Spy Docs: The Difference Between the A-12 and the SR-71

Ever wonder what the real difference between the CIA’s A-12 Oxcart Mach 3 spy plane and its legendary successor, the Air Force’s SR-71 Blackbird?

Well, these declassified documents from 1967 compare the two jets performance side by side. Basically, the Blackbird could carry a lot more spy gear and electronic countermeasures than the A-12 could. What Specifically could the SR-71 carry that the A-12 couldnt?

Here’s a quick breakdown.

On a single mission an SR-71 could carry:

  • two “technical objective cameras”
  • two “operational objective cameras”
  • one “terrain objective camera”
  • one “high resolution” side-looking radar
  • one infrared camera
  • one electronic and communications intelligence-gathering package
  • three electronic warfare (countermeasures) systems, “CFAX, APR 27 and System 13C”

While the A-12 could carry some of this gear individually, it had to swap out particular sensors per-mission, according to the report. This meant that the A-12 was lighter and could fly 2,000 to 5,000-feet higher than the SR-71 at comparative speeds. Still, this wasn’t enough of a performance gain to warrant keeping the Oxcarts in service alongside the Blackbirds whose increased sensor loads and better countermeasures made them more useful and survivable than the A-12s, according to the documents.

Click through the jump to read the report.


  • Richard S.

    I know there isn’t really another need for one, but I would love to see another mach 3+ spy plane come out. Mach 5+ if they could. It’s not about need for me, it’s about the United States flipping the Chinese and Russians the bird and daring them to stop the flyovers.

  • coolhand77

    Officially the SR71 could do Mach 3+. Unofficially I heard rumors they had them up around 5+

  • Dfens

    What the hell kind of country is this that would retire the SR-71 and keep that POS U-2? It’s sure as hell not the country I grew up in.

  • Mike

    I’ve lived outside Beale AFB all my life, and grew up with the SR-71 flying by almost daily. I also heard the high-Mach rumors, but was told by someone that I know and trust, that the rumors were false…mach 3.2 was, and still is, the SR71’s top speed. And isn’t that fast enough for anyone wanting to do a photo-recon run? Nawwww…..

    • Technoweapon

      Speed was for evasion. I imagine it had to slow down, shoot the photos, then get the hell out ASAP before interceptors ate your lunch. 3.2 is incredibly fast.

      As I remember it the SR71’s plates, pipes, wires, etc, would all expand greatly due to the heat of friction at max speed. This caused high maintenance costs and long downtimes for the crafts that hit above Mach 3.

      Rumors are still false. Due to our materials we’re stuck in the realm of Mach3. But it’s only a matter of time. We’ve hit Mach5 but only for moments before destruction. So the speed is there.

    • exLoader

      ….not if your taking picture from the edge of the atmosphere. How fast do you think a satellite moves ??? Do you think they slow a spy satellite down to take a snap shot ?? Not likely. Those kinds of aircraft and satellites are not the Top Secret part, it’s the technology of those cameras.

  • Kurt

    I’ve always been curious about the “A” prefix for the A-12. Doesn’t “A” mean attack, as with the A-10 Warthog?

  • Charlie

    The Mach 3 number is less than the 71’s aerodynamic design limit.

    • bevel450

      Not true.

      The immediate problem with such a claim is thermal. Heat soak from that 500-700F skin ( depending where it is on the airframe) is the real issue.

      Heat soak…a reality

      • W.R.Monger

        I work in the aerospace industry and 8 years ago I’d have a agreed that the thermal problems would prevent faster than Mach 3.5 (to .7ish) but there have been an explosion of new heat resistant/heat wicking/heat transference materials on the market. I personally made composite parts that could withstand turbine exhaust temps and pressures of 800 F to 1100F consistently for exhaust systems so the 5+ barrier is a matter of money.

        Why go faster than a little more than an enemy if it costs a lot more but doesn’t give you an advantage that you don’t already have? I’m sure this is the reasoning for not pushing the envelope on this. I even had the opportunity to work on a Mach 15+ power plant project which works but has no airframe to attach it to.

        It all comes down to money and what returns we will get from it.

  • blight_

    For meaningless armchair giggles and apples to hearts of romaine comparison, compare the J58, F119 and F135.

