FM immunity - thoroughly confused by Pilot magazine

[tmmorris]

'Pilot' Magazine had an article on avionics this month which unequivocally stated:

If you fly with non FM Immune equipment in class A, B, or C airspace, or under IFR/IMC conditions, you are breaking the law.

This had me worried, as I was doing just that last week (IFR in IMC under the edge of the Birmingham TMA, for example), so I looked it up.

Unless I've read it wrong, only the equipment required by the ANO (Section 1 Schedule 5) has to be FM Immune, and any other equipment you may carry or choose to use is up to you? As I understand it therefore:

IFR in CAS: must have radio, transponder, ADF, DME and VOR*
VFR in CAS: must have radio
Landing in CAS: must have ILS* if airspace notified as requiring it

i.e. the ones marked * must be FM immune and only under those circumstances. And I remember a training flight where we flew through the Lyneham CTA IFR tracking CPT on a non-immune set: yes, we were in VMC, but we definitely got an IFR clearance...

Am I missing something, or was the article in 'Pilot' misleading?

Tim

[Circuit Basher]

Just had a look on the CAA Web site and Schedule 5 of the ANO seems to be the chapter and verse on this. There is an issue of GASIL from 2001 here (http://www.caa.co.uk/docs/33/srg_gad_gasil2001_01.pdf) which gives a good summary on the front cover of the situation as I understand it, which goes as follows:Non-FM immune VOR and ILS receivers must be identified with a suitably worded placard and such receivers must not be used to comply with a requirement for the mandatory carriage of radio equipment. In the United Kingdom these requirements are set out in Article 15 and Schedule 5 of the Air Navigation Order (ANO). (Commercial air transport operators with JAR-OPS Air Operators Certificates should refer also to the requirements contained in JAR-OPS.). In addition, national aviation authorities in other countries are entitled to designate airspace where approved radio equipment must be carried.

For flight under instrument flight rules (IFR) in controlled airspace the legal requirements include one VOR receiver (which must be FM immune).To conduct an ILS approach inside or outside controlled airspace, one (FM immune) ILS receiver is required. The reference in Schedule 5 to duplicated VOR equipment relates to public transport IFR flights, whether inside or outside controlled airspace.

Note:This summary does not include all the radio and radio navigation equipment required by the ANO –for which the Order itself and Schedule 5 must be relied upon.

It should also be noted that there is a separate issue here - since the introduction of EASA on 28 Sep 03, they are now the regulating authority and the aircraft equipment approval process has been changed. There is a recommendation to contact the SRG at CAA.

[tmmorris]

Yes, I found that GASIL too - that was why I went to the ANO. Interestingly there is an AIC listed in this year's LASORS on the subject, but when I looked for it on the AIS website it had vanished - withdrawn?

Not sure why the GASIL says you need FM immune ILS outside CAS, though - I can't find any justification for that in the ANO...?

Tim

[Chilli Monster]

Go back to the Pilot magazine quote. Add class 'D' and 'E' airspace to the list and then replace the word or with and and it reads right. A poorly worded statement on their part.
And I remember a training flight where we flew through the Lyneham CTA IFR tracking CPT on a non-immune set: yes, we were in VMC, but we definitely got an IFR clearance...
Then you were the bad boys for accepting the clearance. ATC doesn't know the state of the kit in your aircraft - you do and it is always the pilots responsibility to refuse a clearance which he is not entitled to accept.

Having said that did you actually state you were IFR or VFR, and did they actually give you a clearance that could have been construed as VFR or IFR? The reason I say this is my experience of Lyneham is not so much a clearance issued on the basis of flight rules as would be done in the civil world, but on the basis of what service you are receiving outside CAS. Nothing against the boys and girls there who do a sterling job, but just an observation from outside.
Not sure why the GASIL says you need FM immune ILS outside CAS, though - I can't find any justification for that in the ANO...? Think about why you need one full stop. It's all because of the protection required between ILS and radio broadcast stations which may be adjacent to the ILS band. After all - if you're doing a coupled approach then the ILS doesn't know whether it's inside or outside CAS - but it does know whether it's being interfered with or not with the associated safety ramifications ;)

[IO540]

Surely one can fly around VFR without FM immune kit - this is what flying schools do. Very few training planes are FM immune.

