The escort-fighter phase of the test was conducted in a similar manner to the interceptor phase in that simulated missions were flown escorting B-45s and B-29s at 25,000, 30,000, and 35,000 feet. Since only three F-84s were available for the missions, and escort missions usually involve large numbers of fighters, it was not possible to determine the effectiveness of the F-84 in defending the bombers from the intercepting fighters.
While escorting B-45s at 25,000 feet, the F-84D had a combat radius of action of 460 miles, and at 35,000 feet it increased slightly to 475 miles. The tip tanks were retained on these missions. On a theoretical mission with a B-45 at 35,000 feet, in which the tips were jettisoned when empty, the radius of action went up to 580 miles. On this mission part of the internal fuel was used during the outbound leg of the flight, so with larger tip tanks the range could be extended even farther. On all of the escort missions the fighters were required to be over the home base at 10,000 feet with no less than 100 gallons of fuel remaining.
Only seven practice missions to determine the combat radius of action in the fighter-bomber role were flown, because the results matched the calculated figures so closely that further missions were unnecessary. The major emphasis of the tests was to determine the capability of the F-84 to deliver the full range of fighter-bomber weaponry: guns, bombs, and rockets. Since a separate test of the A-1B gun-bomb-rocket sight was under way at Eglin, only the functional aspects of the weapons and their effect on the airplane structure were tested. Accuracy of delivery was not considered.
Approximately 46,000 rounds of ammunition were fired at various altitudes and g-loads. Few malfunctions occurred, and there was no damage to the airplanes caused by the firing. The pipper of the A-1B sight vibrated so much during firing (20 mils plus) that target tracking was impossible. One night mission was flown during which the glare from the fuselage guns was so intense that no additional night firing was attempted.
Seventy-four 500-pound and 1,000-pound general-purpose bombs were dropped at airspeeds ranging from 450 to 560 mph and dive angles of o to 45 degrees. No adverse pitching characteristics were encountered at bomb release with the fixed-pylon bomb racks that had replaced the retractable racks on the F-84B, nor were there any rack malfunctions. On several pullouts from high-speed dives, more than 7.5 g's were registered on the accelerometer. Despite the pullouts and several intentional hard landings with 500-pound bombs aboard, there were no pulled rivets, nor was there any skin wrinkling or other structural damage. When napalm tanks were dropped at speeds in excess of 430 mph, however, the right tank would bounce off the fuselage. This problem had been encountered earlier by Republic Aviation, but no solution had been found at the time of the final report.
The final report concluded that the F-84D was satisfactory as an interceptor up to an altitude of 35,000 feet, as a short-range escort fighter, and as a fighter-bomber but that it should not be procured beyond the present contract, because a more advanced model, the F-84E, was entering production. The A-1B gun-bomb-rocket sight was found to be unsatisfactory, and it was recommended that no further production be authorized until its deficiencies had been corrected.
The operational suitability testing of the A-1B sight in the F-84D overlapped the test of the airplane itself. The sight, manufactured by the Sperry Corporation, was the first production version of the A-1 (Davis-Draper) sight, which had been tested at Eglin for several years in a P-38 with good results. Most of the problems with the A-1B arose during the air-to-air gunnery phase. Although the sight was designed to use radar for its range input, radar was not yet available on the F-84D, so manual ranging was required, and the pilots found it difficult to range properly using the backup manual system. The computing unit of the sight used vacuum tubes, since transistors were just being developed and were not yet in wide use. Vacuum tubes are sensitive to vibration, and there was a great deal of vibration when the six machine guns were firing, so maintenance was excessive. Also, the firing caused the sight pipper to fluctuate so much that tracking was impossible. On nonfiring tracking passes on B-29s, pilots were able to track with about a six-mil error, which is acceptable. I did not participate in the gunnery phase; to eliminate the pilot variable, the test officer flew all those tests himself.
In the rocket-firing phase three pilots, with minimal experience in rocket firing, fired 118 rockets at speeds ranging from 202 to 512 mph and dive angles from 3 to 35 degrees. The sight functioned well in the rocket mode, since ranging was not required, and accurate results were obtained.
In the accuracy phase of the bombing test, ninety-four 500-pound general purpose bombs were dropped in pairs at various altitudes, entry airspeeds, and dive angles. All were released automatically by the sight. With the A-1B sight, the pilot rolled into the dive with the sight reticle caged. When the pipper, in the center of the reticle, was on the target the caging switch was released. The sight began tracking as the pilot held the pipper on the target while depressing the bomb release switch. The airplane flew a slightly negative-g path, and at the proper time the sight released the bombs, and the pilot pulled out of the dive. Bomb release was signaled to the pilot by a flashing light on the gunsight and by the reticle's going out. In the manual mode the pilot depressed the bomb release button when the reticle went out.
I flew about one fourth of these missions and was able to save considerable time by flying two missions without refueling. We were using a bombing range to the northeast of the field, so I took off to the north, climbed to the entry altitude en route to the range, rolled into the dive, released the bombs, let down on the way back, and landed to the south. The armorers, who were standing by at the taxiway at the runway's end, loaded the bombs with the engine running. Then I took off and repeated the process. It was safe to load the bombs next to the runway because they were inert, carrying only a small spotting charge.
Two pilots, experienced in dive-bombing (not Ray Evans), made comparison drops in F-84Ds using fixed sights. The A-1B sight in the automatic mode was generally superior to the fixed sights, especially at higher release altitudes. In rough air the A-1B had a tendency to release the bombs too early, causing them to hit short of the target, but the fixed sight bombing was adversely affected by rough air as well.
The final report stated that the A-1B sight was unsuitable for air-to-air gunnery for the reasons stated above, but it was suitable for air-to-ground gunnery, rocketry, and dive-bombing. Later, after considerable modification it became the standard USAF fighter gunsight.
On Friday, September 23, 1949, we learned that the United States' atomic advantage over the Soviet Union had been lost, thus increasing the fears of the Cold War. That morning, Colonel Davis called all the squadron officers together and announced that the Soviets had successfully exploded an atomic bomb. The United States learned of it when an Air Force reconnaissance plane detected intense radioactivity in the air over the Pacific. President Truman announced it to the country that same day. There never was any doubt that they would be able to develop the bomb, but it came four or five years earlier than expected. Later it was discovered that the development of the bomb had been expedited by the turnover of vital technical information to the Soviets by spies and traitors in England and the United States. The next month Communists completed the takeover of China, and the People's Republic of China was formed.