Abnormal Events
Mandatory conditional inspections after a lightning strike, HIRF penetration, a heavy or overweight landing, and severe turbulence.
Abnormal events, summary notes
- Certain in-service events require a special ('conditional') inspection to the manufacturer's instructions before the aircraft returns to service, because they may have overstressed or damaged the structure or systems in ways not found by routine checks.
- LIGHTNING STRIKE: examine the extremities for entry/exit burn and pit marks, wing tips, tail, radome, static wicks, antennas, propeller or rotor tips. Check skins for arcing, burning and pinholes; bonding and static wicks for damage and continuity; and avionic, electrical and navigation systems, including the compass, for damage or magnetisation. Composite areas need particular attention as damage may be internal.
- HIRF penetration is inspected similarly for effects on avionic and electrical systems.
- HEAVY / HARD (OVERWEIGHT) LANDING: inspect the landing gear and its attachments for distortion, cracking, strut leaks and tyre/wheel damage; the wing and fuselage structure and attachments; the engine mounts and pylons; and look for wrinkled skin, popped or sheared rivets, and deformed frames or spars.
- SEVERE TURBULENCE / OVER-G: inspect the wing, empennage and their attachments and high-load components for overstress, again to the manufacturer's conditional-inspection schedule.
- The extent of inspection escalates with the recorded severity, established from the flight-crew report and any recorded flight-data.
- Findings are assessed against repair limits, and the event and the inspection are documented before release to service.
- ⚠ Exam trap: the greater lightning threat to avionics is the INDIRECT effect (induced transients), and a hard landing focuses first on the landing gear and its attachments.
- Rule
- conditional inspection to the manufacturer's instructions before return to service
- Lightning
- burn/pit marks at extremities · bonding & wick continuity · avionics & compass
- Hard landing
- gear and attachments first · then wing/fuselage structure and engine mounts
After a reported hard landing, where does the inspection concentrate first and what is looked for?
On the landing gear and its attachment structure, checking for distortion, cracking, shock-strut leaks and tyre or wheel damage, then the wing and fuselage structure, engine mounts and pylons, looking for wrinkled skin, popped or sheared rivets and deformed frames.
Why do composite areas need particular attention after a lightning strike?
Composites are not naturally conductive, so lightning energy can cause internal delamination, resin damage or damage to the embedded conductive mesh that is not visible on the surface. Special inspection, often tap test or ultrasonic, is needed to find damage that a visual check would miss.
Abnormal events concept map
Abnormal Events
Abnormal events quiz
Abnormal Events, quiz
1. A hard (overweight) landing requires:
A special structural inspectionNo actionOnly a logbook note2. A special inspection after an abnormal event is carried out to:
The manufacturer's conditional-inspection instructionsThe pilot's judgementAny convenient checklist3. After a lightning strike, burn and pit marks are sought at the:
Extremities, tips, radome, wicksCabin floorFuel tanks only4. A hard landing inspection concentrates first on the:
Landing gear and its attachmentsCabin trimAvionics cooling5. The greater lightning threat to avionics is the:
Indirect effect, induced transientsBurn mark at the attachment pointNoise6. After a lightning strike, composite areas need special attention because:
Damage may be internalThey cannot be struckThey are always replaced7. The extent of an abnormal-event inspection is set by:
The recorded severityThe time availableThe aircraft age only8. After a hard landing, wrinkled skin and popped rivets indicate:
Structural overloadNormal wearA paint fault