How Lightning Strikes Affect Aviation
How Lightning Strikes Affect Aviation Capt. Martin Brodbeck Head of Flight Operations Engineering Swiss International Air Lines Ltd. SEREC, October 14, 2011 Content − Examples of lightning strike events − How aircraft are struck by lightning − Protections on aircraft against lightning strikes − Regulations for airport and flight operations − Effect to the aircraft, structure and systems − Behavior of new material like CFRP − Checks required by maintenance after a lightning strike − Summary 2 Examples of lightning strike events Navigation system failure FedEx MD-11 freighter, had departed from Hong Kong and was already enroute when the crew recognized a navigation system failure, that the crew suspected had been caused by an earlier lightning strike during departure. The crew returned to Hong Kong for a safe landing. (aviationherald.com) Fuel dumping Virgin Atlantic Airbus was climbing out of London Heathrow when a lightning struck the airplane, the crew decided to return to Heathrow Airport but dumped fuel before land. (aviationherald.com) 3 Examples of lightning strike events Engine failure (temporarily) A SWISS Airbus experienced lightning strike while on approach. One engine temporarily failed. The crew decided to abort the landing and divert to an airport with maintenance support. An examination of the airplane revealed no damages. The airplane resumed journey, about half of the passengers preferred to fly on another airplane. (SWISS) Effects on Material A SWISS Avro RJ100 during approach encountered a heavy lightning strike on the forward left side of the cockpit. The strike was noticed as a very loud bang with a heavy flash. The aircraft was inspected and several burned spots were detected in forward left zone. (SWISS) 4 Content − Examples of lightning strike events − How aircraft are struck by lightning − Protections on aircraft against lightning strikes − Regulations for airport and pilot operations − Effect to the aircraft, structure and systems − Behavior of new material like CFRP − Checks required by maintenance after a lightning strike − Summary 5 How aircraft are struck by lightning − In Cumulonimbus clouds static charges are build up − An aircraft passing through this zone can initiate a discharge Lightning Strike − It mostly occurs within 5’000 feet of the freezing level − Effects are: brilliant flash of light, smell of burning material and noise − Physical damage to an aircraft is rare − However, damage can occur to avionics and fuselage Safety not threatened! 6 Content − Examples of lightning strike events − How aircraft are struck by lightning − Protections on aircraft against lightning strikes − Regulations for airport and pilot operations − Effect to the aircraft, structure and systems − Behavior of new material like CFRP − Checks required by maintenance after a lightning strike − Summary 7 Protections on aircraft against lightning strike Manufacturing regulations Aircraft manufacturing regulations require proper protection against catastrophic effects from lightning: − Minimise accumulation of electrostatic charge − All important metal parts have to be bonded to the main earth system − Fuel system designed to prevent the ignition of fuel vapour in tanks by lightning strike − Make sure that functions whose failure would affect a safe flight are not adversely affected when aeroplane is exposed to lightning 8 Protections on aircraft against lightning strike Fly by wire technology Advantages against conventional flight controls: − Easy handling, good stability − Overspeed protection, stall, windshear protection − Maintenance costs reduced Problems: − Signals to control surfaces via wires not cables Protection against lightning strike mandatory Protection measures: − Wires are twisted and in metal shields in the exposed areas − Computer in- and outputs are protected against the most severe spikes These protections + precautions in the software ensure good protection. 9 Protections on aircraft against lightning strike Electrostatic discharger Electrostatic discharger to reduce electrostatic load 1) 10 2) Protections on aircraft against lightning strike Diversion straps Diversion straps on keflar type radome 3) 11 Content − Examples of lightning strike events − How aircraft are struck by lightning − Protections on aircraft against lightning strikes − Regulations for airport and flight operations − Effect to the aircraft, structure and systems − Behavior of new material like CFRP − Checks required by maintenance after a lightning strike − Summary 12 Regulations for airport and pilot operation If lightning strike activity exists over the airport the following restrictions apply to the servicing of an aircraft: − Stop work outside the aircraft (loading, catering) − No Start Up / Push Back of the aircraft − No connections between airplane and ground (electrical supply, headset communication) − Entry and exit only via jetway (not by metallic stairs) 13 Regulations for airport and pilot operation Flight Operations Following rules from the operations manual apply, when aircraft is exposed to lightning: − Airport ground personell should not communicate to cockpit via interphone system − Avoid thunderstorms with lightning activity by a distance of 20 