PPRuNe Forums - View Single Post - Entering autos: discussion split from Glasgow crash thread
Old 17th Dec 2013, 17:47
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HeliComparator
 
Join Date: Aug 2004
Location: Aberdeen
Age: 67
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Just a thought... Regarding emergency auto entry from cruising flight, we seem to be stuck somewhere between dumping collective then thinking about the cyclic afterwards, dumping the collective and maintaining the attitude, simultaneously dumping the collective and moving the cyclic back, and leading with the aft cyclic prior to moving the collective. One of the problems with "maintaining the attitude" is that, with a large and rapid movement of the collective comes a significant attitude upset (more so in some types than others) and to apply the correct amount of cyclic to maintain the attitude is not that easy especially bearing in mind the rapidity of the effect of dumping the collective vs the relatively slow response in pitch attitude to cyclic being fought by a SAS, muddied by probable yaw and its own effect on pitch attitude.

Therefore my suggestion is that the pitch attitude is not the thing to go for. It is hard to judge accurately under dynamic conditions (think IMC), you have to be looking in the right place when really you want to be looking at the Nr gauge, and ultimately it is not an important parameter. What is important is the restoration of Nr and there is one primary parameter that affects this (other than collective pitch) and that is g loading.

G loading is also very easy to assess - the body is pretty good at it. So what we need to do is to aim for at least 1 g, maybe a little more, in the first moments after a double engine failure is recognised.

Therefore my recommendation in the event of a need for emergency auto entry, is to lower the collective whilst moving the cyclic back to maintain at least 1g. If 1g or more is maintained, there will be little or no height lost in the first moments which satisfies those flying fast near the ground. Since the responsiveness of the cyclic depends on current g, leading with the collective will instantly reduce g and make it harder to regain it with cyclic. Therefore it is necessary to lead with cyclic, so as to maintain 1g or more throughout the early stages of entry.

I'm sure this is what we actually do, but I'm not sure anyone has vocalised it yet?

To reiterate, all this from cruising flight. As you can tell, I remain in full agreement with PG!
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