ADF/DME Carriage Requirements AGAIN

[Contacttower]

Hopefully our regs will change and we will move forwards in line with the more progressive aviating states in the world.

ADF is going out next year, at least that was what I was told by my IMC rating examiner.

[scooter boy]

Great news Contact Tower.
Let us hope that he is right and that it comes to pass!
SB

[IO540]

I think we can get bogged down in the "ADF enroute" argument without realising the "ADF in approaches" thing is not going to go away anyway.

I can see UK's peculiar ADF enroute requirement going away (it's hardly echoed elsewhere in JAA/EASA-land already) but I can't see the general requirement for an ADF to fly approaches in UK and Europe going away.

How can it??

There would have to be a general de-commissioning of NDBs in approaches, and what they be replaced with? Almost nobody is going to replace an NDB with a VOR because a VOR costs much more to install and run. GPS is the only option, and that will happen when it happens.........

So, the discussion of doing away with the ADF totally hinges on a wholesale adoption of GPS approaches at every airport that currently has an instrument approach involving an NDB. This is going to take many years, at best.

Unless one adopts the U.S. style which is to allow an IFR GPS to be used instead of ADF and DME, and I see no indication whatsoever of this being adopted anytime soon either.

(And, don't forget, not carrying an NDB/DME in the USA does limit your legal options when it comes to alternates.)

So, while I think mandatory ADF-enroute is totally stupid, I really cannot see the slightest chance of the ADF going away for approaches in Europe for many years - IF you want half decent IFR utility from your plane.

On top of this, Cirrus owners usually want to avoid the DME too. This is much less likely to go away than the ADF. DME isn't "mandatory" on all that many approaches in Europe but the alternatives are often not available. Radar is one alternative but IME is so often temporarily unavailable at the smaller destinations; all you need is an ATCO (who is qualified and paid extra to provide a radar service) to be off sick... Timing is another alternative but frankly, in some places that have serious terrain around, I would rather know exactly where I am.

When I used to fly long legs VFR over say France I used to use the ADF as an enroute backup for the GPS. This is just handy and I would not suggest it is essential, but it does illustrate that the ADF is not useless.

[Contacttower]

I don't know the detail of it IO540....it was something the examiner mentioned in passing during the test. At the time I was more contentrating on the ADF itself to ask further questions. I quite like them in those situations when you just want something to point at your destinations, but for approaches they are just .

[n5296s]

So, while I think mandatory ADF-enroute is totally stupid, I really cannot see the slightest chance of the ADF going away for approaches in Europe for many years - IF you want half decent IFR utility from your plane.

On top of this, Cirrus owners usually want to avoid the DME too. This is much less likely to go away than the ADF. DME isn't "mandatory" on all that many approaches in Europe but the alternatives are often not available.

I don't follow this at all. GPS is an excellent alternative to both ADF and DME, both enroute and for approaches. In the US, all NDB approaches (well, no doubt there's an obscure exception somewhere) are designated so they can legally be flown with an approach-certified GPS *instead* of an ADF. There are a few approaches which require DME and aren't designated to allow GPS as an alternat(iv)e, althugh since DME is never fitted to new aircraft I guess everyone either flies another approach or just uses GPS anyway. GPS is *always* legal where ADF/DME are needed only as part of the missed.

I guess the belief in the UK (by the CAA and by pilots) is that IFR-capable GPS units are rare exotica, that nobody who doesn't regularly fly above FL095 could ever conceivably have. Whereas in fact practically all new planes have them. Even the new Cessna 162 has a glass panel!

I did hang on to the ADF that came with my plane for a while, it had a useful timer and it was always set to point to my home airport, which conveniently has a 50kW AM station close by. But when its power supply went on the blink, I used the panel hole for a backup AI. You'd have to be crazy or desperate to fly an NDB approach just by the ADF in actual (yes, I know airliners routinely do it in places like Albania, but it doesn't change my sentiment).

n5296s

[tmmorris]

You'd have to be crazy or desperate to fly an NDB approach just by the ADF in actual

Absolutely. I don't have an IFR GPS in the ac I fly most often, so I carry a hand-held one. But I still fly NDB approaches on the handheld GPS, backed up by the ADF/DME, and I defy anyone who says that is more dangerous than flying by reference to the ADF and stopwatch alone. (Even the CAA... or DFC...)

Tim

[Contacttower]

I defy anyone who says that is more dangerous than flying by reference to the ADF and stopwatch alone. (Even the CAA... or DFC...)

I would draw the line at NDB/DME approaches...NDB alone is just too hardcore. I noticed the other day when SAM at Southampton was out and the ATIS was stating 'NDB/DME approach' most aircraft were just asking for visual...no suprise really.

