SparrowHawk performance at high density altitude

[The Rock]

I have been lurking for over a month now, and really enjoy the forum. It is time that I join in. I have been interested in gyros since RAF built the, IMHO, first attractive, enclosed gyroplane. In 1995, we flew to the PRA convention at Putnam Co to get a ride in an RAF 2000. I was appalled by the lack of pitch stability, and put aside my interest in gyros until Oshkosh last year when I saw the SparrowHawk.

From tracking this forum, it appears that the SparrowHawk resolves the pitch stability issue, but I have some questions regarding its performance at high density altitude. I live near Denver, CO where density altitudes can approach 9000 feet on the runway in mid-summer. Is it even possible for any gyroplane to provide reasonable performance at anywhere near gross weight under these conditions?

Udi, since you live in Ft Collins, you may be best able to answer this question.

The Colorado SparrowHawk distributor is building an RAF modified with the SparrowHawk kit and an EJ20 turbocharged engine. I question whether this will solve the density altitude problem, because in looking at the torque curves for this engine, it is doubtful that in the lower rpm band it has the torque necessary to get a propeller optimized for the upper horsepower band up to speed. Does anyone have any experience with either a turbocharged or supercharged Subaru engine at high density altitudes?

[Mayfield]

The SparrowHawk with normally aspirated EJ22 would not give acceptable performance at high density altitude.

We do not yet have any solid test data on the EJ20 installation.

I suspect that the minimum engine that would do the job is the FI EJ25 normally aspirated. We will offer the EJ25 as an option. Even with this engine performance would (obviously) not be as good as at lower altitudes.

One of the problems with adding more and more HP is that we feel that our 85MM belt PSRU is good to about 160 HP. To be safe with a turbocharged engine with our PSRU it would have to be turbo normalized.

We have not even begun to look at this option.

The other option is to go to a 100MM belt PSRU. This would require re-engineering of the entire drive system and the numbers of you folks that live above a significant percentage of the earth's atmosphere do not yet support the expenditure.

That being said, I believe that "acceptable" performance will best be achieved by installing the EJ25.

Jim Mayfield

[The Rock]

Jim,

Do you have anyone building a SparrowHawk with the EJ25 that will be using it in high DA? I need to be satisfied that the SH will operate effectively in my conditions before ordering a kit.

[Mayfield]

Cliff,

Not yet. We are doing the first two EJ25 installations now. Hang in there and stay in touch. We'll try to keep you informed.

Jim

[Udi]

Cliff,

I don't know much about Subaru engines, but I would think that a turbo charged EJ22 would work just fine. Colorado Component Rebuilders in Denver can probably make any SUB conversion you want.

Have you talked with Bill Clem? Bill flies a Dominator with a turbo charged Rotax 914. He gets fantastic performance, and his machine is not light.

We, who fly gyroplanes at high altitude, get penalized twice. First, we lose 20-30% of propulsion with a normally aspirated engine (just like any FW airplane) and, on top of that, we also lose rotor efficiency. The rotor has to spin faster at high DA, which means a higher rotor drag. So we have to use longer rotor blades as well.

I decided to go with a light gyroplane with adequate power. My Air Command is not as light as I would like it to be, but it is reasonable. A gyroplane that is a hot rod at sea level would have adequate performance at our altitude. I guess that's harder to do with a lead sled (i.e. a two place machine).

Udi-

[birdy]

Jim,has anyone fitted a 914 to one of your machines???

I replaced a EJ22 with a 914 on me RAF and the performance overall improved out of sight.
I'm in central Oz,at 1800' ASL and the air can get hot/thin here in summer when it's 48c and 90% humidity,and it's in these conditions that the 914 realy shines.

[KenSandyEggo]

I think a mistake a lot of us make/made is that we're getting 130 h.p. out of our injected EJ-22s. That 130 horses is made at around 5500 rpm. Most of us are only turning around 5,000 on take-off. I believe that's a significant difference. Maybe we're only cranking out about 100 at that lower rpm. That would explain Birdy getting better performance out of the Rotax, whose h.p. is figured at the usable rpm.

[mceagle]

Birdy,
Was your EJ22 a RAF modified carburettor engine with Distributor? If so they were considerably down on horsepower compared to a standard engine.

