Experimental & Amateur-Built Aircraft Annual Condition Inspection

ContextWork systematically from nose to tail with a strong light held at a low, raking angle to the surface — shadows from this angle reveal shallow dents and waviness that are invisible in direct overhead light. On aluminum aircraft, look for corrosion 'pillowing' under paint: a subtle bubbling that indicates active pitting beneath the surface. Any crack emanating from a rivet or fastener hole in primary structure is serious and requires evaluation before return to service; cracks propagate from stress concentrations and do not self-arrest. On fiberglass or carbon composite fuselages, tap each panel with a coin or knuckle and listen — a hollow, dull sound compared to adjacent panels indicates delamination between skin layers. Photograph all findings before any corrective work.

ContextA rivet showing a ring of fretting — a thin shadow of paint wear completely encircling the rivet head — has been moving in its hole, meaning the joint has lost clamping integrity. This is common at heavily loaded attachment points and warrants further disassembly to assess the underlying hole condition. On tube-and-fabric or tube-and-sheet metal structures, apply a dye penetrant kit ($20–$40 at aviation tool suppliers) at all cluster welds and gusset plates to reveal hairline cracks that are invisible to the unaided eye. The fatigue failure in welded structure rarely originates at the weld itself but in the heat-affected zone just beyond it — probe these areas preferentially.

ContextThe firewall's sole function is to prevent an engine compartment fire from reaching the cockpit for a minimum of 15 minutes — any crack, even small, compromises that capability and must be repaired before the aircraft returns to service. Inspect every firewall penetration — fuel lines, control cables, electrical conduits — for intact fireproof grommets and sealant. Deteriorated red or gray fireproof sealant (typically silicone or a ceramic-based compound) should be cleaned out and replaced; cracked or dried sealant no longer provides either fire resistance or fume barrier protection. On steel firewalls, look for rust staining beneath paint near the bottom of the firewall where oil mist and condensation collect.

ContextPay close attention to any area that has been repainted or appears unusually clean compared to its surroundings — this sometimes indicates a prior owner remediated corrosion without fully documenting it. On wood structure aircraft (spruce spars, plywood skins), probe suspect areas with a sharp pin tool; structurally sound spruce resists penetration with firm hand pressure, while rot allows the pin to sink with minimal force. In areas prone to moisture accumulation — the aft lower fuselage, the nose bowl just ahead of the firewall, the area around the tailwheel spring attachment — clear any trapped debris and inspect the underlying structure directly. Longerons, the primary fore-aft load-carrying members, should follow the clean designed curvature of the fuselage with no abrupt bends or kinks.

ContextMissing or incorrect fasteners on fairings and access panels create a genuine in-flight risk — panels that depart the aircraft can strike the tail surfaces. Verify that all Dzus fasteners, camloc receptacles, and screws are the correct size and length for their installation: a fastener that bottoms out before the panel is drawn tight will not hold, and one that is excessively long will strip or deform the structure. On composite aircraft, check fiberglass fairing flanges for delamination at the attachment holes, which is extremely common after repeated removal for inspections over several years.

ContextWing attach hardware is life-critical and deserves more time than any other single inspection item. After verifying current torque, apply torque-seal or a paint witness mark across each bolt head to the fitting face — this makes any subsequent rotation visible at a glance during preflight. On trailerable aircraft with removable wings, pull each attach pin or bolt, clean the bores, and inspect with a bright light for hole elongation or cracking. Corrosion inside a wing root spar box or main spar pocket is not visible from outside the aircraft — use a borescope if available, or a flashlight and inspection mirror to examine as far inboard as possible. Any corrosion in a spar or main fitting must be evaluated for structural adequacy before reassembly.

ContextOil-canning — a subtle buckling of the skin visible as light changes across the upper surface — in primary wing panels can indicate that the skin has been plastically deformed under an overstress event, or that the internal structure it is attached to has shifted or failed. Leading-edge dents from bird strikes or runway debris may look purely cosmetic but can change the effective airfoil profile enough to noticeably alter stall characteristics, particularly on laminar-flow designs such as the Van's RV series where the first 20–30% of chord is critical to performance. On composite wings, run a fingernail along any seam line — a raised or stepped edge indicates the bond line has partially separated and requires investigation.

ContextApplicable to strut-braced high-wing designs. Inspect each strut along its entire length for any bend, which indicates a load event beyond normal flight — a bent strut means the aircraft experienced an overload the pilot may or may not have reported. At each end fitting, inspect for cracks at the weld, machined shoulder, or crimped swage, and verify that all clevis pins have correct cotter pins or safety wire intact. On fabric-wing aircraft, jury struts often show corrosion from moisture trapped between the fitting and the fabric; remove any wrap or tape at the ends and inspect the metal underneath directly.

