Production
The
Hawker Typhoon was the first operational Sabre powered aircraft, entering service with the RAF in mid-1941. Problems with both the Sabre engine and the airframe nearly led to the Typhoon's premature withdrawal from service.
Problems started to arise as soon as production started in volume. Up to then the prototype engines had been hand-assembled by Napier craftsmen and it proved to be difficult to adapt it to assembly line production techniques. In particular, the sleeves often failed, leading to seized cylinders.
[2] After testing some 18 different materials and manufacturing techniques a process of
nitriding and
lapping the sleeves helped resolve the problem.
[2]
Quality control also proved to be a serious problem. Engines were often delivered with improperly cleaned castings, broken piston rings, and machine cuttings left inside the engine.
[3] Mechanics were constantly overworked trying to keep Sabres running, and during cold weather they had to run them every two hours during the night so that the engine oil would not congeal and prevent the engine starting the next day.
[nb 2] These problems took too long to straighten out, and for many the engine started to attain a bad reputation. To make matters worse, mechanics and pilots unfamiliar with the very different nature of this engine tended to blame the Sabre for problems which were caused by incorrect handling. This was all exacerbated by the representatives of the competing Rolls-Royce company, who had their own agenda. Rolls-Royce eventually built their own interpretation called the
Eagle.
Napier did not seem to be particularly interested in solving these sorts of problems, however, and instead continued to tinker with the design for better performance. In 1942 they started a series of projects to improve altitude performance with the addition of a three-speed, two-stage
supercharger, but at this point the basic engine was still not running reliably. In December 1942 the company was purchased by
English Electric, who immediately ended the supercharger project and focused the entire company on the production problems. The situation quickly improved.
By 1944, the Sabre V was delivering 2,400 hp (1,800 kW) consistently, and the reputation of the engine started to improve. This was the last version to see service, however, seeing service on the
Hawker Typhoon and its derivative, the
Tempest. Without the advanced supercharger, the engine's performance over 20,000 ft (6,100 m) fell off rapidly, and pilots flying Sabre-powered aircraft were generally instructed to enter fights only below this altitude. At low altitude, both planes were formidable, the Typhoon easily outpacing its German counterpart, the
Focke-Wulf Fw 190. With the destruction of the
Luftwaffe during early 1944, Typhoons were increasingly used as
fighter-bombers, notably by the RAF's
Second TAF.
Development continued, and the later Sabre VII delivered 3,500 hp (2,600 kW) with a new supercharger; the final test examples delivered 5,500 hp (4.100 kW) at 45 lb/sq in boost. By the end of the war there were several engines of the same power class; the
Pratt & Whitney R-4360 Wasp Major was producing about 3,055 hp (2,280 kW), but required almost twice the displacement to do so, 4,360 in³ (71 L)
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