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. |
Never heard of it.
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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. :(
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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. |
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. :ok:
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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"... :ugh: |
I thought this was something to do with pensioners' winter heating allowance. :confused:
Never heard of the term before in four decades of aviation. :) |
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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Never heard off it, the only fuel my Granny used was gin!
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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. |
Wish I had lead a sheltered life like some of you folks...
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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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I looked in FAR Part 1 "Definitions". Could not find it their. Is "Granny Fuel" an EASA thing:}?
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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! :} |
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. |
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. |
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. Posted from Pprune.org App for Android |
shame shame shame:=
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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. 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. |
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. |
A quick Google suggests its a North American thing.... the term seems to be "granny gas".
There seem to be multiple mentions of it on one Canadian website in particular (stick site:avcanada.ca Granny Gas into Googoo) One post on that forum even goes as far as stating the following...... Unfortunately the concept of “granny gas” has become an industry standard, particularly for operations north of the 60th parallel. After conduction many long range trips with “granny gas” on board, the pilot eventually will consider this normal operation and not consider this to be a foolish act. There seems to be some confusion over the term, "granny gas". Contingency fuel is that above the normal legal amount the crew decides to carry over and above the legal minimum. Granny gas, is that extra 45 minutes the crew "hides" from the prying eyes of the dispatcher. It remains incognito, so to speak until that rare day when it's needed. It used to be very, very, very common practice. I know it saved my bacon once. I'd almost forgotten the extra 60 gallons I "hid" in the Racer, till one day, the tanks we were using blew |
Hmmm, on a KingAir 200 I flew for 10 years, we had several discrepancies in the gauges, yet the totalizer was actually very accurate, always. The gauges on the plane in question seem to be quite accurate. They are calibrated by maintenance on a specific schedule. They are calibrated at the 0 lbs usable fuel quantity, and the 1000 lbs usable fuel quantity. During calibration they will always ensure that what you have on the gauges represents at least what you have in the tanks, erring on the conservative side. The more I look into this issue, the more I seem to find reason for not taking 'granny fuel'. I've found in my informal survey that pilots tend to state their beliefs as fact. For example, pilots stating that the gauges are inaccurate or that the government regulating agency takes 'granny fuel', yet when asked for any evidence of either one they can't provide any. Not saying that you don't have any evidence for the gauges being inaccurate! :) And if there is a discrepancy in the fuel indicating system it should be snagged and the MEL consulted. |
I've heard the term, "Granny Gas" here in Canada for years...
I guess it would translate to something like, "Plus a pinch for Gram" in Limey speak? |
I would guess granny fuel would get you busted on a ramp check if it put you over max takeoff wt. Good luck.
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Granny fuel because dispatch cut you short of your comfort fuel sounds fine. personally, I just called them and told them what I needed.
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Originally Posted by john smith
There is no 'new' fuel figure. We dial up 100kg extra, which usually gives us the fuel we asked for in the first place
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Folks,
A comment on gauge/totaliser accuracy, in part the story is covered in the changes to certification standards over the years ---- showing the development of sensible thinking over the years --- as a result of hard won and usually deadly experience. Also the development of the concept of fixed final reserve, which is not 30m holding, but the amount of fuel, calculated or indicated, that is to take care of all the inaccuracies in fuel measurement, so that the engines are running at touchdown ---- the Boeing equivalent is minimum fuel for approach. No gauge or totaliser system in "accurate", all measuring systems have an order of accuracy. "Granny fuel", that I know as a "quick squirt for mum and the kids" is relatively common for small aircraft. Airline fueling practices should be far more exacting --- including adding extra fuel when the discrepancy between calculated fuel on board, and indicated fuel on board (including having used the corrected SG--- as in correcting the average SG to account for fuel on board SG v SG of fuel loaded) exceeds 3% --- and in the case when there is a serious mismatch, drip the tanks. And what goes on the loadsheet ---- the minimum fuel that you know you actually have on board. Tootle pip!! |
I can even have a guess who the Captain is.
