Originally Posted by
JohnDixson
Sans, it wasn’t low gain on the 59 ( in the sense of control sensitivity ), but rather low blade range, i.e., total moment capability longitudinally. The hell of that issue was that they’d been up against the forward stop previously.
Ah I see. Thanks for the correction John, I got the "low gain" quote from the Sikorsky Archives article.
First flight occurred in June, 1973. One month later the first XH-59A aircraft experienced a low speed accident on the flight field. The design team had never dealt with a rotor system as stiff as this before. There was much concern about the extremely high control power that the rotor could develop. As a result, the control system was designed with a very low gain to prevent the controls from being too sensitive. This seemed to work out fine in the initial hover tests. However, when the pilots moved out of hover to transition to forward flight, the aircraft tended to nose up. The pilot inputted more and more forward cyclic to counter this, until the stick was on the forward stop and the aircraft was still nosing up. The pilot reduced the collective to get it back on the ground. The tail contacted the ground first and the aircraft rolled over until the blades struck the ground. The rotor system was destroyed. Both pilots were uninjured.
This set the program back for over a year while the cause of the accident was determined. The conclusion was that the control system gains were too low to cover all flight modes. Aircraft #1 was rebuilt for wind tunnel testing, but was not returned to flight status