Flight Test Exuma

T-39by L. D. Alford
Photo Courtesy of the Wikipedia

Exuma is an island in the Bahamas Island chain. It lies about 300 miles from Miami and about 150 miles south of Nassau. The only way in or out is by boat or by air, and in 1992 there was no regular service of either. In 1992, the runway on Exuma Island was 5,000 feet of shell and coral embedded asphalt: the slickest material you can make a runway out of. Because of the lack of facilities and the short runway, no jet aircraft had been into Exuma Island until we flew there to flight calibrate the Aerostat Balloon. We had a waiver from Air Force Materiel Command (AFMC) headquarters for the runway length.

An Aerostat Balloon is a helium balloon tethered at a significant altitude above the surface of the earth. It incorporates high precision lookdown radar that is used to detect low flying aircraft and undocumented boats entering the United States and our allies airspace. The Aerostat Balloons blanket the southern boarder of the United States and identify drug and immigrant runners.

The T-39’s owned by AFMC were chosen to act as targets for the Aerostat Balloons. They were chosen, first, because they were the most documented target aircraft in the modern inventory. I marketed this particular fact throughout the United States test community. In the T-39 office, we had been gathering historical documentation on the T-39 as a radar target for years, and the aircraft acted as a target for numerous early radar programs. A specific aspect of the T-39 that made it a great target was its forward 2D area which was almost exactly 1.5 square meters. If you can’t guess why 1.5 meters is about the right size, I won’t tell you. The second reason the T-39 was chosen was its low cost to operate. When the aircraft was stationed at Wright-Patterson AFB in the last days of the 4950th Flight Test Wing, it cost less than $500 per hour to operate. This was the lowest flight cost for any jet in the Air Force inventory, and a great price compared to $5000 per hour cost of most other small jets. The third reason was the Wright-Patterson flight test reputation. The department running the Aerostat testing knew the job would be accomplished at the lowest cost possible with the highest quality data output. They also knew they were getting at least one Air Force Test Pilot School trained test pilot managing the program. In this case, they got two test pilots, and that’s where I came in.

I was the Chief of Test for the Air Force T-39 flight test aircraft which by 1992 was almost all the Air Force T-39 aircraft. The T-39 was the first business jet and was developed by Rockwell as an Operational Support Airlift aircraft, to carry high value personnel and cargo. This is the same mission the Air Force C-21 Lear Jets and Presidential Support aircraft do today. Some T-39s were modified with a hydraulic powered 10 Kva AC generator in the tail cone compartment and designated B models. Wright-Patterson owned all the remaining B models in the AF and maybe the world. Many of the Wright-Patterson T-39s were NT and CT versions. They were significantly modified internally and externally for special flight test programs. Most of these went to the aircraft bone yard at Davis-Monthan when the Air Force closed the 4950th Test Wing. The T-39 was the last of the German jet designs taken after WWII and incorporated almost in totality into a US military aircraft. The T-39 had approximately the same wing as the F-86 and incorporated many design elements of the Me-262. The T-39 was officially called the Sabreliner because of its similarity with the F-86. The aircraft flew like a fighter. It originally was a fully aerobatic 7G aircraft, but by the time modification flight test got them, they were so restricted that they basically flew straight and level flight test. Fortunately, they could still fly safety and calibration formation chase. The T-39 was and is by far the best heavy aircraft chase ever made. It could also vie for the best target aircraft.

Because I had a lot of experience flying internationally, my Squadron Commander Lt Col (at the time, later Major General) Jeff Riemer gave me the job of planning and managing the planned flight test at Exuma. I didn’t learn until later that he planned to go along as the copilot. As things worked out, we were the only volunteers for a two week flight test in the Bahamas—go figure. I think the primary reason Jeff wanted to go was his inexperience in heavy aircraft international flying. He had been a fighter pilot prior to test pilot school and accepted the job of commander at a heavy flight test squadron. Now fighter guys do get experience in international flying, but not nearly as much as some heavy pilots. I had been flying in Europe, Central, and South America since the beginning of my career. I think Jeff wanted to see what the overall planning and experience was for a single aircraft outside the confines of basic Air Force aviation. Jeff Riemer was like that. He gained a reputation as a fighter pilot who wanted to integrate fully into and understand the heavy aircraft community. We shared a kinship since I started out in the fighter community and came accidentally to the heavy world. After I got there, I wouldn’t have left it for the world. I like the crew mentality of heavy aircraft flying. Not that the T-39 is a very heavy aircraft, but it does have a crew of two.

