The Diamond DA40, with its robust composite construction and fixed landing gear, offers a straightforward yet highly effective design. While its landing gear is known for its durability, specific wear components like bushings in the nose and main gear assemblies require periodic inspection and replacement. For DA40 owners operating across California, Arizona, and Nevada, understanding when and how to address these bushings is crucial for maintaining precise ground handling, preventing shimmy, and ensuring overall airworthiness.
At The Aero Center, we possess deep expertise in the Diamond DA40’s unique landing gear design. Our 24/7 maintenance service is dedicated to efficiently addressing these critical wear items, significantly reducing your aircraft’s downtime. As Cialdini’s principle of Authority suggests, relying on mechanics thoroughly familiar with Diamond’s specific maintenance procedures ensures the longevity and safe operation of your aircraft’s landing gear.
WHEN TO REPLACE LANDING GEAR BUSHINGS
Unlike components with explicit Time Between Overhaul (TBO) limits, landing gear bushings are typically replaced “on condition.” This means they are replaced when inspections reveal signs of wear, excessive play, or damage. However, Diamond Aircraft does issue Service Bulletins (SBs) that may mandate or recommend inspection and replacement at specific intervals or in response to certain symptoms.
- Scheduled Inspections (100-hour / Annual):
- Primary Opportunity: These inspections are the most critical times for a mechanic to thoroughly examine all landing gear bushings.
- What to Look For:
- Excessive Play/Slop: The most common symptom of worn bushings is noticeable play or “slop” in the movement of the nose wheel fork or main gear side stays. While some minor play is normal, excessive movement beyond manufacturer tolerances indicates bushing wear.
- Visual Wear: Bushings are designed to wear sacrificially. Look for visible signs of wear, deformation, or corrosion on the bushings themselves. This might require disassembly of certain components.
- Chafing Marks: Especially on the nose gear, chafing marks on the outer edge of collar bushings (e.g., P/N D44-3223-10-00X01) can indicate wear or migration, as noted in Diamond Service Bulletins like WI-MSB 40NG-020.
- Uneven Tire Wear: While many factors contribute, uneven or rapid tire wear can sometimes be a secondary indicator of excessive play in the landing gear due to worn bushings.
- Symptoms of Wear (Between Inspections):
- Nose Wheel Shimmy: This is a classic and significant symptom of worn nose landing gear bushings, particularly those in the nose wheel fork pivot. While shimmy can also be caused by improper tire pressure, a faulty shimmy damper, or alignment issues, worn bushings are a prime suspect. If you experience shimmy, have it inspected immediately.
- Difficulty Steering on the Ground: Excessive play in the nose gear bushings can make it harder to maintain directional control during taxiing.
- Unusual Noises: Clunking or rattling sounds during taxi or landing can indicate loose components due to worn bushings.
- Service Bulletins/ADs: Always comply with any applicable Diamond Service Bulletins or FAA Airworthiness Directives (ADs) that address landing gear bushing inspections or replacements. For example, some SBs address inspection of the nose landing gear (NLG) pivot for cracks and replacement of collar bushings at specific intervals or conditions (e.g., within 50 landings, then every 100 landings thereafter for certain part numbers, as per WI-MSB 40NG-020).
HOW TO REPLACE LANDING GEAR BUSHINGS
Replacing landing gear bushings is a task for a certified A&P (Airframe and Powerplant) mechanic, preferably one with specific experience on Diamond aircraft. It often requires specialized tools, precise measurements, and adherence to the Diamond DA40 Airplane Maintenance Manual (AMM). The process varies slightly between nose gear and main gear bushings.
General Steps (Illustrative, specific AMM procedures must be followed):
- Aircraft Support:
- The aircraft must be properly jacked to remove weight from the landing gear in question. This is a critical safety step, as the aircraft must be stable.
- Disassembly and Access:
- Nose Gear: This often involves removing the nose wheel assembly, the wheel pant (if installed), and disconnecting the steering links and shimmy damper. Accessing the pivot bushings at the top of the nose gear leg requires careful disassembly. Diamond SBs might also require checking for cracks on the NLG pivot during this process.
