Memories
Thanks Lonewolf, but in my case the toast would be just soda, as in 1989, with the aid of a very good friend, I realized that the good people at Bombay were distilling that product faster than I could dispose of it. It can be historically verified that a month after this epiphany, the popular bar across the street from Sikorsky closed its doors.
Bus Driver, the beanie in the picture is simply a fairing to cover the upper connections for all the rotor instrumentation. I know what you were surmising: that it was a part of the " Tail shake " solution, but that was attained ( on this model anyway ) thru a totally different aft " doghouse " fairing behind the main rotor.
Matari, I will limit my response to your note to the raised rotor, as the story in the book is not complete. First, some history. The original low rotor was due to the air transportability requirements in a C-130. Pilot's office and the safety organization saw a distinct possibility for toe issues: contact of the main rotor into either cockpit roof.engine cowl tops/tail cone, or infantry as they did their thing. Based on the head geometry and the accident history of the USAF S-61 and the USMC S-65, I wrote a longish memo on the subject, which, as you can see in the picture, did not carry the day. What you cannot see in the picture is that there were four electronic blade tracker sensors, one each over the cockpit, both engine cowls and the tail cone. They fed both the onboard instrumentation, and a vertical clearance multi-arrow indicator ( with a memory function button ) mounted on the cockpit glare shield, centered. The first hover flight went absolutely perfectly, but the subsequent two in yard ( Stratford runway is 1500 ft, so forward/sideward/rearward flight speeds are limited ) disclosed that, in simply flaring back to a hover from a takeoff run produced blade clearance over the cockpit of 5 inches ( remember, this is not a rigid rotor ). Remember too, that an Army requirement to flight test to -0.5 G had to be met.
The next envelope expansion flight unearthed no shortage of serious issues, and just one that had a serious spec compliance issue was insufficient forward flight performance, 20+ knots at the top end. While the usual drag reduction schemes were initiated, the senior aerodynamicist assigned produced a theory that was backed up bu massive computer driven airflow diagrams which were posted on the walls of the UTTAS HQ type room. They showed that the airflow up and over the broad, flat cockpit enclosure was increasing the angle of attack of a major section of the rotor disc, and in fact stalling it! By now it is 1975 and we have but 5 months to the Army Preliminary Evaluation. We had a new development chief and April 2nd or 3rd he held a meeting and decided to raise the main rotor 15 inches. May 3rd we flew a raised rotor shaft.The Chief Test Pilot Dick Wright and I made the flight and took the machine out to maximum level flight speed as defined by the 100% Q limit ( design gross weight ). The new development chief met us on the way to the debrief and asked how much faster we had gone. Dick made a circle with his thumb and first finger, and said " that much faster, Bob ". But the news wasn't all bad, as the 3P and 5P excitation was down significantly. At that time, resolving the vibration situation had been going on since October without major success, so this improvement was exceedingly important.
Fits the definition of a serendipitous event. We raised the main rotor in a month ( BTW, it met the C-130 requirement, too! ) in order to get back a major shortfall in airspeed. Absolutely failing at that, we nonetheless totally eliminated the blade clearance issue and markedly improved the vibration signature situation.
I've omitted more than a few details for brevity, but that is the raised rotor story, less the fantastic effort by the rotor/drive train design and test engineering team that allowed a safe test flight one month after decision.
IFMU. I don't type fast enough to cover the story of the stabilator, but like the main rotor that decision was made at a February 11 meeting, and 30 days later, we flew that FBW tail, with the head of that design branch ( a very close relation of yours? )in the jump seat running the electronics.
Last edited by JohnDixson; 23rd Oct 2014 at 02:07.