Above FL600

Roddy and I were having a discussion the other day about a recently aired TV program regarding the Lockheed SR71, our super secret, super fast spy plane. I wound up recalling two interesting events that made me realize I might have been the biggest danger in the government's ultra high altitude recon program.

The SR71 wasn't the first extremely high flying aircraft. It wasn't even the second. The two ahead of it were the famous U2 (as in Gary Powers, shot down over the Soviet Union), and a modification of the B57 Canberra. There probably isn't any need to elaborate on the U2, but the B57 isn't particularly well known. A variation of it was built with extended wings (U2-like in concept) and flown at very high altitudes much like the U2 and the SR71. In fact, there was even a special provision in our Procedures Manual (FAAH 7110.whatever) regarding “pressure suit flights” that covered the operation of these aircraft.

For example, non-aviation types may think that any altitdue above the ground is like any other, but in truth, the higher you go, the harder it is to get and stay there. The normal operating regime of piston powered aircraft is probably up to around the mid 20s, although there were a lot of WWII aircraft that could get into the 30s, even if not perform well there. As I recall, the near absolute ceiling of a piston powered airplane was established by a P38 at around FL420 (42,000').

Most jets are very comfortable up to around FL400, and I don't think I saw anything above FL410 in the first dozen years of my career with the following exceptions: SR71, U2, B57. Nowadays, there are B757s that operate routinely at FL430 and at least one Lear is certificated to FL550 (55,000'). I've been away over twelve years so something marginally higher may have come along, but if it carries passengers it's not going to be much. In fact, flight above the 50s is so exceedingly rare, it wasn't even classified as part of the PCA (positive controlled airspace) which was established after the Grand Canyon crash in the late '50s. Flight above FL600 could be handled “VFR On Top”—exactly the same conditions under which the two Grand Canyon airliners were operating—we still provide separation, but the altitude is picked by the pilot.

Because of the nature of their operations, much of the specifics about pressure suit flights were classified—entire flight plans in the case of the SR71s—and specific altitudes in all of their cases. Once they were above FL600, that was the only plain language altitude report you could get. When they would check on the frequency, it was on the order of, “Chicago Center, Aspen 25, above FL600.” In truth it was an extremely rare circumstance in which you would ever need the specific altitude, but if you asked, you would get a coded phrase which could be decoded at the watch desk. So to bring to a point the purpose of all of this background, here are two events that I think will probably mark me as the most dangerous man to the extreme aircraft program in the world east of BAB (home of the SR71).

First exhibit: I was working JAX High one day and had a B57 southbound transitioning to land at MCO, descending to FL240. We were chatting amiably about aviation matters as I had no one else on the frequency when I took a handoff from ZMA on a U2 which had just departed MCO. U2s climb like scalded cats and he was quickly on my frequency still south of the boundary. He and I started chatting, too, and I realized all of a sudden that the B57 wasn't getting down fast enough to clear the U2 and I wound up having to vector the only two airplanes I had pretty dramatically to ensure separation.

Exhibit two: fast forward, years later, I'm working High Altitude in ZAU. It must have been a transition period when we had a “super high” open which covered the whole west side (BDF, IOW, DBQ sectors) from FL350 on up. My sector was nearly 250 miles long and more than 100 miles wide—a lot of airspace, although the bulk of the traffic was below me in three separate sectors.

I was working a U2 (above FL600) and took a handoff from ZMP on an SR71. One really must ramp up one's thinking when working aircraft at Mach 3 (although the U2 lopes along at a much more pedestrian Mach .70 or thereabouts—it's slow by any jet measure), and it became clear that these two were going to get geographically pretty close to each other. The best alternative would be to establish some sort of altitude separation—it's difficult to vector at Mach 3. Moreover, by the 1970s “On Top” was murky territory for controllers of my age (and particularly for High Altitude specialists) and the fact that it was up in the Flight Levels, which we were accustomed to thinking of as Positive Controlled Airspace, made me decide to grab some altitude.

As I mentioned, asking directly would not have yielded usable information, and taking the time to forward two coded altitude strings to the watch desk, and getting useful information back did not seem a sound prospect. So, I asked both of them their altitudes, got the coded phrases, and then asked each of them if they were sufficiently separated. Each replied they were, and I sat back and relaxed.

Okay, I may have overstated the danger part, but not many controllers can lay claim to having to take action to separate traffic above FL600. And although the two in ZJX were in the lower Flight Levels, they were still both pressure suit flights, so the mystique applies, I think.

Last updated: 19 December 2009