Originally Posted by
PA28181
When I was working in engineering in the transport industry, we always looked for the "root cause" of failure of a component or system. This took some weeks in fact to solve some of the more complicated faults, so what is the "root" cause here, I would say without a doubt the wrong fuel was loaded ...
I fully agree, then you apply root cause analysis to the actual 'mis-fuelling' activity to identify the cause(s) then we're in a good place to develop some control to eliminate, or at least reduce the frequency in future.
In an ideal world you would want to engineer out (by mechanical means) the possibility of misfuelling, in the real world that simply isn’t possible. The width of the aircraft fuelling port is crucial to any mechanical method of preventing misfuelling. There are fuelling industry guidelines for the size of Avgas and Jet refueling nozzles, but these are not universally adopted by aircraft manufacturers. The wide ‘duck bill’ nozzle for jet fuel should be a minimum of 67mm across to prevent it going into smaller (40mm) Avgas fuelling port, the problem is that without 100% take up of the smaller port on every Avgas powered aircraft there cannot be a mechanical solution to the problem.
The only way to control misfuelling is by consistent application of a rigorous refueling procedure. There are people in the refueling industry who have produced such robust procedures, which IF applied will prevent misfuelling. That said following a procedure relies heavily on human performance, if that slips then a misfuel can occur. It is this weakness, the inconsistency of human performance, that is behind misfuelling.
In the environment I’ve come from (oil co – airfield refueling operations) misfuelling was taken incredibly seriously, it was without doubt the worst event a fuelling operator could be involved with. There was a good chance the operator would loose their job because the fact that a misfuel occurred was going to highlight that they had not followed procedure. As a consequence adherence to the procedure was good and it was an issue that operators were constantly reminded about during recurrent training and tool box talks. It certainly was not trained once and forgotten about.
A consequence of fuelling operators adhering to the procedure was that if there was a problem they would not continue with the fuelling; I've seen occasions when this would cause confrontation with flight crews/ operations staff, who for their own reasons might not be so interested in the finer detail of the fuelling procedure, and would be more focused on the speed of turnaround. The single most common cause of this problem was lack of grade placard by the fuelling port. If you are going to operate a misfuelling prevention policy then having clearly placarded fuel ports is a fundamental requirement. Placarding is becoming a more complex issue with the introduction of UL91 in addition to 100LL and that's before we consider that many aircraft now operate on road fuels (petrol and diesel) which adds even more potential for ambiguity and confusion
Within the fuelling operation there are many opportunities to put misfuel prevention controls in place. As already mentioned the size of fuelling nozzles and correct positioning of clear accurate grade placards are a good start but there are other controls which can be used. Before the fuel truck turns a wheel there may well be a verbal request for fuel, this is the first opportunity to ‘read back’ the request and confirm what grade is being requested. The fuelling nozzle can be colour coded and placarded with the grade so as to give an immediate cross check before the nozzle is introduced to the fuelling port. If something doesn’t look right “don’t assume – confirm”. The use of written fuel orders which clearly state the quantity and grade of fuel required. The use of colour coded documents for each fuel, black on white for jet and red on white for avgas.
However the one key feature of any and all elements of the procedure is that the fuelling operator must follow them. The working environment for the operator is very important, high quality effective training is vital. Although the captain is ultimately responsible for his aircraft a conscientious well-trained fuelling operator is often the key to a safe delivery of the correct grade of fuel.