[Chilli Monster]

Surely one can fly around VFR without FM immune kit - this is what flying schools do. Very few training planes are FM immune.
Yes - but nobody's saying you can't. FM immunity applies to IFR operations only. VFR inside or outside CAS does not require FM immune equipment.

[tmmorris]

Thanks for that Chilli Monster - I do understand the safety implications of not having FM immune kit especially for ILS, it's just the legal side that was confusing me.

Out of interest, how many people renting from flying clubs/schools do have FM immune kit? I've never seen an FM immune radio...!

Tim

[Brooklands]

Out of interest, how many people renting from flying clubs/schools do have FM immune kit?

To the best of my knowledge, of the eleven four seaters (3 twins, 8 singles) at the club I fly at, eight (3 twins , 5 singles) have 2 FM immune radios, two have one FM immune radio, and only one has no FM immune radios. AFAIK none of the two seaters (152's) have any FM immune kit, but they don't really need it.


I've this nagging feeling that the number of FM radios you require depends on whether you have a private or public category C of A, but I'll have to do some digging to confirm that

Brooklands

[High Wing Drifter]

Here is the AIC:
http://www.ais.org.uk/aes/pubs/aip/pdf/aic/4P007.PDF

[Justiciar]

The relevant notices are here:

http://www.caa.co.uk/docs/33/CAP455.pdf

[bookworm]

Thanks for that Chilli Monster - I do understand the safety implications of not having FM immune kit especially for ILS, it's just the legal side that was confusing me.

I can't find any explicit requirement in the ANO for an ILS receiver to fly an ILS approach, nor any argument that I would feel comfortable putting forward to a court for not having one. :)

[Justiciar]

The requirement is in Schedule 5 to the ANO 2000, and is a requirement to have equipment to enable the aircraft to make an ILS approach, when landing at a 'notified' aerodrome. Since most use of an ILS will be when flying under IFR - since the pilot will not be able to comply with the VFR minima, the ILS needs to be FM immune.

[tmmorris]

Thanks High Wing Drifter - that AIC is I think the source of the confusion, and I'm still confused. It states:

Airworthiness notice AN84 describes the airworthiness requirements for VHF communications and ILS/VOR navigation receivers... It should be noted that this AN requires all equipment not meeting the new FM immunity standards to be identified as so with a placard, and their use restricted to VFR flights only.

There's nothing in the ANO to support 'VFR flights only'. You only need specified equipment to fly IFR in CAS; outside CAS you simply need whatever equipment is necessary for you to fly the intended route. That route could easily be a mixture of NDB tracking and dead reckoning, in which case you don't need FM immune VOR/ILS equipment.

It could be referring to the COM radios... but in AN84 (thanks for finding that Justiciar) it says:

Recognising the reduced risk (of interference with VHF communications), paragraph 5 of this Notice permits a relaxation from the ICAO standard for VHF communication receivers carried in aircraft of 5700kg MTWA or less.

Tim

[Justiciar]

There's nothing in the ANO to support 'VFR flights only'. You only need specified equipment to fly IFR in CAS

Sorry, but that is not correct. Look at schedule 5 to the ANO and at the table under paragraph 2 of the Schedule. An aircraft requires "Radia navigation equipment capable of enabling the aircraft to make an approach to landing using the Instrument Landing System". This applies to making an approach to an aerodrome "... notified for the purpose of this sub-paragraph".


AN84 specifies non FM Immune instruments be limited to VFR only. That means that if you are making an approach for real in non VFR (i.e. IFR) then you must have FM immune. To stay within AN84 you would have to use the equipment in VFR, which defeates the purpose of the ILS other than in cases of training. The question of controlled or uncontrolled airspace is irrelevant to the use of a VOR/ILS, though would be relevant to the use of the VOR in uncontrolled airspace under VFR, which is permitted.

[S-Works]

As much as it hurt me to upgrade my Nav/Comms to FM Immune at the end of the day if there was not a risk then there would not be a requirement to have it done.

The last thing I wanted to find on an approach in bad weather was that the indications were incorrect becuase of FM interference.

