PPRuNe Forums - View Single Post - Condition for Vortex Ring
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Old 28th Nov 2017, 18:33
  #107 (permalink)  
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FH1100 - the problem is that what you call pilot stupidity causes lots of accidents and incidents.

When it comes to OGE hover performance, the military solution is to ensure an adequate thrust margin ie that you have more power available than is needed for hover OGE - that way you are unlikely to be embarrassed if you encounter slightly unfavourable conditions or don't fly so brilliantly.

To my knowledge, RFMs for civil aircraft don't include a percentage thrust margin graph, only an OGE hover graph for calculating MAUM for given pressure and temp conditions.

So, no problem as long as your maths and use of the graph are spot on - except that those graphs are for completely still conditions in a stable hover and don't take into account any turbulence or the fact that you need more power to get to the hover than you do to maintain it.

No wonder then that when extracting max performance from your aircraft (for whatever reason) you can get caught out and end up in a gentle descent with the lever up and the Nr slowly decaying (you are overpitching) - the solution is a gentle accel to gain speed.

Compare reacting correctly to this situation (because you know it is SWP and not VRS) to what would happen if you only thought SWP and VRS were the same and therefore had the same recovery ie dump the lever and try to get forward speed.

You can continue to pretend the FAA see-all and know-all but if they truly recognise the difference between running out of power and being in vortex ring, they should say it loud and clear to remove any confusion.
crab@SAAvn.co.uk is offline