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Mandatory / minimal IFR equipment for Europe

IFR aircraft with no DME or ADF

What puzzles me is how Cirrus managed to sell thousands of SR20s and SR22s (mainly SR22s) with no DME.

It's true that in the USA an IFR GPS can substitute for a DME, but this is not true if the flight requires an alternate airport (according to the 1-2-3 rule) to be planned, and that alternate airport requires a DME for its non-GPS approaches.

The exception to the above is if the GPS is a WAAS GPS, in which case it can substitute for the DME anyway. But WAAS GPSs came in quite late into the Cirrus "sales cycle".

Is the "alternate" really a non-issue in the USA? Is it the case that almost in every case, the alternate has ILS/VOR/LOC approaches and no DME is required? It's apparently not the case for my KCHD example below.

One argument I read, from a prominent US forum owner, was that once you decide to fly to the alternate then the alternate becomes your main destination, and the above rule doesn't apply. I think that is rubbish; the alternate has to be nominated at the planning stage.

What is slightly amusing is that Cirrus sold many of these (a few hundred) to Europe where DME is universally mandatory for enroute IFR, and the ADF has been similarly (but more varyingly) mandatory, until recently in some cases. Quite a lot of them were retrofitted, but in the early aircraft the mod was a mess, with a big hole hacked in the RHS panel. I recall this from when I was looking at new planes in 2002; the Cirrus dealer (I don't recall the company) told me to ignore the regs because "GPS is a lot better". Then he walked off to talk to a less difficult customer

What is really puzzling, given all we read here about German enforcement and absolutely draconian fines, is that no enforcement appears to have taken place. We have debated issues of astronomical importance like 8.33 and whether one might get fined €500000 in Germany for carrying one 8.33 radio when two are mandated, but the "elephant in the room" has been happily flying without any bother for more than a decade.

There have been rumours in the UK of enforcement against Cirruses but enquiries always showed these rumours to have been made up on the spot.

I have no idea about Germany but my feeling is that, here in the UK, the CAA has been unwilling to test the law because "DME" is worded as "distance measuring equipment" (e.g. ref page 257 of the ANO) and a good lawyer would argue that a GPS gives you exactly that function, and if the CAA lost it would throw out all the equipment carriage regs including the ADF.

The other thing is the GPS-DME distance reading difference and how it relates to published approach plates. There are many airports (not many in the UK though) where the DME reading is significantly different to what you get from setting a "DCT airportname" on a GPS? Where I did the FAA IR (KCHD) the DME reads 8.5 at the MAP (VOR approach plate). The fact that KCHD has a GPS approach would not be relevant if it had to be nominated as an alternate.

How does all this work?

Administrator
Shoreham EGKA, United Kingdom

I don't know how it works in Europe, but the requirement for an alternate in the US is a planning requirement. If an alternate is required, you have to file one on your flightplan that meets the weather forecast and installed equipment capabilities of the aircraft. A GPS may be substituted for a DME, ADF, and in some cases for a VOR. It may not substitute for the lateral guidance on the final approach segment, but can be used to identify a fix along the final approach segment, even when the lateral guidance is based on a localizer.

When planning and filing an alternate, there are two sets of rules, depending on the type of GPS. In the case of a non WAAS GPS, the procedure at the alternate must be capable of being flown without any dependence on the GPS what so ever. If the remaining equipment sans the GPS permit the procedure to be flown, then it may be used for alternate filing purposes. This means that if the aircraft is equipped with a Non WAAS GPS, then a RNAV (GPS) or standalone GPS approach doesn't qualify. Neither will any approach that requires a DME or ADF, but none is installed and operational in the aircraft.

In the case of a compliant WAAS GPS (not all levels of software and antennas are compliant), the GPS may be used to substitute for a required DME or ADF and a RNAV (GPS) approach may be used if it has a LNAV minimum line on the procedure, the approach is approved for use as an alternate, and the weather forecast meets the non precision minimums. The RNAV (GPS) approach can not use the LPV or LNAV/VNAV minimums to meet the weather forecast requirements.

In all cases, once you arrive at the alternate airport, you may use GPS substitution and may fly any procedure for which the aircraft is equipped to any minimums. Of course, one of the procedures must already have met the more stringent requirements at the time of planning the use of the alternate.

Also, there is no requirement to use the alternate as the actual alternate. You can change your mind at any time once you are underway and do whatever makes most sense and is safest. ATC will simply ask you if you miss an approach: "Say intentions." An example where it would make sense to not fly to the alternate: The destination is below minimums on arrival, the nearby airport could not be used as an alternate, but is above minimums at the time of your arrival, the filed alternate airport is 150 miles away and fuel is not an issue. I am going to make an approach to the nearby field and get a taxi or call my wife to pick me up.

An observation, the VOR approach you referenced doesn't require DME and could be used as an alternate as long as the forecast weather at the ETA for arrival at the alternate was at least 800-2.

KUZA, United States

I have no idea about Germany but my feeling is that, here in the UK, the CAA has been unwilling to test the law because "DME" is worded as "distance measuring equipment" (e.g. ref page 257 of the ANO) and a good lawyer would argue that a GPS gives you exactly that function, and if the CAA lost it would throw out all the equipment carriage regs including the ADF.

