Gyro theory

[t-bird]

A concept that I always struggle to understand is what makes a gyro pitch up to climb and pitch down for decent.

This is how I have it feel free to correct me.

For the climbing

By moving your stick back you would increase the pitch of the advancing rotor 90 degrees with the fuselage increasing lift, and also degreases the lift on the retreating blade 90 degrees with fuselage by degreasing the pitch.

But this is 90 degrees with the fuselage, why don’t the Gyro roll instead of pitching up .

The answer is due to Gyroscopic precession where any inputs to a gyro scope will only take effect after 90 degrees.

Your rotor is a big gyroscope

The following video is probably the best explanation of gyroscopic precession that I could find.

http://www.youtube.com/watch?annotation ... TjGTxSevHE

[Lady_Gyro]

Interessting topic... one that specifically interests me!

Aerodynamically the pitch change adjusts the wings' flight path making the rotor aerodynamically driven. Proving that we are not weight shift aircraft.

A concept that I always struggle to understand is what makes a gyro pitch up to climb and pitch down for decent.

I've just finished my Gyro training and I was under the impression that pitch is speed and not climbing and descending?! Power is altitude?! No?!

Please correct me if I'm wrong?!

[t-bird]

You are 100 percent correct that power is height and pitch speed. If you fly at 80 miles straight and level and pull back on the stick the gyro will climb, but only if you have excess power. The pitching terminology that I have used is incorrect and should change to attitude.

[Lady_Gyro]

Thanks, it now makes sense!

[t-bird]

Okay but I left out teetering.
Lets asume your airspeed have increased enough to cause reverse airflow on the retreating blade near the hub.
The retreating blade wil move down as a result of decreased lift.
Advanceing blade will move upwards.
This happens at 90 degrease with the fuselage.
The angle of attack increase on the retreating blade , thus increasing lift and the angle of attack decrease on the advancing blade thus decreasing lift.
These effects take only place 90 degrees further, thus inline with fuselage.
Net effect is zero.

[Gyronaut]

Viva Teetering Rotors T-Bird.

Spot-on, you've got it.

Welcome to the Forum Lady_gyro. Interesting first post?

[ZULU1]

I think that i represent a great number of people on this forum, we all know and fully understand flight behavior, aerodynamics of both 3 axis and flex wing aircraft. I have a fair understanding of helicopter flight. But i aint got a clue about Gyros, nothing other than the fact they fly. I read many posts about Horizontal stabilizers, teetering and so on..Maybe those learned members would enlighten us please ? But keep it simple. I do believe that it will be appreciated by many especially when we see a machine flown so we can at least appreciate the pilots skills...

[t-bird]

Hi Zulu

Teetering is the Gyros rotor that teeter from side to side when the rotor is 90 degrees with fuselage.
The picture is of a Gyro from the top.

The blades are rotating anti clock wise.

The forward movement of the gyro causes the reverse airflow as the advancing blade is into the airflow from the front and the retreating blade is with the airflow.- Like flying into the wind with one wing and with a tail wind on the other.

The region is close to the middle of the blade as the blades move slower in the middle and the relative airflow is slower.

You can see from this picture that the retreating blade is now generating less lift than the advancing blade. Only part of the wing generates lift where full wing for advancing blade.

So the retreating blade will move down and the advancing blade will move up. Thus TEETERING.

Then you need to reed my post above this one to understand what happen next.

[weedy]

T-Bird, you also need to explain why/how the rotor turns

[PieterKotze]

T-Bird and the other experts,

Explain low and slow to me please. AAT says my minimum speed is 20 mpu. I never tried it, except in training in a power off hover, so maybe I should (at seriously high agl I would presume). My question is simple, or not, maybe just stupid, but if I want to fly sloooow, what is safe? Height, speed and power setting?

Pieter

[t-bird]

Hi Pieter
I have started a new topic on Gyro slow flight. Have a look at it.

Weedy
I will start a topic on What turns those blades in a day or 2 just for u.

[weedy]

T-Bird, I know why they turn, it's for the benifit of Zulu1 and non gyro pilots

[t-bird]

Hi Weedy
Then start a gyro theory topic for us on what turns those blades.
We can all benefit from it.

[Learjet]

Here we go... this should save a lot of Google cutting & pasting
Link to download the FAA rotorcraft flying handbook
http://www.faa.gov/regulations_policies ... /aircraft/

[t-bird]

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