Its not common to call it granny fuel. 19 seaters are in the main under 7500kg So we are not talking 200kg extra I would hope. Maybe 50kg which is 10mins extra. Some round up to the next 50ltrs of fuel. Some use 0.77 SP when ordering and some round down the arrival fuel. Its all OK until you have an engine failure in LVP's and you can't look out the window and see and avoid. These machines are in general getting on for 20 odd years old and they weren't very spritely climbing on one engine when new. Also another thing to take a look at is the drift down which is surprisingly low at max weight. So you may have issues with reaching MSA if you have already got 18 blokes on-board who last saw 86kg in there teens. Personally I just don't, I check the MPI's to make sure they are the same as the gauges and then fill up to the required amount. No more no less. But there are more than a few out there, that to be honest are correct reckon that your more likely to have issues due to low fuel than an engine failure when flying a route at min fuel and Max load. An extra 50kg isn't so bad its when they start going 100's of kg over weight or in LVP conditions it seems a bit crazy to me. |
As has been alluded to by previous posters, fuel density variation can be significant,
Ihave dropped 1500 imperial gallons of petrol into an underground tank, the diprodshowed 1530 Gal........12 hours later, it's at the correct .1500. Diesel/Kero is pumped and metered, without density-correction, you get less WEIGHT of fuel on a warm day, than a cold one, if metering is by volume. I find the use of "mixed units" (Kg / Lbs / Litres /Imp. Gals. / US Gals. ) quite disturbing....do the Bowsers have load-cells and deliver WEIGHT ? or metering-pumps and deliver by VOLUME ? ISTR the Gimli incident was caused by just this "scrambled thinking" Weight is, of course, the crucial issue with a small aircraft. The arbitrary "nominal" weights used on a Pax. airliner probably give a wider variance of true load than the fuel density variation. so, all pretty hypothetical, really, as far as big jets are concerned. When it's a choice of fuel /luggage/a soul to keep within W&B limitations, that's a different kettle of fish! |
Bowser delivers volume. Converted to Weight with reference to S.G.
Can be significant on a large uplift. In the OP's case I don't know. Do smaller a/c use a standard SG like large short haul a/c? Posted from Pprune.org App for Android |
Large uplift :D they use less than the big boys do taxing.
Max fuel is between 1200kg and 1500kg and its not uncommon to start off with less that 800kg. They burn about 6kg a min. As for the S.G this can a problem even if you get given one by the bowser man. The S.G tends to get taken early morning. And you have a special bowser that can do over wing fueling. So it can sit out in the sun all day until you refuel. Which is why a lot of us use an SG of 0.77 when ordering. A 500-1000trs is the normal uplift at a time so its won't give you that much extra over. Most of the modern TP's have pressure refuelling and the units I have used anyway pull 50-75kg of it initially which calibrates the S.G. before pulling up to the weight in the panel. And a cross check against the bowser S.G. is usually within 0.01 which would be normal for a bulk to bowser temp rise. |
Its all OK until you have an engine failure in LVP's and you can't look out the window and see and avoid. These machines are in general getting on for 20 odd years old and they weren't very spritely climbing on one engine when new. An extra 50kg isn't so bad As for the S.G this can a problem even if you get given one by the bowser man. The S.G tends to get taken early morning. And you have a special bowser that can do over wing fueling. So it can sit out in the sun all day until you refuel. Which is why a lot of us use an SG of 0.77 when ordering. A 500-1000trs is the normal uplift at a time so its won't give you that much extra over. Most of the modern TP's have pressure refuelling and the units I have used anyway pull 50-75kg of it initially which calibrates the S.G. before pulling up to the weight in the panel. And a cross check against the bowser S.G. is usually within 0.01 which would be normal for a bulk to bowser temp rise. |
There are a few Accident reports of 19 seaters which have come to grief.
I won't post the direct links to them in case it gets the operators backs up that I am implying that they operate overweight. Which I can't be bothered dealing with. But I am sure with out much searching you can find them. It may not be the flight in question which causes the issue. It maybe 50-100 sectors later that issues occur. |
Virtus,
Check your calculations...Kerosine is lighter than water...you need to multiply by around 0.8 to get from litres to Kg.... An extra 100 or so is ok, it will not change anything on a medium Jet. The gauges are less accurate than that. |
An extra 100kg is min an extra 5% of your traffic load on these old heaps.
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Granny Fuel:
Fill mains to full. Plane sits on ramp, fuel expands and spills over into aux tanks = Granny fuel. |
:D that's a huge like OK465
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