Fuel requirements ( IFR question )

[Motor Plane Driver]

TAF YXXX 200131Z 0214 30010KT 9999 BKN 040
FM05 24015 3000 RAIN BKN005 BKN010 INTER
0205 3000 BKN010 SCT015 T 12 12 11 13 Q 1011
1008 1008 1009

ETA 0415
ALTERNATE MINIMA ( 1230 - 4.4 )


Do you need an alternate or just 30 mins holding fuel? (remembering the 30 min buffer on the FM period ) If an alternate is required or not, what is the reference in the AIP?

cheers.

[Sperm Bank]

ETA 0415

This requires 30 Holding. An "operational requirement" becomes effective 30 min prior to the onset of a FM period. Your ETA is 15 before that.

Don't know the AIP haven't used them for years. Jepps AU 304 detals the appropriate stuff for you.

[compressor stall]

Are there any special alternate minima on the chart, and more importantly is your potential aircraft fitted with them?

[hoss]

MPD, to answer your question you only need 30 minutes holding OR a suitable alternate. Jeppesen ATC AU-303 3.2.1/3.2.4/3.2.7 should help, like Sperm Bank I dont use the AIP :) . Operationally, on this one I would have a fair bit of margin as if you are 15 minutes late you could be subject to the worsening conditions(30 minutes prior to the FM05) and in this case you have to assume things are not going to get any better until 14:uhoh: .

[Motor Plane Driver]

So if you arrive at 0415 and hold for 30 mins making it 0445, the alternate requirement because of your 30 min buffer on the FM period only applies to your ETA ( 0415 ) which you arrive before?

[hoss]

Basically, yes but the easy answer is carry a suitable alternate:ok: . You could interpret that in this case the INTER is only good until 0430 due to the deteriorating FM05 (0430). This situation is not 'directly' addressed in the Jeppesen/AIP documents(overlapping INTER and a deteriorating FM period), difficult situation and open to interpretation.

From a practical and operational perspective I would carry 30 minutes to 'have a go' and my suitable alternate. Lets face it, it doesn't take much to get 15 minutes behind schedule and then you are going to be subject to the FM operational requirement anyway.

[Dehavillanddriver]

my thoughts only...

The from period is from 0500 - and your ETA is 0415.

You fall within the inter period, which has conditions below the alternate minima, which means that you need the 30 mins holding fuel. it is interesting to see the number of people who see inter or tempo and automatically stick 30-60 mins extra fuel on-board - even though the inter/tempo doesn't drop the conditions below the alternate minima.

The alternate requirements kick in at 0430 - but that is a buffer on the 0500 actual estimated commencement of the rotten weather.

The practical thing is that if you can carry extra gas I would, on the basis that more is better in these cases, but the legalities are that you only need 30 minutes - in my opinion this remains the case as you revise your estimate up to 0429.99999999999 after which you need to have alternate fuel - thoughts anyone?

PS it is nice to see a flying related discussion that isn't a slanging match...

[Sperm Bank]

Dehav I agree. Hope that does not put the mockers on it. What yourself and Hoss have said is correct. LEGALLY 30 holding is all that is required. Even if it was zero zero at 0500. PRACTICALLY I don't think there would be too many troops who would not have enough to divert in the stated conditions, particularly if they were going into a non precision rwy.

[8 8th's Blue]

Look's like one of those questions used to suck you in in the IREX! Just be aware that the inter period 0205 already is below the alternate minima.

[QSK?]

MPD:

ALTN minima 1230/4.4. Your ETA is 0415.

1. First of all, it must be appreciated that "INTER" does not necessarily mean that 30min holding fuel has to always be carried. Go to AIP GEN 3.5-6 and you will see that INTER simply means that weather conditions can be expected to change frequently for periods of less than 30 mins.

2. For example, it may be possible (but highly unlikely) for a pilot to receive the following TAF:

TAF YXXX 200131Z 0214 30014KT 9999 BKN040 FM 11 24015 9999 SCT060 BKN085 INTER 0509 9999 SCT015 BKN030.

Using your alternate minima, this TAF does not require an alternate, and the weather conditions forecast for the INTER period (+/- 30 mins either end) are also above the aerodrome ALTN minima. Therefore, there would be no requirement for the pilot to even carry 30 mins holding fuel, despite the fact that the forecast is endorsed with "INTER" (Reference AIP ENR 1.1-85 para 71.2.3).

2. 30mins holding fuel is only required to be carried if the forecast change under "INTER" deteriorates below the ALTN minima.

So, my interpretation of the your TAF is that you definitely need to carry an ALTN. My rational is:

1. From 0130-0430: INTER requiring 30H due to the vis being less than the alternate minima of 4400 metres

2. From 0430-1430: Altn required due to vis and cld both being less than the alternative mimima of 4400m and 1230ft.

3. Sure on the face of it, it looks like only 30H is required as your ETA is 0414, but the fact is that, once you've arrived over your destination at 0415 you have to account for the fact that you may actually have to hold for another 30 minus until 0445 at which time, you now fall into the ALTN requirement period.

