Sled Driver

In Uncategorized on November 11, 2009 by hillermuseum

SR-71 Blackbird

On Saturday, November 21st, the Hiller Aviation Museum welcomes SR-71 pilot Brian Shul.  One of only ninety-three pilots who qualified to fly “The Sled”, Brian flew the SR-71 Blackbird for four years.  His book, “Sled Driver:  Flying the World’s Fastest Jet” provides a unique aviator-eye view of this remarkable flying machine.  Join us on Saturday November 21st at 11am as he shares his experiences in person in a special presentation at the Museum.

The Lockheed SR-71 was in many ways the most remarkable western aircraft of the Cold War, able to fly more than three times the speed of sound at altitudes of over 15 miles.  Piloting such an aircraft  at 2,100 miles per hour and 80,000 feet may sound exciting, but it requires remarkable qualifications and dedication.

 The SR-71 provided a means to collect intelligence about the adversaries of the United States.. This was the mission the Lockheed U-2 was originally built for, but the development of surface-to-air missiles made the U-2 vulnerable.  In 1960 a U-2 piloted by Francis Gary Powers was shot down over Russia, and it became obvious that a better aircraft was needed. President Eisenhower approached Lockheed to “…build an airplane that can’t be shot down”. The project was given to legendary aircraft designer Clarence L. “Kelly” Johnson at the “Skunk Works”. Johnson’s experience made him the ideal candidate for the job as he led many programs resulting in such successful aircraft as: P-38, F-80, F-104 and C-130.

 Just eighteen months later, Lockheed rolled out the first aircraft (originally designated A-12) for the CIA. This was followed by the YF-12 and then the SR-71. A total of 50 airplanes were built under several different designations. The project’s code name was Archangel, but Kelly Johnson referred to the aircraft as the “Article”. Later the SR-71 was known as Habu, Lady in Black and the Sled. Most know it only as Blackbird.

 The development of the SR-71 is an amazing story of engineering and construction.  It required the invention of several technologies to achieve its design goals – existing technology and materials would not work. One key to success was the Pratt & Whitney J58 engine. The J58 was a unique design developed expressly for the SR-71.  The engine worked both as a conventional turbojet but also, at high speeds, as a ramjet.  Flight in excess of three times the speed of sound required modification to the engine air inlets. Lockheed engineers created a combination of “spikes”, bleed tubes and bypass doors to control the speed of air entering the engines. The J58 engine also required a special fuel, JP-7. This fuel does not ignite in the conventional manner, so a highly combustible compound called Triethylborane (TEB) was used to light the engines Fuel consumption at such speeds is very high and was carefully managed, often with several air-to-air refuelings during each flight. The J58 was designed to operate with continuous afterburner power, and at maximum speeds 70% of power is provided by the afterburner. Curiously, fuel consumption improves at high speed.

 Friction with the air heated some parts of the SR-71 to 900° F. As a result it was necessary to use a titanium alloy for most of the aircraft’s structure. Titanium is difficult to work with and can’t be forged, thus each SR-71 was essentially hand-built. Ironically, the prime source for titanium imports during the SR-71’s construction was Russia, a nation the Blackbird would spend much of its service career observing.

 Modern aircraft use bladders to hold fuel, but these add weight that reduces performance. In the SR-71, the fuel tanks are integral to the aircraft. Since it was impossible to provide a perfect seal, fuel leaked while the aircraft was on the ground. Once airborne, heat caused the aircraft to expand and close the openings.  Fortunately, since the high-performance JP-7 fuel was difficult to ignite fuel leakage posed no danger to aircraft or aircrews on the ground.

 The SR-71 was one of the first aircraft to include design features meant to reduce its radar signature.  In order to provide a measure of stealth the engineers designed certain parts to reduce radar reflections and used a radar-diffusing paint . The paint used is a dark blue which appears to be black, giving the aircraft the name Blackbird. The afterburning J58 engines produced a huge infrared signature, and a cesium based fuel additive was used to make the SR-71’s exhaust more difficult to detect.

Stealth, however, was secondary to performance in determining the SR-71’s remarkable survivability.  No interceptor aircraft could reach the SR-71, and over 4,000 missiles were fired at it during its service history—with no hits.  Standard evasive procedure for the SR-71 upon detection of a missile launch was to merely accelerate away.

The atmosphere at 80,000 feet is extremely thin, and as a result full pressure flight suits were necessary. The suits developed for the SR-71 were later adapted for use by space shuttle astronauts.  The SR-71’s cockpit was pressurized and air conditioned (the inside of the windshields could exceed 200° F during high speed flight), but if ejection was required the suits were the only thing between life and death.                       

At airspeeds of over 30 miles per minute, accurate navigation is critical to a successful mission. The Air Force modified an Astro-Inertial Navigation System (ANS) first developed for missile guidance for use in the SR-71.  It was unique as it was able to detect a series of stars by day or by night and track them in flight through a small quartz window in the top of the fuselage. The information was fed into a special navigation computer that guided the aircraft.

 Each SR-71 was equipped with a range of electronic and optical sensors to gather and record intelligence required for a particular mission. These included optical and infrared cameras, radar, and electronic detectors. In addition the aircraft was equipped with defensive equipment to protect it from missiles and fighter aircraft, and extensive recording systems to capture data for analysis upon return to base.  The SR-71 was not equipped with systems to download data in flight until nearly the end of its career.

The SR-71 carried a two man crew, a pilot and a Reconnaissance System Officer (RSO). There also was a large support crew at each SR-71 base, and a large contingent of air tankers modified to carry JP-7 fuel were assigned to support the Blackbird. The SR-71 served our nation proudly for 26 years, flying for six different Presidents and being a key component in winning the Cold War. Officially retired in 1990, this magnificent aircraft now resides in 30 different air museums around the country.


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