Re: Differences between A-12 and SR-71?


Message posted by Peter Merlin on August 13, 2009 at 9:11:42 PST:

The first A-12 airframe, Article 121, served as a test aircraft throughout its entire service life. It was different from the majority of the OXCART aircraft in that it retained an all-metal chine and edge assembly as well as metal inlet spikes and tail fins. Later airframes were equipped with "plastic" (asbestos-silicone) parts to enhance stealth characteristics. The first five A-12s, including the At-12 T trainer, initially flew with J75 engines because the J58 wasn't ready yet. Article 123 crashed before the J58s were introduce and the A-12T (Article 124) retained the J75s throughout its career. When the J75s were installed, the inlet spikes were fixed in place. They only needed to move during transition to high-speed cruise with the J58s and the bypass system in operation to turn the nacelle into a ramjet.

Several A-12 aircraft served primarily as test aircraft but the OXCART aircraft comprised an operational reconnaissance system. Several variants of the basic A-12 airframe were produced as the YF-12A KEDLOCK, M-21 TAGBOARD mothership, and SR-71 SENIOR CROWN.

Because the A-12 had only one crew compartment, one life-support system, and carried only one sensor, it was considerably lighter than the SR-71 and other variants. Consequently, it could attain a higher operational altitude - 90,000 feet as opposed to 85,000 feet for the SR-71 (although the SR-71 came close during Category II testing).

I might as well get the performance characteristics out of the way because somebody is bound to ask. All of the performance data has been declassified.

The maximum design cruise speed for all Blackbird variants was Mach 3.2. Speeds of Mach 3.3 to Mach 3.5 have been recorded during test flights. The speed was limited by structural temperature restrictions (compressor inlet temperature had to remain below 427 degrees C).

Fastest known flights:

YF-12A (60-6936) – Mach 3.14 (2,070 mph), USAF, official, 1 May 1965

A-12 (60-6928) – Mach 3.29 (2,171 mph), CIA, unofficial, 8 May 1965

SR-71A (61-7958) – Mach 3.32 (2,193 mph), USAF, official, 28 July 1976

The Blackbirds were designed to fly as high as 90,000 feet, but typically operated between 70,000 and 85,000 feet.

Highest known flights:

YF-12A (60-6936) – 80,257 feet, USAF, official, 1 May 1965

SR-71A (61-7962) – 85,068 feet, USAF, official, 28 July 1976

SR-71A (61-7953) – 89,650 feet, USAF, unofficial, 1968

A-12 (60-6932) – 90,000 feet, CIA, unofficial, 14 August 1965


In Reply to: Re: Differences between A-12 and SR-71? posted by Sam N. on August 13, 2009 at 4:38:13 PST:

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