ContextFlap track rollers wear over time and allow lateral slop, which can cause flap asymmetry during extension — a serious aerodynamic hazard. Grasp each flap at the trailing edge and rock it vertically and laterally; any play greater than a few millimeters warrants disassembly and measurement of the roller-to-track clearance. On electric flap installations, cycle the flaps through their full range slowly and listen for hesitation, unusual motor noise, or any stepwise motion, then verify the limit switches stop the motor promptly at both ends of travel. Flap actuator rod ends should show no perceptible play at the attach bolt; a worn rod end that has spun in its shank is not repairable and must be replaced.

ContextA measurable change in wing incidence or dihedral compared to the aircraft's original build documentation or a prior recorded measurement is a serious finding — it indicates either a structural event (hard landing, torsional overload, ground collision) or progressive structural failure. Use a digital inclinometer or level on the spar cap or a builder-designated reference surface per the aircraft plans. On strut-braced aircraft, a strut bent in service and then straightened will often leave a subtle change in the wing's geometric relationship to the fuselage. This measurement requires fewer than 20 minutes and can reveal structural damage that a visual inspection alone cannot detect.

ContextUse a calibrated deflection gauge or protractor to measure actual degrees of travel for elevator up and down, aileron up and down, and rudder left and right. These limits were established during Phase I flight testing as the boundaries within which the aircraft's handling qualities are known to be acceptable. Exceeding published up-travel limits on any control surface creates the potential for aerodynamic flutter — an oscillation that can destroy a control surface in seconds at cruise speed. Under-travel reduces control authority in critical phases of flight. Record the measured values and compare them against prior inspection records; rigging should be essentially stable year over year unless a cable has stretched or a turnbuckle has backed off.

Context7x19 aircraft cable is unserviceable if any single wire in any strand is broken — not broken through, just fractured — and the standard inspection method is to wrap a cloth rag (never bare skin, which a broken wire will slice) around the cable and slowly run it along the entire length, feeling for a catch or snag. The highest-wear areas are inside conduits and at pulley contact points; budget extra time here. A stainless steel cable that shows reddish-brown discoloration at any point paradoxically has internal corrosion between strands, not surface corrosion — the iron oxide is wicking up from the core. Galvanized cable showing white or gray corrosion product is also unserviceable. Neither condition is acceptable in primary flight controls.

ContextCable tension changes approximately 10 lbs per 10°F change in ambient temperature because steel cables and the aluminum airframe expand and contract at different rates. If the ambient temperature during inspection differs significantly from the temperature at which the cables were originally set, apply the temperature-correction chart from the cable manufacturer or use the formula to correct your readings. Cable tension that is too low creates slop and allows control surface vibration. Cable tension that is too high overstresses pulleys, fairleads, and attach fittings, and can cause the cable to jump a pulley under an asymmetric load. Always record measured values — a tension that is 'in spec today' but lower than the same measurement from two inspections ago tells you the cable has stretched.

ContextRod end thread engagement (the amount of thread screwed into the pushrod tube) must equal at least one full diameter of the thread — for a 1/4-28 AN rod end, that means at least 0.25 inches of engagement. During initial build, most builders apply a paint stripe across the rod end and tube as a witness mark; if that mark is broken or displaced, the rod end has turned in service. Pushrods that are kinked or bent must be replaced — a kinked pushrod will fail at the kink under a flight load that would be well within the original design margin. Torque tubes and bellcranks should be inspected at all weld points with dye penetrant, focusing on the area just beyond the weld heat-affected zone.

ContextGrasp each pulley rim between two fingers and wiggle it while holding the axle stationary — any detectable motion indicates a worn bearing that will allow the cable to track sideways on the pulley face, eventually causing it to jump the pulley guard or abrade against the bracket. Inspect fairleads (the nylon or aluminum guides that redirect cables through structural members) for any groove worn into them by the cable; a groove means the cable has been sawing against the fairlead and both the fairlead and the cable at that point should be considered suspect. Verify that no cable approaches a fairlead at more than approximately 3 degrees off perpendicular — greater angles create a local stress concentration and accelerate wear.

ContextManual trim systems (bungee, trim spring, or screw-and-cable mechanisms) should move smoothly with consistent resistance and no stiction or sudden releases. Electric trim should respond immediately to switch input in both directions and stop firmly at the limit switches — any hesitation or tendency to coast past the stop warrants inspection of the limit switch and motor brush condition. The cockpit trim position indicator must correspond accurately to the actual trim surface position; a discrepancy means the pilot cannot reliably set trim for takeoff or approach, which is a cause of fatal departure accidents. If a servo tab is used, inspect the tab attachment to the main surface and the control horn for cracking at the rivet holes.

ContextThe horizontal stabilizer attach structure carries the full pitch authority of the aircraft — undersized or incorrectly installed fasteners here have caused in-flight structural failures. Inspect every bolt, locking device, and bracket, verifying correct hardware identification markings and that locking devices (cotter pins, nyloc nuts, or safety wire) are intact and not reused past their service limit. On stabilator designs, the single pivot bearing is the critical wear point: grasp the stabilator leading edge firmly and attempt to rock it both vertically and laterally — any perceptible play indicates bearing wear that directly increases flutter susceptibility. The anti-servo tab linkage on stabilators must also be inspected for correct geometry and hinge condition.

