Piper PA-23 Drain Valve STC

For years the FAA has tried to resolve the sometimes-exaggerated issue of trapped water in the Piper PA-23 series fuel system. Many believe, as we do, that maintenance of the gaskets and cap seals in addition to proper sumping eliminates the main source of these problems. The safety record of these aircraft shows if properly maintained there really isn't a problem. HOWEVER... it is proven trapped water can and does occur at attitudes other than level or near level. This concerns the rule makers and so there is a Notice of Proposed Rule Making for a possible Airworthiness Directive requiring corrective action. Two solutions have been offered.

First a return of a rescinded AD with a slight twist. AD 90-23-18 R1 originally called for cementing a rubber wedge inside the inboard aft corner of each fuel cell. The result was a corner that trapped more water than a normal one. This time the wedge is to be installed outside the cell in the same corner. There are two basic problems with this. The wedge displaces some of the space for the fuel cell creating a wrinkle in the vertical edge of the corner. Chaffing and flexing will result in leaks down the road. The other problem is that it still doesn't get the water out of the system at the normal collecting point.

The second solution would be to install a nipple and flush drain valve at the low point. Almost all other aircraft have this feature and it works! Both solutions require the cell to be removed or nearly so for installation. The proposed costs are nearly the same. So if you were required to comply, which one would you prefer?

We acquired this STC for installing drain valves in 1998 and have upgraded it to use our popular stainless steel valve. Now you can purchase the STC kit and have the fuel cell modified or replaced all at one facility.

Benefits include
Durability
Stainless steel construction

FAA approvals
TSO - C76
STC - SA01237AT
• View STC eligibility listing
• View photos

Improved sumping
A drain valve is installed at the low point in the inboard aft corner of the fuel cell allowing for a more thorough sump.

Clean Look
A large stainless steel washer supports the installation and protects the wing skin.

Simple maintenance
Once installed, you can; drain the cell, clean the valve, or change the standard o-ring without removing the valve and disturbing the fuel cell.

Recommended by
Owners, Piper & Apache Associations, IA & A&P’s