[GMAs]

Just finished reading about another plane that went down... why.. because the owner/operator assisted maintance... seems he took the gas strainer appart and with out anyones help put it back in with the old parts... got into the mess of bending up his plane... and now wants to sue the mechanic for not helping him do it right... Hmmmmmm.... seems to me that he took it apart and put it back togeather... all by himself... it it had worked would he have paid the mechanic for the work he did... nope.. so why should the mechanic be responsable for his errors... after all he didn't charge him for it.. ..

But, thats not our intent here.. to find blame over who did what...

INstead we want to look at the strainer again... and take a good look at the gaskets or O rings... here we NEVER...NEVER... EVER.. USE THE SAME old O RINGS... do we... we always put in new ones for the cup and tube... when we pull it to inspect for items in the bottom of the cup...

DO WE HAVE TO PULL THE TUBE... no.. not if the screen looks good and their is no corrosion around the fuel inlet tube where it contacts the brass screen... and yes we can look both inside the inlet tube with a flashlight on the outside... to see if it has holes where it is in contact with the screen... if the fuel system is clean you should not have any rocks or small children stuck in the screen....

SO WHICH O RINGS HAVE TO BE WHAT.... well the big one at the top of the cup.. where it seals and the bottom of the cup where it goes around the drain tube.... are all we need for the inspection time... if their are no stains on anything else... where shafts come thru then we are in good shape and the overhaul of the unit is not needed unless it is over 3 years old...

SO HOW DO YOU PUT THESE GASKETS BACK IN... well more the question how to get them out... here we use a dental pick.. ya if you go to the dentist you might ask him to give you some of the old ones that he is throwing away.... lucky I have a brother who we put through dental school.. who keeps me supplied with all kinds of neet picks... but,....

what if you don't have either... well you can use a piece of dike cut off safety wire.. yep the old 0.032 blood maker... has a real sharp end on it... take the needle nose plyers and make a little hook.. about 1/8 inch long.. press it up into the old O ring and hook it... then remove it... simple huh... well.... for some at least...

Do the same with the small O ring that was under the compression washer which was under the tension nut... and discard them both AFTER you have checked the size against the new ones... is what you want to do... the old ones should be a little bigger in size.. because they expand with the solvents in the avgas... but, they should look about the same...

SO HOW DO WE PUT THE NEW ONES IN.... ahhhhh here is where paying the mechanic is the trick... well it can get frustrating to put the big one in.. only to have it fall out or get trapped when you put the cup back up over the tube (or try to...)

Here is the trick... put oil (engine) like the service manual says... all over the big gasket... stuff it in the land that its supposed to go into...(the oil will cause it to expand a little... so don't have any wrinkles)... or it will leak... then put the cup over the drain tube without the other o ring... or washer... take those oily fingers .. the ones that you lubed the big O ring with.. and lube the drain tube bottom and threads... and now with one hand holding the cup just slightly away from the upper o ring... put the bottom O ring on... and then after you cleared the thread.. (some cover the threads with a piece of real thin heat shrink tubing... with out the heat)...slide it up into the bottom of the cup... and use your thumbnail or some other flat soft object...to force it into the land...and then push the whole thing up so it will go up and lock in place with the bottom O ring holding on if not too much pressure is required... remove the plastic sleave (heat shrink tubing)... and put the compression gasket on making sure the lip goes up on the inside bottom of the cup.... then the nut and thread it up... at this point some mechanics slide the cup around so that they make sure it is not trapped with a twist... if it looks and feels right.. then they tighten up the nut on the drain tube...

OK.. WE GOT HERE....NOW WHAT...
Well we have to torque the nut on the drain tube... so that the cup will seal well up at the top.. while not overtightening it to the point that we strech (lengthen) the drain tube... how much is enough... see service manual for specs.. as cessna made it.. they have the specs for it...

Once tightend... turn on the fuel... have someone grab the drain pull and open it...so that you get rid of the air in the strainer and lines...then stop and check for leaks... and just because you don't see any.. doesn't mean that its not leaking air in... remember they are at the bottom... and any fuel that is drawn thru (suction) will also have a tendency to pull air... and giving you all kinds of symptoms that you don't want... so what we do is on the fwd one.. turn on the boost pump... mixure off... throttle off... run it for a few seconds... and then look for leaking or sweating... as the pump is behind it.. and on the rear... well we pump that one up too.. but, with the throttle and mixture open... so it forces the air thru... listen for the pump to load up... and indicate fuel pressure...and then let it come back down.. looking for wetness...

IF NO WETNESS IS FOUND.... then we get the safety wire out and with a 1/4 tightening turn around the cup twist.. fasten it from the little hole on the mount ear of the strainer... (hint.. put the safety wire on top first... before re-assembly... its easier... smile) to the hole in the nut on the bottom of the drain tube.... put a roll in the safety wire end.. so it doesn't bite you later... and attach the overboard vent line... and again only torque the nut per specs... here we can look in our 43.13... for hydralic line fitting tighteness or check the manufactures spec in the service manual...

ARE WE DONE YET..... NOPE... WE WANT TO CHECK IT A COUPLE OF MORE TIMES FOR SWEATING OR LEAKING... AND THEN AFTER each flight.... for a couple more times.... IF YOU SEE ANY DYE MARKER STAINS... which is in the fuel.. like green or blueish color.... around the cup or top of the strainer... guess what you have to do... yep.. you get to do it all over again... because you have a leak... and a failure somewhere in the unit...

OH AND FOR THE OVER the hill 5 YEAR CLUB...you want to remove the unit... totally when you overhaul it... ya its a bear.. especially the rear one unless you take the rear bottom pan of the back of the plane... all them screws... makes it real easy to get to...however the fwd one....to get the safety wire back on the bolts which hold it on...is really dificult... but, just be patent it does work... and overhaul ALL the O rings...

AND WHAT IF I DON'T.... well ever had that lean engine feeling... on take off... or at altitude the engine keeps quitting... runing hot or just peforming like you have a miss... or bad spark plug... or you smell fuel down between you toes... and wonder what it would be like to have it light up.... I once had a picture that someone took of a plane coming out of the sky... luckly it wasn't a skymaster... that had a fuel leak... and it looked like a roman candle flair.... and when it crashed... looked like a minature nuke... oh and the pilot and his girl friend were wearing parashutes as it was a homebuilt... but, the fabric caught on fire... when it opened... and let them free fall all the way down... something that I don't think would be fun.. and runin your whole day....

SO.... do a good job.. have your mechanic check it out if your not comfortable... and keep checking for leaks on your pre-flight as well as a (ahem...) post flight ..... because if it leaks.. you could be sucking air and we all know that a engine that doesn't have fuel can make you a dead sucker.... but, remember when you hit the boost pump on the fwd eigne it will be putting fuel where you don't want it... and on the rear... well it just grabs more air... so how is your single engine abilities... smile... GMAs... fly safe