Granny fuel

[Virtus]

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.

[BOAC]

Never heard of it.

[DX Wombat]

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. :(

[Agaricus bisporus]

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.

[SeldomFixit]

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:

[FlyingStone]

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:

[ShyTorque]

I thought this was something to do with pensioners' winter heating allowance. :confused:

Never heard of the term before in four decades of aviation. :)

[hvogt]

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.

[SOPS]

Never heard off it, the only fuel my Granny used was gin!

[Virtus]

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?

Yup. They also justify it by saying that the government regulating agency's pilots also use "granny fuel". Quite the claim and yet with zero evidence at all. Let's get really stupid - even if they did use granny fuel, they sure as heck aren't going to admit it in court to help support you when you're charged for breaking the law.

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.

[blind pew]

Wish I had lead a sheltered life like some of you folks...

[Agaricus bisporus]

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.

[captjns]

I looked in FAR Part 1 "Definitions". Could not find it their. Is "Granny Fuel" an EASA thing:}?

[mach 84]

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! :}

[747dieseldude]

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.

[BOAC]

Fairly standard practice here for either us or the fueller to dial up an extra 100kg or so on the fuel panel - and following the OP's query, are you then saying the 'new' fuel figure is not amended on the load sheet?

[737Jock]

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.

[TURIN]

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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[Pugilistic Animus]

shame shame shame:=

[Virtus]

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.

If you're (the 'general' form of you) going to put more fuel on the airplane, at least have the courage to call it what it is. If you want 47.4 tonnes on the gauges, then ask for it. Using words like "healthy", "big", "good", to describe more than the requested number seems somewhat cowardly. It's nothing like turning your back on your fellow troops and watching them get slaughtered while you retreat - but it is still a form of cowardice. Maybe indecisiveness too?

Fiddlefactor notwithstanding, how many actually check the fuel S.G.

I do. The maximum weights are the ones that are normally published for conversion (i.e. 7.00 lbs/US GAL or 1.85 lbs/litre). I find that the actual S.G. almost every single time I call for fuel is right around 6.81 lbs/US GAL.

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.

The airplane I'm referring too, and flying now, is considered a large aeroplane but just barely. I would consider 100 kg to be significant.

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.

[His dudeness]

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.

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.

[mixture]

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.

Or another example from the many on that website.....

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

[Virtus]

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.

What evidence did you have that the totalizer was very accurate?

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.

[3holelover]

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?

[bubbers44]

I would guess granny fuel would get you busted on a ramp check if it put you over max takeoff wt. Good luck.

[bubbers44]

Granny fuel because dispatch cut you short of your comfort fuel sounds fine. personally, I just called them and told them what I needed.

[BOAC]

There is no 'new' fuel figure. We dial up 100kg extra, which usually gives us the fuel we asked for in the first place - I misunderstood you - I thought you were discussing 'granny fuel' on this thread. In which case there is no "0.1 tonnes" to worry about since you wanted 7 and got 7? Non-event!

[LeadSled]

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!!

[mad_jock]

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.

[cockney steve]

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!

[TURIN]

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?


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[mad_jock]

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.

[Virtus]

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.

Yup. These planes don't achieve the published cruise performance either.

An extra 50kg isn't so bad

As long as you don't take 50 kg of cargo/pax with you.

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.

This doesn't happen where I'm from. When I call in for fuel I ask for the "batch corrected density". That is the density of the batch in the fuel truck which is corrected to 15 degrees C. The truck also meters at 15 degrees C. Today the batch corrected density was 0.819 kg/litre - which means that if you have a litre of jet fuel and the temperature of it is 15 degrees C, its mass will be 0.819 kg. That will not change as long as nothing is added or subtracted from the fuel truck - temperature does not affect this number! So if I want 500 kg of fuel I take 500 and multiply by 0.819 to get 409.5 litres. If the fuel temp is 15 degrees C then the actual volume pumped into the tanks will be 409.5 litres. If the fuel temp is greater than 15 then the volume pumped in will be greater, and if the fuel temp is less than 15 then the volume pumped in will be lesser. Whatever the case, I know that I will get 500 kg of fuel. I can use 0.819 throughout the entire day as long as the fuel is coming from the same truck.

[mad_jock]

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.

[despegue]

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.

[mad_jock]

An extra 100kg is min an extra 5% of your traffic load on these old heaps.

[MarkJJ]

Granny Fuel:

Fill mains to full. Plane sits on ramp, fuel expands and spills over into aux tanks = Granny fuel.

[mad_jock]

:D that's a huge like OK465

[BOAC]

These days that in itself could be worth 100 kg. - you saying they employ grannies??

[mad_jock]

We prefer the term GILF's

But you might term young totty ;)

[BOAC]

What about the GGILFs, MJ?

[mad_jock]

What ever floats you boat mate :D

But I personally would point them in the direction of our technical support staff who are more appreciative of there attributes.

[sevenstrokeroll]

granny fuel...never heard the expression...but I have heard of the practice

it is wrong

weight is weight. if you need extra fuel, take it...leave cargo/payload/passengers behind.

report this practice to the FAA or whatevercountry you fly in.

