This whole Fungal Growth in Fuel thing.
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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.
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.
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Several BAe146s have had to be scrapped because of fungal "rot". The damage was so bad that they were beyond economical repair.
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.
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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.
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.
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.
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Cladiosporium Resinae issue
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.
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.
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Ganyeka: Flight Safety Australia had an article in the September/October 2005 edition called "Attack of the Funghi"
Attack of the Funghi
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.
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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
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
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Certification
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.
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.
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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?
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.
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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
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
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).
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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? 
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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’.
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?
Last edited by Blacksheep; 26th Nov 2010 at 13:18.
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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?
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?
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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
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.
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
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.
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.
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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?
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.
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If maintained properly they are. First is more like a primer or a paint there is also a compund in joints to prevent leakage.
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.