PA-30 Sump Drain - A Thought

[Frank Brunot]

I recently had a bout with water and rust contamination in both my electric fuel pump and fuel servo. The pump had to be replaced and the servo repaired.

The side with the contamination (left) has a METAL sump screen (filter), while the other (right) side has the nylon filter. When the left sump cover and metal filter was pulled, the steel part of the filter was rusted! When removing the sump cover, more water and rust was found. Now I drain the sumps BOTH before and after a flight. So I had to ask myself "What the heck is going on?".

In looking at the sump cover, with the drain tube coming out the side, it dawned on me that draining the sump really DOESN'T drain the sump, just the TOP HALF of it! The bottom half, below the level of the drain tube, NEVER gets drained until the cover is removed.

So my engineering brain has to ask: Has anyone ever made a cover with the drain on the BOTTOM, so when the sump is drained, ALL of it is drained? Making one would be fairly simple, just turned from a round aluminum billet.

If anyone knows where to find such a thing, I'd like a couple.

And yes, I know I could replace the metal screen with a nylon screen, but at $800 each from Webco, no thanks!

[N3322G]

Haven't heard on one but also follow SB that says drain before 1st flight and after last every day. 50 AD takes care of the rest. Oh and over time have replaced all fuel storage and transport components from bladder to engines etc.

[Frank Brunot]

But the point is that "draining" the sump really DOESN'T drain everything bad. It only gets HALF of it. Water and rust still remain in the BOTTOM of the cover, BELOW the drain tube.

[N3322G]

Yup - get the partial drain - the ADs job is to clean it out every 50 hrs.

I like your idea better but no means to implement from my end.

[Kristin Winter]

I am not sure I understand what you mean by the fuel selector sump draining from the side. On all the ones I have seen, they have a stainless steel bowl that drains from the bottom of the bowl. Admittedly, the tube goes off to the side, but the drain point is from the bottom of the sump bowl.

Rust has probably eaten through the Cad plating on the fuel selector. You can send to Webco and they will re-plate it, replace the o-rings, etc, and send it back looking much better.

[Frank Brunot]

Thanks. I'll call Webco and see if they have the bottom drain covers, as well as the replating.

[Charles Schefer]

Frank,

Not trying to hijack your thread but - just a quick comment on the subject of "plating". I did extensive research on this early this year when I did my landing gear overhaul project because I decided to cad plate all the steel parts of my PA-30 landing gear. There's a lot of stuff out there called "cad plated" which is actually zinc plated. Any cad plate hardware (nuts / bolts) you buy from a reputable supplier in the aerospace industry (Webco, Spruce, et all included) should be actual cad plate. However when it comes to other components (e.g. fuel bowls) that are sent to a plating shop - you need to ask if it is really cad plating. Don't ask the middle-man, call the actual plating facility.

Most people look at bolts and other components and if they are nice and golden color (like you see in your local hardware store) they think they are cad plated. Not so... the outer golden coating is called Gold Chromate. It's a chromate conversion coating (hexavalent chromium) that's put on top of either the cad or zinc plate to protect the cad or zinc. The actual cad plate underneath is a bluish-white colored metal that serves as a sacrificial layer. It acts as an anode and attracts oxidation away from the steel that it protects. So... the steel is protected by either cad or zinc plate and then the gold chromate further protects the cad or zinc, plus it looks nice with that pretty golden color.

Cad and Zinc plate are both good forms or protecting steel but cad is MUCH MUCH more durable than the zinc. That said cad is getting VERY hard to find due to increasingly stringent EPA requirements. Cad plating is done by immersing the steel part in a vat of cyanide-cadmium and electrically bonding the cadmium to the steel (i.e. plating). It's extremely toxic stuff and very few places do it anymore. In fact the vast majority of the plating shops I called would not do cad. Finally I found a few facilities that did actual cad plating and that's where I took my steel gear components for cad / gold chromate. Once you see a golden colored component you can't tell if it's zinc or cad underneath unless you really know what you're looking for.

During my gear project when I was trying to find a cad plater; number of people and very reputable aerospace facilities who told me they sent stuff out for cad plating - when I called the actual plating facility, they told me they (the plating facility) only did zinc! So my point in all this is just be clear about what you are getting if your aim is to get your fuel bowls re-plated. Zinc is not per-se a bad way to go, it's just nowhere near as durable or long lasting as Cad.

- Charles

[Frank Brunot]

Thanks, Charles. I'm glad you jumped in. That info is VERY useful!

On another note, I did call Webco, and have ordered two STAINLESS STEEL sump covers, with a concave bottom that drains from the bottom! I promised Phil that when they arrive, I'll take (and post) pictures of what is on the plane now, and what the new ones look like.

Now I'm wondering where the ones I have came from, and if they're legal? Do we have a problem with counterfeit Comanche parts?

More to come.

[Kristin Winter]

The fuel selectors originally came with a cad-plated steel bowl. I think that there was an AD, or maybe just a SB, to replace these with the stainless bowls. I have never seen an original as almost all have been replaced.

[Frank Brunot]

You're right, Kristin. It was Service Letter 589, applicable to PA-30's, S/N 30-1 to 30-1744.

Since my S/N is above that, somehow the older covers got installed on my bird.

Piper sold them as Kit No. 757-187 to comply with the SL. Webco sells the newer covers for $100 each. I also found another vendor online who sells them for $60 each.

New ones arrive today from Webco, and will get them installed ASAP!