Aircraft fuel question

Why would they drain the fuel?

Maintenance perhaps, all I know is that they do, and cannot return the fuel to the tanks - it has to come fresh, from the bowser..

spent?

They certainly drain a small quantity of fuel, to ensure that the tank contains only fuel (and vapour) and condensation has not caused water to pool at the bottom of the tank and be in danger of being pumped into the engine(s) in flight.

Yes I suppose so. Get the water out. I would expect it to e.g. get reprocessed and sold on as domestic heating oil.

I do not know what aircraft fuel is made of but I always feel it smells like Keroscene

I only wanted to know, because I was going this morning to a local aero club, to buy some Jet A1, at 94p per litre. Just a small amount, for my workshop diesel fuelled heater. Red is unobtainium, despite the law allowing it, kero 60p perlitre, but only if you buy 500L, otherwise they want £1.90 or more per litre.

Last week, reading that Jet A1 works, and is near the same as kero, and others use it successfully, I emailed my local aero club and asked if I could buy 20L from their bowser. They agreed I could, no problem, just fill a form in, at the flight desk, pay and collect it.

Then I read something about people getting hold of the waste Jet A1, even cheaper, and wondered what they might call that waste fuel - hence my question here.

Whilst at the club, I asked them, and they say what ever they drain, goes back in the tanks, so 94p per litre it was.

Having now tested it on Jet A1, it was indistinguishable from running on Tescos white diesel, from the pump, other than the 41.9p per litre saving.

Jet-A1 is kerosene, used by jets and turboprops. Avgas is used by piston engines and is roughly leaded 4* petrol.

Theo

it is kerosene (sp) + special additives.

NATO specifies that jets and diesels must be able to use it

I can speak from experience.

The plane I was due to fly on was delayed due to the late arrival of another flight. The flight crew on the delayed flight were scheduled to crew my flight.

However, by the time we were able to take off, if the crew had continued to the ultimate destination, they would have exceeded their hours.

So the airline arranged for the aircraft to land at a intermediate point where they would do a crew change.

But in order to land at the intermediate point, if they had had their original load of fuel on board, they would have exceeded their landing weight.

So they had to offload a certain amount of fuel before we could take-off. The offloaded fuel was then waste (or more probably went for recycling)- it could not be used on another flight.

Are there less mission-critical uses for slightly contaminated fuel? For example, ground-based electricity generators.

Jeez! When I returned from Cape Town, while Apartheid was still in force, meaning South African Airways flights had to avoid most of mainland Africa when flying to Europe, we landed at Windhoek to let all the soldiers off for the Angolan War. Then we refuelled for the long flight to London, but after waiting for ages at the start of the runway, we returned to the terminal, as "the wind had changed in our favour and we were able to offload unnecessary fuel". That must have gone to waste, then. To top it off (!), after again sitting at the start of the runway, we returned again to the terminal to load up with fuel, "as the winds had again shifted". Somebody must have had a busy credit card that evening. After all that, we couldn't get to London, we had to stop at Munich in order to have enough fuel to get to Heathrow. The whole flight, from Cape Town to London, took 23 hours, and we never left the aircraft.

Maybe that's what my boiler burns!

Can you use kerosene in diesel engines? There's various ground tugs, service trucks, buses etc around the airfield. Although they might not like fuel additives.

Aircraft have an APU for electricity generation so not sure how much ground generators you'd need (yes if you're Concorde or a B-52 [*], but not so much for a 737).

Theo

It will knock like f*ck in a commercial diesel engine.

No compression ignition so it doesn't need anti knock

So depends on what you mean by 'can be used'

There's various ground tugs,

Interesting chart of fuels here.

My G-wagon had a 3 litre 5 cylinder Mercedes diesel engine with "Indirect Injection" and it would run on all sorts of fuel, including frying fat.

As could Field Marshall tractors.

Tim

Fuel is sometimes off-loaded to ensure adequate take-off performance if conditions have changed and performance is limiting, or to ensure take-off mass is below maximum if the anticipated payload has changed. AFAIK the fuel is returned to storage in those cases, but it can also be mixed with diesel for use in airfield service vehicles. Separately, small samples are drained before flight to check for contamination by water, or an incorrect fuel upload (i.e. AVGAS uploaded when it should be AVTUR, or vice versa) ... these samples are either discarded or (rarely IME) kept for analysis. AVTUR is close to paraffin. AVGAS has a few grades but the most common is "100 octane low lead" (100LL) - but "low" relates to what went before and the lead content is much higher than 4* MOGAS. I would not use 100LL in a modern car.

Couldn't a Chieftain Tank run on anything ?