ICAO Annex 2, Rule of the Air.
Ch. 3.6.5.2.1, pag. 3-8.
3.6.5.2
Communication failure. If a communication failure
precludes compliance with 3.6.5.1, the aircraft shall comply
with the voice communication failure procedures of Annex 10,
Volume II, and with such of the following procedures as are
appropriate. The aircraft shall attempt to establish communications
with the appropriate air traffic control unit using all other
available means. In addition, the aircraft, when forming part of
the aerodrome traffic at a controlled aerodrome, shall keep a
watch for such instructions as may be issued by visual signals.
ICAO Annex 2, Rule of the Air.
Ch. 3.6.5.2.1, pag. 3-8.
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