TM106101(8/01)
RDR-1600 Pilot’s Guide
55
Advisory Circulars (Cont.)
54
RDR-1600 Pilot’s Guide
TM106101(8/01)
Advisory Circulars (Cont.)
ADVISORY CIRCULAR
AC 20-68B
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration, Washington, D.C.
Recommended radiation safety precautions for ground operation of
airborne weather radar.
Initiated by: AFO-512
PURPOSE
This circular sets forth recommended radiation safety precautions to be
taken by personnel when operating airborne weather radar on the ground.
CANCELLATION
AC 20-68A, dated April 11, 1975, is canceled.
RELATED READING MATERIAL
• Barnes and Taylor, Radiation Hazards and Protection (London: George
Newnes Limited, 1963), p. 211.
• U.S. Department of Health, Education and Welfare, Public Health
Service, Consumer Protection and Environmental Health Service,
“Environmental health microwaves, ultraviolet radiation and radiation
from lasers and television receivers – An Annotated Bibliography”, FS
2.300: RH-35, Washington, U.S. Government Printing Office, pp. 56-57.
• Mumford, W.W., “Some technical aspects of microwave radiation haz-
ards”, Proceedings of the IRE, Washington, U.S. Government Printing
Office, February 1961, pp. 427-447.
BACKGROUND
Dangers from ground operation of airborne weather radar include the
possibility of human body damage and ignition of combustible materials by
radiated energy. Low tolerance parts of the body include the eyes and
testes.
PRECAUTIONS
Management and supervisory personnel should establish procedure for
advising personnel of dangers from operating airborne weather radars on
the ground. Precautionary signs should be displayed in affected areas to
alert personnel of ground testing.
AC 00-24B
1/20/83
b. If you cannot avoid penetrating a thunderstorm, following are some
do's BEFORE entering the storm:
(1) Tighten your safety belt, put on your shoulder harness if you
have one, and secure all loose objects.
(2) Plan and hold your course to take you through the storm in a
minimum time.
(3) To avoid the most critical icing, establish a penetration altitude
below the freezing level or above the level of -15°C.
(4) Verify that pitot-heat is on and turn on carburetor heat or jet
engine anti-ice. Icing can be rapid at any altitude and cause almost in-
stantaneous power failure and/or loss of airspeed indication.
(5) Establish power settings for turbulence penetration airspeed rec-
ommended in your aircraft manual.
(6) Turn up cockpit lights to highest intensity to lessen temporary
blindness from lightning.
(7) If using automatic pilot, disengage altitude hold mode and speed
hold mode. The automatic altitude and speed controls will increase
maneuvers of the aircraft thus increasing structural stress.
(8) If using airborne radar, tilt the antenna up and down occasional-
ly. This will permit you to detect other thunderstorm activity at altitudes
other then the one being flown.
c. Following are some do's and don'ts during the thunderstorm pene-
tration:
(1) Do keep your eyes on your instruments. Looking outside the
cockpit can increase danger of temporary blindness from lightning.
(2) Don't change power settings; maintain settings for the recom-
mended turbulence penetration airspeed.
(3) Do maintain constant attitude; let the aircraft "ride the waves."
Maneuvers in trying to maintain constant altitude increase stress on the
aircraft.
(4) Don't turn back once you are in the thunderstorm. A straight
course through the storm most likely will get you out of the hazards most
quickly. In addition, turning maneuvers increase stress on the aircraft.
WILLIAM T. BRENNAN
Acting Director of Flight Operations
