Hi!
I was just wondering if you always remove fuel after landing?

Say for an example that your landing fuel would be 3.5T, will it be removed before the next flight or will it remain in the tanks?

So if you need, say 17T for this specific flight, do you only refuel 13.5T or do you take 17T from the beginning?

Thanks!

Fuel is not removed.

what would be the point in removing it? Do you remove fuel from you car when you get home from the shop?

The only routine requirement for defuelling is maintenance. For example, scheduled fuel tank maintenance or an aircraft reweigh are the two most likely situations I can bring to mind.

Where such maintenance is programmed, flight crews would be requested to RTB with minimum fuel. For some aircraft, offloading fuel is a considerable nuisance.

concur, not only is it a nuisance offloading,
in most places, the fuel cannot be re-loaded onto another ac....so a special truck must offload it and it must go back to the fuel farm and set through the filtration system....

FlightPathOBN,

I have never heard of a fuel farm accepting "used" / contaminated fuel into its system...?! :confused:
After all, the fuel has to be considered "out of specification". Or do I miss something?

In my experience, fuel removed from an aircraft goes either back into the same airplane (after weighing or tank entry accomplished), into an airplane of the same operator - or to a power plant...

Cheers, J. V.

Sometimes, even during maintenance work the fuel isn't removed, merely pumped to another tank whilst on the ground.

Horgy

Well, I did say if.....
once if off the aircraft, it is not going into another aircraft untreated.

There are many facilities that have above ground storage tanks, that are even filled by trucks, so there is a filtration system to handle green fuel.

Even so, there is little spec difference between jet fuel and kerosene heating oil for a home....except the cost, and filtration and water content on delivery...

If you dont think that is true, there are lengthy discussion about this on this website...
here we go...

According to Conoco Philips....

Product Name: Aviation Kerosene
Synonyms: Aviation Jet Fuel A-1 (civilian)
...............Avtur
...............NATO F34, F35 (military)
...............Regular Burning Oil (RBO)
...............28 Second Heating Oil
Safety Data Sheet Number: 814650
Intended Use: Aviation Turbine Fuel
Manufacturer: ConocoPhillips Ltd, Humber Refinery
South Killingholme, North Lincolnshire DN40 3DW

http://apollofuels.co.uk/p7spepper/img/kero_msds.pdf

Where I work, fuel that is removed from an aircraft can only be re-used within the same airline. If airline procedures do not permit 'recycled' fuel, it's trucked off to wherever and discarded.

It still must go through a filtration system either on offload or pre-load, never straight...

I hope that with the price of fuel, you dont really think it gets "'disposed of"

one man's disposal is another man's fuel.

dont kid yourselves....

My question is, why would one even consider offloading fuel at the end of a day's flying?

He's only 17, be nice.

Fuel is not removed. No need to top off overnight like in a 172 either.

FlightPathOBN,

In my point of view (mechanical) filtration is not enough, as per legal aspects.

Thank you for the link to A1, not much new things there.... :ok:

What you pump out of an aircraft tank (especially long range airplanes) is a wild mixture of Jet A, Jet A1, TS-1; there is an unknown part of microbial contaminants like yeast, fungus etc., sand, water, hydraulic fluid, left-overs of previous tank entries - well, just about anything...

The bottom line:
In MY aviation world, we can only bring material to an aircraft with proper documentation about what the stuff is (Form 1s, Conformity Statements etc.).
Any fuel that has gone through an aircraft tank is per default not in line with any of the AFM approved fuel specifications and therefore out of the game (with the exceptions given in my previous post).

Good night everyone,
J.V.

On the recent BBC programme about the full maintenance job on a B747 it showed the presenter and a technician inside a fuel tank without breathing apparatus. I was surprised at this, as even if the tank was emptied it would have a lot of residue left in. (I have a little knowledge of this from driving road tankers around delivering kerosene many years ago).

The tank being filmed looked very clean and dry.

Was this 'set up' do you think, or genuine?

I can't comment on current H&S legislation, but I've crawled into plenty of tanks in my time with nothing more than a socket spanner and a wander light.

The tanks would have been inerted with carbon dioxide before entry...

