Fuel Q

[Barronflyer]

Just a quick question for the boffins

Had a rather large ZFW drop on the last LH and made the appropriate corrections. (Another CFP was out of the question)

I was wondering if after the correction our CRIT PT fuel serves we're still intact? Is this always the case if I apply the right correction or can we be left short?

Cheers

[BuzzBox]

The answer is yes, the required fuel reserves will always be intact, even if the corrected fuel required drops below the figure shown on the depress ERA analysis on the CFP.

The Line Ops page on the Flight Crew part of IntraCX (under 'Guidelines & Policies') has the answer to this and many other questions.

[China Flyer]

Buzzy is right, although actually working out your new crit point fuels is a bit trickier.

[Barronflyer]

Many thanks indeed for the answers.....any gen then on where I could find the CP correction to fuel?

[SloppyJoe]

Upon recalculation of the fuel after a ZFW drop your crit points are still good.

If after dispatch you are going to be less than required at the crit point after doing your own calculation are you going to divert or keep going?

Once in the air surely it does not really matter, you do what is required and often the airports used in the calculations are totally crazy. Who cares if you have fuel to fly over two suitable airports on the way to your crit point ERA after a depress.

If its good at the planning stage then really thats all you need.

Bet your an Aussie :-)

[Liam Gallagher]

Although FLt Ops say the CFP corrections are good for Mandatory fuel, a few years back had a large 0FW drop and did the correction and established a new Final Req'd. Dispatch ran a new plan and the new plan had 300kgs more as Fuel Req'd. We were probably OK because of the 5% extra built into the mandatory, but I am now cautious about using the corrections on large 0FW drops on long sectors.

Sloppy Joe, as for what to do after airborne, I think you need to talk to a training god. Perhaps also ask him about the difference between "your" and "you're" :}

[crwkunt roll]

"I WILL IF YOU WILL"........
I'll adjust the CFP fuel for a ZFW drop, if you stop crying poor and give us a 30% pay rise just as you've given yourself.

[SloppyJoe]

And perhaps you should have a think about what does and does not require a capital letter.

Grammar, the difference between knowing your **** and knowing you're ****.

[cxorcist]

Threads like these prove what a bunch of wankers we have at CX. You guys would rather haggle over a few hundred kilograms of fuel and grammar than discuss real issues like SHP. We surely make the third floor's job easy by putting our effort into the dumbest topics. What would you like to discuss next? My favorite color?

[DropKnee]

My favorite color is, Ocean Blue.
What's yours?

[ANCPER]

YOU CAN'T HANDLE THE TRUTH!!

[Yeager]

w@nky, w@nky, w@nky..

http://en.wikipedia.org/wiki/******

[bellcrank88]

A very good approximation of the new CP fuel required is found by taking a ration ratio of the new CFP total fuel/Old CFP total fuel and multiply this by the old CP fuel. This will be within a couple hundred kilos. Use the same mandatory if you had it as the change in it will be very small. You can use the same ratio to find what the fuel required at each point is. We used to use this all the time before the days of the FMC.

You can always then ask for a new cfp enroute to backup your math.

(some w@nker will probably point out that a better ratio can be found by leaving the contingency fuel out of the equation, and they would be correct, but the difference is negligible)

[PatObrien]

I'd like to point out that better ratio can be found by leaving the contingency fuel out of the equation.

[Yeager]

I'd like to point out that better ratio can be found by leaving the contingency fuel out of the equation.

[BuzzBox]

Hmmm, there must be a village missing some of its brethren.

[channis]

I'd like to point out that better ratio can be found by leaving the contingency fuel out of the equation. (but the difference is negligible.) And i am friends with that w@nker...

[raven11]

Don't use the old and final CFP fuel in the equation. Instead, divide the new burn off figure by the old burn off figure and then use this value to multiply against any fuel figure on the CFP to get the updated fuel burn off.

[quadspeed]

finally someone who gets it.

[SMOC]

Mmmm

Just spoke to a guy who had the ZFW drop just under 9T going to the west coast of the US, did the correction to the trip fuel/total fuel double check by requesting a new flight pan.

MAND went up 500kg!

New plan showed they were now 1.3T below the legal departure fuel based on their LNDG CORR.

Perhaps CX should say ZFW changes up to "X amount" are acceptable.

[broadband circuit]

MAND went up 500kg!

Let's play them at their own game. Every time the ZFW drops, then rather than use the correction, ask for a new plan.

They have a choice, either give me a new plan (time cost), or I take the CFP fuel based on the original weight (fuel cost). Let IOC decide which is their preferred option.

Unlike many things in fuel policy, Depress Fuel at the crit point is not just a planning requirement, and if you leave without it, or more to the point, arrive at the crit point without it, you are operating outside the requirements of the AOC.

OK, the chances of having a depress at or near to the crit point are slim, and the chances of having it happen on the day you've reduced fuel via the correction are even slimmer.

HOWEVER, if your flight file gets selected at random by the CAD in one of their audits, and they conclude that you were operating not in accordance with the AOC, who gets called into the office? (hint: it's not the dispatcher, or load controller or IOC)

Even worse, if you do it going eastward, there have been cases in the past where the authority at the destination (read NavCanada or FAA) has boarded the flight to do a document audit. Once again, who will be held responsible?

