Ground Effects on the rotor

All_In

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Seems the biggest difference between FW and rotorcraft in auto rotation is FW's create lift by just sticking out and being there. While landing as we flare our rotors slow down the lift is also reducing! You are not going to have ground effect last as long as a FW as our blades reduce RRPM there is less air moving over the blade/wing and less lift is being generated. No fixed wing can stop with a zero roll landing... Well unless you spin it in but that will not have a happy outcome.
 
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WaspAir

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And yes, I have previously answered and provided explanations as to why a gyroplane would not be able to climb out. You just need to go back and read them.
Unlike you, I actually did read those old posts. The curious can find them in this thread at #18-24 above. You proposed a layer of cold air next to the ground, which was a pretty stupid notion given that I reported a temperature of 113 degrees Farenheit, and you also proposed that I was overloaded, while I was a skinny fellow flying solo in a two-place, and you proposed flying behind the curve, while I was doing 70 mph. All of that was unadulterated nonsense. Citing that b.s. now with a wave of the hand doesn't make it convincing, especially when every reader here can just zip up the thread and see that you had no clue what you were talking about.

I've gotten tired of your usual modus operandi -- blow some smoke, change your definitions willy-nilly, assert that you're "correcting" others, and declare victory often, sometimes years later.

Clueless buffoonery does not advance any understanding by readers here, and the bogus stuff you push on the uninformed might someday actually turn out to be dangerous for those not sufficiently astute to tell the difference. You do a disservice to our community with this hogwash.

I think it's time for a dose of your own medicine:.
I think it was my good friend Ed Aldifer that said: "I refuse to argue with stupidity".
As you and others have said, if the shoe fits . . .
 
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birdy

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Who was it said" you can fool most of the people most of the time, but youll never fool them all, all the time".

Dennis, jargon, endless yappn, smoke n mirrors and self appointed supiriority wont fool everyone, just the ignorant and gullible.
I pitty them.
 

DennisFetters

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I hope I have not wasted my time with all of you. Some of you, yes.

Good luck through your path of darkness.
 

Gyro_Kai

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Dennis,

you are obviously wrong. I am not surprised, that so many of your constructions have crashed. You just don't even know the physics behind flying.

Kai.
 

All_In

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I care about having the right knowledge, but not about being right!

I pride myself in being able to finally see I'm wrong and change to the correct information faster than most and it does not even winch my ego.

I rejoice in being corrected because I now have the truth!!! My ego feels better changing to the truth than being right about anything.

Then I will fight to debate it until it too may be changed completely or modified sightly.

Which leaves me at like my good friend Vance would say... I'm now confused at a higher level!

I love that line as it is so true.
We never know it all!!! The more I know about complex theories the more unanswered questions I have.

You know for me; math & programming is the one language where you CANNOT BS or lie!

This Forum rocks for teaching me so much with the math and physics to back it up = no lying or fooling themselves or us.

For the newbies just trying to figure out who is who in this expert zoo ... Most of my heroes that have taught me the most on this forum have responded with the correct answers in both the Dennis threads!

Understand they are all human and almost all of them have been corrected by one or the other experts about some small detail.

The biggest difference between Dennis is they all have understood the truth and submitted to it and changed their opinion just like me and no one thought it was a big deal. They all have only gained my respect for that!

Only it very rare for them to even be slightly wrong and I do it almost daily.

I see now that I'm bless my ego is bolstered by being wrong but now having the correct anwser.
 
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Rick E

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Just wondering if any of you guys take time off from studying physics to go flying??????
 

WaspAir

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Just wondering if any of you guys take time off from studying physics to go flying??????
If you work at physics for a living (as I used to) then physics pays for the flying, which works out nicely!
 

StanFoster

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Waspair- Now that was the smartest post yet! You made a good living at what you know....and it supports the flying habit you have very nicely! You sir is what I respect and call being a success at life.
 

All_In

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Not sure over 10,000+ logged FW, 260+ ultralights, sailplane, hang-gliders
Just wondering if any of you guys take time off from studying physics to go flying??????
Hi Rick!

Well Birdy and the boys fly a little? HeheheheHahahaha
https://www.youtube.com/watch?v=yoeDCJE_5hA

Notice the safety foot ware?

Birdy flies his gyro to make a living mustering cows BTW!
Chuck is the father of rotorcraft engineers. He's in is 90's IIRC and does not fly as much as he used to.
Same with most of the rest except for they are still flying more than the national average.

