Question about Oil Filter Caution lights in GA aircraft

[Nikai]

Just wondering whether anyone can tell me a little bit about the function of an 'Oil Filter Caution light' in general aviation aircraft such as a C206.

The flight manual suggests that the light will come on when the filter bypass valve opens but doesn't go into anymore detail than this and unfortunately I don't have access to a copy of the maintenance manual.

I've been told that the light is activated due to pressure differential, and what I am curious about is how critical this type of warning is, whether there is a period where it may still be safe to fly (ie. get it checked within 'X' hours, or whether its a matter of don't fly it until its checked)

I was advised by the engineer who usually looks after the aircraft that the plane wasn't unsafe (via telephone - engineer hadn't seen it since the last check), however another engineer (who I know has significant experience with these engines) mentioned that these warning lights don't often illuminate and if it has it could be a sign of impending trouble and that it should be checked before flying.

I know the other possibility is an electrics fault - and I'm sure this will be checked first - however I am curious how an engineer would recommend a pilot deal with an 'oil filter light' warning.

Background:

Temps & pressures were normal but the engine was only run for a short period of time.
Apparently the light had flickered a few weeks ago but had come on solidly within the last couple of weeks (only flies a few hours a week)
Engine was overhauled a year ago & is still being run on straight oilLook forward to any feedback!

[411A]

•Engine was overhauled a year ago & is still being run on straight oil
That well may be part of the problem.
Lets review, engine overhauled one year ago, and still using non-AD oil.
Not an especially good idea.
So, I would do the following...

Change oil (use Phillips 25W50, is my recommendation), remove and cut open/inspect filter, install new filter, and test run.
Oil light should remain out.

I absolutely would not fly with the present scenario...unless someone was chasing me with a big gun...:uhoh:

[privateer01]

Last time I checked an Engine for a C206 was about $25,000 US.

If the lights on the filter may well be in bypass.....meaning no oil filtration.

So no oil filtration and an unknown reason as to why....might be the filter plugged.....

Like 411A said......Big gun...or perhaps a mortar attack.

I suppose its possible with very little utilization....to be still running straight mineral oil.

[Nikai]

Hi,

Thanks for the feedback so far :ok:

Privateer: the aircraft has had very low utilsation over the last year - however most likely done over 100 hrs.

[Saint Jack]

Nikai: I'm not really a GA type, but for what it's worth:

"...anyone can tell me a little bit about the function of an 'Oil Filter Caution light' in general aviation aircraft such as a C206...." As a general rule, oil filter caution lights (and fuel filter caution lights) indicate an impending by-pass. This gives you time to investigate and rectify the situation before actual by-pass occurs. Check with a knowedgeable engineer or contact the factory for your particular situation.

"...I've been told that the light is activated due to pressure differential..." Correct, a pressure differential switch, and they do occasionally malfunction.

"....and what I am curious about is how critical this type of warning is..." It's very critical. Land as soon as practical and seek technical advice before further flight.

"....and whether there is a period where it may still be safe to fly(ie. get it checked within 'X' hours, or whether its a matter of don't fly it until its checked)..." No, there's no subsequent period during which it's safe to fly, get it checked.

"....I was advised by the engineer who usually looks after the aircraft that the plane wasn't unsafe (via telephone - engineer hadn't seen it since the last check)..." Yes it bloody well is unsafe! He's asking you to fly a single-engine aircraft with an engine oil system caution light illuminated - go figure.

"....however another engineer (who I know has significant experience with these engines) mentioned that these warning lights don't often illuminate and if it has it could be a sign of impending trouble and that it should be checked before flying...." Stick with this engineer, he knows what he is talking about.

"....I know the other possibility is an electrics fault - and I'm sure this will be checked first...." Yes, always go for the simplest potential cause first,

"....however I am curious how an engineer would recommend a pilot deal with an 'oil filter light' warning...." Not really the correct question, the Flight Manual (or equivalent) is the authority for the pilots response to this situation whereas the engine maintenance manual is the authoriy for the engineers investigation and corrective action.

As the engine was overhauled fairly recently, contact the overhauler immediately and explain in detail what is happening and what has been done. Above all, make sure you don't do anything that may invalidate any remaining warranty. Good luck.

[blackhand]

make sure you don't do anything that may invalidate any remaining warranty.

And further to that most excellent advice, do not say anything to the overhaul shop that may allow them to deny warranty.

Cheers
BH

[Nikai]

Thanks all for taking the time to respond!

Part of the reason I was asking was because the flight manual doesn't offer much information about the topic - keen to find out more about how the system works - so thanks for the feedback :ok:

Great advice about the warranty, luckily I don't have to deal with that side of things - but since I'm meant to turn up and fly I'd like to know it's safe (particularly as I'd have other people on board). Seriously wondering whether aircraft utilisation is taking priority over safety... :ugh:

Have just been advised that the oil filter screen has been cleaned, apparently it didn't have engine metal but had carbon from running high cylinder head temps....

[muduckace]

Hell roll the dice on a piston engine, automobiles run thousands of hours withought this warning. I would feel safe going with the manufacturers reccomendations. Play it on the safe side if said engine has a magnetic metal detector it will reveal the condition of the engine, nothing larger than a muddy consistancy of metal is normal wear, change the filter and keep on trucking. Other instruments such as your oil pressure guage are what you should monitor during your inflight D indication.

[Saint Jack]

Nikai: Happy to be able to help, reference your statement;

"....Part of the reason I was asking was because the flight manual doesn't offer much information about the topic - keen to find out more about how the system works..."

Yes, flight manuals for smaller aircraft can be notoriously brief and it's very commendable that you want to know more about how the aircraft and systems 'work'.

A suggestion - the next time the aircraft is in the hangar for maintenance go along and talk to the mechanic/s. Most will be more than happy to explain the theory and practical aspects of the aircraft systems to you. As a minimum, I suggest you get to know all the "why's and where-for's" of the cockpit and instrument panel switches, indicators, selectors, caution/warning lights etc. etc. Rest assured, a thorough technical grasp of your aircraft WILL get you out of a sticky situation one day.