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121 Takeoff Minimums and Takeoff Alternate Questions

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121 Takeoff Minimums and Takeoff Alternate Questions

Old 03-21-2008, 04:59 PM
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Default 121 Takeoff Minimums and Takeoff Alternate Questions

Takeoff Minimums & To Alternate Minimums.

I am interviewing soon (9E/XJ) and need to seek some clarification on takeoff & Alternate minumums.
I am a former 135 freight dog (20 years ago getting back on board) and understood the regs then but
would like to clarify for 121 interview purposes.

Minumum visibility standards for taking off:
Of the three standards possible for taking off
#1.) back of the Jepp Plate 10-9 visibility for takeoff
#2.) (Standard takeoff minimums) of 1 / 2 eng (1 mi or 5000 rvr) and 3/4 eng mins (1/2 mi or 2400 rvr)
#3.) Company ops specs that lets say is lower than the Jepp 10-9 vis. @ 6/6/6 Rvr

A.) Do you jump to the HIGHEST visibility of #1 or #3? or the LOWEST? Does the plate rule?
B.) If you have only #1 and it is HIGHER than #2 which do you use? (plate I would think)

While we are here. Takeoff ALTERNATE. Different question entirely.
Q-Let's say it is determined that a takeoff ALTERNATE is needed (vis less than lowest landing minimum)
What weather do I need to see at that ALTERNATE airport? 600/2 for ILS airport or 800/2 for non-precision landing?
Can ALTERNATE airport Ops specs override (lower) these standard alternate minimums?
One poster said that the weather needed at the alternate need only be greater than the lowest landing minimum throwing
out the old 600/2,800/2 rules but that does not sound like and adequate safety margin.

And one bonus question. Do all alternate airports whether takeoff alternate or destination alternate have the same
600/2 and 800/2 basic weather specification as a theme?
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Old 03-22-2008, 09:56 AM
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121 T/O Mins: These are specified in your OPSPECS and can vary between airlines. Typically it goes like this:

1. If the 10-9 does NOT publish higher-than-standard, you can always use standard.
2. If you can use standard, then your OPSPEC will typically allow you to use your lower-than-standard (5-5-5, 6-6-6, or whatever your airline has).
3. If the 10-9 publishes HIGHER than standard, then you are limited to the 10-9, you cannot use OPSPEC lower-than-standard.

Basically, if standard is published or implied, you can use OPSPEC mins. If higher-than-standard is published, you must use the published mins.

Note: If the 10-9 publishes different values for different climb gradients, you will base your determination on the mins which apply to your climb gradient.

ALT Mins: These are normally calculated based on an OPSPEC formula using the CIG and VIS mins for the approaches to the ALT airport. Too complicated to discuss here, but OPSPEC will overide the standard 600-2/800-2. The formula will produce mins higher than basic approach mins.

The 10-9 ALT mins don't count for 121, except if the IAP says "N/A" under alternate mins for your category, you cannot use that airport as an ALT.

At the airlines I have been at, ALT min calculations worked the same for both T/O and DEST alternates.
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Old 03-22-2008, 09:16 PM
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121.617b says the takeoff alternate has to meet the alternate minimuns in the Ops Specs. Paragraph C55 is the create your own minimuns paragraph based on the available approaches. Pretty much for one approach add 400 and 1 to the mins and for 2 approaches, 200 and a half to the higher minimuns. The approaches have to be to different runways unless you're ETOPS, then they have to be to separate runways. If you're good for CAT III and the airport has dual CAT III runways you can get your alternate minimuns down to 200/1800RVR. If it was down to that, I'd see about having a second alternate added to the release.
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