Originally Posted by
SASless
As I view Page 5 of the latest AAIB Report....the aircraft seemed to pitch down sharply 2-3 seconds after the Collective Pitch was increased 8.5 seconds before impact with the Sea. You reckon that might have had something to do with the ROD increase?
I think the report mentions the pilot lowering the nose, and the cyclic position moving forward supports that. Any helicopter has flapback and as the speed gets very low, you have to move the cyclic back or it will pitch down. On the Super Puma family, there comes a point at about 25-30kts when the horizontal stabilizer stalls, this causes a pitch down which is mostly masked by the autopilot, although less so if the trim release is depressed and/or the pilot is flying against the spring trim. So I think a combination of all 3 effects caused the nose down pitch. However I don't think this had much impact on the RoD - helicopters tend to go where you point them (nose up, nose down etc) when in significant forward flight. With very low airspeed, say in the hover, selecting 5 degrees nose down doesn't make that much different to vertical speed.
With the "flare effect" rapidly disappearing as the speed fell right off, I don't think the pitch attitude change made that much difference and was clearly the right thing to do to avoid the helicopter going backwards, if far too late.
More significant is that it took 8 seconds between the copilot low airspeed call and getting the lever right up. That's a very long time in the heat of the moment and makes me wonder if there wasn't some issue with incapacitation, or disorientation at the very least.