Granny fuel
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Granny fuel
I've run into a few different definitions of "granny fuel" from pilots but a common one seems to be "fuel that is added to the tanks to account for fuel quantity gauge error, and is not shown on the weight and balance". Granny fuel essentially applies to fuel added to the tanks and not shown on the weight and balance, regardless of what the reason is.
This seems to be unsafe as well as illegal for a number of reasons. I've talked to pilots about this and it just seems that most refuse to acknowledge they're doing anything wrong. They come up with justifications for it such as asking if I would trust my life on the fuel gauge being accurate.
Are others encountering this in their airline operation? This is specifically regarding a large, twin-engine turboprop airplane that carries up to 19 people.
This seems to be unsafe as well as illegal for a number of reasons. I've talked to pilots about this and it just seems that most refuse to acknowledge they're doing anything wrong. They come up with justifications for it such as asking if I would trust my life on the fuel gauge being accurate.
Are others encountering this in their airline operation? This is specifically regarding a large, twin-engine turboprop airplane that carries up to 19 people.
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It's illegal to use grannies as fuel. 
If you use too many there will be none left to knit your warm, woolly, winter socks and traditional Christmas jumper. 
If you use too many there will be none left to knit your warm, woolly, winter socks and traditional Christmas jumper.
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Never hard of it but it sounds like the sort of thing that happens in 19 seat turboprop operations. If its endemic in company culture and you don't like it the only solution is to change jobs.
It is certainly illegal and potentially hazardous. It is most definitely grossly unprofessional.
It is certainly illegal and potentially hazardous. It is most definitely grossly unprofessional.
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There has always been " some for mum and the kids " - those couple of 100 kgs that just fell into the tanks magically - just in case. Perhaps that is what you are thinking of. 
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Well if they are so eager to be on the safe side because of "fuel quantity gauge error" and they add fuel to tanks because of it, why not be on the safe side regarding W&B and add "granny fuel" to loadsheet as well? Sounds like someone wants to be on the safe side regarding fuel, but is happy to fly overweight - so much for being on the safe side. And silly me, I thought idea was to put the actual fuel in tanks at break release into loadsheet...
It's probably the logic of the same people who think that if an aircraft can barely depart using improved climb (increased V2 procedure) with lowest flap setting that a higher flap setting will increase PLTOM, since "use of higher flap provides greater obstacle clearance"...
It's probably the logic of the same people who think that if an aircraft can barely depart using improved climb (increased V2 procedure) with lowest flap setting that a higher flap setting will increase PLTOM, since "use of higher flap provides greater obstacle clearance"...
Avoid imitations
I thought this was something to do with pensioners' winter heating allowance. 
Never heard of the term before in four decades of aviation.
Never heard of the term before in four decades of aviation.
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Never heard the term either. When I was a ramp agent, I once caught a bowser driver deliberately entering an additional 100 kg on the refuelling panel. He told me he was doing so because on the A320 there was a known discrepancy between the fuel quantity indications on the refuelling panel and on the flight deck. Since the crew didn't seem to bother, I never thought about it again, and I never saw any bowser driver doing it again.
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Well if they are so eager to be on the safe side because of "fuel quantity gauge error" and they add fuel to tanks because of it, why not be on the safe side regarding W&B and add "granny fuel" to loadsheet as well?
At the place I'm at it's company culture. The pilots don't know any better either - this is usually their first job. It gets them indoctrinated with this false logic from the start and then they eventually pass it on themselves. It's frustrating to explain this to them because they're essentially brain-washed into believing that their fuel quantity gauge is precisely 200 lbs over-reading (requiring 200 lbs of granny fuel - some use more) yet believe that the fuel totalizer is accurate.
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hvogt, the refueller's 100Kg reset is common in my company. I thought it was done because the system sometimes stops the refuel before the required amount is present due to the fuel level settling after delivery, not due to an error on the indications (which I doubt exists). There are some skippers who'll get very het up if they get 20 or 30Kg less than they asked for and bawl the fueller out, so some of them up the quantity by 100 to avoid the unpleasantness.
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granny fuel, you are talking about 100 to 200 kgs, if you are not happy with it make a LMC on the load sheet, but maybe just stupid thinking, you are planning
for a MTOW takeoff, fligh tplan fuel includes 300 kgs taxi fuel, but runway was changed and you need only 100 kgs for taxi. what you do you ask ATC to delay you takeoff to burn off the execssive fuel?
don't make things to complicated!
for a MTOW takeoff, fligh tplan fuel includes 300 kgs taxi fuel, but runway was changed and you need only 100 kgs for taxi. what you do you ask ATC to delay you takeoff to burn off the execssive fuel?
don't make things to complicated!
