I am currently working on a fuel burn analysis of a particular route (ATL to DCA). I really want to predict takeoff weight of the flight; however, I realized that it's not easy to get the information. Instead, I may want to gather information about minimum fuel requirement for the flight.

For example, I heard from the pilot of the flight that they should have more fuel (20,000lbs) than the minimum fuel (15,000lbs) before takeoff. Could anyone please let me know where I can get this information such as minimum fuel requirement for A320 from ATL to DCA?

Everyday is different, so there is no “minimum” fuel. Winds, taxi out and in time allowances, weather at destination and alternates(s), ATC delays, tankering, performance all play into the minimum and maximum fuel for any leg.

What are you trying to accomplish?

GF

Pre-dispatch, fuel is generally divided thus, the total being "block fuel":
- Taxi fuel. From gate to take-off.
- Trip fuel. From take-off to landing.
- Contingency fuel. For unexpected delays, longer routings than expected, etc. This is traditionally 5% of trip fuel but on long haul is likely to be a much smaller number based on performance statistics and availability of en route alternates.
- Alternate fuel. From the missed approach point at the destination to landing at the alternate. Some airlines don't carry alternate fuel on most routes, and some routes are flown with "island reserve" and no alternate, thus no alternate fuel.
- Reserve fuel. Half an hour of final reserve. Alternate + Reserve make up "minimum divert fuel".
- Rec extra. Not legally required, this is extra fuel based on experience or company policy, for example if you expect holding. Any tankered fuel is included here.

Taxi, trip, contingency, alternate (if required), and reserve make up "Fuel Required", which is the legal minimum. If the pilot said they carried 20000lb and the legal minimum was 15000lb, that sounds as if they carried 5000lb rec extra for tankering and/or expected delays.

Fuel burn analysis is tricky because varying weights give wildly varying fuel burn. On a 3 hour sector, a variation in zero fuel weight of a ton might mean 50kg difference in burn. If daily weight variation is in the 10 ton range, well, you can do the maths.

Just to add, the FAA final reserve is 45 minutes at 10,000’ at “normal cruising speed” vs. 30 minutes at holding speed. Domestic ops doesn’t require the contingency fuel.


GF

GalaxyFlyer wrote:

Just to add, the FAA final reserve is 45 minutes at 10,000’ at “normal cruising speed” vs. 30 minutes at holding speed. Domestic ops doesn’t require the contingency fuel.


GF

Thx for info. I was not aware of this "within the 48 states" fuel regulation. https://www.law.cornell.edu/cfr/text/14/121.639

To be specific about ICAO final reserve for commercial flights, it is 30 minutes holding at 1500ft above aerodrome level for jets, and 45 minutes at normal cruising altitude for reciprocrating engines. Can also be "Island Reserve Fuel" for isolated airports, which replaces contingency and alternate with 2 hours holding at normal cruise consumption.

Island holding is the same here.

GF

sillykim wrote:

I am currently working on a fuel burn analysis of a particular route (ATL to DCA). I really want to predict takeoff weight of the flight; however, I realized that it's not easy to get the information. Instead, I may want to gather information about minimum fuel requirement for the flight.

For example, I heard from the pilot of the flight that they should have more fuel (20,000lbs) than the minimum fuel (15,000lbs) before takeoff. Could anyone please let me know where I can get this information such as minimum fuel requirement for A320 from ATL to DCA?

You appear to be talking about minimum landing fuel, which may be aircraft-specific, or it may be company specific, and many operators also allow captain's discretionary fuel, typically in the order of an additional 5,000 lbs if the captain feels it's necessary. This is not universal, and it does change, even for a company, operation, or the individual captain.

I'd want to know why, if you don't know anything about fuel requirements, you're working on a fuel burn analysis for a particular route. Normally someone who does that is intimately familiar with the requirements for the aircraft, regulation, and for the operation in question. How is it that you're doing a "fuel burn analysis," but don't know anything about the requirements for the fuel?

GalaxyFlyer wrote:

Everyday is different, so there is no “minimum” fuel. Winds, taxi out and in time allowances, weather at destination and alternates(s), ATC delays, tankering, performance all play into the minimum and maximum fuel for any leg.

What are you trying to accomplish?

GF

Thanks for your information! I am now trying to predict takeoff weight of the particular route with the particular aircraft. Since it is difficult to get the information, I may want to know block fuel as the first step.

That's what you said the first time. Normally when someone wants to do an analysis, fuel analysis, runway analysis, etc, they already understand the basics, and it sounds like you don't. If one is calculating fuel for a leg, one should know the very basics of that subject. Likewise, takeoff weight...very basic information.

Any time someone wants to jump to the middle of something without having a basic understanding or purpose, it raises concerns...much like someone walking into a simulator training center and saying they just want to learn to drive, but don't care about learning how to land. Do you understand what I'm saying?

What is the purpose here? The question is why you're doing this analysis in the first place without understanding any of the work that goes into it.

