123 Rule with a Tempo Condition

nippy31 · March 16th, 2008, 01:50

Hey all,
I was wondering if any of you could direct me to a resource regarding this question. If you are required to file an alternate and by using the 123 rule your ETA is during a tempo condition that is below alternate minimums, are you allowed to use it as an alternate?

My personal thoughts were no. A co-worker disagreed. SO tonight I went nuts looking through the FAR's, and my various instrument publications. I could not find anything.

What I'd like to know is A TEMPO of PROB restrictive for an alternate.

Thanks

Minuteman · March 16th, 2008, 02:19

91.169 (c) says:

Quote:

... no person may include an alternate airport in an IFR flight plan unless appropriate weather reports or weather forecasts, or a combination of them, indicate that, at the estimated time of arrival at the alternate airport, the ceiling and visibility at that airport will be at or above the [required minimia for various situations]

and NOAA says:

Quote:

The TEMPO group is used for any conditions in wind, visibility, weather, or sky condition which are expected to last for generally less than an hour at a time (occasional), and are expected to occur during less than half the time period. The TEMPO indicator is followed by a four-digit group giving the beginning hour and ending hour of the time period during which the temporary conditions are expected. Only the changing forecast meteorological conditions are included in TEMPO groups. The omitted conditions are carried over from the previous time group.

So I think you're OK to an file an alternate with a TEMPO as long as at least the required minimums are forcast for the time of arrival.

minitour · March 16th, 2008, 04:30

Are you asking about the following scenario?

Departure: ABC

Arrival: DEF
ETA: 0100Z

TAF for DEF from 0000 to 0200 calls for 003OVC 1/2SM

Alternate: XYZ

ETA at XYZ: 0200Z

TAF for XYZ calls for:
0000 020OVC P6
TEMPO 0103 003OVC 2SM
0500 CLR P6

I'm going to say "no, that's not a legal alternate....for part 91". As always, check your op specs for air carrier stuff as that may differ.

If that's not the scenario you're asking about, then I have no idea what you're asking about.

-mini

nippy31 · March 16th, 2008, 10:30

Mini,
thats exactly what I am asking. Is it written anywhere though in the publications specifically that a TEMPO condition is restrictive?

dc3flyer · March 16th, 2008, 10:44

I don't know if it is "written" anywhere, but it only makes sense that you shouldn't use it. What if the TEMPO is happening when you get there?

BobDDuck · March 16th, 2008, 11:58

Unless you have an exemption to the FARs a below mins TEMPO is controlling. That's where the dreaded 3585 comes into 121 (and maybe 135) flying.

aloft · March 16th, 2008, 15:13

"The dreaded 3585"? You gonna leave us hangin' like that, or are you gonna finish your answer and explain what the hell a "dreaded 3585" is???? Sheesh!

Clocks · March 16th, 2008, 15:37

Every time I try to explain 3585 I confuse myself.

To paraphrase my FOM...

3585 allows operation when a forcast's conditional remarks are below dispatch minimums, the main body of forcast must still be above dispatch minimums.

So you can still be dispatched to a destination which has "BCMG, TEMPO" etc below the normal minimums as long as those conditional remarks don't put the weather lower than 1/2 the lowest visibility value.

Your first alternate's conditional statements can't put the weather below 1/2 the visibility AND 1/2 the ceiling minimums.

A second alternate is required and must meet the normal alternate minimums.

majorityof1 · March 16th, 2008, 16:07

I have a 3585 quick referance card if anyone wants a copy emailed to them. It can be confusing, but the card walks you through the conditional statements and when it would be beneficial to use it.

BobDDuck · March 16th, 2008, 16:21

3585 used to scare me. Not so much any more. The Jepps sized flow chart card is great. Basically, like Clock's FOM says, it allows dispatch to send you to an airport (and alternate airport) even if the conditional statements in the TAF are below the minimums for the approach as long as a) the main body of the TAF is good and b) there is a second alternate that is good that is listed.

There's a bit more to it then that, but that's the basics.

taseal · May 7th, 2008, 02:35

I don't even know what a 3585 is, and I'm already scared!

I know that however my flight fell in between the TEMPO times, i would def file an alt

Flyin_bryan · May 7th, 2008, 04:06

Quote:

Originally Posted by Clocks

Every time I try to explain 3585 I confuse myself.

To paraphrase my FOM...

3585 allows operation when a forcast's conditional remarks are below dispatch minimums, the main body of forcast must still be above dispatch minimums.

So you can still be dispatched to a destination which has "BCMG, TEMPO" etc below the normal minimums as long as those conditional remarks don't put the weather lower than 1/2 the lowest visibility value.

Your first alternate's conditional statements can't put the weather below 1/2 the visibility AND 1/2 the ceiling minimums.

A second alternate is required and must meet the normal alternate minimums.

:i nsane: