This whole Fungal Growth in Fuel thing.

[Ganyeka]

Firstly, I am not a Pilot. I am a lawyer. That alone may be grounds on which to hang, draw and quarter me. I do have 2 close friends who are Pilots, both with Virgin Blue. I don't know if that helps.

The reason for me posting on this forum is slightly obscure. I have a client who is, amongst other things, an inventor. He is very intelligent, but, how do I say this delicately, he's "unconventional". He recently posted as Fungal Bob in your Tech Forum about fungal growth in fuel and was roundly criticised. I believe his intentions to have been honourable. He isn't trolling or spamming for commercial benefit. He has connected some dots and become concerned by the inferences he has drawn. He does have existing technology that is relevant to fuels and specifically to microbial contamination, hence his interest. He is one of these guys who genuinely wants to help.

I'm trying to get my head around the issue and thought I might humbly seek the views of this Forum's members.

I cannot technically assess the merits of the various arguments but a few things seem clear. At the risk of over-simplification, microbial contamination and fungal growth in aircraft fuel seems well recognized. It's effects are known to be problematic for engines and other parts due to corrosion, blocked filters (and one therefore assumes fuel delivery), wing electrics and structural elements etc. Whilst there seems to be maintenance routines for detection and correction and various additives to combat this microbial contamination, it seems clear that it does, nonetheless, routinely cause both minor and serious safety concerns.

It also seems clear that these procedures for detection, correction, repair and prevention are challenging and frequently expensive. And, as with all of these types of systems and procedures, if they aren't followed properly, or something goes wrong whilst performing them such that they are imperfectly performed, the consequences can be severe.

Any issues so far? I'm just trying to lay some groundwork and establish what my understanding of the situation is.

So if this issue really is as potentially serious as it seems to be, isn't an alternative solution that is basically 100% effective, cheap and essentially permanent something people would be interested in?

I'm just asking. And I am asking genuinely, not as a prelude to a product flog etc. I am just trying to understand the dynamics of the problem and the politics etc surrounding how it is currently handled.

Cheers and Thanks, in anticipation.

[vapilot2004]

I've always been amazed at how something as noxious as jet fuel & kerosene can still manage to support life.

[piggybank]

There are lab checks that can be done and are done to check bulk fuel installations for fungus.

Good care of the tanks of fuel, i.e. ensuring water drain checks are done on a daily basis. Here at my location we fill from tank-tainers containing 20 thousand litres that have been at sea. The fungus and quality lab checks are done on receipt of a new container, before going into bulk storage.

Boron compound treatments have been successful in the past in treating bulk fuel and affected aircraft fuel tanks and for prevention of fungus development.

However, some engine manufacturers have limits of how much boron from these compounds can be tolerated by the turbines of their particular engine during its working life.

[MountainBear]

My problem with the original post is when it uses words like "serious" and "severe". There is no context for evaluation.

If a wing falls off a plane that is a serious and severe problem. Fungi growth in fuel, eh, not so much.

[matkat]

As a maintence engineer I can tell you that regular checks are carried for fungal growth, not only that a chemical (bibor) is also regularly added to the tanks to kill it.

[Meccano]

The microbes can cause damage to the tank Mountainbear. It seems they not only can survive in kerosene - but they also 'eat' aluminium. I know of one B732 back in the early 80's that had to be scrapped because of it (African company).

[Los Endos]

As far as I'm aware many commercial fuels contain additives such as Prist which prevents fungal growth and lowers the temperature at which crystilline icing occurs. If not already present in the fuel it can be added at the point of delivery.

[piggybank]

https://www.corrdefense.org/Academia%20Government%20and%20Industry/06T025.pdf

The above link seems to cover the subject of fuel tanks with fungal activity in the fuel, and as far as I know the fungus only developes at a fuel water interface so you have the one of the ingredients for corrosion right there.

[MountainBear]

The microbes can cause damage to the tank Mountainbear.Since you seemed to have missed my point entirely let me try again.

Link a single accident report anywhere in the world where fungi in the fuel supply--either directly or indirectly--lead to a loss of life.

I know of none. It seems hyperbole to claim that this is a "serious" or "severe" problem from a safety perspective. Even if you want to argue that, left untreated, it would become a safety issue that only speaks to the fact that present methods seem to be taking care of the safety aspect nicely, thank you very much.

None of this should be read to disparage the inventors knowledge. It may be the case that there are real cost saving involved by adopting his product. That amounts to a claim that product X is better than product Y. I don't know enough to judge that claim.

What I do know is that given all the real issues in flight safety--CRM, automation, exploding Rolls Royce engines--attacks by the mutant fungi from outer space are low on the list.

[Ganyeka]

Flight Safety Australia had an article in the September/October 2005 edition called "Attack of the Funghi" which states that the funghi causes the formation of a "gooey matt" which can "cause blocking of the engine fuel feed system". This is unlikely if good maintenance is being performed (a big "if" in many operations and parts of the world), but the article goes on to state that the real problem is "corrosion to the wing structure". This corrosion happens in a number of ways that the article details, such as:


reducing the surface tension of the water so that it spreads into small gaps more effectively;
acid byproducts reacting with the chromate in primer paint turning it into a passive form so it will no longer sacrifice itself to protect the aluminium;
increasing the electrical condictivity of the water allowing electrons to flow more easily, accelerating the oxidation process;
directly attacking aluminium.The article was written by an aeronauical engineer. I would consider this to be "severe".

The rest of the article, about detection and treatment, seems to highlight the risks if vigorous maintenace and correction procedures are not undertaken, and the cost of things like cleaning the tanks. Not to mention the environmental impacts of all of these additives and fuel tank cleaning etc.

And here's the thing from my point of view - it's the Jurrasic Park Principal (don't try to look it up, I made it up) - ie - When human generated complex systems require human delivered complex maintenance, it's a question of WHEN not IF something goes pear-shaped. Therefore, anything that simplifies the maintenance and improves the outcomes reduces risk. And when we're talking about aircraft, we're talking about lives. The risk, specifically, is death. Potentially lots of death.

Problem is there seems to be a lot of vested interests in justifying the status quo and lots of businesses built around airplane fuel additives and such who want to push the line that everything works just fine. So who is going to take a proper, objective look at these issues and consider ALL of the alternatives?

Anyway, now I feel like a conspiracy nut, but with even the mainstream media picking up stories about fuel problems grounding planes and causing issues, it makes me wonder if there isn't a bigger issue here.

[27mm]

IIRC, the RAF had this problem on its Herc fleet some years back; the fungi in question, I believe, was called Cladiosporium Resinae.

[JW411]

Several BAe146s have had to be scrapped because of fungal "rot". The damage was so bad that they were beyond economical repair.

The undersurfaces of the wings of those that were repaired were not a pretty sight either - patches everywhere!

[foxy2600]

Most good airlines subscribe to the IATA fuel quality programme. If the inspections are done correctly, the fuel supplied 'at the pump' could not support CR as the filtering (C Filter) won't allow microbes through and the filter/separators won't allow water through. The problem lies with aircraft stored for any length of time or extended parking. As one contributor said - poor maintenance. Warm moist hi-humidity climates don't help, which it is more prevalent in the tropics. Biobor and regular water drains help. Purging /draining the fuel system doesn't, as the seals and sealant dry up.
Why does it eat untreated aluminium? It grows on the interface of water and JetA1 and then 'clings' to the tank interior as the levels fluctuate. It's kind of plant form which means Carbon in - Oxygen out. Water enriched with oxygen loves untreated aluminium.
Not the same but just as weird is the bottom of a plastic (fibreglass) boat. keep it in the water for three or more years and the gel coat starts to get 'eaten' - so I guess the all plastic aircraft won't be any better either :hmm:

[Grogmonster]

Ganyeka,

I would love to know how your friend can solve this fungus issue. Please tell us?

Groggy

[protectthehornet]

in airline ops it seems that you burn fuel so quickly, on a daily basis there isn't much of a problem...in the US all of our fuel has the additive sometimes known as PRIST.

now, if you got fuel without prist, and it sat in the tank for months at at time you might have a problem...but airliners don't sit (in regular service mind you), they fly, they burn fuel and the fuel is replaced later on.

[Agaricus bisporus]

Ganyeka, I rather think the "problem" already has a solution. "Biobor" is a well known and readily available biocide that is used to combat the growth, any new product will only be a competitor to an already established market leader. (Prist is an anti ice additive, not a biocide)
If operators can't or won't be bothered to keep fuel tanks water free then they are unlikely to bother buying Biobor or any other product, so you won't win there.
It is not a thing I've ever encountered in 25 years flying from equator to almost the arctic circle, so I don't lose too much sleep over it.

the bottom of a plastic (fibreglass) boat. keep it in the water for three or more years and the gel coat starts to get 'eaten'

It does? As a plastic boat owner that's news to me! What happens to gelcoat at three years immersion? All gelcoat? Please tell more.

[411A]

"Biobor" is a well known and readily available biocide that is used to combat the growth, any new product will only be a competitor to an already established market leader.

Indeed so.
The first jet airplane (business jet, anyway) to have these difficulties was the Lockheed JetStar, but fuel additives solved the problems.

I think the original posters friend has a solution looking for a problem...that has been solved already.
IE: a financial dead-end.

[SNS3Guppy]

Ganyeka,

Fuel contamination is always a serious issue. Microbial contamination in fuel is a problem not only in aircraft, but in storage and transport systems, as well Delivery from both storage and transfer systems (trucks, underground delivery and so forth) have filters to prevent passing on contaminates.

Microbes in aircraft fuel cells thrive where water is found. Algae and bacteria becomes a problem if the fuel sits and has water available in the fuel (jet fuel suspends water better than other fuels such as gasoline). In aircraft that are constantly on the go, constantly burning their fuel supply and receiving new fuel, it's seldom an issue at all.

Where fuel contamination does take place from organic developments, the corrosion issues are localized to the algae, and are usually not a problem. You mentioned in your original post issues with corrosion of wing electrical components, and so forth. These have nothing to do with the formation of algae and other contaminants in fuel.

I'm a career aviator. I'm also a career mechanic (engineer, to some here). I've worked extensively inside fuel cells, installing fuel cells, repairing fuel cells, etc. I've been a director of maintenance twice. I've been an inspector in repair stations, a line inspector, and filled other maintenance line, floor, and supervisory duties over the past few decades. Fuel contamination, while most certainly a serious issue, is rarely a problematic issue in that it seldom is seen and seldom rears it's head. It's just not an issue as I've seen it over the years, especially for aircraft that are properly maintained and frequently flown. For aircraft that will be stored for a time it can be an issue, but there are numerous considerations to make that determination, and more importantly, it's something that can be addressed.

Another poster mentioned biobor, which is a "shock treatment" for an existing problem in a fuel cell or system. It's also available for ongoing treatment. The most commonly used treatment is the inclusion of fuel additives such as "Prist" in fuel. These are primarily used to affect the freezing temperature of fuel, but they also serve other functions. Often these additives have or include chemicals which offer antimicrobial properties. They tend to inhibit the growth of microbes.

This corrosion happens in a number of ways that the article details, such as:

1. reducing the surface tension of the water so that it spreads into small gaps more effectively;
2. acid byproducts reacting with the chromate in primer paint turning it into a passive form so it will no longer sacrifice itself to protect the aluminium;
3. increasing the electrical condictivity of the water allowing electrons to flow more easily, accelerating the oxidation process;
4. directly attacking aluminium.

The article was written by an aeronauical engineer. I would consider this to be "severe".


While I'd agree that from your perspective this sounds like a terrible thing, it's not.

Corrosion in aircraft comes from a number of courses, including within the metal itself. Galvanic, intergranular, fretting, electrolytical, and numerous other forms of corrosion occur, to say nothing of fatigue, and other factors which are prime concerns to maintenance personnel. You appear to be envisioning a problem in which microbes are on the verge of causing a wing to fall off. This isn't the case.

Pitting on surfaces, and spots of corrosion in faying (overlapping) surfaces can certainly occur. What we're not seeing out there are hoardes of microbes gnawing their way through wings and the wholesale need for replacing wings and aircraft structures due to microbial infestation. It's just not happening.

The wrong soap used on the outside of an aircraft can cause or accelerate corrosion on an airframe. Paint sometimes sustains corrosion. Corrosion is an ongoing process which does not end, and which is a constant battle (albeit a relatively minor one, in the grand scope of things), with which maintenance personnel must deal. Sometimes addressing corrosion means light surface removal of the corrosion, other times it involves repairs of varying degrees. Often it's little more than prevention, which is nearly always the case with fuel tank contamination by microbes. One tests the fuel, deterines the problem, makes a visual inspection where necessary, treats the fuel, flushes the tanks if absolutely necessary, changes and inspects filters, and moves on. We're talking about routine maintenance issues here...not drama, and not a "severe problem." A routine problem.

[foxy2600]

My boat's over 30 years old now. When she's out of the water the hull gets pressure washed and re-waxed. It's all discoloured and shows signs of pitting, just like the older exterior uPVC panels on my house. All the day-fishers I talk to say algae is the cause - I live in ignorance I guess could be an old wives tale but clean her every 3 years or so regardless.

Found this:
Blister Repair Methods (http://www.ippnet.com/newsletter/44-first-quarter/290-blister-repair-methods.html)

Sure this thread should now be in Tech Log :)

[foxy2600]

Must be a moderator reading my mind:ooh:

[SNS3Guppy]

As the article you linked will note, what you're seeing is delamination...not damage caused by algae or other microbes.

A poor gelcoat (or porous gel coat, as the case may be) can cause this as can pitting and damage in the coat. A properly poured and painted coat should prevent it, but where polyester resins and a gelcoat are used, the aging of the resin, hull (or airframe flexing), and the inevitable cracking of the gelcoat will allow in moisture. It's the moisture that's causing your problem. Not microbes.

An epoxy underlying structure with something other than a polyester coat will make a big difference, but it's more expensive, and not widely used. It's largely used on aircraft, however, where fiberglass and composite structures are involved.

Gelcoat issues are largely cosmetic issues, not structural ones.

These have nothing to do with aircraft fuel tanks, however, as most fuel cells are not fiberglass, nor gen coated on the inside.

[grounded27]

Several BAe146s have had to be scrapped because of fungal "rot". The damage was so bad that they were beyond economical repair.



I do not see how this is a bad thing?

As for fungal growth, there are no cheap installations of any part to modify an aircraft. Whatever this device I guarentee you it will cost allot more than your friend thinks. Airlines and mfgr's will go with conventional methods because they work.

[SNS3Guppy]

Innovation isn't a bad thing, either. We see entire fleets retrofitted with updated panels and avionics. I've seen simple fixes over the years fix known problems; there's no reason to believe that one couldn't come up with a better solution to microbial issues, too.

[PEI_3721]

grounded27; re “I do not see how this is a bad thing?”
I think that the issue is that some operators failed to take precautions against ‘fungal rot’ and inspect the aircraft, to such an extent that they were ‘unrepairable’. This infers that some aircraft had a degraded airworthiness standard, although still safe due to the margins within the airworthiness concept. However, if the situation had been allowed to continue – poor inspections etc, then a safety issue could have arisen.

The cost of biobor additives, fuel analysis checks, and tank inspections are relatively cheap compared with a wing tank repair.

[SNS3Guppy]

I believe that grounded27 was making a tongue-in-cheek observation about the efficacy of the BAE146, not an overall statement on corrosion.

[Section 48 Ace]

For Info Only as I have some interest on this matter.

Cladiosporium Resinae thrives between Jet A1 and Water, water can be held in suspension and distributed throughout Fuel Tank during refuelling or pool and drain towards Weather head after a lenght of time. CR can be found to thrive at any point where moisture can be trapped inside a fuel tank.

Maintenance Manual Procedures state Weather Head draining to be carried out prior to refuelling first flight of the day ( drain the water which has pooled once released from suspension) regular draining post refuelling throughout the day is a token procedure and will collect some water.

The Weather Head is a component and its fastener prevents it from being totally flush from the tank lowest surface so some pooled water always exists.

Regular operations and biobor treatment minimisers CR growth. Dead CR is toxic to aluminium and its protective finish ( fibreglass gell coats as well, then osmosis does the rest of structural damage).

Routine maintenance inspection will purge and evacuate A/C fuel tanks and dead and live CR should be found and removed with any discrepancies.

A/C left idle and exercise low operating hours will have an increase activity and more costly repairs.

So I guess there could be a market for sponge that will purge and evacuate lipids from bacteria killing them with out absorbing fuel. There is one close, for now we are stuck with routine maintenace.

Note: This fuel contamination has increased since Singapore took over Austalia's refining tasks, obviously the product is within limits or is that just a coincidence.

[grounded27]

Yes, as I know it BAE is often referenced as Bring Another Engine.

[OverRun]

Ganyeka: Flight Safety Australia had an article in the September/October 2005 edition called "Attack of the Funghi"
And it is located here:
Attack of the Funghi (http://www.casa.gov.au/wcmswr/_assets/main/fsa/2005/oct/50-51.pdf)

[lederhosen]

I too would have previously discounted the problem. However I know of of this occurring on the NG. It shocked people. As pilot you have no way of visually inspecting the tank at least not easily on the 737. Only when the tank was opened up after some incidents, did the scale of the problem become apparent. I would bet there are a load more reputable airlines that are at risk than you would think.

[DERG]

If it works patent it.

[Ganyeka]

The other issue, apart from the corrosion, seems to be microbial contamination blocking filters and interrupting fuel flow.

Thanks everyone for the time you've taken to clarify some issues and provide your input and experience. My client's technology was not originally designed for application to aircraft. It has arisen out of a product for fuel systems in petrol and diesel automotive engines and storage of fuel for same, but the fungal growth inhibitor aspects of the technology are just as applicable to aircraft and aircraft fuels.

I won't turn this thread into an advertisement by throwing product names around, and the application in this instance really does require a bit of R&D before too much spouting off happens anyway.

I will ask this question however, and perhaps some of you may have some views on it - If a product was available that prevented and killed microbial contamination of fuel and which was cheaper and more effective than current practices, reduced or eliminated the need to flush tanks, had long-lasting effect etc - would it be adopted? Or is this something that is, as someone said, a solution in search of a problem?

How would you go about having it tested and approved for use? Or would it be better to have your own independent tests done and then provide those to the CASA?

Thanks

[DERG]

The rules for aviation fuels are strict. Need to do very thorough research. The big oil companies have done a lot on this subject.

Some refineries have been producing "biofuels" notably in the kero/diesel fraction which has caused concern IF residues enter aircraft tanks/lines. Biofuels promote fungal growth and can change burn times.

Your next step is to investigate the fuel regs. If the civil sector is non responsive (which is my guess) the military sector is the way forward. Notably the USA DoD could well be interested. Most standards in civil use are derived from military demand.

[SNS3Guppy]

I will ask this question however, and perhaps some of you may have some views on it - If a product was available that prevented and killed microbial contamination of fuel and which was cheaper and more effective than current practices, reduced or eliminated the need to flush tanks, had long-lasting effect etc - would it be adopted? Or is this something that is, as someone said, a solution in search of a problem?

The answer to your question largely depends on what it is that you're trying to get approved. "Approval" can take many forms. If you're talking about a fuel additive, it's going to have to meet several tests, including those for fuel specifications and compatibility, as well as the fuel use requirements of every individual aircraft manufacturer, and every individual type design. Current additives, for example, vary in acceptability from manufacturer to manufacturer, but also from airplane to airplane from the same manufacturer. Not all aircraft and not all fuel systems get approval, and not all are compatible with certain fuel additives or fuels. Further, how the additive may affect fuel cost, freezing point, and other properties of the fuel will have a determining effect on it's use in each individual type.

If you're talking about equipment to modify fuel tanks or aircraft, these will require separate approval on each aircraft on which you wish to install the equipment. This approval will come in the form of a supplemental type certificate, which means you're ensuring compatibility of the equipment to the original type certificate (birth certificate, if you will) of the individual airplane. If you're going to get it approved for Boeing products, for example, you're going to need to do separate certification (an extremely involved, complex, and costly process) for every individual type aircraft produced by Boeing on which you wish to gain approval. If it's installed equipment, that is.

The answer to your question, then, may be complex, and really depends on what it is that you're talking about. Rest assured, with aviation, regardless of the nature of the product, the answer won't be simple.

[grounded27]

I will ask this question however, and perhaps some of you may have some views on it - If a product was available that prevented and killed microbial contamination of fuel and which was cheaper and more effective than current practices, reduced or eliminated the need to flush tanks, had long-lasting effect etc - would it be adopted? Or is this something that is, as someone said, a solution in search of a problem?

How would you go about having it tested and approved for use? Or would it be better to have your own independent tests done and then provide those to the CASA?

Thanks

To clarify one thing. Many commercial airliners use devices (usually jet pumps that work on a venturi effect) to circulate fuel disrupting water and biological growth from accumulating for this very reason.

Point is that they are only effective when the aircraft is in operation or electro/mechanical fuel pumps are aiding in their operation. Result is aircraft with higher utilization have cleaner tanks in these aircraft. Does this product work when an aircraft is sitting overnight?

All fuel samples are taken after an aircraft has not been in operation (2 hrs is a good number).

[onetrack]

O.K. I now have a silly question. As I'm not a LAME or even involved with aircraft maintenance, the answer may be simple. However, the question is... if tank corrosion created by CR has created problems in the past... why aren't aircraft tanks coated internally, with some type of epoxy-style coating to prevent corrosion issues? :confused:

[Blacksheep]

I think that the issue is that some operators failed to take precautions against ‘fungal rot’ and inspect the aircraft, to such an extent that they were ‘unrepairable’. I think the answer lies right there in that statement.

The kind of operator that routinely ignores the maintenance schedule and fails to perform the simple tasks that prevent microbiological activity damaging their aircraft beyond economic repair is not going to use any new method of dealing with microbiological contamination either.

The overwhelming majority of operators who comply with the regulations and follow their Approved Maintenance Programme will continue with their present relatively inexpensive precautions against funghi growth and other problems - regular water drain checks, routine "Biobor" treatments and of course, the heavy maintenance tank entry tasks that inspect the internal tank structure for much more than mere evidence of microbiological activity.

why aren't aircraft tanks coated internally, with some type of epoxy-style coating to prevent corrosion issues?Because we'd have to remove it every check cycle to inspect the structure for tiny cracks and those forms of corrosion that occur naturally over time within the structure of the metal. Some aircraft do have removable bladder tanks and these bring their own problems. Keeps us in work. Fixing things is our job. Its what we do.

[CJ Driver]

Ganyeka,

A solution is available that is 100% effective, and that is to mix the fuel with a water dispersant - the best know brand is Prist, but others exist. Prist was designed to stop ice crystals forming in fuel systems, which it achieves by dispersing the water into the fuel so that no ice nuclei form. It has the important side effect that it also completely stops microbial contamination - not, contrary to popular view, because it is a biocide, but by the simple mechanical effect of removing the fuel/water boundary that the bugs need to live on.

You may wonder why Prist is not universally used. Prist costs more than Jet fuel. Even though the concentrations are small (typically 1000:1 mix), by pre-mixing Prist with the fuel you increase the cost by roughly 1 cent per litre. Many small jets and turboprops routinely use Prist in their fuel because they need the anti-ice properties, and they don't use so much fuel that it makes a material difference to their operation. Bulk fuel users - like airlines - find the cost premium to be a problem. Instead they install heat exchangers to solve the ice problem, and rely on utilisation and maintenance programs to solve the bacterial problem.

So if your friend has invented a new additive the target for success is easy - does it cost a lot less than 1c per litre of fuel to deploy it?

[SNS3Guppy]

Let's bear in mind that you're talking about the direct operating cost for fuel as a function of liters or gallons or pounds consumed per hour. This doesn't address an airplane which sits for a period of time, or which has entrained water, or that already has a microbial problem, or that has existing corrosion or other issues related to microbes. Therefore, to say that an innovation must compete with the cost of Prist (or other additives, Prist being but one brand) is somewhat misplaced, though well taken.

One must consider other factors as well. Among them is the obvious: not all aircraft use Prist.

If one were to develop a transmitter, for example, which might be capable of killing microbes, this would certainly have application regardless of whether or not the aircraft or fuel system components is tolerant of biobor, prist, or other fuel additive products. I'm not saying that such an idea would work, but introduce it as a "what-if" example to illustrate the difference between a common fuel additive and a universal solution.

Prist isn't universally used, nor universally usable. It's damaging to some fuel system components and seals, particularly in quantity or improperly mixed, and isn't available in all circumstances. Some operators who use large quantities of fuel and use a lot of it don't include Prist, and not all aircraft approve or utilize it, anyway. Accordingly, one can't necessarily make a reasonable comparison between the potential market for a new product, and the use of an additive such as Prist.

The use of Prist, incidentally, is definitely NOT 100% effective in preventing microbial contamination, nor is it intended for that use. Prist is intended to hep prevent entrained water in fuel from freezing; specifically to prevent it from freezing on filters, valves, etc. Prist, in concentration, can dissolve or damage both fuel bladders, and filters. Where water concentrations occur, Prist will be drawn out of the fuel to combine with the water. In tanks in which condensation becomes a problem, Prist concentrations can settle out of the fuel into the bottom of the tank, along with water, and can reach unacceptable levels, leading to damage of fuel components. This is particularly true for Hi-Flash Prist, which is for use with turbojet aircraft; Prist doesn't recomment it's use for long term storage.

As turbine fuels cool, the entrained (suspended) moisture in the fuel settles out as "free water." The purpose of additives such as Prist is to prevent that water from freezing. This is not the same as preventing the water or absorbing the water, or not allowing the water to become a support for Microbial life. When water is suspended in fuel, it can't be drained out or checked by conventional draining methods, but it can still support microbial growth. Prist does not prevent this from occurring, which is why microbiocidal products such as biobor are used. It should be remembered that while Prist is soluble in water, the same is not true in fuel. Prist is used to lower the freezing point of water.

To go straight to the source on the topic with respect to Prist, visit the Prist Aerospace web site at Questions & Answers: Prist Hi-Flash (http://www.pristaerospace.com/hi-flash/FAQ/index.html#biocidal)

What you'll find is that Prist Aerospace clearly states that they do not claim that their product has microbiocidal or microbiostatic properties, or that it inhibits or retards the growth of microbes.

What biocidal/antifungal properties does the PRIST® Hi-Flash™ Fuel Additive have?

PRIST® Hi-Flash™ Fuel Additive meets ASTM D4171 and MIL-DTL-85470 (Current Revision Issue) specification for DiEthylene Glycol Monomethyl Ether (DiEGME). The primary purpose of this chemical is to prevent freezing of water in the fuel system of aircraft. It is this property that is covered in ASTM and/or Military specifications. Neither of these specifications contains any biocide requirements.

Prior to 1994, PRIST® was made to a Military Standard MIL-I-27686, which specified Ethylene Glycol Monomethyl Ether (EGME). Provisions were made to have this product certified as a pesticide with the EPA. This allowed the product to be advertised as having the ability to retard growth of microbes in aviation fuels. The correct term is for the additive is microbiostat (-stat means it controls or retards growth by putting the microbes in a static condition), it is not a true microbiocide, (-cide means it kills microbes).

With all of the new EPA requirements, it became economically prohibitive to certify the new DiEthylene Glycol Monomethyl Ether, DiEGME based additive as a pesticide. Summarizing the above, it is widely believed that DiEGME does have a retarding effect on microbial growth; however, we no longer officially claim this property for the PRIST® Hi-Flash™ Fuel Additive.

[grounded27]

O.K. I now have a silly question. As I'm not a LAME or even involved with aircraft maintenance, the answer may be simple. However, the question is... if tank corrosion created by CR has created problems in the past... why aren't aircraft tanks coated internally, with some type of epoxy-style coating to prevent corrosion issues?

If maintained properly they are. First is more like a primer or a paint there is also a compund in joints to prevent leakage. The 146 spoken of were probably poorly maintained.

As said before the largest threat is engine fuel filter clogging, the filter will bypass (allthough I have never seen this with microbial) allowing the engine to operate and may eventually (theoreticaly) clog a fuel control unit. Doubtfull because that pressure is often increased by this stage to a much higher pressure.

[SNS3Guppy]

If maintained properly they are. First is more like a primer or a paint there is also a compund in joints to prevent leakage.

Generally fuel cells are not coated, primed, or painted internally. The most common finish in a fuel cell is bare metal, although some systems do use chromate or other coatings. The basic corrosion preventative in aluminum sheeting is alclad, or pure aluminum coating. This is often treated with alodyning or other methods of corrosion prevention, which is really a surface treatment of actual corrosion or oxidization. This surface oxidization prevents further penetration of the metal. It's a very common method of treating the base metal, and in many applications is followed by other treatments such as paint, chromate, etc.

Putting surface treatments inside a fuel cell can have dangerous problems if the treatment becomes free in the fuel. Paint flecks can plug a fuel filter as easily as ice. Very specific sealants are used inside fuel cells, but generally the cell isn't coated internally with paints (epoxy, or otherwise). Where a full surface treatment is required in a cell, sometimes a bladder is used in place of sealants, and the entire fuel cell is lined with a material which is resistant to the fuel, as well as conventional corrosion. One should note that in such cases, often the bladder material isn't resistant to additives such as Prist; the proper mixing and use of those additives is crucial to ensure longevity and proper function of fuel system components.

[Airtanker Pilot]

Sir;
I work for a company in the US which provides fixed wing aircraft support for wildland fire suppresion. We are in the process of transitioning from reciprocating engine aircraft , fueled with aviation gasoline, to a turbine powered aircraft. The microbial problem does not exist in gasoline, so we are facing a new problem.

As you have probably gathered, present methods of combating this problem center around chemical addittives and maintenance actions, also you probably noted that the problem becomes significantly more severe when aircraft spend time in storage status.

As we do not operate our aircraft outside of fire season, and even in fire season we spend significant amounts of time parked waiting for a fire call, we are facing a little different problem than most air carrier aircraft operators. So all of the present practices appear to have some disadvantages for us.

Bottom line is we do not know whether we have a big problem or not, but we surely are interested in anything that can minimize a potential problem.

We will have some peple in Australia in Jan 2011 for simulator training and would appreciate the chance of finding out a little more of what your client may have to offer.

Jim Pape
146 Project Pilot
Minden Air Corp.
2311 P-51 Court
Minden NV 89423
956-342-4871

[grounded27]

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC547198/pdf/applmicro00236-0098.pdf

and this reference is probably as old as your aviation career.

[Ganyeka]

Thanks Jim. I will discuss this with my client and get back to you. I appreciate your interest.

And thanks to everyone else for your views and input as well. This has been hugely helpful and informative.

Regards

Karl

[mustafagander]

This is not a new problem. When I was a new apprentice in the late 1960s the L188 fleet (of a South Pacific operator) had a hell of a problem with the lower wing planks rotting out from this microbial contamination. We were told that the "bugs" lived in the water phase and "ate" the kerosene to live, producing corrosive products as they did so. Our stated strategy was to carry out scrupulous water drains to keep the water phase at a minimum and introduce various (unknown to me) chemicals to aid in killing the bugs.

The end result for this little black duck was that I spent a lot of time inside the tanks grinding off corrosion to the extent that one aircraft had a doubler fitter to the inboard lower wings to make up for the dramatically reduced plank thickness. The rego lent itself to an obvious acronym - XX-ECC, obviously "'ere comes corrosion"!! OTOH, the "tank allowance" and overtime were quite welcome!!

[mustafagander]

mssb etc,

Unless the "gloop" floats on the surface of the fuel, you get it at once because the pick up lines of the bowsers only have a couple of hundred litres under the standpipe to allow for water.

This means that it goes out as fast as it is produced, assuming a reasonable turn over of fuel, so always fill up at a busy fuel supplier.

[DERG]

Don't believe all you read about "German made" automobiles!

True they are big on biofuels on Europe mainland. The problem is when tankers and transit pipes have been used for diesel and then switched to aviation kerosine. That is where the problem lies. Only needs a few spores of this plant life to start a colony inside the airplane tank.

The other issue is rubber attack. The bio content rots rubber.

Love the way these threads go on and on and on!