Not worth it, give me a new plan, or I take CFP.

[fire wall]

Trip fuel vs zfw is not a linear relationship
Mand fuel vs zfw is not a linear relationship.
ie if the zfw is down 2% then the burn is not down 2%....worse if the zfw is increased. Why ? Too long a discussion.
Within small variance in ZFW then the corrections are relatively accurate and I would suggest to a limit of approx 2T ULH and 5T on short haul flights.
Within those boundaries I do an adjustment and add a bit for inaccuracies so that I am on the "right" side of the error.
Outside that then get a new flight plan.

[Loopdeloop]

I think most pilots do something similar, although I know some folk like everything to be accurate to the kilo. Unfortunately, flying doesn't work that way. Personally I use the correction figure up to about 5T and add a fudge factor thereafter, always rounding in my favour.
Do we really need everything mandated? I would hope that most pilots can think for themselves using some common sense and airmanship... oops, did I use the A word?

[PatObrien]

That Crit point and associated Mand fuel IS ONLY a planning requirement (hence the term 'flight plan'). ANO requires us to be able to reach a suitable airport if depressed (which I usually am on flights over 2 hrs) hold for 30 min and land anywhere along the route DURING THE ACTUAL FLIGHT. The airports used when Mand fuel is required during the planning stage are usually far and wide, maybe because of planning wx requirements, but really to keep the dummies from cutting it too close and running out of gas during contingencies (like all the other fuel planning rules). If you want to keep eyeballing PANC and Kansai Crit fuel as you cross the ocean, go ahead. But likely RJCC, UHPP, PASY and a few others are suitable during flight, and that Crit pt is a non factor - as is the Mand fuel figure, the 5% contingency, and that vertical descent profile we planned on in Despatch.

If there's someone in CAD that can sort through one of those abused flight plans and actually find someone who was below Enroute Diversion Fuel during flight, and you can prove this myth, I'll give you my next year's bonus.

[Liam Gallagher]

Like I said before, talk it through with some of the trainers. There's a lot more to this than meets the eye. The OP mentioned crit pts, which could be ETOP points, that can be dealt with by selecting another ERA. Mandatory Fuel, is a bit more complex as you probably don't have scope to select other ERAs. Do you need it once you dispatch anyway???

I agree with Firewall and have experienced the same with a large 0FW drop (5T). Had we used the corrections on the original CFP we would have dispatched with 500kgs less than the new CFP calculated. The corrections assume linear changes and over a small change-weight range are a useable approximation, however over a larger weight change and a long flight these assumptions get stretched.

Again, talk to to an adult, but when carrying Mandatory, I reckon our Fuel Required is calculated on the basis of depressurising at the most critical depress crit.pt, and then we fly at FL140 etc, which means we are so far off Optimum Level (particularly in the 747) for a long period of flight. Put all this together, and I am cautious when carrying Mandatory on ULH, the change between weight and burn is not linear and ratios become unreliable proportionate to weight change.

Don't get me wrong, the corrections are good 99.9%, however on ULH when carrying Mandatory, I am cautious. ETOPs, different game as you can probably pick other ERAs to launch, the use the FMC airborne to finese and monitor.

Clear as mud?

[China Flyer]

Pat: I don't really agree with you, but that's because where I fly, the planned ERAs are the only ERAs.

Therefore, I really need to have the planned fuel when I'm in the air, 'cos there are no other options available.

So I think that BC's statement here is absolutely correct: Unlike many things in fuel policy, Depress Fuel at the crit point is not just a planning requirement, and if you leave without it, or more to the point, arrive at the crit point without it, you are operating outside the requirements of the AOC.

[fire wall]

Pat, whilst what you say is correct I side with China Flyer.
On NoPac and Polar routes in winter the ERA's are the only options I have and , on a particularly bad day they are RJCC-PACD and PACD-PANC. Petro is one way and normally vis ugly in +SN and Shemya has a wind that would strip flesh whilst claiming <1000ft in FZFG (yup, how in 50kts is beyond me) and to top it off vvv///.

If I am missing something then I am happy to be corrected .

[PatObrien]

China, give me an archived filght plan on the route you're referring to and I'll take a look. Even if the airborne ERAs are the same as the planned, you still have the 5%, and to a lesser amount the immediate descent to 14 or 10k, which may be TONNES different from what is actually required airborne.

Have you or anyone you know ever gone below this INFLIGHT requirement? If so, what was the resulting course of action?

I'm having trouble recalling a time on NOPAC when I was stuck with the same ERAs inflight. UHPP is an option 90% and PASY 30-40%.

[bellcrank88]

On almost every single YVR flight you are limited in your choice of ERA's. There are no other options.

Somewhere in what used to be Vol 1 and is now Ops A it used to say that if the change in weight was more than 5T, then get a new flight plan. Can't seem to find it anymore although it may be hidden there somewhere.

[cxorcist]

Now that seems like a useful number. I can remember that...