A test facility to test a component of a gas turbine engine, the test facility comprising: a storage reservoir for storing compressed air; at least one heat exchanger and at least one combustor; characterised in that: the storage reservoir is capable of storing enough compressed air to test a combustor of a large frame heavy duty industrial gas turbine engine for at least one hour of continuous normal operation; a first heat exchanger is provided with a first fluid flow passage connected to the storage reservoir and a second fluid flow passage, the compressed air flowing within the first fluid flow passage of the first heat exchanger; a first combustor is provided connected to the second fluid flow passage of the first heat exchanger, the first combustor producing a hot gas stream, the hot gas stream flowing within the second fluid flow passage of the first heat exchanger; a second heat exchanger is provided with a first fluid flow passage connected to the first fluid flow passage of the first heat exchanger and a second fluid flow passage connected to the second fluid passage of the first heat exchanger, the compressed air flowing within the first fluid flow passage of the second heat exchanger; a second combustor is connected to the second fluid flow passage of the second heat exchanger, the second combustor producing a hot gas stream, the hot gas stream flowing within the second fluid flow passage of the second heat exchanger; a third heat exchanger is provided with a first fluid flow passage connected to the first fluid flow passage of the second heat exchanger and a second fluid flow passage connected to the second fluid passage of the second heat exchanger, the compressed air flowing within the first fluid flow passage of the third heat exchanger; a third combustor is connected to the second fluid flow passage of the third heat exchanger, the third combustor producing a hot gas stream, the hot gas stream flowing within the second fluid flow passage of the third heat exchanger; and a test article is connected to the first fluid flow passage of the first heat exchanger, the test article being a component of a gas turbine engine, and the compressed air from the storage reservoir passes through the first fluid flow passage of the first, second and third heat exchangers (23, 24, 25) and is preheated from the hot gas stream passing through the second fluid flow passage of the first, second and third heat exchangers (23, 24, 25), and the preheated compressed air from the first fluid flow passage of the first, second and third heat exchangers (23, 24, 25) passes into the test article for testing, the preheated compressed air being non-vitiated compressed air. the storage reservoir is capable of storing enough compressed air to test a combustor of a large frame heavy duty industrial gas turbine engine for at least one hour of continuous normal operation; a first heat exchanger is provided with a first fluid flow passage connected to the storage reservoir and a second fluid flow passage, the compressed air flowing within the first fluid flow passage of the first heat exchanger; a first combustor is provided connected to the second fluid flow passage of the first heat exchanger, the first combustor producing a hot gas stream, the hot gas stream flowing within the second fluid flow passage of the first heat exchanger; a second heat exchanger is provided with a first fluid flow passage connected to the first fluid flow passage of the first heat exchanger and a second fluid flow passage connected to the second fluid passage of the first heat exchanger, the compressed air flowing within the first fluid flow passage of the second heat exchanger; a second combustor is connected to the second fluid flow passage of the second heat exchanger, the second combustor producing a hot gas stream, the hot gas stream flowing within the second fluid flow passage of the second heat exchanger; a third heat exchanger is provided with a first fluid flow passage connected to the first fluid flow passage of the second heat exchanger and a second fluid flow passage connected to the second fluid passage of the second heat exchanger, the compressed air flowing within the first fluid flow passage of the third heat exchanger; a third combustor is connected to the second fluid flow passage of the third heat exchanger, the third combustor producing a hot gas stream, the hot gas stream flowing within the second fluid flow passage of the third heat exchanger; and a test article is connected to the first fluid flow passage of the first heat exchanger, the test article being a component of a gas turbine engine, and the compressed air from the storage reservoir passes through the first fluid flow passage of the first, second and third heat exchangers (23, 24, 25) and is preheated from the hot gas stream passing through the second fluid flow passage of the first, second and third heat exchangers (23, 24, 25), and the preheated compressed air from the first fluid flow passage of the first, second and third heat exchangers (23, 24, 25) passes into the test article for testing, the preheated compressed air being non-vitiated compressed air.