There should not be any residue, as the fuel and slosh would keep the interior very clean...

There will be a problem with biofuel, if you ever use it, it is very clean, and will flush out all the intake lines, expect to be changing filters quite often when you first start using that stuff, if ever..

Carbon dioxide? You may have been more believable guessing it was laughing gas.

In the UK, wet tanks can be entered with Breathing Apparatus otherwise the tank is drained, forced air vented and entered without BA after the tank atmosphere is checked (electronically-not with canary's, even in Wales) continuously for remaining vapours.

The tanks would have been inerted with carbon dioxide before entry...This doesn't make any sense at all to me.


Here's the basics of how tank entry is done where I work.
Before entry the tank is defueled/sumped then purged using blowers and venturis to obtain the correct Lower Explosive Limit and oxygen content. This is considered a fire-safe condition and allows for entry using a supplied air respirator. Repairs can then be performed or the people entering the tank will remove any remaining fuel and the tank will continue to be purged until the health-safe limit has been reached which allows entry without respirator, although its still recommended. If the tank contained JP-4 or Jet B a health-safe condition is not possible (not an issue for me). During the whole process the tank is continuously monitored and ventilated.

Unless it is an A380!?

Forced air?

In the US, you inert tank with carbon dioxide first, this removes any oxygen and the LEL level is zero. Then you go in supplied air...

Using carbon dioxide it takes about 2 mins to get the LEL level to zero...how long does forced air venting take, 2 days?

Yes, purged with forced air, hours not days and in the US.
What you describe is still considered a hazardous atmosphere, a fire-safe atmosphere is the minimum that has to be maintained where I work. Can you reference any current aircraft maintenance manuals that allow the use of inerting for fuel tank entry?

I will look into the exact specs, but I will say that my portion of the adventure was certification under OSHA regulations regarding confined space entry of a fuel storage tank.

I can't comment on current H&S legislation, but I've crawled into plenty of tanks in my time with nothing more than a socket spanner and a wander light.

Having read the rest of this thread, sounds like I'm lucky to be alive !

Probably best not to identify my erstwhile employer, or the de Havilland three-holer involved. :O

Whilst doing the walkround before a check flight in a large RAF radial twin I noticed a drain valve cover dangling on its chain. (first round to Bas)
The offending airman was court martialled a few weeks later for nicking petrol :{

On the recent BBC programme about the full maintenance job on a B747 it showed the presenter and a technician inside a fuel tank without breathing apparatus.

The tanks would have been inerted with carbon dioxide before entry...

I really hope not! They would have been dead within minutes.

I cant speak to the BBC Special, but it must have been staged, as there is no way you would or could be in the tank, unless it was brand new, and that still requires confined space entry procedures.

Boeing (http://www.boeing.com/commercial/aeromagazine/aero_04/textonly/s01txt.html) references Nitrogen, but I have found that Carbon Dioxide is much better, takes less time, and uses much less to inert a tank...
its very easy to get an overpressure condition going with cylinders.

The CO2 cylinders are readily avail with no transport issues. Once the LEL and LFL levels are meet, you can hook up the air vent system to keep the levels down for entry... and not have to keep pumping gas...

Depending on atmospheric conditions, a center tank takes between 5 to 10 minutes to inert...

other than that, I guess you would have to see through this where you are located at, and verify Carbon Dioxide can be used, at least there is Boeing data to validate the methodology. Since there are exhaust gas systems that inert the tank with carbon dioxide in-flight, I would surmise there is no problem with CO2, but.... its all up to you and your group.

Related concepts in this doc...Ref para 4.7 (http://www.fire.tc.faa.gov/pdf/TG3.pdf)

I cant speak to the BBC Special, but it must have been staged, as there is no way you would or could be in the tank, unless it was brand new, and that still requires confined space entry procedures.Not necessarily, with the tank in a health-safe condition you can be in the tank without a respirator, although at least a half mask with organic filter is recommended.

at least there is Boeing data to validate the methodology.
No there isn't. Your link is to a study for fuel tank inerting for the purpose of preventing a potential for explosion while the aircraft is in service not maintenance. Boeing aircraft with a NGS (Nitrogen Generation System) system have to have that system disabled as one of the steps before tank entry.

