Hang test

[Michael Perdue]

This is a design of my late father and he really was an expert on these things. But I'm still learning and studying.

When conducting a hang test does a tractor hang at a different deg than pusher style gyro's. And if so what deg would I be looking for.

Also what do I take the deg measurement from? The center vertical bar that the rotor head is attached too? or do I take the measurement from the horizontal bar below the seat?

 

[Aerofoam]

This is a design of my late father and he really was an expert on these things. But I'm still learning and studying.

When conducting a hang test does a tractor hang at a different deg than pusher style gyro's. And if so what deg would I be looking for.

Also what do I take the deg measurement from? The center vertical bar that the rotor head is attached too? or do I take the measurement from the horizontal bar below the seat?


View attachment 1160986

I have always done it from the rotor head, or teeter bolt.
I would like to stay in contact, I am going to built a tractor too.....

 

[GyroChuck]

I can not help you with the hang angle. But I looked up the N Number and saw the aircraft has been deregistered. But the N Number is on hold till 6/26. Whatever that means.

 

[Jean Claude]

The angle of any reference fixed to the fuselage (tractor or pusher) should decrease by 9-10° when the gyroplane is hung by the teeter bolt.
(hold the stick in neutral)

For a tractor model, the angle of the rotor disk should be +15° to the horizon when the gyrocopter is standing on its three wheels with the stick in neutral.

 

[Michael Perdue]

The N number is on hold because for some reason the paperwork that is to transfer it from my late father to myself didn't go through. I forget the reason but I sent the the correct paperwork in the first place so I don't know why I didn't go through and I just hadn't bothered to follow up.

 

[okikuma]

The angle of any reference fixed to the fuselage (tractor or pusher) should decrease by 9-10° when the gyroplane is hung by the teeter bolt.
(hold the stick in neutral)
View attachment 1160988
For a tractor model, the angle of the rotor disk should be +15° to the horizon when the gyrocopter is standing on its three wheels with the stick in neutral.

Jean Claude,

In respect to a neutral cyclic position, why does the rotor disk on a tractor gyroplanes need an angle of incidence of +15 degrees as opposed to the nominal +9 to +10 degrees for a pusher configured gyroplane?

During normal level cruise flight, semi-rigid, teetering rotor disk "flies" at nominal +9 to +10 degree angle of incidence when the lift vector of the rotor disk "passes through" the gyroplane center of gravity. All the photos and videos of I have seen of EAB tractor gyroplanes flying at level cruise flight with the semi-rigit teetering rotor system, the rotor disk angle of incidence is at the nominal +9 to +10 degree position.

Wayne

 

[Jean Claude]

Placed on the ground, a pusher has approximately the same attitude as in level flight.
Whereas on the ground, a tractor has a pitch attitude of approximately 5 degrees (unless nose wheel). This means that for the same relative disk angle to the ground during the run, the tractor's disc is only +5° from neutral
(instead of +10° for the pusher)

 

[okikuma]

Placed on the ground, a pusher has approximately the same attitude as in level flight.
Whereas on the ground, a tractor has a pitch attitude of approximately 5 degrees (unless nose wheel). This means that for the same relative disk angle to the ground during the run, the tractor's disc is only +5° from neutral
(instead of +10° for the pusher)

OK, I understand the perspective that you have presented.

Merci beaucoup Jean Claude,

Wayne

 

[Michael Perdue]

The third video from the bottom with the red little wing is my late father's lw-3. And the the tractor that I posted at the start of the thread is his own unique design. He did fly it a few times before his passing. But the last time he flew it he said the engine needed to be moved forward and it lacked rudder authority in a heavy cross wind.

He had the new motor plates cut and drilled but not installed when he past away. I installed the plates and made a new mount for the muffler. I have also replaced his rotor blades. Was 8 core and 87lbs with a 7" core and 55lbs. I have not decided what I want to do about the rudder yet. I have also decided to send the rotax 582 off for a over-haul.

