Aviation Week report on RQ-170 Sentinel loss

AVIATION WEEK/BILL SWEETMAN

The first clear pictures of the center-line reconnaissance bay on Lockheed Martin’s RQ-170 Sentinel show that the small unmanned aircraft was carrying sensor balls mounted in an internal compartment with specially treated transparent panels—developed for the F-22—when one of them crashed in Iran on Dec. 4.

The new pictures were taken at Kandahar airport in Afghanistan on Sept. 30. The images show that a wheels-up landing would have inflicted massive damage to the bay and sensor package.. That package is “similar to some of the podded electro-optical/infra-red [EO/IR]systems” used by other non-stealthy aircraft and unmanned aerial systems, says a veteran black-world engineer with insight into U.S. UAS programs.

The accident was caused by a “lost [data] link, followed by, or simultaneous with, another malfunction,” says a second official involved with the program. Putting the loss into perspective, “We’ve lost over 50 MQ-1s [Predators] and 9s [Reapers], so this should not be a surprise.”

The U.S. Air Force squadron that flew Sentinels was activated in 2005 and the stealthy, unmanned aircraft was first photographed at Kandahar in 2007. Early RQ-170 operations were conducted from both Afghanistan—with CIA involvement—and South Korea.

The RQ-170s were brought back to the U.S. in 2009, re-equipped with a full-motion video (FMV) camera, and then redeployed to Afghanistan, say USAF intelligence officials. At that time it was operated by the USAF 432nd Wing’s 30th Reconnaissance Sqdn. (RS), then at the Tonopah Test Range Airport in the northwest corner of the USAF Nevada Test and Training Range. The wing also flies the Predator and Reaper, and the Tonopah base was once the clandestine home of the F-117 stealth fighter.

Prior to refitting, the aircraft carried a long-range, EO/IR camera thought by U.S. analysts to be used for monitoring missile tests and other activities in sparsely populated eastern Iran.

The RQ-170’s operational altitude of 50,000 ft. gives it an advantage over other lower-cost UAVs and the manned RC-135 Cobra Ball (for monitoring foreign missile tests) that are restricted to about 30,000 ft. and below. However, the Sentinel is not a high-end, very low-observable stealth design with sophisticated sensors. It is instead a robust, reduced-signature, sensor truck designed to maintain high sortie rates.

Other stealth design features include a variant of the “toothpick” leading-edge profile developed for the B-2. Stealth dictates sharp leading edges, but bluff shapes are better for aerodynamics and stability. The compromise on the RQ-170 and B-2 is to make the edges sharp at their ends, where more radar scattering is most likely, and more blunt at the mid-point.

Initially, flights are thought to have been conducted along the borders of Afghanistan. avoiding the airspace of neighboring countries. However, after adding shorter-range FMV, the aircraft operated in Pakistan’s airspace to monitor the compound of Osama bin Laden, and later over Iran, defense officials say.

The RQ-170 has a dual history of operations for both the CIA and Air Force.

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