From: nlappos@snet.net (nlappos@snet.net)
Subject: Wrong - Left turns make you climb!
Newsgroups: rec.aviation.rotorcraft
Date: 2001-01-19 21:18:37 PST

Contrary to the posts that assert otherwise, a steady left pedal turn in a US turbine powered helicopter will almost always make the machine slowly climb. This is certainly counter intuitive, and was first demonstrated to me by the Dean of Sikorsky test pilots, Byron Graham, back in 1974. After a slight initial descent, the climb begins, and doesn't stop unless you stop turning.

The tail rotor torque is not measurably increased (once the steady yaw rate is achieved) since the thrust needed to keep a slow hover turn (say 10 to 20 degrees per second) is virtually the same as a steady hover. The climb is caused by a rather subtle factor - the fact that the turning fuselage adds rpm to the rotor! For a rotor spinning at 300 rpm, the rotor is turning at 1800 degrees of rotation per second. 20 degrees per second more due to fuselage rotation is a 1.1% increase in tip speed, which makes a 2.2% increase in total lift. A slow climb of 100 feet per minute results.

A right turn causes the opposite effect, of course.

I know this is counter to all the other posts, but I encourage you to simply try it - freeze the collective, stay steady on the cyclic, and just slowly creep in some pedal to make the turn at 10 to 20 degrees per second (a five count for each 90 degrees of turn will help you keep the pace).

Nick Lappos