Northrop’s XST entry was similar in appearance to that of Lockheed’s; its design had been developed from a computer programme called GENSCAT. This also had its origins in mathematical equations associated with the physics of optics. McDonnell Douglas had been the first to determine what the RCS thresholds for the competition were likely to be, however they were unable to design an aircraft that could achieve anything like those
goals. With RCS results from both Lockheed and Northrop verging on the revolutionary, DARPA determined that the program should be developed into a two-phase, full-scale, flight test demonstration. Phase 1 would culminate in a ground RCS evaluation of large scale models, following which one contractor would be selected to proceed with phase two: the construction and flight testing of two demonstration vehicles. The estimated cost for the XST programme was 536,000,000 and this would be split between the successful contractor, the Air Force and DARPA. On 1 November 1975, Lockheed and Northrop were each awarded contracts of SI.5 million to conduct phase one of the XST programme.
In early April 1976, Lockheed received word that they had officially’ won that phase of the competition. However the outstanding results also achieved by the Northrop team caused DARPA to urge them to remain together. Shortly thereafter Northrop successfully submitted studies for a Battlefield Surveillance Aircraft, Experimental (BSAX) which became Tacit Blue – the highly successful flight demonstration programme that provided vital data for the subsequent B-2 bomber program.
Phase two of the XST programme was code-named Have Blue, and was initiated on 26 April 1976, when the Skunk Works were authorised to proceed with the design, construction and flight testing of two technology demonstrator aircraft.
Have Blue had three objectives:
1. Validate, in flight, the four low observability- signatures identified earlier in the programme, (radar, infrared, acoustic and visual).
2. Demonstrate acceptable performance and flying qualities.
3. Demonstrate modelling capabilities that accurately predict low observable characteristics of an aircraft in flight.
.Manufacturing was placed under the direction of Bob Murphy and the entire Engineering, Fabrication and Assembly of Have Blue was carried out in legendary Building 82 (birthplace of the F-104, U-2 and A-12).
Above left Lockheed chief test pilot, Bill Park (in flight suit), was first to fly the Have Blue prototype HB1001. (Lockheed Martin)
Above Maj Norman ‘Ken’ Dyson was recruited into the Have Blue program whilst serving as Director of the F-IS Joint Test Force. (Lockheed Martin) below НВІ00І received this ingenious three colour-three tone camouflage pattern to hide the facetting from uncleared ‘onlookers’. (Lockheed Martin)
Just three assembly tools were used on the project; wing, forward fuselage and aft fuselage. The sub assemblies were all made on a tooling plate left over from where the main frames for the C-5 Galaxy had been machined. On the morning of Wednesday 16 November the prototype Have Blue (HB1001) was flown by C-5 from Burbank to Area 51, where it was reassembled and readied for a final series of pre-flight tests. On 1 December 1977, Bill Park completed HBlOOl’s maiden flight.
The first five sorties in aircraft number one were completed by Bill, who was chased on each occasion by Air Force Test Pilot Ken Dyson in a T-38. On 17 January 1978, Ken completed his first flight in the Have Blue prototype. All was proceeding well and on 4 May 1978, Bill had conducted 24 flights on HB1001 and Ken, twelve. However, whilst returning to Area 51 that day,
Bill was involved in a landing incident which damaged one of the aircraft’s main undercarriage legs. Retracting the gear and going-around for another landing attempt Bill discovered that the damaged leg would only half extend. Despite several attempts to free the jam by pounding the other main wheel on the runway, it steadfastly refused to budge. As fuel depleted, the decision was made to climb the aircraft to 10,000ft and for Bill to eject. However, on the climb, the aircraft ran out of gas and Bill was forced to eject, during the course of which he hit his head and was knocked out. Still unconscious when he hit the ground, he sustained back and leg injuries that forced an early retirement from test flying.
It would take a further six months to prepare HB1002 for its maiden flight; an event which took place early on the morning of the 20 July 1978. Ken Dyson recalls, “We
flew three flights to check the aeroplane out, then on 9 August 1978, we began to take the first airborne RCS measurements. І Пси against a ground based facility and on these first series of tests, they wanted to check-out the cross-section of the aeroplane nose-on, that’s with a look angle of zero. To achieve this, I climbed to a predetermined altitude and maintained a heading that would take me right over the radar test site. When I reached the test point, I configured the aeroplane in a decent, making sure my speed, angle of attack and rate of decent was exactly correct. I had to keep control movements to a minimum in order to provide accurate test data, so 1 switched in the autopilot. Well, as soon as I did that, the nose went right and the wing rolled slightly left. I later learned that Ben Rich, who was watching the test in the radar control room went crazy, asking, ‘What does that goddamn Air Force pilot think he is doing! Is he deliberately side-slipping the aeroplane to screw-up our test results?’ I decided to switch-off the autopilot and fly manually, something we’d planned not to do, because the test engineers didn’t think the necessary tight parameters could he achieved manually. Well it seemed to work pretty good, and after that, 1 flew all the tests manually – we never did resolve the problem with the autopilot. Virtually every flight in aeroplane two was associated with RCS measurements and if we weren’t measuring radar returns, we would be flying the aeroplane against operational systems to see if they could see us. To my knowledge, none did.”
