VCTS: Alternate Requirement?

[m.r.a.z.23]

Thanks for the replies. Here are the applicable TTFs:

201710220300 METAR YSSY 220300Z 08012KT 9999 FEW032 SCT050 20/10 Q1012 NOSIG=
201710220330 METAR YSSY 220330Z 12013KT 9999 VCTS VCSH FEW030 BKN100 FEW060CB 19/11 Q1012 NOSIG=
201710220400 METAR YSSY 220400Z 14010KT 9999 VCTS -SHRA FEW020 SCT030 BKN055 FEW060CB 18/13 Q1013 NOSIG=
201710220412 SPECI YSSY 220412Z 12009KT 5000 TSRA FEW017 SCT022 BKN040 SCT050CB 17/14 Q1012 FM0430 12012KT 9999 -SHRA SCT025 BKN040=
201710220430 SPECI YSSY 220430Z 15012KT 9999 -TSRA FEW018 SCT030 BKN040 FEW050CB 16/14 Q1013 RESHRA FM0415 15012KT 9999 -SHRA SCT025 BKN040=
201710220430 METAR YSSY 220430Z 15012KT 9999 -TSRA FEW018 SCT030 BKN040 FEW050CB 16/14 Q1013 RESHRA FM0415 15012KT 9999 -SHRA SCT025 BKN040=
201710220446 SPECI YSSY 220446Z 19017KT 6000 TSRA FEW016 BKN020 BKN030 FEW050CB 16/15 Q1013 FM0500 15012KT 9999 -SHRA SCT025 BKN040=
201710220500 METAR YSSY 220500Z 13017KT 9000 4000SE -SHRA FEW016 BKN022 BKN035 16/15 Q1012 NOSIG=
201710220500 SPECI YSSY 220500Z 13017KT 9000 4000SE -SHRA FEW016 BKN022 BKN035 16/15 Q1012 NOSIG=
201710220515 SPECI YSSY 220515Z 11013KT 9999 -SHRA VCTS FEW013 SCT022 BKN037 FEW060CB 16/15 Q1012 NOSIG=
201710220530 METAR YSSY 220530Z 08009KT 9999 -SHRA VCTS FEW012 SCT024 BKN055 FEW060CB 16/14 Q1012 NOSIG=
201710220600 METAR YSSY 220600Z 10009KT 9999 VCSH FEW014 SCT080 BKN120 17/14 Q1013 NOSIG=
201710220630 METAR YSSY 220630Z 12009KT 9999 VCSH FEW018 SCT024 BKN085 17/13 Q1013 FM0730 18015KT 9999 -SHRA SCT020 BKN040 INTER 0800/0930 4000 SHRA BKN015=
201710220700 METAR YSSY 220700Z 13010KT 9999 VCSH FEW012 SCT024 BKN120 17/13 Q1013 FM0720 18015KT 9999 -SHRA FEW010 SCT020 BKN040 INTER 0720/1000 4000 SHRA BKN010=
201710220730 METAR YSSY 220730Z 14011KT 9999 4500SE -SHRA FEW010 SCT023 BKN060 FEW030CB 17/14 Q1013 FM0745 18015KT 9999 -SHRA FEW010 SCT020 BKN040 INTER 0730/1030 4000 SHRA BKN010=
201710220800 METAR YSSY 220800Z 11007KT 9999 VCSH FEW012 BKN055 BKN095 15/13 Q1014 INTER 0830/1100 4000 SHRA BKN010=
201710220830 METAR YSSY 220830Z 10005KT 9999 -SHRA FEW015 SCT024 BKN075 16/14 Q1014 INTER 0830/1130 4000 SHRA BKN010=

The The METAR/SPECIs of 0400, 0500 & 0530 were the ones that had us pause and have a think.
Just to clarify, we had full alternate fuel but not much in the way of holding, so with an ETA of 0630 we were hanging out for that 0600 METAR to be comfortable hanging around.

Maybe my way of thinking needs to shift, but my understanding was that every part of the TTF has the ability to impose requirements,
not just the NOSIG/FMxx (trended) parts, which seems to be what some previous posters have been implying (sorry if I've misread). If, like in 0412/0430/0446 TTF METAR/SPECI
(trended METAR in the rest of the world) above, there is TS in the actual weather, then alternate/holding fuel is required.

The AIP also says that "The TTF supersedes the TAF for its validity period and is the current forecast for pilots of aircraft whose arrival time falls within the validity period."
Therefore, surely the entire TTF has the ability to impose operational requirements, not just the trend. So it really all hinges on the VC qualifier as to whether that constitutes
"at the destination" per AIP, which the consensus has been that it does not.

Yes, there's the commonsense argument saying if you had TS at a little over 4nm away you'd probably want some extra fuel (which I completely agree with), but my question
was to do with the scenario as described, because the wording of the forecast could necessitate or prevent a diversion.