    • W.R.Monger

      i had a unique opportunity to see the F119 being tested in Florida at the Pratt & Whitney plant there. they burned that engine day in and day out constantly. at night it was pretty cool to see the sky light up when they hit the afterburner especially from teh top of the project we were working on at teh time. had a front row seat to a shuttle launch as well high above the treetops on our test cell. good times, good times…

      also at the airfield where we built our test bed there was a J85 there that had a thrust diverter on it and it kicked out flames 90 degrees from exhaust (had titanium guide vains that diverted the thrust), that was pretty cool to see as well even though it was pretty much ancient technology :)

  • Black Owl

    Sometimes I wonder if the SR-71 was ever capable of delivering a nuclear warhead and no one talked about it. The idea of being able to drop a bomb at mach 3+ without being touched must have been something that would strike fear into the Soviets and probably pushed them to make the MiG-25 Foxbat.

  • blight_

    I didn’t think that they did RCS testing at Groom Lake, but went looking, and found an interesting gem:

    • Smeghead

      Oh, is that what they’re up to in that photo? I was wondering what the hell they were doing to the aircraft, being upside down and all.

      Great pic!

  • Societyinadownfall

    Its amazing how we defeated Russia by pretty much outspending them during the cold war. Now history is repeating itself and we are defeating ourselves by spending more than we make.

  • johnysmith

    As pilots we are always interested in aircraft, and in particular unique and interesting aircraft. The SR-71 is one of the most fascinating aircraft ever build. http://airsoc.com/articles/view/id/4f717b6ec6f8fa

  • deleted6399689

    A late friend of mine worked in the Skunkworks on everything from P-38’s to the A-12 / Blackbirds and retired in the ’70s. He had a lot of cool stories to tell and some he wouldn’t. I asked him one day. long after he retired, how fast the SR-71 would go balls out. He said “I don’t know and I’m not sure there are more than a dozen people that really do, but I installed the Mach meters in all of them and the meters will read over Mach 4.”

    • bevel450

      Well, lots of us worked out there and many dozens flew the aircraft. The only time the plane ever went Mach 4 was during drinking sessions with Navy pilots.

    • Bealevet

      My boss at Beale AFB in 1989 was a crew chief on the SR. After SR flights they had to go to debriefs where the pilots and support people (Life support, Avionics, etc) were briefed on the flight in general. One of the questions always asked was max speed due to different inspections that were required depending on the speed reached during the mission. On one flight the pilot was asked his max speed. Instead of replying mach 3, 3.1, 3.2 as per normal, the pilot looked around the room and told the debriefer “I’ll speak to you after the ‘brief, but mach 4+”.
      I unofficially was told this by multiple sources over the years, that the SR was taken to 4+, but the big problem was it always required intensive inspections after such a high speed run and was not at all encouraged. Basically if you had to do it, do it. But try not too.

      • 16a65nana156351cfcongratulations Laura, as usual you came up with something beuutifal that photographs so well. i love. everything you do, but, would love to see you do a layered acrylic album with pages that interact with each other like the anatomy charts on transparency paper in the encyclopedia that show a little more when you turn the page. i think that would be awesome. keep doing what you do. i love all your work nana 156 146

  • matheusdiasuk

    The photo looks like a Naboo Star Cruiser from Star Wars new movies.

  • authormjlogan

    In a rather hair raising flight in 1986, the blackbird outran Qaddifi’s missiles at 1.6 miles per second. Do the math, that’s well beyond M3.2. Speed of sound is 1,126 ft/s or 768 MPH. I’m sure this speed is unofficial and undocumented, but the source is http://all-things-aviation.com/aircraft/the-black

  • Stratege

    A-12 and SR-71 were the great engineering achievement of that time. But those birds wasn’t “wunderwaffe” after all.
    Blackbird with its relatively huge radar signature and straightforward manoeuvrability was not survivable against Soviet air defenses such as S-200 / SA-5 SAM (Mach 4 / 35 km max height / up to 300 km max range)

  • Lance

    Its a pity that the U-2 lived on and the Blackbird died to politics in the early 90s may it live on in legend.

  • BobSacamano

    This may have been addressed, but to my understanding the A-12 was a single seater, while the SR-71 was crewed by a pilot and RSO…

  • kim

    Just like the 200 mpg carburetor.

    • bevel450

      Precisely. And I am sure that all of the enthusiasts above, have got one of those carburetors as well !

  • RSweeney

    More proof that looking good is the same a flying well.

    Is there a better looking aircraft in history?

