The Diamond DA40, with its advanced composite airframe, represents a modern approach to general aviation design. Unlike traditional aluminum aircraft, composites demand a specialized approach to annual inspections. While the fundamental goals of airworthiness remain the same, the inspection techniques, common failure modes, and repair methodologies differ significantly. For DA40 owners in California, Arizona, and Nevada, a comprehensive annual inspection by mechanics experienced in composite structures is paramount for ensuring safety, compliance, and the long-term integrity of their aircraft.
At The Aero Center, our A&P mechanics with Inspection Authorization (IA) are highly trained in the unique requirements of composite aircraft like the DA40. Our 24/7 maintenance center is equipped with the specialized tools and knowledge necessary to conduct thorough annual inspections, minimizing your aircraft’s downtime. We emphasize Authority in our meticulous adherence to Diamond Aircraft’s stringent maintenance schedules and all applicable Airworthiness Directives, providing unparalleled confidence to our clients.
GENERAL REQUIREMENTS FOR A COMPOSITE ANNUAL INSPECTION
Similar to any annual inspection, the DA40 must be thoroughly cleaned, and all necessary inspection plates, access doors, fairings, and cowlings removed or opened to provide full access. The inspection of a composite aircraft emphasizes:
- Visual Inspection (VT): Meticulous examination of surfaces for cosmetic and structural flaws.
- Tap Testing: A crucial technique for detecting subsurface delaminations and disbonds.
- Specific NDT where required: Utilizing advanced methods like ultrasonic testing for suspect areas.
- Adherence to Diamond’s Maintenance Manual and SRM: These documents are the definitive source for inspection criteria, repair limits, and procedures.
DIAMOND DA40 ANNUAL INSPECTION CHECKLIST (COMPOSITE EMPHASIS)
This checklist provides a general overview, but the Diamond DA40 Airplane Maintenance Manual (AMM) and Structural Repair Manual (SRM) are the ultimate authority for detailed procedures and limits.
I. OPERATIONAL CHECKS (Pre-Inspection Run-Up & Cockpit Checks)
- Documentation: Verify current airworthiness certificate, registration, operating limitations, weight and balance. Review aircraft logbooks, Airworthiness Directive (AD) compliance (especially composite-related ADs), and current status of all mandatory inspections.
- Engine Run-Up: (Specific to Lycoming IO-360 or Austro AE300)
- Check engine oil pressure and temperature within limits.
- Perform magneto check / FADEC system check.
- Verify throttle and mixture (or power lever on AE300) control operation (smooth, full travel).
- Propeller operation (constant speed).
- Static RPM check within limits.
- Verify alternator/generator output and battery charging.
- Check all engine instruments, fuel flow.
- Listen for any unusual engine noises.
- Cockpit/Cabin:
- Inspect seats, seat belts, and harnesses for condition, security, and proper operation.
- Check acrylic canopy/windows for crazing, delamination, cracks, clarity. Inspect attachment points.
- Verify operation and security of all flight and engine controls (full, free, correct travel, no binding or excessive play).
- Inspect instruments for condition, mounting, markings, and proper operation (including glass cockpit functionality).
- Check all lights (interior, exterior, nav, strobe, landing, taxi) for operation.
- Verify stall warning system operation (if applicable).
- Check pitot-static system drains and function.
- Inspect battery and battery box for proper installation, security, and charge.
- Verify ELT operation and battery expiration date.
- Check cabin heater, defroster, and ventilation systems.
- Inspect baggage compartment and door for security, latch operation, and condition.
II. FUSELAGE (Composite Structure Emphasis)
- Overall Fuselage Skin: Conduct a meticulous visual inspection for:
- Cracks: Especially hairline cracks in the paint/gel coat. While some might be cosmetic, investigate thoroughly with a magnifying glass. Pay attention to areas around cutouts, access panels, and high-stress points.
- Delamination: Look for bubbles, blisters, or areas where the surface appears to have separated from the underlying structure.
- Impact Damage (BVID): Subtle dents, scuffs, or changes in surface sheen that may indicate significant subsurface damage. Perform tap testing in suspect areas – a dull thud indicates delamination.
- Discoloration: Yellowing, fading, or chalking of the paint, indicating UV degradation.
- Loose Rivets/Fasteners: Though composites use bonding extensively, inspect any mechanical fasteners for security and corrosion.
- Firewall: Inspect composite firewall for cracks, delamination, and heat damage.
- Control Linkages: Inspect all pushrods, bellcranks, and bearings within the fuselage for excessive wear, play, corrosion, and proper lubrication.
- Landing Gear Attachments: Crucial inspection points. Carefully inspect the composite structure around the main landing gear and nose gear attachment points for cracks, delamination, and evidence of stress. Perform tap testing in these areas.
- Door & Latch Mechanisms: Inspect door hinges, latches, and seals for proper operation, security, and wear. Inspect the surrounding composite structure for cracks due to stress.
- Antennas: Inspect all antennas for security, corrosion, and proper wiring.
III. WINGS (Composite Structure Emphasis)
- Wing Skin: Conduct meticulous visual inspection and tap testing of the entire wing surface, top and bottom.
- Pay critical attention to the wing root area where the wing attaches to the fuselage, a high-stress point prone to cracking and delamination.
- Inspect for any signs of water ingress, especially in the leading edge or tank areas, which can degrade composites.
