AAIB accident report now published. Any R22 pilots able to comment?
Two possibilities perhaps...
Looking at the GPS data the groundspeed appeared to slow with a gain in height and a turn to the left just before the incident. Perhaps there was an element of head inside looking at a chart in the left hand, having not been where he thought he was before passing Cambridge he was working out a new route having been denied the Camb transit. Then either;
a) lookup up and spotting the climb and noticing he was in the MATZ attempted to lose height and/or gain speed with a large forward cyclic movement, heading into Low-G territory.
b) still consulting map, there was carb ice, the governor masked it until the low RRPM horn went off with the resultant rotor stall.
The pilot had come from the fixed wing world, where you can trim an aircraft to fly level and 'easily' consult charts and the like, you simply can't do that in an R22 the workload is higher just to fly straight and level, and you are effectively one handed as you must hold the cyclic all the time. Workload could have been increasing with the incorrect position and the cambridge transit denied causing a lapse to fixed wing response to the final trigger event? It's hard to see how he would have intentionally gone into the MATZ given his previous experience.
I fly the R22 / R44 and also act as ballast and/or navigator in fixed wing with friends so do see the difference in workload just to fly along straight and level once up and trimmed.