Mosquito air brake

I couldn’t find the information on the talk we had but I did have a browse through a couple of Mosquito books and this is from de Haviland Mosquito, Martin W. Bowman:
The first version of the segmented Youngman frill airbrake was fitted to W4052, the fighter prototype, when the aircraft was at Salisbury Hall. The ‘frill’ could be opened by a bellows and venturi arrangement to provide rapid deceleration 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.
I thought it might be of interest.

Good question. The information about the air brake and undercarriage came from a talk we had at our club years ago. The chap was an author and had written various magazine articles on the Mosquito but for the life of me I can’t recall his name at the moment. If I get a chance at the weekend I will try to check up on who it was. He had various slides on the air brake being tested and we asked about the effect on air flow over the tail surfaces etc but I don’t think anyone asked about Vle.

ISTR there was a placard by the u/c lever saying that it must be raised by 115 knots. As we needed at least 150 knots to achieve safety speed I don’t think lowering the u/c was a sensible option. Safety speed was the speed necessary for the aircraft to continue safely on one engine. If an engine failed before safety speed was reached the instructions were to put the aircraft down straight ahead, any attempt to turn could be lethal as many crews learnt to their cost.

The u/c was a big drag producer and acceleration was very sluggish to nil once airborne and I doubt safety speed could be attained if the gear was not retracted. Too long ago now to remember all the details but we tried all sorts of antics.

An air brake would have been very useful to knock off excess speed in the final stages of an interception. When we were upgraded to the Meteor, which had such an animal, it made life much easier

I wonder what Vle for the Mosquito is?

I’d be quite amazed if it was at interception speeds.

Moggy

I was told years ago that the system worked but during testing it was found that the same effect could be had by lowering the undercarriage so the air brake was idea was not persued.

The problem with night interception is you have to catch the bogey, so you will need a speed advantage and the less time you spend stalking it, the less likely you are to be spotted.

But a slippery aircraft like the Mosquito has great problems shedding that speed. Chop the throttles and the aircraft will not slow down abruptly.

Hence the thought of air brakes.

The Maverick ‘I’m gonna hit the brakes and he’ll fly right by’ tactic owes more to Hollywood scriptwriters than 1940 RAF night fighting SOP.

Moggy

I read about it many years ago and seem to recall that the annular airbrake wasn’t as effective as hoped and produced too much turbulence over the tail-surfaces.

Closing fast on a target and it makes evasive turns – easy way to shed speed and turn with it.