13/02/2020
Many Mooney pilots overlook their down-lock tensions or over-centre preload on their aircraft because they simply don’t know about it or don’t understand it. The inspection process requires special tools, only finding use on the M20 airframe so maintainers who don’t service many Mooneys usually don’t have the correct tooling and often don’t check the down-lock tensions correctly. Down-lock tension readings can be “masked” by poorly lubricated linkages and springs. These issues would need to be addressed prior to measuring the tensions or preload in the system in order to get an accurate reading.
Omitting to ensure the undercarriage is in top working condition could seriously ruin your day.
The purpose of introducing preload into the undercarriage system is to provide resistance to the locks that hold the undercarriage down. These locks are pushed “over centre” by the actuation rods against the stop mechanism created by the combination of the retraction link and the retraction truss. The actuation rods are powered by a strong arm in the early Mooneys or an electric motor in the newer versions. Simply put, the amount of force required to push these locks back over their centre point in order to retract the undercarriage is the “down-lock” tension.
When the tension in the system is insufficient, the gear will still lock in the down position, but, with enough external force, from a molehill on a grass strip, for example, the sudden “jolt” or “joggle” in the system could cause the entire undercarriage to fold up under the aircraft on landing or take-off.
A gear collapse opens a whole can of worms, aside from having to recover your aircraft from an active runway – dealing with insurance, removing the engine for shock-loading or sudden stoppage inspections, a new propeller, bodywork, paint, etc. etc. etc…
The inspection takes a grand total of one hour, including jacking the machine up. That’s money and time well-spent!
Book your aircraft in for a health check at Africa's only Mooney International certified repair and maintenance facility.
We are able to inspect and release most singles to service.
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