    • gkam44

      The XB-70, the White Beast was equal in admitted speed, and much larger. Sometimes I would go out the side door of the hangar, and find myself almost under it. They would walk it our the day before flights and park it there before flights.

      • Guest

        That was cool, but, I still think the SR71 is the baddest looking plane of all time. Just MHO, that’s all. :-)

  • jcallends

    Where can I see the inner workings of an SR-71 engine?

  • jhouse

    The Blackbird used to regularly fly over North Korea in the 80s (and perhaps beyond). The North Koreans tried to shoot it down every time but the closest they ever got was miles away. It was basically like throwing a rock and tring to hit a bat with both eyes closed.

  • gkam44

    There are other differences in the birds that let us differentiate between them. The YF-12A had a drop-down vertical stabilizer that folded up to the left before landing.

    The chines (the flaring sides), went all the way to the nose for the SR, as in the picture, but only to the nosecone for the YF-12A. There were two on the ramp at Edwards a few years ago I spotted with satellites.

    We had all three variants at Eddies Airplane Patch 1966-67,and to see one flying with the XB-70 was a sight I could never forget.

  • gkam44

    I have a poor photocopy of the Operations Manual for an SR-71 in digital form.

    Anyone want a copy?

    It may take a day to find it. Or you could google the phrase SR-71 Operations Manual,

  • Ben Hazi

    Sad that they were decommissioned. I mean these are technological marvels , the US should have kept at least a few of them because who know what other roles they might be able perform. But in the end they just cost too much to maintain and that’s what every expensive aircraft face.

  • ChadManAST

    Why is the plane upside down in the picture?

  • Jill Trotchie

    please u lnow what kind of spies i was thinking about-hikers

  • Danny Ross

    Great things just sometimes become obsolete. My guess is that, however fast the SR-71 went, or however high it flew, it was made obsolete by military satellite technology. You put up a satellite and it sits there, observing, until it dies. For a discussion of a possible replacement for the Blackbird, try http://www.spyflight.co.uk/The%20Future.htm

  • Craig

    I worked on the SR-71 at Edwards on the test force from 67 to 69. The max speed of the a/c was “CIT limited”, that is ‘compressor inlet temperature’ Above that speed/temperature the compressor turbine blades start coming apart. We did all the testing, an the max that I saw on the charts that came back were 3.325 mach. People said it could go mach 4 or 5 is a bunch of bull. The idea that you could fly a lot higher is also bull. You might be able to zoom to 95 or 100k but it then has a cost also – that means gas, range, speed, down alt after the zoom might be 60k. The a/c is a camera platform, it is not a fighter.
    Should we still have the SR because everything has an associated cost. We did not build many of these aircraft. Kind of like AFone should the president have a 747 or a Gulfstream or maybe a Cessna 182. A limited budget makes decisions for you in one area and then forces your decision in another area.

  • Rob M

    Yeah, I don’t really understand the motivation of people trying to pretend the thing needed to go mach 5+ and there must be a big conspiracy blah blah blah.. you hit it on the head when you said it wasn’t a fighter. It was optimized for a specific purpose, was gossamer delicate, and had to fly within narrow limits to avoid damage or destruction. As for the conspiracy stuff, it is trackable on radar despite the relatively narrow RCS, so just go ask the thousands of radar controllers all over the world spread throughout many different countries, friendly, enemy and neutral alike if they are all “not authorized to disclose the speeds” they witnessed. Jesus Christ..

  • jerry griffin

    what happened to the new plane/wing concept that could not-would not stall. last I heard the inventor’s had no offers from the u s gov’t and had sold the design concept to a radio-control plane manufacturer

  • BobThe Dog

    As an ex-BUFF-Keeper, and lifelong aviation enthusiast, I am more than sick to death of this jingoistic horsehockey bestowing every capabitltiy on the Blackbird short of warp drive. Per the late, great Kelly Johnson himself, 3.3 mach, with a 3.5 “option”, after much re-work on BOTH(!!!) airframe and engines, WAS IT!! As a feat of engineering, the aircraft stands on its own extraordinary merits and needs no further embellishment. BTW, given the fact, per “Moore’s Law”, that its far easier to increase the speed of a fire control computer than an entire aircraft, as demonstrated by an F-15 intercept of the ultimate “high/fast target” a used up recon SATELLITE!!!!, speed is now moot.

