Comprehensive Guide to Aircraft Fuel Planning and Management

when you're driving a car all you do is fill up the tanks with fuel and drive there's not really that much planning

that has to go into it because the worst thing that happens is you run out of fuel you pull into the side of the road

or you reach another fuel station and top up when you're flying an aircraft though

there aren't many fuel stations floating around in mid-air though so we have to be a little bit more careful with how we

plan our fuel so how do we plan our fuel and how do we decide how much fuel we're going to take on any given Journey

let's find out [Music] hi I'm Grant and welcome to the second

class in the flight planning Series today we're going to be having a look at how to plan and predict our fuel usage

that way when we push back from the stand at the start of the day and get our engines going we know we have the

correct amount of fuel on board in order to conduct our flight safely the fuel we put on an aircraft at the start of the

day at the gate can be broken down into different parts while not physically separated in the fuel tanks it can be

useful to think of these things as different containers of fuel like Jerry cans bottles containers barrels whatever

you think is appropriate for example the taxi fuel is a small bottle of coke that we use to tax out onto the runway we can

then discard the bottle as it is now empty we can then use the trip fuel which is like a barrel of fuel we only

start tapping into once we start the takeoff roll that's just a trick I use to try and think of these fuel is

completely separate and only used in certain situations so whilst they're not physically separate it can be useful to

think of it that way in your head so the breakdown of fuel that we have at the ramp is as follows we've got the taxi

fuel this is pretty straightforward this is the fuel used to taxi out to the runway depending on which Runway it is

uh which runways in use and which airport you're at it might be a small amount if you're somewhere with a Runway

miles away it could turn out to be a lot of fuel this fuel section the taxi section ends

at the start of the takeoff roll down the runway so our total fuel on board our block fuel our ramp fuel minus the

taxi fuel is the fuel we would take off with and that's what our takeoff Fuel and takeoff Mass would be based off of

so we're at the terminal our plane pushes back it gets pushed back by a little tow truck and then we start the

engines and we taxi down to the runway and that's our little period of Taxi fuel there trip fuel is pretty

straightforward this is the fuel required for the trip it's the fuel needed to depart airport a climb Cruise

descend and land at airport B our destination and it takes into account all the routing any weather that we

might have to um that we know about and we could avoid in terms of

um storms or it could be things like headwinds and Tailwinds that we need to think about and we'll also consider the

type of arrival and approach that we're doing into our destination airport the contingency fuel is something that we

use for unforeseen circumstances that could increase the fuel burn on the trip this could be things such as avoiding a

thunderstorm that we don't know about in the planning phase it can also be things um such as increased fuel consumption

due to flying at non-optimal flight levels or different arrival departure runways from expected and different

routing as a result contingency fuel is five percent of the trip fuel but there are a few special

procedures we can use to reduce this amount further which we'll look at after we've covered this breakdown additional

fuel may be added depending on the type of flight if we're operating to a remote Airfield without a destination alternate

for example then we have to add fuel into this alternate section to allow for 50 minutes of holding at 1 500 feet

above the destination eardrum we would also see additional fuel added for something called etops which is extended

twin operations and etops is basically a set of um criteria in terms of Maintenance fuel

planning and in-flight procedures that you have to fulfill in order to fly a twin engine aircraft across large bodies

of water and further away from suitable destination and sorry on Route alternates because the standard is you

fly within one hour of airports and as you would make your way um down a route but if you had four

engines it was a different rule um because you had more engines in case one went wrong you'd still be able to

fly further to reach a suitable alternate that's on route but the etops the extended twin operations

allowed for two engine aircraft to fly further than one hour away from suitable on the alternates and basically because

the engines were seen as more reliable there was more careful planning going into it and etops is not something I've

ever done but it's something you do if you probably cross the Atlantic or cross the Indian Ocean down to Australia or

something like that and but I just know it requires a bit of extra fuel alternate fuel is the fuel we

fly to the alternate with this is the fuel from the missed approach of the destination taking account the full

missed approach procedure and routing then fuel The Climb to a certain altitude cruise for a little bit descend

