Flightline: 27/TBD

"user314" (user314) 08/14/2020 at 11:00 • Filed to: flightline, Planelopnik, planelopnik history, Blackbird, SR-71, Ground Speed Check, Speed check

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The second SR-71B under construction

Of the 32 SR-71s built, two were SR-71B trainer models (s/n 61-7956 and -957) , with a raised cockpit for the instructor behind the student. These humped cockpits disrupted the airflow enough that the trainers were fitted with fixed fins under the engine nacelles to stabilize the aircraft, and as they were not operational aircraft, were not fitted with the cameras and ECM gear of the SR-71a models. 61-7956 was retired with the rest of the Blackbirds, and is now on display at the Kalamazoo Air Zoo, but - 957 was destroyed in 1968 after a double generator failure. The crew ejected safely, but the Blackbird stalled and entered a flat spin, impacting tail first and falling onto its back.

Wreckage of the second SR-71B

A new trainer was needed, however t ooling for the A-12/YF-12/SR-71s had been destroyed per USAF orders. A solution was found in the remains of YF-12A 60-6934, which had been irreparably damaged by overheating in 1966. The aft fuselage , which had been preserved, was mated to a static test article, producing 61-7981, the only SR-71C, also known as “The Bastard”.

As she had the aft sections of a YF-12, - 981 had a shorter tail cone than the rest of the SR-71s, though the folding ventral fin was removed. Also, o wing to its hybrid nature, 981 was difficult to fly at first, needing extended testing:

“ 981 took a long time to pass the acceptance testing at !!!error: Indecipherable SUB-paragraph formatting!!! because the inlets were acting so unusually. We had more than 10 unstarts on several flights and by-pass doors and spike positions were hardly ever in synch.
“I had Palmdale install a sideslip (Beta) indicator in the front cockpit because the aircraft seemed to be out of rig. Once installed, with indications of zero sideslip, the rudders needed to be trimmed out of the streamlined position and the inlets were still acting up. For the next flight, I asked to have a yaw string (made out of Nomex) placed ahead of the cockpit.

“On that mission, the yaw string was centered when the Beta indicator showed a 4 degree yaw and the rudders were then in streamlined trim. However, the inlets were still not matched in position. To determine what was wrong, Palmdale finally determined that the pitot boom was out of alignment in yaw by 4 degrees and thus feeding bad information to the inlet computers. Once they straightened the boom, 981 flew normally and we delivered the aircraft to Beale.”

-Lt Gen (Ret) William Campbell 

Despite early difficulties and her ominous nickname, the Bastard flew like the rest of the fleet after her teething problems were ironed out , and was the favored Blackbird for VIP flights early in the program. Although stationed at Beale AFB until retirement in 1990, -981 had last flown in 1976, and was added at the last minute to the “group photo” taken in February.

Group photo of 11 SR-71s. The SR-71C is at the back of the arrangement.

The Bastard is now on display at Hill AFB in Utah.

facw > user314 08/14/2020 at 11:08

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Bit of a theme this week huh?

RacinBob > user314 08/14/2020 at 11:23

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A story that I had heard/read was that some A-12/ SR-71's were having their titanium skins cracking early in their life. and in fact they may be some of the ones on static display. This was a serious issue with no known cause and a major investigation was made.

They did know that the affected planes were built in summer and so there was a dee p dive into finding the cause. The ruled out the plate material, the welders, the sticks, the weather. Everything they looked at did not make a difference.

They then reviewed the entire manufacturing process and realized that it came down to the washing of the skin before processing and t he difference between summer and off season water.....

Drum roll.... Chlorine levels. San Diego water is transported from open reservoirs and through open aqueducts . The city utility increases the Chlorine levels to assure the water was safe and the increased Chlorine was causing Chloride stress cracks. The lesson is nobody promised that this would be easy.......

user314 > facw 08/14/2020 at 11:29

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Yeah, the A-12/YF-12/M-21/SR-71 family a re too fascinating.   

PyroHoltz f@h Oppo 261120 > user314 08/14/2020 at 11:51

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The big beautiful black bastard, I love it!

PyroHoltz f@h Oppo 261120 > RacinBob 08/14/2020 at 11:53

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I believe it's LA water. They also had to develop their own cutting fluids due to a similar problem when machining the titanium.

facw > user314 08/14/2020 at 12:09

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Now imagine if we had gotten this Lockheed proposal, which clearly shares a lineage:

V ery early design concepts for what would become the ATF program, that ultimately led to the F-22 (and YF-23), though clearly Lockheed went an entirely different route than what they were sketching out at this point.

user314 > facw 08/14/2020 at 12:43

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Blackbird with retractable canards...

That’s a curious batch of designs. Obviously there was no low-observable/stealth requirement (not modern stealth, at any rate) yet, lots of canard designs though. Grumman offering an operational design based on the X-29, must be from before they decided FSW isn’t really worth it. Boeing with an A merican MiG-23/-27 and an X-31-inspired design.

facw > user314 08/14/2020 at 12:50

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Yeah, you can tell Northrop was thinking stealthy, but at F-5/F-20 scale, rather than something like the YF-23. McDonnell and Boeing have designs that are clearly the F-18 and F-15 switched into a canard configuration with wings moved back. General Dynamics just seems to have a very big F-16 (bigger even than the F-2). There is concept art floating around for a lot of these, and they do indeed look as badass as you would expect.

ItalianJobR53 - now with added 'MERICA and unreliability > RacinBob 09/04/2020 at 11:42

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I remember reading about it in Ben Rich's book