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CATlllA&B Operations

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Spooky 1

Well-known member
Joined
Nov 28, 2004
Posts
987
For those of you who are CAT111A or B approved and in particular flying Boeing equipment, I need a quick survery as to where you are setting your RA bugs during this procedure so as to signal the Alert Height. The FAA's AC that deals with this subject is a little vauge and has a fairly large degree of latitude. It has always been my experience that 50' was where I set the bug per our Ops Specs and particular aircraft operational procedures but I am getting some unwanted feed back that this might not be the ideal setting. Obviously I don't agree, so I am looking for feed back that would either support my concepts or challenge them for validity. So in your ops is it 50' or what.

Thanks in advance........
 
Spooky 1 said:
For those of you who are CAT111A or B approved and in particular flying Boeing equipment, I need a quick survery as to where you are setting your RA bugs during this procedure so as to signal the Alert Height. The FAA's AC that deals with this subject is a little vauge and has a fairly large degree of latitude. It has always been my experience that 50' was where I set the bug per our Ops Specs and particular aircraft operational procedures but I am getting some unwanted feed back that this might not be the ideal setting. Obviously I don't agree, so I am looking for feed back that would either support my concepts or challenge them for validity. So in your ops is it 50' or what.

Thanks in advance........

Hey Spooky ... give 'em hell ... to answer your question:

100' Alert Height on the 757/767 @UPS per our Ops Specs


The primary justification for 100' is found in the AOM:

"Below 100' the approach, flare and rollout may be safely accomplished following any failure in the airplane or associated Cat III systems".

BBB
 
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In the airbus, for 3A we set 50' RA as a DH and lights must be in sight, for 3B we set 100' RA but ignore the "minimums" autocallout where many operators don't put anything at all to avoid the confusion of hearing "minimums" when in fact you don't need to have anything in sight. I guess each operator can tweak thier profiles if they want.
 
a319drvr said:
In the airbus, for 3A we set 50' RA as a DH and lights must be in sight, for 3B we set 100' RA but ignore the "minimums" autocallout where many operators don't put anything at all to avoid the confusion of hearing "minimums" when in fact you don't need to have anything in sight. I guess each operator can tweak thier profiles if they want.

Technically, UPS is similar to a319's procedure. In a 757/767 there are 2 options for flying a Cat IIIa approach:

CatIIIa (Land 2 Fail-Passive) conducted to a 50' DH (must have sufficient visual reference)

Cat IIIa (Land 3 Fail-Operational) conducted to a 100' Alert Height


On the Boeings the difference lies in what required redundant item failed. Must have triple redundancy normally. Gets complex, but thankfully the computers take care of all the "what-ifs" and illuminate the corresponding light bulb ... Land 2 or Land 3.

On a Cat IIIa (Land 3), "the reliability and performance is such that continued safe operation is assured following any system failure, not shown to be extremely improbable below 100 feet".

Basically on a Land 2, two like items (2 of 3 radar altimeters, for instance) failed and now the pilot has to see something to land (human must double check computer's flight performance) because Boeing no longer has blind confidence (if you will) in the system.

BBB
 
B-757 Ops:
Cat IIIA-Land 2: DH=Published Cat II RA minus 50'
Cat IIIA/B-Land 3: AH=Published Cat II RA, Ignore the "minimums call" from the GPWS
 
RampFreeze said:
B-757 Ops:
Cat IIIA-Land 2: DH=Published Cat II RA minus 50'
Cat IIIA/B-Land 3: AH=Published Cat II RA, Ignore the "minimums call" from the GPWS

Why are you getting a minimums call at something other than what you have set your RA bug at even though in this case it is an Alert call as opposed to a minimums?
 
Re: Cat 111

At US / Airbus we train to CAT 11, 111a, and 111b.

The primary difference, please I don't have my books in front of me so be gentle, is that CAT 11 DH is based on RA as published or if No RA authorized, then DH is the IM. We set the IM altitude as a reminder for a 100 above call that is required.

For CAT 111a or CAT111b we use 50ft and 100ft respectively. The difference is that for CAT111a we have a decision height, (DH). CAT111b uses an "alert height." The difference is, as our books tell us, is that AH is based on reported visibility being above required minimums and that at the minimums call out, at 100AH, the captain electronically verifys that the aircraft is aligned for a normal landing in the touchdown zone. On the Airbus this means the needles are centered and there are no warnings, and CAT111 dual, (fail active configuration) is annunciated on the PFD.

