Oregon Aircraft Design LLC
Hirth, Rotax Sales and Service
We are authorized distributors of Hirth engines. Please call for advice on the engine and gear ratio/prop combo to order for your application. Free shipping anywhere in the continental U.S.A. on any complete engine purchase. This is a $100 to $150 value.
Please call for technical info and pricing for your application. Tel. 503-876-8980
Shop rate
- Our shop rate is $65 an hour and we are darn fast!
- A written warranty and detailed invoice will be provided on all work performed.
- All repair work will require a signed work release and waiver form from the customer.
- An OAD warranty of 3 months or 50 operational hours is standard for all 0-Time spec. units or repaired or overhauled engines.
- A free log book with a concise A&P entry will come with your engine if you do not already have one.
Custom paint work
Includes plastic bead blast and chemical cleaning. We use 500 degree paint on engines and 1500 degree paint on exhaust systems. Your choice of colors, eliminates further corrosion and looks "show quality".
 |
 |
 |
 |
The Hirth line of aircraft engines
3502 60 HP or 3503 70 HP Water-Cooled. Drop-in Rotax 2-stroke replacement in most cases.
 |
 |
 |
| F-36 15 HP | F-33 28 HP | 2702 40 HP |
 |
 |
 |
| F-23 50 HP | 3202 55 HP or 3203 65 HP | F-30 110 HP Fuel-injected |
 |
 |
Also available: 3 specially designed engines for helicopter applications: the H-32 60hp, H-30 100hp and H-37 90hp. |
| F-30 85 HP | 3701 100 HP Water-cooled |
Hirth pluses:
- Hirth has eliminated the cause of the typical 2-stroke failure.
- All models incorporate the very latest aircraft engine technology breakthroughs.
- Exceptional dollar value.
- Fuel injection available for most models (eliminates intake icing potential and constantly optimizes fuel mixture).
- 1000 to 1200 hr. T.B.O. dependent on model.
- Fuel economy rivals any 4-stroke engine.
- Fewer than 1/2 the moving parts of a 4-stroke = better reliability, far less cost to overhaul and substantailly less weight.
- Very easily pull started with the standard digital automatic adjustable ignition.
- More HP per pound of engine weight than all the competition across the board.
- Total one year parts and labor warranty.
Hirth minuses:
- Rich idle with the Delorto carbs. (F.I. automatically adjusts mixture.)
- Proper break-in takes 2 hours due to the Nikasil cylinders.
Some Hirth Engine Installations
 |
 |
| 3203 65hp mounted by OAD on Six Chuter PPC. | 3203 on custom T2.3 PPC. |
 |
 |
 |
 |
 |
 |
What Makes Hirth Engines Different?
When initially looking at the Hirth Aircraft engine line, it may at first appear that Hirth engines are more expensive than equivalent engines from other sources. We would like you to consider the 1000 hr rated T.B.O., one year warranty, superior reliability, and the lower RPM operating range. Over the long run you will find that Hirth engines can actually turn out to be the least expensive choice.
There is an old saying that goes like this. "Horsepower sells engines but torque moves the plane". A superior torque curve brought in at substantially lower RPM is why the Hirths outperform other brands by a wide margin.
Most engines in the light aircraft market were designed for a specific use on the ground and then altered, to be used in aircraft. Hirth engines are designed specifically for aircraft use. Hirth does not make snowmobile, water craft, or car engines and then try to modify them for aircraft applications.
Hirth knows that in order for a 2 cycle engine to perform properly in aircraft use, peak power and peak torque have to be achieved at lower RPM. The engine has to have a realistic T.B.O. and not use complicated rotary valves. The use of Nikasil cylinders and Hyper-Eutectic Aluminum pistons make Hirth engines very seizure resistant.
Our red line CHT is 535 F, our redline EGT is 1256 F. This gives Hirths great fuel efficiency and a very clean oil burn. The use of chromemoly steel crankshafts insure long life with little chance of failure. It costs more to build an engine when you use the best technology and materials available but in the long run you will find that Hirth is the better value.
