Diesel Air Dair 100


The Diesel Air Dair 100 is an opposed-piston aircraft diesel engine, designed and produced by Diesel Air Ltd of Olney, Buckinghamshire for use in airships, home-built kit planes and light aircraft. The prototype was built in the 1990s and exhibited at PFA airshows. Although Diesel Air engines have been fitted to an AT-10 airship and to a Luscombe 8A monoplane, production numbers have been very limited.

Design and development

The Dair 100 engine is a twin-cylinder two-stroke, opposed-piston, displacement, liquid-cooled, diesel engine direct drive design. It produces at 2500 rpm, with a compression ratio of 18:1. The engine has two cylinders and two crankshafts linked to four pistons, the combustion chamber formed between the crowns of the pistons. There are no poppet valves, each cylinder having a ring of ports at each end. In this "one-direction " engine these ports, respectively, admit air and expel exhaust gases. This design eliminates the need for a cylinder head and camshafts. Scavenging is assisted by a centrifugal air pump, the pump also serving to provide a mild supercharging effect. Fitment of an exhaust-driven turbocharger is permissible.
The engine may use either diesel fuel or Jet-A1 kerosene. Jet-A1 is more readily available at airfields, but its reduced lubricity could mean that additional cylinder lubrication may be required. Fuel is directly injected into each cylinder, pressure being supplied by a hydraulically-governed mechanical fuel pump.
Dry sump lubrication is by high pressure pump delivering oil to plain main bearings and con-rod bearings.

Applications