In my 21 years of TB20 ownership I have never seen anything whatsoever in any filters – except the oil filter which gets a fair bit of soot. That one, and the strainer at the bottom of the crankcase, are important engine inspection points and I would never suggest not doing those.
But what about all the others? Has anyone ever found anything in those?
On the TB20 there are four air system filters (which have never had the smallest spec in them even after this) which cost about €300 from Socata or about £100 from LAS Aerospace as standard GA parts. These are known to be generally good for 10-20 years. They tend to look like this
and their prices have been going up a lot; the metal ones are over £50 each.
Then there is the BA7112 front engine air intake filter which can get dirty but in clean conditions will easily do a few years. But at £15 it is so cheap it is not worth the worry.
The “best gift from Socata”, not repeated by the US makes AFAIK, is the main fuel filter N7284526357 which looks like this
and is reportedly now approaching 1k; under EASA it is inspected annually and per the MM is replaced every couple of years or so. It is made in France, was €175 in 2013, one of the French companies is now US owned but good luck finding the OEM part in small quantities. Also a replacement of such a filter is totally pointless.
On an N-reg you can inspect as required. Even the metal cased ones can be borescoped. But if you open one up, you find nothing in it. And one of them is only for protection from a disintegrating vacuum pump blowing back carbon fragments into the instruments.
I have already taken one step – to eliminate the oil filter by installing the STCd Challenger one.
A search on Knots2U shows Challenger (K&N) cloth reusable air filters which advertise 2-4hp or 0.3-0.5gph gain for various models (I can only find TB9/10 from Socata). Considerably more expensive than paper though.
I bought the K&N filter some years ago. It does nothing. The MP drop due to the front air filter is tiny. This
It also didn’t fit because whoever got the STC didn’t realise different TB models have different cowling etc dimensions. One could have “bent it about a bit” to make it fit but I didn’t bother due to the low cost of the foam filter.
Peter wrote:
I bought the K&N filter some years ago. It does nothing. The MP drop due to the front air filter is tiny.
If you really want to filter dirt, K&N filters are horrible. If just want to have a filter to keep big stuff out, like birds and insects, a K&N will be ok.
Then there is the BA7112 front engine air intake filter which can get dirty but in clean conditions will easily do a few years. But at £15 it is so cheap it is not worth the worry.
Yes, many people and planes use Brackett air filters, enough that they seem almost universal. The Brackett STC for those models with which I’m familiar requires replacement of the element every 100 hrs or one year. It’s a total rip off at $20 or something for a small piece of closed cell foam sheet, but it’s not enough to affect your maintenance cost significantly. The perfect legally enforced revenue stream for Brackett 
If the filter is under an STC then one has to follow the STC… but how many are?
This is the Socata Annual parts kit and those OEM P/Ns appear to be authorised
Re the o-rings, that is another overinflated area. The OEM part numbers for these are kept “secret” even on the US Socata owner group but most are both standard parts and are identifiable from the package markings once you buy one from Socata. Most are Le Bozec or similar but are actually generic parts. I found a number of identical parts (mostly the parts which Socata actually use) which I list here. Thread name changed to include o-rings… I would think o-rings might be more problematic because filters can be inspected whereas a small crack in an o-ring might be missed. OTOH o-rings are normally held in position when the thing is assembled. And they don’t cost much – maybe €100. One of those on the list is a metal ring which lasts for ever…
eurogaguest1980 wrote:
If you really want to filter dirt, K&N filters are horrible.
K&N air filters require periodic maintenance: cleaning and oiling.
I’m surprised to hear that a properly maintained K&N air filter would be horrible
It’s a standard equipment in RV14 firewall forward kit.
Look at it this way. The engine in a SEP keeps you alive. All other factors excluded, common sense dictates that the engine should be in top shape. Which other things can help you stay alive if the engine stops:
If you have none of those, then more importance goes to keeping the engine in top shape. If there were no cost associated with it, it would be a no brainer. The problem is the associated cost, not whether or not all details of maintenance is necessary or not. When there is money to be made, it’s fair to assume people will try to maximize the profit, and in particular when the competition is less than ideal, the market is tiny, and people are afraid to do something “wrong” (wrong, not because it increases the technical probability of engine failure, but because of rules and regulations. Most people don’t know the difference, and couldn’t care less).
IMO, yes it’s definitely a money making con. The reason is because it’s possible, straight forward, low hanging fruit due to rules and regulations. The necessity from a technical point of view is minimal at best, but it’s also the case that every little probability of failure adds up to the total. There is no way of minimizing the probability without going into the details. My point is that the money making part of it has very little to do with the technical aspects, but everything to do with the environment made by rules and regulations. The technical part is as expected regardless, even if it can be a bit on the extreme side and more about “feel good” than actually about real world probabilities and risk. It’s a bit like women and dressing. No one sees their luxury underwear under the brand new fancy dress, but it’s super important nonetheless Also a money making con btw
The main driver is that 25% of 100 quid a year is a lot more than 25% of 25 quid a year which is a lot more than 25% of 25 quid every 5 years
And nearly all owners of certified planes use a company for everything including 50hr checks. So not only do they have to do what the company wants to do but they pay 2x more because they use a company.
Ecologically it is dumb to be chucking out so much stuff.
Peter wrote:
The main driver is that 25% of 100 quid a year is a lot more than 25% of 25 quid a year which is a lot more than 25% of 25 quid every 5 years
Yes, but tell me on what planet a simple mass produced fuel filter cost €1k to produce, package and sell? A fuel filter like that costs max €10, and that includes QA filtering out the slightly bad (but perfectly operational) ones. You would probably pay €30-50 in normal circumstances, max, which already is 3-500% more than production costs. Certified GA is a separate and detached economy, not all that different from military economy. It’s not governed by supply and demand, but “must have” (due to various reasons) and the willingness in the market to pay whatever is asked.
This is very different than for instance musical instruments, or sport equipment. Those things can also have insane price tags. Bicycles for instance. You can get dirt cheap ones, but also very expensive ones. In general though, the quality will increase up to say €3k. More expensive bikes are not of higher quality. You can easily pay €30k for a bike, and what do you pay for? Mostly it is reduced weight, a few grams here and there, and it could be tailor made instead of standard size. The improvement is infinitesimal, but measurable, and there is a psychological factor there as well which cannot be disregarded.
None of this exists in certified GA. There are no super duper, high quality fuel filters Yet, people pay insane prices for them. Certified means standardized, which means there is nothing special. Everything is standard.
