After making arrangements to leave the flight engineer with the airplane, Barney, Rode, and I went to dinner and then flew back to Eglin in Rode's airplane. All the seats were occupied, so I was floored. The next day a C-47 was flown to Gainesville with a new engine and a crew to help install it. Except for the engine, which had indeed thrown a rod, there was no damage to the airplane. I'm sure that if this engine problem had occurred before my flight with Glyn I never would have taken her up.
The Eglin-based crew from MIT's instrumentation laboratory completed some modifications to the Davis-Draper (later A-1) radar-ranging gunsight in the P-38 in early April, allowing me to take up where I had left off in its testing. Some of my flight test school training proved valuable in the sight calibration runs that had to be completed before the firing and bombing phases could begin. I had to make numerous runs at precise airspeeds and altitudes, holding the sight on a fixed point and filming through the sight for as long as sixty seconds per run. The film was developed and analyzed back at MIT, and we were given the go-ahead for the firing and bombing phases.
The air-to-air firing phase was brief, since we only had to confirm what had been previously accomplished. The modifications to the sight were primarily in the bombing mode. The sight's special features, radar ranging and automatic lead computation, were not used for air-to-ground gunnery, eliminating the need for firing at ground targets. I spent a good deal of time for the next several months diving toward the ground from various altitudes and at various angles. Again, precise airspeed and altitude at the entry to the dive were of prime importance in guaranteeing that any inaccuracy could be attributed to the sight and not to poor technique. The sight, however, proved to be remarkably effective. Using it, I was able to achieve many direct hits and an overall low CEP (circular error probable). In a dramatic firepower demonstration, the sight allowed me to score a direct hit on a pyramid target after releasing the bomb and completing my pullout above a thin overcast. Although the observers in the bleachers could hear the P-38 in the dive, they couldn't see it through the cloud layer, but I, obviously, could see the target well enough to hold the pipper on it.
One rainy afternoon I was shooting the breeze with Ted Shea, MIT's on-site technical advisor on the gunsight test, one of the original Auger Innmates, and a good friend. He told me about a habit of mine, of which I was unaware, that used to irritate him no end. Prior to my starting the P-38 engines for each test flight, he would kneel on the wing next to the cockpit and go over the objectives of the mission, briefing me on anything special he wanted me to record. During his briefing I would seemingly ignore him, turning away to hook up the seat belt, shoulder harness, and radio leads; setting the altimeter; turning on various switches; and whistling the entire time. It infuriated him so much, he said, that he considered reporting it to Colonel Slocumb, but he soon realized that I was accomplishing everything he asked for on every mission. After that, he confessed, he rather enjoyed the routine. My wife also complains that I still don't seem to be paying attention when she is talking, but at least with her I don't whistle.
The YP-84 had arrived at Eglin for operational suitability testing before I left for test pilot school, but I had not been checked out in it, as only pilots assigned to the test of a new airplane could fly it. Upon completion of the testing the rest of the squadron pilots were checked out. While I was away, the production model, the P-84B, had been delivered. The Republic P-84 Thunderjet (in June it became the F-84) was the second USAF operational jet fighter. It was larger and heavier than the P-80 and was powered by the Allison J-35 engine, which produced 4,000 pounds of thrust. This was an axial flow engine; it compressed the intake air in a series of stages rather than in the single stage used in a centrifugal-compressor engine like the P-80's J-33. The axial-flow engine is more efficient than the centrifugal because the air flows in a straight line through the engine (axially) instead of having to turn through 90 degrees as in the centrifugal. It also has considerably less frontal area, an advantage in aircraft design. The axial-flow engine is used in virtually all jet aircraft today.
The Thunderjet had a high landing gear to prevent the long aft fuselage from hitting the runway on landing, requiring a long ladder for cockpit entry. It was a bit faster than the P-80, but the 80 had a higher ceiling.
The 20th Fighter Group, based at Shaw Field near Sumter, South Carolina, was to be the first group to be equipped with the latest model, the F-84C. Four pilots from the 20th (led by Capt. Jim Kunkle, the engineering officer for the 77th Squadron) flew to Eglin to familiarize themselves with the F-84 and its air-to-ground weapons delivery capability, since the 20th was a tactical group.
During the familiarization they encountered some difficulties with the retractable bomb racks and also with the landing-gear retraction system. The bomb racks did not extend far enough from the lower wing surface to avoid creating a wind-tunnel effect. The resultant low pressure between the bomb and the wing caused the bomb to hit the wing when released instead of dropping clear. The problem was corrected by lengthening the rack, thus moving the bomb farther from the wing. The landing-gear problem was due to the improper installation of a small part.
More serious was a sudden pitchup that occurred during a high-speed dive-bombing run. At about 600 mph in a steep dive, the nose of a P-84 suddenly and violently pitched up, imposing a high g-load on the aircraft. There was no apparent reason for the pitchup, and the Republic officials said that it had never been encountered by either company or Air Force pilots, including those at Eglin. Further tests were scheduled to find if it was a design problem or was something peculiar to that individual aircraft. That particular aircraft could not be flown again before the effects of the excessive g's on the structure had been determined.
On May 10 I was checked out in the P-84B, the test of that model having been completed. It was easy to fly, with good control feel and no bad characteristics that I could determine on that short first flight. The cockpit was much roomier than that of the P-80, and the gunsight was not right in the pilot's face. One feature I particularly liked was the variable aileron boost. It could be varied from high ratio (more sensitive) for aerobatics or low altitude to low ratio for high-altitude and cross-country flight. This relieved a lot of the strain on the pilot on long flights.
I had a personal interest in the pitchup problem. I knew I would be doing a great deal of dive-bombing in the 84, since the A-1 gunsight was to be installed in it, and I would be the test officer. The next day, however, I would be back in the P-80 for the firepower demonstration.
15
Firepower Demonstration, May 11, 1948
One of the missions of the Air Proving Ground Command was to demonstrate the firepower of the Air Force some three times a year for groups of about one thousand, comprising members of citizen groups, high-ranking officers of all services, and students of the various officer service schools such as the Air War College and the Armed Forces Staff College.
This particular firepower demonstration began for the participants at 6:30 a.m., as the pilots of the 3200th Proof Test Group filed into the headquarters briefing room. In their crisp, starched, open-collared khaki uniforms they looked more alert than they felt. The firepower demonstration was scheduled to begin at ten, and some of the bombers would have to be off the ground no later than nine.