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volunteered by controllers. Pilots should also be
prepared to provide a descriptive runway condition
report to controllers after landing.
AIM 2/14/08
4-3-8 Airport Operations
4-3-9. Runway Friction Reports and
Advisories
a. Friction is defined as the ratio of the tangential
force needed to maintain uniform relative motion
between two contacting surfaces (aircraft tires to the
pavement surface) to the perpendicular force holding
them in contact (distributed aircraft weight to the
aircraft tire area). Simply stated, friction quantifies
slipperiness of pavement surfaces.
b. The greek letter MU (pronounced “myew”), is
used to designate a friction value representing
runway surface conditions.
c. MU (friction) values range from 0 to 100 where
zero is the lowest friction value and 100 is the
maximum friction value obtainable. For frozen
contaminants on runway surfaces, a MU value of
40or less is the level when the aircraft braking
performance starts to deteriorate and directional
control begins to be less responsive. The lower the
MU value, the less effective braking performance
becomes and the more difficult directional control
becomes.
d. At airports with friction measuring devices,
airport management should conduct friction measurements
on runways covered with compacted snow
and/or ice.
1. Numerical readings may be obtained by using
any FAA approved friction measuring device. As
these devices do not provide equal numerical
readings on contaminated surfaces, it is necessary to
designate the type of friction measuring device used.
2. When the MU value for any one‐third zone of
an active runway is 40 or less, a report should be given
to ATC by airport management for dissemination to
pilots. The report will identify the runway, the time of
measurement, the type of friction measuring device
used, MU values for each zone, and the contaminant
conditions, e.g., wet snow, dry snow, slush, deicing
chemicals, etc. Measurements for each one‐third
zone will be given in the direction of takeoff and
landing on the runway. A report should also be given
when MU values rise above 40 in all zones of a
runway previously reporting a MU below 40.
3. Airport management should initiate a
NOTAM(D) when the friction measuring device is
out of service.
e. When MU reports are provided by airport
management, the ATC facility providing approach
control or local airport advisory will provide the
report to any pilot upon request.
f. Pilots should use MU information with other
knowledge including aircraft performance characteristics,
type, and weight, previous experience, wind
conditions, and aircraft tire type (i.e., bias ply vs.
radial constructed) to determine runway suitability.
g. No correlation has been established between
MU values and the descriptive terms “good,” “fair,”
“poor,” and “nil” used in braking action reports.
4-3-10. Intersection Takeoffs
a. In order to enhance airport capacities, reduce
taxiing distances, minimize departure delays, and
provide for more efficient movement of air traffic,
controllers may initiate intersection takeoffs as well
as approve them when the pilot requests. If for ANY
reason a pilot prefers to use a different intersection or
the full length of the runway or desires to obtain the
distance between the intersection and the runway end,
THE PILOT IS EXPECTED TO INFORM ATC
ACCORDINGLY.
b. An aircraft is expected to taxi to (but not onto)
the end of the assigned runway unless prior approval
for an intersection departure is received from ground
control.
c. Pilots should state their position on the airport
when calling the tower for takeoff from a runway
intersection.
EXAMPLECleveland
Tower, Apache Three Seven Two Two Papa, at
the intersection of taxiway Oscar and runway two three
right, ready for departure.
d. Controllers are required to separate small
aircraft (12,500 pounds or less, maximum certificated
takeoff weight) departing (same or opposite
direction) from an intersection behind a large
nonheavy aircraft on the same runway, by ensuring
that at least a 3-minute interval exists between the
time the preceding large aircraft has taken off and the
succeeding small aircraft begins takeoff roll. To
inform the pilot of the required 3-minute hold, the
controller will state, “Hold for wake turbulence.” If
after considering wake turbulence hazards, the pilot
feels that a lesser time interval is appropriate, the pilot
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