by Kevin Wright
The Aircraft
Particularly in the early post-war years, the USA operated an eclectic mix of aircraft on Corridor and BCZ operations, including ‘combat’ types. After the 1953 unilaterally imposed Soviet ban on ‘combat’ aircraft in the Corridors and BCZ, usage became restricted to unarmed transport and trainer aircraft – though by practice not explicit agreement. Even when these ‘permitted’ types were used, clandestine photographic and SIGINT missions were conducted as discreetly as possible. The tell-tale bulges and aerials generally associated with SIGINT aircraft had to be minimised, made retractable, or disguised as much as possible. Cameras had to be hidden behind retractable hatches and covers. Despite such countermeasures, a close and knowledgeable observer would soon realise that these were not standard transport aircraft.
The ‘designations’ of the US aircraft types involved in the Corridor flights are often debatable. Various publications use designations such as EC-47, RC-54D, EC-97, RC-97, RC-130, C-130E-II amongst others, to describe them. Some designations were official, although they were not always applicable to the variants used in Germany, some were assumed, and others simply made up. Documentation, and those who worked on the aircraft often generally referred to them as C-97 or C-130, etc., identifying an individual aircraft by its tail number. It all helped maintain the external fiction, however thin at times, that these were just ‘ordinary’ transport and communication aircraft going about their daily trade.
Mustangs, Invaders and Fortresses
In 1945, 45 RS operated a mixture of P-51D Mustangs and F-6Ks (photographic reconnaissance Mustangs). There is some anecdotal evidence that they were used in the Corridors until their withdrawal in 1948.
‘Flight X’ of the 45 RS was established with A-26 Invaders. They used a carefully concealed forward-looking oblique K-18 camera with a 24in lens installed for Corridor flights. In 1948, the A-26s were redesignated RB-26s and served from 1946 until 1958. Using the call sign ‘Slot’, up to nine aircraft operated with the squadron, although usually only four aircraft were on strength at any one time. During this period there were two losses: on 30 July 1952 one crashed in a valley near Roith, Austria, and although there were no crew fatalities, several sustained major injuries. The following month another aircraft crashed just south-west of Wiesbaden following an engine fire, resulting in the loss of two crew members.8 The RB-26’s main camera fit was vertically mounted in the aircraft bomb bay and consisted of one K-17 with a 12in lens and a K-22 with a 24in lens, producing 9 × 9in images. A K-18 with a 24in lens, producing 9 × 18in images, was in a forward-facing oblique mount. Like the RB-17s they suffered from Soviet protests about ‘combat types’ but USAFE’s response was that they were not on the strength of a combat unit and were used for fast courier flights to Berlin and as VIP transports.
After their adoption of the ELINT role in 1947, the Detachment ‘A’ RB-17s of 10 RG flew peripheral and Corridor missions. These aircraft were transferred to the 7499 SS in November 1948 and remained there until 1953. In their latter days the Soviets objected to the use of the RB-17, considering them to be ‘combat types’. Their withdrawal was probably hastened by these protests. Up to eight RB-17s were used at various times during this period.
C-47 Skytrain
Between 1948 and 1960 up to eight C-47s passed through the unit, but only three were on the unit’s strength at any one time. Some carried the markings of the 7167 Transport Squadron (7167 TS) then based at Wiesbaden. They used the call signs ‘Willy’ or ‘WWA’ under Project Red Owl. The cameras were installed beneath the cargo hold floor, which allowed the carriage of cargo and passengers to give an appearance of ‘respectability’ but made access to the cameras difficult. The C-47s are known to have carried a K-17 with a 12in lens and a vertically mounted K-22 with a 24in lens. Another three K-17s with 12in lenses mounted in a trimetrogen arrangement gave horizon-to-horizon cover. All the cameras produced 9 × 9in format images but there are unconfirmed reports of a camera being fitted that produced 9 × 18in format images.