ContextHinge wear that allows a control surface to develop even small amounts of free play is a precursor to flutter — the dynamic phenomenon where aerodynamic forces sustain oscillation that grows destructively. Rock each hinge pin in its bracket by hand: acceptable play in a primary flight control hinge is effectively zero. On piano hinge installations (used on many kitbuilt designs for elevator and rudder), examine every hinge knuckle along the entire length because a single failed knuckle puts concentrated bending stress on its neighbors and propagates failure progressively. Any hinge showing visible elongation of the pin hole is unserviceable and must be replaced before flight.

ContextThe vertical stabilizer carries significant side loads during crosswind landing operations and any aggressive rudder input, including full-deflection input common in aerobatic or spin training. On most homebuilt designs the fin is bolted to the aft fuselage top structure — inspect the upper longerons, aft deck, and any reinforcing doublers for deformation, paint cracking, or fastener rotation that indicates the joint has been in motion. Where the fin is integral to the fuselage structure (bonded or welded designs), examine the transition from fin root to fuselage skin on both sides for cracking or disbonding at the joint.

ContextSight down the length of each control surface from the trailing edge with one eye — even a slight twist is readily apparent using this technique. A warped elevator produces a steady nose-up or nose-down tendency requiring constant trim compensation in cruise; more importantly, a surface that has been permanently deformed has been stressed beyond its design limits, and the cause — overspeed event, turbulence encounter, abusive control input — should be identified and recorded in the logbook. A fabric-covered surface can sometimes be re-ironed at low heat to remove thermally induced warps, but a warp in a metal or composite surface indicates plastic deformation of the structure.

ContextApply 80 psi shop pressure to the cylinder through the spark plug hole with the piston at top dead center on the compression stroke. A generally accepted serviceability threshold is 60/80 (75% retention), though most maintenance-minded EAB operators flag anything below 70/80 for a borescope follow-up and ground the aircraft if any cylinder reads below 65/80 until the cause is understood. More important than any single reading is the trend — a cylinder that was 76/80 last year and reads 69/80 today is declining even though 69/80 is technically 'in spec.' Always note where the air escapes: escaping through the crankcase breather tube indicates ring wear; from the exhaust stack indicates an exhaust valve problem; from the carburetor air inlet indicates an intake valve issue. Log every cylinder's result with the ambient temperature.

ContextA USB borescope ($40–$200) inserted through the spark plug hole while the piston is positioned at mid-stroke reveals the cylinder bore surface, piston crown condition, and a partial view of both valve faces. Vertical scoring in the bore indicates a lubrication failure event — caused by oil starvation, overheat, or water ingestion — that warrants cylinder replacement or removal for professional evaluation. A valve face that appears slightly recessed compared to the surrounding seat, or that shows a distinct burn mark on one quadrant, indicates valve recession or burning that will worsen and eventually cause a hot exhaust gas leak past the valve. Carbon deposit patterns on each piston crown also reveal relative mixture distribution — a piston that is notably cleaner than others indicates that cylinder is running lean.

ContextSpectrographic oil analysis from laboratories such as Blackstone Labs, Aviation Consumer, or Savvy Aviation (typically $30–$40 per sample plus shipping) detects wear metals in parts per million before any cockpit symptom appears. Elevated iron and chromium indicate ring, bore, or crankshaft wear; a copper spike can indicate bronze bushing wear at the camshaft, piston pin bosses, or accessory gears; silicon above background level usually means contaminated air is entering the engine. The first sample from a newly inspected or newly overhauled engine establishes your personal baseline — the value is in trending, not in comparing against published averages. Take the sample from the oil drain plug of a warm engine at the oil change portion of your inspection, not from the filler cap.

ContextCooling fin cracks that originate at the base of a fin and propagate outward along its length are common in high-hour Continental and Lycoming cylinders and are generally considered benign unless the separated fin area is large enough to disturb cooling airflow patterns. However, a crack that crosses from the fin area into the barrel/head junction area is a cylinder integrity concern and warrants consultation with a certificated engine shop. Check each cylinder hold-down nut and stud by attempting to rotate the nut by hand with the aircraft at ambient temperature — any looseness on an assembled engine indicates a potential for cylinder base gas leakage. On Lycoming cylinders specifically, inspect the area around the exhaust port base for radiating cracks.

ContextOn Continental engines with solid valve lifters, valve clearance must be physically measured with a feeler gauge at the rocker arm per the relevant engine overhaul manual — the values are typically 0.010 inches for intake and 0.018 inches for exhaust when cold, but verify these against your specific engine model. Exhaust valves with insufficient clearance run hot because they cannot fully seat to transfer heat to the head — this progressively burns the valve face and seat until the valve fails completely, a catastrophic failure mode. On Lycoming engines with hydraulic lifters, excessive valve train noise during runup is the primary indicator; disassembly for physical measurement is warranted if the tick persists after confirming correct oil pressure.

