announcement followed on June 12.[263] A total of fourteen drones had been shot down by the end of 1967. A fifth Nationalist Chinese U-2 was also shot down on September 9, 1967. The pilot, Capt. Tom Hwang Lung Pei, was killed when an SA-2 hit his plane.[264] In early 1968, it was decided to end the Nationalist Chinese U-2 overflights, due to the risk. From now on, the 147H drones would carry the burden of watching China.
The new role had a cost — on January 20, 1968, the Chinese shot down 147H-25. The
THE DEFINITIVE DRONE — THE 147S BUFFALO HUNTER
December 1967 saw the debut of the first of a family of low-altitude drones, a series that would form the backbone of the final years of 147 operations. The 147J was not the ideal low-altitude drone. Its long, flexible wings, originally built for the high-altitude 147G, were somewhat unstable at low altitude and prevented the 147J from making sharp turns. The 147NPs and NQs were a quick, short-term effort.
There was a need for a low-cost drone specifically designed for the low-altitude mission. Ryan was told that if they could produce a cheap drone to replace the 147J, the production run would amount to several hundred, compared to only thirty to forty of the other models.
In building the new drone, Ryan went back to the basic Firebee design.
The Firebee's 13-foot wing was used; this was much cheaper than the long wing of the G and J models. The fuselage was 29 feet long and carried a redesigned camera system. Rather than two cameras, as on the 147J, the new drone had a single camera. This provided an 80 percent increase in coverage. The contract for the new 147S drone was issued in December 1966. Unit cost was about $160,000—40 percent less than that of the G and J drones.[266]
It would take a year to get the 147S into operation. Five of the last 147Gs were modified to test the new 'poly-profile' low-altitude control system. In the first test of the system, the drone flew into the water. There was a lag in the system, with corrections coming too late. It took six weeks to develop a fix for the problem. It was known as the 'Polly Get Well Kit.'
When the 147S test flights were completed, there were a number of proposals for modifications which would give it additional capabilities. These included antiflutter kits, different yaw rate gyros, multiple altitude settings, radar altimeters, and a digital programmer. It was decided to group the changes in production blocks. All the drones in a specific block would have identical configurations.
The first such block was the 147SA. A total of forty were produced. The first operational mission was made in December 1967. The drone's camera could produce photos with a one-foot resolution along a sixty-mile-long strip of North Vietnam. In some cases, objects as small as six inches could be identified. On one mission, a stack of truck tires in a storage yard was photographed. The trademark could be read.
Most of the 147SA missions were directed at the main bridges around Hanoi. These were under repair, and it was necessary to have regular coverage. Other targets were supply lines and SAM sites. In some cases, winds or navigation problems would cause the drone to go off the track, but the targets of opportunity picked up would often be more valuable.
The early 147SA missions were very successful, and, in March 1968, a second block of forty drones was ordered. The 147SB carried the multiple altitude control system (MACS). The 147SB could be programmed to fly at three different altitude settings between 1,000 and 20,000 feet. It could also vary between the three settings throughout the mission, making it much less predictable. The drone was also equipped with new yaw gyros that allowed tighter, more precise turns.
The first 147SB missions were flown in March 1968, overlapping with the 147SAs. One early mission was flown by a pair of drones over Haiphong Harbor. The Soviets claimed one of their freighters had been tor-pedoed by the United States as it entered the harbor. The drone unit was ordered to photograph the ship to see if it had been damaged. The drones' flight paths were to cross over the ship. The two drones flew as programmed and returned with photos looking directly into the cargo hold.
They showed no damage at all. The North Vietnamese, however, caused some damage when they opened fire at the low-flying drones. Shooting at a nearly flat trajectory, the shells hit the ground throughout the harbor area.
The 147S drones were the source of a number of 'war stories.' None matched the adventure of 147SB-12 on October 6, 1968. After launch, the MACS had a problem and rather than flying at an altitude of 1,500 feet, the drone flew at 150 feet above the ground. Its programmed flight path took it under a line of high-tension power lines. The photo showed the tower looming above the drone, while on the ground, people were looking upward at the low- flying plane. The unit commander posted the photo on the bulletin board with a note saying, 'The FAA frowns on this bullshit!'[267]
Such achievements were not without cost. With the partial bombing halt on March 31, the drones became a prime target. Flying at 1,000 to 1,200 feet, they were taking heavy losses. On April 21, SA-17 was lost over Haiphong.[268] On June 8, a drone was reported shot down over Hanoi.[269]
A change in profile was necessary — the drones were set to fly at 500 feet and 500 knots. This put them below the m i n i m u m altitude of heavy antiaircraft guns, while the high speed made them difficult to hit with light antiaircraft guns or small arms.[270] Still, by late 1968, the North Vietnamese had shot down a total of about forty of the drones.[271]
The North Vietnamese also sought to end the drone flights through political means. When the Paris Peace Talks opened, the North Vietnamese demanded an end to all reconnaissance flights. This was described as the first order of business: the halt must be 'without delay' and 'definite and unconditional,' and continuation of the talks was dependant on U.S. acceptance of the demand.[272] This effort also proved ineffective. United States reconnaissance flights continued to monitor North Vietnamese activities.
These reconnaissance photos showed that, within two weeks of the bombing halt, the North Vietnamese had repaired all the bombed-out bridges between the seventeenth and nineteenth parallels. Roads had also been made passable, and troop and truck traffic had quadrupled to some four hundred trucks per day.[273]
The next version of the 147S family made its debut in November 1968.
This was the 147SRE night reconnaissance drone. They were equipped with a near infrared strobe. In flight, this was visible as a small red light; it was hard to see unless someone looked directly at it, making the drone much harder to track than the white-light strobe on the NRE. The film was geared to near infrared, and the camera had a filter to cut down the effects of haze. A doppler navigation system also provided better accuracy than the NRE.
The first flight, by 147SRE-1, was made on November 7, 1968. A total of five flights were made in November and six more in December. Missions were flown in the predawn hours, when activities were just starting. When compared to photos taken later in the day, this would give an indication of activities.
The December 19 flight of SRE-2 was an adventure. As it flew over a SAM site, it was fired on. The camera photographed the SAM overtaking the drone, then exploding behind it as the SAM hit the ground. A second SAM was launched, which passed so close the photo was burned out by the exhaust flame. The flight was intended to cover the Haiphong docks and seaplane base, then turn west to cover an airfield near Hanoi. The doppler system was not set correctly, however, and the turns were coming late. This caused the drone to fly to an area northwest of Haiphong, where it missed colliding with a ridgeline seven times. The photos showed it only ten or twenty feet above the trees. The final 147SRE flight was made in October 1969.
Although the SREs were successful, less use was made of the system than was possible. The photo interpreters were not trained in analyzing the near infrared images. Many times targets were missed.[274]
A total of 340 drone missions were launched in 1968. Of these, 205 were 147S drones, while only 67 were 147H high-altitude flights. Clearly, there was a shift in operations. The original concept of high-altitude, covert