I agree with Yeelep.

Having seen a few base maintenance layovers with work in the tanks, there was no requirement to go in with full gear, after sufficient venting.
Done it myself.

As for Boeing and Airbus, I havn´t heard of any CO2 purging methods.

Regards, J.V.

Yeelep,

The link on the Boeing word, the other document is related, but was provided to show CO2 is another option

Hazards of Airplane Fuel-Tank Entry (http://www.boeing.com/commercial/aeromagazine/aero_04/textonly/s01txt.html)

"pumping nitrogen into a fuel tank to prevent fire ignition will cause the oxygen concentration to decrease"

The CO2 is to inert the tank, basically you fill it with CO2, which is much heavier than air. This gets everything out, no dead spaces, and a 5 to 10 min time instead of hours...
Again, once it is purged, and the LVL/LFL levels are down, then you put the forced air system in place, allowing entry. Or just go in supplied air.

It is still a confined space entry, no matter what is in there.

Surely by pumping in CO2 or N2, ie displacing oxygen from the tank atmosphere you reduce the explosive vapour mixture to a tolerable level. Unless the tank is totally dry as soon as you start forced air purging that mixture rises again until all puddled fuel has evaporated? I do not see how the CO2/N2 bit helps in any way.

Your talking apples and oranges. Nitrogen is used to inert the fuel tank while its in service. Using a inert gas in conjunction with fuel tank entry isn't a common industry practice on Boeing or any other aircraft that I am aware of. In the end you can do whatever you want. I just hope, for your sake, you have some sort of approved documentation if the FAA comes snooping around.

Hi!
Thank you all for your answers!!

Can i just ask a pretty dumb question?

Say that you have 3T in your tanks at the gate and you need a total of 18T today... Does the ''refuel people'' know that you want 18T in TOTAL? Or do they just know about these 15T that they need to fuel?

Please don't shoot me down

Thanks

BP,

When you ask for 18T, they fill till the gauge says 18t. Most modern Jets have a fueling system that allows the required FOB to be set on a panel at the fueling station, which then closes valves to stop the fueling at the appropriate figure.

It usual to then compare the actual uplift ( how much came through the bowser) with the calculated uplift ( difference between FOB before and after) and, if this is within a certain tolerance ( typically 1%) assume all is well.

If it's outside the tolerance, a manual check of FOB is carried out (different aircraft have different methods, such as " drip sticks").

Hi Thanks for your reply!

I mean you landed with 3T on your last flight. And you only need to refuel 15T to reach 18 and then you're ready to go. So the gauge shows the total fuel including these 3T that they landed with?

BP,
It ain't rocket science. It doesn't matter how much fuel you land with. Most times, you just tell the engineer how much fuel you want to depart with and he sets the panel to reflect that and the valves shutoff automatically or the engineer manually shuts off the valves when the fuel on board reaches that value.
Some commanders tell them how much fuel to add by calculating what they want added in kilos and converting to liters

I can't comment on current H&S legislation, but I've crawled into plenty of tanks in my time with nothing more than a socket spanner and a wander light.

Wot - no coveralls ?? :)

Since there are exhaust gas systems that inert the tank with carbon dioxide in-flight, I would surmise there is no problem with CO2, but.... its all up to you and your group.

The only aircraft that I am aware of that used exhaust gas for tank inerting were the Lavochkin LAGG-3, 5 & 7 piston engined fighters and the Il-2 Sturmovik of the Second World War. Components in the latter corroded through in 90 days due to the acids in the exhaust gas.

I'm not an engineer, but one of my family members who is, once told me that an aircraft is safer if it is left with fuel onboard as it leaves less room in the tanks for vapours to build up, and its the vapour that will ignite.

listen, this is not inflight, it is after fuel removal to enter the tank....you can sit there blowing air in for hours until the levels drop, or you can fill the tank with Nitrogen or Carbon Dioxide in a few minutes, then pump air...its up to you...I just added the process...figure it out for yourselves, but I cert this all the time...

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A man has died after an empty oil drum he tried to turn into a barbecue exploded at a house in Oxfordshire.
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