Procedure not available without DME

[baldwinm]

If an approach plate states that a "Procedure is not available without DME" eg Rwy 28 ILS/DME at blackpool, does this apply to the full procedure only or to a radar vectored (to ILS) approach. At Blackpool there are NDB 10 and NDB 28/Radar approaches without DME. A SRA approach is available and there is a RVA chart in the AIP (no reference to DME). So would a non DME equipped aircraft (although with GNS430) be only allowed to do a non precision or radar approach to 28, or would the ILS be o.k. if it was initially vectored by radar?

[tmmorris]

My initial instinct is that it means what it says, i.e. no DME, no approach, though we all know that there are plenty of people out there using GPS for the DME reading without saying anything.

Some approaches say in the notes 'No DME: radar ranges will be passed at Xnm outbound and Ynm inbound); not at Blackpool, I see. Only the NDB/DME actually says 'DME mandatory', though, on my set of charts (AERAD), presumably because of the high ground to the east.

Interesting to note that the Manston LLZ/DME/NDB approach to Rwy 10 says:


3. NO DME. Advise ATC. Rdr Ranges given at 10nm outbound and 7nm & 5nm inbound...
4. DME mandatory


which makes little sense...

Final thought: why not just get an SRA? Or do you have an IR so can go to 200ft on the ILS (SRA minimum for 28 being 500ft)?

Tim

[High Wing Drifter]

There are no timings offered for the ILS so a DME is required for the proceudre, you would be restricted to the NDB approach procedurally. However, my general understanding is that a vectored ILS would be ok sans DME as you would be given radar ranges anyway. Certainly no requirements for a DME for the SRA as the required timings from SRA termination at 2nm to MAPt.

tmmorris,

I would interpret the contradiction as meaning that either radar ranges or DME is required for the procedure to be available. I still can't decide if I prefer Aerad, Jepp or AIP. Although Aerad tries to be the most helpful there seems to be the odd funny in there. Jepp is bit cluttered and yet still minimal. The AIP usually resoves problems with the former!

[baldwinm]

Tmmorris

Unfortunately I don't have an IR - and I don't want to start the IMC rating advisory or mandatory minima debate again :)

If it is as you suggest than the SRA is probably the easier option.

[javelin]

Only you know that you don't have a DME and as you say, the 430 can generate it so go for the ILS every time :E

[tmmorris]

Have you done an SRA before? It wasn't part of my IMCR training (presumably because you can't use it on the test (has to be pilot-interpreted)) but it is very easy and much the nicest kind of cloudbreak. Gloucester do them free if you land from them (i.e. you pay approach fee or landing fee but not both) and are usually happy to do one if you ring first.

PAR even better but we don't all have the advantage of operating from a military AD.

Tim

[baldwinm]

Tim

Yes, I have done a (practice) SAR. During my original IMC training I did a PAR into Waddington. I did think at the time that in a slow light aircraft a survivable arrival could probably be achieved from a PAR in conditions of very low visibility indeed.

Malcolm

[DFC]

The procedure is not available without DME regardless of how one is positioned onto the LOC.

The easiest way to see why this is the case is to look at the NDBDME28 procedure and then at the RADAR NDB28 procedure.

While one could think that radar could fix the distance from touchdown as accurately as the DME, but this is very dependent on the radar performance, how the procedure has been designed and if radar fix was considered at the design and approval stage.

You will see from looking at both procedures that the minima for the Radar NDB (which you might expect to be the same as the NDBDME) are the same as the crossing height of the 3DME step-down fix height on the NDBDME.

Without having access to the design info, one would expect that the radar performance is such that it can not be used to provide fixes close in or that this was simply not checked.

Even the last fix on the SRA is at 2nm with the pilot having to time the final part to the MAP which is at 1nm.

The ILS has a close in check fix at 0.9 DME which is also the MAP for the GS out approach. Some clutter or other issues could prevent this fix being accurately provided by radar.

To me everything points to poor radar performance close in.

As for using GPS. Remember that the DME reads zero at the threshold. Unless set for the threshold, the GPS will often read zero at the ARP.

Regards,

DFC