 

[Aerofoam]

There is not much rudder and it is in very dirty air flow, I would think about making the tip rudders as large as possible and putting the control surface on them. They will be in less disturbed air flow and prop wash.

 

[okikuma]

Hello Michael,

I could never understand why you father drastically deviated from the original design by changing the shape and reducing the surface area of the vertical stabilizer and rudder.




All propellers create a corkscrew airflow that will spiral down the fuselage. With fixed wing aircraft, a large vertical stabilizer is created to counter the resultant reaction to that airflow.




Unfortunately, the surface area of the vertical stabilizers and rudder of a tractor gyroplane cannot be as large as a fixed wing aircraft because of the possible impact of the main rotor. The partial solution is to create a dorsal fin extension ahead of the vertical stabilizer, and to add additional vertical stabilizers at the tip of the horizontal stablizer.




My suggestion is to convert the empannage (horizontal and vertical stabilizers and rudder) back to the original design for the LW-3. This should be ample enough surface area when flying behind the Rotax 503, 532, or 582 engines.

As for crosswind authority. All gyroplanes should always be landed into the wind. To help mitigate the angle of a crosswind, land diaganally across the runway or onto a taxiway into the wind.

If the crosswind is greater that the maximum for the gyroplane and one cannot land into the wind, don't fly that day.

Wayne

 

[WaspAir]

I've always been curious about photos like the Corsair with the corkscrew effect. I could never convince myself that it shows a true spiral slipstream, with each droplet of moisture starting at the front and following a tightly wound path around the fuselage. I think it equally likely that it shows the path of the prop tips, where their passage has left a bit of condensation, creating something like a twisted contrail. The prop is rotating, but is the spring-shaped cloud itself actually rotating, or simply moving backwards while retaining its helical shape?



I think it's a cool image, but it might not really show what people assume it shows.

 

[okikuma]

I've always been curious about photos like the Corsair with the corkscrew effect. I could never convince myself that it shows a true spiral slipstream, with each droplet of moisture starting at the front and following a tightly wound path around the fuselage. I think it equally likely that it shows the path of the prop tips, where their passage has left a bit of condensation, creating something like a twisted contrail. The prop is rotating, but is the spring-shaped cloud itself actually rotating, or simply moving backwards while retaining its helical shape?

View attachment 1161042

I think it's a cool image, but it might not really show what people assume it shows.

JR,

You are correct that the visualized, condensed droplets are at the location where the tip of the propeller passed over at that instant of time. Still the airflow of the slipstream is very real and continues to rotate while flowing back along the fuselage.. In the same manner how a wing tip vortice continues to rotate well after leaving the wing tip.

There are countless photos of Bensen B8Ms flying with a small amount of right rudder during cruise flight to counteract the propeller slipstream that is hitting the left side of the vertical stabilizer. Trying to push the nose of the gyroplanes to the left.

Wayne

 

[WaspAir]

I didn't dispute that such flow has been observed, just whether the commonly chosen impressive photos are really illustrating that, or showing something else entirely. It is very hard to trace the motion of any particular parcel of air from imagery of that sort. People naturally assume that air follows the whole corkscrew path, because that's what they expect to see, while not considering the possibility that one bit of condensation is indistinguishable from another, and the aftward motion might not follow the helix.

We should ask questions such as: Is the tightness of the coils suggesting that the rotary velocity far exceeds the rearward velocity, and does that make sense?

 

[okikuma]

JR,

We agree but from two different perspectives. I also agree we should always question conventional thinking. This is how we should always test scientific discovery and evidence base results to continuously evaluate if the findings remain valid.

The helix airflow is not equal in rotation from hub to the tip of the propeller. Propeller blades also create tip vorticies since it is a rotating wing. So the helix portion of the airflow would last longer than the flow created closer to the hub, thus that slower flow could be easily redirected into a straight flow due to deflection of a near by object and the nearby induced drag from the surface of the fuselage. The helix flow does not continue forever. It certianly changes and disapates down the line of flow at some point in time. We have to remember that our air / atmosphere is a fluid and does not always flow equally in the same direction. So your question is quite valid.

