3 or 4 blade propellers?
- rcristi2271
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3 or 4 blade propellers?
Which are the main differences between these types of propellers? I always asked myself why Germans used almost always 3 blade propellers (just one exception: Heinkel He 177) compared with Allies who widely used 4 blade propellers.
Best regards
Chris
Best regards
Chris
It`s the surface square meters you need for the propeler to be eficient at a certain power of the engine.
You can increase the diameter or the number of blades.
Too big diameter, the propeler requests high undercarriage not to touch the ground, and the speed at the margin of the blade becomes supersonic(destroys airflow, vibrations). Americans had engines more powerful at last series of proprller fighters than germans (but germans had jet fighters ). Its the same with elicopters today, from two blades (Cobra) to seven (russianMi-26)
You can increase the diameter or the number of blades.
Too big diameter, the propeler requests high undercarriage not to touch the ground, and the speed at the margin of the blade becomes supersonic(destroys airflow, vibrations). Americans had engines more powerful at last series of proprller fighters than germans (but germans had jet fighters ). Its the same with elicopters today, from two blades (Cobra) to seven (russianMi-26)
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- Cantankerous
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Re: 3 or 4 blade propellers?
Even though this thread is almost 20 years old and it may therefore be tempting not to post here, I should note that the Junkers Ju 288 prototype tactical bomber had Junkers Jumo 222 engines driving four-bladed propellers, and that the one Heinkel He 177B prototype was used as a testbed for the Jumo 222 because Heinkel floated the option of using the Jumo 222 for the Heinkel He 277 long-range maritime strike aircraft. The Jumo 222, however, was a technological failure due to cooling problems.
- ShindenKai
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Re: 3 or 4 blade propellers?
Its not just the efficiency of the propellers themselves but the constant-speed/prop pitch control units. There just wasn’t physically enough space to have the prop pitch controls AND a cannon firing through the prop hub.
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Re: 3 or 4 blade propellers?
https://www.youtube.com/watch?v=EKR-Obdq8_E
Greg did a really neato video on the topic, long video, but he's a great youtuber.
Greg did a really neato video on the topic, long video, but he's a great youtuber.
- ShindenKai
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Re: 3 or 4 blade propellers?
Yes, Greg does an excellent job!ThatZenoGuy wrote: ↑19 Jun 2022, 17:48https://www.youtube.com/watch?v=EKR-Obdq8_E
Greg did a really neato video on the topic, long video, but he's a great youtuber.