Fuel Check
 

Hi

Another quickie. Bar the standard fuel check, FOB v CMR and the surplus/shortfall, why do some operators like to do a burn check, actual v planned burn? Is there a benefit in this which is not reflected in the primary way of doing it.

Regards

Pin

Are you talking about the extra 'used v planned' at the end of the flight or during?

Good way of picking up a fuel leak.

If you're referring to a "How Goes It" time/fuel check, (more commonly done on long haul international flights), there are a number of reasons for doing it.

Besides the already mentioned fuel leak possibility some others that I can think of are:

Enroute winds different than forecast and flight planned for

Altitudes, mach#, or routing different than planned

Actual gross weight or CG different than reflected on the weight and balance record

Airplane not properly trimmed

Engine and/or wing anti-ice required enroute

MEL/CDL drag penalties or APU operation required by MEL/QRH

Weather circumnavigation

Clearance limit issues (eg enroute holding at an FIR boundary)

Wrong drag coefficient entry in the FMC

Some planes/engines in the fleet just perform differently than others

Many others that I can't think of....but Ppruners will.

If I misunderstood your question, disregard all of the above.:)

Fuel totalisers more accurate than guages perhaps?

How else do the engs in HQ work out the fuel bias for a particular 'frame?

My company doesn't recommend it but I do it because I feel like I could pick up
any discrepancies early. ( or wind/ temp effects etc, basically it reassures me).

Our flight plans have columns for fuel remaining and fuel used, we compare the planned vs actual figures. It is useful to check both for two reasons.

1. Double checking.
2. If one figure changes and the other doesn't, it is easier to diagnose the problem.

Example 1 (leaking from tanks / lines):
Hour | Extra fuel on board | Extra fuel burnt
_1__________4_______________1.5
_2__________4_______________1.5
_3_________3.5______________1.5

Example 2 (inefficient engine):
Hour | Extra fuel on board | Extra fuel burnt
_1__________4_______________1.5
_2__________4_______________1.5
_3_________3.5_______________2

OPS 1.375

In-flight fuel management

(a) in-flight fuel checks

An operator shall establish a procedure to ensure that in-flight fuel checks and fuel management are carried out according to the following criteria:
1. a commander must ensure that fuel checks are carried out in-flight at regular intervals. The usable remaining fuel must be recorded and evaluated to:

(i) compare actual consumption with planned consumption;

(ii) check that the usable remaining fuel is sufficient to complete the flight, in accordance with paragraph (b) “In-flight fuel management” below; and

(iii) determine the expected usable fuel remaining on arrival at the destination aerodrome;

2. the relevant fuel data must be recorded

Aside From the reasons given in previous posts, this would be a reason as well. Depending on aircraft type and FMS the FMS prediction may not always be accurate. Step climbs you can not program etc.

All are Legitimate Reasons
 

All of the cited reasons are valid and they apply to short domestic legs and well as those 12-15 hour killers. Out of gas is Out of Gas, regardless of location.
In my experience, the more experienced the pilot, the more often s/he checks actual fuel against expected burn.

It's done to monitor aircraft performance for a variety of reasons. It can be an early way to detect an abnormally high fuel burn which can be critical on longer flights. It can detect a fuel leak. The FAA and maybe some other agencies allow "redispatch" flight plans. On these, a minimum fuel value at a certain point on the flight plan must be met or exceeded, otherwise the flight has to divert. It's important to detect and solve the problem early if it appears that you might not make your redispatch fuel, otherwise you may find yourself diverting.

Worked with a company that had an issue with abnormal fuel burn on an MD11F. Several months passed before the aircraft was being re-positioned empty and the flight mechanic went back for a smoke noticing a vapor stream out of an over wing fuel panel, panel was loose and would suck out 10K lbs from top off on average (the MD11 auto transfers fuel). Unique yet simple example as the first thought was an engine issue that could not be pinned down.