Below are a collection of interesting studies and research on propeller airflow.

Wayne

Computational Study of Propeller–Wing Aerodynamic Interaction

Kestrel simulation tools are used to investigate the mutual interference between the propeller and wing of C130J aircraft. Only the wing, nacelles, and propeller geometries are considered. The propulsion system modelled is a Dowty six-bladed R391 propeller mounted at inboard or outboard wing...

www.mdpi.com

https://www.researchgate.net/publication/286185607_Time-domain_analysis_of_the_hydroelastic_response_of_cavitating_propulsors?_tp=eyJjb250ZXh0Ijp7ImZpcnN0UGFnZSI6Il9kaXJlY3QiLCJwYWdlIjoiX2RpcmVjdCJ9fQ

https://www.researchgate.net/figure/Propeller-slipstream-visualisation-as-helicoidal-wakes-being-shed-from-the-propeller_fig2_352039444

https://www.researchgate.net/figure/Helical-vortex-system-and-slipstream-tube-generated-by-a-propeller-1_fig4_334083628

 

[Jean Claude]

The measurements of the torsion of a propeller sleepstram were presented in Naca report 712 fig 23
The flow is twisted by only about 16 degrees relatively to the axis. What the photos of the "Corsaire" show us is not the torsion of the slipstream, just the trajectory of the blade tip through the air.
(If V= 20 m/s, D = 1.7 m and N = 42 rev./s, then V/ ND = 0.28

 

[okikuma]

Here's a link to that NACA Report #712

https://www.abbottaerospace.com/downloads/naca-report-712-propeller-analysis-from-experimental-data/?wpdmdl=18693&ind=1472493158248

Thank you Jean Claude.

Wayne

 

[Michael Perdue]

I can not help you with the hang angle. But I looked up the N Number and saw the aircraft has been deregistered. But the N Number is on hold till 6/26. Whatever that means.

Just took care of the N-number issue. I just hadn't thought about it in a while. FAA sent me a letter to correct the transfer by adding the word "estate" in front of my fathers name. I've corrected it and sent the paperwork in.

 

[Michael Perdue]

Hello Michael,

I could never understand why you father drastically deviated from the original design by changing the shape and reducing the surface area of the vertical stabilizer and rudder.

View attachment 1161029
View attachment 1161030

All propellers create a corkscrew airflow that will spiral down the fuselage. With fixed wing aircraft, a large vertical stabilizer is created to counter the resultant reaction to that airflow.

View attachment 1161026
View attachment 1161028

Unfortunately, the surface area of the vertical stabilizers and rudder of a tractor gyroplane cannot be as large as a fixed wing aircraft because of the possible impact of the main rotor. The partial solution is to create a dorsal fin extension ahead of the vertical stabilizer, and to add additional vertical stabilizers at the tip of the horizontal stablizer.

View attachment 1161036
View attachment 1161037

My suggestion is to convert the empannage (horizontal and vertical stabilizers and rudder) back to the original design for the LW-3. This should be ample enough surface area when flying behind the Rotax 503, 532, or 582 engines.

As for crosswind authority. All gyroplanes should always be landed into the wind. To help mitigate the angle of a crosswind, land diaganally across the runway or onto a taxiway into the wind.

If the crosswind is greater that the maximum for the gyroplane and one cannot land into the wind, don't fly that day.

Wayne

I don't know his reasoning but his lw-3 flew great and had a lot of hours on it before he sold it because he needed money to build the new design. The new design though needs a bigger rudder.. though he did fly it and he stated that he needed a bigger rudder for use in higher cross wind flying. He said on a calm day it was just fine. But as we all know you don't want to be caught lacking authority when needed. So I am exploring options of increasing the height and length but my preference would be to add dual rudders and go a little bigger. I just havn't had the space to work yet. The garage has three aircraft stuffed in it plus storage items. Been trying to sell a Ragabond two place for a few years now to make room.