At the end of the day IFR flying requires appropriate equipment and appropriate skills/practice, FM immune is just part of it.

It cost me US$600 to have 2 x Narco Nav/Comms made FM immune hardly a huger amount of money for safety?

[High Wing Drifter]

I have been informed by an RAF engineer that the chance of there being any interference with non FM immune equipment is very very unlikely. In fact he went as far to say that in this country the risk is, at this time (a few months ago), theoretical.

I have not the knowledge to either agree or disagree with this, just wondering what the engineers in the forum think.

[tmmorris]

Sorry, talking at cross purposes. I accept that for instrument approaches (ILS or VOR) you would need FM immune NAV radios (in the real world I fly NDB or SRA approaches, in fact). What about en-route tracking of a VOR outside CAS but in IMC, though? That's an IFR flight so AN84 implies you can't do it legally, yet there's nothing in the ANO to prevent it - does AN84 override the ANO? Or does it come under the catch-all 'equipment required to complete the flight' bit?

Tim

[IO540]

High Wing Drifter

I have asked and asked and have never come across anyone who has ever heard of FM interference having actually happened.

There are much bigger problems with light aircraft these days, e.g. electric fuel pumps affecting fuel totalisers, own radio transmissions affecting oil pressure indicators, own RF emissions or power bus spikes causing autopilot crashes, landing gear pumps causing avionics malfunctions, and while these things can be extremely irritating to say the least, none of these issues are certification issues because the equipment in question is not legally required to work.

But we must be charitable! The people who bring us these wonderful regulations have families to feed, just like the rest of us. We live in a redistributive society these days :O

[High Wing Drifter]

But we must be charitable! The people who bring us these wonderful regulations have families to feed, just like the rest of us. We live in a redistributive society these days
Somehow, Dickens' Christmas Carol would not be quite the same if Tiny Tim's Dad was a CAA inspector.

:}

[Timothy]

I have two immune COMs and NAVs for sale. PM me if interested.

W

[bookworm]

Sorry, but that is not correct. Look at schedule 5 to the ANO and at the table under paragraph 2 of the Schedule. An aircraft requires "Radia navigation equipment capable of enabling the aircraft to make an approach to landing using the Instrument Landing System". This applies to making an approach to an aerodrome "... notified for the purpose of this sub-paragraph".

So which aerodromes do you think are "notified for the purpose of this sub-paragraph"? I can't find a single such notification in the AIP. It's unlikely to include airports outside controlled airspace. It would make it illegal for any aircraft to land at the airport without an ILS receiver, regardless of circumstances. I can imagine such a notification for Heathrow and perhaps Gatwick, but it's not going to go down well with the Tiger Moths at Cambridge, is it?

AN84 specifies non FM Immune instruments be limited to VFR only.

and goes on to say

"NOTE: For aircraft of 5700 kg MTWA or less, an acceptable means of compliance is to placard and restrict non-immune receivers to operations permitted under the Restricted Approval Category LA Class 3 (see paragraph 5.4), irrespective of the approval category for that equipment."

LA Class 3 receivers may be used for the facilitation of any flight (VFR or IFR) outside controlled airspace.

[BEagle]

Airworthiness Notice 84 states:


"5.2 Requirements for ILS localiser and VOR receivers effective from 1 January 2001:



(a) ILS localiser and VOR receivers, required to be carried.by UK registered aircraft for the purposes of operations under Instrument Flight Rules (IFR) in accordance with applicable airworthiness and operational regulations, must be of a type approved as complying with the improved FM broadcast immunity standard.



(b) Where non-immune ILS localiser and VOR receivers remain installed, (i.e. those carried in addition to the minimum number required by applicable airworthiness and operational regulations to meet IFR), they must be identified to the flight crew and their use restricted to Visual Flight Rule (VFR) operations.



NOTE: For aircraft of 5700 kg MTWA or less, an acceptable means of compliance is to placard and restrict non-immune receivers to operations permitted under the Restricted Approval Category LA Class 3 (see paragraph 5.4), irrespective of the approval category for that equipment.