NM detected by weather radar 4) 14 Regulations for airport and pilot operation Pilot − Switch on cockpit lights to full brightness − Note actual gear position − File an air safety report 15 Regulations for airport and pilot operation Air Safety Report (ASR) 5) 16 | Change content using menu “Insert", "Header & Footer" Regulations for airport and pilot operations St. Elmo’s fire www.youtube.com 17 Content − Examples of lightning strike events − How aircraft are struck by lightning − Protections on aircraft against lightning strikes − Regulations for airport and pilot operations − Effect to the aircraft, structure and systems − Behavior of new material like CFRP − Checks required by maintenance after a lightning strike − Summary 18 Effect to the aircraft, structure and systems Areas where lightning strike is most probable 6) 19 Effect to the aircraft, structure and systems Possible damage − Pitting/meltthrough − Scorch marks, paint discoloration, skin puncturing, deformation of fibre − Resistive heating − When lightning currents flow through structure, the energy is changed into heat weld type marks − Acoustic shock wave − If intesity is high, deformation of thin metal skin 20 Effect to the aircraft, structure and systems Possible damage − Magnetic force − Damage in small areas, were the density of the current is high e.g. a bonding lead installed at a control surface hinge − Electromagnetic fields − Unwanted transient voltages and currents in aircraft wiring and systems Crew and passengers are not in danger as the aircraft is a kind of Faraday Cage! 21 Effect to the aircraft, structure and systems Damage examples to an aircraft (Avro RJ100) 7) 8) 22 Effect to the aircraft, structure and systems Damage examples to an aircraft (Airbus A300) 9) 23 Content − Examples of lightning strike events − How aircraft are struck by lightning − Protections on aircraft against lightning strikes − Regulations for airport and pilot operations − Effect to the aircraft, structure and systems − Behavior of new material like CFRP − Checks required by maintenance after a lightning strike − Summary 24 Behavoir of new materials like CFRP Carbon Fiber Reinforced Plastic benefits …to the User …to the Designer Reduced weight Fatigue & Corrosion resistant Design flexibility …to Manufacturing Reduced fuel consumption Fewer & easier inspection Reduced maintenance cost Longer life 25 Fewer parts Reduced production cost Manufacturing flexibilty Behavoir of new materials like CFRP Carbon Fibre Reinforced Plastic benefits − New aircraft types like B787, A350 and CSeries are using CFRP − Possibility and Severity of Lightning Strike to a CFRP airframe is equivalent to metallic frame − CFRP is 1’000 times less conductive than aluminium. Thin CFRP fuselage panels risk a delamination of the layers in addition to burn marks More energetic pulses on the wiring Solution: Copper or bronze metallic foil on external face of the panel restore good conductance 26 Behavoir of new materials like CFRP Protection test − High current generator loaded under about 70kV − Generator connected to an electrode − Electrode installed 10 to 15 cm above the panel − Panel is connected back to the other pole of generator 27 Behavoir of new materials like CFRP Comparision CFRP panel without protection CFRP panel with bronze mesh 10) 28 11) Behavoir of new materials like CFRP Horizontal stabilizer solution Structure Lightning Strike Protection Carbon monolithic Bronze mesh Carbon sandwhich Aluminium straps Aluminium part Bonding braid 12) 29 Behavoir of new materials like CFRP CFRP Fuselage part 13) 30 Content − Examples of lightning strike events − How aircraft are struck by lightning − Protections on aircraft against lightning strikes − Regulations for airport and pilot operations − Effect to the aircraft, structure and systems − Behavior of new material like CFRP − Checks required by maintenance after a lightning strike − Summary 31 Checks required by maintenance after lightning strike Checks according to manufacturer maintenance manual: − Inspection of aircraft surface to find strike areas − Inspect strike areas, type and quantity of damage − Repair of damage and perform system checks Aircraft is only allowed to re-enter service, after all these procedures have been performed. 32 Checks required by maintenance after lightning strike Example of temporary repair of a burned whole with a rivet. 14) 33 Content − Examples of lightning strike events − How aircraft are struck by lightning − Protections on aircraft against lightning strikes − Regulations for airport and pilot operations − Effect to the aircraft, structure and systems − Behavior of new material like CFRP − Checks required by maintenance after a lightning strike − Summary 34 Summary Lightning strike in aviation is a regular event, however: − Precautionary measures are imperativ − It can be distressing to crew and passengers − After encountering a lightning strike maintenace action is required − It is not threatening flight safety 35 Thank you for your attention QUESTIONS? 36 Picture Sources 1,4) www.flightforum.ch 2) www.wikipedia.org 3) www.amevoice.com 5,7,8,14) SWISS 6,9-13) 37 Airbus 38 | Change content using menu "View", "Header and Footer"
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