What is required to examine my fuel strainer? It is on the Annual Inspection checklist, but it doesn’t appear to have ever been apart.
It depends on what strainer you have. This FAQ will be updated later for the very earliest airframes. Most of the airframes from the 70’s onward used the Gerdes A1540-4. This unit consists of the drain, a NAS1523AA3R Stat-O-Seal (for the drain valve), a lower plate (sealed by an O-ring), the body, (sealed by another O-ring), the A1588 filter screen, and the upper housing. The MS29513-132 O-rings are a standard but uncommonly-stocked size; they are a large diameter ring having a small cross-section. Make sure you have them on hand prior to disassembly, as they may take some time to obtain by mail.
If you have a very late drain valve, it may be the flush style that uses a different lower seal (I will update this later to reflect the drains themselves).
Note that the filter screens are sometimes found missing. They are easily damaged, and some have apparently been omitted during reassembly, which negates most of the purpose of the gascolator (to remove water and debris). The filter screen is of a very fine mesh that will normally block water due to its higher surface tension. If it is missing, you have no filtering function; and you are dependent on the water just settling out so you can remove it through sumping. That won’t help much in flight!
A1588A Filter screen
MS29513-132 Gascolator bowl O-ring (top and bottom)
NAS1598-3R Gascolator bolt sealing washer; alternate number is
NAS1598-D3R (not used with later-model flush drain valve). These
are “Stat-O-Seals”; the superceding part number is NAS1523AA3R.