Question on Hellcat Propellers (Corsair)

[GregP]

There was a post with a question about the propellers on the Hellcat and the Corsair. The question was whether or not the Corsair had the same prop as the Hellcat. Both the F6F-3 and the F4U-4 had a prop described as a 6501A. This is very misleading.

The propeller on the F6F-3 is described as a 6501A-0; very incomplete. This number describes the individual blades. It is design 6501 and the "A" mean it is an assembly. As an assembly, it includes bearings, bushings, bushing drive pins, shim plates, drive pins, bushing screws, and balancing plug. The blade may then have a dash number and a letter. The dash number is the number of inches the prop was shorted from the basic blade. If it is a "-18" it is 18 inches shorter than the basic blade with each blade being 9 inches shortened. If there is a "B" after the dash, it means it has a bushing with an oversize bearing diameter.

The blade number says nothing about the propeller hub, which has it's own part number. Then hub is something like a 2 or 3 (number of major changes, up to 12+) followed by a 3 (3-blade) followed by B, D, E or F depending on the diameter of the shank (B = 1 inch, D = 1.5 inches, E = 2 inches F = 3 inches), followed by 20, 30, 40, 50 or 60 (SAE prop shaft spline number), followed by a dash number. The dash is the summary of the changes. It will be an odd number since odd means right-handed and even means left handed. SO it could be something like 23E50-501. 2 major changes, 3-blade, 2 inch hub, 50 spline, modification 501, right hand turn.

So, if the F6F-3 and the F4U-4 had the same blade basic number, it follows they were the same blade, maybe with different dash numbers and might have had different hubs. I always thought the number on the prop described the entire prop, but it doesn't ... it only described the blades.

 

[N4521U]

Holey crap. NOW my head is spinning. When it stops I may grasp what I've just read.
You've made sense of it all tho.
Thanks for that.

 

[FLYBOYJ]

Here, I'll make your head spin more...

HamStd

There isn't an FAA TCDS for the prop hub (23E50) but there is one for a 24D50 (P-51 prop). It also explains the hub/ blade relationship.

http://www.airweb.faa.gov/Regulator...48496DCB1D17867D8525670F0068C846?OpenDocument

 

[GregP]

Thanks Joe!

 

[N4521U]

So by the HamStd schedule, the blades for the Corsair listed is 3 bladed!?
Were the four bladed props Not HS?

 

[GregP]

Yes, the F4U-4 hub was a 4-bladed hub (probably a 34 E or F 50 or 60 unit. Maybe 34E50 to 34F60.

The blades were identical in basic number to an F6F-3, but may have been anywhere from 1 to 1.5 inches longer due to the dash number after the main part number.

 

[nuuumannn]

Like Joe posted, HS part numbers look confusing but are relatively simple. Every prop manufacturer does the same thing with their props, including McCauley and Hartzell. The hub is exactly the same in almost every hydromatic prop - the word "Hydromatic" was patented by HS to describe their internal mechanism. The blades are usually the same, but are cut and profiled by hand to the right length, but with different blade butt fittings, depending on the installation. Cropping of the blade is done with the old eye-ometer; I've done it before. You draw your blade profile based on what you think it should look like and make sure the others look roughly the same, then cut the tip off and shape the profile with a file. Hopefully it looks right. Any discrepancies in metal removed can be balanced out when the blades are individually balanced and then the whole unit static balanced before it's fitted to the aircraft.

The basic three bladed prop part number is 23E50, which is the same prop with minor differences, including the distributor valve in the centre of the hub (directs oil pressure from the governor to either side of the piston) and the ability to feather, which means the blade angle is greater and a feather stop is fitted. De Havilland hydromatic props are exactly the same, but with different splines on the spider so they can fit British engines, but the part numbers are roughly the same; the DH three blader, fitted to Beaufighters, Lancasters, Mosquitoes etc was the 23EXX. The four bladed HS prop, like Joe said is the same, but the hub has a different part number because it has four instead of three blades. The first link Joe posted shows an illustration from the manual and also drawings from the A&P (airframe and propulsion) propeller manuals that engineers refer to for notes.

Part numbers of hubs, blades etc are different on any prop; when you order a part from stores, you don't always want an entire assembly, so each component has its own part number as well as there being an assembly or sub assembly part number. I used to have a copy of the 23E50 CMM (Component Maintenance Manual) once, but I can't seem to find it...