Originally Posted by
Bell_ringer
Any number of things could have happened to an engine with so many moving parts. They could have even lost a mag.
Yeah, it's really hard to tell. The Low RPM horn starts first (indicating 97% RRPM vs power on 102%), and then you hear a smooth decrease in the engine noise. I've had both bottom end and top end failures in Lycomings, and they're not this smooth. They involve some banging and violent yawing, none of which was obvious in the video. Likewise mags - a simple mag failure wouldn't cause this, and a jumped mag gear would again involve rough running which we don't hear. And if the comment on the video was correct, this was a Raven 2, so no carb ice (it's fuel injected). I could also buy fuel exhaustion (probably not boost pump failure - the R44 has both an electrical and mechanical pump, either one of which is sufficient to run the engine).
A governor failure is a possibility (and it's one of the least reliable parts of a Robinson), as is the pilot simply rolling the throttle off by mistake (i.e. if he got the horn and responded by trying to roll on throttle but rolled it off by mistake... wouldn't be the first time a pilot rolled the throttle the wrong way.
Without hearing from the pilot I hate to toss some criticism his way, but here goes:
1) he was way too low given the congested area below him. He clearly wasn't high enough to allow for a safe landing following an engine failure.
2) he didn't build much RPM. You can hear the horn chirp several times during the glide. That means he kept pulling up on the collective with the RPM below 97%, and then putting it back down when the horn would chirp. So, he probably went into the flare with less than 97%. I do hear the RPM build just before the impact, but it was still building when they hit - which leads to #3
3) He flared too low. I can tell not only by the view out the window (although it's obscured at just the wrong moment) and by the sound (I do a LOT of R44 touchdowns). The RPM was still building when they hit, indicating to me that the flare didn't have time to reach full thrust. This is common in R22 pilots that transition to the R44... they tend to start the flare 15-20 feet too low because they're used to the R22 inertia. An R44 will do a 30 foot hovering auto at max gross if you wind the RPM up to the upper red line (108%), but that requires you to start at 40-50 feet with plenty of deck angle... R22 (and many pilots used to low inertia rotor systems) tend to not flare aggressively enough. A gentle flare won't build enough RPM, nor will it decrease the ground speed to near zero.
But of course #1 was the biggest problem. Ask anyone who's flown with me: I'm always telling people to fly higher. This accident is a really unfortunate example of why.