Editing Distress signal (section)

== Aviation ==
{{Listen|filename=Radio beacon of distress on 121,5 MHz.ogg|title=Radio beacon of distress|description=Modulation of a radio beacon of distress on 121.5&nbsp;MHz and 243 MHz. (Radio triangulation)|format=[[0]]}}
The civilian [[aircraft frequency]] for voice distress alerting is 121.5&nbsp;MHz. Military aircraft use 243&nbsp;MHz (which is a [[harmonic]] of 121.5&nbsp;MHz, and therefore civilian beacons transmit on this frequency as well). Aircraft can also signal an emergency by setting one of several special [[Transponder (aviation)#Transponder codes|transponder code]]s, such as 7700.

The COSPAS/SARSAT signal can be transmitted by an Electronic Locator Transmitter or ELT, which is similar to a marine EPIRB on the 406&nbsp;MHz radiofrequency.  (Marine EPIRBs are constructed to float, while an aviation ELT is constructed to be activated by a sharp deceleration and is sometimes referred to as a Crash Position Indicator or CPI).

A "triangular distress pattern" is a rarely used flight pattern flown by aircraft in distress but [[NORDO|without radio communications]]. The standard pattern is a series of 120° turns.

=== Ground Air Emergency Codes ===

[[File:Ground-Air Visual Code for Use by Survivors.png|thumb|Visual code used by survivors in the U.S.]]

[[File:Ground-Air Visual Code for use by Ground Search Parties.png|thumb|Visual code used by ground search parties in the U.S.]]

Ground-Air Emergency Codes are distress signals used by crashed pilots and military personnel to send signals from the ground to an aircraft.<ref>The Handbook Of The SAS And Elite Forces. How The Professionals Fight And Win. Edited by Jon E. Lewis. p.185-Tactics And Techniques, Evasion, Capture And Escape. Robinson Publishing Ltd 1997. {{ISBN|1-85487-675-9}}</ref><ref>{{cite web | url=https://www.offgridweb.com/survival/international-ground-to-air-signaling-code/ | title=International Ground-to-Air Signaling Code | date=December 2017 }}</ref>