The Hirth 3502 and 3503 are a family of liquid-cooled, in-line twin-cylinder,

two-stroke A two-stroke (or two-stroke cycle) engine is a type of internal combustion engine that completes a power cycle with two strokes (up and down movements) of the piston during one power cycle, this power cycle being completed in one revolution of ...

, carbureted aircraft engines, with optional

fuel injection Fuel injection is the introduction of fuel in an internal combustion engine, most commonly automotive engines, by the means of an injector. This article focuses on fuel injection in reciprocating piston and Wankel rotary engines. All com ...

, designed for use on

ultralight aircraft Ultralight aviation (called microlight aviation in some countries) is the flying of lightweight, 1- or 2-seat fixed-wing aircraft. Some countries differentiate between weight-shift control and Aircraft flight control system, conventional three-a ...

and small homebuilts. It is manufactured by

Hirth Hirth Engines GmbH is an engine manufacturer based in Benningen, Germany. It is currently a part of the UMS Aero Group. Hirth began manufacturing aero engines in the 1920s, was taken over by Heinkel in WWII to develop the Heinkel-Hirth jet en ...

of Germany.

Development

The engines were developed as competitors to the

Rotax 582 The Rotax 582 is a two-stroke, two-cylinder, rotary intake valve, oil-in-fuel or oil injection pump, liquid-cooled, gear reduction-drive aircraft engine manufactured by BRP-Rotax GmbH & Co. KG. It is for use in non-certified aircraft operating ...

with an identical mounting bolt pattern to the 582, allowing either to be a drop-in replacement. The engines are similar to the

Rotax Rotax is the brand name for a range of internal combustion engines developed and manufactured by the Austrian company BRP-Rotax GmbH & Co KG (until 2016 BRP-Powertrain GmbH & Co. KG), in turn owned by the Canadian Bombardier Recreational Produc ...

powerplant in being liquid-cooled, two-cylinder in-line engines, with dual

capacitor discharge ignition Capacitor discharge ignition (CDI) or thyristor ignition is a type of automotive electronic ignition system which is widely used in outboard motors, motorcycles, lawn mowers, chainsaws, small engines, turbine-powered aircraft, and some cars. It ...

. The 3502 was developed from the 3503 as a de-rated version and produces , in comparison to the 3503's . Both engines have the same bore, stroke and compression ratio as the three-cylinder in-line liquid-cooled

Hirth 3701 The Hirth 3701 is an in-line three-cylinder, two-stroke, carburetted aircraft engine, with optional fuel injection, designed for use on ultralight aircraft and small homebuilts. It is manufactured by Hirth of Germany. Development The 3701 ...

and the bore, stroke, compression ratio and displacement of the twin-cylinder

Hirth 2704 The Hirth 2704 and 2706 are a family of in-line twin cylinder, two stroke, carburetted aircraft engines, with optional fuel injection, designed for use on ultralight aircraft and especially two seat ultralight trainers, single seat gyrocopte ...

and

Hirth 2706 The Hirth 2704 and 2706 are a family of in-line twin cylinder, two stroke, carburetted aircraft engines, with optional fuel injection, designed for use on ultralight aircraft and especially two seat ultralight trainers, single seat gyrocopte ...

. Both the 3502 and 3503 are equipped with dual Bing 34 mm slide carburetors or optionally electronic fuel injection. The cylinder walls are electrochemically coated with

Nikasil Nikasil is a trademarked electrodeposited lipophilic nickel matrix silicon carbide coating for engine components, mainly piston engine cylinder liners. Development Nikasil was introduced by Mahle in 1967, and initially developed to allow Wank ...

and the crankshaft is forged from

4130 steel 41xx steel is a family of SAE steel grades, as specified by the Society of Automotive Engineers (SAE). Alloying elements include chromium and molybdenum, and as a result these materials are often informally referred to as chromoly steel (common va ...

. Standard starting is

recoil start Rope start (also called pull start or ''rewind start'') is a method of starting an internal combustion engine, usually on small machines, such as lawn mowers, chainsaws, ultralight aircraft, small outboard motors and portable engine-generators. A ...

with electric start as an option. The reduction drive system available is the G-50 gearbox, with reduction ratios of 2.16:1, 2.29:1, 2.59:1, 3.16:1, or 3.65:1. The engines run on a 50:1 pre-mix of unleaded 93 octane auto fuel and oil, or optionally oil injection.

Variants

;3502 :Twin-cylinder in-line, liquid-cooled, two-stroke aircraft engine with dual Bing 34 mm slide carburetors or fuel injection. Produces at 5000 rpm and has a factory rated TBO of 1200 hours. In production since April 2008. ;3503 :Twin-cylinder in-line, liquid-cooled, two-stroke aircraft engine with dual Bing 34 mm slide carburetors or fuel injection. Produces at 6500 rpm and has a factory rated TBO of 1000 hours. In production.

Applications

;3502 * CGS Hawk Arrow II *

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powered parachute A powered parachute, often abbreviated PPC, and also called a motorized parachute or paraplane, is a type of aircraft that consists of a parafoil with a motor and wheels. The FAA defines a powered parachute as ''a powered aircraft a flexible or ...

Paraski Para-Ski International was a Canadian aircraft manufacturer, based in Mascouche, Quebec. The company specialized in the design and construction of powered parachutes.Cliche, Andre: ''Ultralight Aircraft Shopper's Guide'' 8th Edition, page D-10 ...

- powered parachute ;3503 *

Excalibur Aircraft Excalibur The Excalibur is an American two seats-in-tandem, high wing, pusher configuration ultralight aircraft that is manufactured in kit form for amateur construction, by Excalibur Aircraft of Sebring, Florida. It was introduced in 1993.Cliche, An ...

GyroTec DF02 The GyroTec DF02 is a German autogyro, designed and produced by GyroTec Michael Obermaier of Wörth am Rhein. The DF02 is supplied as complete ready-to-fly-aircraft.Bayerl, Robby; Martin Berkemeier; et al: ''World Directory of Leisure Aviatio ...

Rotortec Cloud Dancer Light The Rotortec Cloud Dancer Light is a German autogyro, designed and produced by Rotortec of Görisried, Allgäu. The aircraft is supplied as a complete ready-to-fly-aircraft.Bayerl, Robby; Martin Berkemeier; et al: ''World Directory of Leisure ...

Summit Steel Breeze The Summit Steel Breeze is an American powered parachute, designed and produced by Summit Aerosports of Yale, Michigan. The aircraft is supplied as a kit for amateur construction or as a complete ready-to-fly aircraft.Bernard, Mary and Suzanne ...

- powered parachute *

Vortech Skylark The Vortech Skylark is an American helicopter produced by Vortech of Fallston, Maryland. The aircraft is supplied in the form of plans for amateur construction. Vortech also supplies rotor blades for the design.Downey, Julia: ''2005 Trikes ...

- helicopter

Specifications (3503)

References

External links

Official 3502 page
{{Hirth aeroengines Hirth aircraft engines Two-stroke aircraft piston engines