On 29 June 1979, Dyson air aborted HB1002 shortly after take off, following a fluctuating hydraulic pressure reading. He continues, “On 10 July, we flew again and the aeroplane was OK. The next day I got airborne and had the chase aeroplane look me over, everything was OK, so I flew outbound to get to a point to run against an F-15 Eagle, to see how it performed against us. I was
Above HBI002 was the RCS test vehicle and was flown throughout its life by Ken Dyson. Its external appearance differed from the prototype: gone is the instrumented nose – boom and the drag ‘chute receptacle. (Lockheed Martin)
Below HBI002 accumulated 52 test sorties before being lost on 20 July 1978. (Lockheed Martin)
just short of the designated turn point, when 1 noticed the same hydraulic system begin to oscillate, again in the downward direction. 1 thought well, that’s the end of this flight and turned back. I started to tell test control about my problem, when I got a fire light. After pulling the pow’er back, and telling them of my troubles, I shut the engine down. All this was in short order. I had the aeroplane pointed towards home plate and configured at the right speed for single engine operation (it was not a
Above Despite initial skepticism over the ‘Hopeless Diamond’ concept, Dick Cantrell and his team of aerodynamicists worked tirelessly to ensure that the F-l 17 retained the smallest RCS and remained aerodynamically viable. (Lockheed Martin)
Below As president of the Lockheed Martin Skunk Works, Ben Rich was the driver behind the stealth concept; he passed away on 5 January 1995. (Lockheed Martin)
good performer on a single engine, not much thrust, and a lot of drag). I was coming home somewhere between 20 and 25,000 ft. Shortly after that, the remaining hydraulic system began to oscillate in a downward direction and I knew that was not good for our unstable machine. Just about the time the remaining hydraulic system went to zero, the plane pitched violently down, something like 7 negative ‘g’s, it then pitched up, the pitch rates were just eye watering, something only an unstable machine could do. I was somewhere around 225 knots and above 20,000ft and the aeroplane was tossing me up and down and actually got near vertical nose down and near vertical nose up. I began to try and reach for the ejection seat ring that was between my legs. I got my hand on it and pulled. The canopy blew off, the seat went out and I found myself floating under a ’chute at about 20,000 ft.” As Ken slowly descended by ’chute, the pilot of the F – 15 with whom he had planned to conduct further tests began orbiting above. Col Norm Suits, the Director of the F-l 5 Joint Test Force, saw the stricken Have Blue aircraft impact the ground and shortly afterwards, spotted two unauthorised cross country vehicles heading towards the crash site. Although the vehicle’s occupants were probably intent on performing their public duty and offering help and assistance to any survivors, the highly classified nature of the program and the materials used in its design couldn’t be compromised. Acting on his own
AVIATION PIONEERS: LOCKHEED’S BLACKWORLD SKUNK WORKS
Left Unstable in all three axes – pitch, roll and yaw – it is essential that this fly-by-wire platform receives accurate air data at all times. Therefore this unique four probe system was developed. (Paul Crickmore)
Below Although ice encrustation was not an issue on the Have Blue research vehicles, much time, thought and effort was devoted to the problem on the F-117, before this simple wiper blade was developed. (Paul Crickmore)
Left The F-l 17 is at its most stealthy head-on, 25 degrees look – down and 25 degrees look-up. Note suck-in doors located above the intakes to supplement air flow at low engine operating speeds. (Lockheed Martin)
initiative, Norm began a series of extremely low passes at the vehicles to deter their drivers from closing in on the wreckage. Just how low these passes were, can only be judged from the fact that he succeeded in his objective!
Ken continues, “I had noted my take off time, and while hanging in my ’chute I noted that ten minutes had elapsed from take-off. I watched the unstable machine flip flop slowly it seemed, as it descended vertically below me and I saw it hit the ground and erupt into a ball of fire, it still had a lot of gas on board. It took me quite a while to make my parachute descent down to the desert floor, after landing (that was my first and only jump to date), I again noted the time, I had been in the parachute for ten minutes”.
The cause of the crash was determined to be an engine exhaust clamp, which had become loose, allowing hot exhaust gases to enter the right engine compartment.
This had triggered the fire warning light, and as the temperature built up, first the left and then the right hydraulic lines failed, which in turn caused a complete loss of control.
Fortunately the program was within two or three sorties of its planned completion, which officially ended in December 1979. Having achieved all its test objectives, the Have Blue programme can be categorised as a stunning success.