Monday, 30 July 2012

Vintage aircraft [4]

A few new clips from Youtube.
This is a Bristol Hercules engine from a Handley Page Hastings aircraft. This clip has about the best sound quality of the many clips I have seen of different aircraft engine, it is probably the most true one of the actual sound particularly in low frequency as cheap digital cameras that people often shoot with tend to have poor bass response. In case you wanted to know why it is so noisy… this engine has a cubic capacity of 2370 cubic inches and produces around 2000 horsepower at full power. By comparison a 2 litre car engine has a capacity of 125 cubic inches and produces maybe 70 horsepower. Also there are no mufflers fitted to any of the exhausts. There are 14 cylinders and because the engine is supercharged rather than turbocharged, the exhaust is straight out which means the noise level is quite high for the size of the engine, Hercules engines like Merlins were known for their high noise level and were not popular on passenger aircraft or with people who lived near airports where aircraft fitted with them flew from.
Restoring old aircraft engines and running them at public shows is a popular pastime and as we know the Bristol Freighter at Omaka has had engine restoration to allow the engines to be run and the aircraft taxied at shows within the last three years. The engineer who did the work to get it going also got hold of a spare engine which he mounted onto a trailer in a similar fashion to that shown above.
Here it is running somewhere in Christchurch City in 2011.
This clip shows the running of a Wright R-3350 engine from a B-29 bomber at night. Wright’s engines were not as good as Pratt and Whitney’s. They tended to be lower grade technology and engineering. For example when both manufacturers brought out engines around 1800 cubic inches, P&W made the jump to a two row 14 cylinder engine – Wright simply built another single row 9 cylinder engine which would have been of a larger diameter resulting in increased drag. It wasn’t until the R-2600 that Wrights built their first two row radial engine. The 2600 was the 14 cylinder version of the 3350. The latter was the biggest engine the US had when Boeing set out to put together the B-29 bomber. Wright’s decision initially to use cast fins on the cylinder head (the smaller P&W R-2800 had introduced milled fins because of the need for better cooling) was responsible for the overheating and engine fires that were such a problem when the B-29 first went into service. Although the engine design survived into the 1950s and powered the last of the great propeller airliners, they are still a less reliable engine than the R-2800 which accounts for the fact that more DC-6s are still flying today than DC-7s or Lockheed Constellations. Also Wrights went out of the engine business at the beginning of the jet age whereas Pratt & Whitney are still in business today. Technologically the largest successful radials were those with 18 cylinders. The P&W R-4360 with 28 cylinders in four rows was uneconomical for passenger aircraft operation. Wrights with the R-3350 and Bristol with the Centaurus were right to stay at 18 cylinders, although a 22 cylinder version of the R-3350 was considered. Bristol had planned several series of larger 18 cylinder engines but the Centaurus was the last model to reach production.