military

SR-71, KC-135Q and JP-7

If not for air refueling, the SR-71 Blackbird’s range would be relatively limited to about 2,000 NM. The aircraft’s range was increased by several air refuelings, reaching the crew’s endurance limit. A few missions have gone above 12,000 NM. The SR-71 and KC-135Q tankers’ forward basing allowed for increased overall efficiency, shorter range, shorter length missions, and faster response.

There were various ways in which KC-135Q crews and their aircraft were different from other Air Force crews. Their boom operators were the only ones qualified to refuel the SR-71, and their aircrews were the only ones qualified for Blackbird’s specific radio-silent rendezvous procedures. The Q-model tankers could transfer JP-4 and JP-7 fuel between different tanks because of the special plumbing between the fuel tanks. They may use JP-4 or JP-7 fuel in their engine. If the SR-71 landed in an area without JP-7 fuel, the Q-model tankers would fly in with the fuel and refill the aircraft using ground-based transfer hoses.

How to get better gas mileage in an SR-71 Blackbird flying at Mach 3

David Peters, former SR-71 pilot, describes how to get better gas mileage in a Blackbird flying at Mach 3.

‘We had some gimmicks we used to make fuel. Each plane was different, but the techniques were very close. As soon as we started the climb away from the tanker, I would select tank two manually and even sometimes go to manual aft transfer to get the CG aft as soon as possible. After leveling off at Mach 3, I would get the CG situated where the trim was at zero for a slight cruise climb thus eliminating induced drag. Next, I would have the aft doors in A position and manipulate the speed to close the forward doors as much as possible without creating an unstart. This might be anywhere from 3.0 to maybe as high as 3.04 or 5.

‘Much of this was dependent on the outside temperature. If it was colder than standard, you could do even better. Hotter than standard not so good but always better than the plan. Using these techniques and a few more I would often see fuel flows below 3600 lbs/hr/per engine at Mach 3. Ed and I rarely came back from a mission with less than 5,000 lbs more fuel than the flight plan called for. There are a lot of those things involved. Flying the SR required a great deal of stick and rudder abilities under some circumstances but I always told people it was primarily a cerebral machine. You had to have a very deep understanding of how it worked to get the job done.’

Skill and knowledge

Peters concludes;

‘I have said many times before, much to the contrary of the engineers, that DAFICS [digital automatic flight and inlet control system] really screwed up what the airplane was capable of just like everything we seem to do anymore, it took the skill and knowledge of the operator pretty much out of the equation. But that is another discussion.’

Check out Habubrats SR-71‘s Twitter profile and Born into the Wilde Blue Yonder Habubrats‘s Facebook page for further Blackbird photos and stories.

Photo by David Peters and TSgt. Michael Haggerty / U.S. Air Force

The Blackbird

Developed from the Lockheed A-12 and YF-12A aircraft, the SR-71, sometimes known unofficially as the “Blackbird,” is a long-range, advanced, strategic reconnaissance aircraft. The 4200th (later 9th) Strategic Reconnaissance Wing at Beale Air Force Base, California, received the first SR-71 to begin service in January 1966. The first SR-71 flight occurred on December 22, 1964. On January 26, 1990, the US Air Force (USAF) retired its fleet of SR-71 aircraft.

For almost 24 years, the SR-71 held the record for being the fastest and highest-flying operational aircraft in the world. It could cover 100,000 square miles of the Earth’s surface per hour from 80,000 feet. The Blackbird’s extraordinary capabilities allowed it to gather intelligence in some of the most hostile environments.

SR-71 Blackbird Mission on the day of the Chernobyl Disaster

Former SR-71 RSO, Lt. Col. Doug Soifer, recalls in Richard H. Graham’s book SR-71 Revealed The Inside Story;

‘Mike Smith and I were TDY for our first time to Mildenhall for our normal six-week rotation. We went to the Det one morning to fly a routine six-hour sortie—the Barents and the Baltic. During the preflight briefings, the intelligence officer said a nuclear power site (Chernobyl) in the Soviet Union had an accident a few hours earlier. They had no other information on it yet. The weather briefing officer gave his normal briefing but also mentioned they double-checked with the weather service at Offutt AFB that we would not fly through any of the fall-out from Chernobyl. With the briefings done and no one concerned about our route of flight, we went to the jet and flew a normal mission.

‘The normal routine after an operational mission is to land and continue to taxi off the runway and directly into the hangar so they could download the mission take. But as we landed and turned off the runway, we were told to stop way before the hangar. We both thought this was very strange and couldn’t understand why we were stopping here. Then one person, and only one, dressed in very funny-looking gear, came walking up to the plane.’

Soifer continues;

‘As he got closer, we could see he was in full chemical gear and had a Geiger counter. After they had guaranteed Mike and I that we were in no danger of through radiation from Chernobyl, they were checking the plane before any of THEM would get close to us! Once he walked about the plane with the Geiger counter, we were allowed to continue to taxi into the hangar.’

