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denver69

Part 121 alternate requirements with Cat 3

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Just wondering with any real airline pilots out there that fly Cat 3 certified stuff. What are the minimum requirements at the destination before one must file an alternate. What are the minimum weather conditions required at that alternate. Tomorow I am flying from San Fransisco to Zurich and it looks like I will have to be shooting the Cat 2 there upon my arrival. I have spent much time looking for a suitable alternate and it looks like the whole of Europe seems to be plagued by radiation fog. I fly part 135 for real in a Cessna 421 an am of course a cat 1 airplane and pilot so I know your Opspec is probably totally different than mine in this regard.Thanks


Marc Lynn

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There is general information written in the regulations, and approach charts, but in the US every airline has an OpSpec. It's all the rules for that company, and it's approved by the FAA. The FAA will allow lower than general minimums in circumstances where a company has proven sufficient safety procautions. In other situations, the company is limited to higher than general mimimums. So the disclaimer is that every airline's operation is different. That being said, my airline is approved for CAT II ops. For our operations (and I believe this holds true pretty much across the board with US carriers), we are required to have an alternate (for domestic ops) if the landing airport's weather is forecasted to have visibility below 3 statue miles, and/or ceiling below 2000 ft AFE at anytime from 1 hour before to 1 after your proposed time of arrival. We have an exemption to allow us to ignore conditional statements in TAFs (such as TEMP, PROB30, PROB40, and "becoming"), but to use it we have to have 2 alternates, use special increased minimums for each of the alternate airports, and have enough fuel for flight from the destination to the farthest alternate. Our general alternate aiport weather requirements are dependent on whether there is only one navaid available for the forecasted direction of landing, or more than one operating navaid each providing a straight-in approach to different suitable runways. If there is only one navaid we have to have a forecasted ceiling at least 400 ft above the intended approach's MDA/DA and visibility at least 1 statue mile better than the approach's min vis. For alternates using the "two navaid" rule, a ceiling at least 200 ft above the higher of the two approaches' MDA/DA, and vis 1/2 statue mile above the higher of the two approaches min vis requirement must be forecasted at the time of arrival at the alternate.Clear as mud? There are many pages about this is our company manuals to explain these details and quite a few others. It can be very complicated, and that's why we have dispatchers. We are still responsibile for all of this, but it can become very time consuming. Our dispatchers get all of this pieced together for us, and then we double check it. I hope this helps some, but remember this is specific info for the company I fly for. It isn't intended to be used for any other operation (read that as: isn't legal for any other operation).


Charles Carter

 

i5 750 OC'd to 3.6GHz - 8 GB RAM - nVidia GTS 250

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You alternate stuff is almost exactly like mine for FAR 135. The FAA has fairly blanket Opspec issuance in this regard I guess. I am just wondering if Cat 3 may be more lenient if you are going to an airport with a cat 3 approach. But maybe not, especially if it only has 1 of them. It is interesting to note that we are not even aloud to use the more conservative numbers written for part 91 operators in the NOS. It would make sense that if you were planning on shooting a cat 3 you had better have a pretty bombproof alternate because that weather is REAL low.I am just trying to be realistic a possible going international to an area like Switzerland in the winter where the fog problem makes the Central Valley of California look like Margarita weather in the winter time. Last night's TAF's were socked in bad all the way to Paris as far as usable airports go for the MD11.


Marc Lynn

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You alternate stuff is almost exactly like mine for FAR 135. The FAA has fairly blanket Opspec issuance in this regard I guess. I am just wondering if Cat 3 may be more lenient if you are going to an airport with a cat 3 approach. But maybe not, especially if it only has 1 of them. It is interesting to note that we are not even aloud to use the more conservative numbers written for part 91 operators in the NOS. It would make sense that if you were planning on shooting a cat 3 you had better have a pretty bombproof alternate because that weather is REAL low.I am just trying to be realistic a possible going international to an area like Switzerland in the winter where the fog problem makes the Central Valley of California look like Margarita weather in the winter time. Last night's TAF's were socked in bad all the way to Paris as far as usable airports go for the MD11.
Ya my all over Europe the WX was bad, I was going from Gatewick to Zurich and the visibilty was very very bad all over the place. I did however manage to fly the ILS 34 at LSZH down to about 250' and I saw the runway. Seriosuly I've been for the past week EVERY flight I've done into EGKK has been an Autoland as ASE was giving me RVR's/Visibilty's of 175metere or less, at one time I had to wait to takeofff because EGKK's 08R has a T/O min of 75meters and the Visbility was 55meters. I really enjoy this kind of simming though. Make me appreciate RW pilots and there skills.

Ron Hamilton

 

"95% is half the truth, but most of it is lies, but if you read half of what is written, you'll be okay." __ Honey Boo Boo's Mom

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