To: the chopper
At the time I was working aboard the icebreaker in Greenland our two sister ships both US Navy were operating Bell HTL-5s. The HTL-5 had spring loaded teeter stops that kept the blades in the neutral teeter position until sufficient rotor speed was built up and the stops would disengage allowing the pilot to operate his cyclic. Our HTL-1s did not have this provision. Shortly before our deployment Bell issued a mod order requiring that the springs be removed from the centrifugal clutch. With the springs removed the clutch would immediately engage when the engine started to turn and in a fraction of a second the clutch would be fully engaged and the rotor would be turning over at engine speed minus the gear reduction.
That meant that our pilots and me the mechanic had no experience aboard ship with the helicopter in this modified configuration. The first few times we started we were not breaking ice and the ships’ flight deck was very stable. We did encounter the bouncing due to the turning frequency of the ships’ screws but there was no rocking. With a minimal wind speed the rotor would maintain somewhat of a median position which did not cause any problems during run up.
However when we started breaking ice and the ship was rolling left and right and pitching and heaving at the same time the helicopter would really bounce on the floats and it would also roll quite a bit on the floats. At this same time the blades would be moving all over the place. When the engine was started the blade would immediately start rotating at a high rate of speed. If the blades were teetered too far the physical action would be to move them to their neutral teeter position and this could result in a physical force that would cause the helicopter to roll over. It only took one time for us to realize that the blades had to be maintained in the neutral teeter position during start up. The Navy did not experience this phenomenon due to the spring loaded teeter stops.
To show how fast the blades rotated at start up if you did not pull your hand back after having the blade snatched from between your fingers the second blade hit your hand. Once again, it only took one time to learn the lesson. Or as they say, it doesn’t take me long to learn how to check out a hot horseshoe.
To answer your question about how many Bell 47s on floats rolled over during start up the answer is none but only because we learned from the experience. It was close but it didn't roll over although it could have.
[ 26 August 2001: Message edited by: Lu Zuckerman ]
[ 26 August 2001: Message edited by: Lu Zuckerman ]