A321 AAIB Report: Mayday/emergency landing due to fuel additive error
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I do agree that stipulating a heavy engineering operational instruction in ppm is almost deliberately making things difficult. But we can extend our discussion of "cheap" to the maintenance manual production, where once upon a time a professional in house technical documentation author would never have simplistically written it like that. Instead outsource the production, again to the low bidder, and they will just whack in the product manufacturer's spec sheet without consideration.
Without wanting to blame the hapless engineer, Googling something and then using a random calculator found somewhere on the internet, but without fully understanding the terminology...........Why did he not have access to a proper procedure and a proper, validated calculator?
Engine critical procedures, such as opening the cowl flap locks, the engine oil caps etc., have mandated dual inspections. Why not for fuel additives? Fuel is pretty critical !
Engineers attending aircraft I have flown, have print-outs of the procedures, and often phone another authority if they are not familiar with a particular procedure, to check. And that is fine and sensible.
Why this guy did not phone his boss or another engineer to check his figures is beyond me.
Engine critical procedures, such as opening the cowl flap locks, the engine oil caps etc., have mandated dual inspections. Why not for fuel additives? Fuel is pretty critical !
Engineers attending aircraft I have flown, have print-outs of the procedures, and often phone another authority if they are not familiar with a particular procedure, to check. And that is fine and sensible.
Why this guy did not phone his boss or another engineer to check his figures is beyond me.
Didn't want to admit/display his ignorance ?
But who was the supervisor that oversigned/stamped the task? If he did the task and able to countersign/stamp it then that is even worse, in that someone with that authority did not know/understand the task details and what he was meant to do! For heaven's sake who was the MRO management/QA people allowing such a person to be working on aircraft? Absolutely frightening for the paying customers and equally for the crew flying the aircraft!
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But who was the supervisor that oversigned/stamped the task? If he did the task and able to countersign/stamp it then that is even worse, in that someone with that authority did not know/understand the task details and what he was meant to do! For heaven's sake who was the MRO management/QA people allowing such a person to be working on aircraft? Absolutely frightening for the paying customers and equally for the crew flying the aircraft!
In order to keep a balance in the discussion we should also look beyond the blame of a person and also look at safety nets beyond the initial mistake. Perfection is not possible, we also depend on mitigation or shielding (redundancy, detection etc.)
Indeed, in such a high dilution ratio as this (1: 0.0001, or 0.001% or 100PPM), it is arguable that PPM is the clearest way to express it, as it uses only whole numbers. Also, being a multiple of 1e3 (1,000), it works very well with standard x1,000 multiples {eg. (k)g, (m)l etc.}, where % is x100, which prevents such easy multiples and the relatively simple use of k(ilo) m(illi) prefixes.
Both PPM and % are valid ways for engineers / scientists to express dilution ratios. Neither should be more or less likely to be prone to error, and certainly not by "add[ing] an extra step to a calculation", as you claim. Competent engineers should be expected to be able to work accurately with either.
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But who was the supervisor that oversigned/stamped the task? If he did the task and able to countersign/stamp it then that is even worse, in that someone with that authority did not know/understand the task details and what he was meant to do! For heaven's sake who was the MRO management/QA people allowing such a person to be working on aircraft? Absolutely frightening for the paying customers and equally for the crew flying the aircraft!
I would assume that the certified the task himself if he was a Licensed Engineer. With regards to the screw up over the calculation, as the MRO seems to be based in Cyprus perhaps English was not his first language and the instructions in the AMM were not totally understood - it is a situation that I have seen numerous times overseas especially with Airbus manuals that seems to be written by a committee when compared to those from Boeing.
One small example of this, if you look in one of the uncustomised manuals (The SRM for example) Airbus will list each and every MSN, one list might be the A319, another the A320 etc, etc. Why couldn't they just state A319, A320 or Effectivity ALL ?
The effectivity can be filtered in Airnav or AirnavX but it doesn't always work.
Boeing make your life easier with "Effectivity ALL" or B737-700 etc.
Since the concentration was specified in PPM by volume, but both the fuel and the product are normally measured in KG (and have different densities), there were actually 4 calculations required:
1. Convert the 6200 KG of fuel to 7678 L.
2. Convert 100 PPM to .0001.
3. Multiply 7678 L of fuel by 0001 to get .7278 L of product.
4. Convert .7678 L of product to .799 KG.
And that's after looking up the specific gravities of both the fuel and the product.
If the procedure had said that 1 KG of product treated 7760 KG of fuel, the calculation would have looked like this:
1. 6200 KG divided by 7760 equals 0.799 KG.
1. Convert the 6200 KG of fuel to 7678 L.
2. Convert 100 PPM to .0001.
3. Multiply 7678 L of fuel by 0001 to get .7278 L of product.
4. Convert .7678 L of product to .799 KG.
And that's after looking up the specific gravities of both the fuel and the product.
If the procedure had said that 1 KG of product treated 7760 KG of fuel, the calculation would have looked like this:
1. 6200 KG divided by 7760 equals 0.799 KG.
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Really? How does 'per million' (divide by 1e6) "add an extra step to a calculation", where 'per cent' (divide by 1e2) does not?
Indeed, in such a high dilution ratio as this (1: 0.0001, or 0.001% or 100PPM), it is arguable that PPM is the clearest way to express it, as it uses only whole numbers. Also, being a multiple of 1e3 (1,000), it works very well with standard x1,000 multiples {eg. (k)g, (m)l etc.}, where % is x100, which prevents such easy multiples and the relatively simple use of k(ilo) m(illi) prefixes.
