Helicopter flight

GreatLakesFlying

GreatLakesFlying

Pre-takeoff checklist
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Display name:
Leo
Today I went up in a helicopter for the first time. A friend who flies helicopters returned the favor after I took him on a couple of flights on the airplane with me. Here's the summary of my experience flying in a 'copter:
  • someone, woke up one day and thought, hmmm, let me design a flying machine with rotating wings that change their angle of attack thousands of times per minute. Wow!
  • The darn thing is slow. As we flew near a cemetery, I noticed a funeral procession on the ground marching faster than we were flying :D. (OK, headwind may have been a bit strong).
  • I couldn't help myself and I said it: "as god is my witness, I thought turkeys could fly" (it's the 40th anniversary of this statement, this year).
We flew a Schweizer 269C out of 06C. Here're a few photos I took from about 1500 MSL which was our cruising altitude.

IMG_9408.jpg Janura Forest Preserve, ~ 4 miles northwest of 06C.

IMG_9392.jpg The "ski jump", on Fox River, about 1 mile east of 3CK. This is a "cultural feature" shown on the Chicago TAC.

IMG_9392.jpg The Inverness Golf Club.
 

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GreatLakesFlying said:
let me design a flying machine with rotating wings that change their angle of attack thousands of times per minute.
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Not exactly. The pitch or (angle of attack) of the blades are changed by the raising and lowering of the collective. They don’t change their angle of attack thousands of times per minute unless the pilot has a very fast arm. ;)

Glad you had a good time. Some of my best memories are flying in rotor-wing.
 
Passed up a ride from the owner of the other flight school on the airport yesterday. Was going over some things with him as he’s also a DPE and I have a guy going for his check ride Saturday. He was giving a lesson and invited me along but I had another lesson myself.
 
Ryanb said:
Not exactly. The pitch or (angle of attack) of the blades are changed by the raising and lowering of the collective. They don’t change their angle of attack thousands of times per minute unless the pilot has a very fast arm. ;)

Glad you had a good time. Some of my best memories are flying in rotor-wing.
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Not exactly. The pitch or (angle of attack) of the blades are also changed by moving the cyclic. And they are constantly changing angle of attack as the swashplate rotates.

DDF282ED-5F42-4D0C-9AFF-49B96D68BFEF.jpeg
 
Salty said:
Not exactly. The pitch or (angle of attack) of the blades are also changed by moving the cyclic. And they are constantly changing angle of attack.
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Well if ya look at it that way.....
 
Salty said:
You wouldn’t be able to control a helicopter unless you look at it that way.
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Sorry, it’s getting late and I’m tired. I wasn’t thinking straight (like I ever do...:crazy:).
 
Unless your at a zero state no wind hover and omit any correction for translating tendency...or flat pitch on the ground each blade has a different angle of attack at any given time...sort of the way they work
 
Uggggghhhhhh... No.

Changing the pitch of the blades via either the collective or cyclic changes the angle of incidence. The angle of attack is the difference between the resultant relative wind and the chord line of the blade.
 
Minus a no wind, stationary hover, angle of incidence and AoA are both cyclically changing during flight. You have to have a change in AoA (cyclic feathering & blade flapping) or you’d have a dissymmetry of lift due to the difference in wind velocity between the advancing and retreating blades.
 
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You can see the pitch horn (lower right) moving up and down as the blade makes its revolutions. The blade flapping is further modifying AoA to try and combat dissymmetry of lift. In reality, you almost never have zero dissymmetry of lift in forward flight though.

 
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Guys got it all wrong. Basically if you take the stability matrix and f=kx we can solve for the eigen values. Basically what this means is that the flow manifold distributor on top of the blades is changing both angle of resistance as well as cyclic variation. Add in a little bit of p factor and torque effect and you got yourself a flow blown helicopter.

Hope that clears things up.
 
Velocity173 said:
You can see the pitch horn (lower right) moving up and down as the blade makes its revolutions. The blade flapping is further modifying AoA to try and combat dissymmetry of lift. In reality, you almost never have zero dissymmetry of lift in forward flight though.

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And then there is the lead/lag movement. Video doesn't really show that. Both of my older brothers are heli mechs. They are incredible and unforgiving machines.
 
jaybee said:
Changing the pitch of the blades via either the collective or cyclic changes the angle of incidence. The angle of attack is the difference between the resultant relative wind and the chord line of the blade.
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Bingo.

In general, AOI is hard angle between chord and rotorhead. AOA is soft angle relative to chord and airflow/airspeed. Collective/cyclic controls change AOI (blade pitch) along feathering axis which then induces an AOA collectively and cyclically. Throw in blade twist, retreating/advancing blade dynamics, lead/lag, underslung/overslung heads and you can have an AOA change without any AOI change. Ray Prouty 101.
 
