Fuel calculations

[Paul_Smith 92]

Thanks. I get it now!Only one more question.Do you always calculate reserve fuel using the alternate diversion route from your destination to your alternate?What happens if before reaching you primary, somehow you reach your reserves value and alternate airport is farther than primary? what should you do? Declare an emergency and land at the nearest suitable airport?

As Ryan said, the reserves are what you plan to get you from the primary to the alternate after holds and go-arounds. If you are using reserves before you have even reached primary, you have either a serious miscalculation or a fuel leak. Either way, your plan is out the window, time to get out of the air. That said, you should not declare an emergancy unless one actually exists, and having to change your plans is not an emergancy in itself.

[prdant 2]

Interesting. I use FSBuild, and this is what it gives me:EHAM LOPI1S LOPIK UN852 LUTOM N852 LNO UN852 PELIX UZ210 KRH UM150 LAMGO UZ210 TGO UL607 BEMKI ADILO LOWIDIST 0419Mach 78FL370AVG WIND -40 kts (headwind)(fuel type) (amount) (time)TAXI 000375 0015DEST LOWI 007754 0109RESV 003741 0045ALTN 001309 0015HOLD 000000 0000EXTRA 000000 0000TTL AT TO 011495 0154REQD 011870 0209It looks like your total fuel is 12964 vs mine which is 11870. A difference of 1094 lbs. Not much really.My reserves are usually 3.7, which I put into the PERF page, and I always end up about 2-3,000 lbs above my reserve mark.Everything is accounted for except 2 missed approaches but the extra fuel I have besides the 45 min hold and the alternate is enough for those 2 missed.

While JetPlanner is a real world flight planner, there are more than likely differences in the aircraft, routing and weather that could account for the differences. I grabbed a generic 737-800W but I see my opwt is 82000 which I believe differs from the PMDG version. I will play around tomorrow or over the weekend and tweak my aircraft to match the specs of the PMDG aircraft and see what I get. Need to try to compare apples to apples.

[Kerlix 99]

I use vroute premium and it seems to be pretty accurate for me. does anyone know if the calculations are generally "off"? which would mean i really don't know ANYTHING. which i guess is quite possible...

[ajpongress 467]

I use vroute premium and it seems to be pretty accurate for me. does anyone know if the calculations are generally "off"? which would mean i really don't know ANYTHING. which i guess is quite possible...

Never used vroute so I wouldn't know. I've only used FSBuild.

[EdubFlyer 2]

I think there's some confusion here over what the reserves amount you enter into the FMC really is - sorry if I didn't make this clear enough in the tutorial:Reserves is not the value you're planning to land with and it's not the minimum amount you can have in your tanks. It's a variable amount of fuel depending on the specific flight in question that represents the point at which you are legally forced to divert to your alternate. If for any reason during a flight you reach your reserves value, you MUST divert because if you continued on to your original destination **you no longer have the fuel to make it to your alternate** while complying with the legal limits. If you got to LOWI and did two go-arounds or something like that and then got the USING RSV FUEL message, you HAVE to divert to EDDM even if you think you still have enough fuel to try again at LOWI. If you fail on the third attempt you now can't make it to Munich (legally at least) and you're going to be in a ton of hot water with your airline and the government regulators.

Ryan is this the same way in the U.S.(i.e. fuel planning regulations) ? Do all airlines load that much fuel into the tanks ? Is there any difference between airline policy in fuel loading?I notice via flightaware.com that most airlines generally use the same routes between cities. Although one thing I find interesting is that the flight plan altitude policy appears to be different between carriers for the same airframe. Maybee it's just me, but Alaska seems to pick lower inital cruise altitudes with possible step climbs, while SWA will fly high as possible. I'm sure winds and CI have an impact.Any RW pilots can chime in....Eric W

[EdubFlyer 2]

Just found an interesting article on this subject. http://articles.latimes.com/2010/jul/13/business/la-fi-airlines-fuel-20100713It mentions an FAA regulation of 45 minutes of reserve for domestic flights. AA says they are landing with an average of 93. would a domestic carrier flying from say NY to Miami actually make a flight plan with an alternate when there are many airports on the way and in the vicinity?Eric W

[Paul_Smith 92]

... would a domestic carrier flying from say NY to Miami actually make a flight plan with an alternate when there are many airports on the way and in the vicinity?Eric W

I would hope so. If you have spent 30 minutes holding for Miami and still can't get in, it is probably weather related, which means all other nearby fields will also be closed.

[realpilotsimpilot 11]

Just found an interesting article on this subject. http://articles.lati...s-fuel-20100713It mentions an FAA regulation of 45 minutes of reserve for domestic flights. AA says they are landing with an average of 93. would a domestic carrier flying from say NY to Miami actually make a flight plan with an alternate when there are many airports on the way and in the vicinity?Eric W

Yes, there's the so-called "1-2-3 Rule" which specifies when they need to have an alternate. Many/most times you don't. In terms of how much fuel you need, what you're really talking about is flying to Miami, shooting the approach at least once, then dverting to the alternate. If the airport is closed before they get there for some reason, they could very well land early, but think how rarely that happens.And, regardless of the 1-2-3 Rule there's good reasons to carry extra fuel. Unforecasted delay, weather that doesn't meet the rule, but prohibits landing (think wind or sudden thunderstorm, as examples) are reasons. A friend was recently diverted from LAS to PHX because of high wind. Clear day, heavy desert wind. So, they sat on the ground at Phoenix until the wind calmed down. That's a about 30ish minutes flight time? Cutting it mighty close if you had 45 minutes and no alternate planned. Fuel in the truck is not worth very much.

[Spin737 102]

 

Maybee it's just me, but Alaska seems to pick lower inital cruise altitudes with possible step climbs, while SWA will fly high as possible. I'm sure winds and CI have an impact.Any RW pilots can chime in....Eric W

I'm not sure that we do anything different. Alaska does quite a bit of E-W routes so we might be going up and down for favorable winds.

[Spin737 102]

Reserves is not the value you're planning to land with and it's not the minimum amount you can have in your tanks. It's a variable amount of fuel depending on the specific flight in question that represents the point at which you are legally forced to divert to your alternate. If for any reason during a flight you reach your reserves value, you MUST divert because if you continued on to your original destination **you no longer have the fuel to make it to your alternate** while complying with the legal limits.

You're talking ICAO/JAR here, I'm assuming. When people start putting all this info it, it probably helps if we try to also identify where we are or who the governing body is.In the US, reserve is reserve: 45 minutes for domestic. There is no legal requirement to have that when you land. You must have it when you take off, but after that, you can use it. Also, there is no MUST divert language in the FARs (at least not that I've found).All that said, if in the PERF INIT put in your HOLD/EMER+ALT fuel or in the US your RES+ALT in the RES line, you can easily be warned of a good bingo fuel.Everybody is talking apples and oranges.

[sherab 0]

I think there's some confusion here over what the reserves amount you enter into the FMC really is - sorry if I didn't make this clear enough in the tutorial:

 

Reserves is not the value you're planning to land with and it's not the minimum amount you can have in your tanks. It's a variable amount of fuel depending on the specific flight in question that represents the point at which you are legally forced to divert to your alternate. If for any reason during a flight you reach your reserves value, you MUST divert because if you continued on to your original destination **you no longer have the fuel to make it to your alternate** while complying with the legal limits. If you got to LOWI and did two go-arounds or something like that and then got the USING RSV FUEL message, you HAVE to divert to EDDM even if you think you still have enough fuel to try again at LOWI. If you fail on the third attempt you now can't make it to Munich (legally at least) and you're going to be in a ton of hot water with your airline and the government regulators.

Thank you Ryan for this info - it's very helpful for me.

Reserves is "...a variable amount of fuel depending on the specific flight in question that represents the point at which you are legally forced to divert to your alternate".

If I understand right it's not a percentage of trip fuel.

 

Can someone help me out and make it explicit how I calculate it?

 

I guess:

Reserves = Alternate 1 + Alternate 2 + Holding + Contingency Alternates + ???

 

Antonio

[Fabo 213]

The process is well explained in Tutorial 2.

[rmusick 1]

Here's another vote for NGCalc for an iPhone or iPad. Great application and very accurate.

[sherab 0]

I am looking for Fuel Tables for the NGX because I want to plan the fuel myself. I am not looking for a fuel planner, not FSBuild, not vroute, not TOPCAT, not the NGX FMC, or another software.

I am looking for the Fuel Consumption Data that someone must have somewhere if such software was compiled.

I am not looking for the Tutorial 2 either because that uses the FMC as the basis and offers me a general rule of thumb. I am looking for the source of that data the Tutorial was based on.

 

Does anyone have any data, fuel tables, graphs or numbers, so I can make the fuel calculations myself? Old style pen and paper method, mileage, winds, and so on.

 

Many thanks,

 

Antonio

[kittyatyi 3]

http://avsimrus.com/f/documents-16/737-700-800-flight-planning-and-performance-manual-28390.html