Page 56-57, Mosquito, C. Martin Sharp & Michael J. F. Bowyer:The first turret fighter W4053 was flown out of Salisbury Hall field on Sunday, 14 September, and shed part of it's turret on the way to Hatfield. George Gibbons flew the second, W4073, out of the same field 5 December, with a mock-up turret. But soon this was removed and faired over at Boscombe Down. The turret tests were over. Having dual control W4073 was taken to 157 Squadron, Castle Camps, by Wg. Cdr. Slade on 17 January, 1942, to become a trainer. The turret fighter was out, primarily because there could be no doubt of the effectiveness of fixed guns-given deceleration.The first hopes for deceleration, when coming up behind an enemy aircraft, were pinning to the Youngman frill brake. This had been tried on Spitfires. It encircled the rear fuselage like a cake frill and was operated by a bellows and venturi. Between 1 January and 1 August, 1942, the brake was tried in many forms, without gaps, with gaps, with chords of 10, 13 and 16 inches, but compared to lowering the undercarriage (despite door problems at high speed) it was not a worthwhile complication.
Page 20, De Haviland Mosquito, Martin W. Bowman, italics mine:(Below)Below is a photo of a Mosquito with a Youngman frill with gaps.The first version of the segmented Youngman frill airbrake as fitted to W4052, the fighter prototype, when the aircraft was at Salisbury Hall. The 'frill' could be could be opened by a bellows and venturi arrangement to provide rapid decleration during interceptions and was tested in a number of different forms between January-August 1942 but the idea was shelved when it was found that lowering the undercarriage in flight had the same effect.
Originally posted by Pyro Pilot's handbook for the FB6 gives a maximum gear down speed of 155 knots.
