Lost Procedures, Visibility and Curvature of the Earth
C172 — N608DL — Santa Ana > (practice area) — Performance T/O, Stalls, Landing — 1.3hrs
The rules state we need 3 miles visibility to fly.
But that's cutting way down from what we can really see. On an average clear day, we can see about 30 miles. It's the fog, smog and humidity that cuts it down.
And get this, given that same clear day, as you go up in altitude you can see more. Lot more. (Better for VOR reception as well.)
Here's the formula for a quick calc:
Formula: D = 1.22 √ h
where d is in miles and h is height above ground level in feet.
from Height (ft) Distance (miles)
Example: at 6ft = 3 mi
Example: at 100ft = 12mi
Example: at 1200ft = 42mi
Example: at 3500ft = 72mi
Example: at 8000ft = 109mi
Example: at 30000ft = 211mi
So the virtue here is in being able to see more, which is always a good thing, but in Lost Procedures, it's a really good thing.
The basic Lost Procedure is Climb, Conserve, Communicate.
But my version of the Lost Procedures is a little different and more expanded (all C's):
- Stay Cool, Calm, Collected,
- Circle around as you Climb,
- (if you really are lost) do NOT Continue forward (hoping for reorientation),
- use the Compass and pilotage and all navigation means to Contemplate your location,
- Conserve altitude speed fuel time visibility,
- Communicate with available resources such as Tower etc.,
- and Coordinate your best options if you've deviated too far and must divert.
That's a mouthful, I know, but follows advice from lot of experienced CFIs.
Just try not to get trapped on top of a cloud canopy, and find yourself lost.