RVR Limiting Values

[Voodoo 3]

Quick question on RVR values if I may.

You are flying a CAT 1 approach with an RVR limit of 550 meters. If you are given touchdown, midpoint and end values from ATC, is the limit of 550m valid for all three sections or just the touchdown. Say you get given 600/400/600, would that prevent you making an approach?

Similarly flying CAT 3a with RVR required of 200m, if you get 300/300/100, would that too?

Thanks for your answers and if you have a reference in the manuals too that would be great!

[Torque2]

What is your take minima, ie are you able to operate to 125m or 150m, this will affect the precise answer.

550m indicates that the runway in use has lighting suitable for operation to at least Cat 2 LVP minima so the mid point would be whatever RVR you can takeoff at, the stopend the same OR if you have rollout guidance and you are able to reduce to taxi speed by then it becomes 50m when autoland is used at Cat 2 and below. As you can't officially use autoland at Cat 1 because no extra protections are in force then the 50m doesn't apply.

[Gin Jockey]

In practice I use the T/D and mid RVRs for a CAT 1 i.e. they both need to be above 550m, dunno what the "official answer" is.

As for not be able to do an autoland on a Cat 1 approach, that is balderdash, you can do an autoland to an approved runway if it is clear skies if you like, in fact it's often necessary for recency (crew and aircraft).

[Torque2]

I wish responders would read previous replies carefully. You CAN do an autoland but you can't do it for real, only in VMC for training. we're talking about having the necessary protections in place so that it shouldn't run of the edges. Balderdash? Bu!!£*"7 :ugh:

[Young Paul]

You CAN do an autoland (for real) but you CAN'T do it to Cat II/III minima without protection.

I think that's what you meant? :)

[MarkerInbound]

Probably depends on what country's rules you are operating under. Fairly standard US:

550 m is CAT I, only the touchdown is required and controlling
300 m is CAT II touchdown and rollout required with only TD controlling
175 m is CAT IIIa w/ TD, midfield and rollout required but only TD and Mid controlling
75 m is CAT IIIb, all three required and controlling

I've heard a few nights when crews try to get ATC to swap runways for iffy CAT Is. ATC will give a below min TD but the rollout is OK. The crew will ask to have the airport turned around so the higher RVR is the controlling one.

[Voodoo 3]

Young Paul,

I meant that you are flying in to a foggy airfield and you are CAT1 only. If you were given an RVR of say 600/500/600, would that prevent you making an approach under the approach ban rules since the midpoint is below your min of 550m?

Thanks for the answers peeps and the the PM's as well,

V3

and by the way it can be autoland or manually flown with a head up display even to CAT3a!!

[Torque2]

If you are referring to EU Ops then yes, 550m is the approach end, 125m or 150m is the mid point requirement depending on your Ops Spec, so you could land in those conditions.

[eckhard]

It does depend on your Ops Manual, but generically in EU-land:

For take-off:

Min/min/adv*

For landing:

Min/125**/adv*

*'adv' means 'advisory', in other words there is no minimum RVR required unless your performance requires the last 1/3rd of the runway. This is generally taken to mean that if your speed will be below 60kts on the last 1/3rd of the runway, it is deemed not to apply.

**125m for the mid-point or the same value as that required for the TDZ if that is less than 125m.

So, for Cat III approach with TDZ required of 75m, the RVRs would need to be 75/75/adv.

For a Cat I approach with a TDZ required of 550m, they would be 550/125/adv.

For take-off, depending on the lighting/markings available, you may need a TDZ RVR of (for example) 150m. Your minima would therefore be 150/150/adv.

[Sir George Cayley]

But what if one of the RVR sensors next to the runway is u/s?

And for take of what if one circuit of the runway centreline lights is out? Go or no go?

Sir George Cayley

[fujii]

CAT I TDZ only required for RVR 550m. Otherwise 800m if TDZ reading is not available.
CAT II and IIIa require both TDZ and MID or TDZ and END reading.
CAT IIIb requires all three readings.
All readings from electronic sensors. Ground staff assessment not permitted unless operating to CAT I 800m. Sensors only certified for fog and mist.