When did the remove the two bladed fixed pitch wooden propellers of the Spitfire Mk.I? If im correct they replaced them with 2 pitch three bladed ones and then eventually with 3 bladed variable ones... Anyone got the dates at when they started using/replacing them? What were the differences (performance wise etc.)?
Variable props give you better accelleration (generally speaking) and if the engine conks out in flight they can be feathered (hopefully). Something about the bite the blde gets in the air or something if I remember right (which seems to be a recent short coming.......)
Did the early 2 and 3 bladed props have inflight variable pitch control or was it set before flight (i've read about that somewhere sometime ago...can't reemember if it was on early spits though).
The two bladed wooden propeller was only fitted to the first 78 production Spitfire Mk I's. The switch to a 2 pitch three blade propeller, reduced the take off run by 30 per cent and increased the speed of the fastest climb from 175 mph to 192 mph. By the time of the Spifires first combat all of the 78 early production aircraft had been re-fitted with the 2 pitch 3 blade propeller The Spitfire started to receive the De Havilland constant speed variable propeller in June 1940, and by August 1,050 had been retro-fitted in the field.
The 2 blade propeller had no variable control, while the early 3 bladed propellers had two different settings, which were controlled by the pilot.
differences if you consider a prop as the driveline and tires on a car perhaps it gets simpler. a fixed 2 blade would be a one speed tranny hooked to small narrow tires. works well enought for slow speeds and low HP. a 3 blade fixed prop gives you better tires so you can get hooked up better. a 2 speed prop adds a second gear to either design. a variable prop becomes a 5 speed tranny and allows the engine to function better at a wide range of speed and loads. blade width also improves the grip. the P-47 became a different plane when it got the paddle bladed props simple because then it could get all that hp hooked up instead of wasting it. take a 1000 hp dragster and try running it on street tires and see how slow it runs. then give it back its slicks and watch out. prop design had as much to do with fighter performance as did engines, you have to have both and they better match
Re: differences A single pitch propeller is a compromise between "take off distance" and "speed that is attainable". A more accurate terminology when comparing against cars would be comparing propeller pitchs to car transmission gear: with gear #1 you get on the move far more easily than with gear #5 with a low top end speed and with gear #5 you don't get on the move as easily as the gear #1 but the resulting top end speed is far greater. A single pitch propeller usually was set to #3 gear (to keep the analogy going :] ) while 2 speed propellers had the set for #1 and #5 respectively. At the pinnacle of propeller designs are the constant speed propellers. You could keep the engine running at the most efficient RPM while the propeller pitch would always be optimal for given speed (or more accurately, a constant speed propeller would have an optimal angle that the prop is having to relative wind at all times. The angle is adjusted relative to aircraft speed and propeller blade speed). Late edit: I should have also said that a constant speed propeller doesn't mean that the engine and propeller is having a constant RPM all the time. You obviously don't have to keep the best available power output from an engine when you are doing best economical cruise.
Can anyone tell me If this picture is a prop off of a spitfire if not, does anyone know what it is off of??
Thanks Ace of Spades. This came off a plane my father test flew in the war he was an instructor, Canadian Air Force. The prop was out of balance. So he had it shipped home. Some relatives say he shipped from England and some figured it was off a Spitfire because he did fly them. Apparently the Spitfires first started with 2 blade wooden props then soon changed to 3 blades then even 4???? Thanks again for your input Duncan
I would still say its off a biplane (common as instruction aircraft) it is wooden and is steel reinforced along its leading edge...Not WW2 stuff really. The early spits had two blades but had a dark paint applied. Many commonwealth pilots were trained in Tiger Moths...(Biplane) this is an example of a Tiger Moth Prop Tiger Moths were and still are legendary aircraft (My grandfather learned to fly in a Moth) i'd still love to have that prop of yours...
Thanks for your help. I think you might be right. Now that you mention that I remember my Dad telling stories about Barn storming and even flying under highway power lines in the Tiger Moth. The last picture is almost a perfect match to my prop. Thanks for the pictures Duncan
Your Dad sounds pretty cool... : ) An Australian Tiger Moth... NOTE: Dragger tail...you could plow with this thing. As I said, my Grandfather learned to fly in these...he managed to crash three of them! The last time was hitting those power lines and flipping (all three crashes were at night, they eventually clicked he had night blindness) He said he was lucky he was a short arse...any taller and his head would have been crushed when he flipped. The RAAF offered him a job as a test pilot (flying only during day light hours)...which he took. Canadian Tiger Moth NOTE: Additional cage canopy - An illustration of how cold it must have been up in a Moth in bloody Canada!