ContextThe engine mount transfers engine thrust, torque, gyroscopic forces, and vibration to the airframe — it is in a continuous state of cyclic stress loading. On welded steel tube mounts, apply dye penetrant at every weld cluster and bracket, focusing on the aft engine mount attach points where they bolt to the firewall and the forward points near the engine case lugs. On conical dynafocal isolation mounts, compress the rubber element between your fingers — serviceable rubber should feel resilient and spring back immediately. Rubber that feels hard, shows surface cracking, or has compressed to a permanently flat profile has lost its vibration isolation function and should be replaced; collapsed mounts allow the engine to shift on its frame, which eventually fatigue-fails fuel, oil, and coolant connections.

ContextBaffles direct the differential pressure between the upper and lower cowl plenums over the cylinder fins, and even a small gap or crack can allow hot air to recirculate rather than exit through the cowl flap or lower cowl opening. Inspect all aluminum or fiberglass baffle panels for cracks at bend radii — these are the highest-stress areas and crack first. The baffle seal material (silicone rubber strip or fiberglass felt) must press firmly and continuously against the cowl's inner surface when the cowl is closed; compressed, hard, or torn seals allow bypass flow that raises cylinder temperatures. Replacement seal material is inexpensive — typically under $30 for a full set — and thermal damage from running hot is not.

ContextThe most effective technique for locating engine compartment leaks is to thoroughly degrease the engine, run it to normal operating temperature (oil at least 170°F), shut down, wait five minutes, then immediately inspect with a flashlight. Fresh oil is dark and wet against a clean surface and locates its source precisely. Verify that all hose clamps sit on the hose body itself, not on a fitting bead or shoulder — a clamp over a bead cannot compress the hose against the fitting barrel and will not seal under pressure. Braided stainless aviation hose (Aeroquip, Stratoflex, Parker) should be replaced at the manufacturer's specified interval — typically five years or 2,500 hours — regardless of external appearance, as the inner liner degrades without visible sign.

ContextBoth magnetos must be verified against the manufacturer's specified timing in degrees before top dead center at the static and/or impulse-coupling firing point per the engine manufacturer's service manual. A magneto that is advanced beyond specification will cause detonation under load, which destroys cylinder heads rapidly and silently — the pilot typically notices only a rough-running engine before cylinder failure. Inspect the ignition leads for contact with or proximity to the exhaust system, where radiant heat can destroy the silicone insulation over one to two seasons. Any lead that shows stiffened, cracked, or melted insulation must be replaced — not taped.

ContextAt approximately 1,800 RPM, switch from BOTH to LEFT, record the RPM drop, return to BOTH, switch to RIGHT, and record the second drop. The FAA general guidance is a maximum of 125 RPM drop on either magneto and no more than 50 RPM difference between the two. A drop significantly greater than 125 RPM on one side indicates a problem on that magneto — bad timing, a failing plug on that side, or a magneto issue. A drop of nearly zero — the engine barely changes — should raise immediate concern that the P-lead on that magneto is open, meaning the magneto cannot be grounded and therefore cannot be shut off in an emergency. Verify the engine actually stops when the key goes to OFF; if it continues to run, the magneto P-lead is broken.

ContextRemove all plugs noting which cylinder and which position (top or bottom) each came from. Aircraft plug electrode gap is typically 0.015–0.019 inches — check your specific engine manual, as this varies by engine and some fine-wire plugs have different requirements. Inspect the ceramic insulator for cracks, the electrode for erosion or deposition, and the threads for damage. Black, sooty deposits indicate rich mixture or oil fouling; white, chalky deposits on eroded electrodes indicate a lean mixture or detonation event. Rotate bottom plugs to top positions and vice versa — bottom plugs run cooler and accumulate lead fouling faster. A plug tester ($150–$300 at aviation suppliers) fires the plug under a pressure that simulates compression and verifies actual firing quality; a plug that appears serviceable may fire weakly or intermittently under load.

ContextA partially blocked air filter enriches the mixture at all throttle settings because the pressure drop across a restricted filter adds to the depression at the carburetor inlet. Service or replace paper filters annually regardless of appearance; oil-bath filters should be drained, cleaned in solvent, dried, and re-oiled. Inspect the entire induction path from filter to carburetor or fuel-injection servo for cracks in rubber sections, loose clamps, and any air leak downstream of the throttle plate. An induction air leak downstream of the throttle plate creates a lean mixture and rough running — squirt a small amount of mineral oil around each joint at idle and watch for a change in RPM as the oil temporarily seals the leak.

