Still not easy

The WWII problem - hit an aircraft carrier steaming at 33 knots with a torpedo that runs at 33 knots. This example is a drop roughly abeam the 800-ft long carrier at 2,000 feet, well inside the 1,000 yards usually cited as the maximum drop distance for accuracy. I've revised the calculation to roughly account for a drop from 200 feet (3.5 seconds of air time) and 200 knots, which increases the average speed of the torpedo significantly and therefore reduces the lead required. It's now obvious that the lead is sensitive to the drop speed and altitude, the ballistics (lift/drag) of the torpedo in the air, and the deceleration of the torpedo in the water until it is at its run speed of 33 knots. The good news is that the lead determination is less sensitive to the target speed, although it's still important, and the ship has less time to turn into or away from the torpedo track.

Sticking With What You Know

In response to the U.S. Navy's need in the late 1940s for a carrier-based, long-range jet bomber, the Glenn L. Martin Company, the successful purveyor of large sea planes, proposed its Model 245, a hybrid that could fly to the carrier's operating area, refueling from submarines along the way, and then jettison the boat hull for operation from a carrier. It was apparently to be used only from staging from a carrier, because it did not have folding wings. The Navy went with the more conventional Douglas A3D Skywarrior instead.

Pictures and information courtesy of the Glenn L. Martin Maryland Aviation Museum.

This Just Isn't Right

In looking up information to respond to a request, I was reminded of this unique Grumman. It was the cargo version of the venerable S2F ASW airplane, modified to be the aerodynamic prototype for the AEW version of the airplane. The addition of the big radome over the fuselage required the change shown here to the empennage and also a change to the wing fold arrangement. It did not have the stretched fuselage of the production airplane, however, as evidenced by the red propeller warning stripe being so close to the aft edge of the pilot's side window. After flight test, the dummy radome was removed and the airplane resumed its role as a transport.

The production airplane was originally the WF-2, redesignated in 1962 as the E-1B. Strictly speaking, there was a WF-1 but not an E-1A, since the WF-1 was cancelled at the mockup stage. It was to be an S2F airframe simply modified with an APS-20A mounted above the cockpit. This would have preserved the original empennage and wing fold arrangement, albeit with the addition of small fins on the horizontal stabilizer to maintain directional stability.

XFL-1 Carrier Suitability Evaluation

The Bell XFL-1 flunked its shore-based carrier suitability evaluation due to excessive tail rise on arrestment, not that it was being seriously considered for production after the XF4U reportedly exceeded 400 mph in level flight. Note that the pilot is not wearing a shoulder harness, which was surprisingly absent in all Navy carrier aircraft at the time given the abrupt stop involved in an arrested landing.

Antiaircraft Bombs

In the late 1930s, the Navy's Bureau of Ordnance developed a tactic to deal with large, heavily defended bomber formations. The fighters would fly above them and drop anti-aircraft bombs. These were small, with a light case containing two pounds of TNT, but would cause considerably more damage than a bullet. BuOrd designed small containers housing two bombs each for installation within the wings, five containers to a side. Twenty bombs were to be dropped at one time, covering an area 150 yards long and 50 yards wide. The pilot was to be provided with a downward vision window for aiming.

This was a requirement in the Navy's 1938 fighter procurement, so the Bell XFL-1 (shown here), Grumman XF5F, and Chance Vought XF4U were all built with the small bomb bays to house the BuOrd containers and a downward vision window. According to a BuOrd history published in 1953: "Although antiaircraft bombs gained a group of staunch advocates, their admirers were more numerous on the higher level of planning than on the lower one of actual combat." The bomb bays were deleted from the production F4U by BuAer although the window remained through at least some (most?) of the F4U-1As. Although BuOrd bought 200,000 anti-aircraft bombs, they were apparently only used as antipersonnel weapons.

The Navy and Liquid-Cooled Engines

Based on reading most accounts of the Naval aviation history, one would think that the U.S. Navy had no interest in liquid-cooled reciprocating engines for carrier-based airplanes after 1929. Certainly it only deployed ones powered by air-cooled engines thereafter. In fact, the Navy maintained an active role in liquid-cooled engine development into the early 1940s. One example was their selection for evaluation of a derivative of the Bell P-39 Airacobra, the XFL-1, in 1938. The Wright H-2120 was another such effort. It was a very unusual configuration - a twin-row radial engine, but with the six cylinders in the aft row lined up with those in the front row and each such pairing liquid-cooled. The objective was to minimize the frontal area of a radial engine and avoid potential problems with air cooling the aft row of cylinders. The Navy funded development of the H-2120 from about 1933 to 1936, when a 100-hour development test was run at 1,000 shp. At that point, both Wright and the Navy lost interest in pursuing this particular configuration, with the feasibility of air-cooling the second row of cylinders having been demonstrated.

Not Doing It Right

This illustration is what the Air Force Museum is using to depict the "idiot loop" that the Air Force developed in 1952 to more or less safely deliver a nuclear weapon from a tactical aircraft. Safe in terms of both ingress and egress. The problem is, it's depicted as a loop and the actual maneuver is a half-Cuban eight. It starts as a loop (a loop is what you'd be doing on a Ferris wheel if the car you were riding in wasn't free to dangle) but after you go over the top, inverted, you do a half roll back to upright flight while diving back to treetop altitude to depart the premises as fast as possible back along the route you took to get to the target. A loop, as depicted, would keep you in the vicinity of the upcoming blast for too long...

After I wrote this, I discovered that there were proponents (at least one in the Navy, anyway) for the loop recovery from the over-the-shoulder mode and it was evaluated by him at China Lake in an F7U-3. There is a video of it somewhere on the interweb which I can't now find.

It was compatible with LABS since the pilot was free to recover from the inverted climb that he was in by any maneuver he wanted to use. However, in addition to probably not providing as much separation as the half-Cuban eight (I don't have any numbers to compare the two), completing the loop before encountering the ground was not entirely risk free, whereas the half-roll in a dive was. Remember that having enough altitude coming over the top to complete the loop was compromised by having to lug a heavy, draggy bomb a good part of the way up and a dive to build up loop entry airspeed was precluded by both the LABS computation and the need to make ingress at treetop level. The F7U-3 was probably better off from this standpoint because its engines were equipped with afterburners.

In any event, I haven't found any operational descriptions of the use of a loop on the interweb or in the literature other than this report.

This is an illustration of the three LABS alternatives from my book, Strike From the Sea.