How many hours did a Vulcan fly with Conway engines during testing?

The XA902 was a production Vulcan B.1 withdrawn from RAF service after a landing accident in 1958. Rather than being written off, it was rebuilt and given a new job: replacing the first prototype, VX770, as the testbed for the Rolls-Royce Conway engine, after VX770 crashed in September 1958.

For that task, XA902 was fitted with four Conway RCo.11 engines. The Spanish Wikipedia records that it completed 1,000 flight hours with those engines. The Conway was of particular interest: it is considered the world's first turbofan. VX770 had already flown with the earlier RCo.7 version from 1957, and XA902 continued that work with the RCo.11 variant.

Once the Conway campaign ended, XA902 was used to develop a new turbofan, the Rolls-Royce Spey. The two inboard Conways were replaced with two Speys, and the aircraft first flew in that mixed configuration on 12 October 1961.

XA902 was not the only Vulcan devoted to engine work. The first production B.1, XA889, was used to flight-certify the Olympus 102 and 104 versions, and XA903 later tested the Olympus 593 used by Concorde and the RB.199 used by the Panavia Tornado.

The aircraft came from the British Ministry of Supply's B.35/46 specification. The first prototype flew on 30 August 1952, and the RAF received its first Vulcan B.1 in September 1956. Deliveries of the much-improved Vulcan B.2 began in 1960, and the last example reached the RAF in January 1965.