Fuel SG and Bowser Uplift vs Calc Uplift
 

Hi all. Need some help in Fuel Discrepancy check. ( still learning please bear with me)
The bowser uplift is calculated from the fuel receipt ( litres x s.gravity) to convert to kilos.
1) The station where u uplift the fuel tells u the SG. how do u know if the SG given is correct? and is there a typical range for the SG?

2) If the Bowser uplift Vs Calculated uplift ( Figures u get from the fuel gauges after uplift - before uplift) does not agree ( which is often the case) , what is the acceptable difference?

3) Referring to Question 2 above. So what happens if the difference is out of the acceptable range ( assuming u checked the sg & the uplift difference again and still yield the same result)?

Many thanks :)

1. SG is checked every morning prior to the first fuelling of the day and also includes checks for water etc. The gravity should not change for that batch of fuel. I can't recall the acceptable range as it's been years since I pumped the stuff.

2. All guages should be tested and sealed, if there is not a seal mark do not accept the fuel. They are usually quite accurate...

3. Don't know.

OB :ok:

Don't know what or where you're operating, but I had a similar case not long ago at a large West Coast airport. Fuel ticket indicated 21,000 gallons uplifted, and FQI indicated 208,000 on board. Usual delivery is around 24,000, all else being equal.

Modern large Boeing aircraft have density measuring system in all tanks, so we used that of the CWT to measure the density of uplifted fuel and to figure out that the fueler had just supplied 3480 gallons of free fuel. Stick the tanks to verify actual levels on board, and done.

This has happened 3 times to us in the last 10 years. One time the hydrant truck meter "forgot" 11,000 gallons on a -400 delivery. Of course, each time the offending unit has been pulled off the line, and a flow check done, which always comes up within limits (~ 10 gallons in 25,000) so it's a mystery.

Just for reference, there can be a range in density. I've seen values from 6.68 to 6.90, depending on various factors.

1) SG range for Jet A1 is 0.755-0.840. We are unable to measure this data ourselves.

2) Acceptable discrepancy is set by the operator. For example, my company expect maximum +/- 2% discrepancy [100x(actual uplift-calc uplift)/calc uplift].

3) If discrepancy > +/-2% and within 200kg (A320) or 400kg (A330), no further action required. Beyond these values, maintenance action is due.

1. The S.G. is checked several times a day. One asks for the S.G. from the bowser driver during every refuel operation. if he doesn't have a current one to hand he can contact the fuel farm direct by radio or phone for the latest reading.

2. The allowable difference (discrepancy) between uplifted and calculated fuel is dependent on a/c type and airline policy. Some airlines use a standard +/-3%, others use an actual figure (Kilo/Litre) based on a go-nogo graph which is usually carried on the flt deck in the refuelling manual.

3. If the fuel discrepancy is out of limits one tweeks the S.G until it isn't. :E





Ok the last bit's not true, if it's out of limits then a stick/drip check is required to determine the actual fuel on board. It can take a few minutes (737) or half on hour or more if it's a 747.

Hope this helps. :ok:

Pprune is fantastic. Thanks for all the help guys. better write it down b4 i forget.:)

Right on TURIN....

that's what I've been doing for the entire fifteen years of flying Boeings...

if it's not within 3%, simply dip the tanks....though that didn't happen often...

am I understanding you correctly in that sometimes the refueler DIDN'T have the fuel specific gravity figure when he arrived at the airplane!

I can't ever recall accepting a fuel upload without the specific SG figure.

EW73

Yeah, what Turin said. APU burn can also be "tweaked" a bit.

Rule of thumb:

15 deg C SG .80
30 deg C SG .79
45 deg C SG .78

Take calculated uplift in kG, divide by actual uplift in L. If resulting SG is reasonable, put in techlog. Everyone happy, all numbers match.

Not an approved method though....

We have a Hydrometer and a Thermometer along with SG Conversion tables in our Bowsers so that in the event of a member of the Crew requesting an SG we can perform one at the side of the Aircraft via the Visijar located on the Bowser, never been asked to perform one in the 2 years i"ve been Fuelling though.

Refuelling big aircraft, B777 sized, I always ask for the SG. All the dispensers at ARN can measure it on the truck, and we can watch them do it. I find the SG changes often, it not only depends on temp, but which refinery the fuel comes from. We get fuel from different refineries and see the SG change often.
But on small aircraft, my company uses a standard SG of 0.8 all the time. When fuelling an A319 with 6000 litres, the difference from mid-summer to mid-winter is only around 200kg, so why bother? And I can calculate litres x 0.8 without a calculator!

Many large aircraft, B744 and B777 for two, will show you the uplift SG on the fuel maint page on the EICAS. They get this from the densitomitor in the tanks.

Be careful when you do a stick check.
Fuel gauges are very accurate. Sticks are not. Use the sticks to roughly check the gauges. To accurately stick check takes a lot of time.
And if you are stick checking an A320, call an expert. To convert the stick reading to the tank qty is an art.

swedish steve
 

Once again steve your input is spot on.A drip or stick check , done accurately takes quite a while.Most stick checks are pretty rough affairs and unless the aircraft attitude is measured very accurately and fuel is not sloshing around (from wind, pax movement, loading unloading holds etc) is rather a crude confirmation that you have roughly the right fuel.

PS. note that there can be quite a difference between uplift SG and that in tanks.