a professional engineer and an all around mechanical guy, as well as a flight instructor, it seems to me that meeting this challenge might require inclusion components whose sole purpose is to prevent the engine from starting as well to prevent the prop from un-feathering unless the engine is started. While the goal is admirable it seems that the pursuit of it may have wandered past a point of diminishing returns in terms of safety in that the risk of failure due to mechanical complexity of a completely auto-feathering system may outweigh the risk of failure due to pilot error. The majority of motor-gliders have feathering props that are mechanically operated. This design clearly works well and is the product of decades of design evolution by the best minds in the business. A feathering prop is so necessary to the proper operation of a glider that a fixed pitch prop should not be considered. As a flight instructor I know that there are some students out there that may be challenged by aspects of piloting an aircraft. The operation of a manually feathering prop does not stand out as being the straw that broke the camels back in terms of complexity and would only be consistent with allowing retractable gear for light sport gliders and amphibians. We, the instructors, should bear the responsibility of training light sport pilots in the proper operation of these simple systems.