- Fuel Tanks (Wet Wing): Inspect for any signs of fuel leaks from the composite structure. Look for fuel staining around rivets and seams. (Refer to previous blog on Mooney fuel bladder leaks for general principles of wet wing inspection)¹.
- Wing Attachment Points: Inspect the bolts and fittings where the wing spars attach to the fuselage. These are critical load-bearing points.
- Ailerons & Flaps (Composite Construction):
- Inspect surfaces for cracks, delamination, and impact damage.
- Inspect hinges and attachment points for excessive play, wear, and corrosion.
- Lubricate flap tracks and hinges as per manual.
- Check flap and aileron control stops for proper adjustment.
IV. EMPENNAGE (Composite Structure Emphasis)
- Overall Empennage Skin: Conduct meticulous visual inspection and tap testing of the vertical and horizontal stabilizers (fin and stabilator) for cracks, delamination, and impact damage.
- Control Surfaces: Inspect rudder and stabilator surfaces for cracks, delamination, and impact damage.
- Hinges & Attachments: Inspect hinges, control horns, and attachments for wear, play, and security. Lubricate as per manual.
- Control Stops: Verify rudder and stabilator control stops are properly adjusted.
- Stabilator Jackscrew/Actuator: Inspect for proper lubrication, wear, and security (if applicable to model).
V. ENGINE COMPARTMENT (Specific to Lycoming IO-360 or Austro AE300)
- Engine Mount: Inspect engine mount frame (often steel tube) for cracks, corrosion, and distortion. Inspect rubber vibration isolators for deterioration.
- Cowl and Fasteners (Composite): Inspect composite engine cowlings for cracks, delamination, and heat damage. Check all cowl fasteners for security and proper operation.
- Fuel System: Inspect all fuel lines, hoses, and fittings for leaks, security, chafing, and deterioration. Inspect fuel pumps, fuel strainers, and fuel vents.
- Exhaust System: Inspect exhaust stacks, muffler, and heat exchanger for cracks, leaks, and security. Critical for CO poisoning prevention.
- Intake System: Inspect intake manifold and hoses for security, leaks, and deterioration.
- Propeller System: (Refer to previous blog on Spinner Backplates) Inspect blades, hub, spinner, and spinner backplate for cracks, nicks, corrosion, and security. For constant speed props, inspect governor and control rigging.
- Cooling System (AE300): Inspect radiator, coolant lines, and fans for leaks, damage, and security.
VI. LANDING GEAR
- Gear Legs (Composite): Inspect composite main gear legs for cracks, delamination, impact damage, and proper attachment. Perform tap testing along the legs.
- Wheels: Inspect wheels for cracks, defects, and bearing condition.
- Tires: Inspect tires for wear, cuts, and proper inflation.
- Brakes: Inspect brake pads for wear, rotors for condition, and hydraulic lines for leaks. Check brake adjustment.
- Nose Gear: Inspect nose gear strut, shimmy damper, steering linkages, and tire for condition and operation.
VII. AIRWORTHINESS DIRECTIVES (ADS) & SERVICE BULLETINS (SBS)
- Mandatory Compliance: The IA mechanic must ensure compliance with all applicable Airworthiness Directives (ADs) for the specific DA40 model and serial number. Current ADs for the DA40 might include those related to:
- Wing spar attachment points or bonding.
- Fuel system components.
- Propeller or engine specific ADs.
- Electrical system components.
- Service Bulletins: Review relevant Service Bulletins (SBs) issued by Diamond Aircraft. While generally not mandatory for Part 91 operations, SBs often address known issues and provide valuable proactive maintenance guidance that can prevent future problems. Owners should discuss recommended SBs with their mechanic.
VIII. POST-INSPECTION ACTIONS
- Rectify Discrepancies: All discovered discrepancies must be rectified to restore the aircraft to an airworthy condition. Repairs to composite structures must be performed strictly according to the Diamond SRM or FAA-approved data (e.g., Form 337).
- Lubrication & Servicing: Perform all required lubrication and servicing as per the DA40 Maintenance Manual.
- Reassembly & Rigging: Reassemble all removed components. Verify proper rigging of all flight controls (ailerons, flaps, rudder, stabilator) and engine controls.
- Final Functional Check: Perform a final engine run-up and functional checks of all systems.
- Documentation: Make detailed entries in the aircraft’s logbooks for the annual inspection, all discrepancies found, and all corrective actions taken, including part numbers and references to approved data (e.g., ADs, SBs, Form 337s). The IA will sign off the annual inspection.
For Diamond DA40 owners in California, Arizona, and Nevada, the annual inspection is your primary assurance of safety and continued performance. Entrusting this vital task to The Aero Center’s experienced IA mechanics ensures your composite aircraft receives the specialized attention it demands. Our 24/7 service means your DA40 will be back in the air, certified airworthy, with minimal delay.
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. DA40 Series Airplane Maintenance Manual. (Specific Part Number and latest revision is critical).
- Diamond Aircraft Industries GmbH. DA40 Series Structural Repair Manual.
- Federal Aviation Administration (FAA). 14 CFR Part 43, Appendix D – Scope and Detail of Items to be Included in Annual and 100-Hour Inspections.
- Aircraft Owners and Pilots Association (AOPA). “Composite Aircraft Maintenance.” https://www.aopa.org/news-and-media/all-news/2018/june/composite-aircraft-maintenance