callegro From United States of America, joined Jun 2009, 17 posts, RR: 0 Posted (7 months 2 weeks 1 day ago) and read 2560 times:
So I do a lot of long hauls with the PMDG 747 and I have FS Fuel which is a server that provides a computerized flight plan. Just a few questions about real world operations as for a 747-400.
What is contingency fuel? the default is set to 3% but in a real CFP I have seen it set to 9%.
There is also an option to select how many minutes of taxi fuel is needed. What is the norm for that?
Also an option for how many minutes of APU fuel needed. I know the APU is rarely run anymore do to ground power at the gate, but how many mins are usually in the CFP?
Then you have extra fuel, how much is usually loaded?
CosmicCruiser From United States of America, joined Feb 2005, 2212 posts, RR: 16 Reply 1, posted (7 months 2 weeks 21 hours ago) and read 2535 times:
your question is flight specific and not just a "default" amount. For example most co.s have a historic avg. taxi for every airport and yes the APU is run for engine starting but no fuel amt is really figured as far as I know, never seen it. Rarely if ever do you leave with exactly the req'd amount and I've actually seen fuel added to bring up landing fuel to the co. mins. So your question is really trip specific. Some guys add extra but I almost never add it and I've been low only once and that was a weird set of circumstances.
SKC From United States of America, joined Oct 2012, 60 posts, RR: 0 Reply 2, posted (7 months 1 week 6 days 17 hours ago) and read 2404 times:
Contingency fuel is specifically that...contingencies that you may or may not be aware of. I've been with three different carriers and all three had different contingency fuel policies. So, you can't just say 4% or 25 mins and encompass all possible contingencies.
As Cosmic stated, taxi fuel varies by airport and aircraft type. You'd better plan more taxi fuel for a departure from PHL than you'll need for OKC.
"Extra" fuel is similar to contingency fuel. It differs for every carrier and every scenario. I'm going to plan more extra/hold/cont fuel during the spring thunderstorm season in the midwest than I am during a nice fall day. I'm going to plan more extra/hold fuel when I know AF1 is going to be arriving about the same time as I am into an airport.
On top of company policy, each dispatcher has their own preferences regarding fuel planning. Some are min fuel type guys, others like to carry plenty of extra. Unless it's severe clear, I'm carrying additional gas as it's far cheaper to carry the gas and hold (during wx events) than it is to divert. Not worth it to me.
PGNCS From United States of America, joined Apr 2007, 2516 posts, RR: 45 Reply 3, posted (7 months 1 week 6 days 4 hours ago) and read 2321 times:
Quoting SKC (Reply 2): On top of company policy, each dispatcher has their own preferences regarding fuel planning. Some are min fuel type guys, others like to carry plenty of extra. Unless it's severe clear, I'm carrying additional gas as it's far cheaper to carry the gas and hold (during wx events) than it is to divert. Not worth it to me.
Excellent post, SKC. I wish you could work all my flights!
On our real life 747s contingency is normally less than 3% on ultra long haul flights, you are going past so many good airports enroute, we do not need full contingency for he entire route, we use a reduced contingency, and regularly update the fuel available compared to the plan. If required, a tech stop maybe needed, the company has done the numbers and has the statistical basis, it is cheaper to occasionally do a Tech stop than carry full contingency every flight. Sometime we also refile in flight as well, I.e. plan on a closer destination, and we can "make fuel" enroute by not burning contingency, getting optimum levels etc, and revile to the normal destination.
Taxi fuel for us on the 747 is a standard 1000 kg, I cannot recall any port we currently plan for more than that, JFK may have been a little higher.
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CosmicCruiser From United States of America, joined Feb 2005, 2212 posts, RR: 16 Reply 5, posted (7 months 1 week 5 days 19 hours ago) and read 2258 times:
Quoting SKC (Reply 2): I'm carrying additional gas as it's far cheaper to carry the gas and hold (during wx events) than it is to divert. Not worth it to me.
In that scenerio I would agree that most dispatchers will add some cont. fuel but some guys just want extra fuel just because and that is a waste. You must burn it to carry it. Now that we are a flag/dom carrier it's published how much fuel is saved by not having an alt.
Darksnowynight From United States of America, joined Jan 2012, 980 posts, RR: 1 Reply 6, posted (7 months 1 week 5 days 18 hours ago) and read 2247 times:
Quoting callegro (Thread starter): I know the APU is rarely run anymore do to ground power at the gate, but how many mins are usually in the CFP?
