I've been watching the videos that surfaced after the crash with great interest, and my opinion poor decision making is the main factor of this accident, for reasons I will describe below.
The following is worth noting about the Reverse ½ Cuban 8 maneuver:
The Reverse ½ Cuban 8 maneuver is used as an end turn-around maneuver, and may be offset well to the left or right for this purpose.
** This is important, because the same is visible in the video referenced below.
To begin with, the airplane is seen in
this video to approach A27 from the North, doing a low level left hand turn, which it finished on an approximate South-Eastern heading, roughly above the Cuckoo's Corner (Coombes Rd).
At that point from what is visible in the video, he was flying roughly around 100 feet AGL, at which altitude, he began a Reverse ½ Cuban 8, which when he started he was flying roughly parallel to A27 as seen in
this video.
** This is important because starting that evolution parallel to the highway, also implies the possibility of it ending parallel to the highway (or directly above it), which it did.
Low level flying coupled with poor situational awareness amount to a poorly judged evolution with equivalent results, for reasons described below:
For what it's worth, I think any display pilots of highly maneuverable planes (such as Eurofighter, Rafale etc) would be reluctant if asked to start a Reverse ½ Cuban 8 at that altitude. Simply because it's a dangerous proposition, regardless of the airplane you are flying. Even if done right, it implies you would also finish the maneuver very close to ground level. Which is not a way to do things generally, let alone at an airshow, and much less in a vintage aircraft, equipped with a turbojet engine which even under perfectly functioning conditions, is likely to have a longer spool up time (like the L-39 does) and you will waste precious seconds close to ground level waiting for that power to be delivered to an otherwise not very energy-efficient air frame.
It is then wise, to allocate an altitude buffer for maneuvers such as Loops, Split S, or Reverse ½ Cuban 8.
Whether there was an unusual takeoff in a lower power setting than usual, or the usage of flaps influenced the elevator authority can be debated until the technical investigation is finalized. If the airplane didn't deliver enough power upon taking off, and the pilot was aware of the limitation, that means he had even less reasons to attempt that maneuver in the first place.
I believe if the pilot would have decided to go for a ½ Cuban 8, instead of Reverse ½ Cuban 8, the evolution would have ended at a relatively safe altitude and we wouldn't be having this conversation today.