Although AIP ENR 1.1 71.2.3 allow for holding fuel to be carried in lieu of an alternate if weather conditions improve, the fact is that the improvement in this case is still below the published ALTN minima (VIS being 3000m when 4400 required).

Relevant AIP references are: ENR 1.1 71.2.1 and 71.2.3

That's how I see it but if I'm wrong, then I would appreciate it if someone could put me right.

[splatman]

QSK?

Hate to say it but while carrying the fuel for an alternate in this case may well be prudent with available payload, there is cartainly no legal requirement to carry the alternate fuel.

Your references to the 30 minute holding are correct in that the ETA is inside the 30 minute buffer. The Alternate requirement only applies if your arrival time is after 0430.

While I understand the logic you are applying in this case, the key to the whole interpretation is the phrase "arrival at the destination". As the arrival time is at 0415, it falls inside the 30 Holding requirement but outside the BUFFER period of 30 minutes for the deterioration to alternate conditions.

Hope that view helps.

Cheers

[QSK?]

Thanks for your reply, splatman. I really appreciate your response as I'm always willing to learn.

My only question is what happens when you arrive at your destination, hold for the 30 mins in the expectation that you might be able to make an approach and then find that you still can't get in? Now you don't have any fuel (save for the statutory 45 mins + variable reserve) to go anywhere.

What's the next trick? (probably, as you say, its prudent to carry the alternate fuel but not necessarily a legal requirement).

R/QSK?

[EngineOut]

I have another Q on this topic (not related to this TAF):

If you have an inter and a tempo (say, one for TS and one for low cloud/vis) which are below the alternate minima and both are valid for your arrival time, do you:

a) only need to carry 60 mins (as worst case)? Or,

b) Carry 90 minutes (30 + 60 mins)

of holding fuel?

[splatman]

QSK

We would all hope that the MET office got it right. If the conditions were such that the deterioration lasted longer than 30 minutes the forecasters got it drastically wrong. It should have been specified as tempo or alternate from the beginning.

In 20 years of flying (geez i feel old!) Ive never found (placed) myself in a situation that has left me with no alternatives. You really need to consider all the options enroute, including your PSD. If your fuel load is critical and the weather marginal at the destination, source some enroute reports from other aircraft, ATC or ground stations, get all the information you can and make a balanced decision, then continually evaluate the progress to ensure your still on the right track.

Engineout

The two periods would not be cumulative and would generally only be forecast as such if the two conditions create operational requirements that are based on differing criteria.

For example a forecast Tempo due to reduced viz or cloud may be a requirement for aircraft that do not have special alternate minima capability (2 ILS etc,etc) but those that are capable of complying with the special alternate minima do not need to plan for the 60 holding. While the same forecast over the same period may have an INTER for TS. Obviously all aircraft need to carry the 30 holding as an operational requirement but other aircraft may need to carry increase their planning fuel to allow for the tempo.

Hope this helps

Cheers

[Blue Heeler]

Good, good, .....but wrong

The AIP states:

72.2 Weather conditions
72.2.1 Except when operating an aircraft under the VFR by day within
50NM of the point of departure, the pilot in command must provide for a suitable alternate aerodrome when arrival at the destination will be during the currency of, or up to 30 minutes prior to the forecast commencement of, the following weather conditions:
a. cloud – more than SCT below the alternate minimum (see
paras 72.2.11 and 72.2.12 ); or
Note: In determining requirements for alternate aerodromes, forecast
amounts of cloud below the alternate minima are cumulative.
For determining requirements, the cumulative cloud amount is interpreted
as follows:
FEW plus FEW is equivalent to SCT,
FEW plus SCT is equivalent to BKN,
SCT plus SCT is equivalent to BKN or OVC.
b. visibility – less than the alternate minimum; or
c. visibility – greater than the alternate minimum, but the forecast
is endorsed with a percentage probability of fog, mist, dust or
any other phenomenon restricting visibility below the alternate
minimum; or
d. wind – a crosswind or downwind component more than the
maximum for the aircraft.
Note: Wind gusts must be considered.


What is the arrival time? 0415

What is the forecast WX at 0415? 9999 BKN 040 Altn required? No

Is the arrival time within the currency of or within 30 minutes of the onset of Wx forecast FM 0500? No. Alternate required? No

Is holding fuel required? No. Carrying holding fuel is an option in lieu of carrying fuel for an alternate. No alternate fuel required therefore no holding fuel required.

PS Is the TAF reported correctly? Unusual to see an INTER period where there is an improvement.

Also maybe one or two people have misread the TAF. INTER applies FM 0500 and Wx during INTER periods is 020/5kts 3000m etc 0205 is not a time.

[Tinstaafl]

0205 most definitely IS a time. A wind change as you suggest during that INTER period would be given as 02005. Note the difference.

