Is there a specific reason that Airbus chose to shorten "LOW" to "LO" for the lowest autobrake setting?
Wouldn't it be more consistent to use three letters for each setting?
Aviation Stack Exchange is a question and answer site for aircraft pilots, mechanics, and enthusiasts. It only takes a minute to sign up.Sign up to join this community
Boeing 747 wiper knob showing LO; source: alamy.com
As shown above, it's not unique to Airbus, or to just airliners, so from that perspective:
Example A320 ECAM messages:
- CAB PR LO DIFF PR
- ELEC IDG 1 OIL LO PR
- FUEL CTR TK PUMP 1 LO PR
- FUEL L WING TK LO LVL
- HYD B RSVR LO LVL
Note: Messages on displays are abbreviated to save space, and are in all caps for readability (see: Why do aircraft cockpit displays use uppercase fonts?).
It wouldn't make sense to deviate just for the auto brake (its ECAM indication is also LO).
That labeling is also typically electroluminescent, so the fewer the letters the cheaper (not just for LO, not just for airliners).
$^1$: FAA AC 20-175 - Controls for Flight Deck Systems
Labels are the most common means used to identify and describe controls and other devices in the flight deck. They can be full text (e.g., "Standby"), abbreviated text (e.g., "STBY"), acronyms (e.g., "AGL" for "Above Ground Level"), as well as icons (e.g., [icon example] for "On/Off").
Control labels must be visible, legible, and understandable for the population of pilots that will use the controls, per § 2X.1555(a).
Use only one abbreviation and/or one icon for labeling a function. This is to prevent confusion when a label appears in multiple locations. [emphasis added]
The AC also references SAE standard ARP 4105B Abbreviations, Acronyms, and Terms for Use on the Flight Deck (paywall), and ICAO Doc 8400.