Friday, December 8, 2023

One Degree of Change

“They always say time changes things, but you actually have to change them yourself.” - Andy Warhol

F-16 Fighting Falcon Ready to Rock! (Photo taken by James)

There are quite a lot of aspects of aviation and flying airplanes that, surprisingly, transfer over seamlessly to real life.  One of the best examples of this is if you're flying an airplane and your heading is off by 1 degree then after 60 miles you will be 1 mile off course.  1 mile off course may not seem like a lot but keep in mind that resulted from your heading only being 1 degree off initially, which is a very miniscule amount.  If you've never had the pleasure of trying to hold a heading to an exact degree while hand flying an airplane that's getting rocked around by changing winds and turbulence, I can tell you with great certainty... it is not easy (but it is really fun).  At the same time, going 60 miles may seem like a fairly large distance but you have to keep in mind, the speed that airplanes travel at vary wildly and airplanes can cover a lot of ground... fast!

A Cessna 152 cruising at 120 miles per hour (mph) will cover 60 miles in only 30 minutes, which is at the slow end for airplanes.  A Cirrus SR-22 cruising at 240 mph will cover 60 miles in 15 minutes.  A Dassault Falcon 50EX corporate jet cruising at 480 mph will cover 60 miles in 7.5 minutes.  A Boeing 737-700 airliner cruising at 520 mph will cover 60 miles in 6.6 minutes.  An F-16 Fighting Falcon going 960 mph will cover 60 miles in 3.75 minutes.  An SR-71 Blackbird going 2,300 mph will cover 60 miles in 1.56 minutes.

Back when I was actively flight instructing (teaching people how to fly airplanes), this was one of my many favorite thought experiments to do with students, usually after their first cross country flight (with me onboard) during which they would always, inevitably, at some point during the flight, stop comparing their heading indicator to the actual magnetic compass (commonly referred to as a wet compass).  The heading indicator gauge is not magnetic, it's a gyroscopic instrument and anything with a gyro in it means it has friction which means it needs to be reset often to keep it on the correct heading.  It needs to be compared to the actual magnetic compass every 15 minutes and adjusted accordingly.  If you forget to do this, after an hour your heading indicator will suddenly be off by about 15 degrees (some airplanes more, some airplanes less).  Which is significantly more than 1 degree off, it's 15 times as much in fact!  This results in you thinking that you're on course but your heading is actually 15 degrees off and each minute that goes by you'll be significantly further off course, in terms of mileage.