P.S. Something else that had us scratching our heads was the 0430 METAR forecasting a change FM0415...

[m.r.a.z.23]

Originally Posted by FGD135

You will never see VCTS in a forecast. Therefore, VCTS cannot trigger the operational requirement. This can only happen via a TAF or ARFOR.

Can't find a current Aus TAF with VC, but here is the current one from Pago Pago:

TAF NSTU 291734Z 2918/3018 10013KT P6SM VCSH FEW015 SCT040 BKN100
FM300800 10010KT 6SM -SHRA VCTS SCT025CB BKN040 OVC100
FM301600 10010KT P6SM -SHRA BKN025 OVC040

Now obviously for this TAF you'd be holding a full alternate from 0730 unless the METAR said otherwise, but purely for legal min fuel, there's no requirement. Would be a moot point though because their regs don't require alternates based on TS!

I'm pretty sure I've seen VCSH on a Aus TAF before though?

Edit: Having thought about it, the BOM usually use plain english when discussing Present Weather for TAFs (again unlike the rest of the world), e.g. "Showers of Light Rain" or "Showers in the vicinity". So you might see "Thunderstorms in the vicinity" on a TAF, but maybe they just use "Thunderstorms" to cover themselves.

[Capn Bloggs]

201710220330 METAR YSSY 220330Z 12013KT 9999 VCTS VCSH FEW030 BKN100 FEW060CB 19/11 Q1012 NOSIG=

Assuming that is a TTF (not annotated as such but neither are any of the others), NOSIG means no significant change from what is currently happening=alternate required because of the (VC) TS. AIMHO!!

[Derfred]

That line of TTF's is exactly what I was going on about in the Poor Man's Radar thread on this forum yesterday.

The BOM knew there was a risk of TS's but refused to put it on the TTF until they had to.

The first TTF is a blatant lie because NOSIG meant no chance of TS for the next three hours. Well, the TS's turned up shortly after that. I can't believe they couldn't see that possibility, or are they just that incompetent?

I'm sure any pilot who happened to have access to the BOM radar when that first TTF went out would have said "bullcrap". But most pilots inflight don't have access to that.

The BOM needs to man up. Peoples' lives are at risk if a pilot turns up at an airport with a TS over the field and no options.

[FGD135]

... there is TS in the actual weather, then alternate/holding fuel is required.

This idea doesn't work. Consider taking off from A for a long flight to B. Whilst loading fuel at A, a perusal of the forecast for B shows that there are no operational requirements at B. So, no alternate/holding fuel is loaded.

Then, during the long flight, and now 10 minutes away from B, the METAR for B suddenly mentions TS. Is it now the case that you need to be carrying alternate/holding fuel?

Of course not. The legal requirements were fully met before departing from A.

This must also be the case if an amended TAF for B (now forecasting TS) was issued 10 minutes out.

Can't find a current Aus TAF with VC, but here is the current one from Pago Pago ...

It must be the case for that place that they always use VCTS and never TS in their forecasts. This is probably more efficient than what we do here in Australia (i.e one code for Pago Pago, while we have two: TS and VCTS).

I'm pretty sure I've seen VCSH on a Aus TAF before though?

This would mean that the BOM have the forecasting accuracy to discern whether the thunderstorms are going to be within 5 miles (TS) or outside that (VCTS).

I don't believe they have that accuracy at the moment, which is why I say that in Australia, you will only see VCTS on a METAR or the report portion of a TTF - and being the report portion means it is not the forecast portion, which means the alternate/holding rules don't apply.

[Dale Hardale]

Not 100% sure of my facts here regarding the Aussie AIP, but my understanding was if an amended TAF/TTF is received in flight that has weather conditions below the alternate minimum, including INTER, TEMPO and PROB TS, then yes, extra fuel needs to be on board to meet this requirement or a diversion initiated.

Anyone provide more factual info with this and whether this is right or wrong?

[Lookleft]

That discussion has occupied the time of many an airline flight deck. Should you get a TTF inflight if the fuel you departed with was legal? There is no requirement to update a TTF if the one you based your decision on was valid for your arrival. By updating inflight and if there is now a requirement you have just sold yourself a hospital pass. If you don't have the fuel then you must divert or calculate a PNR and hope for an improvement in the weather. Don't tell don't ask is the underlining principal.

[Derfred]

Correct, Dale.

Except that a diversion need not be made immediately, you may continue to your latest diversion point in the hope that a further TTF will be released removing the holding requirement.

You must at all times in flight have the fuel on board to proceed to "an" airport for which you have the fuel including reserves and any required holding.

If you have proceeded past your latest diversion point and a subsequent TTF adds a holding requirement for which you do not have fuel, then you have a potential emergency on your hands. You would then need to take safest course of action, which may include landing below minima, landing in a TS, diverting with less than legal reserve, or diverting to a runway normally unsuitable for your aircraft type. None of them are very pretty options, and in the event you survive, would likely result in a safety investigation.