I have not been able to find a case where a pilot was fined in Germany for not carrying a DME while on an IFR flight plan. The German law is absolutely non-ambiguous, asking for a "distance measuring equipment (DME interrogator)". The fine is up to €50k per infraction but in reality fines are mostly in the €500-€5000 region.

It's mostly an issue for N-reg obviously as a D-reg would not get an IFR release during the annual radio check. Of course nothing prevents such owners from filing IFR flight plans but I've never seen that.

There are many airports (not many in the UK though) where the DME reading is significantly different to what you get from setting a "DCT airportname" on a GPS?

You have to be very careful what you measure the GPS distance for. Usually it is clear from the approach plate and DCT airport is the ARP which is never what the DME would measure. I generally don't rely on my DME (King KDM705 designed by James Watt) but use the NRST page on my Garmin 695 showing the DMEs. From what I know, GARMIN GPS always show the ground distance and never the slant range but the difference is negligible, considering the tolerances for DMEs. My DME was broken several times in the past, some of the defects leading to incorrect distance measurements.

NC Yankee - what do you think the answer might be to my query as to whether the lack of a DME in the SR22 fleet is relevant in the USA, operationally?

I guess it isn't but I can't see why not - pre-WAAS.

An observation, the VOR approach you referenced doesn't require DME and could be used as an alternate as long as the forecast weather at the ETA for arrival at the alternate was at least 800-2.

I can see SECKA FACTA ARULY are also defined as VOR radials, but the MAP needs the 8.5D, no?

GPS always show the ground distance and never the slant range but the difference is negligible

Yes; I don't think the slant range error is ever a practical issue.

The "DCT to the airport" is probably the middle of the principal instrument runway...

Administrator
Shoreham EGKA, United Kingdom

The "DCT to the airport" is probably the middle of the principal instrument runway...

From what I know it's the ARP (aerodrome reference point), which is kind of arbitrarily located but listed on most Jeppesen plates.

NC Yankee - what do you think the answer might be to my query as to whether the lack of a DME in the SR22 fleet is relevant in the USA, operationally?

I guess it isn't but I can't see why not - pre-WAAS.

It is a minor limitation for the pre-WAAS units. One may have to use a towered airport for an alternate. Some approaches may be ruled out because of equipment requirements, but usually there are choices available within 100 NM of your destination.

An observation, the VOR approach you referenced doesn't require DME and could be used as an alternate as long as the forecast weather at the ETA for arrival at the alternate was at least 800-2.

can see SECKA FACTA ARULY are also defined as VOR radials, but the MAP needs the 8.5D, no?

No. If it did, there would be a note on the procedure: DME required. The timing table is listed on the procedure so that the final leg can be timed. DME is simpler, but not required. BTW, if DME were required, usually the timing table would not be printed on the chart. See http://155.178.201.160/d-tpp/1303/00076ILD33.PDF as an example. The DME is required for the LOC only procedure and for the full ILS only because the missed approach hold is only defined by DME.

KUZA, United States

From what I know it's the ARP (aerodrome reference point), which is kind of arbitrarily located but listed on most Jeppesen plates.

In the US, the ARP is defined as:

AIRPORT REFERENCE POINT (ARP) The approximate geometric center of all usable runway surfaces.

KUZA, United States

OK; interesting.

This is relevant to N-regs in Europe too. If they have a non-WAAS GPS installation (which is what the vast majority will have) they cannot file as an alternate an airport for which they do not carry the required non-GPS approach equipment.

So a non-WAAS plane, not having ADF or DME, cannot file as an alternate (if an alternate is required according to the FAA 1-2-3 rule) an airport which has a GPS approach and whose other approaches all require ADF or DME.

Quite subtle

Administrator
Shoreham EGKA, United Kingdom

Peter,

You are correct.

I minor unrelated technical point, the 1-2-3 rule applies to a destination that has an instrument procedure. If the destination airport is strictly a VFR airport, but you file it as your IFR destination, then you are required to have an alternate, regardless of the weather. This provides you a backup in case the weather deteriorates to below VFR from your lowest enroute IFR altitude. Some claim that even if there is an instrument procedure available at the destination, but your aircraft is not equipped to fly it, the airport is for all intents and purposes a VFR airport for you, and you are required to file an alternate. The strict reading of the regulation doesn't state this, but it is a reasonable conclusion.

In the US, there isn't a technical reason that a stand alone GPS approach (titled GPS) couldn't be used as an alternate for a WAAS equipped aircraft, but so far, none have been approved as an alternate unless they are titled RNAV (GPS). The RNAV TERPS standard permits it, whereas the older GPS standard doesn't. There are very few GPS stand alone approaches remaining in the US as the vast majority have been converted to the RNAV standard.

KUZA, United States

I generally don't rely on my DME (King KDM705 designed by James Watt) but use the NRST page on my Garmin 695 showing the DMEs.

The potential problem with this is when the DME is used with a localizer and is zeroed to the runway threshold....as is commonly the case in the UK

YPJT, United Arab Emirates
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