FAQs
The two most frequently asked questions about Hirth engines are: how they are able to produce superior performance at lower RPM than other two-cycle engines, and how the 1000 hr rated T.B.O. is possible in a two-cycle.
Hirth has redesigned the porting and the combustion chambers on their aircraft engine line to produce a higher peak hp and torque at lower RPM. Please understand this, not the peak hp and torque output possible overall, but rather the best output possible at a more usable RPM.
Midrange throttle control and fuel use are also improved as a result. Porting and combustion chamber design are very important to "tuning" a 2-stroke engine for the application in which it will be used. This line of Hirth engines have been "tuned" for flight. So, now the RPMs are down, but the good engineering doesn't stop there.
Hirth uses two substantial ball bearings on the Power Takeoff (P.T.O.) end of the crankshaft. High strength chromemoly steel crankshafts are used instead of the softer carbon steel cranks. All engines come standard with special hypereutectic alloy pistons and Nikasil cylinders.
Let's talk about cylinders
Most aircraft engines on the market today are built with steel sleeve cylinders. Although steel sleeves are less expensive than Nikasil, steel cannot dissipate heat as efficiently as aluminum and expands at a slower rate. As the heat in a steel sleeve cylinder engine increases the piston expands faster than the cylinder wall, steadily decreasing the piston clearance.
To compensate for this, engines utilizing steel sleeve cylinders, must run lower CHT and EGT temperatures. Hirth cylinders are made of aluminum alloy; there are no sleeves. The cylinder walls have been treated with the patented Nikasil process. Nikasil coated cylinders have a hardened surface that cannot peel and is more wear resistant than steel sleeves.
Because the cylinders are still an aluminum alloy, their expansion properties as well as their excellent thermal conductivity are virtually unchanged. This design allows heat to be dissipated quickly and efficiently. The piston is also made from an aluminum alloy. The piston alloy is slightly different and expands slightly less than the Nikasil cylinder. This combination of cylinder treatment and matched cylinder and piston materials creates an extremely seize resistant environment. This is also why Hirth engines can handle cylinder head temperatures of over 600 degrees F. without failure. Although the Nikasil process is very expensive, the resulting increase in the engines life span, performance, and reliability more than offsets the cost.
Philosophy
Keep it simple (K.I.S.) is the rule at Hirth. If it isn't there, it can't break. Hirth does not use performance enhancers such as Dyke rings or rotary valves. These are all mechanical devices and if they fail you are coming down. They all require additional maintenance and add to your preflight list. If Hirth ever does offer such technologies it will be because the benefits far outweigh the costs.
Hirth has designed an entire line of aircraft engines from 15 to 110hp. All engines include the following as standard equipment: Carburetor(s), Air filter(s), Spark plugs, Starter relay, Regulator/Rectifier, Fuel Pump, Nikasil cylinders, Chromemoly steel crankshafts, Dual oversized bearings on P.T.O. side, Hyper-Eutectic pistons, Complete exhaust system and Dual CDI ignition with electronic advance. (F36 15hp engine only available with single CDI)
All standard equipment is included in both the list price and total weight.
Reduction drives are optional.
Hirth G-50 Gear Box is: available in 2.16, 2.29, 2.59, 3.16 and 3.65 to 1 Ratios and uses an elastometric dampener between the engine and drive. G-50 is used on 2702, 2703, 2704, 2706, 3202, 3203 and 3701 Hirth engines. It weights 19 lbs. Dry.
Hirth G-40 Gear Box available in 2.03, 2.25, 2.64, 2.96 and 3.33 to 1 Ratios. G-40 is used on F-30, F-23 and 3701 engines. It weights 20 lbs.
Poly grooved belt drive available in 1.8, 2.1, 2.5, 2.85 and 3 to 1 ratios. Can be used on all engines up to 50hp. It weihgts approximately 5 lbs depending on ratio.
Recoil start is available on all engines except fan cooled F30's and 3701 engines.
Engines can have both recoil and electric start installed. All engines can be ordered without electric start.
Hirth engines carry a full 1 year warranty (parts and labor) and a rated 1000 hr T.B.O. 1200 hr. TBO on special high torque/low Rpm engines 2702, 3202, 3701-80Hp and F30-80Hp. Hirth engines are engineered and manufactured in Germany.
Crankshafts have a pro-rated 3 year warranty, H series engines used on helicopters have a 1 year warranty on crankshaft and piston siezure is not covered. F36 warranty is 6 months.
The Hirth heritage
Hirth was founded in 1917. They built 4 cycle aircraft engines for the German air force until the end of World War II. After the war they were forced into the ground engine business and eventually developed a line of snowmobile engines in the 60s. Hirth built their last snowmobile engine in 1974. The company was taken over by the Gobler Company and the decision was made to combine the aircraft technology with what was learned in the snowmobile industry to develop 2 cycle engines for use in aircraft. The result is a line of 2 cycle engines that are much more advanced than standard ground engines. In an aircraft this means stronger climb and cruise at lower RPM. It means less noise, vibration, and fuel use. Less likely to seize a piston or break a crankshaft.
Quality Support
While the quality and design of the engine is of course important, after-sale support of the engine is of equal importance. Recreational Power Engineering has developed the most comprehensive support system in the industry. Engines are warranted for a full year plus a 3 year pro-rated crankshaft warranty. Warranty not only covers defective parts but also labor, free tech support, and prepaid return shipping of the engine. These are all unprecedented support features.
NOTE: Hirth engines are manufactured on a limited basis. There can be a 4 to 6 week lead-time on some models. It is best to get your order in well before your kit is complete to avoid waiting on your engine. Prices subject to change without notice. Call or e-mail for current pricing.
What's new?
This page describes/lists new things which are happening, or are soon to be happening with Hirth engines. New stuff that's here and available, stuff that we're pretty sure will be showing up soon and maybe even a few rumors about stuff that we MIGHT someday see! Change in engine line up - 2706 and 2704 engines have now been replaced with the new 3202 55 hp engine and the 3203 65 hp engines. Basically the same as 2704/06 with some improvements. 5% more fuel efficient, cooler EGT and CHT throughout the RPM range and improved torque curve in the midrange. F-33 engine - Change in hp options. Previously sold in the standard 25 hp version or with an optional 30 hp tuned pipe. The tuned version was to expensive and cumbersome to install. Hirth found a new off the shelf exhaust that when combined with a new cylinder design makes 28Hp. This new setup can be sold for the same price as the old 25 hp version and is much easier to install. 28 hp is now the only option we offer.
Electronic fuel injection Ð Option is Available on F23, F30, 3701, F30ES, 2704/3202 and 2706/3203 engines.
Now Available
3701 - Now available with carburetors at substantially less cost than fuel injection version. F-23 two cylinder opposed engine is back in production. New F-23 is 50 hp and has a new twin exhaust system. Twin float carbs are still standard or optional twin diaphragm carbs or, electronic fuel injection can be used. Optional manual fuel enrichment control for fuel injection. Rubber air guide inserts that seal off the spark plug holes in air guide on 2706 and 2704 engines. Lowers CHT 20 to 30 degrees F. New gear ratio (3.33:1) for G-40 gearbox. Electric start for F33 and F36 engines. Improved fan belt system for dual fan cooled F30's. New system uses a 2v belt instead of the yellow flat belt. Upgrade kits available for older F30's. Optional oil injection for 3202, 3203, 3701, 3503, and F-23 engines. New H-30 engine. Special helicopter version of 4 cylinder F30 Ð105 hp. New H-32 engine. Special helicopter 2 cylinder engine Ð60 hp. New H-37 engine. Special helicopter 3 cylinder water cooled engine Ð90 hp.
Soon Available
3701- 3 cylinder water cooled engine in 80Hp. high torque/low RPM version Can be fitted with either the G-50 gearbox or G-40. Clutch option for 3701 only available with G-40 gearbox.
