Gyro Vs. Helicopter Cruise Efficiency

Vance

Gyroplane CFI
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That is a part of what I love about you Stan!

That is a part of what I love about you Stan!

Birdy- You got me! I should have said less than 20 mph, or less than 15 mph. Ha Vance- We all basically work up to the type of flying that suits our interest best. Your type of flying is out in the open, mine is behind a windshield with the sides open. You love flying over the terrain doing very cool cross country flights. My love is flying in the terrain, having the capability to landing and taking off most anywhere. You enjoy going somewhere more than anyone I know, and I feel like no one loves going nowhere while hovering as much as I do. If I flew from airport to airport with no desire to turn the air around me into a runway at anytime, I wouldn't even consider a helicopter! But, you and I are flying how we like and that is what's important. So comparing the efficiency of both types of rotorcraft doesn't mean a thing, as long as our fun per hour is the most efficient it can get. Can you imagine everyone wanting to fly the same way? Keep stirring the air over the terrain with the wind in your face going somewhere, and I will keep stirring the air in the terrain going nowhere at all with no wind in my face! Stan
You are able to work through the quagmire of my thought process and comprehend what I am attempting to convey.

I am grateful to have you as a friend Stan.

What I find interesting is the number of people who are interested in this subject.

I hope I have not offended anyone with my observation that rotorcraft efficiency is oxymoronic.

Thank you, Vance
 

StanFoster

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Ian- I would vote for the gyro hands down if you can meet your takeoff and landing goals. ......even if it burnt more fuel. There is a lot more to a helicopter that has to work right.....and the desire has to be high to turn any air into your runway so you can set down and take off. I want the ability to land and takeoff most anywhere....but that is just me. If that isnt a pressing desire....then a helicopter starts being a distant 2nd choice over a gyro. A gyro will always be the simplest of rotary flight and can mimic 90% of what a helicopter can do....and much cheaper in the long run.

Thats my opinion and I flew gyros since 1985.




Stan
 

dcnblues

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- "Best range speed...130 km/h IAS
-Fuel flow at 130 km/h IAS...13 l/h"
-AutoGyro Calidus

Same engine, same general configuration:
Helo: 4.75 gph at 90 mph
Autogyro: 3.43 gph at 81 mph
New data from Helo manufacturer:

Our technicians inform you that the min. is 18 litres, at 80 MPH
the consumption is slightly lower, anyway with 17 litres only it
is impossible to fly. Unfortunately we do not have any graph; all
useful information can be found on our web-site and pilot's handbook.

Kind regards.

Clotilde Quinterno
So if you have the same general configuration and similar drag, powered by
the same engine, the helicopter's best cruise is also the minimum power setting to keep it in the air. That does seem like it limits efficiency when talking about fuel burn. Good to know.
 

Vance

Gyroplane CFI
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Fuel cost is a small part of oppreating rotorcraft.

Fuel cost is a small part of oppreating rotorcraft.

But if I have two locations 50 miles apart, with a little bit of room at each place (just enough for a gyro to take off), and I'm deciding on what kind of aircraft I want, and it will be a regular trip and future fuel costs are part of the budget, it will mean something.

I don't have that setup, but wish I did. In any case, they're damn close, which is what the original thread poster wanted to know.

Hello Ian,

In my opinion any rotorcraft is a very expensive way to go 50 miles.

In my personal experience with a Helicopter insurance and maintenance more than double the operating cost per hour compared to just looking at the fuel.

Insurance and maintenance add significantly to the cost of operating a gyroplane.

For me it is about having fun and a life lived well.

When I was a Harley Davidson dealer people would try to justify buying a Harley Davidson by getting excited about the gas mileage when the reason they wanted it was because they felt they would have fun on it.

I would try to explain to them that it was ok to feed their fun appetite and when they get to the end they would regret the things they didn’t do to have fun.

They would call their wives from the agency and talk about how the money saved on gas would make the payments.

It is my observation that the operating costs on my 99 Ford E350 that occasionally sees 16 miles per gallons are less than the operating costs of a Harley Davidson Motorcycle that usually operates on the far side of 50 miles per gallon.

In my opinion your operating costs of a gyroplane will be less than the costs of operating a helicopter and still much more than my 99 Ford E350. Weather is always a challenge in aviation. The logistics are also a challenge if you are trying to make a regular trip.

My fatherly advice to you Ian is to give into your desires for a rotorcraft, learn to fly and live life on a higher level.

I feel it will make you a better writer.

Thank you, Vance
 

dcnblues

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Lovely post, Vance. Thanks, can't argue, and will keep the operating costs in mind. I've stuck every receipt for my Hayabusa over the past 12 years in a file, and have never added the numbers up, but I know they'd be surprisingly huge.:)
 

Alfa wave

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Dennis,

Thanks for sharing your experience.

How much power do you think would need to be applied directly to the gyro rotor (i.e. PPR) to achieve the same cruise efficieny as a helicopter? That is, assuming all other things being equal (weight, drag, etc.)
About 4 hp
 

Jean Claude

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Mechanically adding a torque to the rotor reduces the drag at equal lift. So, less power is required on the propeller.
But the total power required (i.e propeller and rotor) does not decrease.
Admittedly, directly applied to the rotor, the power efficiency is better than pneumatically coming by auto-rotation.
But unless you re-adjust the pitch of the blades, the extra is losted by the increase of the rotor speed produced.
 

C. Beaty

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With Dick DeGraw’s partially powered rotor, with power split between rotor and propeller via a differential gear, there is very little change of rotor RPM with power change. More power to the rotor reduces power extracted from the airstream so the rotor flies at a reduced angle with increase of power.

I don’t remember exact numbers but Dick said something like a 25 RPM change of rotor speed between full and minimum power with fixed rotor blade pitch angle.
 

Jean Claude

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This confirms my calculations, Chuck.
For example at 67 mph without changing the pitch of the blades, adding a torque of 170 Nm increases the rotor speed from 373 rpm to 395 rpm, while the rotor drag decreases from 794 N to 634 N (at the same lift of 1000 lbs)
A.o.A disk reduces from 10 degrees to 8 degrees

This means that an added mechanical power of 7 kw on the rotor only saves 4.8kw of propulsion
or about 7 kw on the propeller shaft when its efficiency is 0.7
So all the profit is lost!

If now the pitch of the blades is increased from 3 degrees to 3.7 degrees to keep 373 rpm, then disk A.o.A is 7.2 degrees and the drag decreases to 568 N.
This is 6.8 kw of drag saved, or 9.7 kw on the propeller shaft with an efficiency of 0.7
So, the profit is now 2.7 kw
 
Last edited:

Jazzenjohn

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That is a far different number than the often repeated '1 hp to the rotor equals 5 hp from the prop'. I tend to think that your numbers are much closer to the truth Jean Claude. I would imagine that 1 Hp to the rotor is .9 HP after transmission losses minus anti-torque losses, and that .7 prop efficiency times (.7??) windmill efficiency to spin the rotors would equal ~.49 Hp. Add in the additional weight and complexity and I agree with you, All the profit is lost.
I still see the value of it in a DeGraw machine where all the jump takeoff mechanics are already there and available for inflight rotor power, so no additional weight or complexity, and anti torque is handled by differential prop thrust.
 

Jean Claude

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About 500 h (FW + ultra light)
It is possible that Dick Degraw got this pitch increase without his knowledge, by a blade twist due to the little overspeed of the rotor.
 
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