The careless $80,000 slide is one thing, but landing gear mishaps from mechanical failure on Cessna model 210/210B singles might be avoided with a recent NTSB Safety Recommendation that landing gear actuators are inspected for fatigue cracking. Inevitably, the Safety Recommendation A-25-36 will become an airworthiness directive in response to Textron Aviation’s service bulletin on the matter.
on the interior of the actuator housing and propagated outward into the housing. When the cracks grew large enough, the housing fractured, which resulted in a loss of hydraulic fluid.
It’s the Cessna part number 128051 1/-2 (or Electrol part number EA1614-1/-2) hydraulic gear actuators that are the focus of the inspection, and a recommendation to develop a life-limit for replacement for these components ahead of them cracking and an inadvertent gear retraction upon landing. In its letter, the NTSB said that since 2015 it has investigated five accidents where Cessna 210 main landing gear failed to fully extend. Either the pilot executes an emergency gear extension or simply lands with the gear partially retracted. Regardless, the probable cause for all was fatigue failure of the actuator. Why do they fail? You guessed it—corrosion.
According to the NTSB, the actuator construction is from aluminum alloy tempered to maximum strength and hardness, but it’s susceptible to specific corrosion mechanisms, like pitting. The NTSB’s examination of the failed actuators found that the geometry of the housing where the retainer ring is located may impart a high stress concentration at the area of fatigue crack initiation.
On The Shop Floor
If you’re buying any Cessna 210, obviously you want to pay close attention to the landing gear—as you would any used retrac. The NTSB points out that since these cracks are entirely inside the actuator, they would be difficult to find with many standard techniques, like fluorescent penetration or visual examination. However, with correctly calibrated inspection equipment and procedures, ultrasonic inspection or eddy current inspection should be able to detect such cracks before they propagate through the barrel of the actuator. Currently, no life limit has been defined or established for the actuator.
The landing gear on Centurions has always been a focus of extended maintenance. Cessna has issued three service letters concerning these hydraulic actuators since 1967, but none of them addressed the failure mode covered in the NTSB’s recent reporting. These previous service letters required periodic inspections for cracking of the housing and replacement of the spindle assembly and associated bearings, but none focused on the retainer ring. In 1976, the FAA issued Airworthiness Directive (AD) 76-04-01 requiring compliance with the most recent Cessna service letter (SE 75-21).
This inspection is suggested o 210/210B models, very early models and a minority of the fleet. For completeness and clarity it would be prudent to have mentioned these facts in your article.
Respectfully,
Robin Ardoin
Edited for clarification, thanks. We did link to the NTSB Safety Recommendation. Still, we’ve worked on enough Centurions and seen enough landing gear failures to suggest they all deserve careful inspection.