Leandros
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Grumman F4F-3P and F4F-7
I’ve done some home-work on this. It interests me, also because there are so many discrepancies between the various available sources - and postings here. My main references are a couple of Grumman manuals on the F4F-3, Greene and Denn’s publications and excerpts from a VMO-251 web-site.
Before I get back to technical details I’d just like to clear up the (lack of) connection between the -3P and the -7, they were, as mentioned here in another posting, quite different airplanes, originating from different needs. The -3P was not dropped on the Marines because the Navy didn’t need it or wanted to use it.
The -3P was an emergency project, originating from a need created by the upcoming US counter-strike into The Solomons (Guadalcanal). The planners of that operation needed (photographic) information on the enemy positions there, and the Navy had little resources available for the purpose. A simple rebuild of some F4F-3s was the result and the Marines VMO-251 (M: Miscellaneous, O: Observation) squadron was hastily equipped with these and sent to the South Pacific.
The main modification of F4F-3P was the removal of the auxiliary fuel tank behind the cockpit, reducing the fuel capacity to 117 gls., and the installation of a Fairchild F-56 camera in its position. Weapons were retained but one source states that two of the wing guns were removed to lighten it – which was supposed to be done when flown as a bomber, too.
As it were, VMO-251’s first station was Noumea, New Caledonia, too far away for the modified Wildcat to reach The Solomons. They were instead used for the defense of that base. The same when they moved north to Esperito Santo, closer to the Solomons. Even from there they could not fly their original missions. From there the history is somewhat clouded but at least some of them probably participated in the defense of Henderson field, Guadalcanal.
Their photo missions were finally fulfilled by borrowing B-17’s from MacArthur’s “Air Force”, with VMO-251 personnel manning the cameras.
The -7 was a much more advanced project and meant to be used from carriers. To that I would like to add that one doesn’t have to fly all missions with maximum fuel….
The main modifications were:
To make the wings “wet”, in effect using wing space for fuel - no tanks as such, resulting in a fuel capacity of 555 US gallons in the wings.
Removal of the auxiliary tank – normally holding 27 US gallons (with self-sealing installed), to make space for a camera.
Installation of a Fairchild F-56 camera behind and little to the left of the cockpit
No armaments
Removal of pilot and oil tank armour. If this is to be taken all the way it would also result in 13 gallons increase in fuel capacity in the center (old main) tank – by removal of the self-sealing materials. Most probable as this was also known to contaminate the fuel.
Installation of a Sperry autopilot
Installation of a double fuel-dump system
Installation of an extra oil tank
Notes: As a standard the F4F—3 had a GF-5 radio installation with a special radio direction finder incorporated. Would the -7 have had any additional navigation equipment?
And, for those worried about this, the F4F had a “relief tube” as standard. Mounted under the seat, emptying through the bottom of the plane.
The only actual weight I have for the -7 is the allowable MTOW – 10.328 lbs. and the “empty” weight (Greene). What would have been nice to have is its “operational” empty weight. That is, “gross” - less fuel.
We can, of course, do it the simple way. If we presume that the MTOW was finalized at 10.328 lbs simply to get weight space for the actual fuel tankage, the Operational Empty Weight would be: 6.300 lbs. To reach that number I have retracted 685 gls. fuel (4.080 lbs.) – self-sealing material removed from the “center” tank, increasing its capacity marginally.
This looks reasonable. Standard (normal fighter) gross weight for the F4F-3 was 6.864 lbs inclusive of armour, self-sealing tanks, pilot and his paraphernalias, 110 gls. of fuel (660 lbs.), weapons and some ammo (526 lbs.), flotation gear, etc. Greene, in Profile Publications no. 53, quotes “empty” weight for F4F-7 as 5.456 lbs. That is 240 lbs more than what he quotes for the “normal” F4F-3A, but the -7 would not have weight additions for armament. This adds up to a little more than 500 lbs., depending on how much ammo you load up with. It is not known whether Greene’s empty weight on the “normal” Wildcat included armour. What this means is that the modifications weighed more than the removal of armor, armaments and flotation gear. It is not known whether the empty weight includes the camera, approx. 60 lbs. Radios, etc., are normally not included in the “empty” weight.
To see it from another perspective, if the only difference in added “operational” weight was armaments, the F4F-7 would have an advantage (in being lighter) in OEW (four MG’s and “normal” fighter ammo load = 526 lbs.).
I shall elaborate a little on this in a while.
Fred
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