Originally Posted by
weemonkey
Please excuse my ignorance but how do you trim a helicopter?
Reason I'm asking is on the fb video it went up into hover first, during the transition the tail dipped slightly only to be instantly corrected.
I didn't see any "tail dip". The ship picked up into a hover normally, then departed normally.
Perhaps what you are noticing is that, in the hover, the orientation of the helicopter is a bit tail low, nose high. This is totally normal for many helicopters. This way, with the required forward rotor disc tilt in cruise, the ship itself is just about level while in that flight regime. So as the ship is picked up, the cyclic must be moved forward as first the nose lifts off, and then the tail, so as to keep the rotor disc level and the pickup nice and vertical. As the pilot transitions into forward flight, the rotor disc, and the entire helicopter, tilts forward about the pitch axis and off it goes.
The same effects also happen about the roll axis. Depending on the direction of main rotor rotation, this aerodynamics involved will cause either the right or left skid or wheel to come up first, and the pilot must also move the cyclic laterally as the helicopter picks up into the hover, again to keep the main rotor disc level and the pickup vertical. And of course the wind also has it's own effects on this process.
In any case there is no trim involved. The way the controls are hydraulically boosted in most helicopters there are no control forces to speak of and any "trim" is merely the displacement of the pilot's hand by a couple of centimeters or so. Indeed, in the small R44 I fly, my trim position indicator is the location of my right hand where it rests on my leg
Very small helicopters without hydraulically boosted controls may have electric trim or no trim. The R22 has no trim except for the rather crude "cruise trim" bungee, which is either on or off. It can actually be rather fatiguing to fly after a while, especially if the rigging isn't exactly correct. The Cabri G2 has electric trim. Unfortunately in the G2 there is so much friction in the controls that it is hard to feel when trim has alleviated control pressures. The Enstroms, and the MD500 series, have electric trim, but I've never flown any of them. I'm sure there are other examples.