More Than A Feeling

We feel some weird stuff  when we fly. Part of the reason for this is that flying is kind of a weird activity in the first place.

People are very sensitive to acceleration. Our inner ear is a precision instrument for balance perception and our brain is a really fast processor. This makes it easy for us to stand and walk.

Our brains are also very good at finding patterns. Patterns in numbers, pictures, sounds, and sensory input.  Also, our brains will often create a pattern where one doesn’t exist and one of our senses can cause errors of perception in the others. This is a large part of why flying without visual reference to the horizon is a skill acquired only through considerable training. Up doesn’t always feel like up.

The takeoff begins with acceleration. When the brakes are released and the power is pushed up the speed increases and we feel “pushed back” in the seat.  This is because we are being pushed back in the seat.

Engineers call the maneuver when the nose of the airplane is raised up on takeoff “rotation”.  An airliner at average takeoff weight generally rotates at around 3 degrees per second once the proper takeoff speed is reached. This provides for a pitch attitude of about 8 degrees “nose up” as the wheels leave the ground.  Airliners have a limit of allowable pitch during takeoff to prevent the tail from dragging the ground.  A “tail strike” is a bad thing so we don’t exceed this limit.

As the landing gear is retracted our speed is about 30 percent more than the minimum stall speed for the wings and the pitch is at around 10 degrees and increasing to an initial climb value of 18 to 20 degrees. This makes us feel pushed down in the seat a little as the pitch is increased.  If you were sitting on a scale your measured weight would increase about 10 percent. ( a total guess)

It has only been 40 seconds or so since brake release and this is already enough to confound our human balance sensory processing. When you can’t see outside, the inner ear will often interpret acceleration as a turning movement. The combination of this and the conflicting visual input of  the stationary airplane interior which is clearly not turning makes people feel weird.

After getting off the ground our next objective is to get up to a safe altitude in the event of engine failure so the 18 or 20 degrees of pitch persists for another half  a minute or so. A turn might be started during this time, introducing yet another confusing sensory input.

When about one thousand feet high it is time to start accelerating to flap retraction speed and “cleaning up” the airplane.  This doesn’t involve throwing away candy wrappers but is a general description of  retracting the flaps and anything else than hangs out.

The pitch attitude is lowered to about 13 degrees, this might make you feel “lighter” in the seat.  The 5 degree change doesn’t sound like much but it is easily perceptible, especially if it isn’t done smoothly. By the time we reach about three thousand feet our speed is at 250 knots and our “acceleration state” should be pretty much neutral.

There are almost always level offs , speed changes, and turns on the way up to cruise altitude. These aren’t as dramatic as the takeoff but if you are sensitive you might notice a difference in acceleration.

When there are visual cues outside most people feel less uncomfortable. Misleading visual cues like slanted clouds or rows of lights can cause you to feel like the airplane is leaning  to one side or turning when it isn’t.

If you are bothered by motion sickness consider getting a window seat.  Watch outside during the takeoff and climb. Try to look at the horizon as far away as possible.  This might help you stay better oriented. 

 Happy landings

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