THE 456th FIGHTER INTERCEPTOR SQUADRON

THE PROTECTORS OF SAC

 

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YF-12A  #6935

The YF-12 was developed as a high-altitude Mach 3 interceptor for defense against supersonic bombers. It was designed in secrecy by a team headed by Clarence L. "Kelly" Johnson, director of Lockheed's Advanced Development Projects office--better known as the "Skunk Works." The existence of the aircraft was not officially revealed until February 29, 1964. The YF-12A was the forerunner of the highly sophisticated SR-71 high-altitude strategic reconnaissance aircraft. Unlike the SR-71, the YF-12A never became operational, but during the test program, which ended in 1966, it set a speed record of 2,070.101 mph and an altitude record of 80,257.86 feet. Both records were set on May 1, 1965. For this flight, Col. Robert L. "Fox" Stephens, (pilot) and Lt. Col. Daniel Andre (fire control officer) were awarded the 1965 Thompson Trophy.

To enable the YF-12A to withstand skin temperatures of more than 500 degrees Fahrenheit (generated by air friction), 93 percent of its structural weight is made up of titanium alloys. The aircraft also is coated with a special black paint that helps radiate heat from its skin. All aircraft components were developed especially for the environment of sustained Mach 3+ cruise.

The aircraft on display was recalled from storage in 1969 for a joint USAF / NASA investigation of supersonic cruise technology. It was flown to the Museum on November 7, 1979.

SPECIFICATIONS
Span: 55 ft. 7 in.
Length: 101 ft.
Height: 18 ft. 6 in.
Weight: 127,000 lbs. loaded
Armament: Three Hughes AIM-47A missiles
Engines: Two Pratt & Whitney J58s of 32,000 lbs. thrust each with afterburner
Crew: Two
Serial number: 60-6935

PERFORMANCE                                     
Maximum speed: Mach 3+
Range: 2,000+ miles                                                 
Service Ceiling: above 80,000 ft.

Notes

• The first YF-12A (S/N 60-6934) was converted to SR-71C S/N 64-17981
• The second YF-12A was transferred to the USAF Museum.
• The third YF-12A crashed on 24 June 1971.

PHOTOS & TEXT COURTESY US AIR FORCE MUSEUM

 

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The J58 engine was developed in the late 1950s by Pratt and Whitney Aircraft Division of United Aircraft Corporation to meet a U.S. Navy requirement. It was designed to operate for extended speeds of Mach 3.0+ and at altitudes of more than 80,000 ft. The J58 was the first engine designed to operate for extended periods using its afterburner, and it was the first engine to be flight-qualified at Mach 3 for the Air Force.

Two J58s power the highly-sophisticated Lockheed SR-71 high-altitude strategic reconnaissance aircraft as well as its forerunner, the Lockheed YF-12A prototype interceptor. In July 1976, J58 engines powered an SR-71 to a world altitude record of 85,069 ft. and another SR-71 to a world speed record of 2,193 mph.

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Because of the high-temperature environment in which the engine operates, it uses low-volatility JP-7 fuel which requires a chemical ignition system. The engine on display is a prototype version of the J58 and was used as a ground trainer before being transferred to the AIR FORCE Museum.

SPECIFICATIONS
Model: J58
Compressor: 9-stage, axial flow, single spool
Turbine: two-stage axial flow
Thrust: 32,500 lbs. with afterburner
Weight: approx. 6,000 lbs.
Max. operating altitude: above 80,000 ft.

COURTESY US AIR FORCE MUSEUM

During the development of the A-12 the Air Force asked if the Skunk Works could modify several of the A-12s into a high altitude interceptor. Kelly Johnson, aircraft designer, said "Yes, that was not a problem". The A-12 aircraft would be modified by installing the Hughes AN/ASG-18 fire control radar, design weapons bays to carry two Hughes GAR-9/AIM-47 missiles internally and space for a second seat for the fire control system operator. A ventral fin was attached under each nacelle and a folding ventral fin was mounted under the fuselage for added stability due to flight characteristics impacted by the revised nose and cockpit area to house the massive radar. This version was labeled AF-12 and later re-identified by the Air Force as YF-12. During flight testing there were several missile launches at drone targets. The most impressive launch was at mach 3.2 and at an altitude of 75,000 feet at a target 36 miles away and at 1,500 feet with a direct hit on the Boeing B-47 drone. The missiles were moved out of the weapons bays and into the air stream on a device called a trapeze, and then fired. The Air Force never issued a production contract for the YF-12. It was the opinion of many in the Johnson administration including Secretary of Defense Robert McNamara that there would never be a need for a high altitude intercept capable aircraft. That is, until the soviet Backfire bomber showed up....too late for the YF-12. In one of Kelly Johnson's speeches I was fortunate enough to hear him lament, "every day a high altitude penetration of U.S. airspace occurs and we do not have an aircraft with the ability to fly up and eyeball the threat, including F-14 and F-15 fighters, and this aircraft carries women and children...the Concord SST".

During flight testing several A-12s were lost, but the testing continued on both the YF-12 and the A-12 aircraft. Mach 3.0 was routinely broken and many speed records held by Soviet aircraft fell. However, these records could not be made public due to the secrecy of the program. The Department of Defense decided to take back the records from the Soviets. On May 1, 1965 two YF-12A aircraft set the absolute altitude record of 80,258 feet, and a speed of 2,070 miles per hour on a closed course. During continued flight testing an A-12 exceeded mach 3.28 at 90,000 feet altitude. On December 21, 1966 an A-12 piloted by Lockheed test pilot Bill Park covered 10,198 statute miles in six hours.

Editors Note: The YF12A Development data was written by Dennis Edelbrock and gleaned from his great web page "Home of the Skunk Works".

  COURTESY OF  Leland R. Haynes    "SR-71 Blackbirds"

 

YF-12A Tail number/ build number

 

6934/ #1001   

Lost on 14 August 1966 (some sources say 14 July 1966), at Edwards AFB, CA. Seriously damaged during a landing at Edwards. The rear half of the YF was fused with the front half of the SR-71 static model to make the SR-71C #64-17981.

6935/ #1002    THE ONLY REMAINING YF-12A

On display in Annex of USAF Museum, Wright-Patterson AFB, DAYTON, OH

 

The Mach 3 Interceptors:

 

YF12A  #60-6934  LAC#1001

 

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	This Lockheed photo was the very first one published of ANY blackbird.  Until 2 YF-12s were unveiled at Edwards AFB in late 1964, this was all that anyone knew about the blackbird.

This Prototype was the 1st YF-12A and performed it's maiden flight on 7 August 1963. On 28 September 1965 flying at Mach 3.2 and 75,000 feet, #934 fired an AIM-47 missile at a target Q-2C Drone destroying the Drone at 20,000 feet. Again on 25 April 1966 flying at Mach 3.2 and 75,000 feet, #934 fired an AIM-47 missile at a target QB-47 Drone destroying the Drone at 1,500 feet! YF12A #934 aircraft was seriously damaged during a landing at Edwards AFB. It was placed in storage in Palmdale, California. The rear half of #934 was later used to build the SR-71C #64-17981 trainer which flew for the first time on March 14 1969.

 

The YF12A #934 Activity and DOD Cancellation of Program

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Another photo of 934, taken during the same flight as the one above - Lockheed photo via Tony Landis

F12A #934 was one of Bob Eaton's Aircraft while working for the Lockheed Skunk Works in the early 1960's. He has graciously provided some insight into the activity of this Interceptor. The following data is provided to acquaint the reader with an in-siders view of this unique Blackbird:

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934 was severely damaged as a result of internal systems overheating during a test flight from Edwards AFB on August (or July) 14, 1966.  The airframe remained intact but the damage to internal systems was beyond repair.  What happened to the forward section is anybody's guess, but the aft end lives on as part of SR-71C #981.

