For aircraft engines

84.07 - Spark-ignition reciprocating or rotary internal combustion piston engines (+). 8407.10 - Aircraft engines - Marine propulsion engines : 8407.2 1 - - Outboard motors 8407.29 - - Other - Reciprocating piston engines of a kind used for the propulsion of vehicles of Chapter 87 : 8407.31 - - Of a cylinder capacity not exceeding 50 cc 8407.32 - - Of a cylinder capacity exceeding 50 cc but not exceeding 250 cc 8407.33 - - Of a cylinder capacity exceeding 250 cc but not exceeding 1,000 cc 8407.34 - - Of a cylinder capacity exceeding 1,000 cc 8407.90 - Other engines This heading covers spark-ignition reci rocating internal combustion iston engines and rotary internal combustion iston en ines ( ankel engines having a trilo a1 disc type " ptston"), other than those of hapter 9%It includes such engines for motor vehicles. E 7R g These engines generally have the following elements : cylinder, piston, connecting-rod, crank shaft, flywheel, inlet and exhaust valves, etc. They make use of the expansion force of a charge of inflammable gas or vapour burned inside a cylinder. The characteristic feature of these engines is that the are equipped with sparking plugs fitted Z into the cylinder head and with electrical devices (suc as magnetos, coils and contact breakers) synchronised with the motor, for supplying high tension current. In the more-common types the fuel and air are mixed (e.g., in a carburettor) before induction into the cylinder by the suction stroke of the piston, but in some cases e.g., certain aircraft engines and motor car engines) the fuel is introduced into the cylinder ead directly by an injector. The most usual fuel is petrol, but others include kerosene, alcohol, hydrogen, coal gas, methane, etc. Gas engines are most frequently fed by producer gas enerators which are sometimes integral with the engine, but are more often independent. In t%e latter case the generators are always classified in heading 84.05. These engines may have one or several cylinders. In the latter case the connecting-rods are coupled to a single crank shaft, and the cylinders, fed separately, may be arranged m various ways, e.g., in a vertical line (upri t or inverted), in two symmetrical obliquely opposed rows (V-engines), horizontally oppose on opposite sides on the crank shaft or, for certain aircraft engines, radially. The rotary piston engine (Wankel engine) operates on the same pnnci le as the conventional plston engines described above. However, instead of a c r S : d turne by an oscillatin piston and connecting rod, the rotary iston engine has a trilobal disc (" piston ") in a special y shaped housing (epitrochoid), which d?rectly rotates a driving shaft. p f f The " piston " divides the housing (combustion chamber) into several compartments and each complete rotation corresponds for each lobe to a four-stroke cycle. These engines may have one or more housings with " pistons ". The engines of this heading are suitable for very many uses, e-g., in agricultural machines; for driving electric generators, pum s or compressors; for propelling aircraft, motorcars, motorcycles, autocycles, tractors or oats. g The engines of this heading may be e ipped with he1 injection pumps, ignition parts, fbel or oil reservoirs, water radiators, oil coo ers, water, oil or fuel pumps, blowers, air or oil filters, clutches or power drives, or starting devices (electric or other). Change speed gears may also be fitted. The engines may also be equlpped with a flexible shaft. y The heading includes " outboard motors " for the propulsion of small boats, consisting of a motor of this heading, a propeller and a steering device, the whole constitutin a single, indivisible unit. These motors, designed to be attached to the outside of the hull of e boat, are detachable, that is they can be attached and removed easily and are adjustable, the unit turning on the oint of attachment. However, motors designed to be fixed to the inside of the hull at the rear otule boat combined with a block holdin a steering ropeller fixed to the exterior of the boat at the corresponding place are not regarde as outboar motors. 6i f It also covers mobile motors consisting of engines mounted on a wheeled chassis or on runners, including those with drivin mechanisms permitting their self-propulsion to a certain extent (but not constituting vehicles o Chapter 87). ? The heading excludes variable compression motors of the spark-ignition internal combustion piston en ine type designed specially for determination of the octane and cetane vaIue of motor hels (ciapter 90). PARTS general provisions regardin the classification of parts (see the General Note to Section XVI), parts o the engines of this heading are classified in f