Yes, block fuel is needed, but not enough information is provided. You'll need the fuel for the leg. To get that you'll need a weight estimate and temperatures aloft, fuel to taxi, climb, cruise, descend, fly the approach, and taxi in. You'll need fuel to the alternate, and depending on the leg and rules under which it's operated, holding time or time beyond the alternate. You'll also need to know the minimum for the operator; the operator may say that no aircraft in that particular fleet will land with less than 15,000 on board, for example. If ballast fuel is to be carried, that will be in addition to other fuel, and can't be burned. To understand ballast fuel, you'll need to know the weight and balance of the aircraft and it's load, and with that added, you'll need to recalculate for the trip fuel again.

You'll also need to look at takeoff and landing performance, obstacles, and "second segment" climb performance; these will determine what weight you can take off with, and landing limitations will determine the maximum takeoff weight as well: you've got to be light enough, considering planned fuel burn, to land at the destination, and if this is an airline operation, within 60% of the selected runway at the destination, given winds and weather forecast, as well as applicable notices to airmen, approach availbility, etc.

Note that planned fuel is not the same as required landing fuel; two separate issues.

Your takeoff weight will be impacted by runway availability, accelerate-go and accelerate-stop or balanced field criteria. Your takeoff weight is limited by takeoff distance, temperature, field/runway conditions, obstacles, wind and weather, etc. You've got to work within that takeoff weight limitation to determine what your balance is going to be between cargo/passengers and fuel.

Is this for a flight simulation game, or something else?

I'll add to the above:

You say you want to predict the fuel load for a specific flight. So suppose we give you all the variables etc and you make a prediction. How will you validate you prediction? If you don't have access to these numbers in the first place, chances are you won't have access to the validation numbers.

Which still leaves us wondering what you are trying to accomplish?

The Part 121 passenger and cargo FAR for minimum takeoff fuel is trip fuel burn plus 45 minutes reserve plus alternate fuel if required. There is also a regulation for additional fuel to account for wind and traffic delays but this is not a defined number or time which leaves it up to the dispatcher and captain's discretion.

Many domestic airlines include contingency/hold fuel in the minimum takeoff fuel. However, the hold and contingency is frequently reduced or dropped from the minimum takeoff fuel if a long taxi out means more taxi burn than planned or a re-route is given by ATC. Even the alternate fuel requirements can be and often are deleted if conditions changed since the release was sent out that made the alternate no longer required. It is known in the business as moving fuel around.

Short to medium flights like ATL to DCA should have fairly consistent fuel loads and planned enroute burns. With load factors 80-90% range, weight should be fairly consistent unless there is a one off day with unusually high/low pax, bag or freight numbers. OEWs will generally be in a similar range with each aircraft type. ATC normally requires a certain routing and sometimes even altitude unless they publish otherwise. Most days they will be flying the ATC preferred routing. Winds will have some effect but on shorter routes not quite as much as longer. Where you can often see the big difference will be in your long haul flying. The longer the flight, the more options you generally have as ATC doesn't often restrict you to just one routing. Even a restrictive country like China offers several entry/exit points for long haul flights to play the wind game.

I've never been offered multiple entry and exit points in China for the "wind game." I have a routing to fly and they're not likely to vary it, other than their ridiculously inefficient 90-degree off-course vectors for traffic around Beijing. Wind is addressed with altitude, and working in China or crossing China, altitude isn't very flexible, either; it's usually flown at optimum, regardless.

Alternate fuel isn't discretionary. I'm not sure how one can say that contingency fuel is regulatory, but that it's entirely discretionary at the same time. That makes no sense. I've never seen a case in which holding fuel or contingency fuel is "dropped" due to a long taxi. I've returned to get more fuel, following a long taxi, but if conditions are such that one needs the extra fuel, then it's poor judgment to blow it off thanks to a higher taxi burn. If the fuel is needed, it's needed, and the most useless fuel in aviation is what's been left behind.

I don't believe I've ever seen alternate fuel deleted.

Planning fuel is planning fuel; fuel use enroute is another matter. Just the same as one must be able to land within 60% of the destination runway for planning and dispatch purposes, one can use all of it on actual landing. Certainly enroute one may end up landing with less fuel than planned, or may bite into reserve fuel flying a second approach; the reserve requirements are for planning the flight. Executing it is another matter. Still, I don't believe I've ever seen reserve fuel deleted enroute.

In fact, there are many different fuel and reserve requirements for 121 operations beyond the simple domestic fuel burn to destination plus time to reserve plus 45 minutes holding. Among those other types of fuel reserve arrangements are international fuel (which includes 10% of the class II nav time, etc), and a re-release which reduces the enroute 10% to effectively half-that, but requires the crew to re-calculate when approaching the re-release point and still have that reserve, plus the destination and alternate reserve, in order to continue. It does become more complex than simply doing domestic USA numbers, and that depends on the operator, not simply the location of the operation, and the operations specifications and company policies under which they're operating. The flight release will spell out exactly which criteria, opspec, and regulation under which the flight is operating, and the fuel breakdown on the flight release will show the work itemized as to exactly how the fuel total is derived.

