Gyro Vs. Helicopter Cruise Efficiency

DennisFetters

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If the Mosquito were burning at a set rate of say 4GPH, what 2 speeds would it fly at, and what 2 speeds would the Bee fly at? Wouldn't that be the way to make the fairest comparison of the 2 admittedly very different aircraft with respect to cruise efficiency?
Yes it would, if both aircraft were loaded to the same gross weight.
 

Rotor Rooter

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Yes it would, if both aircraft were loaded to the same gross weight.

The Sikorsky X2 has a number of unique features, however this craft might provide some answers on this subject in the future.

It would be interesting to find out; at what forward speed the propeller comes into play and what ratio of mechanical V.s. aerodynamic power is delivered to the rotors at various forward speeds.

Dave
 

Fl90

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Guys, the original post was about cruise. Not turning, slow flight, hovering, or climbing.

I don't think the Mosquito air would take off with 36hp, but I think it can cruise with less.

Again, I'd love to see the comparison in fuel consumption between a Mosquito air and a Bensen with a Rotax/MZ and DW's, with the 2 craft flying together from point A to B.

Phil.
 

Jazzenjohn

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According to the graph, the Helo as well as the gyro has a minimum power required speed. What would be interesting to me is to compare the speeds and the fuel burn in the open Mosquito with the gyro. I think the minimum power required speed in the gyro would have a lower fuel burn than the helo.
 

dcnblues

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If no one minds, I'm going to bump this topic as I find it interesting, but inconclusive. And maybe there's new arguments to be made here in 2012. I'm new to autogyros, but in my reading so far, it seems there are popular engines that have been in both helos and autogyros. Aren't there any comparisons to be made between types of aircraft using the same engine (say the Rotax 912 or 914)?

I also support the thinking that defines efficiency (for the purposes of this thread) as GPH. Hard to argue with that, especially when one is cruising anywhere over 80mph using less fuel than your average automobile.

PS I'm new to rotorcraft, but nothing I've read so far (in specs, etc) uses the aircraft terms 'low cruise' and 'high cruise.' Have I just missed it, or is there a simple reason for this? Thanks.
 

Stan V

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I believe this thread should have remained dead, just my opinion. everyone's got one ya-know!
 

Fly Army

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I think an aerodynamically sleek design such as the Arrow or even the Calidus powered by a 914 with a constant speed prop could give the old Robby-copter a pretty good run for the money. Maybe even walk away from it. Certainly it would have about 90% of the R-22's capability at about a third of the operating costs.
 

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Aren't there any comparisons to be made between types of aircraft using the same engine (say the Rotax 912 or 914)?

912 'ferel' gyro.
Cruise-50kts-14LPH

Ch-7B heli.
Cruise-75kts-15LPH.

Both single seat, both near the same weight.
 

kolibri282

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Both single seat, both near the same weight
The power required scales to the third power of airspeed. If the helicopter had the same aerodynamic characteristics as the gyro it would need 1.5^3=3.75 times the power of the gyro to achieve a 50% higher speed. The two aircraft are obviously aerodynamically very different since the helo flies that speed with just 15/14=1.07 or 7% more power, assuming that fuel consumption goes approximately linearly with power. (I take it that LPH is the amount of fuel per hour)
 

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Apples and Oranges. They're different crafts. I think the answer to the question of which is more efficient probably is: both. Seems like at lower weighs, Gyros are the winner. Then once you reach a certain weight, helicopters take over. I don't know where that weight is, but i'm sure someone is more than willing to research it (i'm not, lol).

Also, can't you further increase your gyro efficiency with a tractor config?
 

Rotor Rooter

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It appears that the power-consumption / weight-ratio of a comparable gyrocopter and a helicopter are esentually the same, at moderate forward speeds. An example is the Ultralight - Mosquito and the Gyrobee.

IMHO, a merging of the recreational gyrocopter and the recreational helicopter may take place in the future.
All power will go to the rotor(s) for VTOL, and for forward flight there will be spliting of power between the rotor(s) and the propeller(s). An advantage of this split power is that there is no 15% power loss resulting from the aerodynamic transmission of power from the propeller to the rotor(s) during forward flight, particularly at the higher cruise speeds that will be obtainable.


Dave
 
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StanFoster

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One thing that is being overlooked is how efficient it is when a helicopter can actually land at most destinations, instead of the nearest airport. Unless we are talking airport to airport, then the efficiency swings toward the helicopter. Just flying over without landing isn't completing the mission. Stan
 

dcnblues

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One thing that is being overlooked is how efficient it is when a helicopter can actually land at most destinations, instead of the nearest airport. Unless we are talking airport to airport, then the efficiency swings toward the helicopter. Just flying over without landing isn't completing the mission. Stan
Landing's not the limitation, it's the takeoff distance, if I'm not mistaken.
 

dcnblues

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Aren't there any comparisons to be made between types of aircraft using the same engine (say the Rotax 912 or 914)?

912 'ferel' gyro.
Cruise-50kts-14LPH

Ch-7B heli.
Cruise-75kts-15LPH.

Both single seat, both near the same weight.

I was also assuming similar faired cockpits.
 

dcnblues

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The power required scales to the third power of airspeed. If the helicopter had the same aerodynamic characteristics as the gyro it would need 1.5^3=3.75 times the power of the gyro to achieve a 50% higher speed. The two aircraft are obviously aerodynamically very different since the helo flies that speed with just 15/14=1.07 or 7% more power, assuming that fuel consumption goes approximately linearly with power. (I take it that LPH is the amount of fuel per hour)
Kolibri, that's over my head. But it looks like those numbers say 'advantage helicopter.' Can you convert those numbers to fuel burn at typical cruise?

