Glass type fuel filters - Please take note

[Duck Rogers]

Alright guys and dolls....listen up and pay attention.

After reading John's last post regarding the glass type fuel filter, I thought I had better obtain some unbiased opinion. After consulting with my friends in the USA, who, by the way are some of the most well known and well respected Rotax servicemen over there, I have come to the conclusion that even though some, or most of us, have never had a problem with the glass type fuel filter, we better take note of the fact that there is definitely something not too lekker with these things.

Here is what Mark Smith had to say:

"There is always something different that attracts some folks attention.

The Pteradactyl was once said to fly really bad, and it did so with full personal knowledge.

But some folks love it even though they may admit, or not, that it does
indeed fly badly.

Same with this glass filter.......It sounds good, replaceable element, cleanable, etc,

but it is bad news in my opinion.

A friend bought a used Rans S9, nice little thing but a bit underpowered with a 503.....

His first attempt at flight could have been a total of the plane as the
engine quit at a most inopportune time.........
he made it down in a sloped field across the road........

The filter was fully plugged and I tested it with a can of fuel and
gravity flow.....very small trickle at best.

I have seen other examples of this filter where they have come apart
inside and leaked, etc,

the best is a cheap, 2 dollars or so, paper filter to be replaced every
100 hours......it is clear to see major crud, and it will also show water if it gets that far,

my Quicksilver types have a loop of fuel line and two low points that connect with it, this traps any water for the most part,

I have removed many of the glass fliters from customer's planes and have a good reputation for continued good performance using the small paper pastic filters......

hope this helps...."

AND

This is what Brian McCallen had to say:

"Never heard of any problems with the Rotax engines on aircraft here in the states but I have heard of problems on snowmobiles. The problem was not that the filters were so fine that any they would clog up easy. The problem was the filter screen was so fine and the fuel consumption so high the filters would restrict the fuel flow. That may be the reason some of the microlighters are able to restart the engine after they successfully do their dead stick landing.
Now we have had problems with the paper type filters also restricting fuel flow when there is water in the fuel the paper will swell up and restrict fuel flow.
Now I noticed some of the microlighters say they have never had a problem. It could be in the way the fuel system is installed on that particular aircraft. If the fuel pump is located much higher than the fuel tank this may not allow the fuel pump to draw enough fuel through the filter to keep up with the engine demand because it is already working hard to just draw the fuel from the tank. Maybe their fuel pump does not need to work as hard to supply the required fuel at the higher RPM's because of where it is located in the system.
Just my opinion."

So, there you have it.......you can draw your own conclusions from the above.

Let it be known that the Duck has moved closer to the John Young camp of thought but will reserve judgement until further investigation........

[Duck Rogers]

Further to my previous post, I have had a lekker long discussion with John Young about this and we both feel that there are too many unanswered questions for us to make a definite judgement on this one.

For instance, we don't know the fuel system set-ups of the planes that have had engine outs. Were the fuel pumps above, level or below the fuel filters. Were the fuel pumps dodgey to start off with? Perhaps not working too well? Did every fuel filter have an identical sized mesh element or are there different sizes available?

As John pointed out to me, the filters he has seen are all made in China.....what are the tolerances like in their manufacturing process?

The filters that I have previously imported are all made in the US. Is there perhaps a difference?

I would haste to add that there are a number of us at my field that fly these filters and none of us have had an engine out with it. Then again, all our installations are identical......

In conclusion, you are all welcome to install whatever you fancy on your planes. The technical guys on the forum will continue to provide answers to the best of our knowledge but please, let sound judgement prevail. You are, after all, responsible for your own actions.

[Ian]

I was told by a very reputable AMO that you never use a paper filter if you pre mix your oil and fuel.....
the oil clogs up the paper, then no fuel flow..

[Duck Rogers]

the oil clogs up the paper, then no fuel flow..

Correct.
Sorry, should have clarified. I did raise the issue. They only mention water in the fuel 'cos most their installations have the oil injection pump fitted.

[John Young]

Correct.

Agreed.

Regards
John ZU-CIB

[Morph]

I was told by a very reputable AMO that you never use a paper filter if you pre mix your oil and fuel.....
the oil clogs up the paper, then no fuel flow..