and conduct an approach at the destination alternate and there's a few extra things about ultimate fuel that

will again touch on in the future we've then got final Reserve fuel this is our absolute Last Resort fuel in a piston

aircraft we take 45 minutes worth of flight time just generic Cruise flight time and in a jet it's 30 minutes worth

of fuel holding at 1 500 feet above the destination

alternate and we use this because generally Jets have a different a significantly

different fuel burn when they're at low altitude compared to high altitude so by using the 1500 feet above

the destination Outlet at a first 30 minutes it's going to be a very different number if we took 30 minutes

of cruise flight time and this is the more realistic situation we're more likely to be holding at a low level than

we are at a high level so by taking 1 500 feet that's probably a bit low in reality you'll probably be holding a bit

higher than that but you still get a more realistic value for our fuel burn that we're going to need in our final

Reserve than if we use the cruise value for a jet the final Reserve fuel is not to be used unless it's an absolute

emergency if you enter into your final Reserve field you are in an emergency situation you need to call Mayday and

you need to land as soon as you possibly can because this is possibly the worst situation is running out of fuel in the

flight that's why we have this final Reserve it's for the absolute worst possible case scenario if you go into it

for anything other than a complete emergency situation then um yeah you're gonna get a call from your

boss and maybe uh ah there's some serious questions extra fuel is anything extra that the captain

wants to add it's the Commander's discretionary fuel this is not a legal requirement like most of the other

component parts but this is just any extra fuel that the captain wants based on intuition and local knowledge say for

instance you knew you were flying to London Heathrow there's quite often a lot of delays going into London Heathrow

because it's a very busy airport your company might factor in that they um expect a 10 minute delay fairly

reasonable but you know that it's you know five o'clock on a Tuesday afternoon and that's when all the big flights

arrives you're gonna have to hold for a bit longer you might think right we'll take an extra minute uh extra 10 minutes

of fuel so we've got a 20 minute holding fuel so the flight plan doesn't leak left to

calculate that holding time for you so this is where you use that and local knowledge that intuition to help you out

and you just take what you need so legally speaking we have to take all those parts but we can do a few little

procedures to edit and change the amounts that we need legally speaking so the first one we're going to look at is

the three percent contingency so basically if we reduce the amount of fuel that we take with us on a flight

then we can take more passengers and cargo with us think about the elements of our all-out mass that we looked at in

the previous class we've got the basic empty mass and that can't really change we've got the variable load which that

can't really change for a certain route we need that amount of crew we need that amount of uh

food in the galleys we need that amount of water in the toilets that kind of thing so the only thing we can really

change are the fuel and the passengers for a certain route ideally we want to take more passengers because passengers

pay for the space and fuel cost us money to burn so if we can take less fuel we can take more

passengers earn a bit more money from the flight we can't just under fill the fuel tanks

though and take too little fuels this would be dangerous and illegal so there are a few procedures we can use to allow

us on the three percent contingency is one of those procedures so the three percent contingency

procedure as you might expect allows us to reduce the contingency from five percent of the

trip fuel to three percent of the trip fuel this is only allowed if there's a

suitable on Route alternate available or an era you might call it if during the flight we see that they

will no longer be enough fuel to land at the destination or a destination alternate with our finals are still

intact then we have this era as an option so the era has to be in a specific location which is within a

circle that is 20 with a radius that is 20 of the total flight distance and the center of that

Circle has to be located 25 percent back from the destination if we look at this picture between Madrid and Amsterdam we

can see that the era would have to be within this circle here which is a 20 radius of The Descendants and is

centered 25 back from Amsterdam and I'm pretty proud of myself on this one because I just guessed two eardrums that

I thought would be or two cities that I thought would be about a thousand nautical miles apart and to make the

maths nice and easy and it turns out the Madrid and Amsterdam straight line is about 980 knuckle miles so that's uh I

don't know that's just a win for me I thought I was quite proud of that anyway you'd have to pick an era which is

within this circle and you might pick one depending on what your company wants so Paris has a few airports it's got