I'd say there needs to be a conversion chart / graph. In any argument over 'efficiency at cruise,' I'd have to say that cruising at 80mph at 3gph would beat cruising at 100mph at 6gph. Agree or disagree?
 

dcnblues

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Okay, here's another comparison with rough numbers. Both streamlined, two seat tandem, faired fuselage, same engine, identical max takeoff weight (the helicopter is 30lbs heavier empty). Both seem to burn about 5gph/100mph. Seems like a push to me:

-Helicopter with cruising speed of 100 mph, 18-20 lt/h consumption
*not from flight manual

CH-7 KOMPRESS PILOT’S HANDBOOK / Last release MARCH 2010

Ch-7 Kompress two seater, with Rotax 914 engine, power CV 115,
FRAME : trestle, tubes, fiber cabin, plexiglas canopy.
ENGINE PROPELLER GROUP: Rotax 914, 4 cylinders, 4 strokes, turbo, liquid cooling system.
- *actual tare weight kg. 280
- *maximal take-off weight 450 kg. / 992lbs
- *fuel tank capacity l. 40 = at kg. 30
- *fuel hour consumption at 75% of the maximum developed engine power: 20 l/h (5.28 g/h) *edit
- *useful load kg. 170
Maximum Range 56 KIAS


-Autogyro 2 seat tandem

Flight Manual Calidus SECTION 5 PERFORMANCE
Revision 2.0 – Issue Date 01.05.2011
Take-off weight/mass (max.):…450.0 kg / 992 lbs
5.8.1 Fuel Flow
The following fuel flow figures are provided as estimates and do not constitute certified performance. Exact fuel flow will vary with environmental conditions, cleanliness of propeller and rotor, piloting technique (minimum side slip), and power setting. For additional procedures about proper power setting consult SECTION 9 for supplemental data concerning the variable pitch propeller, if installed.

-Best range speed...130 km/h IAS
-Fuel flow at 130 km/h (81 mph) IAS...13 l/h
-Long range speed*...140 km/h (87 mph) IAS
* Long range speed is the speed faster than the best range speed which results in a slightly lesser range but represents a good compromise between range and saved air time.
-Fuel flow at 160 km/h (99.4 mph) IAS...18 l/h
 
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kolibri282

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it looks like those numbers say 'advantage helicopter.'
They do, but to such a degree that one must assume the gyro has the aerodynamics of a garden shed.


I'd have to say that cruising at 80mph at 3gph would beat cruising at 100mph at 6gph. Agree or disagree?
Agree.....but very, very marginally..;-)
What I tried to point out is that the relationship between speed and power (=fuel consumption) is highliy nonlinear. If everything else remains unchanged you need eight times the power to push the same aircraft to twice the speed. For your example it works out like this:

100/80=1.25

1.25^3 (1.25 to the power of three) = 1.25*1.25*1.25 = 1.953125

this means that the aircraft flying at 80 mph using 3gph would need 3*1.953125 gph = 5,859375 to fly 100 mph

Thus the aircraft using 6 gph at 100 burns only ever so slightly more and thus is beaten very narrowly.

Your example in post #97 is great but to put a figure to it we'd need the speed at 75% power for the helo
 
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birdy

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The two aircraft are obviously aerodynamically very different since the helo flies that speed with just 15/14=1.07 or 7% more power, assuming that fuel consumption goes approximately linearly with power. (I take it that LPH is the amount of fuel per hour)
LPH= liters per hour.
Yes, these 2 numbers clearly ilestrate the draggyness ofa gyro.

Seems like at lower weighs, Gyros are the winner.
Not weights, but air SPEEDS.
If i nailed the ferel to 75kts, not only would it be orrible uncomfortable after an hour, but the fuel burn will go to bout 20LPH
The best the ferels ever dun [ approx] at full fuel n bout 35 mph is bout 9LPH. The CH-7 wont even break ground burn'n that much.
Also, the ferel can putt round at 3800 erpm, the heli is constant at 5300 i think.

I was also assuming similar faired cockpits.
The majority of the gyros drag comes from the 'back leaning' rotor.
Pods do make a difference, but not much.
At low speeds it makes no difference.

Kolibri, that's over my head. But it looks like those numbers say 'advantage helicopter.'
Miles per gallon, the choppy is miles in frunt.
Hours off the ground per gallon, the gyro of similar weight is just better.
[ its the latter that counts dureing mustern.]

I'd have to say that cruising at 80mph at 3gph would beat cruising at 100mph at 6gph. Agree or disagree?
Depends on whos waitn at the other end for you. ;)

Bloodyell, that makes the choise easy.
Ill take the choppy, with copilot. :)
 

dcnblues

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They do, but to such a degree that one must assume the gyro has the aerodynamics of a garden shed.

Your example in post #97 is great but to put a figure to it we'd need the speed at 75% power for the helo
Thanks for that. Are there data one can use to calibrate or would you just be guessing how much it would help if the autogyro had a collective? 5-10% reduction in drag sound like a good guess?

I know that question, and the premise of this post, is dependent on speed. Drag increases with the square of speed? And power requirements with the cube of speed? Is that close?

In any case, this argument is about looking at curves, and picking subjective points on them. It's certainly my impression that if we had better data on these two aircraft, there'd be a speed where the gyro would be get you there acceptably fast, at far lower fuel consumption. But it would be nice if this thread could establish that, and we don't really have adequate data.

In addition, other variables complicate the comparison. For example, the Calidus has a carbon monocoque and the Kompress doesn't. That alone could be argued as unfair weight advantage. Engine tweaks, fuel carried, aerodynamic differences, etc.

I looked, but wish I'd found better numbers for the CH-7 KOMPRESS. Or the Calidus. There really should be fuel burn charts for these.

Well, I had a second look at the helo's manual and found this, but it doesn't give us 75% power:

 
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