[High Energy]

Never heard of the expression but I like it! Anyway, on the 737NG this 'granny' error is defined as 2.5% of full scale reading of the fuel quantity indicators. So you can quickly figure out what your 'granny fuel' would be. And that will be my excuse from here onwards. :ok:

[Pratt X 3]

So when you are fretting over the weight of the Evil Granny Gas, do you also consider all the dirt, dust, dead bugs, dead birds, live birds, bird guano, bird nests, lost pens, wrenches, coffee mugs, nudie mags, water, etc. that your "large", twin-engine turboprop 19 seat airplane has acquired since it was last weighed? And do you weigh every person, including the pilots, and everything they bring onboard the airplane before departing? Or does your airline use standard weights? So how much does that add to the official numbers?

[GemDeveloper]

When I was an undergraduate engineer, I spent a summer vacation working in the stress office at BAC, Hurn, helping with the final stress of the BAC 1-11 500 series. We were all hoping that we were not going to find too many reserve factors less than one, as the first aircraft was flying already... co-incidentally, the last flight in the U.K. of a 1-11, ZH763, on Friday is noted on the Military Aircrew blog.

The standard weights that were used were 150 lbs for aircrew, and 140 lbs for passengers; that included carry-on baggage, Jepperson bibles, the lot.

Given the current propensity for SLF to take as carry-on sufficient baggage to see them through a fortnight's holiday, to say nothing of the ever widening girths of our fellow human beings, what are the standard weights that you use in your operation? I can remember an occasion in the mid-90s when all the pax, with their hand baggage, were weighed at the bottom of the air bridge just prior to boarding a BA LHR-NRT service. I wonder what happened to the data? I was slightly embarrassed at the time, as I had a complete mini hi-fi, with speakers, about my person, as I was heading back to a part of the world where they were unobtainable, and needed something on which to play CDs. :=

[mad_jock]

Its 86kg for a male 68kg for a female and 35kg for a child.

They tend to weigh both carry on and checked in bags.

If its the 19 seater which I think it is its not even designed to a civilian spec.

Someone planted one on the runway recording 5.6g, it split the main spar and a pax commented it felt like a normal landing nobody hurt. Recently though there was one which had a leg come off on landing under 2g due to a fatigue crack in the gear.

[Natstrackalpha]

The only time an aircraft has too much fuel is when it is on fire.

[Virtus]

So when you are fretting over the weight of the Evil Granny Gas, do you also consider all the dirt, dust, dead bugs, dead birds, live birds, bird guano, bird nests, lost pens, wrenches, coffee mugs, nudie mags, water, etc. that your "large", twin-engine turboprop 19 seat airplane has acquired since it was last weighed?

So because we don't know the exact weight of the people on board, and the dirt, and the lost pens, etc., we should forget about using the exact weight of the fuel on board? I guess we could just come up with a standard fuel load based on distance along the route and forget about winds and other factors that affect the actual load of fuel required for a particular trip. Nice logic! :ugh:

I could list a number of fallacies from here that would apply to your logic - Common fallacies (http://www.nobeliefs.com/fallacies.htm)

They tend to weigh both carry on and checked in bags.

Yes, all carry-on baggage is weighed separately - it can be included in the standard weight for a passenger but we choose to weight them separately.

The only time an aircraft has too much fuel is when it is on fire.

That quote belongs in the same category as, "A good landing is one which you can walk away from. A "great" landing is one which lets you use the airplane another time." and "Your mom is so...." - they aren't correct and they get old fast.

Your quote might be correct if fuel didn't weigh anything. Unfortunately, it does. I can think of many cases where having less weight would be better - engine failure on takeoff, for one.

[mad_jock]

We try and train commercial pilots out of that crap.

The other time is when an engine goes bang then you discover that there is not enough runway infront of you to stop.

Then of course just as your rotate maybe you can't climb and hit a hill or a mast.

Then you might go for struggling round the circuit in the wrong direction and forget that Vmca goes through the roof if you start banking towards the dead engine and while your struggling to hold height you suddenly run out of rudder and loose it and spin in.

But hey engines very rarely fail on takeoff do they thank goodness.

The guys that seem to not care and take the piss the most tend to be the ones with a fair bit of experience with single engine GA work when its never really made much difference if they were over weight. They are also the ones that seem to think height is safety in a twin and go for V2+10 climbs all the time. Try and explain to them speed is safety and terrain separation is assured if you follow the performance sheets in a twin and its just alien to them.

[Virtus]

+1 to that, mad_jock.

I'm surprised to hear the logic of some pilots I fly with. I had a pilot (Captain) within the last week tell me that if there wasn't a usable altimeter setting available at the airport you were flying an instrument approach at, you could use the altimeter setting from another airplane on 126.7 that's nearby. I tried explaining that it firstly isn't safe and that it also isn't legal but that had no effect. :(

[mad_jock]

I think you need to find another job mate.

[Virtus]

I've been told the same thing recently by someone else... I agree.

[mad_jock]

I take it your not working in Europe.

[Virtus]

Correct. I have my FAA and Canadian licenses. Got a job for me in Europe?!

[mad_jock]

Not with those tickets.

[Slasher]

I notice its those cheap and nasty low cost outfits
who make a real song and dance about ordering a
"good" level of fuel.

One would swear blind an extra 100kg on a 737 or
320 is literally bankrupting 'em. They also make a
huge bloody stink about actual arrival fuel too so
I'm told, if its more than 200kg over CFP.

[mad_jock]

To be fair Slasher I have never been given stick about even taking full tanks.

Its when you bang on min and offload that the pillocks come out the wood work.

I have learn't though that if you don't even engage them in discussion eventually they don't bother even trying to bully you which is what it is.