The Grumman Skyrocket is a radical looking twin with significant pros and cons as a potential fighter. In the years before World War II it was one of the more interesting designs considered in a rapidly expanding and modernizing fleet.
After the jump, a unique fighter prototype.
In the late 1930s, as the Wildcat and Buffalo were competing for a big production contract, Grumman and the Navy were already looking at the next generation of carrier fighter. The much bigger twin-row radial engines (R-2600 and R-2800) were still in development, so Grumman decided to try a twin with the current R-1820 to get a dramatic increase in power and performance.
Like the Army Air Force P-38 Lightning, the F5F Skyrocket was quite different from other nation’s “heavy” fighters. The extra engine was not about load, it was about performance. The Navy was also considering a liquid cooled engine (V-1710) in the Bell XFL-1 Airabonita (a navalized Airacobra), and work was starting on Vought’s XF4U-1 Corsair with the big R-2800. Grumman too would hedge their bets by also offering an advanced single, the XF6F-1.
But in 1938-1940 the future was unclear. As radical as the Skyrocket looks, it could be considered “safe” for using the well tested R-1820. Flight testing showed the Skyrocket to have several good traits; the counter-rotating propellers made for good stability. The top speed over 380 mph was better than anything in service; and the rate of climb was phenomenal, the best of any of the experimental aircraft.
There were drawbacks too. There were aerodynamic issues with the fuselage. I’ve read several directly contradictory reports on what those issues were, so let me tread carefully here (pilots called the type very stable; engineers were critically concerned about its stability?!); but the nose and tail surfaces were redisigned a couple times, and much of this research was later applied to Grumman’s more advanced F7F twin. But the biggest issue seems to have just been manufacture and support. As a twin, the Navy was concerned the type could not be easily mass produced, and it would be a drain on fuel and maintenance resources in the fleet.
Apparently, by the time the prototype flew, it was already seen as a pure research aircraft. Even if test pilots praised its suitability for carrier operations, and delighted in climbing away from the XF4U-1 like it was standing still (LCDR Crommelin, Navy test pilot, reported thinking the Corsair must have been having engine problems, because he climbed away from it so easily), it was not seriously considered for production. The Army ordered a land based derivitive, the XP-50, but this was also purely for test and comparison. The type clearly had less potential than the P-38 (slower and lower critical altitude).
The type did however see lengthy operational service in Quality Comics “Blackhawk” series (later acquired by DC). This series was originally published from the ’40s to ’60s; the Skyrocket was the only piston engine aircraft used by the Blackhawk squadron until they re-equipped for the jet-age.
This subject is from the Academy kit. It was a simple and trouble free build.
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Always interesting to see these prototypes that just didn’t quite make it. I think it does show just how bold designers were getting and how the new ideas and risks they took paid out in progress in aviation and aeronautics in general if not the specific types the experimented with.
I think also, in the days before computer aided design, more really different ideas were built and tested. World War II is also the climax of the piston engine era, so definitely some interesting stuff going on.
This is another of those plausible “what ifs” I am fond of. I think if the type had been built, it was actually similar enough in performance to the Hellcat it wouldn’t have changed any specific events much. Except if Navy concerns about cost bore out, there might not have been the sort of insane over supply situation that led to any aircraft with major damage just being pushed over the side. And maybe the Corsair would have found its way in to a few carrier squadrons by late 1944 (instead of early ’45 when they really did).
Just as an aside, though my knowledge of aeronautical engineering is limited to the basic physics, when pilots raved about the stability and engineers worried about the stability they may have been talking about different things. For pilots the counter-rotating engines that produce a zero-torque that they don’t have to fight the plane might feel pretty solid. As an engineer looking at it my first concern would be the center of lift versus the center of gravity and how that might affect the flight characteristics.
That helps some Ernie, thanks. It was obvious they were somehow looking at different things; but its maddening that they couched it in similar language!
I know the “fixes” involved lengthening the nose and increasing the size of the vertical stabilizer.
It may well be that they had considered this, but to me, this design looks problematic. Most airplanes have a very organic looking relationship between the obvious center for lift and mass. This one looks like it could change throughout flight. What happens as the fuel tanks or ammunition empty? In most planes it wouldn’t seem to matter. In this one it looks very much like flight characteristics could change over the course of a standard mission.
I don’t know, if the fuel cells are centered on the main wing spar, either side of the nacelles, they might be right on the CG; and not a huge problem. I think the fixes had more to do with yaw stability, increasing “sail” area. the pilots were praising the stability from counter rotating propellers, which MAY have more to do with roll stability.
There are just so many dimensions it could take. Different speeds, attitudes, altitudes and loads. Good traits in one area are no indicator of good traits in another! And I think the main knocks on the type really were more cost and supply related. I think they were trying to find a range of behaviors more than fix a major problem.
I noticed I sort of soft sold the type’s main drawbacks in the post. I should have spelled out more clearly; unit cost, and supply/maintenance issues were the biggies.
Also, although it was fast compared to current types at 380; that is slower than the new generation of R-2800 powered aircraft it was competing against.
The Air Force was also unhappy with its critical altitude; performance dropping off above 15000 feet didn’t work for them, and the P-38 was notably better in this regard. But this last wouldn’t be such a big thing to the Navy. The Hellcat and Corsair were both built to a similar low altitude requirement.
A radical departure from Grumman’s fighter family looks, but still has Grumman written all over it.
Looked very odd to me years ago, but she grows on you — well me anyway.
Oh I agree. Its Grumman but different, in a cool sort of way. Eventually I hope to do one of these in an operational/hypothetical scheme. Like a mid-1943 tri-color.
I’ll be watching for that.
Had my own ideas for that a few years ago with the MPM 1/72 XF5F as a starting point.
Planned to adapt and substitute F4F-4 cowlings and P&W engines, windshield/canopy, underwing oil coolers, reshaped horizontal stabilizers/elevators for vertical fins/rudders. Landing gear and wheels would be adapted from a TBF with the gear bay covered by full length doors.
I’d keep the “pug nose”.
My logic was, with the Navy’s concerns about spare parts issues, Grumman would attempt to utilize as many “like” parts as possible.
Sounds like a good hypothetical project.
I’ve also seen it built up in Blackhawk markings. Not quite my thing, but it is entertaining to see!
Seen a few also — did nothing for me either.
Probably should, considering the Blackhawks were the biggest user!
I probably would have loved it when I was 13!
Westland Whirlwind has the same thing going for it — sort of a wallflower, but has an underlying attractivness about it.
Yeah and I think they would be similar performers too. The Whirlwind did well, but not exceptionally so. It’s engines were troublesome, but if it had really distinguished itself I’m sure a fix would have been found.
Hi. I see the posts are a couple of years old but I have just located this site. I have a RC Grumman Skyrocket which I purchased from an elderly chap from Hoppers Crossing in Melbourne, Australia earlier this year.
It is a scratch bult model with a w/s of about 2.4 metres, and painted dark blue with yellow wings and “US-Navy” printed on both sides of the fuse. We flew it last Sunday and it flew very well.
I was very interested in your comments about the history of the plane. Thank you for sharing that.
Ron (Tiny) Harrison,
Shepparton, Victoria, Australia
An RC model of it sure sounds interesting, it would be fun to see it fly!
This sight is still “active”, and I expect somewhere down the line it will be very active again. It’s mainly a matter of when I have time to work on models. The last two years have been consumed with family business, and for the next few months we’re doing needed work on the house (not as much fun as building models!). But retirement is looming, and I hope that means more modeling…