Back in the days when there was an Air Defense Command, General Agan was lobbying for a replacement for the F106. The YF was so successful that we were given a follow-on contract to up-grade one of the A/C (#934) to be a YF12A/B, prototype for a production fighter called the F12. The production contract was to be for 200 airplanes! #934 was, with engines and outer wings removed placed back on the delivery trailer and transported back to Burbank, California. There it was to be given a flat nose (like ASAR) because Hughes had developed a new antenna that could operate in an enclosure close to the original design contours of the "A" & "SR-71" noses. It was actually to be an SR-71 converted to a Fighter/Interceptor in its final configuration. There was going to be a big buy of these new Interceptor type fighters, the F12. As part of the work the airplane was placed back in the jigs and was unmated at station 715. Lo and behold the Department of Defense (DOD) Whiz kids prevailed. These people canceled the YF program in its entirety. Gen. Again resigned under protest of McNamara's treatment of the program. It was replaced by the F106, what they already had in service. This was cheaper and allowed them to waste more money on Viet Nam. YF12A, #934 pieces remained at Burbank for a time until the AF realized that having lost one of their "B" models, they needed another trainer. At Burbank there was a complete metal mockup fore-body of an SR-71. It was complete except that on assembly it was never meant to fly, so all the fuselage panels were assembled dry, no sealant. Thus was born #981, the vehicle that nobody liked because it was different. #934's fore-body hung around Burbank until Lockheed finally interested NASA Dryden into having it shipped up to Edwards AFB for testing purposes. They did ultimately use it for fit check and tryout of the quartz heaters in a test that was completed using #935. It was damn expensive buying and powering all the heaters required to completely wrap the airplane in this heater shroud. It had to be done late at night when the power requirements on the base were the least. I don't remember the electrical load but it was huge. The purpose of this test was to heat the vehicle to a hot-leg environment, so as to calibrate and confirm all their thermocouple data from their test flights. The aircraft had to be fueled for this. We used denatured alcohol instead of JP-7. The fore-body from #934 kicked around in the junk pile for a while and at the closing of NASA YF12A Program in was carted off, by Lockheed ADP people.......to that great place of mystery and was buried.

Note of interest: The GAR9/AIM47 was ultimately given to the NAVY F14. Its capability was reduced to allow for more reliability. By that I mean the range was reduced to, I think about 100 miles.

Written by Bob Eaton, Lockheed Skunk Works Advanced Development Program

Editors Note: Bob Eaton has worked throughout the Blackbird Program for 36 years (1963-1999). His resume included Lockheed Engineering Flight Test Supervisor-Electrical/Instrumentation; Lockheed Technical Representative (Skunk Works); Dryden NASA Flight Test Center Consulting Engineer for the A12, YF12Aand the SR-71. Thanks Bob for your lifetime contribution to the success of the Blackbird Program in all of it's many aspects.

COURTESY OF  Leland R. Haynes    "SR-71 Blackbirds"

 

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YF-12A 935

This YF12A is the sole surviving aircraft of the Interceptor series. On 18 March 1965 flying at mach 2.2 and altitude of 65,000 feet, #935 launched an AIM-47 missile successfully intercepting and destroying a Q-2C Drone flying at 40,000 feet. Again on 19 may 1965 flying at Mach 2.3 and altitude of 65,000 feet, #935 launched an AIM-47 missile successfully intercepting and destroying a Q-2C Drone flying at 20,000 feet. She was in storage from 1967 to December of 1969. On December 11, 1969, #935 was loaned to NASA as a test aircraft flying 145 flights for NASA. On November 07, 1979, #935 was flown to the U.S. Air Force Museum at Wright-Patterson AFB, Ohio for permanent display. Flight crew to Wright Pat was Col. Jim Sullivan and Col. R. Uppstrom.

 

YF-12 radar systems engineer Ray Scalise recalls one adventure in 935, during the US Air Force's test program:

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Preparing for Launch

"One of the things that was done to the YF12As at Edwards was to paint a white cross on the bottom of the aircraft to make it visible against the black sky so it could be spotted by a ground observer who was stationed on the hangar roof during missions (they used high power binoculars). He was in radio contact with the engineers in the radio room in the hangar.

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YF-12A #935 on the ramp at NASA FRC, April 28, 1971

"On one mission the observer said he did not need the binoculars to see the airplane because he could see the "contrail." Airplanes con at 35,000 ft, NOT AT 80,000 ft. At about the same time my pilot noted we were losing fuel at a very high rate. He guessed a fuel line to the left engine had burst and was feeding raw fuel into the engine. He immediately declared an emergency, throttled back on the engines and began a spiral descent to Edwards since we were right overhead. I kept my hands on the eject handle in case the airplane decided to explode. We landed OK and when the plane stopped the base commander was there with his car. Emergency vehicles had not arrived on the scene yet, so the base commander drove up to the plane on the right side by the cockpits.

"Both the pilot and I egressed the aircraft by jumping on the roof, then the hood of the car and started to run away from the bird. It looked like it had just come out of a car wash and was leaking fuel all over the runway. I still do not know why it did not explode. YEAH, the fuel was of low volatility, but come on!

"Anyway, because I was carrying almost double my weight (the pressure suit weighs 35 lbs and the parachute weighs 70 lbs; I only weighed 120 lbs), I was concerned about falling off the airplane and breaking my neck. SO...I walked down the chine on my spurs to keep from slipping on the wet skin (the spurs were strapped to your boots, and were used to hook into cables on the seat which were designed to pull your feet back into the seat to prevent leg loss during an ejection). In doing so I punched a couple of holes in the upper chine skin. Thus, I have always contended I "signed my signature" to the plane.

"If you are ever in Dayton, Ohio at the air museum, there you can see the patches on the upper chine, right side by the rear cockpit where they repaired my 'signature.'"

 

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NASA crewmen Fitz Fulton and Don Mallick with 6935

 

YF12A  #60-6936  LAC #1003

 

On Saturday, May 1, 1965, YF-12A #60-6936 was used to set several speed and altitude records (notice the white reference cross just visible on the underside of the engine near the landing gear).  This was "coincidentally" the Russian New Year, and 5 years to the day that Gary Powers was shot down flying his U-2 over the Soviet Union.  The plan was to have 2 airframes (936 and 934) each set different records, but 934 developed problems at the last minute, and so 936 was used to set all of the following records that day:

World Speed Records set by #936: 60-6936 courtesy of NASA

May 1, 1965......WORLD ABSOLUTE RECORDS FOR SPEED: 1,000 km Closed Circuit . . . . . 1,688.891 mph (2,718 kph) Crew: Maj. Walter F. Daniel, Capt. James P. Cooney

May 1, 1965......WORLD ABSOLUTE RECORDS FOR SPEED: 500 km closed circuit . . . . . . 1,643.042 mph (2,644 kph) Crew: Maj. Walter F. Daniel, Maj. Noel T. Warner

 

On 22 March 1966 #936 flying at Mach 3.15 and altitude of 74,500 feet launched an AIM-47 missile successfully intercepting and destroying a Q-2C Drone flying at 1,500 feet. On 13 May 1966 flying at Mach 3.17 and an altitude of 74,000 feet #936 successfully intercepted and destroyed a Q-2C Drone flying at 20,000 feet. The third and final missile intercept occurred on 21 September, 1966 with #936 flying at Mach 3.2 and an altitude of 74,000 feet successfully intercepted and destroyed a QB-47 in low terrain. YF-12A #936 set the world Speed and Altitude records on 1 May 1965. The USAF team of pilots was led by Colonel Robert L. "Silver Fox" Stephens, the first military pilot to fly the YF-12A.

World Speed and Altitude Records Set by #936
WORLD ABSOLUTE Altitude RECORD: Group III Sustained Altitude (Absolute). . . . . 80,258 ft. (24,462.59 m) Crew: Col. Robert L. Stephens, Lt. Col. Daniel Andre
WORLD ABSOLUTE AND CLASS RECORDS FOR SPEED: 15/25 km straight course . . . . 2,070.102 mph (3,352 kph) Crew: Col. Robert L. Stephens, Lt. Col. Daniel Andre YF-12A #936 was briefly retired but reactivated for NASA test programs. This aircraft was lost on 24 June 1971 on the 63rd flight test in an accident at Edwards AFB. Pilot Lt Col Ronald J. Layton and Systems Operator, Billy A. Curtis were approaching the traffic pattern when a fire broke out due to a fuel line fracture caused by metal fatigue. The flames quickly enveloped the entire aircraft and on the base leg both crewmembers ejected. #936 was totally destroyed. Both crewmembers survived.

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YF-12A  6936

60-6936 She was still wearing that cross when she was lost on Thursday, June 24, 1971.  On approach to Edwards Air Force Base, a fire broke out from a ruptured fuel line and quickly engulfed the entire left engine.  Pilot Lt.Col. Jack Layton and Systems Operator Billy Curtis ejected safely, but the aircraft was a total loss.  Shortly thereafter, SR-71 #951 was reassigned the bogus tail number 06937, re-designated as a "YF-12C", and continued with NASA's YF-12 program until its conclusion in 1979.
 

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	Clarence L. "Kelly" Johnson, about to get the first "check ride" in 927 with Lockheed test pilot Lou Schalk.  Contrary to some reports, this was not the only time he flew in a blackbird; in his book Kelly: "More than My Share of It All", Johnson states that he was also in the back seat of a YF-12 on one of the missile test firings.

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Col. Robert L. "Fox" Stephens, (pilot) and Lt. Col. Daniel Andre (fire control officer)	MAIN LANDING GEAR

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AIM-47 Missile in the Launch Bay	The first YF-12A AIM-47 Missile target	The last YF-12A AIM-47 Missile target