  • Danny

    I have often wondered if the Beatles song “Black Bird” was about the SR-71. Anybody know the answer?

  • My brother suggested I may like this blog. He was once entirely right.
    This post actually made my day. You can not imagine just how a lot
    time I had spent for this information! Thank you!

  • BobTheDog

    Another point, not usually mentioned in go-arounds such as this about Blackbird capability is that BOTH(!!) it and the MiG-25 started out on the same shaky ground in that, in each case their engines (J-58 and R-15 respectively ) were never intended for the performance that would be demanded of them, and could not be used for either mission without first being modified beyond literally recognition. The Blackbird was lucky in that, even though they weren’t ready for the first test flight, requiring a temporary substitution of J-75’s, the folks at P&W did finally get all the bugs ironed out of the J-58 before its entry into service. The MiG was not so lucky, having to soldier on with deficient power plants, the real reason it only was able to gaze at the SR-71’s “tail lights” getting smaller, fast! Which makes me wonder if anyone has heard about a final version of the Mig’s R-15 engine, the “I coulda’ been a contender” R-15BF2-300, which not only had ALL(!!) its previous shortcomings resolved but also offered the bonus of THIRTY(!!!) percent more thrust, and with which the Foxbat, with a few airframe mods to accommodate the higher temperatures, like Wile E. Cuyote on ACME leg vitamins, (my favourite episode of that entire series), would have given the “roadrunning” Blackbird some serious competition? As I hear, they only slammed the new engine into a couple of stock airframes to see what it would do, set a couple of zoom climb to absolute altitude records, and then cancelled it in favour of the more electronic-capable Mig-31, Moore’s law carrying more weight (bad pun intended). Also, as regards SAMs, the issue was never the missile’s speed as NO(!!!) man-carrying air breather is going to ever “outrun”(??) a rocket propelled ANYTHING!! It was rather the inability of the primitive, and slow soviet fire control computer in the ground-based guidance system to correctly calculate the proper lead angle so that the SAM and the Blackbird arrived at the same place/altitude at the same time causing the missile to arrive at the required height but way behind the “target”, necessitating a “looping over-to-tail chase”, at which point the SAM simply ran out of fuel before closing the gap. Which is a completely different scenario from literally enjoying superior speed of flight altogether, as has been claimed not withstanding SAM capabilities of mach 4+!

  • BuffKeeper

    Having seen any number of sources noting that the rate at which aerothermodynamic forces (aka HEAT!!!) increased with even the slightest increase in speed, from a mere 17 deg at 707/747 cruising speed, to 267 deg at the “mere” 2.05 mach of the Concorde, to 550+deg for the mach 3.0 B-70 Valkyrie, to over EIGHT HUNDRED(!!!!) deg at just the 3.3 acknowleged for the Blackbird, coupled with the frank admission by the folks at P&W that, upon ANY(!!) exceeding of the max compressor inlet temp (427 deg centigrade, the other numbers were farenheight), usually reached at around mach 3.25, they “could NOT(!!!) guarantee the structural integrity of the engines” , aka KA-BOOM(!!!), coupled with Kelly Johnson’s noting the sheer magnitude of cost and effort required to just get to mach 3.5 from the Blackbird’s established cruising speed, I must to having some trouble swallowing all these “tales” crediting what is indeed an absolutely marvelous craft in its own right with every capability from SSTO to warp drive. Simply because the instruments were calibrated to more than cover the flight envelope does not prove the actual extent of it, and, BTW, I would suspect the reason the A-12 is upside down in the photo is that it was the way craft were mounted on the pylon for stealth testing, as any number of pics showing everything from the F-117 to the Raptor, also on their backs would suggest.

  • Ray

    In addition to the initial post stating the differences between the A12 and SR71 one particular item was not mentioned. The A12 was shorter had a better RCS and for this reason was stealthier than the SR71. All the leading edges of A12’s were saw tooth under the skin to redirect radar signals/pulses. Although both models had this incorporated into their design, the SR71 didn’t have them all the way to the very leading edges on the wings, and tail section and none at all in the front fuselage due to having to carry all the additional sensors that the A12 didn’t.

    • ronaldo

      Quite right. The Saw tooth design of the leading and trailing edges of the wings had composite pie shaped inserts which are transparent to the incoming radio energy. The metal element would trap the incoming wave which would not reflect back and whose energy would be disappated.