7.19 Abnormal Events Flashcards
How and when can lightning strike an aircraft?
Lightning can strike aircraft at altitudes of 8000 ft to 14,000 ft, often over land or water due to weather changes caused by landmasses.
Most lightning occurs in the tropics, and strikes are likely when flying through areas with large charges, such as clouds or precipitation.
What are the stages of a lightning strike and its effects on aircraft?
Lightning strikes produce a current in the aircraft skin that generates voltages across joints, potentially causing sparks near fuel tanks and leading to explosions.
Modern aircraft construction and electrical bonding have reduced incidents of ignition from lightning strikes.
What areas does a lightning strike conditional inspection cover?
Inspection covers:
* Nose section and radome
* Engine nacelles
* Wing tips
* Horizontal stabiliser tips
* Vertical fin tip and rudder tip
Areas less likely to experience strikes include drain masts, pitot probes, and landing gear.
What is High-Intensity Radiated Fields (HIRF) penetration?
HIRF penetration refers to the effect of electromagnetic radiation that can disrupt aircraft electronics and avionics.
HIRF can be caused by external sources like radio transmitters or internal equipment operating at certain frequencies.
What is the likelihood of a lightning strike on an aircraft?
A lightning strike on an aircraft occurs approximately every 3000 flying hours.
Lightning strikes vary in intensity and duration, with aircraft designed for high-intensity strikes.
What types of damage can lightning strikes cause to aircraft?
Lightning strikes cause:
* Direct damage (burned, melted metallic structures)
* Indirect damage (disruption to electrical/electronic systems)
Direct damage includes visible signs like melt marks and pitting, while indirect damage affects system operation.
What are the visual signs of direct damage from a lightning strike?
Signs include:
* Small circular melt marks
* Holes of 1/4 in (6 mm) or greater
* Burned or discolored paint
* Damaged fasteners
Composite components may show discolored paint or delaminated structures.
What is the purpose of lightning strike diverter strips?
Diverter strips are used to conduct lightning strikes away from sensitive areas like the radome into the aircraft structure.
They help protect composite structures from catastrophic damage.
What should be examined during an inspection for direct damage caused by lightning?
Inspect for:
* External and internal damage
* Holes or pits on metallic structures
* Damage on honeycomb sandwich structures
* Static dischargers for burns or damage
Ensure bonding straps of the radome are correctly attached.
What types of antennas should be checked for damage after a lightning strike?
Check:
* High-Frequency radio (HF)
* Very High-Frequency radio (VHF)
* VOR
* DME
* ATC Transponders
* ILS
* ADF
* ELT
* RA
* ACARS
* GPS
* SATCOM
* TCAS
All radio and navigation systems must be examined.
True or False: High-intensity lightning strikes can cause indirect damage to electrical systems.
True
Indirect damage occurs due to large electrical transients affecting wiring and systems.
What is a common result of ferrous components becoming magnetized after a lightning strike?
It can affect magnetic instruments like compasses, requiring degaussing and a compass swing.
Non-ferrous fasteners are used in sensitive areas to prevent magnetization.
Fill in the blank: Static dischargers on aircraft dissipate _______ that builds up due to friction with airflow.
[static charge]
They help prevent interference in aircraft radio receivers.
What are the three primary areas to consider for HIRF protection integrity?
Consider:
* Aircraft structure
* Electrical wiring installation protection
* Equipment protection
Maintaining these areas is crucial for continued airworthiness.
What steps should be taken if HIRF penetration is suspected?
Conduct:
* Functional tests of all systems
* Inspection of electrical bonding system
* Checks of static dischargers
* Degaussing if magnetizing is suspected
Inspections should focus on the bonding and shielding integrity.
What is the Maximum Design Landing Weight (MDLW)?
The maximum weight at which an aircraft is designed to land safely without structural damage.
What is the primary indicator of a heavy landing?
A wrinkled or creased wing skin.
What must be performed if the flight crew reports a heavy or rough landing?
A special inspection to determine if the aircraft exceeded the MDLW.
What are the common areas checked during a Phase I inspection after a hard landing?
- Main Landing Gear (MLG) Struts
- Structural Components
- Skin wrinkles
- Popped rivets
- Buckles
- Missing fasteners
- Damaged access panels
- Leaks
What defines an overweight landing?
A landing made at a gross weight in excess of the maximum design landing weight for a particular model.
True or False: A smooth landing does not require a special inspection if it is overweight.
True.
What is the purpose of a Phase II inspection?
To conduct a more detailed inspection if damage is indicated during a Phase I inspection.
Fill in the blank: Common areas checked during an overweight landing inspection include __________.
- Wrinkled Wing Skin
- Fuel Leakage
- Spar Webs
- Bulkheads
- Nacelle Skin
- Firewall Skin
- Stringers
What should be checked in the landing gear during a hard landing inspection?
- Tyres for excessive creep, damage, or cuts
- Wheels/brakes for cracks or other damage
- Axle struts and stays for distortion
- Leaks, scoring, and abnormal extension
- Gear attachments for cracks or movement
What happens to the aircraft structure when exposed to higher heat than normal operations?
The strength of the structure can severely degrade.
What type of inspection follows a flight through severe turbulence?
A special inspection covering all critical areas of the aircraft.
What are the signs of structural damage after severe turbulence?
- Excessive buckles or wrinkles in wing surfaces
- Sheared rivets or attachments
- Buckling in nacelles and nacelle skin
What is the significance of accelerometers and flight data recorders in aircraft inspections?
They provide better indications of loads sustained but do not give a full overview.
Fill in the blank: Any totally submerged parts must be __________ before the aircraft can be considered airworthy again.
completely disassembled, thoroughly cleaned, dried, and treated with a corrosion inhibitor.
What is a common consequence of water acting as an electrolyte in aircraft?
Corrosion.
What is the primary goal of a Phase I inspection?
To determine whether further inspections are necessary.
What should be inspected in the empennage during a hard landing inspection?
- Controls for freedom of movement
- Hinges for distortion or cracks
- Attachments and fairings
What does a visible or non-visible damage from fire or intense heat require?
Repair or replacement.