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CC268 said:
Guys got it all wrong. Basically if you take the stability matrix and f=kx we can solve for the eigen values. Basically what this means is that the flow manifold distributor on top of the blades is changing both angle of resistance as well as cyclic variation. Add in a little bit of p factor and torque effect and you got yourself a flow blown helicopter.

Hope that clears things up.
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You are so incredibly wrong!

:D
 
Ryanb said:
You are so incredibly wrong!

:D
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He is, isn't he?

He is ignoring second-order effects and other non-linearities, and his approach assumes a uniform gravity field, no gravometric perturbations, and a cosmological constant at a value Λ<1, which we all know is impossible.
 
The only person who really knows how it works is Half Fast. I heard he single handedly designed the Saturn V rocket.
 
CC268 said:
Guys got it all wrong. Basically if you take the stability matrix and f=kx we can solve for the eigen values. Basically what this means is that the flow manifold distributor on top of the blades is changing both angle of resistance as well as cyclic variation. Add in a little bit of p factor and torque effect and you got yourself a flow blown helicopter.

Hope that clears things up.
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EACA6DAD-2347-4BE2-B13D-E25EE84C4B35.gif
 
b15065e58942ca4cad3f697fe8432c06.jpg
 
So tell us about two-rotor helicopters, e.g. Chinook. Great way to get around the advancing blade/retreating blade speed limitation?
 
Sac Arrow said:
So tell us about two-rotor helicopters, e.g. Chinook. Great way to get around the advancing blade/retreating blade speed limitation?
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They’re ugly so the air just wants to move out of its way. :D
 
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This big guy was out at the home field this week. I thought the pitot tubes on the hub was an interesting location.

987B725E-67D2-4B58-9F64-48BBA2CF92C3.jpeg
 
GreatLakesFlying said:
He is ignoring second-order effects and other non-linearities, and his approach assumes a uniform gravity field, no gravometric perturbations, and a cosmological constant at a value Λ<1, which we all know is impossible.
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:) :)
Helicopters run on 72% dark energy.
 
Sac Arrow said:
Comfy to ride in though!
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Yeah, a bit loud though.

Speaking of the speed issue, we were always told of the whole counter rotating blade theory of canceling out retreating blade stall as well. Never really bothered to investigate it so I really couldn’t tell ya. Flyarmy47 is a crew chief / flight engineer SI guy so I’m sure he could fill us in. I think it’s simple excess thrust vs total drag myself. As helos go, they are quick. One left me in the dust in Kosovo during a “cordon and search” mission.:(
 
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Sac Arrow said:
Great way to get around the advancing blade/retreating blade speed limitation?
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True. But right up with that is M/R flapping limits, cyclic forward limits, and engine power. However, in a perfect world conventional M/R designs are limited to around 250 mph. That is reason they go to compound helicopters or tilt rotors to exceed the 250 barrier.
 
Any of the CH-47 variants could leave any other helicopter in the dust...long time ago we would use Cobras to try and provide security for special mission nuke birds that carried a single 155mm 105 pound nuke joe to the Artillery Battery for a fire mission (Cold war Germany)...please slow down was all we could say...AH-64 although can haul more is no faster...particularly with armament. CH-47s have black magic working for them...
 
CC268 said:
Guys got it all wrong. Basically if you take the stability matrix and f=kx we can solve for the eigen values. Basically what this means is that the flow manifold distributor on top of the blades is changing both angle of resistance as well as cyclic variation. Add in a little bit of p factor and torque effect and you got yourself a flow blown helicopter.

Hope that clears things up.
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This from the guy with the controllability vs. maneuverability question. :rolleyes:
 
These things called helicopters are the devils doing, I tell ya whut...

 
My neighbor sprays crops with his helicopter... Took me for a ride one day and first question from him after I got my head set on was "what kind of ride do you want to take?"

Told him any damned thing but what I see him doing in the fields by the house. He complied, which was nice. Ag turns are fun to watch, from the ground.
 
my first helo ride, with girlfriend in 1984, he finds a tiny patch of ground surrounded by 80' trees and said something like Watch this, did an autorotation right there.
 
You can see the pitch horn (lower right) moving up and down as the blade makes its revolutions. The blade flapping is further modifying AoA to try and combat dissymmetry of lift. In reality, you almost never have zero dissymmetry of lift in forward flight though.

I bet the guy taking the movie got dizzy.:p
 
SkyDog58 said:
This from the guy with the controllability vs. maneuverability question. :rolleyes:
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I know...I’m just not as knowledable pilot as you high time guys...maybe someday tho
 
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