I wouldn't say rarely. In the two-hour+ turns we did for BA at my previous station, the APU stayed on the whole time. Ditto for KLM, CX, QF, and quite a few others. Really, you're only going to see an APU off on RONs or turns greater than five or six hours (when a plane is towed remote anyway; but sometimes --like QF's DFW service, not always then either--).
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SKC From United States of America, joined Oct 2012, 60 posts, RR: 0 Reply 7, posted (7 months 1 week 5 days 14 hours ago) and read 2208 times:
Quoting zeke (Reply 4): On our real life 747s contingency is normally less than 3% on ultra long haul flights, you are going past so many good airports enroute, we do not need full contingency for he entire route, we use a reduced contingency, and regularly update the fuel available compared to the plan. If required, a tech stop maybe needed, the company has done the numbers and has the statistical basis, it is cheaper to occasionally do a Tech stop than carry full contingency every flight.
I agree that this is beneficial on long haul and ultra long haul flights. The majority of things I handle are short to medium range flights of > 4.5 hrs.
Quoting CosmicCruiser (Reply 5): some guys just want extra fuel just because and that is a waste. You must burn it to carry it.
I agree with this as well. I'm only taking the extra when there's a known chance of holding/diverting.
I do not know about the other airlines you mention, at CX we prefer to run external power. Most if not all of our APUs are power by the the hour. If it were not for a tailpipe fire, I do not think we would tart them at all if the local station has decent ground power.
I do not agree with that, I use my judgement for every flight. I am not per-disposed either way. Most of the flight plans I see would burn the planned contingency in a single circuit at our home airport.
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Darksnowynight From United States of America, joined Jan 2012, 980 posts, RR: 1 Reply 9, posted (7 months 1 week 5 days 7 hours ago) and read 2153 times:
Quoting zeke (Reply 8): Most if not all of our APUs are power by the the hour.
Interesting. I think I knew that from somewhere. Anyway, what I see here is a lot of the 744 & 748fs leaving them on here. But then, they're not on the ground very long most of the time.
Have you had a lot of issues w/tailpipe fires? We hear about stuff like that every now and again, but I don't think I've ever seen that one.
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SKC From United States of America, joined Oct 2012, 60 posts, RR: 0 Reply 11, posted (7 months 1 week 4 days 19 hours ago) and read 2074 times:
Quoting zeke (Reply 8): I do not agree with that, I use my judgement for every flight. I am not per-disposed either way. Most of the flight plans I see would burn the planned contingency in a single circuit at our home airport.
Of course, I use judgement on every flight, as does any good dispatcher worth anything. I was referring to additional fuel above and beyond our company mins for contingency fuel (which is above and beyond what is required by the FARs).
Our flight plans include: dep-dest, 1 missed app and go around to land, FAR required fuels, additional fuel based on stage length....THEN at that point the dispatcher has the choice to carry extra contingency fuel. So, when I say that I don't carry extra unless I know there's a chance I'm holding or diverting, you have to realize that I already have a nice cushion built into the plan without me adding to it.
senchingo From Germany, joined Oct 2010, 104 posts, RR: 0 Reply 12, posted (7 months 1 week 4 days 17 hours ago) and read 2058 times:
Quoting zeke (Reply 4): Taxi fuel for us on the 747 is a standard 1000 kg
Same as we take
Quoting SKC (Reply 2): On top of company policy, each dispatcher has their own preferences regarding fuel planning. Some are min fuel type guys, others like to carry plenty of extra. Unless it's severe clear, I'm carrying additional gas as it's far cheaper to carry the gas and hold (during wx events) than it is to divert. Not worth it to me.
If i add up all the flights, the company might not be very happy seeing that all of them carried around and burned unneeded extra fuel. There might be one diversion out of what.... 100 flights? My guess is that this one diversion - which, if the reason is emergency fuel, is extremely rare under normal circumstances - is much cheaper than 100 other flights carrying tons of fuel around.
Of course, if there's such a mess like the Ryanair scenario with 3 flights in the holding for quite a while and a company policy to reduce fuel to the min possible extent, it may happen easily to come to emergency fuel.
Quoting zeke (Reply 2): On our real life 747s contingency is normally less than 3% on ultra long haul flights, you are going past so many good airports enroute, we do not need full contingency for he entire route
Also true, but depending on the route taken of course. Flying i.e. over Syberian Tundra on a ultra long haul, there may not be very much alternates. Therefore, i go a little higher (4-5%).
SKC From United States of America, joined Oct 2012, 60 posts, RR: 0 Reply 13, posted (7 months 1 week 4 days 14 hours ago) and read 2031 times:
Quoting senchingo (Reply 12): If i add up all the flights, the company might not be very happy seeing that all of them carried around and burned unneeded extra fuel. There might be one diversion out of what.... 100 flights? My guess is that this one diversion - which, if the reason is emergency fuel, is extremely rare under normal circumstances - is much cheaper than 100 other flights carrying tons of fuel around.
Except you can't plan to use reserve fuel. Holding isn't typically an emergency, so if you know there's a chance for holding you are required to plan for it.
I'm not suggesting that I load an extra 2 tons of fuel on my flights when the skies are clear and traffic is flowing nicely. I'm only saying that when there is known holding going into BWI due to single runway ops, it would be crazy to not add some extra fuel for contingencies. When my DEN bound flights are arriving mid-afternoon during thunderstorm season, I'm adding extra fuel because even if the thunderstorms aren't in my arrival quadrant, I know that TRACON is going to start moving flights to different STARs thus increasing my enroute time, so I'm adding gas. Will all of my flights hold and/or divert? No, but had those four flights not had that additional fuel, I'd be having to explain why I had 4 diversions when I wasn't weight restricted.
Senchingo From Germany, joined Oct 2010, 104 posts, RR: 0 Reply 14, posted (7 months 1 week 4 days 10 hours ago) and read 1986 times:
Maybe i got you wrong there. To me it sounded like "i'll add extra fuel, come what may" :P
Of course, if known issues are present (holdings, closed runways, severe weather etc) i think everyone will plan more.
On my sectors, there are also known seasons where fuel will automatically be raised (i.e. MUC during winter/snowfall, NRT during rainy/typhoon season).
By the way:
How much taxi fuel do you guys plan if deicing is going on (talking about deicing on the pad, not at the gate like underwing or sth).
Fabo From Slovakia, joined Aug 2005, 1111 posts, RR: 1 Reply 15, posted (7 months 1 week 4 days 7 hours ago) and read 1961 times:
Quoting callegro (Reply 10): I'm curious, how many minutes is 1000Kgs of Taxi fuel for a 747? Is that total taxi or for departure airport and arrival airport?
Makes for about 20 minutes.
You plan taxi fuel for departure airport, and you plan it so that your take-off weight does not include taxi fuel. You might want to re-plan if you eat more than that though, since you might end up illegal on takeoff. (This means, in practice, that taxi fuel usually includes whatever APU fuel usage is. APU fuel planning is one of those flightsimisms that pop up here and there
After you land, worst thing that can happen is that you need to get a towtruck, but your typical minimum legal landing reserve, which you may not tuch without declaring emergency, will get you to your gate and far beyond anyway.
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zeke From Hong Kong, joined Dec 2006, 7725 posts, RR: 73 Reply 16, posted (7 months 1 week 3 days 20 hours ago) and read 1909 times:
Quoting senchingo (Reply 12): Also true, but depending on the route taken of course. Flying i.e. over Syberian Tundra on a ultra long haul, there may not be very much alternates. Therefore, i go a little higher (4-5%).
I do not, that is just my technique. We tend to carry a lot more fuel these days as aircraft have become more efficient and more direct routes have opened up. Back when the classic was the modern aircraft, routes were a lot more convoluted, a lot more procedural control and greater traffic separation. End result, fuel was very tight.
Quoting SKC (Reply 13): Holding isn't typically an emergency, so if you know there's a chance for holding you are required to plan for it.
My take on that is, if it is published in the AIP or NOTAM, I must carry it, otherwise it is personal judgement, and not absolutly required. If I need to divert as the plan does not have additional holding fuel in it, my company accepts this as a commercial decision. Most flights I tend to make fuel.
Quoting Senchingo (Reply 14): How much taxi fuel do you guys plan if deicing is going on (talking about deicing on the pad, not at the gate like underwing or sth).
That really depends on the airport. I find airports that do a lot of de-icing are very good at it, time is negligible. I find it tends to be in the shoulder season or airports that do not see a lot of snow are not as efficient, I sometimes allow for an hours fuel burn, I do not want to end up going back on stand for fuel, and not all ports all refuelling with pax onboard.
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