We in fact do not have to see the runway to land CAT111b. We electronically verify the landing envirnment and allow the autopilot to land the aircraft. Like wise if there is an incapacitation issue or the captain fails to respond to callouts the recomendation (US) is to continue and allow the autopilot to land the aircraft. This is different from the procedure on our older 737 CAT111a procedure where to F/O does the go-around or on the MD-80 CAT111a, again F/O takes the AC and does go around.

I hope I throughly muddied up the water and raised your knowledge to a much higher level of confusion.
 
Easy with me as well as I have no books in front of me.

For CAL, Beer Belly and Groucho are spot on. Although I think Belly had a typo with 3B being an alert height as he mentioned 3A twice.
 
Spooky 1 said:
Why are you getting a minimums call at something other than what you have set your RA bug at even though in this case it is an Alert call as opposed to a minimums?

To clarify, what I meant by ignoring the "Minimums" call from the GPWS is simply that it is an "alert height" and not really a "minimum" altitude to be treated as such. The "Minimums" call is, in fact, going to be heard at whatever height the RA bug is set at. It will be heard at either the DH or AH as appropriate. So, on a Cat IIIA/B-Land 3, with a 100' Alert Height (AH), you ignore the minimums call (since there are no minimums on this approach with an Alert Height vs. the RA Decision Height on a Cat II or Cat IIIA-Land 2 which does have "minimums" of ~50' AGL) We set the Cat II RA DH (~100') for a Cat IIIA/B-Land 3 (and get the "minimums" GPWS call) for a couple of reasons. 1) it is an advisory of reaching the alert height 2) in case of a malfunction restricting us to a Cat II approach, the bugs are already set. (We can hand-fly a Cat II as necessary and if you do end up hand-flying all of a sudden, the last thing you want to be doing is dialing the bug) If we revert from a Land 3 condition to a Land 2 condition, you just dial down the bug 50' and press. Clear as mud?
 
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RampFreeze said:
To clarify, the "Minimums" call from the GPWS is simply going to be heard at whatever height the RA bug is set at. It will be heard at either the DH or AH as appropriate. So, on a Cat IIIA/B-Land 3, with a 100' Alert Height (AH), you ignore the minimums call (since there are no minimums on this approach with an Alert Height vs. the RA Decision Height on a Cat II or Cat IIIA-Land 2 which does have "minimums" of ~50' AGL) We set the Cat II RA DH (~100') for a Cat IIIA/B-Land 3 (and get the "minimums" GPWS call) for a couple of reasons. 1) it is an advisory of reaching the alert height 2) in case of a malfunction restricting us to a Cat II approach, the bugs are already set. (We can hand-fly a Cat II as necessary and if you do end up hand-flying all of a sudden, the last thing you want to be doing is dialing the bug) If we revert from a Land 3 condition to a Land 2 condition, you just dial down the bug 50' and press. Clear as mud?

Gottcha. Just hace a hard time ignoring any minimums callouts and continuing on futher down to a lower altitude. Thanks!
 
Boeingman said:
Easy with me as well as I have no books in front of me.

For CAL, Beer Belly and Groucho are spot on. Although I think Belly had a typo with 3B being an alert height as he mentioned 3A twice.

Okay Boeingman. I think I know where you work, so is it your company policy to use 50' for both CATlllb and a? I am assuming that you are not flying the -800 with the HUD installed?
 
Boeingman said:
Easy with me as well as I have no books in front of me.

For CAL, Beer Belly and Groucho are spot on. Although I think Belly had a typo with 3B being an alert height as he mentioned 3A twice.

Checked it again ... no typo. To further clarify though, at UPS your approach choices are:

Cat I

Cat II to a DH of 100' (min)

Cat IIIa (Land 2) to a DH of 50'

Cat IIIa (Land 3) to a AH of 100'

Cat IIIb to a AH of 100'


RVR and equipment malfunctions will obviously dictate approach choice. Cat IIIb are flown to 300 RVR (where published) with no requirement to see anything prior to touchdown.

BBB
 

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