inflight prerotation

[pbool]

b Three years ago this month I had a keeerash with my pitbull. This was due to an inflight engagement of the prerotator while in flight. Someone asked me how it happened the other day so I wrote up a detailed explanation and posted it in the flying photos forum under illinois aerials, page 2. It was a pretty bizarre happening but if it happened to me, it could happen to someone else. It is too long to rewrite twice so I will leave it where it is. John M

[gyromike]

Here's a link to the post:

http://www.rotaryforum.com/forum/showpost.php?p=62182&postcount=26

[Doug Riley]

The safest prerotator setup is one that has multiple disconnect points in series. For example, the Wunderlich has the following (in order from the ring gear down) : (1) Bendix floating drive gear (2) override ratchet within the Bendix and (3) the retractable drive wheel. Any one of these will prevent the prerotator from slowing the rotor in flight, even if the other two lock up.

The RFD (Dominator) system retains the Bendix's floating gear, but eliminates the override ratchet. Down at the engine, the rubber drive wheel is replaced by a micro-vee belt that is slack during flight. Thus, this unit has TWO disconnects in series. Somewhat less idiot-proof than the Wunderlich, but still a measure of fail-safety.

I'm not very familiar with start-motor prerotators, but you guys who use them ought to review your designs for fail-safety. An in-flight engagement when the unit isn't designed for it is a really, really scary possibility. In an extreme case, it could jam and STOP the rotor or shred the mast/rotor head.

[bartc150]

Seems like you guys with the electric pre rotators should cover all electrical connections, i.e. starters, solenoids, switches, with some sort of protectant such as liquid electrical tape to keep that mystery part from arcing on them and engaging the starter.