Hello,

i was wondering, when there's a low visibility procedures, how does the pilot knows when it's category II? i know that cat III is usually 100 and less, but i don't think they should know it in verbal.

so, if someone can explain it batter for me it'll be nice. thanks, cheers.

LVPs don't mean a certain category is in use, it simply means low visibility procedures are in use. This includes (but not limited to) ATC holding aircraft on the ground at the CATII/III holds to protect the ILS (if present, LVPs can be used at airfields that don't have CATII/III ILS), requiring aircraft to report vacated after landing, increased separation on approach etc.

 

As for which approach CAT gets used, it's complicated, so hopefully I've got the the following info correct:

 

If visual conditions are expected, CATI minima are likely to be used, because aircraft on the ground won't be holding at the CATII/III holds, meaning the ILS isn't protected; this is regardless of the capability of the aircraft.

 

If LVPs are in force, the pilots will want to land to the least restricted minima they can; obviously with CATIII being the least restrictive, CATI being the most restrictive. To carry out a CATII/III landing, the aircraft, ILS and pilots must all be certified to those limits. All three must be CATIII to allow a CATIII landing; if any are only CATII certified, that is the minima that must be used. If any are only CATI the same applies and only CATI can be used.

 

Also worth remembering that RVR (runway visual range) comes into play as well as decision height when dealing with a CATII/II landing.

 

I think the above is correct, I'm sure someone will correct me if I'm wrong.

Some more info....

 

He knows by the RVR in the ATIS.

 

With the runway visibility less than 1200 RVR, you'll need to have and use a CAT III Operations Specification authorization. Also, special aircraft equipment and pilot training is required for CAT II and III operations.

 

To sum it up in a nutshell, the lowest authorized ILS minimums, with all required ground and airborne systems components operative, are:

• CAT I - Decision Height (DH) 200 feet and runway Visual Range (RVR) 2,400 feet (if authorized and with touchdown zone and centerline lighting, RVR 1800 feet)
  
• CAT II - Decision DH 100 feet and RVR 1,200 feet
  
• CAT IIIa - No DH or DH below 100 feet and RVR not less than 700 feet
  
• CAT IIIb - No DH or DH below 50 feet and RVR less than 700 feet but not less than 150 feet
  
• CAT IIIc - No DH and no RVR limitation
  

 

vololiberista

terrible accent (although beeing a German by myself)

but his RVR minimum was 200 which doesn't fit into one of the official limits. Are there different limits possible for example company regulations or regional restrictions?

Another thing but off topic... the flaps ind the vid deployed a lot faster than in the PMDG.

 

Regards

Hirschi

terrible accent (although beeing a German by myself)

but his RVR minimum was 200 which doesn't fit into one of the official limits. Are there different limits possible for example company regulations or regional restrictions?

Another thing but off topic... the flaps ind the vid deployed a lot faster than in the PMDG.

 

Regards

Hirschi

 

Yes, airlines can have company specific minimums that are different from what is officially charted. They can even have their own customized charts, like e. g. Lufthansa. However, company minimums can never be lower than the official ones that were established for an airport's runway by the respective aviation authorities.

Yes, airlines can have company specific minimums that are different from what is officially charted. They can even have their own customized charts, like e. g. Lufthansa. However, company minimums can never be lower than the official ones that were established for an airport's runway by the respective aviation authorities.

Thank you, Dave.

but his RVR minimum was 200 which doesn't fit into one of the official limits.

 

 

Hi Hirschi,

RVR was within CATIIIb requirements (200 meters RVR/700 feet RVR) when he started the approach. He eventually had to miss the approach because reported RVR minimums went to 100-175 meters. In the US, but I'm not sure about anywhere else, you may continue the approach and take a look if you have passed the FAF for the ILS approach. You may not begin a ILS if RVR or visibility is below minimums and you have not passed the ILS final approach fix.

 

 

Hi Hirschi,

RVR is within CATIIIb requirements. RVR is 200 meters. 200 metere = 700 feet. CAT IIIb - No DH or DH below 50 feet and RVR less than 700 feet but not less than 150 feet.

geez, totally overheard the meters. Thanks a lot. That must not happen.

