The rate at which parts deteriorate in a gas turbine is unbalanced insofar as the hottest parts need replacing or repairing more often than the cooler-running parts. If the hotter parts can be removed without disturbing the rest of the engine, for example without removing the complete engine from the aircraft, maintenance costs are reduced. It was achieved with the PT6 by having the hottest parts, the gas generator turbine and combustor, at the propeller end. They are removed without disturbing the rest of the engine with its connections to the aircraft. This arrangement was patented by designer Newland, one of the original PT6 team. A similar general arrangement with a free-turbine power take-off at the exhaust end ( the 1,000 shp P.181 engine) had been shown by Armstrong Siddeley Motors at the Farnborough Airshow in 1957.