This is why I believe the perceived BOM policy of under-forecasting is bordering on criminal, especially when TS or FG is a possibility.

[Derfred]

Lookleft,

I would argue that if you haven't made every effort to obtain the latest TTF approaching your latest diversion point, you could be held liable for some offence.

If I recall correctly, the investigation into the Adelaide-Mildura diversions by a couple of 737 concluded (amongst other things) that both the airlines and the pilots should have been more proactive in monitoring the weather.

I've been involved in more than one situation of landing a airliner in poor weather with min fuel because we ran out of options. All when I was in the RHS. I'm touching wood here, but since I've been in he LHS it hasn't happened. I do my best to make sure it doesn't happen. And intentionally not updating weather in case it's gone downhill doesn't fit well with that philosophy...

[maggot]

Originally Posted by Lookleft

That discussion has occupied the time of many an airline flight deck. Should you get a TTF inflight if the fuel you departed with was legal? There is no requirement to update a TTF if the one you based your decision on was valid for your arrival. By updating inflight and if there is now a requirement you have just sold yourself a hospital pass. If you don't have the fuel then you must divert or calculate a PNR and hope for an improvement in the weather. Don't tell don't ask is the underlining principal.

Yes I too like to blindly back myself into a corner

Hazard alerts kinda sink ya tho eh

[Lookleft]

Agree with you both. If I am keeping an eye on the trend with FG then I update every half hour but will usually have the fuel to go somewhere else anyway. If however the TTF has gone to INTER or TEMPO BN 0500 when I know that I can still get in off a CAT 1 ILS then I will impose the Rumsfeld defense: "there are unknowns and known unknowns" If you have a TTF that covers you for your ETA then I don't consider that you are then required to update the weather in case the BOM wants to hedge its bets.

[FGD135]

... Anyone provide more factual info with this and whether this is right or wrong?

Dale, this is not correct. There is no such rule because there CANNOT be any such rule.

Cannot, because if there was such a rule, it would be frequently broken - without the PIC able to do anything about it.

Refer back to the example I gave earlier. If place B is remote then there is a good chance that the aircraft will not have the option of diverting or holding.

This is why there cannot be any such rule.

For those really remote places like Norfolk, Christmas and Cocos Islands, the rules have a special way of making sure you have diversion fuel. That is the "remote islands policy".

[Derfred]

FGD, your example was 10 minutes from destination, and assuming you have passed your latest point of legal diversion, you are now in a potential emergency, as I said. There is no ruleset for that other than to follow the safest course of action in the unfortunate situation you now find yourself in.

But prior to your latest point of legal diversion, you must divert (or continue to that point and then divert if no improvement).

[Lookleft]

FGD135, the most remote capital city on earth is Perth and it is not covered by any remote airport policy although Qantas now has a AV for Perth. I agree there is no black and white with TTFs and I refer back to my original statement that CASA won't provide an opinion until you are involved in an incident that is related to the weather forecast then it will be the pilot's fault. Whenever I go to Perth, Darwin, Cairns or Townsville I always have an alternate regardless of the forecast.

[Derfred]

Originally Posted by Lookleft

Whenever I go to Perth, Darwin, Cairns or Townsville I always have an alternate regardless of the forecast.

You can be my wingman any time.

If however the TTF has gone to INTER or TEMPO BN 0500 when I know that I can still get in off a CAT 1 ILS

Fair enough, I won't labour my point on that situation. It's FG and TS that I lose sleep over. And BKN 0500 doesn't turn into FG. FG and TS are the events that the BOM regularly under-forecast. And those are the events that can eat aeroplanes.

[Lookleft]

I forgot to include AYQ and AS in that list.

[FGD135]

But prior to your latest point of legal diversion, you must divert (or continue to that point and then divert if no improvement).

Derfred, can you point to the legal reference behind this statement?

Note that this topic is not about emergencies and what we would each do in these situations.

It is about what the rules say for these situations. This is why I ask you for the legal reference.

[Derfred]

FGD, I don't have a reference at hand, I would have to search. I'll get back to you if I can find it.

[framer]

Dale, this is not correct. There is no such rule because there CANNOT be any such rule.

I think Dale is correct. If he/she isn't then what is the purpose of Australia's ' special Alternate minima' ?

[travelator]

I think Dale is correct. If he/she isn't then what is the purpose of Australia's ' special Alternate minima' ?

Yep. Alternate and holding is required when forecast, no caveats for if already in flight.

I remember a few years ago arriving into BNE and a TTF was issued indicating vis below the special alternate minima for the duration despite the ATIS and TAF indicating better. After some aircraft began diverting, ATC queried why this was happening. Once they were informed that thanks to the TTF, BNE now required an alternate, a new TTF was issued with the vis slightly above the minimum!