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On MTOW, re- dispatch flights with minimum reserves, we used to tell the fuel guy to put in XXX "big gallons".
Also add some taxi fuel up to MRW, even if it was just a 5 minute taxi.
Also add some taxi fuel up to MRW, even if it was just a 5 minute taxi.
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Originally Posted by john smith
Fairly standard practice here for either us or the fueller to dial up an extra 100kg or so on the fuel panel
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It all depends if you believe the standard passenger weights, bags that are offloaded from the cabin suddenly going from weightless to 13kg. Etc etc etc.
There are a lot of unknown variables in the W&B that are not accounted for, 100kg of Fuel isn't going to do anything in an A320-sized aircraft. Offcourse try to get it as accurate as possible, but it's not an exact science. You would need to weigh every aircraft to achieve this. Then we also guesstimate the taxifuel in order to reach a guessed TOW. So lets keep some perspective.
With regard to the fuel panel on A320, it varies per aircraft. The 3 clicks will add 100kg, but the panel will show the same number for all 3. So say you want 6.7 I usually go until I see 6.8 and then go 1-click down in order to get 6.7 on the display. This will usually give around 6740 in the tanks, but sometimes less then 6700. A bit random per aircraft and even per refuelling. Also changing the number midfuel seems to sometimes mess things up.
Our digital w&b module alteady does a lot of rounding. Weightare determined to the nearest (highest) 100kg. So we see something like 68.6, no idea if that is 68.549 or 68.600
However on a small turboprop, a 100kg can be a major difference.
There are a lot of unknown variables in the W&B that are not accounted for, 100kg of Fuel isn't going to do anything in an A320-sized aircraft. Offcourse try to get it as accurate as possible, but it's not an exact science. You would need to weigh every aircraft to achieve this. Then we also guesstimate the taxifuel in order to reach a guessed TOW. So lets keep some perspective.
With regard to the fuel panel on A320, it varies per aircraft. The 3 clicks will add 100kg, but the panel will show the same number for all 3. So say you want 6.7 I usually go until I see 6.8 and then go 1-click down in order to get 6.7 on the display. This will usually give around 6740 in the tanks, but sometimes less then 6700. A bit random per aircraft and even per refuelling. Also changing the number midfuel seems to sometimes mess things up.
Our digital w&b module alteady does a lot of rounding. Weightare determined to the nearest (highest) 100kg. So we see something like 68.6, no idea if that is 68.549 or 68.600
However on a small turboprop, a 100kg can be a major difference.
Last edited by 737Jock; 24th Apr 2013 at 16:32.
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If the fuel discrepancy is within limits, does it matter?
I often get asked, for example "a good 47 tonne please eng".
We both know what the Captain means and the a/c will have something like 47.4 on the gauges.
Fiddlefactor notwithstanding, how many actually check the fuel S.G.
Never heard it called granny fuel though.
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I often get asked, for example "a good 47 tonne please eng".
We both know what the Captain means and the a/c will have something like 47.4 on the gauges.
Fiddlefactor notwithstanding, how many actually check the fuel S.G.
Never heard it called granny fuel though.
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we used to tell the fuel guy to put in XXX "big gallons"
I often get asked, for example "a good 47 tonne please eng".
We both know what the Captain means and the a/c will have something like 47.4 on the gauges.
We both know what the Captain means and the a/c will have something like 47.4 on the gauges.
Fiddlefactor notwithstanding, how many actually check the fuel S.G.
The airplane I fly has a capacitance-type fuel measurement system. It measures the volume by capacitance and then corrects the reading for temperature. It'd be correct if they compensated for S.G. but it doesn't. That being said, the difference is quite small as the fuel capacity is not exceedingly large.
However on a small turboprop, a 100kg can be a major difference.
A little more background:
The airplane has a way to measure the volume of fuel in the tanks to confirm what is on the gauges in the cockpit. When I check the tanks on the walkaround, the tanks always have had between 100-200 lbs (usually around 125 lbs) more fuel than what's on the gauges. So when we're taking off, we have ~250 lbs more fuel than what's on paper... assuming the Captain hasn't added granny fuel. Most add around 200 lbs meaning that we're taking off 450 lbs overweight. When the manufacturer flight tested the airplane, they did so at precise weights. When performance is specified for a particular weight, the airplane was tested at that weight... not at that weight plus a few hundred pounds for the allowed discrepancy on the fuel gauges, which happens to be 200 lbs per side. That being said, when you're 450 lbs overweight for a field or obstacle limited airfield, in an airplane that weighs ~10,000 lbs and 15,000 lbs, that will significantly affect your performance. Two engine isn't much of a problem but when you're single-engine, you might encounter some serious problems.
