FH-1100 (OH-5) FIRST FLIGHT by Jack Schweibold.
Hiller Air Museum located in San Mateo, California, announced it will again host the Vertical Challenge Helicopter Air Show June 16th, 10am to 4pm. (1) This comprehensive showcase of rotorcraft brings
back memories of my first flights in the predecessor of the Fairchild Hiller FH-1100, the YOH-5 some 50 years ago. I had just completed fifty hours of required flight on the new Allison YT63 Turbine Engine, now the Rolls-Royce/Allison 250. Prototype engines were then released to Hiller, Bell and Hughes for their respective helicopters designed and built for the Army’s Light Observation Helicopter Competition. Our engine test aircraft at Allison was a Bell 47-J dressed in Navy colors. The Navy used this model as an anti-submarine Torpedo Helicopter.
Hiller’s maiden flight in the YOH-5 (FH-1100) was January, 21st 1963 with Bell and Hughes launching their models in the same period. Competition among the manufacturers was brutal and the secrecy requirements were ferocious. I was the Allison test pilot commissioned by the Army to be the first to fly and evaluate the three aircraft. Confidentiality was especially tight for those of us working with the engine as it powered all three contenders. Sworn to secrecy by signing “Thou Shall Not Tell” documents, I was dispatched from Indianapolis to the various manufacturers. I was amazed at the quality of design, performance and workmanship in the Hiller machine. While I couldn’t offer comparative remarks during the two week trip, it looked like the winner. Effectively, it highlighted state-of-the art construction. I valued the attention given to its serviceability. Battlefield maintenance of engine and related components could be easily addressed by merely sliding a clamshell cowling rearward on horizontal tracks along the tail boom.
My initial test flights confirmed earlier OEM engineering assessments that the engine needed quicker responsiveness when recovering from an aborted autorotation touchdown. Otherwise, the little engine pumping out an awesome 318hp, at half the weight of a reciprocating engine, performed extraordinarily well. After some modification to the fuel control, the Allison 250 with reduced acceleration time made an excellent performance pairing in all these light helicopters with the added benefit of modular construction that facilitated a new era for field serviceability.
The YOH-5 did not win or maybe even ever had a chance to compete. In a competition that featured the initial winner, Hughes – as in Howard, being brought before a congressional investigation for tampering with the selection process that eventually resulted in the bulk of the production contract going to Bell. Hiller had elected to drop from the military contest and instead built over 250 civil FH-1100’s. Much like the venerable DC-3, this helicopter remains in certified service almost fifty years later. Currently serviced by FH-1100 Manufacturing Corporation (2), recent reports (3) indicate its manufacture may continue into the future through agreements with China … it’s hard to keep a good old girl down!
Next article … a flight in a competitor, the Bell YOH-4, the Heavy Weight!
(1) http://www.hiller.org/vertical-challenge.shtml
(2) http://www.fh1100.com/
(3) http://english.peopledaily.com.cn/90778/7763510.html