This article initially appeared in PS 786 (May 18), pp. 38-39.
When hydraulic filters don’t do their job, it leads to system contamination, component failure and flight safety concerns.
Hydraulic pumps, primary servos, actuators and tail rotor servos have a high failure rate when using the current legacy filters. Dynamic flow testing showed the filters captured and then released a cloud of particles that flowed downstream from the filter into hydraulic components. This condition, known as silting, causes spool valve locking, uncommanded flight control inputs, and increased component wear.
To combat the problem, a series of new, improved filters were tested. Over many flight hours, the new filters removed particulate matter, improved hydraulic fluid cleanliness, and increased the mean time between failures (MTBF) for six key hydraulic components.
For example, the failure rate of the primary hydraulic servos dropped from 310 failures with a MTBF of 648 hours to just 25 failures with a MTBF of 1,389 hours; a 114.3 percent MTBF rate increase. And hydraulic pump replacement went from 285 failures with a MTBF of 705 hours to just 25 with 1,389 MTBF; a 97 percent increase in the MTBF rate.
New filter reduces failures
Hydraulic systems require very clean fluid to make things work. From helicopters to the aviation ground power units (AGPUs) that service aircraft, hydraulic filters are the key to increased operation, reliability and safety.
AGPUs also use new filters
The new filters, which are completely interchangeable with the old ones, will be added to the next TM updates for the H-60, AH-64 and AGPU. Until then, order the new filters from this list:
| System |
Old Filter NSN |
New Filter NSN |
| H-60 |
1650-01-114-1899 |
1650-01-601-1254 |
| AH-64 |
1650-01-328-5588 |
1650-01-642-2829 |
| AGPU |
4330-01-484-0896
4330-01-484-0891 |
2940-01-605-7088 |