Definition
An edge-type oil filter consisting of a stack of thin metal disks separated by spacers, with cleaner blades that fit between the disks. As oil passes between the disks, contaminants larger than the disk spacing are trapped on the outer edges. The filter is cleaned by rotating a handle that turns the cleaner blades through the disk stack, scraping the trapped material off the edges so it falls into a sediment chamber below.
Plain English
A reusable oil filter built from a stack of metal plates with tiny gaps between them. Dirt gets caught on the outside of the stack, and turning a handle on top scrapes the dirt off so the filter keeps working without being replaced.
Context Anchor
Seen in aircraft maintenance instructions for servicing oil, fuel, or hydraulic system filters.
Derivation
Named after the Cuno Engineering Corporation, which developed and marketed this style of edge filter in the early 20th century. The name became a generic term for this disk-and-blade filter design, much like how 'Hoover' became a name for vacuum cleaners.
Why Pilots Care
Keeps engine oil free of abrasive particles, reducing wear on bearings and other moving parts and helping prevent in-flight engine problems.
Analogy
Think of a reusable kitchen strainer with a built-in scraper: the fluid passes through, dirt is caught, and the trapped material can be scraped away so the strainer can keep working.
Intuition Check
Do not read Cuno as the name of a fluid or aircraft system. It refers to a particular cleanable filter design.
Example Sentence 1
During the 50-hour inspection, the mechanic rotated the Cuno filter handle several times to scrape contaminants off the disk stack before draining the sediment chamber.
Example Sentence 2
The oil analysis report improved after the old Cuno filter was replaced with a clean element.