Where is 'thrust' pointing?
Thread Starter
Joined: Apr 2003
Posts: 1,635
Likes: 1
From: Vancouver, BC, Canada
Where is 'thrust' pointing?
'Thrust' is considered by some as the rotor's force that is perpendicular to the tip path plane. Others considered 'thrust' as the horizontal component of the rotor's force.
Both definitions are probably valid for an airplane's propeller. Which is the correct one for a helicopter's rotor and what is the correct name of the other vector?
Both definitions are probably valid for an airplane's propeller. Which is the correct one for a helicopter's rotor and what is the correct name of the other vector?
PPRuNe Enigma
Joined: Feb 2001
Posts: 427
Likes: 0
From: Scotland
How about "Total Rotor Thrust" for the force perpendicular to the disk ?
This can then be resolved into vertical and horizontal components.
In fact, there are two possible horizontal components - a longitudinal one for forward/back motion, and a lateral one if the helicopter is banked or traversing sideways.
This can then be resolved into vertical and horizontal components.
In fact, there are two possible horizontal components - a longitudinal one for forward/back motion, and a lateral one if the helicopter is banked or traversing sideways.
Joined: Jan 2001
Posts: 420
Likes: 0
From: AB, Canada
As much as it seems like it would be convenient, there is not a universal standard for terminology, sign conventions, and variables with regard to helicopter aerodynamics. Check out Stepniewski & Keys book carefully and you'll see they aren't even consistent between their volumes.
I think of thrust as perpendicular to the tip path plane.
Whichever you use, make sure it's clear to your readers.
Matthew.
I think of thrust as perpendicular to the tip path plane.
Whichever you use, make sure it's clear to your readers.
Matthew.
Thread Starter
Joined: Apr 2003
Posts: 1,635
Likes: 1
From: Vancouver, BC, Canada
Grainger & heedm
Thanks for the input.
Perhaps Stepniewski was ambidextrous. Perhaps when writing the two books, the left hand didn't know what the right hand was doing.
Bad joke.
If 'thrust' is used for the vector perpendicular to the tip path plane and 'lift' is the vertical component, would 'push' or 'pull' be an appropriate word for the horizontal component(s)?
Thanks for the input.
Perhaps Stepniewski was ambidextrous. Perhaps when writing the two books, the left hand didn't know what the right hand was doing.
Bad joke.If 'thrust' is used for the vector perpendicular to the tip path plane and 'lift' is the vertical component, would 'push' or 'pull' be an appropriate word for the horizontal component(s)?
Joined: Apr 2003
Posts: 3,012
Likes: 1
From: USA
Dave,
In general terms, the thrust that is prouced by the main rotor is the vector sum of all the forces that the rotor produces. This thrust is very roughly perpendicular to the tip path plane. If the truth be known, the thrust is a very choppy wave form, with lots of 1 per rev and N per rev content, as well as oscillating in-plane "H" forces.
For accounting the forces on a flying machine, we divide all forces into four vectors, Lift and Weight, Thrust and Drag. In this parlance, the thrust is the sum of all propulsive forces on the aircraft. For a helicopter, this is the longitudinal component of the rotor thrust, and the net propulsive force from the engine exhaust.
There is no standard term for anything on our planet, why should thrust be any different?
In general terms, the thrust that is prouced by the main rotor is the vector sum of all the forces that the rotor produces. This thrust is very roughly perpendicular to the tip path plane. If the truth be known, the thrust is a very choppy wave form, with lots of 1 per rev and N per rev content, as well as oscillating in-plane "H" forces.
For accounting the forces on a flying machine, we divide all forces into four vectors, Lift and Weight, Thrust and Drag. In this parlance, the thrust is the sum of all propulsive forces on the aircraft. For a helicopter, this is the longitudinal component of the rotor thrust, and the net propulsive force from the engine exhaust.
There is no standard term for anything on our planet, why should thrust be any different?
