Keep ADF or DME?

[imwithtuxedo]

As an instrument pilot looking at a new plane and if it had both a DME and ADF in the panel and you were to get rid of one with considerations for best usage for alternate approaches if GPS fails or is blacked out, which would it be and why?

 

[PeterNSteinmetz]

I decided to keep my ADF and ditch the DME. In the event of an unplanned GPS outage, VOR and DME are line of sight, while LF/MF signals (both NDBs and commercial AM stations) hug the ground.

IIRC the sparse VOR backup network in the future for Canada and the US will have full coverage only at 10,000 ft and above, which is no use if you're stuck below an icing layer, or trying to avoid embedded CB. The ADF adds a genuine extra emergency capability (low-level radio navigation after a GPS outage), while the DME does not.

I believe you may have my Foreflight overlay for the location of AM radio stations in the US for just this use? If not, available at http://steinmetz.org/peter/flying/

 

[PeterNSteinmetz]

It’s one of the means the Japanese used for navigating to Pearl Harbor, using ADF technology to a local Honolulu radio station.

And I suppose may be the way some day that aliens navigate to us to destroy those pesky humans :emoji38: