Posts about: "Biocide" [Posts: 25 Pages: 2]

In terms of the Mayday message, maybe Reading into it too much, it was not \x91lost power\x92 but loosing power. \x91
clearly we have no idea at this point how fast this happened, but slowly enough to state this.

however it has been seen with the Jetstar incident below that both engines can lose power simultaneously due to fuel filter blockage due to something in separate tanks.
is there someway the tanker could have picked up some contamination somewhere!?! I know the biocide (showing that even previously \x91safe\x92 additives can cause issues) in question is no longer used.

https://aerossurance.com/safety-mana...-genx-biocide/

This got me thinking about a report I read where an Auckland based maintenance facility added too much biocide to an aircraft fuel tank by a factor of ten. From memory the Engineer simply read the instructions wrong or calculated the additive amount incorrectly and the cross checking systems were either not in place or they failed. I searched online for it but could only find the following;

So my point is, if we are speculating about fuel contamination causing dual engine failure, it is possible that a fuel contaminant is specific to a particular airframe and not the supply system. Obviously not saying that is what happened here, but it goes to show how many possibilities exist.

Only two 787 dual loss of thrust situations I can think of is Jetstar into Osaka (biocide issues) and Jal on rollout with a TCMA malfunction.

Fuel contamination is certainly a valid theory. The main thing working against it is that it would seem from the aircraft's flight path is that both engines failed at exactly the same time and lost thrust simultaneously. The chances of this are non zero, but remote. I say that as there appears to be no yaw, or other controlling of the aircraft - either by pilot or automation - that would suggest an asymmetric thrust scenario, even for a few seconds.

Yes, Jetstar had the biocide issue but did not immediately hit both engines within seconds of each other.

It's my understanding that both engines draw fuel from independent sources during that time (which may be fed from a common source (eg central tank). But again, the odds of both failing at the exact same instant is low, but not zero.

Fuel tank biocide treatment gone wrong?
Now contaminated fuel has been discussed before, but what keeps coming to my mind ist the incident of A321 G-POWN on 26 February 2020.
There is a sumary on https://safetyfirst.airbus.com/fuel-...ion-treatment/
On 26 February 2020, an Airbus A321 (G-POWN) being operated by Titan Airways on a non revenue positioning flight from London Gatwick to London Stansted in night VMC took off just after midnight and almost immediately after it became airborne experienced successive problems (stall/surge) on both engines.
The Aicraft had undergone biocide treatment after fuel tank contamination was detected.
However the the engineer was confused by the term ‘ppm’ – meaning ‘parts per million’.In the end he used an online calculater, got it wrong and entered 37 times the required ammont of biocide, plus not mixing the biocide in the correct way with the fuel.
That did not go well with the HMU's.

I\x92d like to give you another option to consider in what must be a worrying time;
Am I right in saying, from a mathmatical perspective, that dual engine flame out due biocide overdose would be more likely than a TCMA activation shutting down the engines? Considering we have examples of engines reducing to idle within seconds of each other in the past, but we have no examples of airborne TCMA issues I would have thought this to be the case. Likewise, nefarious intent also appears more likely statistically than a TCMA issue.
I have high-school level statistics under my belt so I pose that as a question for people much smarter than myself.

On the statistics I would be wary of selection bias (in reverse). Until now this a/c type has had 1m hours without accident, so what has happened is by definition incredibly unlikely. If you attend a meetup of lightning strike survivors, it is not much use to say how rare it is to be struck by lightning (if you see what I mean).

Entirely valid to opine on the relative probability of different causes of course, just to note that by definition we are looking at an incredibly unlikely sequence of events.

There is a possibility that doesn\x92t get much air time on this forum that satisfies all the \x91facts\x92 ( pprune facts mind you), and requires less mental gymnastics to believe than many of the theories put forward. I\x92m not saying it\x92s what happened at all but it seems much more likely than a TCMA fault to me.
This link is to a Japanese report on a Jetstar 787-8 with GE engines that had both engines drop below idle while airborne due to magnesium salts effecting the operation of the FSV spools. The Magnesium salts came from a biocide dose by maintenance two days earlier.
For some reason I can\x92t paste the link but if you google JTSB the report number is AI2020-2.
I think it\x92s quite easy to imagine that a simple maintenance error ( 1000ppm instead of 100ppm) combined with extremely bad luck on timing lead to this accident.
I think I\x92m favouring a theory like this for its simplicity and the fact that fuel is the elephant in the room when you are dealing with a dual engine failure.

That’s really interesting, I’d not heard of that incident. The report does say though that particular biocide had been withdrawn due to other engine thrust occurences.

In that report, the factual conclusion is:

4. PROBABLE CAUSES
In this serious incident, it is highly probable that, when the Aircraft was descending for
landing, there occurred oscillation in rpm of each engine causing both engines to temporarily fall
below idle at separate times because Residue primarily composed of magnesium salts accumulated
in spools impeded movement of spools that involved in fuel metering of both engines. (emphasis added)

and the narrative taken from the pilots is that while they happened in short order, the engine issues were not simultaneous. Not to say they couldn't be simultaneous, but they weren't. Also, the problems arose in the descent, as the engines were throttled back. Again, not to say it couldn't happen in the take-off, under full power.

Yes I agree that it’s unlikely that it was the same biocide as the Jetstar incident, or even a biocide at all. I just think that incident highlights the vulnerability of something ( fuel) that has direct access to both engines at the same time.
From what I can gather the biocides are required to be injected into the refuelling line with a special little wheel mounted pump in order to ensure it mixes evenly. Even something as simple as a U/S piece of kit and a late night work around could be problematic.
A day before the Jetstar engines rolled back we didn’t know that that particular brand was only 7% soluble in Jet A1, yet it was. Is it possible that another brand has another issue? Or that a fantastic brand of biocide is used excessively? Or that no biocide is used at all and the actual microbes clog the spool/ filter instead of other particulates? Or any other number of things. I know it’s unlikely, but something unlikely has definitely happened, I just wanted to point out that it may surprise us all as to how simple it is in retrospect.
As a side note, according to a quick internet search the biocide in question was rebranded with a slightly different name and is still available for purchase. ( not saying that it’s being used in Airliners, just that it’s still out there waiting to clog up your D8)

(disclaimer: not a pilot, just some experience in petroleum and power engineering)
Re: the Jetstar incident and accumulation of crystals in the fuel system: I don't think a sample size of one is necessarily representative of all possible failure modes.

For one thing, the mass of salts present seems quite dependent on the magnitude of the error made with the biocide, and isn't specific to biocide at all (a sufficient amount of any stable-enough crystal in the fuel system would do the trick - see e.g. ice crystals in BA 38).

For another, would the increased fuel demand of (near-)full power not cause a blockage by residue to develop quicker? That's not a rhetorical question: I don't know enough about the GEnx-1B's fuel system or these specific magnesium salts to tell if the accretion of crystals would be directly or inversely proportional to the fuel's volumetric flow rate. In the case of BA 38 the fuel-oil heat exchanger blockage only became apparent (or perhaps only developed fully?) when increased thrust was commanded, no? And the thrust on each engine reduced within several seconds of each other - a far cry from the minutes that the Jetstar situation developed over.

I suppose my other question would be what possible sources of chemical contamination there are, apart from water and biocide. I think that for the theory of a quickly-manifesting fuel system blockage to work, it must be something on the microscopic scale (for lack of better phrasing); larger physical debris would surely cause a more externally-spectacular failure than a quiet rollback, and is extremely unlikely to manifest in both engines at anything close to the same time.

Now I'll admit that this is pretty out there as far as speculation goes: any petroleum product can produce flow-inhibiting crystals by itself if it's at a low enough temperature, or at higher temperatures in the presence of a suitable contaminant/gellant. As I understand it the fuel tanks of modern airliners are heated as necessary to prevent the temperature of the fuel from dropping too low. But if that system was malfunctioning or there was an inadvertently introduced gellant in the tanks, could that have resulted in a dangerous buildup of paraffin wax? Unfortunately due to the post crash fire I'm not sure the investigators will be able to collect fuel samples for testing, as was done for BA 38 to rule out fuel waxing...

It has been a week, and the recorders were recovered within two days. Contamination would have been found and almost certainly made public by now. A government statement yesterday asked people not to speculate on sensitive matters and whatever it was appears to need more time and deeper investigation. I am old and patient, so I have no problem with shut up and wait.

Engine failure due to water contamination is surely a different investigation to biocide contamination? I expect they're looking into both, but they're not that closely linked.

Surprising that you can do nearly a minute of takeoff+climbout then fail cleanly and silently within seconds of each other.

I would, of course, presume, that take-off roll performance was within expected limits, otherwise they would have aborted by V1. They reached VR before running totally out of runway, and achieved a short-lasting climb. What one single point of failure occurred very shortly after aircraft went nose-up and would it be possible that the fuel feed in some way affected by virtue of that angle in the context of some failure?

If I may - going back to the upthread report of an Indian Express newspaper interview with "an official" who was pointing at possible "water contamination". This is very misleading by either the "official" or the newspaper. The incident specified by "the official" near Gatwick in 2020 is this one:

https://www.gov.uk/aaib-reports/airc...-february-2020

which was explicitly biocide contamination not water. As in the Japanese similar case discussed here already, the excessive biocide use caused chemical reactions in the fuel that - eventually - caused starvation and abrupt shutdown.

The Japanese incident , discussed already above, has much more detail on how the biocide is used and what happens if it's used excessively.

I do not know how Air India / Boeing / Ahmedabad do their biocide treatment, but it appears generally (from a good number of accident / incident reports) that it is very particular to the given aircraft. Once the desired fuel load level is known, a desired concentration of biocide can be calculated for that fuel load. That biocide is then introduced, via an intermediate little bowser, into the specified quantity of fuel being loaded on the tarmac into the subject aircraft tanks. So, the biocide does its thing in suspension in the regular fuel, as the aircraft operates its route. In a number of cases, orders of magniture more biocide (of which there are various brands) has ended up in the fuel, causing engine shutdowns at very difficult moments.

So, some questions. If the investigators are looking at a biocide contamination:
- after such a fireball, would there be any way of determining whether the fuel had in fact been biocide contaminated? Perhaps the inner surfaces of the tanks? Assorted valves and piping along the fuel route?
- what relevant engine parameters are captured and (hopefully) usefully recorded by the FDRs? A couple of incident reports have mentioned monitoring of the exhaust gases, with an ability to detect contaminants as they are expelled.
- does anyone here know what records are kept regarding the biocide treatment at the point of fuelling? Iirc, in the Japanese incident it was forensic interviews with the ground crew responsible that revealed the details of the error, rather than captured hard data.

Gary Brown Yes that was what I was wondering too. Biocide contamination not water. Hence my earlier curiosity about what might have occurred to the aircraft in the DEL stopover. If the inner surface of just the centre tank somehow got contaminated there, any issues may have been hidden flying with the tank empty and the problem only arose on the subsequent sector when the tank was used.

Why is there still such lengthy discussion over the auto throttle / alt hold theory. For the first time since this awful incident an update seems to have been given (if AH is accurate) suggesting all was normal and the engines just lost power. The fact they\x92re looking closely at the Titan incident at Gatwick is a pretty big suggestion of what their running hypothesis is. If it is another biocide overdose though, wouldn\x92t that require quite a low fuel load before it became apparent? I seem to recall the Titan A321 had flown around a fair bit without issue, it wasn\x92t until they took off with a low fuel load that it all got unpleasant?

Some assumed numbers about normal biotreatment.
https://www.biobor.com/wp-content/up...ation-IATA.pdf

If we assume 50 tonnes fuel load a 100ppmw biotreatment will be 5kg of biocide total in all tanks.

The GEnx-1B will burn about 4,5kg/s fuel each on a take off run (give or take a bit) so 9kg/s in both donks for about 20s until rotate.

So the total nominal biocide dose could be pumped in about half a second through both engines on take off power if it where not mixed at all and arrives in both engines at the same time.

This gives you an idea that with the nominal amount of biocide dose not much could have happened. If biocide is the source of this dual EFATO than an extreme overdose in addition to wrong application preventing mixture with the fuel had to be the case.

This sounds convincing, but I have read the investigation report on Jetstar Airways serious incident (VHVKJ) with great attention, and if I understand it right, things may be a bit more subtle:

First, the problem involves the valves (notably but not exclusively FMV and FSV), not the combustion of the product:
Second, the doses apparently don't need to be that high to result in a problem. A x10 dose seems sufficient:
Third, the main cause of the incident seems to be associated with magnesium salts dissolving in water instead of fuel:
Fourth, and despite the report indicating that ( my bold ) "In this serious incident, it is highly probable that, when the Aircraft was descending for landing, there occurred oscillation in rpm of each engine causing both engines to temporarily fall below idle at separate times because Residue primarily composed of magnesium salts accumulated in spools impeded movement of spools that involved in fuel metering of both engines.", it should be noted that the reported "rpm oscillations" of left and right engines were close to each other in time:



These "rpm oscillations", leading to substantial loss of thrust, could as well have occurred simultaneously, and 81 seconds (for the RH engine) is an awfully long time. According to the report, Kathon FP1.5 is not used anymore for biocide treatment, but another contributor ( nachtmusak , who seems to be a petrol specialist) suggested that other products may have similar effects .

Therefore, regarding the case we are discussing at large (thanks again, mods!), I think we shouldn't overlook the hypothesis of fuel contamination by biocide, since it is a single point of failure (among a very limited number of SPoFs) from a system analysis point of view.