An interesting observation

[rickshaw]

The national preference for the number of propeller blades an aircraft uses.

In the UK, the maximum number appears to have been five.
In the US, the maximum number appears to have been four.  Does anybody know of the US testing/employing five bladed or more propellers?
In Germany, the maximum appears to have been four.
In Japan, the maximum appears to have been five.
In Russia, the maximum appears to have been four.

Now, I wnder why the US and Russia never advanced beyond four blades?   I am aware that they occasionally used contra-rotating propellers.  However in single propeller applications, four appears to have been the maximum.   I wonder why?

[kerick]

Hmmm...... interesting indeed.

Are you thinking commercial, military or civilian? Or all together?
In general aviation the popular choice seems to be three blades. Military, up to recently, definitely four. Commercial four up to recently with the new five, six or more blades.
Perhaps its the same thing that holds up old rickety buildings..........tradition!

[Weaver]

Perhaps in the countries that only got up to four blades, they made an earlier/firmer decision to go straight to contra-props, thus making the step to five blades unnecessary? In the UK at least, there was a time-consuming debate over the relative merits of five-bladed props vs contra-props that led to both being seen.

[rickshaw]

Hmmm...... interesting indeed.

Are you thinking commercial, military or civilian? Or all together?
In general aviation the popular choice seems to be three blades. Military, up to recently, definitely four. Commercial four up to recently with the new five, six or more blades.
Perhaps its the same thing that holds up old rickety buildings..........tradition!

Mmm, OK, perhaps I should have been more specific?  How about World War Two, with piston engines.  OK?

[PR19_Kit]

Hmmm...... interesting indeed.

Are you thinking commercial, military or civilian? Or all together?
In general aviation the popular choice seems to be three blades. Military, up to recently, definitely four. Commercial four up to recently with the new five, six or more blades.
Perhaps its the same thing that holds up old rickety buildings..........tradition!

Mmm, OK, perhaps I should have been more specific?  How about World War Two, with piston engines.  OK?

Doesn't H's point still hold good? Supermarine tried both solutions on the later Spitfires and only seemed to come down on contra-props as the ideal because of the horrendous torque effects from the 5 bladed Griffon engine versions.

[NARSES2]

Well I'll be blowed. I had these very thoughts myself traveling down on the train Monday.

Been reading my mind mate ? 

[Dizzyfugu]

It is a matter of blade area, rotation speed, and other aspects that define the prop design. Japan actually tested six-bladed props in WWII, but they were found to be impractical because the blades' blur was so strong that the pilot would not clearly see anything in front... Not good for a fighter, and landing might have been rather hazardous this way, too. More blades means more complexity, but when you want to transform the engine's power into propulsion and simply cannot increase the prop's diameter (the Spitfire is a good case), the only option is to add a blade or two... With side effects, like torque and drag. It's always a compromise.
And in recent time the number of blades (e. g. on turboprops) increased because the props have to run run slower in order to keep blade tip and frequency noise withing acceptable (legal) limits.

[Lord_Voyager]

Japan was moving towards 6 blades with their Shinden  ( https://en.wikipedia.org/wiki/Kyushu_J7W ) and the Americans were heading towards contra-rotating 3 and 4 blade props at the end of the war with their XP-56 Black Bullet ( https://en.wikipedia.org/wiki/Northrop_XP-56_Black_Bullet ) If you're thinking about bombers and heavier aircraft, the whole line of Boeing was going to go that way (think Tu-95 Bear)

Curtis had a notion to put the same contra-rotating prop from the Seafire Fr-47 as a racing plane based on the P-40Q but beyond a few drawings, it never went anywhere... That had 8 blades and a massive tail.

[NARSES2]

Japan actually tested six-bladed props in WWII, but they were found to be impractical because the blades' blur was so strong that the pilot would not clearly see anything in front...

Interesting, I'd never considered that. Perhaps one of the reasons the Shinden was a pusher ?

[zenrat]

Hmmm...... interesting indeed.

Are you thinking commercial, military or civilian? Or all together?
In general aviation the popular choice seems to be three blades. Military, up to recently, definitely four. Commercial four up to recently with the new five, six or more blades.
Perhaps its the same thing that holds up old rickety buildings..........tradition!

Mmm, OK, perhaps I should have been more specific?  How about World War Two, with piston engines.  OK?

Doesn't H's point still hold good? Supermarine tried both solutions on the later Spitfires and only seemed to come down on contra-props as the ideal because of the horrendous torque effects from the 5 bladed Griffon engine versions.

Torque was an issue with the Supermarine Schneider Trophy seaplanes (one float would dig in) and they only had two blades.

[PR19_Kit]

Hmmm...... interesting indeed.

Are you thinking commercial, military or civilian? Or all together?
In general aviation the popular choice seems to be three blades. Military, up to recently, definitely four. Commercial four up to recently with the new five, six or more blades.
Perhaps its the same thing that holds up old rickety buildings..........tradition!

Mmm, OK, perhaps I should have been more specific?  How about World War Two, with piston engines.  OK?

Doesn't H's point still hold good? Supermarine tried both solutions on the later Spitfires and only seemed to come down on contra-props as the ideal because of the horrendous torque effects from the 5 bladed Griffon engine versions.

Torque was an issue with the Supermarine Schneider Trophy seaplanes (one float would dig in) and they only had two blades.

Noooooooooo, I wasn't suggesting that the 5 bladed prop was the cause of the torque issues on those specific Spitfire marks.

The monster torque was due to the equally monster Griffon engine, which incidentally was almost the same capacity as the 'R' engine in the S6Bs. The use of the contra-prop on the later marks that used the same engine cancelled that torque out totally.

Supermarine tried to sort out the problem on the S6Bs by making one float longer than the other.

[zenrat]

The R made more power than the Griffon.  But then it did run on a mixture of benzole, methanol, acetone and tetra ethyl lead.

Would an S6B with a five bladed prop flip itself onto its back if the throttle was blipped?

[kitnut617]

I've read that increasing the amount of blades actually helps to combat the torque affect, Hawker Typhoon 3-blade to 4-blade for instance, or the Sea Fury switching to 5-blade from 4-blades.

IIRC, I read that when I subscribed to AEHS* some years ago.

* Aircraft Engine Historical Society

[rickshaw]

Well I'll be blowed. I had these very thoughts myself traveling down on the train Monday.

Been reading my mind mate ? 

Ah, but are yours fostered by the same reasons mine are?

[NARSES2]

Well I'll be blowed. I had these very thoughts myself traveling down on the train Monday.

Been reading my mind mate ? 

Ah, but are yours fostered by the same reasons mine are?

Don't touch Fosters mate. Solely a bitter man