[birdy]

It had the holly carb and CTI and if it pumped 130 horses in these conditions I'm a chinaman.
The 914 has the altitude compensating waste gate on the turbo so it is the same as opperating at sea leavel,giving the true rated hp with 70kg less weight less than the EJ22.


cruise=70-80mph
@4200rpm, manifold pressure at these rpm is usually 0 or less.
Max=5600rpm,with 6psi boost.
14-15LPH with full fuel

[LARRYEBOYER]

Rock, I would be interested in you keeping an update on the EJ-20 turbocharged engine. It is my understanding the turbo can be set mechanically to come in at 3000 to start the boost. I have a EJ-20 STI FI WRX engine that was rebuilt and ported and balanced. I was going to put it on my new RAF but decided to go with the EJ-22 with a cam grind. I was concerened with to much power. I understand GATES makes a super strong 60mm belt able to handle 250+ HP. I would like to see the finished engine installation on the RAF. I may change engines later on if it works well for your friend. Parham told me he thought the EJ-20 would make an excellent direct drive. Boost it at 3000RPM andturn it to 4000. About 160hp!

[rfi]

A standard 85 MM wide HTD belt is marginal on an EJ25. The new GT-2 Gates belt which has random Aramid fibers embedded in the Neoprene teeth allow the belt to handle 70% more power than a stock belt.

In fact, a Gates engineer said, unofficially and off the record that an 85 MM wide belt would handle 270 Hp. A 60 MM GT-2 belt would be good for 170 Hp but not 270 as Larry mentioned. The EJ25 should develop adequate Hp at a mile high, especially with the Stratus cam grind which increases power from 165 to 180+.

The EJ20 is pretty much a bullet proof engine and will run wide open days on end. In 1991 an endurance test was run on a government test track near Tucson, AZ during August where temperatures reach as much as 110 degrees. Three Subaru Legacy autos with turbocharged EJ20 engines were run non-stop for 100,000 Km (62,000 Miles) in 18 days at an average speed of 130+ miles per hour. The autos were only stopped long enough to refuel and/or change drivers. All three engines completed the endurance run without a problem.

It is true that the EJ20 could be used direct drive. I have several customers that are flying direct drive EJ22 engines on gyros and fixed wing aircraft. One installation which is on a Europa airplane has over 600 hours of flight time. The only problem with direct drive is that a smaller diameter propeller has to be used which reduces efficiency and increases noise.

[Hognose]

The problem with rated horsepower is that you don't fly with rated horsepower -- you fly with thrust, and horsepower is only one piece of that puzzle (the prop's another piece, and the best prop at sea level on a standard day is a different animal from the best prop at a density altitude of 5000'.

That said, continuous rated HP of the 914UL is the same as the 912S -- 100HP. The 914 has a takeoff power setting for 115 HP, but you are limited to five minutes. So the best way of looking at a 914 is probably as a turbonormalized 912 (it is not strictly speaking, in the literal sense, turbonormalized... but that's the effect).

The 914 is about 170lb installed, complete with accessories and fluids. A soob is 200 and up.

cheers

-=K=-

[KenSandyEggo]

Speaking of Gates Belts, I just looked at a new NAPA belt I have for my alternator in my hangar, and they are made by Gates for NAPA. My NAPA prerotator belt is from NAPA and I've had it on there for several years and my prerotator gets quite a workout while waiting for takeoff at my homefield. I took off the 85mm drive belt (Gates GT2) a few weeks ago after several hundred hours for replacement, and it looked brand new. Not one sign of wear.

Speaking of Rotax, Birdy says his Rotax-equipped RAF performs better than with the Soob. I've flown 1,000+ lb. Ercoupes with a mere 85 h.p. and they've performed fine. I flew one with a 100 h.p. 0-200 and it felt like a rocketship compared to my 85 horser. I just wonder what h.p. we are really getting from the EJ-22. If a 100 horse Rotax outperforms it (according to Birdy), I'm wondering what a new 125 h.p. Continental with Fadec would do on mine.....or a Lyc 0-235. Gee, I wish I had a couple cardboard boxes of money laying around somewhere.

[Heron]

HIgh density alttitude? Or low density at high alttitude
I am confused . . .
Heron

[Udi]

Same thing, Heron.