- Main Gear: Accessing main gear bushings typically involves removing the wheel and brake assembly, and possibly parts of the wheel pant. Some bushings are in the main gear leg attachment points to the fuselage, which can be more complex. For instance, some service bulletins (e.g., SB190LIN-57-0016 for similar aircraft designs) describe removing the main landing gear side stay support fitting to access bushings.
- Bushing Removal:
- Bushings are usually press-fit or interference-fit into their housings.
- Methods: Specialized bushing removal tools (presses or drivers) are often used. Some mechanics might use a tap to thread the inside of the bushing, then screw in a bolt to pull or press it out. Applying heat to the outer housing or cooling the bushing with dry ice can sometimes aid removal by causing differential expansion/contraction.
- Caution: Care must be taken not to damage the housing bore during removal.
- Inspection of Housing/Mating Surfaces:
- Once the old bushings are out, the mechanic will thoroughly inspect the bore of the housing for any corrosion, pitting, wear, or distortion. Any damage here could affect the fit of the new bushing and lead to premature wear.
- Ensure any shims or washers are inspected for deformation and replaced if necessary. The Diamond WI-MSB 40NG-020, for example, calls for inspecting washer D41-3223-00-34 for deformation to ensure it’s “absolutely planar.”
- New Bushing Installation:
- New bushings are typically press-fit into the clean, inspected bores.
- Methods: Specialized installation tools are used to press the new bushing squarely into place. Some bushings may require reaming to achieve the exact internal diameter after installation to ensure a precise fit with the pin or shaft.
- Lubrication: Apply specified lubricants (e.g., aviation grease) to the bushings and mating surfaces during assembly. WI-MSB 40NG-020 specifically mentions lubricating O-rings on the nose wheel fork with Lubricant Type 1.
- Shims: Install appropriate shims to achieve correct “end float” or play, as per the AMM.
- Reassembly and Rigging:
- Reassemble the landing gear components, ensuring all bolts are tightened to the correct torque values using a calibrated torque wrench. Use new self-locking nuts and cotter pins where required.
- Nose Gear Steering Friction: For the nose gear, re-check and adjust the steering friction as per the AMM to ensure proper control and prevent shimmy.
- Landing Gear Alignment: A post-replacement alignment check is often performed to ensure correct geometry.
- Functional Checks:
- Perform full range of motion checks for steering and shock strut compression.
- Conduct ground runs and taxi tests to verify proper ground handling and absence of shimmy.
Replacing landing gear bushings on a Diamond DA40 is a meticulous task that requires adherence to manufacturer specifications and best maintenance practices. Proactive inspection during annuals and prompt attention to any signs of wear, particularly nose wheel shimmy, will ensure your DA40 remains safe and enjoyable to fly across California, Arizona, and Nevada.
The Aero Center is equipped with the expertise and tooling necessary to perform all aspects of Diamond DA40 landing gear maintenance, including precise bushing replacement. Our 24/7 availability ensures that your aircraft receives expert care when it’s most needed, minimizing your downtime.
The Aero Center is located at William J. Fox Airfield KWJF | Lancaster, CA. Contact us at 209.885.6950 for questions or appointments.
Footnotes:
- Diamond Aircraft Industries GmbH. WI-MSB 40NG-020 – Inspection of NLG pivot of NLG-legs installed under OÄM 40-334.
- Diamond Aircraft Industries. DA40 Series Airplane Maintenance Manual.
- Diamond Aviators Forum. “Nose wheel strut issue.” https://www.diamondaviators.net/forum/viewtopic.php?t=5434
- McFarlane Aviation. “Cessna Torque Link Repair – FAQ.” https://www.mcfarlaneaviation.com/products/categories/all-products/landing-gear-components/torque-link-repair/cessna-torque-link-repair/faq/ (While for Cessna, this resource provides good general insight into bushing removal and shimmy issues.)