MstrCmdr Posted March 2, 2022 Posted March 2, 2022 This one goes out to all you real rotorheads. Im a spinny-boi noob. Is DCS modelling gyro precession correctly? The Huey does not appear to follow the physical law where forward cyclic means the disc actually tilts to the right thereby imparting its effects 90 degrees later = downward pitch. Ive been watching a ton of apache videos but cannot see the disc movement clear enough except in one where the rotors tilt right and the helo pitches up. It was a gung ho training vid where the helo pulls up and then tilts down to loose some rockets. In the AH64 ultimate weapon intro vid the aircraft pitches its rotor disc in the same direction of movement instead of being 90 degrees delayed. Example:rotor disc pitches down to the right and helo dips right. Shouldnt the rotor disc tilt back and the helo tilt right? Or maybe the rotor behavior is 90 degrees later than the swashplate. So the swash tilts right but the rotors dip forward and so does the helo. Am i misunderstanding this? Cmon kgillers and raptor, set me straight here.
Solution kgillers3 Posted March 2, 2022 Solution Posted March 2, 2022 (edited) The tilt is correct for the the uh. The controls are rigged. Now I haven’t specifically checked, but, if you were looking for evidence of it then with the blades stopped, If they are at the 9-3 clock positions. Forward and aft on the cyclic you should see the blades feather or rotate. And if you move it in the roll axis there should be no feather. If the blades are at the 12-6 clock positions, the opposite for pitch and roll. the disk tilts because lift is being applied in the correct area. Gyroscopic precession says it’ll happen 90 degrees ahead of where you ask for it or to that affect. No weird tilt. If you ask for lift 90 degrees behind, the result is blade tilting in the way you wanna go, so if the controls aren’t rigged then for and aft in the cyclic will give you left and right which would give your funky blade movement and probably a crash. Edited March 2, 2022 by kgillers3
kgillers3 Posted March 2, 2022 Posted March 2, 2022 Watch them demonstrate it on YouTube with a wheel, the wheel will tilt 90 degrees ahead of where he pushed it.
MstrCmdr Posted March 2, 2022 Author Posted March 2, 2022 7 minutes ago, kgillers3 said: The tilt is correct. The controls are rigged. Now I haven’t specifically checked, but, if you were looking for evidence of it then with the blades stopped, If they are at the 9-3 clock positions. Forward and aft on the cyclic you should see the blades feather or rotate. And if you move it in the roll axis there should be no feather. If the blades are at the 12-6 clock positions, the opposite for pitch and roll. the disk tilts because lift is being applied in the correct area. Gyroscopic precession says it’ll happen 90 degrees ahead of where you ask for it or to that affect. No weird tilt. Do you ask for lift 90 degrees behind, the result is blade tilting in the way you wanna go Ok so the rotor plane of a real helicopter tilts in the direction of movement, excluding tail rotor, torque, and wind effects." Cylic right, rotor plane tilts right, BUT the swashplate tilts up decreasing blade bitch at the 180 so blades are feathered for less lift in the rear but that effect is made 90 degrees later resulting in the rightside dip in rotor plane? Got it. Im gonna pack up and go back to the A10C. Bye guys. [Packs stuff and leaves]
RedskinMike Posted March 2, 2022 Posted March 2, 2022 Pilots dont have to account for the 90 degree lag. what happens is that the pitch horn 45 degrees together with the mixing unit also angled 45 degrees in the apache. So the 90 degrees is taking into account within the controls so if he steers left the blade wil start increasing or decreasing pitch at the 12 o clock pos. And have full effect 90 degrees later at the 9 o clock pos.
MstrCmdr Posted March 2, 2022 Author Posted March 2, 2022 3 minutes ago, RedskinMike said: Pilots dont have to account for the 90 degree lag. what happens is that the pitch horn 45 degrees together with the mixing unit also angled 45 degrees in the apache. So the 90 degrees is taking into account within the controls so if he steers left the blade wil start increasing or decreasing pitch at the 12 o clock pos. And have full effect 90 degrees later at the 9 o clock pos. I have no idea what that middle portion is saying... dumb it down for me please. Im genuinely curious what this mixing unit is. I completely understand the pilots not having to account for the 90 degree lag. I have a completely newfound respect for helo pilots. I really dont think there are any questions abt elevators or ailerons. But if you told me to inspect a helo id poke it with a stick and say oogly boogly.
MstrCmdr Posted March 2, 2022 Author Posted March 2, 2022 Found this video that shows forward cyclic on a clockwise spinning helo. The swash tilts left which would equate to a right tilt in the Apache since it is anticlockwise. I'm learning so much. I mean what's next? Are we gonna learn the Earth is actually round? 1
kgillers3 Posted March 2, 2022 Posted March 2, 2022 43 minutes ago, MstrCmdr said: I have no idea what that middle portion is saying... dumb it down for me please. Im genuinely curious what this mixing unit is. I completely understand the pilots not having to account for the 90 degree lag. I have a completely newfound respect for helo pilots. I really dont think there are any questions abt elevators or ailerons. But if you told me to inspect a helo id poke it with a stick and say oogly boogly. All he’s saying is it’s rigged so when we wanna go forward it’s cyclic forward and etc. they accomplish this differently on different helicopters. Point is blade feathers 90 degrees behind where you’re asking for lift. So I push forward on cyclic. Blades feather at the 9 o’clock position for ccw rotor, and when it gets to the 6 o’clock position lift is applied causing the blade to lift (tilt) forward. it could be a combination so one side increases lift and one side decreases lift for your directional control. tail rotor collectively changes pitch for all the blades so there is no gyroscopic precession. Just like moving the collective on the main mast doesn’t affect gyroscopic precession because lift is applied equally throughout the disk. this is a neat to know thing I’d say, I was taught it, it’s a thing that happens and it’s compensated for.
Recommended Posts