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Old 15th Aug 2008, 16:44
  #28 (permalink)  
Bravo73
 
Join Date: Jul 2002
Location: UK
Posts: 2,952
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Originally Posted by Nipper2
Now to get back on topic, can someone please tell this humble fixed wing pilot why when these Z9/365s take-off they pull slowly into a not-so-low hover (perhaps 100 feet), hang for a while and then ever so slowly push over into forward flight? They have a superb operating location with a long enough slab of concrete for me to fly my Tipsy Nipper from so it's definitely not a site limitation.
From your description, Nipper2, that sounds like a fairly standard 'Group A, Helipad' departure. The idea is that if you have an engine failure before TDP (Take-Off Decision Point ie 100 feet) then you can reject back onto the helipad. If you have an engine failure immediately after TDP, you should have sufficient height to fly away on the remaining engine. (Think of TDP as roughly equivalent to V1.) This procedure obviously only applies to twin engined helicopters.


Originally Posted by Nipper2
I was always led to believe you wanted to be low and slow for the minimum possible amount of time when flying one of these loosely connected sets of rotating parts. Have the Chinese also found a way to change the laws of aerodynamics?
The 'avoid low and slow' (ie what 'we' refer to as the Height/Velocity Curve) particularly applies to single engined helicopters. Although twins also have to be aware of height/speed issues, the idea is that in the event of an engine failure, you should be able to fly away on the remaining engine. (There are, of course, some H/V combinations where particular twins might not be able to fly away though.)


HTH
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