Approach chart querie (NDB V's NDB/DME)

[ooizcalling]

Had a sim check with an NDB letdown that (apparently) requires a DME as well. The chart was NOT called a NDB/DME, just NDB. It descended on a timed outbound to an intermediate level, proceedure turn to inbound leg and then down to the MDA. There was no Ground speed verses ROD advice, or any timing checks inbound. So far so good. However, the MAP was determined from a DME fix (DME co-located with the NDB site). No other method of determining or crosschecking the MAP was provided. (Nb. The aircraft Simulated, had a GPS approved for SID's, En Route, and STAR's but NOT for any approaches)

Question 1. How can this chart (Jepperson) be categorised as an NDB chart only and not a NDB/DME letdown considering the MAP required a DME to establish that point ?

On turning onto the inbound leg, the instructor failed the DME.

Question 2. With no other official method of determining the MAP, is an immediate missed approach required or being only an NDB letdown and the NDB remaining serviceable would it be OK to continue to, for example a Dead Reckoning MAP ?

The 'practical' answer might be to continue and use the GPS distance for calculation of the MAP, which is probably equally, if not more accurate, than the DME. But what about the 'legal' viewpoint. Can anyone suggest an answer to either or preferably both questions ?

( Just for info, the missed approach proceedure required a turn to avoid terrrain )

[411A]

In the USA (FAA regulations),
The DME distance can be determind from the GPS, however the GPS need not be certified for approaches, only enroute/terminal are required.
So, in these cases, the lateral navigation is not approved (or need to be, NDB used) but the "distance" must, ie: enroute/terminal.
Confusing...yes:(
Having said this, have made over a hundred GPS approaches...spot on every time:D

[galaxy flyer]

I agree with 411A. You would need the DME to determine the MAP; no DME instant missed approach. However, any turns required on the Miss would have to begin at the MAP and you can't find it except with a guess. GPS would work in FAA airspace, as 411A said.

I've seen approaches like this overseas and can't figure out why. NDB/DME, sounds pretty stupid. If you have the DME, why not fly a VOR/DME or TACAN (mil only)approach. It's rare that the DME would work but no VOR azimuth. I flew night cargo eons ago and we used to joke about the NDB Glide Slope approach when we lost the LOC receiver. Stupid then, stupid now.

[OzExpat]

There are some places in the world where VOR installations are rare. Thus, you'll usually find a predominance of NDBs. These places will often have a DME, but not always. And, to cap it off, navaid serviceability can sometimes be a major problem.

It is therefore conceivable to find an NDB-based approach that may or may not require use of DME. If DME is mandatory for any part of the approach, it's failure demands an immediate missed approach.

As has already been pointed out, it is necessary to track to the MAPt before turning to follow the missed approach. It is not unusual to find a lack of information on how to identify the MAPt when you can't identify it with conventional navaids. That's when you earn your money by taking your best shot at identifying the MAPt and, if I was in that position, I would certainly consider using GPS distance information - after making due allowance for any distant discrepancy that existed prior to failure of the DME.

[planett]

I would like to point out that in some areas of the world, stand alone DME stations are not uncommon, that is, no VOR or TACAN associated. They are usually nearby the NDB station or co-located, and provide extra info for the NDB approach. Some may actually be incorporated in the approach with different minima published for DME U/S. Some may allow a straight in approach as an alternative to the full procedure, then allowing for self calculated approach profiles.

Missed approaches are usually at the NDB itself since circling approaches are common. If not, they are based on timing alone or timing with DME as an option. I have never seen an NDB approach with the missed determined by DME only. I would think this approach is mis named.

They were installed presumably to allow the controlling agency to query high level aircraft of their position in the vast areas of Canada's north where there is no Radar Coverage. They have the added benefit of allowing uncontrolled aircraft to separate themselves using distance, bearing, altitude, and the comm radio for position reports.

Sadly, I fear these stations will be decommissioned as NavCanada assumes everybody has GPS.

[Rumbo de Pista]

I think your problem boils down to Jeppesen (check spelling above!!).

Some of the worst charts in the world!

However, a thorough understanding and brief should cover you.

Could you not, in good-ish weather, fly down to beacon height and use that as you MAP? Or do a rapid descent from the beacon to minimum, and if not visual, go-around immediately, using Commander's discretion to judge that you MUST have been inside the MAP?