How many miles per gallon do you get out of your gyro?

ckurz7000

Senior Member
The past couple of days I investigated the optimal power settings for various cruise conditions on my ArrowCopter. It is powered by a Rotax 914 which drives a constant speed prop. So I have two degrees of freedom: throttle (controlling manifold pressure) and prop pitch (controlling prop rpm).

With full tanks and one up I get about 18 mpg. At max gross it is 17 mpg.

Considering the speed and fun I get, this isn't bad at all :)

-- Chris.
 

Stan V

Newbie
Chriss, my 2.2L FI Sooby RAF runs along at 65 mph and burns 5.5 US gal. = 11.8 statute MPG. 18 MPG is great
 

Texasautogyro

Gyro Master Instructor
Ok my MTO custom built with the Rotax 912 IS injected engine burns 3.6 at 5100 rpm at 80kts. Or 92mph so that gets 25.5 mpg.
 

fara

AR-1 gyro manufacturer
Ok my MTO custom built with the Rotax 912 IS injected engine burns 3.6 at 5100 rpm at 80kts. Or 92mph so that gets 25.5 mpg.
Is that 80 knots calibrated airspeed though? From my experience 80 knots in a MTO somehow seem significantly slower than 80 knots indicated on other machines. That would drop your MPG down.
 

eddie

RAF, turbo subaru 230hp
I burn 8.0 gph @ 85 so that is 10.6 in my turbocharged 2.5 subaru. I have also noticed

that I can run 70 to 85 mph and my fuel burn is still the same! I use auto fuel with 10%

alcohol. I noticed when I went from aircraft fuel to auto gas I had to increase my fuel

flow on the ECU to obtain the same amount of power my GPH went from 7.0 gph to 8.0.




best regards,
 

fara

AR-1 gyro manufacturer
Here is a comparison for you. We just developed KittyHawk, a new model classic tube and fabric airplane like KitFox that uses 912iS Sport engine, has 2 axis auto-pilot, Moving map EFIS, ADSB-IN and OUT, side by side seating, a spacious baggage compartment (tailwheel or tri-gear). We are testing the tailwheel #1 right now. Its costs around $100k in this configuration. We used Oratex fabric from Germany that is supposed to save weight and does not require painting like STITS and has UV protection built in (but I would never recommend this fabric ever again, it looks like crap and the tape simply does not have the sticking power of STITS tape). I'd take STITS and paint any day over this fabric.

Anyway, this airplane is doing from initial testing cruise at around 92 knots (106 mph) at 3.7 GPH or roughly 60% power. At about 75% power, its cruises at 99 knots (114 mph) and burns about 5 GPH. These are all calibrated airspeeds.
This is a STOL airplane with wider cabin, taller cockpit and longer cockpit with bigger baggage compartment than its predecessor Apollo Fox. It takes off in about 90 to 150 feet to break ground depending on flaperon setting and technique used. So speed is not its end all desired aspect. Meaning we did not try and make it so it can go fast.
Just some perspective for comparison.

Now having said that, I can tell you we burned 5.5 GPH in the long cross country to Oshkosh and back on average in our gyroplane going about 82 - 84 knots (94 - 97 mph) with a 914UL engine in hot humid conditions in July/August. That's about 17.5 MPG, one up. At gross it drops down a bit. Our trike at same speed did the same leg and was always 1 GPH better usually 2 up.
At 65 knots (75 mph) cruise in our gyro with 912ULS we burned a pretty consistent 3.25 to 3.5 GPH of car fuel 2 up. That's about 22 GPH and that is about its best cruise efficiency balance.
 
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Texasautogyro

Gyro Master Instructor
Is that 80 knots calibrated airspeed though? From my experience 80 knots in a MTO somehow seem significantly slower than 80 knots indicated on other machines. That would drop your MPG down.
Abid I cross check mine with my GPS ground speed on both MTOs I have owned and mine have been dead on in calm wind. I have seen others that are not so accurate. I can fly Houston to Bridgeport north of Dallas and still have over 1 hr fuel left. That's a good hop in a gyro. My gyro could fly from Houston to Oklohama boarder and still have 30 min of fuel left in calm wind. That's over 300 miles.
 

Vance

Gyroplane CFI
Some thoughts on operating costs.

Some thoughts on operating costs.

In no wind conditions The Predator typically gets 12 to 13 miles per gallon.

I have seen as high at 23 miles per gallon flying high enough to take advantage of a prevailing wind (8500 feet MSL) averaging about 98 miles per hour.

When we flew Puff the 752 miles back to Spanish Fork she averaged 15.6 miles per gallon at an average ground speed of 95 miles per hour typically less than 1,000 feet AGL.