In the early years visual reconnaissance was frequently practised. Sergeant Fordham of the USAFSS recalls that in 1953 he was tasked with standing in for his boss, Lieutenant Pearsall, on the weekly C-47 courier flight taking SIGINT material from Berlin to Wiesbaden. After take-off from Tempelhof, he was taken to the flight deck and as they overflew airfields along the Corridor, he and the flight crew noted the numbers and types of aircraft at each airfield. The flight crew had simply expected him to do this as Lieutenant Pearsall usually did so when he was on the weekly run.9
C-54 Skymaster
From 1950 ELINT and camera configured C-54s, of various models, flew from Wiesbaden on Corridor and peripheral missions, replacing the RB-17s. A total of ten aircraft passed through the squadron before they were replaced by C-97s in 1963.10 Two ELINT equipped C-54D’s served from 1955 until 1963 on Project Pretty Girl, although they had been Wiesbaden residents since 1951. On ELINT missions they carried a crew of thirteen that included seven electronic warfare officers. The onboard equipment included AN/APR-4 direction-finding receivers and an AN/APR-2 ‘panoramic receiver’. These aircraft had a very visible under-fuselage ELINT antennae, until a 1960 modification programme, and were employed on peripheral missions rather than Corridor flights.
A single C-54D (43–17248) arrived in 1949–50 to be employed on Project Hot Pepper. The aircraft was dual-role ELINT and photographic reconnaissance, though primarily used for the latter.11 It carried a battery of cameras hidden behind pneumatically operated doors and hatches that were intended to be externally invisible. The main camera was a K-30 fitted with a 100in lens that produced 18 × 9in images. This was positioned directly behind the flight deck, used an electrically powered mounting, designed to allow it to take oblique images from each side of the aircraft. There were also three K-17s fitted with 6in lenses in a trimetrogen mount, located just behind the nosewheel housing, for mapping and survey work.12 In 1957 ‘Hot Pepper’ returned to the USA for an updating programme that installed a covert, removable ELINT capability by fitting: an AN/APR-9 receiver, AN/ALA-5 pulse analyser and AN/ANQ-1A recorder. The displays and operators’ positions were hidden as much as possible by fake panels when on the ground. In 1958 another upgrade incorporated the AN/APR-9 system’s antenna into the fin, removing the obvious bulge on the fuselage underside which made it more externally resemble a standard cargo C-54. The aircraft was withdrawn from USAFE by March 1962.
Another C-54D and two C-54Es were used for Project Sara Jane. Furnished with VIP interiors, they were equipped with fourteen concealed Fairchild P2 cameras installed in fuel-tight compartments in the wings, hidden by pneumatically operated doors. The cameras could be operated discreetly from the flight deck without any passengers being aware of it. The aircraft may have been used for courier flights to US embassies in Eastern Europe, providing additional opportunities for covert photography.13
One C-54D (42–72685) served with the squadron from December 1955 to November 1962. It was modified to carry photographic and infrared equipment to support the Automatic Terrain Recognition and Navigation (ATRAN) programme under Project Lulu Belle. The ATRAN programme is described more fully later in this chapter.
CT-29 Carol Ann/Ocean Gem
The CT-29A was a conversion of the T-29 navigator training aircraft that was itself based on the Convair 240/340 civil airliner. The first of four that served with the 7405th SS arrived in September 1959 to replace the C-47s that flew their final missions in May 1960. One aircraft (49–1917) was lost after crashing at Breckenheim near Wiesbaden on 9 February 1967 following an engine failure after take-off. By August 1968 the three remaining aircraft had left the 7405 SS to be modified and transferred to the Pacific Theatre for Project Ocean Gem.14
The cover role for the CT-29 was the operation of the Berlin air courier service and, according to a 1960 document, they flew about twelve missions per month.15 The reconnaissance equipment was separated from the main compartment by a false bulkhead at the
rear of the aircraft, so that passengers and cargo could be carried to maintain the cover story. Behind the bulkhead the camera compartment contained a trimetrogen arrangement of KA-1 cameras in a roll-stabilised mount, the operator, his console and stored film.16 In 1962 an oblique camera with a 40in focal-length lens looking out through the aft escape hatches on a more flexible mount was installed. When the aircraft was on the ground the camera was hidden behind a false shipping crate. In 1963, the aircraft was redesignated Ocean Gem.
All the CT-29s had suffered from poor maintenance prior to their conversion and by 1965 the three remaining aircraft had their severely corroded wing spars replaced. The weight of the onboard equipment was becoming a major safety issue because the aircraft was unable to sustain flight on a single engine. This was the primary cause of the 1967 crash.
