1) Hydraulic Filter Screens

(0-2 and 337) HE1649-1

Have you or your A&P inspected and/or replaced the landing gear hydraulic filter screen (p/n HE1649-1)? There is a very fine mesh screen in the landing gear hydraulic system that can get clogged after many years of service, Cessna recommends they be removed and cleaned/or replaced at each 100 hr inspection. This fine mesh screen filters hydraulic fluid before it enters the power pack and the system contains a bypass valve which will open and supply unfiltered fluid if the screen becomes clogged. It’s possible that unfiltered fluid could cause wear and/or malfunctions within the power pack, in all other hydraulic actuators and possible landing gear operational problems and/or failure. We have seen this filter screen on 337 and 0-2A aircraft completely clogged. It appears that this maintenance issues has been ignored on many Skymaster aircraft and I suspect the reason is that Cessna does not have nor has had any of the filter screens in stock, but we have them in stock. As Skymaster aircraft continue to age, clogging of this hydraulic filter screen takes on more significances. When we procured the majority of the 0-2A and 0-2B surplus Cessna spare parts in the 1990’s, we got a supply of these screens, p/n HE1649-1. The screen is inside the 2 inch square block on the front firewall LH side just below the hydraulic filler port and above the battery. Removal is fairly easy, remove the 4 bolts holding the square block and the filter screen is inside the block. Hold the screen element up to a light and see if it is clogged. You can try to blow it out or clean with MEK/equivalent. If it cannot be cleaned, call us and we can send you a new replacement filter screen. We also have complete landing gear/hydraulic system parts. (This filter screen p/n HE1649-1 is also the same p/n on Cessna 210 aircraft).

We also recommend that the landing gear hydraulic system be re-filled often. There are numerous places that small leaks can occur and many early Skymaster landing gear problems are caused by low hydraulic fluid levels in the power pack. Even with the sight glass it is difficult to determine the level of the fluid. The only way to be sure is to fill the system until it runs out the overboard drain at the belly.