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• November 2, 2016 Create Date
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National Advisory Committee for Aeronautics, Report - Statistical Measurements of Contact Conditions of 478 Transport Airplane Landings During Routine Daytime Operations

Statistical measurements of contact conditions have been
obtained, by means of a special photographic technique, of 478
landings of present—day transport airplanes made during routine
daylight operations in clear air at the Washington National
Airport. From these measurements, sinking speeds, rolling
velocities, bank angles, and horizontal speeds at the instant
before contact have been evaluated and a limited statistical analy-
sis ofthe results has been made.

The analysis indicates that, for transport airplanes in
general, the gusty-wind condition had a substantial eject in
increasing the values of sinking speed, bank angle, and rolling
velocity likely to be equaled or eaceeded once for a given number
of landings but had essentially no eject on the airspeeds at
contact. Specifically, in 1,000 landings under conditions of no
gusts, the values of sinking speed, bank angle, and rolling
velocity (in the direction of the first wheel to touch) likely to be
equaled or eaceeded once are 3.5 ft/sec, 4.8°, and 4.4 deg/sec,
respectively; for the same probability of 1 out of 1,000 landings
made under conditions with gusts, the values of these respective
quantities increase to 4.7 ft/sec, 6.6°, and 5.3 deg/sec. In
general, the transport airplanes landing at Washington National
Airport touch down at airspeeds which have a considerable
margin above the stall; in 1 out of 1,000 landings, the landing
speed will probably equal or weed an airspeed 60 percent above
the stalling speed (based on an assumed loading of 0.9 of the
maaimum permissible landing weight).

Although wing loading was seen to have some efl'ect on the
sinking speeds of various transport airplanes, that is, there was
a tendency for airplanes with higher wing loading to land with
higher sinking speeds, the actual correspondence was rather
poor, and study of a greater number of landings is required in
order to isolate the influence of wing loading and other pa—
rameters which cause the difierences in sinking speeds for the
various types of airplanes.