ETOP's Diversion weather
 

I've just completed a company ETOP's lecture (all fairly standard stuff) but one element seems overly complicated.
I've had a good look through the many posts relating to ETOP's I cant say I can find any info relating to this.

How do you guys calculate the period of time to which you need to apply enhanced weather minima for an ETOP's diversion?
Depending on the amount of equitime points and adequate diversion airfields, it can become a very complicated calculation.......does anyone have any simple rules of thumb etc etc...

From my ETOPS manual:

"PERIOD OF VALIDITY: At each alternate airport, the dispatch weather minima must be ensured during a certain time period. This period of validity starts one hour before the earliest Estimated Time of Arrival (ETA) at this airport and finishes one hour after the latest ETA..."

The earliest ETA at an alternate airport is defined by the departure time plus the normal flight time to reach the maximum diversion distance circle centered on this alternate airport plus the normal flying time to reach this alternate airport considering a diversion from the edge of the circle at the normal cruise speed and level"

The latest ETA at an alternate airport is the departure time plus the normal flying time to quite the maximum diversion distance circle centered on this alternate airport plus the diversion flying time at LRC speed and FL100 to reach this alternate airport considering a diversion initiated on the exit edge of the circle.

However, from a practical point of view and in conjunction with the Computerized Flight Plane (CFP), the diversion point will be taken as the Equitime Point (ETP) between the relevant en-route alternate airports."

I know...it's not the simple rule you were looking for !:)

I also have a nice figure that explain very well the period of validity...but unfortunatly at this time I have no scan available!

we have ours computerised in our flight plan.

I use jetplan...It calculates the ETP's but it doesn't tell you the earliest and latest ETA...anyway it tells you SUITABLE referred to the airport taken as Etops alternate

Thanks guys.......

I guess there is no easy answer:uhoh: :sad:

I use Jetplan also, and our PLOG's show the time band for which the alternate is required. Suggest you get your company to request the info to be computed by Jetplan for you, as we seem to have no issue with getting this info.

Hope you get it sorted.....

30W

Just to add that according JAR rules the enhanced planning wx minimas for ETOPS alternates apply till the ETOPS entry point.
After the ETOPS entry point has been passed, the one engine inoperative landing minimas is applicable.

Eh?

Not according to my Ops manual:ooh: Can you point me to the JAR regs that states that?

haughtney1 it's in accordance to mine, which is JAR approved by the CAA, as like as an other company's OM I had way to see.
I have no direct reference to JAR OPS chapter to show you now, I have to search for it too.

HVIII

There are 2 criteria
1 Planning...apply enhanced mins
2 Inflight.....what you see when you update by ACARS is what you use.... no factor
Dont make it hard....there's too much else to think about

Which is what my Ops manual says..except we dont have ACARS:ooh: :hmm:

Ok, but you update your WX inflight, before entering the ETOPS zone... by...well...whatever means available.

When you (or the Flight Planning guys ) do your plan, the alternates have to be 'suitable', right, and this includes WX to the 'planning' mins ....
eg... you had (or they had ) selected an ALT airport that had a CAT 1 aproach ...the WX has to be 'non precission approach' minimums or better ( 1 step higher ) in the planning stage.... ok cool

In flight, lets say that the WX deteriorated to CAT 1... it is still suitable, because this is now the 'inflight' bit.