On my previous visit to Tucson, I saw the Rolls Royce owned Boeing 747 engine testbed. This was converted for the Boeing 787 Trent engine development program (hence the registration N787RR). The Number Two engine was removed and replaced with the test engine. The other three Rolls RB211s are unchanged. At various times the testbed has been reported to be without an engine in the test location but there was something there when I was last here – it’s just they didn’t fly. This time was different.
I saw the testbed when I left the airport after my flight landed. The following morning, I headed out to see what F-16 traffic there was and saw online that a flight plan had been filed for the testbed. I only had a certain amount of time before I was due to be at Hawgsmoke but it was supposed to fly long before that. Of course, test flying is not usually something that happens to a tight schedule and the takeoff time came and went. We were beginning to think we might miss it when the sound of some large engines spooling up reached us. A while later, out she came.
Engine testbeds require some careful control. Since one engine is significantly different in thrust from the others, there is a balancing act required to keep the thrust differential within the ability of the control surfaces to overcome. That means the max thrust is not always going to be used. Consequently, they use a good portion of the runway for takeoff rotating just passed our location. That meant I didn’t get the front quarter rotation shot I had in mind.
No matter, I still got to see it fly. The return was about six hours later and I was busy elsewhere at that time. I figured that was it for this trip. I was wrong. The morning of my departure, I had a little time to spare so went back to see what was happening. Amazingly, the testbed was already being crewed as I drove up. We got a repeat of the previous day and some similar shots. I guess I was compensating for not seeing it fly last time!
A number of different airframes have been used for airborne early warning requirements. The Boeing E-3 Sentry is the most well-known but there have been a number of other types over the years. SAAB developed a radar system that has been mounted on Embraer 145 jets, SAAB 340s and SAAB 2000s. The development of this system was started in the 1980s and a testbed was produced prior to the system appearing on a production airframe. This testbed was a Fairchild Metro turboprop. It made an appearance at the Farnborough airshow where I got some shots of it. It was camouflaged in what was then the standard Swedish camouflage scheme. This was a cool look for their planes and I do miss it.
