Marginal Weather Exemption

[vlamgat]

The other day I heard the term "Marginal Weather Exemption". I haven't heard this before. I have looked in the AIM but can't find any referance to it here either. I was wondering if someone could enlighten me as to its meaning.

Thanks

 

[GearDwnFlaps15]

Exemption 3585

I guess this is what you're refering to. It allows a company to dispatch an IFR flight to an airport or with an alternate when the forecast conditional portion is below minimums but the main body is at or above minimums. It requires 2 alternates.
*The destination aprt conditional remarks cannot be less than 1/2 the visibility for the approach.
*The first alternate conditional cannot be less than 1/2 the required alternate ceiling and vis minimums.
*The second alternate must be at or above the alternate minimums.

In a nutshell, we're going.

 

[SkywayFO]

Ahh, Exemption 3585. Airlines use it to take off with lower that standard legal destination and alternate weather.

 

[jobear]

Hey Skyway how things goin over at ACA?

Jobear

 

[J41CA]

Marginal WX vs. Exemption 3585

Marginal WX and Exemption 3585 are separate things. One has nothing to do with the other.

Marginal WX is simply if the ceiling OR visibility are at their respective minimums at the destination and the alternate, requires the FAR Part 121 release to have a second alternate listed. That's it.

Exemption 3585 is the FAR that allows to be dispatched to a destination with a conditional forecast (tempo, prob, or becmg) lower than the category I landing minimums. For example, assume the destination has a 200- 1/2 approach, the main body wx (visibility controlling) at the destination can not be any lower than the approach minimums (i.e., 1/2 SM) at the ETA. Plus, the conditional portion of the destination wx can not be more than half of the landing minimums (i.e., 1/4 SM).

Exemption 3585 requires two alternates. The 1st alternate ceiling and vis are controlling and the wx must be at the alternate minimum (i.e., 600 - 1 1/2) and if a conditional statement is published, the conditional forecast can not be lower than half of the alternate minimums (i.e., 300 - 3/4). The 2nd alternate wx requirements are the same as the 1st alternate, except that the main body wx and the conditional wx (if there is one) must at or above the alternate minimums.

Clear as mud.

 

[SkywayFO]

Yeah, your right. But who cares if it is good to go,you go oneway or the other.

 

[vlamgat]

Thanks for the info. You're right, "Clear as mud" it is, but I'm at least a bit closer to understanding it now. Thanks again.

 

[w4mch]

Actually J41CA, marginal and exemption 3585 have a long history together. The marginal weather rule you quoted is FAR 121.619. Many years ago, Peoples Express got an exemption to this rule from the FAA, getting the right to disregard all conditional statements in forcasts when determining WX legality. Other airlines tried to get in on the band wagon and capitalize on the FAA's lack of attention in granting an exemption they really shouldn't have. A fight ensued between the pilot groups, the ATA and the FAA. The result is the compromise deal we know as 3585. This is why we can have conditional remarks of 1/2 the required visibility/ceiling.

The history guy...