Flying DME Arc, lose DME, now what?
 

Hey I have a Skywest interview soon and one of the gouges lists one of the possible questions as:

You are flying a DME arc in IMC and you lose DME. What do you do?

Does anybody know the right answer? I know in the real world I'd tell ATC and ask for vectors to set up for another approach, but what should the correct interview answer be?

And if you're at non-radar approach controlled Helena, Montana, served by SKW, flying the DME arc, what will you do?

You have to break off the approach because one of the required navigation facilities is not working. If you were on an ILS and lost glide slope you would discontinue the approach but continue to the missed approach and go missed.

However on a DME arc it is not quite so clear. The ARC is there to protect you from an obstruction or other traffic so you can't turn towards the missed approach point and then go missed (you might hit something)

It still seems to me even in a non radar control environment you break off the approach. Contact ATC for more instructions while climbing to MSA (via what heading or direction though?)

It's really not that clear. :confused:

I would say turn direct to the VOR, climbing to the missed approach altitude, then execute the missed. DME arcs are designed to keep you away from high terrain outside the arc, not inside the arc. If there was high terrain inside the arc, you wouldn't have picked up the DME in the first place.

If asked such a question in the interview, my first response would be "do I have any approach certified area navigation equipment onboard (that's a fancy way of saying FMS/GPS).

If so, you don't need the DME.

What about situations where the VOR/DME is located on a hillside and the airport is in a valley? I personally wouldn't assume anything... especially if you're outside of the US.

The best thing to do is call ATC and ask for instructions/vectors. Even in a non-radar environment, they can provide minimum safe altitudes for whatever sector your in.

On GA aircraft a certified GPS can also substitute for DME. You would have this already set up as supporting nav gear anyway, so just use that.

Good point.

Yeah and fly what heading or direction? I've seen ATC so busy that it could take 1 to 2 minutes to get a word in?

It would be nice if part 121 aircraft had GPS but 95% of the aircract at Mesa have no GPS. Without DME you would have no distance information.

Climb to the MSA that appears on the approach plate. This is the quickest way to assure terrain separation. Then you can proceed to the missed approach point or to the holding pattern depicted on the missed approach. Notify ATC as soon as practical but remember, Aviate, Navigate, then Communicate.