The long haul flights often have less flexibility for deviation, as the fuel load is already maxed out for the payload, and there's not. lot of wiggle room for creative deviation. In any case, ATC generally puts the aircraft where ATC wants the aircraft, which is not necessarily what was planned or filed, and sometimes not what was cleared.

SAAFNAV wrote:

I'll add to the above:

You say you want to predict the fuel load for a specific flight. So suppose we give you all the variables etc and you make a prediction. How will you validate you prediction? If you don't have access to these numbers in the first place, chances are you won't have access to the validation numbers.

Which still leaves us wondering what you are trying to accomplish?

Maybe, somebodies cat has Internet access and is a terrorist. If you are an actual carrier, your flight manual will calculate and validate any of the numbers the OP is curious about. Kinda like ah, no. I just need training for take off. I do not care about procedures for landing an aircraft...............

stratclub wrote:

SAAFNAV wrote:

I'll add to the above:

You say you want to predict the fuel load for a specific flight. So suppose we give you all the variables etc and you make a prediction. How will you validate you prediction? If you don't have access to these numbers in the first place, chances are you won't have access to the validation numbers.

Which still leaves us wondering what you are trying to accomplish?

Maybe, somebodies cat has Internet access and is a terrorist. If you are an actual carrier, your flight manual will calculate and validate any of the numbers the OP is curious about. Kinda like ah, no. I just need training for take off. I do not care about procedures for landing an aircraft...............

I must admit your reply has me scratching my head.
To be clear, I never implied any nefarious intent by OP, my point is, that if you are a hobbyist, trying to 'guess' or predict take-off weights/fuel loads, without understanding what goes into it, you might as well guess the weight of the moon and it wouldn't really matter to you if you can't validate it. And if you were able to validate it, you probably didn't need to guess it in the first place.

I flew this city pair recently. Here’s the numbers from my flight. You couldn’t possibly do anything harmful with this info but this is real world for a 737.

Burnout for a 700 at 390 was 6.2
Alternate fuel was ORF 3.0
FAR reserve of 46 minutes 3.3
Contingency fuel 25 minutes 1.8
Dispatch gave us an extra 30 minutes because of wind and turbulence avoidance 2.2

Min takeoff fuel then 16.5

We boarded 800 lb for taxi out in Atlanta. So total fuel load 17.3. Not even half tank.

So... the plane weighs 85.4 empty.

I have to observe a few limits... Max structural weight 154.5, max landing weight plus burn, today, 134.2... there’s also obstacle climb and zero fuel weight limits but they aren’t a factor. My limiting weight that day was 134.2, and this is often the limiting weight- max landing weight. So, I have room for quite a bit of payload. That said, 143 people weigh less than 29,000 lb and their bags won’t be more than a few thousand above that so there’s lots of room for everyone, their bags, any cargo and be way under any limits.

We don’t arbitrarily board fuel. It’s all calculated to the minute in terms of burnout and we will only take what we need. Today I have to have 16.5 to begin the takeoff roll and 17.3 to leave the gate. Fueled might give us a hundred more perhaps, rounding error. But if the fuel slip says 17.3 we pretty much get exactly that.

All good information and while flight plans are built to suit the operator with regulatory approvals in place, one needs to recall that one size does not fit all. Different operators will design their flight plans accordingly.

Missing from this discussion is the ETOPS factor where the possibility exists for additional fuel to cover APU usage along with diversion fuel beyond the 2nd or 3rd ETP when building the Critical Fuel Scenario.

SAAFNAV wrote:

stratclub wrote:

SAAFNAV wrote:

I'll add to the above:

You say you want to predict the fuel load for a specific flight. So suppose we give you all the variables etc and you make a prediction. How will you validate you prediction? If you don't have access to these numbers in the first place, chances are you won't have access to the validation numbers.

Which still leaves us wondering what you are trying to accomplish?

Maybe, somebodies cat has Internet access and is a terrorist. If you are an actual carrier, your flight manual will calculate and validate any of the numbers the OP is curious about. Kinda like ah, no. I just need training for take off. I do not care about procedures for landing an aircraft...............

I must admit your reply has me scratching my head.
To be clear, I never implied any nefarious intent by OP, my point is, that if you are a hobbyist, trying to 'guess' or predict take-off weights/fuel loads, without understanding what goes into it, you might as well guess the weight of the moon and it wouldn't really matter to you if you can't validate it. And if you were able to validate it, you probably didn't need to guess it in the first place.

Sorry. My point is that all of this stuff is readily available if you study the type certificate of any specific aircraft type and study the FAA regulations about aircraft fuel requirements. Unless you are planning to turn a large fortune into small fortune by starting an airlines, I don't see how knowing fuel minimums would be useful to anybody.

He was asking about ATL-DCA. There is no ocean between those two points.

Redbellyguppy wrote:

He was asking about ATL-DCA. There is no ocean between those two points.

The scope of the discussion had expanded. Thanks:)