I had everything planned for our trip. We departed for Patrick AFB and then Exuma. We were flying with a new box on this aircraft. We had an early aviation GPS. The mod center at Wright-Patterson installed them as a temporary modification in our aircraft. In fact, this particular installation got a certain Major medals, awards, and almost court marshaled. To help support the original Iraq war, Wright-Patterson developed the temporary modification GPS to be installed on any aircraft we could proof test. The unnamed Major developed a quick installation antenna that did not have the problems of common internal antennas. Although GPS was not yet fully operational, the installation gave Wight-Patterson’s test aircraft and operational aircraft a fantastic improvement over their current navigation capability. During the first Iraqi war, Wight-Patterson test aircraft, mostly C-141s, C-18s, and KC-135s, used this GPS capability to aid in high value airlift and fighter deployment support. The problem was the facilities in the modification hangars and facilities couldn’t keep up with the production of the special antenna fixture. The unnamed Major began making the antenna fixtures at home in his garage. Then someone in the mod center turned the Major in. This was after the Major got all his awards and medals. The Wing commander couldn’t close his eyes to the accusation and commenced an official investigation. The Major survived, but not unwounded. The Air Force never received enough GPS antenna fixtures and the world is a worse place because politics got in the way of true patriotism. By the way, this is one of the reasons the mod center was shut down at Wright-Patterson. There are many other reasons, but that discussion will have to wait until a more opportune time.

We were flying with one of these great GPS units. They really were great. They couldn’t be trusted, and they were cumbersome to use, but they told you exactly where you were within 100 meters, give or take. For the Aerostat testing, they were more than sufficient. The test plan design was for the radar to note our position at various altitudes and distances and calibrate that with the GPS data from the aircraft. The flying was supposed to be very simple: takeoff, go as far out as safely possible, turn around, fly back on the exact flight path as on the way out, and land. One to two flights per day, with a day between flights for data reduction—pretty cushy test schedule.

It became even cushier when Jeff negotiated our grub with the hotel. From the European guests, he heard something about a single price for a week that included breakfast and dinner. He reached an agreement with the owner that gave us a great rate—we ate fantastic four course dinners of lobster, chicken, fish, or beef, every day we were there. When we weren’t flying, it was a typical tropical TDY (Temporary Duty): we snorkeled, we sat on the beach, ate great food, and talked about flying.

The flying was spectacular. We didn’t have any bad weather not even the common tropical afternoon thunderstorms. We also didn’t have a lot of backups. The nearest divert field with a long enough runway was over 100 miles away. If the weather crumped, or the runway at Exuma went down, we would be schosh on gas. We kept a good heads up on the weather information that was available.

The first flight test, we noticed a lot of people lined up on the beach when we took off, and they were waiting for us when we retuned. When we came back, the guy who ran the airport asked us to tell him when we were taking off, and when we were landing. At first we were a little concerned about this—questions about military operations in a foreign country are always suspect. Then he said, “You are the first jet that has ever flown into Exuma, and everyone wants to see you takeoff and land.”

Somehow we had become an item of interest. People literally lined the beaches near the airport when we flew. I guess they thought they were getting an air show.

The target flights at Exuma were largely unexciting. The T-39 didn’t have an autopilot so we had to hand fly everything. A T-39 can get squirrelly at high altitude, but it’s pretty docile down low. Jeff and I had a running bet on altitude and accuracy because the GPS recorded this data on each run, so it was easy to check. Since some of the runs were at 200 feet AGL (above ground level) this was a great challenge. The runs were nail biters from the standpoint of fuel planning and navigation, but otherwise they weren’t anything to write home about—except one. Jeff was flying on the way out, and we were marking points on the GPS for return. The mission was to fly at 200 feet over as much land as possible. This meant skimming the islands south of Exuma from one end to the other. The trick was that we had to hit the exact points on the way back. We turned the corner at the end of the run and had just started back the other way. Fuel was tight, but the weather was beautiful—then the GPS died. Remember, this was a long time before the GPS system was approved for flight. Our GPS box didn’t die; the Air Forces shut down the GPS satellite transmissions. We had nothing, but gas and a map—just like Lindbergh. We didn’t want to lose the test flight so we continued, picking the route and points from memory. I didn’t want to lose the bet since I was flying. We hit each point almost exactly. We were so good, the Aerostat guys couldn’t tell, from our track, when we lost course guidance. Just as Exuma Island was topping the horizon, the GPS system came back on. Pretty good mapping for a couple of pilots who hadn’t looked much at the ground for navigation in years. Our beach crowd was waiting for us and got a good look at 200 feet as we pitched up into the pattern and flew an overhead.

The only other rough spot was our computers. We brought a couple of brand name laptop computers to download the GPS data for our Aerostat customers. We had two in case one broke—and both broke. At one point, I had two computers apart in my hotel room and eventually put together one that worked. I could download the GPS data, but I couldn’t put it on a floppy disk for the Aerostat guys. We eventually worked some computer hoodoo and downloaded the data directly to their systems. Afterwards, we also sent the data to them via the post office—these were the largely pre-Internet days.

All great missions must come to an end, and so did our flight testing in Exuma. We came back through Patrick AFB again. Of course, the Customs guys we prebriefed two weeks before when we came through Patrick the first time, claimed we had never spoken to them. We had to wait hours for clearance. One last thing, there were supposed to be nude beaches on Exuma—we never found them.

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