[DFC]

tmmorris,

Once again a "I can't do it so everyone else is crazy to even attempt it" puff the chest out statement.

If the NDB and timing says one thing and the VFR only handheld GPS says another while in IMC, what are you going to do other than go-arround?

Thus you are simply cross-checking the primary ADF/timing aid. You are not using an alternative approach aid.

If however, you would continue using the VFR only handheld GPS then why bother to tune the ADF in the first place, you are breaking the law (reckless) from the moment you ignore the GPS manufacturer's warning.

---------

n5296s,

Many aircraft have various pieces of equipment fitted. However being fitted and being certified for IFR use is something different altogether.

GPS replacing DME can cause problems for when dealing with a DME associated with an ILS. the DME station will be lolcated to one side of and about half way along the runway strip. The responses are adjusted so that the indication is 0 in a circle about the station that crosses both thresholds. Now using your GPS do you use the station as the zero point or threshold 1 or threshold 2. The answer of course is that it depends on if you are enroute (makes little difference) or making an approach (need the approach end) or departing (need the departure end).

Thus the "replacing DME" is not 100% accurate.

--------

IO540,

The price of VORs are dropping rapidly. There is the issue of calibration and maintenance but they offer lower minima and better options from an ATC point of view in a procedural environment. The DMEs are not going to go away because many aircraft use DME/DME for RNAV and for that reason many VORs are being turned off while their associated DME will remain.

Regards,

DFC

[Contacttower]

To recap though I think we have established that it is the law that one needs ADF and VOR/DME to operate IFR in CAS.

The price of VORs are dropping rapidly.

Well in that case when Southampton decide to sell SAM, I'll buy it and stick it in my garden... then I could have my own IAP to my own field and what the CAA thinks.

[tmmorris]

DFC, like many before me I am moved to wonder if you've ever flown an aircraft, and in this particular case whether you've flown an NDB approach in IMC. Least of all at Gloucester or Shoreham.

Are you suggesting, by the way, that the NDB might be so inaccurate that it and the GPS might disagree violently? If so, why on earth are we basing approaches on them?

And I never said I couldn't do an NDB approach based solely on the ADF. Indeed, if you consult the CAA records you will find that I have held an IMC rating since 2003 and have demonstrated my ability to do so therefore to an examiner on three separate occasions. I just said I wouldn't.

Tim

[n5296s]

Once again a "I can't do it so everyone else is crazy to even attempt it" puff the chest out statement.

Huh? I've certainly flown NDB approaches, I even did one on my IFR checkride. Much to my own and the examiner's amazement, I came out with the nose pointing at the runway. Statistically, this is highly improbable. (Think about the lateral error with 1% compass accuracy and 1% pilot error following the 1% compass error - both of which are pretty good going - and the NDB 5 miles off the approach end of the runway). I've even flown them to minimums. I can't any more, because even if I still had my ADF, all the NDB approaches within 100 miles of my home base have been decommissioned.

But all that said, if conditions were down to minimums, unless the terrain was extremely favourable (which I guess it always is in the UK), I'd divert somewhere with a nice friendly ILS rather than fly an NDB approach without GPS.

(item about DME accuracy, which I can't readily quote)

If that is the case (which would imply that the DME antenna must be exactly half-way down the runway, which I suspect is rare in practice) then I guess that nice Mr Jeppsen and Mr Garmin have figured that out and adjusted the readout accordingly, when I am showing simulated DME from a localizer. Most approaches that use DME are actually doing DME off a VOR rather than the localizer - although there are exceptions.

n5296s

[DFC]

If that is the case (which would imply that the DME antenna must be exactly half-way down the runway, which I suspect is rare in practice) then I guess that nice Mr Jeppsen and Mr Garmin have figured that out and adjusted the readout accordingly

No. Think about it for a few seconds. The DME only has to be equidistant from both thresholds. It is very common - ILS at both ends (same frequency but different idents) using a switchover but 1 DME for both ends.

I am aware on a number of commercial operators who are having problems with the Jeppesen database for the ILS DME used for the departure runway. On a SID, the procedure specifies a turn at x distance by reference to the DME. However, the FMS can turn one early (by the length of the runway) because the DME reads 0 at the departure end but the FMS location for 0 DME is the approach end.

It is being monitored and also being worked on by Jeppesen but the final solution has yet to be decided.

------------

tmmorris,

Yes I have been to both places and used the NDB at both places. However, you have missed the important point - if the GPS says something different from the ADF your only option is to not trust both of them because you can not put more faith in a VFR handheld GPS unit than in a certified ADF (even with the errors).

