Just a quick question: On the Cessna 172 SP cockpit panel in the middle on top you have 3 lights with 'O M I' written on them.
What are they?
O - Outer Marker
M - Middle Marker
I - Inner Marker
They refer to markers on the approach path as a means of gauging your position on the approach path (i.e. distance from the runway threshold). On commercial flights, ATC may often say, report at outer marker to keep an even flow of traffic and knowing the traffics location at a specific point.
I've only been flying VFR, never used ILS systems or something like that, so now I know why I didn't know! 😎