PPRuNe Forums - View Single Post - Question: Hover @ MCP and TOP
View Single Post
Old 20th December 2005 | 19:57
  #2 (permalink)  
NickLappos
 
Joined: Apr 2003
Posts: 3,012
Likes: 1
From: USA
CS-hover,
Generally performance is stated at Take Off power, at the weight/performance limit for HOGE. While this is not practical if one must make a vertical takeoff in still air, it is the convention.

In reality, it takes about 1.5% more power (or less weight) to make a purely VTO that when near the HOGE performance limit, and even with that 1.5%, the climb rate is only about 50 to 100 ft/min. However, even 5 knots of relative wind makes a tremendous difference, as does even a few feet of run, should the zone permit it (because the first 4 to 6 knots is so powerful, and it only takes a few helo-lengths to get that.) So for most helo operations, HOGE weight is OK, but the first takeoff is a squeeze.

In many training exercises and tests I have hung at TOP at max HOGE weight, and there is no climb except that made by fuel burn. In one powerplant cooling flight, I set the power, hung in perfectly still air with fixed collective and slowly drifted upward, ending at 1500 feet about 1 hour after the "take off".
NickLappos is offline