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Editorial: Oshkosh Ottering

By Tracy Crook. Originally published in the Rotary Aviation News, Issue 4, 1996

As usual, Oshkosh was an overwhelming experience in “aviation immersion” which was fun, educational and takes at least a week to recover from. The Mazda hummed flawlessly all the way up and back without missing a beat. Dodging a few thunderstorms on the way up added a couple of hours to the flight plan and the Hobbs meter rolled past the 300 hour mark shortly after I got back.

I arrived a couple of days early and was the first aircraft to park in the Auto Powered section. There were enough hard core aviation nuts around to notice the different sounding engine and within seconds after engine shutdown I got asked the now familiar question “what have you got in that thing?”

Watching people’s reaction to the answer is always interesting. When I first started flying the rotary about a year and a half ago, the response was mostly negative with comments like “nobody has had much luck with those engines”. Some would react with stony silence. It’s not hard to tell they believe if man were meant to fly behind an auto engine, Lycoming would have built them. I used to try and discuss the subject with them until I realized it was a actually a religious issue.

Word has started to get around that they really do work and the reactions are now mostly positive. This is actually quite gratifying. I thought it would take a lot longer.

By the time Saturday came, there were 15 alternative powered aircraft in the auto powered section and an unknown number who chose to park in their aircraft type section. I saw some of these but I’m sure I missed a lot. A few people I talked to at Oshkosh told me of several Gyrocopters they saw in the rotorcraft area powered by Mazda 13B engines. I believe there are more 13Bs flying on gyrocopters than on airplanes at the present time. I know of 7 in Florida alone. This is not surprising since the time between deciding on an engine and finishing the aircraft is much shorter for a gyrocopter. This also tells me that the rotary is gaining momentum rapidly.

Here’s the breakdown of what I saw. I’ll go over the specifics on some of them later.

Engine Number seen

---------------------------------------------

Ford V6 3.8 L 5

Mazda 13B 4

Subaru EJ 22 3

Subaru EA 81 3

Buick V8 (1963) 1

Chevy 454 1

The predominance of Fords this year reflects the long period that these engines have been under development. Some of them had been flying for over 10 years although the number of hours flown was relatively low. Most had between 100 and 300 hours with the highest being around 325. The only recent installation was in Jerry Schweitzer’s RV-6 (125 hours). Jerry had previous experience with the Ford V6 in a V6/STOL on which he accumulated 400 hours of flight. Several Ford power builders gave interesting talks at the Alternative Power forum on Saturday and their experiences reinforced my feeling that development problems were common. It’s nothing that can’t be fixed but the Ford is not as close to being an “install and fly” engine as the rotary.

Mazda 13Bs were flown in by Allen Tolle (Powersport -RV-3), David Atkins (Atkins Aviation), myself and a Christavia Mk 4 whose owner I didn’t get a chance to meet. All except the Powersport were using Ross reduction drives. At least some of the 13B powered gyrocopters were using Ross drives as well. I previously described most of these 13B installations so I won’t go into a lot of detail here.

The only changes I noticed on Atkin’s machine (RV-6) was the addition of an auxiliary radiator to improve cooling and a new IVO Magnum prop in place of the McCauley that was installed at Sun ‘n Fun. He used a Mazda RX-7 oil cooler for the added radiator. The prop was a three blade model and is the same prop I want to try when time and finances permit.

FINALLY! A Flying Legacy.

I finally got my wish (three times over) to see an actual flying installation of the 2.2 L Subaru Legacy engine. The prototype from Stratus showed up on the front end of a Cessna 150. The PSRU was one developed in cooperation with Northwest Aero using a belt drive. Stratus claims they will have this engine available for sale to customers within a few months. Price range was in the $10 - 15K range depending on HP. They plan on offering 160 and 180 HP versions. The one on the Cessna was claimed to be 180 HP and used a pair of two barrel downdraft Webber carbs mounted directly over the intake ports on the heads. At least Stratus is flying what they advertise. I still saw no examples of NSI or Formula Power 2.2 L Subaru based engines on the flight line in spite of seeing their ads for years now.

I found the use of short (about 1 and a half inches), straight intake manifolds to be very interesting. Up until this point, the engine sellers have all stressed the importance of long intake runners and tuning for good horsepower. I always thought this was an attempt to convince builders that it took super smart engineers and hundreds of hours of dyno testing to arrive at a good intake system. In other words, they were saying, don’t try this at home, kids. I accept their use of short, straight intake manifolds as proof that the ones on my 13B rotary were not such a bad idea after all.

As further evidence that this does work, take a look at motorcycles. These are some of the highest power per cubic inch engines in the world and the carburetors are coupled directly to the intake ports on the heads.

The two other 2.2 L Subarus were builder conversions that took the “stock is best” approach. Both of them used the stock fuel injection and ignition systems. Unlike the Mazda 13B injection, the Subaru injection is a fairly simple, compact and lightweight system that comes close to fitting inside the normal aircraft envelope. The Vari EZ installation used a belt drive. (by Eggenfeller) and was mounted low enough (due to the belt drive offset) so that the stock manifold and throttle body did not cause clearance problems. The other 2.2 L was in an RV-3 and used a Ross drive. This builder cut off the intake manifold just after the 90 degree elbows at the heads and fabricated his own low profile manifold from that point on using carbon fiber composite. This manifold was a work of art and I’d love to know how he formed those graceful compound curves and glass like finish. The stock throttle body & ECU was used on this installation as well.

Both of these builders using the “all stock” approach made realistic horsepower claims of 130 HP which is the rating that Subaru gave the normally aspirated EJ22 engine.

INFO you can use

The purpose of this newsletter is to distribute the kind of information which will help you design and build reliable and affordable aircraft engine solutions based on the Mazda rotary. I’m doing the best I know how toward that goal but if I’m missing the boat, let me know. Questions, subjects for articles and suggestions of any sort are welcome.