U-2 Avionics Technician explains why Dragon Lady pilots breathe pure oxygen for as much as 14 hours straight

U-2 Avionics Technician explains why Dragon Lady pilots breathe pure oxygen for as much as 14 hours straight

By Dario Leone
Feb 9 2024
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The U-2

Built in complete secrecy by Kelly Johnson and the Lockheed Skunk Works, the original U-2A first flew in August 1955. Early flights over the Soviet Union in the late 1950s provided the president and other US decision makers with key intelligence on Soviet military capability. In October 1962, the U-2 photographed the buildup of Soviet offensive nuclear missiles in Cuba, touching off the Cuban Missile Crisis. In more recent times, the U-2 Dragon Lady has provided intelligence during operations in Korea, the Balkans, Afghanistan, and Iraq. When requested, the U-2 also provides peacetime reconnaissance in support of disaster relief from floods, earthquakes, and forest fires as well as search and rescue operations.

U-2 print
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The U-2R, first flown in 1967, was 40 percent larger and more capable than the original aircraft. A tactical reconnaissance version, the TR-1A, first flew in August 1981 and was structurally identical to the U-2R. The last U-2 and TR-1 aircraft were delivered in October 1989; in 1992 all TR-1s and U-2s were designated as U-2Rs. Since 1994, $1.7 billion has been invested to modernize the U-2 airframe and sensors. These upgrades also included the transition to the GE F118-101 engine which resulted in the re-designation of all Air Force U-2 aircraft to the U-2S.

U-2 pilots breathe pure oxygen for as much as 14 hours straight

Despite all these upgrades, one thing that hasn’t changed much at all over the years is oxygen.

U-2 Avionics Technician explains why Dragon Lady pilots breathe pure oxygen for as much as 14 hours straight

‘[U-2 pilots] breathe pure oxygen for as much as 14 hours straight,’ Damien Leimbach, former USAF Avionics Technician on U-2 aircraft, says on Quora.

‘The plane flies at extreme altitudes (above 70K ft) which many people know. What most people don’t know is that the cockpit is not a pressure vessel. Look at the three panels under the windscreen in this photo.

U-2 Avionics Technician explains why Dragon Lady pilots breathe pure oxygen for as much as 14 hours straight

‘Opening any of those up would allow a maintainer to look directly into the cockpit. The only thing holding the air inside is a thin smear of sealant, and some screws for the panel. As a result, the cockpit is only pressurized to the equivalent of about 29k ft, which for reference is roughly equal to standing at the top of Everest.

‘Why? To save weight. Putting a pilot in a space suit weighs less than building a pressure vessel into the plane.

U-2 pilots pre-breathing pure oxygen

U-2 Avionics Technician explains why Dragon Lady pilots breathe pure oxygen for as much as 14 hours straight

‘You see that suitcase close to them? Yeah, that’s not their spare underwear and a toothbrush. It’s a liquid oxygen supply. They just spent an hour or more like this,

U-2 Avionics Technician explains why Dragon Lady pilots breathe pure oxygen for as much as 14 hours straight

‘pre-breathing pure oxygen to purge his system of nitrogen.’

As highlighted above, one thing that hasn’t changed much at all over the years is oxygen: in fact, pre-breathing took place in the 1950s just like it takes place today.

Leimbach explains;

‘Just like scuba divers, rapid decompression in an emergency could cause the bends. So, the pilot will spend an hour or two before a mission taking a nap and breathing pure oxygen, then hooking up to the LOX case for the ride out to the jet, where PSD (physiological support division) will then connect him to the liquid oxygen supply on the jet. Then they get to spend the next 8–12 hours continuing to breathe pure oxygen during the mission. They do NOT mix the pure oxygen with air. That would defeat the purpose of the nitrogen purge. Anyone suggesting that this is somehow harmful or fatal to pilots needs to stop relying so much on bots so write her answers.

‘Here is a crew chief servicing the LOX tanks on the U-2.’

U-2 Avionics Technician explains why Dragon Lady pilots breathe pure oxygen for as much as 14 hours straight

Photo credit: Staff Sgt. Kenny Holston, Airman 1st Class Luis A. Ruiz-Vazquez, Senior Airman Colville McFee, SrA Andrew Buchanan 9th Reconnaissance Wing Public Affairs / U.S. Air Force and Lockheed Martin

U-2
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Dario Leone

Dario Leone

Dario Leone is an aviation, defense and military writer. He is the Founder and Editor of “The Aviation Geek Club” one of the world’s most read military aviation blogs. His writing has appeared in The National Interest and other news media. He has reported from Europe and flown Super Puma and Cougar helicopters with the Swiss Air Force.
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