Imfriggenpossible, The ratio of oil to fuel is 50 to one. I phoned the product manager at GUD and he told me in no uncertain terms that your average paper filter, as used in all cars can/will never ever block the oil. They guarantee it. I used paper filters for over 100 hours on a premixed 503 and never had a single problem. If this logic was true I would eventually have ended up with 5 liters of oil one side and nothing the other.

What is a risk with paper filters is water. If they take in any water the paper filiment will swell and this could cause problems. If your plane is still running at that time, since water does not burn as well as fuel, the swollen filter will starve the already dead engine of fuel.

GUD do not recommend these filters to be used at all in any form of aviation since they do not need any litagation against them. I have seen and still continue to see many many 4-stroke planes with these filters and no problems. Even though the risks are the same wrt water.

Duck my mate

After 11 instances in the good old SA telling how bad these glass filters are you still disbelieve us untill you read two similar instances in the US where there have been problems. Now obviously there is credibility to this case and you have changed your mind. Why didn't you believe the original 11 experienced pilots here.


Take your chances, I am one of those who had in my entire 180 hours flying 1 bad instance and it was related to that damn filter. They say a 2 stroke engine is unreliable, not so, it's the fuel filter.

[John Young]

Imfriggenpossible, The ratio of oil to fuel is 50 to one. I .....

Hi Guys,

My Rotax manual quite clearly states “Paper filters must not be used”.

Morph – about your very sensible logic regarding 50:1 etc. Oil can choke the paper filter, but allow enough premix through at normal cruise throttle settings. But, when you need a “good squirt” for full throttle, the premix could be diluted [more fuel & less oil].

Even with oil injection, I will not use a paper filter.

Regards to all
John ZU-CIB

[Arnulf]

My Rotax manual quite clearly states “Paper filters must not be used”.

But then its easy. The manufacturer knows best.

Regards,
Arnulf

[Tailspin]

Guys you are beating an already dead hoarse
Although there has been evidance that the glass filter is at fault, it has also been proven that with the correct filter insert it works fine. Same as the two stroke motor, if you put the wrong mix in you gonna get the wrong output. I would say use common sense if you have a glass filter and you are not happy with it change it same with a GUD paper filter, remember you are the PILOT and you are responsable for your own safety and the safe operation of your aircraft, i would rather put in a filter that i know works and that i feel good about then have a filter in that in the back of my mind i am saying all the time when is this @#$%^* motor going to quit on me cos that filter is not really the right one ....... instead of flying and knowing all is cool

Just my 2c worth.
Sorry work and "other" problems just making me want to BITCH slap somebody !

[John Young]

Although there has been evidance that the glass filter is at fault, it has also been proven that with the correct filter insert it works fine.

Sorry work and "other" problems just making me want to BITCH slap somebody !

Hi Tailspin,

The sinister aspect is that you will not be able to identify the correct insert – to the naked eye, they will look the same.

This “new swing” on the thread is aimed at paper filters.

Agreed that PIC decides, but if the PIC is not informed nor given an option, on what basis will he / she decide?

Sure hope your day improves.

Regards
John ZU-CIB

[Tailspin]

Sorry Guys
Batteling two years to get my "OWN" aircraft into the air and just not getting any joy. Starting to want to just toss it all away and give everything up completely.

My temper should not be a factor here.

AGAIN I AM SORRY

[John Young]

AGAIN I AM SORRY

Don’t be – no offence taken anyway. But still, not as sorry as we will be when the ruffled feathered Quack reads below – Oh boy, time to switch off cell phone, hide under the bed with a bedpan on my head …

After 11 instances in the good old SA telling how bad these glass filters are you still disbelieve us until you read two similar instances in the US where there have been problems. Now obviously there is credibility to this case and you have changed your mind. Why didn't you believe the original 11 experienced pilots here?

Feathers will fly before midnight ….

Regards
John ZU-CIB

[KFA]

Hi guys we had a post a while back on this topic. The mercedez benz filter that whent out of production is still been manufactured by GUD it is called a BC 68 and looks and works exactly the same as the merc part. I have been using them for 3 years without even a cough. They are available from most autozone shops whil try and post a pic now.

[KFA]

Pic's

[Peter Wolf]

I've been using Mecedes Diesel filters for the past 9 years on my Challenger without a problem.