Spoiler alert ... Houston, I think we have a problem.

The CAP training for ground-air distress signals for the CAP people on the ground lists the 5 internationally standard (line-style) distress signals[1], the first (and arguably most important of which) is:

"V" for "require assistance"

The CAP training for the line-style) ground-air distress signals for the airman tasked with looking for them (Mission Scanner)[2] ...

Doesn't list "V" at all!

What we have here is a (rather appalling) failure to communicate. The remaining four standard signals are included in the 25(!) signals taught to mission scanners, but the scanner is given the incorrect definition for a second one. The standard definition of "X" is "Need Medical Assistance" and the scanner is taught the archaic definition[3] that "X" means "Unable to Proceed", which could be a fatal miscommunication. (I sent a note to the CAP academy pointing this out - hopefully they have an errata sheet or something.)

[1] The 5 line-style distress signals taught the "ground people" are precisely those listed in these references:

(a) "Joint Pub 3-50: National Search and Rescue Manual Volume I: National Search and Rescue System", 1 February 1991, Appendix C: Emergency Signals, page C-2, where they are listed as "IMO/ICAO" signals (IMO == International Maritime Organization; ICAO = International Civil Aviation Organization) in the figure: "Figure C-1. Surface-Air Visual Signal for Use by Survivors" This document is at http://www.dtic.mil/docs/citations/ADA357500
and a searchable version at www.public.navy.mil/surfor/Documents/3-50-1_Vol1.pdf

(b)the Feb 2018 version (hopefully current :/) of the Australian National Search and Rescue Manual, page 326, in Table D-1:2 Ground-Air Visual Signal Code for Use by Survivors, which is preceded by the words: "The following visual signals are internationally recognised. They are authorised for use in the Australian SRR."That document can be downloaded from https://natsar.amsa.gov.au/natsar-manual.asp

(c) The 15 July 1985 version of United States Air Force AF Regulation 64-4, Volume 1, Search and Rescue
SURVIVAL TRAINING, Figure 24-19, p. 471 (see p. 473 for the postural signals). This document is at http://www.dtic.mil/docs/citations/ADA325861
[The fact that this document is freely downloadable is not widely advertised. Also - great section on signal mirrors!]

[2] MS O-2021 INTREPRET EMERGENCY SIGNALS AND DEMONSTRATE AIR/GROUND TEAM COORDINATION

[3] Back in 1956, "V" was not on the list, and "X" was listed as "Unable to Proceed", but both were fixed by 1985. Here's the 1956 table: https://archive.org/stream/DTIC_ADA367029#page/n17/mode/2up/search/signals