ContextExhaust cracks are a carbon monoxide hazard because most EAB aircraft use a heater muff wrapped around the exhaust pipe as the cabin heat source. CO enters the cockpit through any crack in the exhaust downstream of the heater muff. Place a CO detector (available at hardware stores for $20–$30) next to the heater air inlet during a ground runup at full power for three minutes and watch for any reading. Visually inspect all exhaust welds and slip joints — look for concentrated blue-black discoloration or paint burning at a specific point, which indicates a micro-crack allowing hot gas escape. Never weld-repair a cracked exhaust as a permanent solution; the heat cycling reintroduces the crack typically within 20 hours. Replace the affected section.

ContextAluminum tanks develop leaks at seams, baffles, and fittings over time as temperature cycling fatigues the sealant. Place a strong LED flashlight inside the tank through the filler neck in a dimly lit environment and examine all seam lines from outside — fuel staining on the tank exterior is the definitive indicator, but fresh staining may not yet be visible on a previously clean surface. Verify the vent tube inlet is positioned in a pressure-neutral zone and opens downward — a vent facing directly into the airflow can overpressurize the tank at high speed, and a vent that is blocked by insect nesting (extremely common in open-hangar aircraft) will cause fuel starvation by preventing atmospheric pressure from entering as fuel is consumed.

ContextFuel lines must maintain at least 3 inches of clearance from exhaust pipes and components, and greater clearance is better — heat permeates through thin metal and can vaporize fuel in a nearby line, causing vapor lock at the worst possible moment. Any fuel staining around a fitting indicates a seeping connection that must be corrected before the next flight. Translucent automotive-style plastic fuel lines commonly used on some homebuilt designs become brittle and crack-prone from fuel absorption and UV exposure after 5–7 years and should be replaced proactively, regardless of appearance, as they can fail without warning.

ContextThe gascolator is the final filtration point before fuel reaches the engine. Drain it completely into a clean, clear container and examine carefully under good light: water appears as a distinct lower layer below the fuel, rust particles settle as reddish-brown sediment, and sealant chunks indicate the tank interior sealer is breaking down and must be addressed at the tank. The bowl gasket should seal with no weeping when the fuel system is pressurized — open the fuel shutoff, fill with a full tank, wait two minutes, and check. A seeping gascolator bowl will supply air into the fuel system and cause lean-out at altitude or at high fuel flow.

ContextThe fuel selector must snap positively into each labeled position with a clear mechanical detent, and must not be capable of resting in an intermediate position between detents. A selector that can rest between LEFT and BOTH, for example, can allow partial or complete fuel starvation even with full tanks. Cycle through all positions deliberately and verify each detent engages with firm resistance that requires intentional force to leave. Also verify that the cockpit labeling matches the actual plumbing by tracing each port — transposed fuel lines during original build (LEFT label connected to the right tank physically) is a documented accident cause that may not be discovered until a single-tank fuel exhaustion emergency.

ContextOn wood propellers, inspect each blade for surface checks (fine crazing in the finish varnish, especially near the tip), separation of the fiberglass leading edge tape from the wood core at the bond line, and any swelling or dark spots indicating moisture ingestion. Any nick in the leading edge, however small, must be dressed with a fine file to a smooth 'U' or 'V' profile per the propeller manufacturer's instructions — a sharp nick is a fatigue crack initiator, and propeller blade failures are catastrophic. On composite propellers, inspect the blade skin-to-core bond line within 12 inches of the tip, where centrifugal acceleration is highest and disbonding consequences are most severe. Any crack that cannot be confidently attributed to surface finish damage should be sent to the manufacturer for evaluation.

ContextPropeller torque values are unique to each hub-and-flange combination and are not interchangeable — never apply a generic 'wood propeller torque' or 'composite propeller torque' value. Obtain the specific in-lb or ft-lb value from your propeller manufacturer's installation manual for your exact prop and engine flange type. Under-torqued prop bolts allow micro-movement of the propeller on the flange that progressively elongates the bolt holes, eventually requiring a new hub or flange. Over-torqued bolts split wood hubs and crack composite flanges. After torquing, apply torque-seal (witness marks) across each bolt head to the flange face so you can see at preflight whether any bolt has backed off.

ContextSpinner cracks almost always initiate at the blade cutout corners, which are stress concentrations under the aerodynamic and gyroscopic loads the spinner experiences. Inspect the corner radius of each blade cutout with strong side-lighting and look for cracks radiating from the corners — these should be considered unairworthy and the spinner replaced. The spinner bulkhead (typically a machined or formed aluminum plate) should be inspected at all bolt holes for cracks and at the interface with the propeller flange for fretting; a loose or wobbling bulkhead allows the spinner dome to vibrate asymmetrically, which accelerates cracking further.

