The Duncan Download Blog: Business Aviation Advice & Observations

Five Consequences of Ignoring Landing Gear Trunnion Corrosion

Posted by Diane Heiserman on Tue, Jan 08, 2013 @ 04:04 PM

Contributed by Dave Schiver, Airframe Tech Rep.

Learjet Trunnion Fixture

A unique Duncan Aviation solution saves the customer more than six months of downtime and a significant amount of money.

Corrosion Ignored never stops!

Due to its location and exposure to the elements, landing gear is highly susceptible to corrosion. And corrosion, even in small amounts, will not stop growing until it is effectively removed. If left unattended, landing gear corrosion can grow and jeopardize the functionality and airworthiness of the unit leading to expensive repairs or the premature removal of components.

As a Learjet (non 40/45) owner/operator, I want to advise you of a corrosive situation that can occur on all Learjet model aircraft, excluding the 40/45. These aircraft are susceptible to corrosion in the sockets for the main landing gear forward trunnion pins on the bottom side of the wing. Corrosion in this area is serious if left unattended, with the potential to cause cracks in the weakened casting and eventual failure resulting in a potential gear collapse.

Five consequences of ignoring Learjet (non 40/45) landing gear trunnion corrosion.

  1. Increased repair costs requiring the sending of the wing to the OEM for repair or even complete wing replacement.
  2. FAA violations for not following the maintenance manual which requires the repair of all corrosion.
  3. If corrosion is ignored for too long, the castings will have to be replaced.
  4. Corrosion can spread into the adjacent spar which translates into a longer downtime and more money to replace the spar, if not scrapping the entire wing.
  5. Catastrophic failure of the Main Landing Gear (MLG) socket resulting in a takeoff, landing or taxi incident leading to injury or loss of life.

Two solutions to trunnion casting corrosion

Replace Trunnion Castings. To replace trunnion castings, the wing will need to be de-mated and shipped to the OEM in Wichita, KS. There it will be placed in the production wing fixture to remove the upper skin and replace the trunnion castings. Depending on the demand for the fixture, we have seen downtimes as long as six months and at a significantly high repair cast.   

Remove Corrosion from Trunnion Casting. Without having to remove the wing, Duncan Aviation is able to remove the corrosion with an on-wing fixture that allows qualified airframe technicians to bore the trunnion and insert a bushing, while staying within allowable limits. This repair process generally takes only 5-7days to complete, eliminating the need for wing removal, shipping, months of down time and at a dramatically less overall cost.

If there is sufficient Ground Support Equipment (GSE) available at your location, this repair can be performed in your hangar by Duncan Aviation’s Engine AOG Rapid Response Teams.

You can read more about this innovative on-wing fixture in the Duncan Debrief. If you have any questions about this or other Learjet technical issues, contact me at anytime. For scheduling and pricing information, contact Learjet Airframe Service Sales Representative Brad Lennemann.

Dave Schiver is an Airframe Technical Representative at Duncan Aviation’s Lincoln, Nebr. (LNK) facility. He specializes in Learjet aircraft. His aviation career began in 1981.

Tags: Learjet, Landing Gear


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