THE NEW WORLD’S AIR RECORD.
ON April 10th the culmination of much research work on the part of the Italian High Speed Flight received its reward when Warrant Officer Age lb set up a new world’s air speed record at 423.77 m.p.h. An average of four runs of the measured course was taken, the fastest being at 430 m.p.h. Agello’s machine was a MacchiCastoldi 72, equipped with a Fiat A.S.G engine of 2,800 h.p. The new record beats the previous figure attained by Flight Lieutenant Stainforth, of 407.5 m.p.h.
Some notes on the Fiat engine used in the record will not be out of place.
The engine to be fitted to the seaplane which would attack the world speed record had to fulfil several qualifications. It had to deliver considerably over 2,000 h.p. ; it had to maintain as small a frontal area as possible and it naturally had to be a logical development of existing proved types. To meet all these requirements, an engine of an entirely new design, but based on previous types, as far as the details are concerned, was evolved. This engine has 24 cylinders in two rows forming a 60°
” Vee ” and a total capacity of over 50 litres. The cylinders are divided into two groups of 12 placed one in front of the other, the groups being mechanically independent. Each of the two groups has its own crankshaft but one single crankcase is used for the whole 24 cylinders. The crankshafts which rotate in opposite directions are individually coupled in the centre of the crankcase by spur-gear reducing units driving two airscrew shafts, rotating in opposite directions, one running within the other through the ” Vee ” of the front 12 cylinder unit to the front of the engine where the two airscrews are situated, close together, one behind the other. These propellors revolve at the same speed. This arrangement of the crankshafts and propellors is the only one which eliminates, at any speed,
• reaction couple of the engine upon the plane and affords very great advantages, not only as regards speed, but especially. in the matter of stability in flight and in taking off. Finally, the air stream distorted by the first propellor is corrected by the second one and does not, therefore, carry the exhaust gasses
to the pilot, avoiding thus a very serious inconvenience usual in such high speed racing sea planes.
Each pair of 12 cylinders has its own cam shafts, water pump and pair of magnetos, but only one induction system is used. This comprises an eight-jet carburettor mounted on a centrifugal supercharger situated at the rear of the entire engine unit and driven by the rear motor group through a progressive automatic clutch coupling. The main induction pipe is carried along the top of the engine between the two Vee ” groups and feeds by branches individual pairs of cylinders.
There are two overhead camshafts per motor group driven by skew gear from the crankshaft, the drives being situate in the centre of the main engine unit. Four valves and two plugs are used per cylinder.
The two magnetos for the forward group are mounted above the airscrew shafts and below the supercharger for the rear group.
The engine devlops 2,900 h.p. at 3,200 r.p.m. the weight of the engine being 2,045 lbs. giving a weight per b.h.p. of 0.706 lbs.