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Friday, May 30, 2014

Autorotation Plus

Spitfire Aerospace develops a new system that will extend powered RPM time in the event of an engine failure.

By Keith Cianfrani

Keith Cianfrani
Imagine hovering for a local news station over a large city at night, filming a story when your engine fails and you are forced to make an autorotation to a suitable area that you can’t actually see and hopefully no trees, poles wires or cars will be in your flight path. This is a situation you do not want to be in. However, you have power to the rotor system with full operating rotor RPM which allows you to find a suitable landing area a mile or two away and conduct a safe landing. Thus, there was no need to execute an autorotation. Having experienced an engine failure while flying over Philadelphia, I would welcome any assistance in allowing me to land with power to the rotor system after an engine failure. What, you may ask, are we talking about? It’s called the Autorotation Plus Program.

All helicopters, large or small, auto-rotate at about the same forward airspeed of 60 to 80 mph, at a descent rate of 1,200 to 1,800 feet per minute. Helicopter pilots must have a solid understanding of the autorotation maneuver while they are in initial training, but there is no more training once they receive their license. These skills are degradable and must be practiced to ensure proficiency. As we all know, an engine failure requires immediate response using the controls during the autorotation descent. A pilot must be alert and maintain the proper airspeed, rate of descent, and rotor RPM while selecting the best place for touchdown. However, this is not always possible. If the engine fails below 500 feet, there is only a short period of time to react before the helicopter reaches the ground. A gentle touchdown depends upon the skill of the pilot and his or her understanding of the helicopter being flown. A good knowledge of the height velocity (HV) diagram of that helicopter will show the relationship of altitude, airspeed, and rate of descent that must be maintained in order to assure a successful autorotation. Another important factor in this event is that a suitable landing area is within the glide ratio of the auto-rotating helicopter.

Blade thruster parts. Photos courtesy of Spitfire Aerospace
Spitfire Aerospace is developing a system that will give a single engine helicopter two to four minutes of powered rotor RPM in order to reach an acceptable landing area in the event of an engine failure. This system would be activated upon entering autorotation.

The system is designed to give the pilot of a single-engine helicopter approximately three minutes of rotor RPM in the event of an engine failure. After an entry into normal autorotation, the pilot would, in accordance with instructions in the helicopters flight manual, activate the auxiliary rotor RPM system and proceed to make a normal powered landing. This system would be particularly useful at night or over densely populated area such as a city. It would give the helicopter the same safety factor as the recent trend in installing parachutes in airplanes. It would, in fact, be better because it would allow the pilot to choose a satisfactory landing area in a three or four mile radius.

high performance blade tip
This auxiliary power system works by pumping hydrogen peroxide from a small reservoir through a tube along the mast of the main rotor system, through another tube inside the rotor blade mixing the hydrogen peroxide with the catalyst near the blade tip. This causes a chemical reaction, which produces steam that is forced out the trailing edge of the rotor blade propelling the blade to turn. It is not explosive and is non-pollutant.

The reaction motors do not have a single moving part, while their weight at the blade tips provides good gyroscopic stability and excellent flywheel momentum in autorotation. Maintenance of the system is also simple. It can be adapted to any model helicopter by adjusting or calibrating the required thrust to maintain rotor RPM.

This invention is the work of a long time helicopter pilot, engineer, entrepreneur, and business owner Jack Fetsko. I had the opportunity to meet Jack and discuss his idea in great detail. He has an extensive aviation background dating back to 1945 when he started flying. He worked for Piasecki and Boeing and was the first pilot to establish helicopter traffic patrols and medevac programs in the Philadelphia area. He also designed, built and flew the first Enstrom Allison turbine helicopter. His invention is currently being evaluated on several types of helicopters.

It looks like Spitfire may be on to something. If this system can be outfitted on any single engine helicopter allowing pilots to have powered flight to a suitable landing area after an engine failure, this can be a force multiplier in helicopter safety. I’m sure there will be more testing involved and maybe some of the large OEMs will take notice and follow suit. Let’s hope this project continues and is proven to be effective thus having the potential to save many lives. As always, take action to fly safe!

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