As for me I learned this stuff in the early 70's so I'm very rusty except this forum allows me to do the math and keep my skills up.
Use it or lose it.

I fly my Archer like most people use their car.
I was a Piper Dealer, FBO, flight school, hangers etc. for 10 years and now have over 10K hours in all types of aircraft including aerobatics most of it in FW's, as I recently only discovered the best kept secret of flying fun so I 'm still a student here.
There is no way a private pilot can rack up hours like that if you don't fly every chance you get?

In fact Rick all of them and me like to fly more than post. Thanks for asking it does help know who is who in the expert zoo.
 
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StanFoster

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I no longer fly and have no plans of flying again. However, I am sending a lot of lead flying out my gun barrels ! I enjoy seeing others enjoying the thrills I had flying....and reading these aerodynamic discussions is interesting to follow.
 

WaspAir

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Waspair- Now that was the smartest post yet! You made a good living at what you know....and it supports the flying habit you have very nicely! You sir is what I respect and call being a success at life.
Very kind of you, Stan -
but if whatever you're doing keeps you happy, that's success in my book. It will be a different formula for each of us.
 

Vance

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My non-technical flying observations about gyroplane ground effect.

My non-technical flying observations about gyroplane ground effect.

I have been avoiding posting on this thread because I don’t want to try to explain or debate something I don’t understand very well.

I believed for a long time there was no ground effect with a gyroplane because the SparrowHawks, modified RAFs and the Predator drop right through anything I perceived as ground effect.

I could not feel any down wash from the rotor in The Predator (the others are enclosed).

Then to answer a question I experimented with The Predator and found I could fly level at 30kts with a lot less power six inches above the ground compared to ten feet above the ground. I posted on my observations early on in this thread.

Then I started flying a Cavalon (Puff) by AutoGyro GMBH.

The Cavalon will float a long way up to about five feet above the runway when landing and if I lift off early she picks up speed best near the ground. I often overshoot my target touch down point because of the way she floats.

Puff takes very little power in to fly level the length of the runway compared to being even ten feet in the air.

In short there is no missing the ground effect in Puff and when I did some testing it appears to me that I get somewhat less ground effect in The Predator.

Puff is 150 pounds lighter than The Predator and has a lot less drag so the performance is very close with only 115 horsepower compared to 160 for The Predator. Climbing out I am typically at 2,450 rpm so The Predator is probably making closer to 145 horsepower at that rpm. At top speed (around 95kts) she is close to 2,700 and when we tested the engine at SMX on a dyno the Lycoming IO-320 made 161 horsepower at 2,700 rpm. She is probably making less now after around 1,000 hours although she still has good compression.

The Cavalon rotor spins at close to 400 rrpm and The Predator spins at around 315 rrpm.

The Predator has a useful quirk in that the horizontal stabilizer gets ground effect at around 3 feet when it is time to flair and I can feel the tail kick up so I can land her with my eyes shut. That is the ground effect like a fixed wing so it should not be a part of this thread.

I can’t explain the difference and have tried to mention the main differences between the two gyroplanes.

Before someone asks the rotors are a very similar height in The Predator and Puff. Puff has a 28 foot disk and The Predator has a 30 foot disk.

I never experimented trying to measure the ground effect in SparrowHawks or modified RAFs.

I have no desire to debate the how of it; I am just reporting my observations flying gyroplanes.
 

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birdy

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Interesting Vance.
Only difference i could get off the top of my hollow head would be a difference in disc AOA at 30kts.
The pred is heavier, so the disc would need a higher AOA, meaning the RTV is not as virtical and less of the disc is close to the ground.
But, my head is hollow, so it could be just an echo. ;)
 

Jazzenjohn

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Wouldn't drawbar pull from a gyroglider at 1 foot and 15 feet above the ground, compensating for the different angle of the pull, give a more definitive answer?
 

kolibri282

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All the theory I have read so far seems to indicate IMO that there is no difference in the physics of ground effect between helo and gyro. My idea is that the difference is in disk loading. Ground effect reduces induced velocity. If the disk loading is low, so is induced velocity and ground effect is not felt very strongly. I think this is why Chuck asked for AUW. It would fit in nicely if disk loading for the Cavalon were higher, something the higher rrpm seems to indicate.
 

Vance

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What were the AUWs in each instance, Vance?
Hello Chuck,

The all up weights are typically around 1,100 pounds for The Predator and 950 pounds for the Cavalon.

The Predator has 8.5 inch chord 30 foot Sport Copter blades and the Cavalon has close to 8 inch chord 28 foot extruded blades.
 
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