ContextWith the engine cold and the aircraft level, establish a fixed reference point just beneath the propeller arc (a block of wood on a stable surface, or tape on the hangar floor marked directly beneath the prop tips). Rotate the propeller and bring each blade tip to the same position adjacent to the reference, measuring the height of each tip relative to your reference. All blade tips should sweep within 1/16 inch of each other; greater variation indicates a blade is out of track. A change in track since the previous inspection — especially if the track was good before — almost always means a prop strike occurred. Prop strikes must be documented, and many manufacturers require the prop be removed and inspected regardless of visible damage before the next flight.

ContextSpring steel gear legs (standard equipment on Van's RV designs and many others) are inspected for scratches and nicks whose sharp edges initiate fatigue cracks under the cyclic bending loads of landing — dress all nicks with a smooth file before they become crack origins. Inspect the gear leg socket in the fuselage main spar or attach block for cracks at the weld line and around the bolt holes, and verify all attach bolts are torqued correctly. Composite gear legs (fiberglass or carbon fiber) should be tapped with a coin along their length — listen for a change in tone that indicates delamination or resin cracking, particularly at the bow radius where bending stress is highest and where a hard landing compresses the composite beyond its elastic limit.

ContextOn aircraft using a bungee-and-tube gear frame (common on Piper Cub derivatives and many scratch-built designs), apply dye penetrant to every weld cluster in the gear frame at each condition inspection. Hard landings are part of the aircraft's service life; the gear structure is designed to accommodate them, but repeated hard landings accumulate fatigue damage. Bungee cord material (natural or synthetic rubber) hardens and loses elasticity over time — a hardened bungee provides less shock absorption and increases peak structural loads at the moment of touchdown. Compare the bungee compliance (compress the gear by hand) against your memory or notes from previous inspections; a noticeably stiffer feel indicates the bungees need replacement.

ContextAircraft tires fail differently from automotive tires: flat-spotting from aggressive braking is more common than tread wear, and sidewall cracking from UV and ozone exposure is the dominant aging failure mode. A tire that looks acceptable on tread depth may have deep sidewall cracks indicating it is at or past the end of its safe service life — probe the sidewall cracks with a fingernail; if they can be seen but not felt, they are surface checks; if they open when the sidewall is flexed, the tire should be replaced. Most operators apply a five-year calendar replacement regardless of apparent condition. Verify inflation against the aircraft builder's specified pressure — an under-inflated tire flexes excessively under load, overheats, and can separate from the rim on the rollout.

ContextBrake pad minimum thickness is typically marked on the caliper body or specified in the brake manufacturer's maintenance guide — do not operate past this limit. Brake discs showing deep radial grooves need to be turned or replaced. A pattern of localized blue-black heat discoloration at one angular sector of the disc indicates a dragging brake caused by a seized caliper piston; the root cause must be corrected, not just the disc resurfaced. Brake hydraulic fluid in most EAB aircraft is MIL-H-5606 (red mineral oil) — pink staining on the gear leg or wheel well indicates a hydraulic leak at a line fitting or caliper seal that must be resolved before flight.

ContextGrasp the tire at the 12 and 6 o'clock positions and attempt to rock it toward and away from the fuselage centerline — any detectable lateral play indicates worn or un-preloaded wheel bearings. Remove both wheels, pull both bearing cups, clean them in mineral spirits, and inspect the bearing races under magnification for pitting, spalling, or surface rust. Repack with MIL-G-81322 aviation wheel bearing grease or an equivalent — do not substitute automotive wheel bearing grease, which is formulated for different temperature and load profiles. Pack grease into the bearing evenly but not excessively: over-packed bearings force grease past the seal onto the brake disc during the first hot brake cycle, contaminating the pads. Re-torque the axle nut with a new cotter pin.

ContextOn tricycle-gear aircraft, check nose gear strut extension against the normal range (aircraft sitting level on the mains with the nose gear compressed to about two-thirds of its travel), inspect the shimmy damper for fluid leakage and correct preload, and verify steering linkage end-stops prevent over-travel that would cause ground loop tendency. On tailwheel aircraft, inspect the tailwheel fork and yoke for cracks at weld points, check the spring for fatigue deformation or cracks at its bend radius, and verify the steerable tailwheel lock (if fitted) engages positively. A tailwheel that shimmy-oscillates during rollout or has intermittent steering authority is a significant ground-handling hazard and requires correction before the next solo flight.

ContextSeat failure during a crash sequence is a major contributor to fatal injuries in otherwise survivable accidents. Inspect the seat frame — typically a welded tubular steel or machined aluminum structure — for cracks at stress concentrations and at any weld. On sliding seat installations, verify the locking pin positively engages the rail detent at every fore-aft position with enough force that it cannot be accidentally displaced by a sharp control input; a seat that shifts aft during the takeoff roll is a loss-of-control accident in progress. The rail attach bolts carry both normal flight loads and crash loads, and must be verified at their correct torque.

