Originally Posted by
RatherBeFlying
Analysis of my recorder data produced this chart of wind velocities. The y-axis wind component could not be determined from the available data.
From the chart we can infer a vortex followed by a downburst.
I was very lucky.
The terrain the aircraft was flying over and the wind do not glaringly suggest a rotor entry. If the aircraft was on the less side of a ridge that had a fairly defined ridge line, and a strong wing was present, particularly if the wind flow is oblique to the terrain, then a rotor could be an interesting option, but, then the attitude of an aircraft entering a rotor with an open loop control is quite predictable. The images show enough resolution to not suggest that the aircraft entered into a rotor. Always a consideration, was an item that came up with UAL 585...
The trees in some of the photos suggest that the camera is not level with the horizon, so the actual bank angle is open to more analysis by the investigators, but it was steep, looks close to 90 but is probably at least 70.... and that adds a pretty high AOA requirement for level flight and more for a pull out. The roll into the run has a high bank angle, but a descending flight path initially, so AOA is modest, then the bank is increased and a pull out is conducted, and AOA is going to spike, about the time that the aircraft does a rapid right roll, and the nose slices downwards, which is characteristic of an incipient spin entry.
I would remain concerned with the loss of awareness of the horizon by the crew in the path that they flew, they may have had little awareness of how close to a bad day their banked pullout was going to take them. The problem with experience is that it increases our confidence that we are on top of the risks that exist, and so the SOPS such as bank limits, crew crosschecking etc are not necessary, (didn't hurt us before, etc) Nothing in LL ops around fires is trivial, fixed or rotary. The guys doing it are darned good, and it is still dangerous, basics still apply every time.