C-97G Stratofreighter
Nine C-97s, of various types, were used over the years, seven of which were uniquely configured for the reconnaissance role. They were the mainstay of US Corridor (Creek Flush) and peripheral missions from 1962 to 1975 when they were replaced by the C-130 Hercules. The squadron had, on average, five C-97s on the strength of which three were fitted primarily for the SIGINT role and two for photographic reconnaissance operations.
The C-97G’s sensor fits frequently changed as camera and reconnaissance technology advanced. During the 1960s camera fits used a range of 48, 66 and 100in lenses. All the cameras produced 18 × 9in images as hard copy paper prints. After 1969 the camera fit changed to one that recorded images on 5in wide film that was viewed in positive film format. The fit became a KA-82A panoramic camera with a 12in lens mounted vertically, producing 5 × 24in images, and a KA-82A panoramic camera with a 48in lens in an oblique mount, known as the ‘H-Pan’. The H-Pan KA-82A images were 5in by up to 48in in full-frame mode, although it could also be set to image a more selective field of view. RS-10 infrared cameras were also added later.
One C-97G (52–2724) was modified under Project Side Kick from late 1961 and delivered to the 7405th SS in June 1962. It soon went back to the USA for depot-level maintenance and upgrading before moving to the Pacific Theatre until 1968. It returned to Germany in late 1969, equipped with a KA-81A camera fitted with a 48in lens and a KA-82A fitted with a 12in lens as well as an RS-10 infrared device. Known as Rivet Giant, the aircraft remained until 1975.17
C-97G (52–2687) joined 7405 SS in October 1961, serving until December 1975. It was a combined photographic and ELINT aircraft, known as Flint Stone. With camera and ELINT equipment hidden from sight, it was still possible to maintain the fiction of being a ‘courier and internal USAFE transport aircraft’.18 Although mainly undertaking Corridor missions, it flew peripheral flights too. Depot maintenance in 1969 installed new camera equipment (KA-81A with a 48in lens, KA-82 with a 12in lens and RS-10 infrared) and the project was renamed Rivet Stem.
The other camera-equipped aircraft (52–2688 Eager Beaver) joined the 7405 SS in July 1963. It carried a 66in lens oblique camera and a KA-82 with a 12in lens. Returned from modification and upgrading in the USA during 1967, it carried a Fairchild KS-96A panoramic camera and an RS-10 infrared being redesignated as Rivet Box. In late 1969 the aircraft left Germany for the MASDC, later AMARC, at Davis Monthan Air Force Base (AFB).19
There were two ELINT equipped C-97s (52–2639 and 52–2686) used exclusively on peripheral missions because their large, distinctive under-fuselage ELINT ‘canoes’ were too obvious, making them unsuitable for Corridor and BCZ missions. The aircraft flew the IGB, Baltic, Adriatic, Black Sea and Mediterranean missions. Little Guy, the code name for 52–2639, arrived in early 1963 and carried eight ELINT operators on the main deck of the aircraft. It stayed at Rhein-Main until January 1969, when it returned to Fort Worth and subsequently passed to Israel.20 52–2686 left service in 1969.
The unit had a C-97 (52–2678) used as a ‘front-end crew trainer’, retaining the dual navigator position like the mission aircraft. Delivered in 1967, it was also used as a cargo aircraft. It only stayed until July 1969 and operated under the designation of Rivet Tub.21 A single standard KC-97F (51–0246) was briefly used for support work and crew training between 1963 and 1964.22
C-97 53–0306 was Project Rivet Flare. Assigned to 7405 SS in mid 1969, it remained on strength until the last C-97s were withdrawn from Germany in 1975. Primarily engaged in photographic reconnaissance operations, it had the post-1969 panoramic camera fit installed.
The gradual rundown of the C-97 fleet started in December 1969 and was completed by December 1975. By then the 7405 SS’s peripheral electronic reconnaissance tasks had been taken over by SAC RC-135s, mainly operating from the UK and Greece. Besides the 7405 SS C-97s there were two other aircraft that operated in the Corridors, BCZ and peripheral regions.
