Thursday, March 1, 2018

FJ-1 Tip Tanks - 1948 Bendix "Race"

Once upon a time, there were big-deal airshows with military participation, including "races". At some point the services were prohibited from competing with each other directly so they took turns year-by-year for the major events. The 1948 Bendix race was to be a Navy year, showcasing the new North American FJ-1 Fury assigned to VF-51. Takeoff was from Long Beach, California with the finish line at Cleveland, Ohio about 2,040 statute miles away.

When I wrote about this event in U.S. Naval Air Superiority, the range and speed numbers originally didn't add up. The FJ-1 cruising at 40,000 feet had a range of about 2,300 miles but almost certainly at a long-range cruise speed of only 350 mph versus the winning speed of 490 mph. However, looking at pictures of the airplanes involved, they clearly had different tip tanks than standard.


They were longer relative to their diameter, didn't have the position light in the tip and also had a rounded aft end and a fore-and-aft horizontal flange. The nose and tail resembled those on a 150-gallon external tank of the time with a longer, bulged center section and the FJ-1 tip tank fins added.

According to a Naval Aviation News article, these bespoke tanks could carry 290 gallons of fuel each versus the standard FJ-1 tip tank capacity of 170 gallons. These enabled the Bendix racers to fly much faster and still get to Cleveland. Just barely. One pilot flamed out 50 miles away from Cleveland at something over 40,000 feet and glided there for a dead-stick landing. The winner flamed out while taxiing in. Another climbed to 50,000 to stretch his fuel (the FJ-1 cockpit was not pressurized), became hypoxic and lost, finally crash landing in a field.

Now misreported most places on the interweb, a California Air National Guard pilot, not officially competing but just going to Cleveland in a P-80C nonstop with nonstandard tip tanks, beat the Navy's best time by a minute or so.

The question has come up as to the size of these non-standard tanks. It can't be directly scaled from the picture above because of the camera lenses distortion of length versus diameter. Knowing the volume proved to be less useful than I hoped. It turns out that the standard 150-gallon tank must have fore and aft voids. Stretching it to add a 140-gallon cylinder results in a tank that looks too long relative to the diameter. I also tried to correct the picture of the tank using the fore and aft sections of the 150-gallon tank, which looks better with respect to length but means the voids had to be eliminated; if retained, the addition only came to about 48 gallons.

The new tank center section did have to accommodate the tip mounting of the FJ-1's as opposed to being slung under a wing on a pylon so it may be that the fore and aft sections were modified to eliminate voids as part of this reconfiguration. This is my best guess at the size and shape: