F6F wing cannons

[Barrett]

I'm working by memory here (the Hellcat book was published in 79 with the Corsair and Avenger books) so please stay with me...

I interviewed some VFN pilots including Bob Baird, the only USMC night ace. He and a couple of others said the 20s "put out a load of lead that was just fantastic" but functioning was a perennial problem. (I inferred that UK-US weapons were less reliable than Brand X designs. Hispano v. Oerlikon) Bob said on the day preceding his last kill he test-flew his bird 5 or 6 times before he could fire out a full 20mm load. Don't recall specifics, unfortunately.

In those days Grumman probably had the only dedicated history shop in the industry, as everyone else seemed to farm out history to the PR Dept. I know that Grumman had the info on armament but just didn't have/take time to peruse it.

Doesn't really address the question but that's what I remember.

 

[Builder 2010]

Does anyone have the 3-blade, 4-blade answer? Seems to me that a 4-blade with the same air moving capacity could be a slightly smaller diameter. Is that a factor in the decision? T-bolts had the 2800 and also have 4-blades. Less blades is more efficient since each blade gets into the disturbed airflow of the previous one. One blade is the most efficient save for the counterbalancing needed and it's very large diameter.

 

[MIflyer]

Here is a well known shot of some F6F-5N's in formation, all armed with 20MM. It is interesting that the cannon has a fairing around the base of the barrel rather than a more flush mounting such as the F4U used.

As for the four bladed prop question I have always thought it curious that the P-39Q-21 and -25 had four bladed props but not the others. I presume they were trying to improve performance and it did not work out too well.

 

[DarrenW]

....late F4U's did too,
& both were running the R-2800, like the F6F - so why didn't the F6F make the cut, for a 4-blader?

The F4U-4 & 5 was equipped with the "C" series of the R-2800, while the earlier F4U-1s and F6F-3 & -5s used the "B" series of the engine. The "B" series US Navy engines (-8 & -10) used the three-blade propeller while the "C" (-18W) used the four-bladed variety. The XF6F-6 was also equipped with the -18W and had the four-bladed prop but development never went beyond the prototype stage due to the end of hostilities in September 1945.

I think at the time the engineers found the three-bladed propeller suited the US Navy's needs quite well and felt there was no reason to mount a redesigned propeller with more blades on these two particular engines.

In contrast, the USAAF "B" series R-2800 engines that equipped earlier P-47s and P-61s (along with the "A" series engines of the B-26) all used four-bladed propellers.

 

[DarrenW]

As far as the question concerning wing cannons, from what I gather only the night fighting versions of the Hellcat (-5N in particular) were equipped with the two cannon/four machine gun combination. Early on many of these 20mm cannon were removed because they didn't have flash suppressors installed (a necessity for night fighters) but were later reinstalled after the proper modifications had been made.

 

[MIflyer]

Recently read that a big reason for going from 3 to 4 blade prop on the Typhoon is that it helped quite a bit with the vibration problem that airplane had, although it did not eliminate it entirely.

The F4U-5 variant introduced more highly automated oil-operated engine and supercharger controls that eased pilot workload. On the other hand, if you were doing a lot of relatively low speed acro you could end up draining the oil out of the system and that fancy control system would quit.

 

[pbehn]

Recently read that a big reason for going from 3 to 4 blade prop on the Typhoon is that it helped quite a bit with the vibration problem that airplane had, although it did not eliminate it entirely.

.

True, as far as I read, this was the driver behind Hawkers conspiracy theories about supply of props from Rotol. Switching back from four to three blade props wasn't just a propeller question, all sorts of balance weights had to be changed too.

 

[swampyankee]

I'm working by memory here (the Hellcat book was published in 79 with the Corsair and Avenger books) so please stay with me...

I interviewed some VFN pilots including Bob Baird, the only USMC night ace. He and a couple of others said the 20s "put out a load of lead that was just fantastic" but functioning was a perennial problem. (I inferred that UK-US weapons were less reliable than Brand X designs. Hispano v. Oerlikon) Bob said on the day preceding his last kill he test-flew his bird 5 or 6 times before he could fire out a full 20mm load. Don't recall specifics, unfortunately.

In those days Grumman probably had the only dedicated history shop in the industry, as everyone else seemed to farm out history to the PR Dept. I know that Grumman had the info on armament but just didn't have/take time to peruse it.

Doesn't really address the question but that's what I remember.

From what I've read, it the reliability problems with the 20mm was primarily American, not British; US-made 20 mm were much, much worse than those made in Britain.