Cost of carrying holding fuel v diverting

[Ropey Pilot]

Just after some info so can carry out a more informed discussion with 'min-fuel' colleagues.

What is the best way of working out the rough cost of carrying the extra weight of 10 mins holding fuel on every flight and what is the cost of a diversion?

I am talking aboout domestic flights with domestic diversions (20 mins) and a small jet ac (<80 pax).

The basic discussion is to work out how many flights would have to carry this 10 mins hoplding when not required before this costs more than 1 unexpected diversion (runway blocked for 20 mins as an example).

Any input would be appreciated - can probably dig around for the fuel figures, but wouldn't have a clue how to even start finding out how much a diversion costs!

[brain fade]

Here's my 2p worth.
A couple or three hundred extra makes little difference to the a/c's performance but it is great insurance against loads of different things which may happen en route. Weighed against the tiny extra burn its great value insurance. I had to larff a few months ago as the 'min- fuel' boys all got excited when ABC fogged in unexpectedly. Happily we were under considerably less pressure:ok:

[BOAC]

Ropey - an age-old question and one you cannot answer as it is accountant driven. In all my experience the 'operator' would "rather" carry the cost of an occasional diversion (and the passenger disruption it causes!!) than carry 'extra' fuel. This can sometimes include having to replace an out-of-hours crew, but so be it, the accountants rule. It also comes down to 'is 10 mins enough'? Would you all be carrying 10 minutes around on EVERY flight which operates with no delay when this particular 'blockage' requires 20 and you still divert?

Bear in mind that CAA recs are that ALL jet a/c operating into major airports in the 'LONDON TMA' should have 20 mins spare fuel. Take what you judge necessary.

To calculate the cost of 'carrying' use the 3% per hour approximation which works ball-park for most jets eg carry 300kg for 1 hour = use 9kg fuel. 9kg per hour on EVERY aircraft on the fleet which flies 100 hrs per day, EVERY day, 1 diversion in 6 months = drone drone drone. Accountants alert!

[petitfromage]

Not a lot at all.

On the A330 we burn 6000kg per hour.
On a short sector (1:20mins), the 'cost' of carrying an extra 1000kgs is 40kg fuel.

ie: On short sectors the cost is approx 4% of the extra fuel carried.

A diversion (20mins) will cost us 2000kgs. (and of course 2000kgs to get home again!)
In a nut shell, if we saved 1 diversion every 100 flights, it is still more cost efective to carry the extra 10mins fuel.

Bear in mind a diversion actually costs a lot more...in delays, missed services, potentially having to pay for hotel rooms, crew duty costs?

Now, having said all that, most managers are quite happy to gamble that less than 1% of flights will divert and they will probably be correct.

The last word on carrying extra fuel should always be left to the flight crew.....and as the numbers above show, the cost of carrying a bit extra for Mum and the kids is not a lot short haul.

**On a long haul flight it is far more expensive; to carry an extra 1000kgs for 10hrs can cost you 300kgs (30%!)

[ManaAdaSystem]

In the last year alone I have avoided diversions (unexpected wx, ATC problems and holding due priority traffic) four times because I carried a bit extra fuel. Fuel cost is only a portion of the total diversion cost.
In my case I have saved the company a large amount of money, but as you all know, these savings does not show up anywhere in the system. They are only known to me.
To the bean counters I'm just an "expensive" captain.
I'll leave it to others to calculate the minimum fuel policy savings for the whole company, but if I save money on my own, then I'm doing my job, and doing it well. IMHO.

[BOAC]

You all may well like to read this thread (http://www.pprune.org/forums/showthread.php?s=&threadid=158750&highlight=tankering) where this has been discussed before.

[Piltdown Man]

In twelve years I have diverted six times or so (short haul). The only difference that having extra fuel has made is that I held for longer before diverting. Then, I'm the last to land at the alternate and end up with the tail end of the now over-stretched handling. Take min fuel, divert early. It happens so infrequently that it's not worth the hassle.

[Daysleeper]

The economics are quite different for cargo airlines where avoiding diversions is a much higher priority and thus more fuel is carried.

[Ropey Pilot]

Thanks for the input!

I think I shall contine to add an extra pint or two when it is up to me! I have avoided diverting on approx 1% of my trips with a touch extra in the tank and an unexpected delay at the far end and many more times when adding extra for expected ones.

[Pilot Pete]

Got to say I like the Piltdown Man explaination. It happened to me once when everyone with a bit extra fuel was holding due to unexpected LVPs at Manchester. We elected to not even join the stack, diverted to Birmingham and were fuelled and taxying out as about five other aircraft started diverting into BHX!!

One adage to that though is something I was taught many years ago, which always makes sense and that is to have a cast iron diversion. If you don't, then load that extra fuel!

Most fleet managers perfer the min fuel option and accept the occasional diversion. Do remember that under JAR OPS your min fuel still has contingency, diversion and final reserve and unless things have gone particularly against you (or your flight planning system isn't very accurate), on a good weather day you can still do a go-around (perhaps due to a blocked runway) and elect to use your alternate fuel to fly another approach at your destination.

If the weather was marginal then you should have taken extra in the first place, but if you didn't or the wx was unexpected, it just means you need a well formulated plan for if you go around at destination.....or like we did above, stay well ahead of the game and lob in somewhere before you even get to your destination; which is pretty easy throughout Europe, perhaps a different issue flying ETOPS though......!

PP

[Dani]

The main thinking error of the "accountants" is that they calculate the diversion costs with the actual probability, which is, of course, generated by carrying extra fuel by nearly everyone.

If you would carry minimum fuel on every flight, the probability of a diversion would increase tremendously, to say, 10-30%. The theoretical cost curve is an exponential one, as is the cost of extra fuel. Where they hit each other, there is the optimum extra fuel, which might be some hundreds of kg for a typical short haul under normal conditions.

Dani

[Bumz_Rush]

In Ciorporate nowadays, we often have the other extreme, we carry round trip fuel, for the next leg...so we have vast amounts of fuel...only practical problem is making the computed upper flight levels, often not able to make 490/510....

The passenger, does not like his car at the wrong airport, and a 1 or 2 hour hold is the calculated risk.

Bumz