you don't need that either. I have done a few with just using the NDB on the field and the 1 in 60 rule and the ILS DME
Ok you're flying into a hypothetical airport with an NDB/DME approach. Airport elevation is 500 MSL. You have an NDB Needle and an ILS DME.
You're at 3000 MSL, flying solo at 135 KTS IAS, a heading of 360, the wind likely to be strong (about 30 KTS) and from 270-ish. Its full IMC, with a 1400ft ovc ceiling.
You've just past the last en route waypoint "BLIMY". Your DME indicates 15 NM to the NDB, your ADF needle points 40° to the left.
Your little chat with ATC results in them asking you to position yourself at the 6 NM center fix.
What heading do you turn to,
using your 1 in 60 rule ?
[My point being that I would question mental arithmetic being good airmanship in this situation. And if it is VMC, then you don't need to position on some center fix, you could fly directly to the airport.]
But its up to you to remain legal
hence my point to have a panel mounted approved GPS to do this.
@peterh :
If it is VFR panel mount or hand held, it is a great addition to situational awareness while flying the needle as a primary indication.
A lot of people say that but no law actually says that, however.
Well, if you are flying N-reg, then AIM 1-1-9 tells not to use handhelds or VFR only panel mounts for IFR navigation. The reason the FAA puts forward is the lack of guaranteed updates and/or lack of RAIM. I don't know the actual law that describes the table. The operations law bit is then regulated by §91.175, 91.181 and the catchall (forgot which one) about having to have the necessary navigational equipment to conduct the flight.