Can a Boeing 747 Stay in the Middle of the Taxiway

1
Can a Boeing 747 Stay in theMiddle of the
Taxiway?

• T. R. Willemain
• ENGR 2600 MAU
• Spring 2009

2
Whats going on here?

• Airport design requires a good deal of thought.
• One issue is how wide to make taxiways. Narrower
  is cheaper and can reduce ground taxi delays by
  allowing more compact layouts, but wider is
  safer.
• Here Boeing used FAA funding to study how well
  Boeing 747s at JFK airport could stay in the
  middle of taxiways Alpha and Bravo.
• There is a lot of attention to estimating
  probability density functions and, from those,
  computing probabilities of large deviations from
  the taxiway centerline.
• The normal distribution is used throughout. So
  are other distributions (extreme value
  distributions) that have fatter tails.

3
Note that the guide lights are to the right
of the yellow line. Combine this with the
pilots not sitting in the middle of the plane,
and it can be hard to stay in the middle. In
the picture, the nose wheels are not aligned with
the yellow centerline.
4
Lasers gave 5 distance readings from the edge of
the taxiway to the wheels of the 747s. These
plots show the distribution of the range of these
5 distance measurements. These plots suggest
that the range might be well modeled with an
exponential distribution.
5
Deviations from the centerline have approximately
a normal distribution. The center of
the distribution is not zero, indicating
a consistent offset.
6
A closer look shows that the deviations are not
normal they have fatter tails. This is hard to
see in the histogram but easy to see in the
normal probability plot.
7
The normal distribution is used to calculate
the probabilities of large deviations to the
right or left. Offsets from the middle translate
into different probabilities of
crossing thresholds. The exceedance probabilities
are small, but are they small enough for safety
at a busy airport?