5.3 Requirements for VHF communications receivers effective from 1 January 2001:



(a) VHF communications receivers, required to be carried by UK registered aircraft over 5700 kg MTWA for the purposes of operations under IFR in accordance with applicable airworthiness and operational regulations, must be of a type approved as complying with the improved FM broadcast immunity standard.



(b) Where non-immune VHF communications receivers remain installed in UK registered aircraft over 5700 kg MTWA, (i.e. those carried in addition to the minimum number required by applicable airworthiness and operational regulations to meet IFR), they must be identified so as to alert flight crews to the potential risk of interference.



(c) UK registered aircraft of 5700 kg MTWA or less may continue to be operated under IFR with non-immune VHF communications receivers provided that the receivers are identified so as to alert flight crews to the potential risk of interference.



NOTE: CAA will continue to monitor reports of interference and, if necessary in the light of experience, reconsider this relaxation from the ICAO standard for VHF communication receivers carried by aircraft of 5700kg MTWA or less."



Basically this means that if you're using a VOR or ILS
anywhere in the UK in a light ac, unless you're under VFR, you MUST have a FM-immune Nav receiver. However, your light aircraft Com transceiver doesn't need to be FM immune.

I went through this whole absurd nonsense a couple of years ago and it cost £17k to upgrade all my 4 ac to FM-immunity compliance requirements.....believe me, if it hadn't been essential I wouldn't have spent that amount of money unnecessarily!

[tmmorris]

BEagle-

There's a similar discussion going on in the Flyer forum at the moment. Someone referred to CAP472* as giving reassurance that for IFR outside CAS in aircraft under 5700kg MTWA, FM immune equipment is not required. There is some debate though over what Restricted LA Class 3 allows - the key word seems to be that Class 3 equipment can be used to 'facilitate' a flight, so I guess you could claim to be flying on dead reckoning in IMC with the 'help' of a VOR, there being no stated minimum equipment for IFR outside CAS.

*not available online, so I haven't been able to consult it!

If you look at the next paragraph on from your quote (referred to in the quote) it merely states that 'such equipment may not be used to comply with the requirement for the mandatory carriage of radio equipment' - i.e. outside CAS you don't <I>need</I> VOR/ILS (you could e.g. track NDB's) so don't need FM immune equipment.

Tim

[Justiciar]

So which aerodromes do you think are "notified for the purpose of this sub-paragraph"? I can't find a single such notification in the AIP

No, nor can I:confused:

I may have confused the situation here. There sems to be a difference between cases where there is a requirement to have a VOR/ILS fitted and the general position where if you use a VOR/ILS it must be FM immune.

Bookworm: I am afraid that "Restricted Approval Category LA Class 3" does not help as it simply clarifies the general requirement for FM immune kit by allowing you to placard non FM immune as "VFR only" rather than replacing it. It does not provide an exemption from the general requirement.

The whole thing is absurd, since you can legally be forced, if you stick to the letter of the law, to do NDB/DME approaches with all the imprecision that involves whilst you have what is in reality a perfectly good VOR/ILS on board. I know which one I'd use:ok:

[High Wing Drifter]

I would like to resurrect this thread as I am still quite confused as to what the requirement is:

In AN84, the "Note:" under 5.2 says that for A/C < 5.7t plcarded non FM Immune ILS/VOR receivers are permitted under Restricted Approval Category LA Class 3. What is this category and where can I find the correct supporting documentation? CAP208 has been withdrawn.

Help!
HWD.

[bookworm]

The wording in CAP 208 is (was) as I quoted above, HWD. They may be used for the facilitation of any flight, VFR or IFR, outside controlled airspace. Aerocoms have put the relevant section (http://www.aerocoms.com/CAP208.htm) on the WWW.

Note that I do not agree with Aerocom's interpretation of AWN84 on other pages.

[Final 3 Greens]

IO540
I have asked and asked and have never come across anyone who has ever heard of FM interference having actually happened.
I'm not an engineer, but I seem to recall that the issue was created by the desire of government to free up radio frequencies for commercial use.

It thus seems logical to conclude that even if there isn't any interference now, there may be in the future, if there is a take up of the extra capacity.

Unless one views this whole thing as a conspiracy to persuade people that private flying is too expensive to start/continue, then maybe the FM immunity issue is a future problem being dealt with now?