Project Pie Face
C-97A 49–2952 was the first C-97 to arrive at Rhein-Main. It had been converted to a photographic reconnaissance configuration in 1952 and assigned to the 7499 SS in the summer of 1953. The giant K-42 main camera, known as Big Bertha (and later as Daisy Mae), was fitted with a 240in lens, in a left-facing oblique mount, and was generally known by the project name Pie Face. The camera was over 6ft tall and weighed around 6,500lb, reputedly being the largest airborne camera ever built. It produced 36 × 18in negatives, known as ‘Texas postcards’ by the Photographic Interpreters (PI). The camera could see 30 to 40 miles and in ideal conditions could allegedly see the proverbial golf ball from 45,000ft. Besides the Pie Face camera there was also a K-30 with a 100in lens in an oblique mount and three K-17s, probably in a trimetrogen mount. These latter cameras were synchronised to operate with Big Bertha.23
The gestation period for Pie Face began in 1948 when the USAF experimented with very long focal-length oblique cameras to gather imagery of airfields in the Chukotski area of Siberia.24 The missions often involved remaining in ‘international airspace’ but flying sufficiently close to the coast to acquire photographs of the area. But even the large 40in to 100in focal-length cameras produced imagery that was inadequate to identify previously undetected installations when standing 10 to 20 miles offshore. They were also incapable of imaging already identified installations in sufficient detail to satisfy USAF planners’ requirements.25 They were, however, a driver for the development of larger lenses.
The Big Bertha K-42s were designed at the Air Force Optical Research Center at Boston University in 1951. The cameras, with their massive 240in lenses, were fitted into an RB-36D Peacemaker aircraft and were said to be able to image installations up to 80 miles away.26 However, the RB-36s could not be used along the Corridors, because of the restrictions. Incidentally, use of the giant RB-36 Peacemaker was regarded even too provocative to be used on many peripheral missions. So another platform had to be found if the camera was to be used in Germany. One K-42 was operated experimentally for six weeks in an early prototype YC-97 airframe and flown from Rhein-Main. Although the airframe’s performance was poorer than the newer KC-97 versions, the trial proved the camera’s value.27 In April 1953, Brigadier General Ackerman of the USAF Directorate of Intelligence sent a memo to AVM Francis Fressanges RAF in London advising him of the imminent arrival in Europe that summer of a new 200in lens camera. It was the precursor to sharing Pie Face imagery with the British.
The short runway at Wiesbaden AB meant that Pie Face C-97A initially had to operate from Rhein-Main (Frankfurt) AB, where it was known as ‘Det 1, 7499 SS’. The camera’s best results were achieved from around 30,000ft, but this was not possible because of the Corridors’ 10,000ft upper limit and often unsuitable north-west European weather conditions. Cloud was the most obvious weather factor, but thermal currents, airborne pollution and particles, and varying temperatures contributed to image distortions. The camera also suffered from airframe vibrations caused by being mounted in the piston-engined C-97. Nevertheless, Pie Face was used on around twelve Corridor and peripheral flights per month.28 On the peripheral flights the optimum 30,000ft was a more usual operating altitude. I
n 1962, retired from Europe, Pie Face had a brief reprieve during the Cuban Missile Crisis when it flew from Florida to image the island.29
The value of operational images acquired by Pie Face, where conditions were rarely ideal for such long-range photography, is somewhat disputed. In the early days there were difficulties with the camera’s shutter design.30 Although many praised Pie Face’s operational performance, there were critics and Dino Brugioni recalls that the camera was:
plagued with problems that caused it to vibrate and produce smearing on the newspaper size images so that photo interpreters would see several smeared frames together with several clear ones.31
Project Wine Sap
One C-97 used in Corridor operations (53–0106) was a very special aircraft indeed. Known as Wine Sap, it was modified during 1965 as an ELINT aircraft. It also carried a T-11 vertical camera to enable the aircraft’s geographic position to be correlated with the collected ELINT data. Previously operated by the CIA, it used the ‘Precision Parameter Measurements System’ (PPMS) developed to collect missile data – see later in this chapter. The aircraft was assigned to Project Creek Flea, collecting information on emitters along the Corridors, particularly the SA-2 Guideline SAM (Soviet name: S-75 Dvina). This had been a high-priority intelligence target since the late 1950s when it was deployed in large numbers across the Soviet Union and close to Berlin. The data collected by Creek Flea was used to develop countermeasures to the SA-2 system that was proving so effective over North Vietnam and the aircraft was occasionally deployed for periods of work against Vietnamese SA-2 systems. After a 1967–68 equipment refit it was retitled Rivet Stock. The aircraft stayed with 7405th SS until 1975, by which time the emphasis had moved onto monitoring SA-3 Goa and SA-4 Ganef associated radars.32