Both PPM and % are valid ways for engineers / scientists to express dilution ratios. Neither should be more or less likely to be prone to error, and certainly not by "add[ing] an extra step to a calculation", as you claim. Competent engineers should be expected to be able to work accurately with either.
Indeed, in such a high dilution ratio as this (1: 0.0001, or 0.001% or 100PPM), it is arguable that PPM is the clearest way to express it, as it uses only whole numbers. Also, being a multiple of 1e3 (1,000), it works very well with standard x1,000 multiples {eg. (k)g, (m)l etc.}, where % is x100, which prevents such easy multiples and the relatively simple use of k(ilo) m(illi) prefixes.
Both PPM and % are valid ways for engineers / scientists to express dilution ratios. Neither should be more or less likely to be prone to error, and certainly not by "add[ing] an extra step to a calculation", as you claim. Competent engineers should be expected to be able to work accurately with either.
Having demonstrated themseIf to be utterly defeated by 100ppm, it is unreasonable to believe they'd have aced molecular concentrations, never mind finding it "far easier" as you claim.
As the manufacturer knows the density of their own product, and using as standard fuel density, Chu Chu's suggestion of the manufacturer specifying 1kg of product to 7,760kg of fuel is easily the best suggestion, as that is the very simplest calculation by a long way.
Inside every vexing problem is a very simple solution (ha!) struggling to be seen!
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I'm just saying
I'm struggling to understand why the manufacturer suspended the use of Kathlon, especially when doing that leaves EU operators with no approved biocide treatment.
It wasn't the product that caused the problem, it was gross misuse of it.
Failing a technical reason, perhaps the manufacturer's insurer is behind it?
On another topic, I hope that the "on-going AAIB investigation" includes a systematic MEDA (or equivalent) analysis of the Human Factors involved, for the industry's benefit as well as the AMO concerned.
It wasn't the product that caused the problem, it was gross misuse of it.
Failing a technical reason, perhaps the manufacturer's insurer is behind it?
On another topic, I hope that the "on-going AAIB investigation" includes a systematic MEDA (or equivalent) analysis of the Human Factors involved, for the industry's benefit as well as the AMO concerned.
Easiest would be if beside the 1kg treats 7.760kg of Jet fuel, a table for typical even masses of fuel is given. Like 129g for 1000kg 1.288kg for 10.000kg etc. At least that allows to check, that your calculated number is in the ballpark. On that product I doubt, that +/- 20% error would matter much, but you should not get it wrong by orders of magnitude.
As pilot you often use rule of thumb calculations for checking if the number given make any sense.
As pilot you often use rule of thumb calculations for checking if the number given make any sense.
Easiest would be if beside the 1kg treats 7.760kg of Jet fuel, a table for typical even masses of fuel is given.... you should not get it wrong by orders of magnitude.
1kg doesn't treat 7.760kg of fuel.
As pilot you often use rule of thumb calculations for checking if the number given make any sense.
1kg doesn't treat 7.760kg of fuel.
As pilot you often use rule of thumb calculations for checking if the number given make any sense.
You should be "checking if the number given make any sense" - in your very own words!
Last edited by pilotmike; 18th May 2020 at 15:40.
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That's possibly because of the continental way of using a decimal point in place of a comma, i.e. UK (and US) would write 7,760Kg but some european countries would write it as 7.760Kg (so there's a potential error of 3 orders of magnitude there). Certainly in the post it's confusing to my (UK) eyes, saying 1000Kg then 10.000Kg for 10 times as much.
Irrespective of the original dosing, the more surprising (and dangerous) thing is it didn't get picked up before it caused loss of thrust at take-off. Mistakes happen, but it does seem this one should have been caught long before it got as far as it did (the potential being there for a considerably worse outcome).
Irrespective of the original dosing, the more surprising (and dangerous) thing is it didn't get picked up before it caused loss of thrust at take-off. Mistakes happen, but it does seem this one should have been caught long before it got as far as it did (the potential being there for a considerably worse outcome).
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Over-reacting
Before anyone else criticises ground maintenance and throws in the "Pay peanuts, get monkeys adage", how many folk at the pointy end have royally screwed weight calculations and had some interesting flex take offs, or failed to configure correctly for take-off.
One common denominator here and that is we're all human.
One common denominator here and that is we're all human.
I agree with this, even for someone like me whose first language is English the Airbus manuals can sometimes be hard work.
One small example of this, if you look in one of the uncustomised manuals (The SRM for example) Airbus will list each and every MSN, one list might be the A319, another the A320 etc, etc. Why couldn't they just state A319, A320 or Effectivity ALL ?
The effectivity can be filtered in Airnav or AirnavX but it doesn't always work.
Boeing make your life easier with "Effectivity ALL" or B737-700 etc.
One small example of this, if you look in one of the uncustomised manuals (The SRM for example) Airbus will list each and every MSN, one list might be the A319, another the A320 etc, etc. Why couldn't they just state A319, A320 or Effectivity ALL ?
The effectivity can be filtered in Airnav or AirnavX but it doesn't always work.
Boeing make your life easier with "Effectivity ALL" or B737-700 etc.
I'm B1. 3 (Turbine Helicopters) and the difference between Airbus/Leonardo vs Bell/Sikorsky is a world apart.
Euro manuals are dumbed down to the point of the lowest common denominator, but somehow manage to complicate it even further!
No schematics or system explanation in Euro. Just an idiots guide which you are expected to follow verbatim.
Literally two pages of instructions to remove a Filter with illogical cross references and tasks, rather than "remove the filter".
Now whilst not relevant to this particular incident its a pointer of what is wrong these days.
The qualifications required to obtain a LAME has been dumbed down and now we are seeing the results. EASA standards are not universal across EASA.