SR-71 refuel

"pdthedeuce" (pdthedeuce) 10/04/2013 at 22:54 • Filed to: habu

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as if these things weren't hard enough to fly already, let's put the fuel port 20-something feet behind the pilot...Thanks, Kelly Johnson !!!

Lets Just Drive > pdthedeuce 10/04/2013 at 23:03

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I actually had no idea.

That's bloody insane. My knowledge is too limited, so let me ask (if you know) if this procedure is 100% pilot controlled or is there some auto-guidance involved?

Icemanmaybeirunoutofthetalents > Lets Just Drive 10/04/2013 at 23:08

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The boom is operated by a person on the refuelling tanker plane. The plane being refuelled will be told to get into position and then maintain it while it gets filled up.

pdthedeuce > Lets Just Drive 10/04/2013 at 23:08

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I think it's all pilot but I defer to some of the more learned Oppo plane specialists.

pdthedeuce > Icemanmaybeirunoutofthetalents 10/04/2013 at 23:12

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sure , but it had to be hard to maintain position when you can't even see the boom. surely they had reference marks on the tanker or something, huh?

Icemanmaybeirunoutofthetalents > pdthedeuce 10/04/2013 at 23:20

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I'm sure its hard as hell and these guys still look cool doing it. I'd be chewing my nails off if I were there!

pdthedeuce > Icemanmaybeirunoutofthetalents 10/04/2013 at 23:21

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no doubt !

f86sabre > Lets Just Drive 10/05/2013 at 08:39

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Right now I am reading Sled Driver by Brian Shul. He was a pilot back in the day. He described refueling as the scariest part of any mission and the had to do it multiple times. As you mentioned visibility is tough. Tey have to look for markings forward on the wings and fuselage of the tanker to get lined up as opposed to the aside to see markings on the boom and aft fuselage. What really made it scary was the Blackbird was drag/thrust limited at the speeds they had to fly while hitting the tanker. It had a hard time keeping up with the tanker. Sounds counter intuitive right? If I remember right, they had to fly at around 350kts during fueling. The Blackbirds aerodynamics and engines were not efficient at that speed. As they fueled up and got heavier the plane would start to fall off the boom. What they had to do was just bump one engine into minimum afterburner to keep up. Now you are dealing with asymmetrical thrust, the plane will be crabbing (flying kind of sideways) while tanking, at night... Yikes.

By the way, Sled Driver is an amazing book with some great pictures. Highly recommend it.

f86sabre > pdthedeuce 10/05/2013 at 08:58

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From Sled Driver by Brian Shul:

I was accustomed to being on the boom for just a few minutes to top off in fighters. In contrast, SR-71 refuelings took fifteen minutes or more which could seem like an eternity. This time was needed because the airplane took on an incredible amount of fuel. During a normal refueling we usually received over 11,000 gallons. This changed our gross weight by 70,000 pounds and caused a corresponding change in the center of gravity of our aircraft.

At the slow 300 knot range in which we were flying to refuel, the feel of the jet became sluggish as the SR filled with fuel. At these gross weights and slower airspeeds, the SR-71 became thrust limited during the last few minutes of refueling. In military power, we would start to fall off the boom. A disconnect was highly undesirable since the jet was less responsive now and to reconnect was more difficult. It also meant wasting time on the refueling track and this could affect our overall mission timing. The solution was to light one afterburner with careful finesse. The fine art of pulling the throttle ever so slightly up and just into the minimum burner range was handed down from one generation of SR pilots to the next. The SR is the only airplane I know that required the use of afterburner to stay on the boom.

Using one afterburner caused another problem: asymmetrical thrust. Some pilots used a little rudder to handle the yaw. Others left the rudders alone, flew sideways, and looked out the front quarter panel to see forward. The quarter panels were located on either side of the windshield. Only the left quarter panel was wired for defogging so we always lit the left burner to yaw right so we could use this feature if needed.

The most exciting moments on the refueling track were normally reserved for those final few minutes in afterburner on the boom with a very heavy jet. Once I selected min AB and the TEB dumped in, there was a pause, then the airplane lunged sideways and started to charge up the boom. With the left burner stabilized in min AB, I controlled our fore and aft position with right throttle. With this method, the pilot controlled the airplane by leading the power inputs. It was like flying a freight train because the airplane's inertia caused a lag between throttle input and aircraft response. It wasn't uncommon at this point for the director lights to resemble a pinball game, flashing from end to end as the fore and aft movements of the jet caused continual changes in relative position. I had to ignore the director lights, grit my teeth, and call on every bit of my experience to get to the end of the refueling track with a full tank.

pdthedeuce > f86sabre 10/05/2013 at 10:31

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thanks for filing in the blanks in my knowledge...I knew one (or more) of you guys would come through !!!

f86sabre > pdthedeuce 10/05/2013 at 10:52

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Yeah, I had read that section a week or so ago. Asymmetric thrust on a blackbird, while fueling (!), just sounds insane.

pdthedeuce > f86sabre 10/05/2013 at 11:51

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...like it wasn't scary enough already !

Lets Just Drive > f86sabre 10/05/2013 at 15:14

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Thanks! I'll check it out.

And I just have to say, that sounds downright terrifying!