Derived values - 3585 rule

[TheFlyingTurkey]

I was going over the 3585 rule and was wondering if anyone could explain "derived values" or "derived minimums"?

Thanks for the help.

[Sig]

Just an arbitrary way of increasing an airport's needed weather for dispatch. Easy way to remember the increase to the published mins is "1 and 4 for one, 2 and a 1/2 for two."

• For airports with 1 instrument approach (including circling)
o Add 400ft to Cat. 1 HAT or HAA
o Add 1 SM to Cat. 1

• For Airports with at least 2 approaches to different runways (no circling)
o Add 200ft to higher Cat. 1 HAT
o Add ½ SM to higher Cat. 1 visiblity

Take a vanilla ILS approach: CAT I mins are typically 200' and 1/2. You add the 1sm and 400', you get 600' and 1 1/2 derived values (sound vaguely familiar for alternate planning, don't they!)- so you can apply the exemption to the weather forecast AND/OR plan for the second alternate.

The real exemption is the ability to dispatch the plane on the strength of the TAF's main body, ignoring conditional (PROB, TEMPO) remarks that the weather will go south by ETA . Calculate the derived values, check the 1/2 vis, 1/2 derived values, and derived values for the intended destination, the 1st alternate, and the 2nd alternate respectively, and get the heck outta there. The thing is you actually need to know this stuff- sometimes our flights are dispatched on data that is hours old, and the release needs to have another airport or two to be legal by the time we're cranking an engine.

Wasn't it so much easier under part 91?

[TheFlyingTurkey]

Thanks for the help!

[Sig]

Hope it worked. It really becomes second nature, but if you go to an airline with a pretty steep training curve you'll be glad you hashed this stuff out ahead of time so you can focus on the plane.

AMOF, a need for an alternate of some kind that needs to be amended on the release happens at least twice a month to me. TOA are usually the real pain in the can- when you fly from SBY to PHL, you can make PHL the TOA and SBY the ALT, PHL the second ALT- all because of the exemption and what it allows (forecast weather versus what we're seeing right now)!!!!. Instead, they were dispatching us to PHL with a ROA or ORF alt, PHL as the TOA, and PHL is the first intended destination- why not make sure the plane gets to A: the destination, or 2: the place it left?! Pay attention to this kind of weirdness, bring it up to the captain in a tactful way, and you've earned your money as he calls DX for a fixed release.

Now if you can figure out crew rest, compensatory rest, and duty times and obligations after 14 hours... that wickedness needs to be left to NASA or Enron actuaries.

[zerouniform]

What is the 3585 rule? Unfortunately I haven't heard of it before.

What does it say?

Thanks for the info.

[mtsu_av8er]

[ QUOTE ]
What is the 3585 rule? Unfortunately I haven't heard of it before.

[/ QUOTE ]

It basically states that a dispatcher may dispatch an aircraft to an airport that has a conditional forecast LOWER than required minimums, as long as there is at least one alternate airport available.

It's a little more complex, but that's the general idea . . . let's a dispatcher get his/her planes out when the regs otherwise would not let him/her do it.

Search for 3583 here , and see what you come up with.

Exciting reading, I tell you . . .