Mode C vs. RVSM status

[Jagohu]

Hi all,

I'm just wondering how is it treated at other ATC units if an a/c loses it's mode C - is it still considered as RVSM or not?
Strictly speaking it is not, but on the other hand it does not lose the altitude keeping ability, it's only an indication... How's it at you and what do you think?
cheers,
Jago

[YourFriendlyATCO!]

Hey!

As far as i'm aware, if an aircraft loses it's Mode-C, we treat it as negative RVSM. Could be wrong though... usually am!

[PPRuNe Radar]

The European airspace documentation can be found here:

ECAC RVSM Library (http://www.ecacnav.com/content.asp?CatID=30)

In particular the MEL is included in TGL6 and the Flight Crew information pack.

The MEL is:

AIRCRAFT EQUIPMENT

The minimum equipment list (MEL) fulfilling the MASPS consists of : (see JAA TGL6)

1.Two independent altitude measurement systems each equipped with:

cross-coupled static/source system with ice protection if located in areas subject to ice accretion,

display of the computed pressure altitude to the flight crew,

digital encoding of the displayed altitude

signals referenced to a pilot selected altitude for automatic altitude control and alerting,

Static source error correction.

2.One SSR transponder with an altitude reporting system in use for altitude keeping.

3. An altitude alerting system.

4. An automatic altitude control system.

Unfortunately the ATC Manual is not available on the site as it is undergoing a rewrite - so can't see what official guidance is given if a transponder fails. :ugh:

[eighteennine]

Hi Vik,

good to see that you haven't lost your habit of asking tricky questions as you did in ABI39 :ok:

greetings from ELLX

PM

[Blockla]

From the Australian AIP...

Failure of the Mode C-capable SSR Transponder. If the mode C-capable transponder fails, the pilot must notify ATC of the failure using the phraseology “NEGATIVE RVSM” (see GEN 3.4 Subsection 5.5 Item 2.p.)

[bekolblockage]

The significance of no Mode C precluding RVSM is not really related to the inability of ATC to see the aircraft's altitude on the radar - there is plenty of RVSM airspace outside radar coverage - but more to do with the ability to comply with TCAS II requirements which would require altitude encoding for resolution advisory.

[Spitoon]

There is a very vague answer in the Air Traffic Controllers FAQs (http://www.ecacnav.com/content.asp?PageID=76#Q5) - doesn't really say yes or no!Typical Eurocontrol/JAA wording!!! Of course you can allow a non-RVSM aircraft into RVSM airspace - it's just that you might want to use 5000ft vertical separation....

Wouldn't it be nice if one day the people who write the rules took the trouble to make sure that they dotted the Is and crossed the Ts. But to do that I suppose you would need to work out all the answers before you dump it on the controllers.

On the original question, although I don't do RVSM, it seems clear to me that no mode C = negative RVSM.

[Jagohu]

Typical Eurocontrol/JAA wording!!! Of course you can allow a non-RVSM aircraft into RVSM airspace - it's just that you might want to use 5000ft vertical separation....

Well, they're only talking about the ICAO RVSM requirements (general I guess) and for Europe there's the D7030 for example, which clearly states that in case if an aircraft is non-RVSM and not state approved it cannot enter to the RVSM airspace.

[Lon More]

Jagohu, ask your TO. It'll give him/her something to look up.
From memory; the requirements for RVSM are no longer met, so climb above/descend below RVSM airspace.