CAT II, without CAT I reversion question?

[FourTrails]

A question for CAT II operators. Having just returned from simulator I must admit to having a little difficulty with the following practise.

Situation: Following appropriate RVR check, ie. 300/300/100, the statement is made at 4nm that the approach will be "CAT II with NO reversion"

I am told, and indeed it is written into our manual that following a CAT II failure above 500(R) for example due Loc deviation or Autopilot failure, the approach may be continued to CAT I minima.

In the past, I had been instructed that a CAT II failure where there was no reversion to CAT I due RVR's meant a GA was flown, hence the 4nm statement "CAT II, NO reverion"

Would welcome comments from other CAT II operators.

[static]

Who made the statement?

[whoop-whoop]

(JAR-OPS 1.430)

Autopilot failure with an RVR less than 300m

1) Above DH: A go-around must be carried out.

2) Below DH: A go-around should be carried out. However, circumstances might dictated that landing is the safest action. i.e point at which failure occurs, visual reference or other malfunctions.

For the following I don't have JAR references, but I have taken extracts from company ops manuals.

ILS Deviation

Persistent deviation above 200RA, or any deviation below 200RA, the approach will be abandoned, unless the flight path of the A/C can be confirmed to be be satisfactory by visual reference.

[Bally Heck]

I believe that after passing 1000ft agl, it is quite in order to continue down to Cat 1 minima for a looky see. The approach ban applies only before this point.

[BLACK_BUSH]

That would be my understanding as well Bally Heck.
After passing 1000ft all RVR information is advisory only and you are quite legally permitted to descend to the minima set.
Our fleet Lo Vis procedures make provision for reversion toCATI"if the relevantCATIminima has been set on servo altimeters,andCATIprocedures have been discussed in the pre-descent briefing".
All companies have provision for ground/airborne equipment failures above and below 1000ft in their CATII/III procedures and most have the caveat "At the Captain's discretion an approach may be continued".
FWIW in my humble opinion,if any doubt exists about the safe conclusion of any approach,a Go-Around and reasessment would be the better option. :cool:

[EPRman]

Regarding the approach ban the 1000'a.a.l only applies if no OM or equivalent position exists,the equivalent position being a DME distance, NDB or VOR, PAR or any other suitable fix that independantly establishes the position of the aeroplane.

[tired]

The approach ban applies to RVRs, not aircraft malfunctions. And, as stated above, it's actually the outer marker - 1000'AGL only applies if there's no marker or equivalent position. (In UK Air Law, anyway - I think it's different in some other countries.)

My airline's SOPs say that, unless you're visual, there should be a go-around for any malfunction below 1000' other than a land ASAP emergency. Has always seemed sensible to me - do you really want to be sorting things out at 500/600 feet?


(Edited because EPRman beat me to it about the OM position!)

[ 06 December 2001: Message edited by: tired ]

[alosaurus]

As WW said you can have a loc deviation 500-200 RA BUT it must be correcting(just another way of saying you can't have a permanent deviation).

It was JAR ops that last year introduced "equivalent point" ahead of 1000'

[Offset]

Autopilot disconnect with RVR < 300m
This applies to fail passive autolands only and is covered in detail in IEM to App 1 to Jar Ops 1.430. The assumption is that a go around will be made if this occurs below DH, with the proviso that a landing may be made if this is felt the safer course. Most modern stuff is fail operational, only degrading to fail passive, and therefore we would be looking at a multiple failure for this restriction to become a factor.(eg for 757/767, LAND3 = fail operational, LAND2 = fail passive)

Downgrade on Approach
The rule is that an approach can be continued if the RVR falls below minima after the OM or equivalent (JAR OPS 1.405). This is not the same thing as and aircraft downgrade. The rule was written to cater for normal variations in visibility over time - ie it doesn't work the other way around! If you did not have reversion RVR at the OM then you must fly a go-around.

[ 09 December 2001: Message edited by: Offset ]

[CaptA320]

Must agree with Offset, the rule caters for RVR changes past 1000 or equivalent point, not aircraft system degredations. If this was the case why brief for reversion capability if we can continue in all cases to CAT I minima?

[FourTrails]

Thankyou chaps for your input. The above reflect my thoughts entirely. I shall now put it in writing to my fleet office and await their response.

[Sick]

My understanding has always been what yours is 4 trails, and what you were told; ie a cat 2 appr has cat 1 reversion when the rvrs are equal or greater than the cat1 minimum rvr, and if rvr is less than this it's a "cat 2, no reversion", (ie dont revert to cat1 minimums if eg you get YD failure, one side nav fail, persistent gs/loc dev). I dont see the relevance of the other stuff except that the beacon/1000' is the point before which you must receive the deciding rvr.