Another question i cant decode via wiki.

 

If the ATC for a given approach requires CATIIIB and the ILS Chart say CATIIIB avaible. What is the DH? Maybe the METAR says 100m RVR. How do i count those 100m and what has first priority during the FA? DH or RVR.

 

How do i know what to set the Radio altimeter to?

 

Thanks

 

Michael

CATIII approaches do not have decision heights. As far as I know they are autolands and CATIIIC do not have minimums associated with them.

RVR and DH are two different things. For simulation purposes, if published RVR conditions exist, you can fly with published DH minimums.

Cat III approaches do not have decision heights--they are intended for a fully automatic landing where the pilot may not even see the runway environment before touchdown.  Cat IIIA and IIIB will have visibility minimums, and Cat IIIC is legal down to zero-zero, so no published mins there.  Which one you can fly will depend on the aircraft (certification and operating equipment vs MEL requirements) and the crew's certification level (driven by training and experience level).

 

Regards

Well you are all wrong. Only fail operationel does not have DH and RVR on a autoland CATIII A or B. Ralph has a very good video training on that. Thats called alertheight btw. But how do i measure RVR from the cockpit?

And what about the DH determination? From a fail passive point of view. Typically this would be in between 0-50 feet but who is calling 37 for instance?

 

Michael

If you know better why have you asked...

 

 

Well you are all wrong.

My My, I'm willing to bet you'll get a LOT more helpful responses in the future.

 

In any case, you happen to be wrong yourself. Alert Height and Decision Height are not the same thing.

What do you mean "how do you measure RVR from the cockpit"? 

 

RVR is runway visual range and it is given in the METAR. You don't measure this with a "broom stick" from the cockpit.

 

ILS Cat 3b -fail operational: DH 0ft 

ILS Cat 3b - fail passive:  DH 50ft 

Well you are all wrong. Only fail operationel does not have DH and RVR on a autoland CATIII A or B. Ralph has a very good video training on that. Thats called alertheight btw. But how do i measure RVR from the cockpit?

And what about the DH determination? From a fail passive point of view. Typically this would be in between 0-50 feet but who is calling 37 for instance?

 

Michael

 

Well, no we're not all wrong.  There's a difference between minima imposed by the procedure itself, and restrictions imposed by company policy or the AOM.  Fail passive ops restrictions, in particular, are limitations imposed by policy or AOM due to partially inoperative equipment, not by the IAP itself.  Many operators also have more restrictive standing operational limits of their own, some for all crews, some for certain aircraft, and some based on the experience level of the crew.

 

DH and AH are not even close to the same thing, either.  The AH is used to make a final evaluation of system status for a decision on continuing the Cat III approach and autoland.  The DH is the latest point where a land/no-land decision is made based on visual contact with the runway.

 

RVR is measured by light transmissometer readings made by instruments located near the approach end of the landing runway, and is reported by ATIS and/or ATC.

 

Regards

Guys sorry if the words was wrong choosen. I did not try to be a beast :-) i know DH and AH is different. I was just under the impression that the pilot has to make visual reference on fail passive and since the DH is 0-50 feet i am just lost. I thought you would or should count the lights or sonething. And secondly. Why would i choose a DH37 aand not just 0 or 50?

 

No hard feelings my fellow sinmers:-)

Concerning fail-passive systems the decision height is 50 ft. 

 

FAA:

(AC 120-28D)

"Category IIIb operations based on fail passive landing systems meeting provisions of Appendix 3 of this

AC, or equivalent, must use a decision height not less than 50 ft. HAT." 

 

EU:

(CS-AWO 304)

"For decision heights below 15 m (50 ft), 

a fail-operational landing system (automatic or 

hybrid) must be provided which, when 

appropriate, includes provision for control of the 

aeroplane along the runway during the ground 

roll down to a safe speed for taxying. "

 

 

Guys sorry if the words was wrong choosen. I did not try to be a beast :-)

 

Try a bit harder, it will do you well.

 

 

 

I was just under the impression that the pilot has to make visual reference on fail passive and since the DH is 0-50 feet i am just lost. I thought you would or should count the lights or sonething.

 

Yes he has. There are guidelines of what you have to see. For example a regulatory document (manual, FAR etc.) could say that you need to see three bars of the approach light system.

 

 

 

And secondly. Why would i choose a DH37 aand not just 0 or 50?

 

Na-ah. YOU don't choose nothing. You do what you are told - these values are chosen by someone for reasons. If they come to a value of 37, it has probably something to do with runway shape/slope, obstacles etc.

 

Also noted fail-passive is not (generally speaking) CAT IIIb level, rather CAT IIIa level (barring exceptions, such as noted in Daniels post, outlined in Appendix 3 of the relevant document)

Thanks but if i am not choosing the DH will it be reported by ATC then?

 

Those lights i might count would be a control of the equipment for RVR i guess. If the RVR changes midway a Weather update?

 

Thanks Michael

DH is not reported by ATC, it is published on the chart for the approach in question...

Also, any significant RVR change during the approach is reported by ATC (in the realworld) until the aircraft has landed.