Put another way, if by following the handheld VFR GPS you leave the +/-5 on the ADF, you are legally guilty of reckless endangerment despite the outcome.

I hear all the time on here about ADF problems. I must ask how many MORs have been filed when the ADF was giving dangerous indications. After all if you find an approach aid is dangerously out, you have an obligation to report it.

Most people get their compass swung when required. However, few seem to get their ADF swung and from my experience, most ADFs are inaccurate simply because the ADF has not been serviced properly and has not been swung to check it.

Regards,

DFC

[n5296s]

No. Think about it for a few seconds. The DME only has to be equidistant from both thresholds. It is very common - ILS at both ends (same frequency but different idents) using a switchover but 1 DME for both ends.

Well, of course I didn't mean that the antenna was actually in the middle of the runway, just (to be pedantic) located on a line perpendicular to the centre of the runway.

Now I understand what you're saying about the DME "trick", I don't understand how it actually works. What this means is that the DME would read negative if you're between the threshold and the antenna. Wouldn't that mean it would have to send its response pulse before it received the interrogation?

n5296s

[Fuji Abound]

Huh? I've certainly flown NDB approaches, I even did one on my IFR checkride. Much to my own and the examiner's amazement, I came out with the nose pointing at the runway.

Yep, they work well. It is just they are harder to fly well and so often the kit in the iarcraft does not work properly.

Wait and see, I think you will find type exemptions will be with us very shortly. .

[CJ Driver]

Now I understand what you're saying about the DME "trick", I don't understand how it actually works. What this means is that the DME would read negative if you're between the threshold and the antenna. Wouldn't that mean it would have to send its response pulse before it received the interrogation?

It works because a "normal" DME reply includes a fixed standard delay to allow for ground station processing. By reducing the delay you can "subtract" some distance, and make the DME appear closer than it really is. By putting the ground station equidistant to the two thresholds and subtracting delay equal to half the length of the runway, the DME reads "zero" at the threshold. And yes, after you have landed you will be into "negative" territory - next time you are at an airport with such an installation, take a look and you will notice that the DME will lose lock when you are closer to the ground station than half the runway length.

[Sir George Cayley]

The Good News

My man at the CAA tells me it is planned to submit proposals to remove the ADF carriage requirements from the UK ANO in 2008.

There is a mid-year reissue planned, so it could be in that (or not in there for those pedants eager to point out that removal will cause an absence of words)

Of course, the dreaded public consultation and Regulatory Impact Assessments will no doubt add delay and apparently the work is bound up with other policy changes on airspace etc.

Nevertheless, if you are planning to take delivery of your Cirrus or Cessna 400 Columbia next summer you won't need to worry about getting a hole cutter from B&Q for the ADF dial.

And those of you filing IFR and putting "ADF inop" in the free text box won't have to hold crossed fingers behind your backs

Suggest someone keeps a lookout for the web notification and we all vote yes when the time comes.

BTW don't wait for SAM to come on the market. Compton NDB is on Ebay.
That's Abbas not the NATS one before TELS spit their coffees out!

Sir George Cayley

[Contacttower]

BTW don't wait for SAM to come on the market. Compton NDB is on Ebay.
That's Abbas not the NATS one before TELS spit their coffees out!

So that's why I couldn't find it the other day!

Although I can't find it on ebay either at the moment...

[glazer]

ADF requirement

It has recently been reported (AOPA magazine) that the CAA are intending to drop the ADF requirement for flying IFR in CAS early 2008. If true, then good riddance to an old-fashioned, outdated, unnecessary and actually potentially dangerous instrument.

[glazer]

ADF problems

Are you suggesting, by the way, that the NDB might be so inaccurate that it and the GPS might disagree violently? If so, why on earth are we basing approaches on them?


Some years ago I tried a practice NDB approach into Gloucester. Fortunately it was in VMC because the needle in fact guided me in the opposite direction to what was intended and had I been doing this for real in IMC I would have eneded up in the hills. The problem was caused I believe by interference from a radio station in France. NDB approach in using an ADF down to minimums, no thanks.

[IO540]

As I keep repeating the ADF may go away as a mandatory enroute carriage requirement but it won't go away for approaches.

So, by all means chuck it out but then you won't be able to fly a huge number of approaches around the UK and Europe, for the foreseeable future.

In practice, most smart pilots know the NDB/ADF is a load of crap when it comes to accuracy and they fly NDB approaches using either the GPS overlay or using the OBS mode of the GPS, just checking the ADF at the start of the descent. This is legal because the regs don't state what equipment is to be used (and AFAIK flying an NDB approach using the FMS is a SOP in the airline business) but IMHO flying an NDB approach without carrying an ADF is probably illegal, especially in CAS.