Bad Yokes

During a scheduled inspection, technicians encountered corroded and bent control yoke boss attachment hardware that proved difficult to remove. After consulting with the manufacturer, the final recommendation was to remove the boss via cutting the bolts (p/n 2315152-33). Manufacturer was able to repair the yoke assembly using SB 31-27-11 and kit 2381602-801. Aircraft had been parked outside without gust locks.

Editorial Staff

Monday, August 20, 2018 at 12:00 AM ET

Verified

Key Takeaways:

Numerous incidents involve the failure or corrosion of various yoke assemblies, including control yokes, nose landing gear (NLG), main landing gear (MLG), and ski yokes, across diverse aircraft types.
Corrosion is a predominant contributing factor to these failures, often originating internally or at critical attachment points and sometimes exacerbated by external conditions or lack of maintenance.
These failures can occur during various operational phases, from preflight checks and taxiing to hard landings, often leading to immediate operational issues, damage, or even accidents.
The incidents underscore the critical need for thorough inspections, proactive corrosion management, and timely compliance with manufacturer's service bulletins to ensure structural integrity.

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Beech Model B24R Sierra

Failed NLG Yoke Assembly

The nose gear yoke assembly departed the aircraft after a hard landing. Inspection revealed existing corrosion in the strut with signs of an existing crack. The corrosion and crack occurred where the strut attaches to the yoke.

Part total time: 4004.0 hours

Cessna 172P Skyhawk

Corroded Control Yoke

During preflight inspection, pilot’s yoke failed as proper control movement was verified. Corrosion discovered from the inside out below the pivot point.

Part total time: Unknown

Cessna A185F Skywagon

Failed Ski Yoke

While taxiing the ski-equipped airplane on a snow-covered lake, the pilot initiated a left turn. The right ski went into some overflow and the outboard welds on the ski yoke broke. As a result, the tire/wheel went into the snow and the aircraft went onto its back.

Part total time: Unknown

Cessna A185F Skywagon

Corroded Control Yoke

Hole noted in steel tube on left side of control yoke (p/n 0711850-1) two inches from welded joint to vertical tube. Similar hole found on opposite side when probed with sharp pick. Manufacturer’s SB 01-3 found not accomplished.

Part total time: 4455.0 hours

Learjet Model 31A

Corroded Control Yoke Hardware

Part total time: 3336.0 hours

Pilatus PC-12/45

MLG Yoke Assembly Failure

During taxi, the left main landing gear yoke assembly fractured at the lug fittings for the trailing link axle attachment. The trailing link partially separated and the aircraft came to rest on the remaining assembly. A replacement gear assembly was installed. Damage included the left MLG assembly, left gear door and hinge, and some small localized lower wing dents.

Part total time: 21,759.0 hours

Pilatus PC-12/47

Binding NLG Steering Yoke

During a scheduled inspection, the technician noticed an unusual noise from the nose landing gear area. Investigation revealed binding in nose landing gear steering yoke assembly. Removed and replaced retaining washer, bolt, rod end assembly, D-ring, ring and clevis pin.

Part total time: 267.0 hours