View Full Version : USA Minimums

767 pilot
15th Aug 2018, 15:29
Hello, everybody!
I din not find CAT III ILS differentiation (to CAT IIIA and CAT IIIB) on USA approach chart. For instance: BOSTON, ILS RW 33L CAT II and III, CAT III - RVR is 600ft, so it is not clear if this is CAT IIIA or CAT IIIB ILS APP and which type of landing system this approach requires FO or FP. Thanks.

Yancey Slide
15th Aug 2018, 18:45
Ref FAA AIM page 1-1-12, CAT IIIa/b/c would be defined by the DH/RVR. Looks like it's a CAT2 (RVR1200, RVR1000 with special auth and use of autoland/HUD to touchdown) and CAT IIIb (RVR less than 700 but not less than 150).

Cant' speak to FO or FP. Isn't that aircraft specific though, what it's limited to for CAT3B ops?

I stand to be corrected though.

16th Aug 2018, 00:02
Lido chart says Cat3b RVR 600ft. Doesn’t mention Cat3a. Cat2 RVR is 1000ft, (1200ft without equipment described above).

767 pilot
16th Aug 2018, 07:19
Thank U for your help, especially for the reference to the FAA Doc.

16th Aug 2018, 22:49
A CAT III operation is a precision approach at lower than CAT II minima.

A category III A approach is a precision instrument approach and landing with no decision height or a decision height lower than 100ft (30m) and a runway visual range not less than 700ft (200m).
A category III B approach is a precision approach and landing with no decision height or a decision height lower than 50ft (15m) and a runway visual range less than 700ft (200m), but not less than 150ft (50m).
A category III C approach is a precision approach and landing with no decision height and no runway visual range limitation.


17th Aug 2018, 01:58
Look at it as the higher of the published minimums or what your airline/aircraft is authorized to land with. My current equipment (744/8, three autopilots) considers CAT II as fail passive and CAT III as fail operational. We are approved down to a DH of 100 feet and 1000 RVR for a CAT II and an Alert height of 100 feet and 300 RVR for CAT III. So we would fall under the CAT II SA 1000 RVR. Since that approach requires 600 RVR for CAT III that would limit us even though our OpSpecs says we can land with 300 RVR CAT III.

23rd Aug 2018, 01:16
The United States does not certify runways or approach systems to CAT IIIA or IIIB anymore. All CAT III runways are certified to fail operational capabilities, unless there is a problem with rollout guidance. Only a very few runways here have the transmissometers necessary to allow operations below RVR 600 feet, hence you'll see that as the published minimum in most cases. As Marker Inbound says, you must use the higher of either the runway minimums or your company minimums. The latter should reflect your aircraft capabilities, i.e., fail-passive or fail-operational.

There is still some misleading guidance floating around about fail-passive systems being limited to CAT IIIA. In fact, they have been limited to RVR 600 for several years now, which is less than CAT IIIA minimums. However, again, your company minimums must again be respected if they are greater than the published minimums. Keep an eye out for little notes on the chart that say things like "Localizer unusable for rollout". That can make a rather big difference!

3rd Sep 2023, 08:43
Can someone tell me what is the Minimum DH to be used on RWY 22L cat3B (Fail/Op) at KJFK ?
LIDO says 50/600 and company.
With my aircraft I can do 20/125m so it's company.
Am I allowed to use my company DH (20ft) ?