The Zoche aero-diesels are a trio of German prototype Diesel radial aero-engines intended for light aircraft. The Zoche ZO range comprises three radial engines, namely: the ZO 01A, a “cross-4”; the ZO 02A, a twin-row “cross-8”; and the ZO 03A, a V-twin. Power outputs are 150 hp (112 kW), 300 hp (224 kW) and 70 hp (52 kW) (respectively).

The founder of the project is Michael Zoche, who claimed that the ZO engines will have the following advantages: they will be lightweight, compact and perfectly smooth; low fuel consumption; high power-to-weight ratio; the lubrication system will allow aerobatics; diesel fuel injection, so no carburetor icing; direct driven generator, so no drive-belts; good reliability through a low part count and absence of poppet valves; pneumatic starting obviates both electric starter motor and heavy starter battery; complete absence of rubber hoses; cheaper parts through modularity; reduced fire risk compared to avgas; good power output, even at altitudes up to 9,000 feet (3,000 m). The engines will also have the “classic” appearance that is suitable for some aircraft types.

The AOPA website explains the “cross-4” ZO 01A as follows: “The radial design was chosen for its ability to be effectively aircooled and 100% balanced at all rpm with a simple counterweight system. All four connecting rods are attached to a single crankshaft throw. This prevents any crankshaft twisting, which is hard to balance out in opposed-configuration engines. Zoche engines use a pneumatic starting system that does away with the need for a heavy-duty starter and battery system”.

Zoche ZO engines are modular and are all direct-drive, air-cooled, radial two-stroke Diesels with up to four cylinders per row. They feature two-stage charging (turbocharger and supercharger), direct fuel-injection and intercooling. Propeller rotation is clockwise (viewed from the cockpit). Engine weights (below) include: starter-generator, hydraulic propeller-governor, turbocharger and supercharger, and oil- and fuel-filters. Engine mountings are attached to the cylinder heads. Engines are to be certified to JAR-E and FAR 33, and a TBO of 2,000 hours is anticipated.

A Zoche engine has run effectively in wind tunnel tests, but Zoche seem barely any closer to production than they were a decade earlier. The Zoche engine gestation period has lasted some 20 years; and whether or when production may start is unknown.

The Lambert Mission 212, a kit-build 4-seat aircraft from Belgium that was nearing completion of pre-production testing, was initially designed around the Zoche ZO1A motor; but, with the non-appearance of the Zoche, Lambert have been obliged to select other engines, the DeltaHawk® DH200A4 (or DH180A4), or the XP-360 engine.

Variants:
ZO 01A
Single-row cross-4, 2,660 cc (162 cu in), (max) 150 hp (112 kW) @ 2500 rpm, 84 kg (185 lb)), fuel consumption 21 litres/h @ 75% power.

ZO 02A
Double-row cross-8, 5,330 cc (325 cu in), (max) 300 hp (224 kW) @ 2500 rpm, 123 kg (271 lb)), fuel consumption 42 litres/h @ 75% power.

ZO 03A
V-twin, 1,330 cc (81 cu in), (max) 70 hp (52 kW) @ 2500 rpm, 55 kg (121 lb)), fuel consumption 10 litres/h @ 75% power.