Which description matches the HUD status 3/4?

• A. 4 green lights 100%-75%
• B. 3 green lights 74%-50%
• C. 2 middle lights flashing yellow 49%-36%
• D. Flashing red 35%-0%

Answer: (B)

HUD indicators show how much air you have left by the number of green lights that's lit. When three green lights are on, that corresponds to about 74% to 50% of the air remaining. That puts you in a caution zone: you still have usable air, but you should monitor it closely and start planning to exit or switch to a fresh air supply as soon as feasible. Other patterns mean different ranges: all four green lights indicate 100%–75% air, two middle lights flashing yellow indicate 49%–36%, and a flashing red pattern indicates 35%–0%.