 

Regards

Hirschi

Yes, airlines can have company specific minimums that are different from what is officially charted. They can even have their own customized charts, like e. g. Lufthansa. However, company minimums can never be lower than the official ones that were established for an airport's runway by the respective aviation authorities.

 

http://www.planningcharts.de/

thanks guys!

Yeah, LVP in and of itself relates more to ground procedures than anything. The rest is just differences in minima for approaches, and that doesn't necessarily get lumped in with LVP. It obviously coincides, but they aren't necessarily dependent. IAD, as an example, has ASDE-X, so tower can still control based on known positions without being able to see the aircraft, and not requiring LVPs that involve the flight crews.

 

As far as the approach goes:

ATC solicits the most ideal approach option for them (which is normally the best option for the pilots as well). If the ceiling is more than 500' above the MVA (minimum vectoring altitude - a pilot has no way to know this number as it is not published) then visual approaches are likely to be run all the way until that point. Why run visuals so low? Running the ILS cuts the airport throughput significantly because of the amount of spacing that needs to take place, in addition to the controller workload. At IAD, as an example, they can push about 100 aircraft through in VMC. In low VMC (basically, ceilings getting close to that 500' limit), they can push about 90. Once that goes to IMC, that drops to 72. If it's low IMC (CAT-II/III), it drops further to 68 (a lot lower if you're CAT-III).

 

Lower throughput means more holding, in the end, so even though it's harder to call the field later because you bust out of the clouds later, you get the benefit of not having to hold while tons of aircraft fly in on the ILS.

 

So, how would the pilot know? This:

"United 946, Potomac Approach. Descend via the SHNON2 arrival. Expect ILS Runway 1R." (note, there's no mention of CAT-II or -III)

From there, as mentioned by the others, it just involves putting things together. Are the mins okay for CAT-I? Nope. CAT-II? Yes. Are we, and the aircraft certed and current for CAT-II? Yes. We'll fly the mins on that approach. Done. It's up to the crew to determine the current category required through listening to the ATIS, and if they can fly the various CATs.

 

If they can't, they advise ATC that they are unable to fly the ILS approach, and provide intentions (we'll hold, we'll divert, etc).

 

The numbers listed above are from the FAA OIS advisory throughput numbers (AAR or "airport arrival rate"). You can find them here. Click on East or West Directory, then click on the ARTCC (Air Route Traffic Control Center) where the airport resides, and then on the airport.

On top of all this, it's good to note that I don't believe CATIIIc mins are used for any commercial flights...anywhere. It's autoland only, and since It's still a fledgling system the only times it's used are for experimental autolands. Someone correct me if I'm wrong.

Hi.

Where I work we have one RWY but with a CAT II category ILS installed from one direction. It's a regoional airport so we don't have that much traffic.

If we are going to put LVP in force (no fancy ground radar, procedure separation on the ground i.e. one movement on the ground at a time) we need to make certain preparations before activating LVP. Such as road blocks on access roads for vehicles, confirming ILS sensitive area is free of any obstacles and deemed OK for CAT II and also running our backup generators in active mode instead of the normal stand-by mode and some more items. All preparations take 30 minutes.

There after we can use CAT II. However if we don't clear an aircraft for CAT II-approach they will have the normal minima for CAT I. But pilots usually request CAT II right after we give them the MET REPORT, given they are capable. Oh, we don't have ATIS either. :smile:

It also feels a bit awkward during real bad weather when you don't see ######, barely the ground from the tower. Seeing the echo on the radar gets closer and closer to the runway and then disappears. 10 seconds later you hear them kick in the reverse. Those 10 seconds can be looong. :smile:

On the other hand pilots can request to do an CAT II-approach for practice even though the weather is good. If so we need to make sure the ILS-sensitive area is clear as well as running the backup generators. It's an impressive sight to see a go around at 100 ft.

For LVP our requirements are to prepare for LVP when RVR is 750 meters or cloud base/vertical visibility is 300ft. And LVP must be in force at RVR 550 meters or cloud base/vertical visibility 200ft.

 

A funny thing is that I've had an aircraft (B200) do a visual approach when LVP was in force and I couldn't see out of my windows because of the fog. Now how could he do that? :wink:

Hey,

whats LVP? thanks.