Photo by NASA and Unknown

The SR-71 Blackbird

A group of Lockheed members led by Clarence “Kelly” Johnson—then vice president of Lockheed’s Advanced Development Company Projects, also referred to as the “Skunk Works” and currently a part of Lockheed Martin—designed the SR-71, the most sophisticated Blackbird—including the A-12 and YF-12.

Beginning in the late 1950s, the A-12 reconnaissance aircraft—which made its first flight in April 1962 and remained classified until 1976—served as the model for the Blackbird. The YF-12A interceptor variant was first made public by President Lyndon Johnson on February 29, 1964, which was more than six months after it made its first flight. On December 22, 1964, the SR-71’s maiden flight was completed.

The Blackbird was built to reach altitudes of up to 85,000 feet and cruise at “Mach 3+,” faster than three times the speed of sound, or more than 2,200 miles per hour.

Checking out in the Blackbird like a cowboy

Col. David P. Dempster, Blackbird Reconnaissance Systems Officer (RSO) who was also part of the first US Air Force (USAF) contingent to fly operational SR-71 reconnaissance sorties from Okinawa into “denied areas” (the term “denied area” was referred to a specific area over or around a foreign country where you could encounter anything and everything… from MiGs to SAMs), recalls in Richard H. Graham’s book SR-71 Blackbird Stories, Tales and Legends:

“Jim Watkins was a great pilot to be crewed within the Blackbird. A Texas cow-boy who raised horses in his off time, Jim loved, breathed, and lived for flying.

“But, like his horses, he ‘felt’ and handled them with cowboy common sense. Imagine checking out in the Blackbird, a World War II B-24 pilot who flew fighters, transports, KC-97 tankers, and KC-135 tankers at Beale. In tanker, Jim was on the initial OXCART team and provided the air refueling support for the A-12s flying from the Ranch. Jim checked out in the SR-71 like a cowboy putting on an old familiar leather glove!

“We were honored to be among the four SR-71 crews selected to deploy for the first time to Okinawa in March 1968. On 21 March, the first operational sortie flew and the crew encountered a double-engine flameout during descent to their tanker as they exited the target area. After refueling, they returned to Okinawa. A week later the second operational sortie flew, and again, with a different crew and different Blackbird, they encountered the same double-engine flameout at the start of their descent. They landed in Thailand due to the left generator not working. What was happening? Both planes checked out good on the ground after landing and we had lots of jaw-boning among ourselves and with Lockheed tech reps, with no conclusions.

KC-135Q saving an SR-71 over Laos

“Then, on 19 April 1968, Jim and I launched on the third operational sortie (the first for us and Crew Chief Technical Sergeant Bud Martin’s #974). We zipped through the target area with no problems and began the start descent checklist. As Jim pulled the throttle back to the rpm setting called for in our procedures, we had a double-engine flameout. Excitement, adrenaline pumping, and we dropped like a rock into Northern Laos! Jim got both engines started around 30,000 feet, and we headed south. 

“Our [KC-135Q Stratotanker] tanker, the real hero of this story, saw our rate of closure on him stop. He knew what had happened and headed north immediately, unprotected, into enemy territory and rendezvoused with us. Refueling with him, we headed back into Thailand and proceeded to our preplanned end refueling point.

“What to do now? We were scheduled to go back to the target area for another ‘hot loop.’ Over the intercom, I heard this commonsense cowboy say, ‘Dave, I think if when we start our descent, we hold a higher-than-normal rpm we can avoid the flameouts. Want to give it a try?’ ‘Sure,’ I answered. We accelerated back to Mach 3-plus and on course into the target area. We eyeballed adding about 30 miles to the start descent range and when the time came Jim’s theory worked perfectly. No flameouts and a smooth descent.

‘Ichiban,’ the ‘number one’ Habu

“What was the secret and why did this work? The answer turned out to be the way the engine’s fuel controls were programmed. They used standard adiabatic lapse rates, which engineers all over the world assumed depicted the height of the tropopause and outside air temperatures at varying altitudes. WRONG! What we discovered was that in Southeast Asia, the tropopause (and magnificent thunderstorms we would look down on) could go as high as 65,000 feet, rather than the textbook 55,000 feet. Moreover, the air was much colder. Lockheed and Pratt & Whitney Co. eventually reprogrammed the fuel controls correctly and the problem went away. In the interim however, all of the crews adopted the cowboy’s technique and the flameout problems disappeared.

“The day after this flight Jim, Technical Sergean. Bud Martin, and I proudly stenciled the first Habu on the side of #974, which went on to be so successful that it was dubbed ‘Ichiban,’ the ‘number one’ Habu in the 1968 period on Okinawa.”

Photo by U.S. Air Force