Using the Altn min specified & the arrival time: ETA 0415
ALTERNATE MINIMA ( 1230 - 4.4 )

Taking each section separately:

AF YXXX 200131Z 0214 30010KT 9999 BKN 040

Applies from beginning of forecast until end OR until a permanent change is specified ie a FM

Vis is not <4.4km --> no altn req'd
Cld is not >4/8ths below 1230' --> no altn req'd

INTER 0205 3000 BKN010 SCT015

Applies from 0200 to 0500Z. Operational requirements have a 30 min buffer either side of the times.

vis is <4.4km --> altn OR 30 min holding req'd
Cld is >4/8ths below 1230 --> altn OR 30 min holding req'd

Holding is an option because it is an INTER period.

This applies because arrival time is within the period covered by the INTER & its buffers.

FM05 24015 3000 RAIN BKN005 BKN010

Applies from 0500Z. Operational requirements have a 30 min buffer.

Vis is vis is <4.4km --> altn req'd
Cld is >4/8ths below 1230 --> altn req'd

Holding is not an option because it is not a TEMPOrary or INTERmittent deterioration.

Does NOT apply because the arrival time is outside the buffer period, let alone the time of commencement.

[Dehavillanddriver]

Blue heeler - would you like to phone a friend?

INTER 0205 3000 blah blah does NOT mean that the wind is 020/5 - christ where did you get that from?

[Blue Heeler]

Tinstaffl, you are perfectly correct. 0205 is a time period. I think the INTER 0205 should be reported before the FM 0500 then it reads correctly.

Dehavillanddriver.

Thankyou for your kind remarks. I think we all know how wind is reported.

If you look at my PS comments you'll see that I questioned if the TAF was reported correctly.

I was suggesting that perhaps the TAF was mistyped and the group of figures 0205 was supposed to be a 02005 i.e. wind and not a time. Perhaps I didn't make that clear.

If you put the INTER in its correct sequence before the FM it would seem to to solve the problem.

Do you agree?

[Tinstaafl]

It makes no difference. There will always be a time associated with an INTER**, TEMPO** or FM. The trick is to look for it.

Whilst in this case it would probably read a bit better since the INTER neatly fits between the forecast time & the FM, that's not always the case. What if this INTER was 0207? A perfectly reasonable forecast since it's a fluctuation around the base conditions (the original forecast then the FM05).

Or what if there were multiple FMs?

I have no problems with either layout:

1. Permanent changes in chronological order then fluctuating changes, also in chronological order, or

2. Everything in chrono. order based on start time.

Either way you still have to digest each section separately & then apply its operational conditions to your flight.


**A possible exception: When the INTER or TEMPO is applicable for the entire period of the forecast. It's conceivable, but unlikely, that the forecast could read

YABC prep. date 0606 various Wx INTER fluctuating Wx.

The only way to read this is that the INTER applies throughout the forecast validity period. Unlikely to be written this way though...

[splatman]

Christ,

I thought I was going to have to hand back my delegations because I had been interpreting TAF's incorrectly and had lost the plot.

This type of post is great to clear up this sort of issue and help some people along with application of AIP etc. Keep up the good work guys.

:ok:

[Motor Plane Driver]

Getting back to the original question, what is the legal answer? I think we all argee that we need 30 mins holding. Do you need an alternate or not? ( some say yes and others say no ).
Thanks for the posts already.:D

[QSK?]

MPD:

Based on the advice that I've seen on this forum, I think the answer is defintely only 30H is required.

Tks splatman and others. Just shows to go ya that you can learn something new every day!

[hoss]

MPD, the legal answer is 30 minutes holding or a suitable alternate(which ever one will work best for you) inorder to meet the INTER requirement. Simple as that:) .

My first employer used to have a slogan in the hangar that read "If there is any doubt, there is no doubt" every now and then I reflect on that one.

[Howard Hughes]

MPD, 30 mins is it, but if your alternate is only 15 or 20 minutes away well hey, whats wrong with only carrying that?

But of course its always good to have a back up plan, for when the forecast is wrong!!

Cheers HH.

[Dehavillanddriver]

blue heeler - sorry if i offended you - I was just blown away by some of your comments....

with regards the positioning of the inter period vs the FM, belowis the current taf for sunny adelaide.

You will see all the fm's in the body of the taf and then the inter at the end - that is how I would expect to see it - which is the way i read the taf in the opening post.

once again my apologies- but I was quite surprised to see your answer....



TAF TAF YPAD 281053Z 1212 01008KT 9999 LIGHT SHOWERS OF RAIN BKN100 FM21
34015KT 9999 LIGHT SHOWERS OF RAIN BKN090 FM04 24010KT 9999 LIGHT
SHOWERS OF RAIN BKN090 PROB30 INTER 1812 32016G32KT 8000
THUNDERSTORMS WITH RAIN SCT080CB T 23 23 24 26 Q 1014 1014 1013 1013

[Tinstaafl]

When did Oz drop 'RASH' & 'TSRA' & '+' or '-' modifiers for the verbose version? And why? :confused:

[topdrop]

They haven't dropped it. If you ask for forecast in briefing format you get it as above. If you ask for forecast in message format you get + - etc.

[Tinstaafl]

Ta. Been several years since I last got an Oz Wx brief.