INTER requirements on a TAF
 

To anyone with an opinion....

Out of interest, what do ya reckon about the following TAF:

TAF AMD YPED 202244Z 0024 35018G28KT 9999 -SHRA SCT030
FM03 32018G28KT 9999 SHRA SCT030
FM09 31015KT 9999 -SHRA SCT025
FM12 01010KT 9999 -SHRA SCT025
INTER 0109 32020G30KT 6000 SHRA BKN025
PROB30 INTER 0206 32025G40KT 3000 TSRA FEW015 FEW030CB
FM00 MOD TURB BLW 5000FT TILL 09
T 12 13 13 11 Q 1008 1008 1009 1010

And looking at the INTER requirements in particular....
Given that there are two seperate and distinct INTER periods - and making the assumption that they are both below Alternate Minima - how much fuel would you need to hold assuming an arrival at 0400Z? Two lots of 30min? One lot of 30min? Or just hold on the ground until after 0600Z? :D

Note - OK, I realise that the first INTER (0109) probably isnt below alternate minima.... but lets just say it is!

PS - and make the replies quick - I have my IRT in 2 hours!!!
:p

One lot of 30 mins

Seconded.

520.

Thirded

ITCZ

Just as a hypothetical....
What if you had 29min of Showers with vis at 6000, followed by 29min of TS.... surely that is possible from these INTERs?

That is possible - another situation of what is legal is not necessarily the safest thing to do.

Bevan..

That is just a great TAF for a training exercise or a test, I am suspecting that some ATO in Adelaide has spent a few minutes preparing the forecast for that very reason

My interpretation is the concensus is correct in that 30 minutes Holding is all that is required as determined by the INTER. If the Met office expected the conditions to be sequential, they would have forecast TEMPO.

Clearly the second INTER conditions are the more critical for cat A & B aircraft as it requires 30 Holding or an alternate. The first inter period only applies an operational requirement to Cat D aircraft.

Other options you may consider is the YPAD TAF and does it have the requirements also, (ie - can you use it as an alternate? if it has no requirements it may alliviate the need for holding fuel if you are weight critical) and, what sort of aircraft are you in and is the cross wind component exceeded at any time with the wind changes therfore requiring an alternate as well.

Great post for newbies to consider!

:ok:

splatman
You mean I was right???

You must have taught me well my friend!!!!!.........

Splatman - unfortunately it is the real TAF for today for Edinburgh (as the weather outside is currently proving)... and Adelaide has the same INTERs (roughly).
I do like your reasoning re the TEMPO though....

About the alternate requirements - with the wet runway, the first INTER wind is either right on, or just outside our crosswind limits (depending on how thick your pencil line is) - for a Cat C aircraft

Its an actual TAF!!! - right, i'm off to get that off of NAIPS in hard format so it can be put to good use at some point in the future.

Observer 2 - , ok you got me! - no idea who u r - pm or email me and shed some light :D

Fourthed.

As Ron said today, the book is for the guidance of wise men and blind obedience of fools.

In this example whilst the fool would only carry 30 mins because that's all that's required (assuming the physical capacity to carry more fuel), the wise man would carry maybe 60 minutes, or more, if possible.

Any reference to one gender shall include the other gender

Min legal requirement fuel wise is 30 minutes holding.

But when is a Inter not an Inter? When there is only a 30% probability of it happening?

I'd be carrying all the fuel that ZFW allowed!!!

Chuck.

Right on the money with that statement I reckon, Bevan! :ok:

I'm just starting to take note of a few scenarios where what you say is exactly the case.


520.

Chimbu spot on and I would add to that 1 or even 2 Alternates that obviuosly dont have any requirement. Despsite the rule.

Splatman - how do you figure that the first inter period applies a requirement for Cat D aircraft only. The way I see it the first inter period would be to cover a significant change in wind direction from that forecast and would apply to all aircraft.

Staggerwing

No doubt that any wind change needs to be considered and would apply to all aircraft if it caused the maximum crosswind compent to be exceeded. However I think the question was asked in a general "what is legal" context as there was no reference to the aircraft type. The forecast wind would not make any requirements for an aircraft like a Dash8 which has a 36kt crosswind component.

Without going back to the chart to check, I recall the 6000 meters vis forecast in the first INTER only affected the alternate visibility requirement criteria for Cat D aircraft.

So Visibility was my figuring!

Splatman,

Yep you're correct. Missed the alternate requirement. Was concentrating on the wind direction change during the inter period.

Innovative way of preparing for an IRT! On a different but slightly related note, does any one know where the requirement to hold an alternate for any international destination comes from?

Legally speaking, an INTER only requires 30 mins holding even if two are over lapping (this does not make a tempo as the changed wx conditions are only expected to last for 30 mins at a time, not 60 mins).

However, the second INTER is endorsed with TS. This puts a different light on things if your ETA falls 30 mins either side of 0206 in this example. From memory, if TS are on the TAF (even as a prob), an alternate is required, even if the vis and cloud are not forecast to be below alt minima or the max cross wind exceeded (could be very wrong. What’s your opinion?).

In practice, I would TRY and carry thirty mins holding or more, as your pax don’t really want to go anywhere else other then the destination they have paid to get to, PLUS fuel for an alt as dictated by the endorsement of TS on the TAF. This of course relies on the ability to carry extra fuel.

My money is on an alt is required if you arrive between 0130 and 0630.

This post has come a bit late... Hope you did well in your IRT.

Nah, change of mind now.

If TS are in an INTER or TEMPO yo may elect to hold OR plan for an alt...................

Only if TS are in a TAF or after a FM must an alt be planned:ok: