Sparky Imeson devotes considerable content in Mountain Flying Bible to the subject of turning around in narrow canyons. I don’t plan to paraphrase the content but would recommend strongly anybody interested in flying in the mountains to buy his book.
He warns against chandelles, wingovers, or hammerhead stalls because there is a human tendency when encountering rising terrain to shorten your flying arm and start to slow down. There is also density altitude, downdrafts, etc to contend with.
Basically he recommends establishing a point of no return, and describes how to establish this.
He also recommends training to ensure your technique is a conditioned response. He discusses what side of a canyon to fly (downdraft or updraft side?); the basic maths of turn radii vs speed vs configuration vs angle of bank vs g-load, and what is the ideal technique for the turn.
I think the main value of his advice is in the behavioural and physiological factors associated with flying in the mountains. Unlike the FAA CPL a chandelle or wingover (which is technically an aerobatic manoeuvre) in the mountains has very different visual cues to the nice PowerPoints showing the manoeuvres over the flat plains of Kansas or Iowa with visibility at infinity. In these conditions you have a clear horizon, there is no startle effect, you have carried out a HASELL check with plenty of altitude, you are not even in an aerobatic competition box so no need to consider wind (the FAA ground proximity manoeuvres do require consideration for wind), and you are starting from an appropriate entry speed.
In a box canyon you have allowed yourself to ‘box yourself in’, the aircraft is at a high density altitude, one side is in deep shade, one side is in haze and glare, one side has downdrafts, one side updrafts, turbulence, there is NO DISCERNIBLE HORIZON, you are surrounded by rocks – Imeson’s point being that you don’t want to have an instinctual response, but you should have a knowledgeable, planned response in a manoeuvre you have trained for and are current in.
I do think the FAA CPL is superior to the EASA version by virtue of the ground reference and co ordination manoeuvres, but I wouldn’t recommend a chandelle or wingover as the desired conditioned response if you are caught out in a narrow canyon.
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At the other end, B2B, transactions can involve all kinds of “unfair” contracts, so long as something is delivered and the agreed payment is made, and it is clear both parties willingly entered into the contract, etc…
However, GA transactions seem to fall into a grey area in between, due to various reasons e.g.