Charles de Gaulle sort of up to the north and it's got orally down to this to the South

say the weather was good for both of them which one would you choose well it

really depends on what your company thinks is best say for instance you had a base at orally but not Charles de

galle it would make way more sense to land orally because then you have

[Music] um all your own staff there you have now

you have extra planes there you might have fueling contracts there all this good stuff you might have your own

handling agents there whereas if you land at Charles de Gaulle your company quickly has to phone up people or you

have phone up people and sort things out which could be a bit messy so for instance on this flight say our company

had a base at orally orally it would be our our on Route alternate option which would allow us to reduce our contingency

three percent saving us a little bit of fuel allowing us to put back more passengers and bags on should we need it

and there's another use for the three percent contingency Fuel and these sort of fuel procedures in general

see if we calculated we were going to be close to our maximum Landing Mass When we arrive at Amsterdam

or our maximum takeoff Mass when we depart then selecting a suitable era3 would allow us to reduce our contingency

down to three percent and bring us back below those maximum structural masses or maximum performance masses so dra3

procedure can be used for a couple things another procedure we can use is the

reduced contingency fuel procedure the reduced efficiency fuel procedure is a way of giving ourselves two options

for our destinations in a way and we use the lower of the contingency fuel values

basically we nominate a suitable on-root alternate that has good weather approaches it's not performance limited

Etc and we non-minate a decision point we then take five percent contingency from the decision point to the

destination or we take five percent five percent contingency from the departure via the

decision point to the enroute alternate and we take the larger of those two values and compare them

so it'll be either five percent contingency for this bit or five percent contingency for this bit

we have to take the larger of the two values but there can be a significant reduction in fuel needed say like this

example our decision point and our era is roughly halfway then we'd only need to take five percent contingency for

half the trip fuel to our destinations which could be quite significant so there's another procedure we can use

that doesn't reduce the contingency but it does mean that we don't have to take

alternate fuel in a way so it's called the predetermined Point procedure and it is basically used when the destination

and the destination alternate are too far apart to fly all the way and fly down to our destination alternate as

well this can happen in really remote airports on remote Islands or even just

remote parts of countries for example Perth in Australia is very far away from any other airports so we might use the

procedure I don't know I've never flown into Perth in Australia um but anyway the procedure entails that

we have a predetermined point along the Route where we make the decision to commit to our destination or

fly to our destination alternate it's a fork in the road where we choose where we're going to commit

the predetermined Point procedure is one where we don't use any alternate fuel because alternate fuel is only used to

fly from the destination to the alternate scenes we're only going to one airport or the other we don't use any

alternate fuel so we're saving a whole bunch of fuel on the alternate but we do have to counteract and cover ourselves

by taking some additional fuel in the form of this predetermined Point procedure basically we have two fuel

values that we have to compare we go from the departure via the predetermined point to the destination

and the departure via the predetermined point to the destination alternate there's two routes and we have to take

fuel for either the departure destination and it depends on

the aircraft we're flying for for a piston for example we take 45 minutes plus 15 of the flight time or two hours

whichever is less we then compare that to the fuel for this route here and then we also take 45 minutes of

additional Fuel and whichever fuel is uh larger we take that one if we were in a jet we would compare the fuel for the

destination sorry departure destination plus two hours of fuel based off of The Cruise fuel burn and versus the

departure to the destination plus 30 minutes of holding fuel of 1 500 feet above the destination alternate and we

take the larger value there you might have noticed that these two values sound familiar because these are

equivalent to our final Reserves so you can think of it as taking two final reserves with you if you go to the

destination alternate or if you go to the destination it's 45 minutes plus 15 or two hours or two hours whichever is

lower so a little example of how we would use one of these alternate fuel procedures as something like this so

given the following information calculate the minimum possible contingency fuel for a commercial

transport flight from A to B with a twin jet aircraft so it's a jet aircraft we're thinking 30 minutes fuel at 1 500

feet above for holding and contingency so we're not looking at the predetermined point we're looking at our

three percent contingency and we're looking at the reduced contingency fuel procedure so we've got a trigger speed

and a headwind uh 450 knots and 50 knots fuel burn is 2000 kilograms on Route fuel burn in the holding is 1 200