ContextWebbing degrades from UV exposure, chemical contact, and repeated loading cycles — look for fraying at edges, cuts or abrasion at contact points with metal hardware, and fading beyond normal wear. TSO-C22 guidance recommends replacing aircraft safety belts 12 years from the manufacture date stamped on the webbing or hardware. Inspect the attach bolt hardware — typically AN3 or AN4 bolts through the seat structure or fuselage floor — for proper installation, thread engagement, and absence of bending. The buckle mechanism must release cleanly with one hand and must not release under firm longitudinal tension simulating a crash-load impulse.

ContextAcrylic crazing — the fine network of surface micro-cracks that clouds the optical clarity of a canopy — is caused by UV exposure, solvent-based cleaning products (Windex, automotive glass cleaner), and hydrocarbon fuel contact. A crazed canopy has substantially reduced impact resistance compared to clear acrylic and should be replaced. Clean aircraft canopies only with dedicated aviation canopy polish and a clean, dry microfiber cloth. Any crack originating from a mounting fastener hole is a stress riser — stop-drill the tip of the crack with the smallest drill bit that encompasses the crack tip to prevent further propagation, then evaluate whether the panel can remain in service. Pull the canopy latch firmly from outside to verify it holds under a realistic load and does not creep open from vibration.

ContextExperimental aircraft carry specific placard requirements: the 'EXPERIMENTAL' legend must be posted near each entrance and be visible from both inside and outside the aircraft. Airspeed indicator arc markings that differ from standard certified aircraft colors must be supported by a placard explaining the deviation. Any instrument that is not certified for IFR use must be placarded 'NOT FOR IFR USE' on VFR-only operating-limited aircraft. Review your operating limitations — they may specify additional required placards unique to your aircraft's certification. A missing 'EXPERIMENTAL' placard is a ramp-check violation regardless of the aircraft's mechanical condition.

ContextWith an assistant working the stick or yoke and rudder pedals to each extreme of their travel while you watch from outside, confirm that each control surface reaches its correct maximum deflection and moves in the correct direction. Verify there is no binding at the corners of stick travel — full aft-right, full forward-left, and all intermediate diagonals. A binding at a specific position that was not present at the previous inspection indicates a control cable or pushrod has shifted its routing and is now contacting structure at that deflection angle. The cause must be identified and corrected; reduced control authority at full deflection is a critical safety limitation.

ContextA battery at rest may show 12.6V while completely unable to deliver starter current — voltage is an unreliable indicator of battery health; a load test (applying a half-capacity load for 15 seconds and measuring the voltage depression) is the only valid servicability check. Sealed lead-acid batteries typically last 3–5 years in aircraft service and should be replaced proactively at the 4-year mark regardless of apparent condition. Inspect the battery box for white crystalline deposits indicating acid vapor outgassing from a stressed battery, and verify the hold-down strap or bolt prevents any movement — a loose battery in a crash becomes a heavy, acid-spilling projectile.

ContextMost electrical problems in homebuilt aircraft trace to high-resistance connections rather than component failures. The engine-to-airframe ground strap is particularly critical: if it fails, all engine electrical return current must find an alternative path, typically through control cables, fuel lines, or steel tubing — causing hidden corrosion and in rare cases electrical arc damage. The strap should be short, use a large wire gauge (at least 4 AWG), and make contact at both ends with bare metal, not paint. All bus bar connections should show bright, oxide-free metal at the contact face; apply Kopr-Shield or equivalent to all aluminum-to-copper connections.

ContextA circuit breaker replaced with a higher-amperage unit to stop nuisance tripping is a significant fire hazard — the wire gauge it protects was chosen to carry a maximum current safely, and a higher-rated breaker allows that wire to carry enough current to overheat and ignite insulation before the breaker opens. Verify each breaker against the aircraft's electrical schematic, which should show the wire gauge and the design current for each circuit. Breakers that trip repeatedly without an obvious short circuit should be investigated for cause — they are detecting a real overcurrent event.

ContextWire insulation failure is the most common cause of avionics failure and a significant electrical fire initiator in homebuilt aircraft. Follow each wire bundle systematically and look for contact with structure edges, sharp brackets, or cable runs. All bundles must be supported with clamps or tie-wrap loops at intervals no greater than 12–18 inches and must never contact sharp edges without chafe protection (split plastic tubing or spiral wrap). Pay specific attention to the engine compartment, where radiant heat from the exhaust system cycles the insulation through temperature extremes that cause embrittlement. Wire that shows discoloration, is unusually stiff, or crumbles when flexed must be replaced.

ContextActivate each light individually from its cockpit switch and verify operation by walking around the aircraft. Navigation lights or strobes that flicker or require switch cycling to activate have a failing socket contact, corroded connection, or degrading LED driver module. A burned-out navigation light is a daytime ramp-check violation and a genuine safety issue at night over unlit terrain. For HID and high-power LED landing lights, verify connector security — these lights draw high current through connectors that warm with each use, and repeated thermal cycling loosens the connector's grip on its pins over time.

