Solved Taxi Fuel

[m695827 1]

I have a stupid question:

In loadsheet manager, I put the temp, wind, cruise alt,etc. But I never touch the taxi time. Does this affect somehow the fuel remaining on board? I mean, sometimes I can taxi 2 minutes, sometimes 10 or 12 minutes depending of the gate. Of course the burning fuel on taxi is not the same. But how the manager know how much fuel for taxi I need, or how do I know how much time I burn fuel on the taxi. It depend even by the AI number of aircraft I have in front of me for takeoff. I mean I put let say a 5 min. Time for taxi, because my gate is half mile from rwy. But I have 5 aircraft in front of me for take off, so my time became 20 or 30 min. Do I risk to have low fuel msg? Or to avoid I have to put from the beginning an approximate time, just in case?

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[Andy320 77]

For my fuel calculations I use Simbrief, one thing iv noticed is that Simbrief will give you the same taxi fuel for time for the A321-A318 and doesn't vary with weight unfortunately. For flight sim taxi fuel predictions comes with experience, I commonly fly out of EGLL, EGKK and occasionally EGLC, so they are my reference aerodromes. For EGLL I always set the taxi time to 24 minutes which is approx 239kg of fuel which includes my 20 minutes APU fuel (Terminal 5A to runway 27L with 65% AI traffic). From when my APU is switched on to my holding point I usually burn roughly 200kg with idle power after turns (this will vary). For EGLC When taking off from runway 09 I set the taxi time to 15 minutes for shorter taxi distances. I can't recall from 100s of flights ever taxiing into contingency fuel.

[Andy320 77]

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[m695827 1]

So you approximately put always for 25-30 min fuel for taxi? I don't use simbrief.

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[Andy320 77]

1 hour ago, m695827 said:

But I have 5 aircraft in front of me for take off, so my time became 20 or 30 min. Do I risk to have low fuel msg? 

 

This is why you have contingency fuel for any unforeseen circumstances, before you take off you must know the minimum fuel you can depart with. For example in the screenshot of my briefing I could depart with 4705 tanks- 239 taxi- 590 contigancy= 3876kg at take off. In reality you probably wouldn't want to take off using all of your contingency fuel but it can be eaten into or part of it if needed. 

[Andy320 77]

4 minutes ago, m695827 said:

So you approximately put always for 25-30 min fuel for taxi? I don't use simbrief.

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The aerosoft fuel planner predicts too much taxi fuel and fuel in general which isn't vary commercial, it's brilliant to get you going but if you want to practice being fuel efficient then a more accurate fuel planner is needed. From my experience flying the aerosoft buses i would say don't load more than 250kg for taxi and no more than 50kg for APU (to keep it light load 200 taxi and 50kg APU), I know you asked for a time but I think the aerosoft fuel planner almost doubles the fuel for time which is why I'm telling you in reference to KG rather than time (24 minutes approx 239 kg).

[m695827 1]

OK. Thanks, I also fly most in Europe, but sometimes I've made LFPG to HECA (SDG scenery) and at Cairo is a long way from rwy to a gate, and temperature is almost always high, so the burning fuel is a lot. Just one thing: the kg for taxi include both airport departure and arrival?

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[The Dude 6537]

We use 200kg taxi fuel in RL and for airports that are known for longer taxi times (EGLL and LEMD for example) 300 kg seems to be the golden standard. Contingency fuel does the rest if we have an unusual long taxi time. Stuff like APU burn does not count as the APU goes off with the after start items. If you do single engine taxi out with APU on your fuel burn would be even lower than with 2 engines and APU off. 

[m695827 1]

Is it safe to do a single engine taxi? I read somewhere that a lot of companies do this procedure to save fuel, but the safety rules on some airports not aloud this procedure.

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[Andy320 77]

For taxi in fuel it's unlikely you will have any traffic during taxi so again 200kg wouldn't be bad, if you are going to arrive early be prepared to wait for your assigned gate (happens at Heathrow T5 quite often but shouldn't be an issue in the sim), again like a lot of airlines owning A320 type aircrafts you can do a single engine taxi after 2 minutes cooling to reduce the fuel burn, if I'm not mistaken as long as you have fuel whether that's remaining contingency or holding fuel you can taxi with that but don't plan to taxi with that during fuel planning.

 

Also the aerosoft checklist isn't compatible with single engine taxi before and after start checks as both engines need to be started, I believe it's engine 1 that needs to be started for single engine taxi followed by switching on the yellow electric hydraulic pump which I believe is recommended by Airbus if one wants to performe such a procedure. The checklist flow that aerosoft use (standard start) requires engine 2 to be started first or else it won't continue.

[Andy320 77]

34 minutes ago, m695827 said:

Is it safe to do a single engine taxi? 

 

This will depend on the surface conditions of the taxiway, the time to taxi to the holding point, etc

[skelsey 103]

Taxi fuel, strictly speaking, includes fuel for engine start, taxi to the active runway and APU burn before departure if significant (if you're only running the APU for a couple of minutes prior to engine start, as is standard at most airfields and with most operators, the fuel burn will be negligible but if you're keeping it running throughout a long turnaround it will be -- the A320 APU burns around 130kg/hr and the main thing is that there's no point loading 200kg for your taxi out if you burn 130kg through the APU before you push back). Taxi fuel will is not (measurably) affected by aircraft weight and different operators will have different policies -- some may load a standard figure, others may have collected statistical data for taxi times at different airfields and will load fuel accordingly which could result in some fairly significant savings across a large fleet. Either way, the taxi fuel burn is around 8kg/min for the A320 with IAE engines, so just estimate your taxi-out time and work from there.

 

As mentioned, contingency fuel is there to take in to account unplanned delays (though use some common sense -- there's no point loading 10 mins of taxi fuel at JFK in peak time if you know you're going to be crawling around the airfield for 40 minutes or more!) -- also bear in mind that you can only use it once and you might just want it en-route...

 

Fuel for the taxi in is not taken in to account, because it's insignificant. The fuel plan is to ensure that you land (touch down) with at least the minimum 30 minute final reserve in your tanks. Once you have touched down, it becomes irrelevant -- you can burn every last drop in the tanks during the taxi in if you want. So when you are constructing the plan, you are working back from the moment of touchdown.

 

Single-engine taxi is perfectly safe, approved by Airbus and SOP at quite a few operators (especially taxiing in, and increasingly taxiing out). However, remember that the engines have minimum warm-up times which must be respected (so you will need to plan when you start the second engine on taxi out and if you have a short taxi it may not be worth the hassle), bear in mind any steep gradients and think about which engine you start first (which hydraulic system powers your brakes & steering...?). Some airfields also have a requirement that both engines must be running when crossing an active runway etc.