kilograms and the aerodrome C is a suitable era and that's halfway between 1 000 mile distance so it's all looking

pretty easy numbers to work out so first thing I'm going to do is I'm going to try the three percent

contingency procedure and the very first step would be just to check that this is within the suitable radius

so we're going to go 25 of the way back so that's going to be there and that's uh going to be 250 naught

miles away from point C and 250 naught miles away from point A

that would be the center of our Circle then we take a circle which is 20 of the distance radius so 20 of this is 200

nautical miles so it's going to look something like that

that's going to be 200 knot miles and we can see that Aerodrome seed does not fall within that Circle so we know

that we can't use the era3 procedure so we're going to be looking at the reduced contingency fuel procedure so we can

assume that we've got a decision point which is in line with Aerodrome C so we're going to either take five percent

contingency fuel for here or five percent contingency fuel to here which is going to be the same number

because this example is nice and friendly to us so

what we're going to have to do is figure out how much fuel we burn on half of the trip and take five percent of that

so few burn onroot 2 000 kilograms an hour so we need to figure out how many hours

we're going to be flying here and we can do that because we've got speed and we've got a distance important to note

though that 0.8 point B will be a distance over the ground and we're looking at true air speed and headwind

so we can work out that we've got a ground speed that is equal to 400 knots because we've got the 50 knot headwind

pushing us back and then speed equals distance over time so that's our speed equals the distance which is 1000 over

the time and we can work out that if we're traveling at 400 nautical miles an hour over a thousand knock miles the

time is going to be two and a half hours that's what it would take fly from A to

B now we need to figure out that our fuel burn is our fuel is good what our fuel burn is going to be it got tripped

over my tongue there so the fuel burn of 2 000 kilograms on Route uh yeah 2000 kilograms an hour on Route 2.5 times

2000 that's going to be 5 000 kilograms we then know that we only have to take five percent of either the

first half the second half well doesn't really matter so we're going to be taking five percent of 2 500 which is

going to equal 125 kilograms so that's our answer we've double checked that it doesn't work for

the era3 and our reduced contingency fuel is either five percent of e via the decision point to c or it's five

percent of C to B and because this is conveniently located halfway it's going to be the same

and five percent of half of the fuel trip burn 125 kilograms nice and easy so to summarize then the fuel that we take

on board can be broken down into different parts we've got the taxi fuel trip fuel contingency alternate

additional final reserve and extra and the way to remember this is taxi trip Cafe with two A's

so taxi very simple gate to Runway trip Runway of e to Runway of B contingency is five percent of this fuel

value for a trip or three percent if we've got a suitable on Route alternate within a 20 distance Circle 25 of the

way back or the contingency is five percent of not the total trip but just the portion

from the decision point to the alternate or the on Route alternate or the decision point to destination alternate

fuel is the fuel from the destination to our destination alternate including all the missed approach the arrival the

approach into the destination alternate and Landing there additional fuel is taken for something

like the predetermined Point procedure this procedure specifies that we pick a point where we create a fork in the road

we either go to destination or we go to the destination alternate if we go to the destination alternate we take an

extra set of final Reserve fuel so in the propeller that's another 45 minutes on top of our final Reserve Fuel and in

a jet that's 30 minutes of holding at 1 500 feet above the destination alternate if we go on to our destination we take

fuel for the trip plus an additional 45 minutes of fuel plus 15 of the trip fuel that we used or two hours worth of

fuel whichever is more and Bridgette is just a flat two hours worth of fuel final Reserve fuel I just mentioned it's

45 minutes for a propeller and 30 minutes of holding fuel 1500 feet above the destination alternate

and we don't want to go into that unless it's an absolute emergency if you even touch it you are in an emergency

situation by definition extra fuel this is Commander's discretion fuel on the day using local

knowledge local information intuition what you'd expect to see if you had a slot like an air traffic control

restriction you can't depart for two hours for instance but you want to run the Apu the auxiliary power unit that's

in the tail of the aircraft to give the plane some air conditioning you might add a little bit of extra fuel on here

just to help cover that before you even start the engines and start burning this other fuel

foreign