I have found when flying direct I typically flies only two thirds of the distance of ground transportation.

I find the hourly cost of fuel ($26.52 @$4.08 per gallon) is slightly less than half the cost of operating The Predator. Hangar rent, insurance, maintenance, oil and annual condition inspections account for most of the rest.

It is hard to put a reserve on a second hand engine. If the Lycoming makes it to 2,000 hours and I can find a similar replacement it will be $3.50 per hour.

I hope my rotor system will see around 3,000 hours for a cost of $3.33 per hour.

There is no telling how many hours the rest of the airframe will go or when I will damage the propeller enough to replace it.
 

fara

AR-1 gyro manufacturer
Abid I cross check mine with my GPS ground speed on both MTOs I have owned and mine have been dead on in calm wind. I have seen others that are not so accurate. I can fly Houston to Bridgeport north of Dallas and still have over 1 hr fuel left. That's a good hop in a gyro. My gyro could fly from Houston to Oklohama boarder and still have 30 min of fuel left in calm wind. That's over 300 miles.
Dead on meaning within a mile or two? I usually find that all analog ASI's that are non-TSO are pretty much on at one speed and then diverge in either direction from there. I am happy if my maximum divergence is less than 5%. GA Type certificated aircraft require 3% or less divergence which is difficult to achieve with these non-TSO gauges and static ports like we do in trikes or gyroplanes. 300 miles is good hop for sure. So you definitely see 912iS burn less fuel even flying low for a given power setting? I know we see that in the airplane. Its the extra cost and complexity of the engine plus the extra 16 pounds of weight that makes it difficult to swallow.
 

Texasautogyro

Gyro Master Instructor
Abid I only use TSO airspeed altimeter and card compass in my machines. I have also done that Dallas flight many times over 30 and have very consistent data on my fuel burns. I usually fly at 3000 to 4000 feet which helps as well.
 

mceagle

Gold Member
Gentlemen, MPG is largely irrelevant. Please, gallons or litres per hour flight time, preferably cross country, not touch and go's. (Litres would be most suitable because of the discrepancy in world gallon measurements)
 

fara

AR-1 gyro manufacturer
Abid I only use TSO airspeed altimeter and card compass in my machines. I have also done that Dallas flight many times over 30 and have very consistent data on my fuel burns. I usually fly at 3000 to 4000 feet which helps as well.
THose TSO instruments are "expensive". $1500 for altimeter and $1500 for airspeed. You get those used?
 

WaspAir

Supreme Allied Gyro CFI
9.9 gal per hour @ 184 mph 32.9 gal tank (helicopter)
Is there an extra 1 in that post? Did you really mean you cruise at 184 mph (296 km/hr) in your helicopter?

That's Chinook speed, on less than 10 gal/hr . . . with 600 mile range . . .
 

WaspAir

Supreme Allied Gyro CFI
yes it does
Well, my book says a nice slick fixed-wing Beech A36 at 65% power/ 10000 feet will do 162 kts (186 mph) on a burn rate of about 13.3 gal/hr, but you're saying you get equivalent speed on 25% less fuel from your helicopter.

I doubt that I'm the only one surprised by that claim.
 

ckurz7000

Senior Member
Dead on meaning within a mile or two? I usually find that all analog ASI's that are non-TSO are pretty much on at one speed and then diverge in either direction from there. I am happy if my maximum divergence is less than 5%. GA Type certificated aircraft require 3% or less divergence which is difficult to achieve with these non-TSO gauges and static ports like we do in trikes or gyroplanes. 300 miles is good hop for sure. So you definitely see 912iS burn less fuel even flying low for a given power setting? I know we see that in the airplane. Its the extra cost and complexity of the engine plus the extra 16 pounds of weight that makes it difficult to swallow.
The 912is is definitely about 20% more efficient than without the "is". I remember cruising at 80 kts solo burning only 4 gph. I wonder how long it will be before we see a 914is.

-- Chris.
 

eddie

RAF, turbo subaru 230hp
I have been using a non TSO'd airspeed and have found it to be one of the most accurate

ASI's I have ever had, even at all speed ranges,its a falcon instrument from AC spruce.





Best regards,
 

ckurz7000

Senior Member
In my experience I found that most ASI instruments are pretty good concerning instrument accuracy but are badly installed. The problem is mostly a bad location for the static port(s), so that 10% error is pretty common. This installation error needs to be carefully determined by accurate flight testing. Most people don't bother or think that a cursory cross check with the GPS is good enough.

Greetings, -- Chris
 
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