Teledyne AQM-91A Compass Arrow

Lop Nor - 20 Oct 64

In the mid 1960s the USA was very keen to obtain photographic intelligence of the Chinese mainland and their nuclear testing area at Lop Nor, situated on a dried up salt lake deep inside China near Xinjiang. Although satellite imagery was just becoming available, as this photo of Lop Nor taken not long after the first Chinese nuclear test on 20 Oct 64 shows, it was unreliable and lacked the image quality of a lower flying aircraft. However, by this time the Russians had already shot down Frank ‘Gary’ Powers in his U-2 and the US government prohibited further overflights of Russia or China by US manned aircraft.

RB-57D

Overflights of China were already being undertaken by the Nationalist Chinese Air Force (CAF) in Taiwan operating a mix of RF-101 and RF-104 aircraft based at Taoyuan airfield thirty miles south of Taipei. In 1958 the US allowed the 408th CAF squadron, known as the Black Knights, to operate the RB-57D and in Feb 58 and Oct 58 two of these aircraft operated by CAF pilots were lost over the Chinese mainland. However, in 1959 the US had already decided to allow the CAF to operate the U-2 in a joint operation with the CIA and by 1961 the aircraft commenced a series of deep penetrations of Chinese airspace, losing a number of pilots as a result. The full story of CAF U-2 operations by the Black Cat squadron will be covered in more detail at a later date.

D-21

Despite the effort of the CAF, the US was determined to develop a new system capable of obtaining the information it required. This led to the development of the Lockheed D-21 drone which overflew Lop Nor a number of times between 1969-71 before it was cancelled. Launched from a rocked after being air dropped from a B-52 H, the D-21 was the cutting edge of current technology and was capable of cruising at Mach 3 above 75,000ft and in the event proved just too unreliable. However, the US had probably already anticipated that the D-21 might just be a step too far and back in 1966 had begun the development of a more conventional, high flying, stealthy, unmanned aircraft – the Teledyne Ryan AQM-91A Compass Arrow.

Development of the Teledyne Ryan AQM-91A Compass Arrow began back in 1966 and the design was based on their Model 154 Firefly drone - the new design was the first second generation UAV. Although outwardly fairly conventional in appearance, the Compass Arrow design incorporated a number of new and advanced ‘stealth’ features. The radar cross section was reduced by canting the vertical tail surfaces in towards the fuselage and by designing the bottom surface of the aircraft to be flat. The engine was mounted on top of the fuselage to reduce the infra-red signature and the engine inlet, leading edges of the wings and some other areas of the vehicle were fitted with Radar Absorbent Material (RAM). Similar in size to a small aircraft, the Compass Arrow was 34ft long, had a wingspan of 48ft and weighted over 5,000lbs. Powered by one GE J-97-GE-100 turbojet, it was designed cruise sub sonically.

Teledyne AQM-91A Compass Arrow

The Teledyne Ryan AQM-91A Compass Arrow was designed to be air-launched from a specially equipped Lockheed DC-130E aircraft. After separation the Compass Arrow would climb to around 78,000ft and self navigate its way along a 2,000 mile course using a Doppler internal guidance system. Equipped with an Itek KA-80A panoramic camera, over the course of a typical 4.5 hr mission, the Compass Arrow could photograph an area 1,720 miles long by 43 miles wide. The vehicle could also be equipped with IR sensors or ELINT equipment. After the mission was complete the vehicle would be guided into a recovery area by a microwave command system, deploy a parachute and be snatched in mid-air by a helicopter equipped with the Mid-Air Retrieval System (MARS.

Teledyne AQM-91A Compass Arrow

Although 28 Compass Arrows were produced by 1971, before they actually entered service relations with China improved and it was decided not to employ the aircraft on the risky overflights for fear of upsetting the new spirit of rapprochement. The Teledyne Ryan AQM-91A Compass Arrow was an expensive, but bold design and although it was never deployed on the operations it was initially designed for, the lessons learnt by Teledyne Ryan were useful in future designs. Nevertheless, the design showed that a conventional aircraft configuration would be unlikely to achieve the low RCS demanded of future designs. For this reason, the current crop of stealthy UAVs and UCAVs can all trace elements of their design back to the Teledyne Ryan AQM-91A Compass Arrow. The Compass Arrows were never used on operations and were placed in permanent storage in 1973 before being scrapped a few years later.

General Electric J97-GE-100 engine

But that is not quite the end of the story, because in 1998 a NASA paper reported that the twenty four General Electric J97-GE-100 engines, designed to allow the Compass Arrow to cruise at 80,000ft, were not scrapped as originally thought, but were actually placed in storage at their AMES research centre. It then appears that these engines may well be used to power a classified USAF Unmanned Aircraft System (UAS) programme, funded with money taken from the terminated J-UCAS programme, known as the Penetrating High Altitude Endurance (PHAE). The PHAE is believed to be a stealthy, twin-engined, UAV capable of cruising between 70,000 to 80,000ft and capable of carrying various weapons enabling it to conduct SEAD, as well as traditional ISR missions as necessary – so hopefully the money spent on developing the advanced technology for the Compass Arrow has finally been put to the use that was intended.