FuelConsumption

I have been an avid metric user in the USA since I was first able to measure items. Thanks to the 1970's push I was included in a group of Americans who were educated under the easiest system for measurement in the world. I was a kid at that time and I lived near Edwards Air Force base.

My father always had a joke about the SR71's speed being a secret. He would joke with me and say it was faster than my bike, or faster than the car, etc. I remember overhearing at my parents cocktail party a conversation between two of my parents friends about how much fuel an SR71 used per hour at its cruise speed (usually very constant). These terms were expressed in SI units. These people were engineers. They were talking about how the fuel thickens over time while flying and that there are problems in cooling the engine if its fuel gets too thick, etc.

My neighbour who piloted this aircraft was talking to my dad. I sat there for a moment while my dad was talking with him and I asked how many hours can he run before a refueling. He told me quickly to get back into conversation. I sat there for a while and later said that aircraft flies about xxx far. He kind of sat there and nodded. I remembered my father earlier told me about one of these planes that leaked most of its fuel onto the runway a few years earlier and that they had to hold off landing of other aircraft because there were X number of gallons of JP-something fuel all over the place.

I went into my dad's home office and grabbed a dead reckoning wheel that had many conversion factors on it (this is a slide rule calculator for pilots) and looked at a milk bottle to see how many litres were in a gallon. I figured out what I thought was its fuel capacity. About an hour later I said to our pilot neighbour "Wow you can fly XXX km/h! That's pretty fast." Both my father and my neighbour looked at me with confusion. I asked how many km/h is a Mach? Neither knew. They did know how many knots were in a Mach at a certain altitude but at that time, my dad said to keep quiet about my km/h speed and not tell anyone - with a wink. My neighbour put down a his beer and laughed. He asked how the heck I guessed that number. I told him that I was learning about the metric system in school and how easy it is to figure out things in metric. He agreed with me and laughed some more. He roughly figured out the conversion to knots and said the speed was close to his cruising speed, but not close enough.

He looked at my dad and back to me and said, "I will tell you how fast I fly...When I am flying at the speed and altitude that I like to fly, let's just say that I have to be careful not to pull back too much on the stick. If I do, the plane shoots upward very quickly, and you cannot turn or do anything for a while because there is not enough air for the rudders, and ailerons at that height. I work for the Air Force and not NASA. NASA takes over at a certain altitude. Flying like that is dangerous because the aircraft does not peroxide reaction control jets and you cannot do anything until you curve downward again. You also can flame out that high too. When you finally do gain control, you might overshoot your way point placing you deep in someone else's airspace at an altitude that is accessible by surface to air missiles. Ahh but at your XXX km/h I guess that is not a problem because you can outrun that missile. Right? To turn around my plane, it has to travel the in the area of four states. I can fly fast, but I also use up fuel very fast. KC-135s do not fly over that airspace either. You just do not want to take the chance of being shot down or running out of fuel. If you do, you may end up being the next Gary powers. I can guarantee that once you parachute down in that country, you will be able to make use of your km/h quite a bit!" He laughed again and said that you would be able to count years in Siberia with the metric Deca prefix.