ContextInsects, particularly mud dauber wasps, commonly construct nests inside pitot tubes stored in warm hangars — a fully blocked pitot will cause the airspeed indicator to freeze at the last reading on climb and overread on descent due to trapped static pressure. Verify the tube is clear by blowing gently from the aft (open, unconnected) end and feeling for resistance. Never blow into the pitot tube hose with the airspeed indicator still connected — the sudden pressure surge can rupture the indicator diaphragm (repair cost: $200–$600). Verify the tube's angle relative to the fuselage nose-down attitude: most pitot tubes are designed to work accurately within ±5 degrees of alignment with local airflow at normal cruise attitude.

ContextBlocked static ports affect the altimeter, airspeed indicator, and vertical speed indicator simultaneously. The most common blockage cause is paint overspray during a touch-up job — a single coat of paint can almost completely seal a 1/16-inch static port. To test system integrity, disconnect the static line at an instrument (or use a static port cover tool with a hand pump) and apply gentle suction — the altimeter needle should rise as the system sees reduced pressure. Maintain that reduced pressure for at least one minute; a system that bleeds back to ambient indicates a leak somewhere in the static lines or at an instrument connection, introducing altitude errors into the altimeter.

ContextThe ELT battery replacement date is stamped on the battery label and is based on either cumulative transmit time (typically after 1 hour of use) or the calendar date printed, whichever comes first — confirm both. Pull the antenna connection at the ELT body and verify the coaxial connector is clean and properly seated; a poor antenna connection reduces transmitted power dramatically. Confirm your aircraft is registered in the NOAA 406 MHz beacon database at beaconregistration.noaa.gov — an unregistered 406 MHz ELT activation triggers a search-and-rescue response, which is legally and financially your responsibility.

ContextActivate the ELT self-test per the manufacturer's procedure (typically during the first five minutes of any UTC hour to avoid generating a false alert, or after coordination with the local ARTCC). If a remote annunciator is installed, verify it illuminates during the test transmission cycle. Note that the self-test does not confirm that the 406 MHz emergency beacon frequency is actually being transmitted at the correct power; only a 406 MHz-capable monitor can confirm this, though the self-test does verify the 121.5 MHz homing signal.

ContextAircraft fire extinguishers should be the halon or halon-replacement type (e.g., Halotron) rated for aviation use — not the dry chemical (ABC-rated) automotive variety, which deposits a highly corrosive powder that damages aluminum structure and avionics. Verify the pressure gauge needle is in the green zone and the safety pull-pin is intact and untampered. The extinguisher must be mounted within arm's reach of the seated pilot — on the left sidewall between the pilot and instrument panel, or under the panel — and the mount must hold it securely under turbulence loads. Replace any extinguisher older than 12 years from its manufacture date regardless of gauge reading.

ContextEvery discrepancy found during the inspection — including items corrected immediately on the spot — should be entered in the logbook with enough detail for a future inspector to understand what was found, what was done, and what materials or parts were used. 'Tightened loose nut' is insufficient; 'Tightened #10-32 jam nut on left aileron pushrod rod end to 20 in-lb, applied torque seal' is a serviceable entry. Photograph every finding in its discovered condition before any work, and photograph the completed correction after. These photographs attached to the logbook entry are your legal shield in the event of a future incident involving that system, and they provide honest provenance history for any future buyer.

ContextAny change in onboard equipment — even swapping one avionics unit for another of slightly different weight, removing a back seat for solo cross-countries, adding a camera mount or EFB bracket — changes the aircraft's loaded center of gravity. The updated W&B calculation must be dated, signed, and stored in the aircraft along with the measurement data. Flying outside the approved W&B envelope specified in the operating limitations is a serious safety risk and typically voids the condition inspection sign-off for any flight in that loading condition. If significant equipment changes have accumulated over several inspections without a formal reweigh, place the aircraft on calibrated scales and reestablish the baseline.

ContextThe sign-off logbook entry must include: the date of inspection completion, total airframe time in hours at inspection, a specific statement that the aircraft was inspected in accordance with its operating limitations and found to be in a condition for safe operation (or a list of specific items that remain unairworthy and have been grounded pending repair), your full name, your repairman certificate number or A&P certificate number and IA designation as applicable, and your signature. A logbook entry that says only 'condition inspection completed, aircraft airworthy' with no certificate number is legally insufficient and can be challenged as incomplete. If any item remains unresolved, it must be listed explicitly — do not sign an unqualified 'condition for safe operation' statement with open discrepancies.

ContextBefore reinstalling all panels and closing the cowl, physically confirm that the following are in the aircraft: the original pink special airworthiness certificate, the current aircraft registration certificate, the operating limitations document, and (for international operations) the radio station license. Your pilot certificate and medical certificate or BasicMed documentation are required to be in your personal possession, not in the aircraft. The operating limitations document is the aircraft's governing document — it must be physically present during every flight, as it cannot be reproduced from memory during a ramp check.