There are 3 Harvards at Goodwood that we know about but there could be others. The Harvard was an American design, known in that country as the AT-6 Texan. A total of 3350 were produced in Canada, more than any other type. Beginning in 1940, 2800 were built by Noorduyn in Montreal and during the 1950's another 550 were constructed by Canadian Car and Foundry in Thunder Bay. The North American Aviation T-6 Texan was an American single-engined Trainer Aircraft used to train pilots of the United States, Royal Air Force, and other air forces of the British Commonwealth during World War II. The T-6 is known by a variety of designations depending on the model and operating air force. The distinctive loud snarl of the Harvard is produce by its 600 horsepower Pratt & Whitney engine together with its nine foot propeller which, when in fine pitch at high rpm, approaches sonic speeds.
There is no doubt that these Harvards are VERY NOISY and the din they create has been the subject of numerous environmental complaints to Chichester District Council. Noise generated by aircraft propellers and engines can propagate into the community around the airfield causing annoyance and discomfort to residents. There is no doubt that Harvards are totally unsuited for use in close proximity to housing estates. The owners of these aircraft seem totally unconcerned about the annoying racket these things produce. For aircraft details and specifications click HERE.
The distinctive loud snarl of the Harvard is produce by its 600 horsepower Pratt & Whitney engine together with its nine foot 2-blade propeller which, when in fine pitch at high rpm, approaches transonic speeds. The speed of both the prop and engine is 2250rpm. It is a direct drive transmission so with no reduction gear and a direct drive the propeller enters the transonic range making the distinct rasping noise of the T6 Harvard. It has the direct drive because it was the cheaper option at the time for a training aircraft. The pitch on the Hamilton 12D40 is adjustable. The greater the number of propeller blades the less is the noise produced.
A fine pitch propeller has a low blade angle and will take a relatively 'small' bite of the air at each rotation. It requires relatively low power to rotate, allowing high propeller speed to be quickly developed, but achieving only limited airspeed. (eg = low gear). A coarse pitch propeller has a high blade angle trying to advance a longer distance through the air with each rotation, taking a big 'bite' of the air. It requires greater power to rotate, limiting the propeller speed that can be developed, but achieving high airspeeds. (eg = high gear). Fine pitch allows the engine to reach maximum speed and hence maximum power at low air speeds, vital for take-off, climb, and for a go-around on landing. The coarse pitch allows the desired aircraft speed to be maintained with a lower throttle setting and slower propeller speed, so maintaining efficiency and improving range. Coarse pitch will ensure the engine does not over rev. while the propeller absorbs high power, producing a higher top speed. A fine pitch propeller has limited airspeed. However it's the matching of a propeller (and it's pitch) to an engine's abilities (RPMs & power band) that achieves the best speed. Use of use a coarser pitch to gain more speed would load the engine, reducing RPMs and drop below the "power band" of that engine thus resulting in less power and less overall speed. For fuel economy lower RPMs are required so the propeller is adjusted to a coarser pitch for cruise or economy flight.
Now this is what is happening when a Harvard takes off from Goodwood. Take-off is maximum RPM and power (hence maximum noise level), the propeller is on finest pitch but climb is slow and that's the reason why these Harvards are flying quite low over adjacent housing. At the city boundary, the pilot switches to maximum propeller pitch and the tone of the engine noise does audibly drop as the engine RPM drops but it's still an excruciatingly offensive noisy disturbance.