Incident Overview
On March 12, 2010, at approximately 1804 central standard time, an Embraer EMB-145LR, registration N16561, operated by ExpressJet Airlines as Flight 5685, sustained a lightning strike while on approach to runway 4R at O'Hare International Airport (ORD), Chicago, Illinois. The aircraft received minor damage. The flight crew encountered elevator control binding but landed without further incident. There were no injuries to the two pilots, one flight attendant, or the 42 passengers. The flight was conducted under 14 CFR Part 121 in visual meteorological conditions on an activated instrument flight rules flight plan. The flight had departed from Greenville Spartanburg International Airport, South Carolina, about 1650, destined for ORD.
Flightcrew Reports
The captain reported that the aircraft was on the ROYKO 3 arrival when it was struck by lightning at an altitude of 7,000 feet MSL near the MONKZ fix. Chicago Approach was notified, and the aircraft was assigned a heading of 270. The autopilot disengaged automatically after the strike. The first officer hand-flew the aircraft. The primary flight display and multifunction display colors changed to red, purple, green, blue, and white, but all information remained correct. During the flare at about 100 feet AGL, the first officer noted that the control column would not move forward from a position approximately 60 percent pulled back. The captain attempted to push forward without success. The aircraft landed in the touchdown zone, and the landing was uneventful. The first officer added that during the flare at 10-20 feet AGL, increased pressure was needed to lower the nose, and the yoke could be pulled aft but not pushed forward past about 60 percent.
Damage Examination
Post-flight inspection revealed damage to the tailcone. The tailcone, a monocoque fiberglass assembly with two internal frames and copper foil skin, had an internal bulkhead that came to rest on the elevator bellcrank. Examination by an NTSB aerospace engineer found missing paint on the aft portion of the t-tail fairing near the navigation light assembly, with visible expanded metal foil. The paint was also missing at the forward end of the fairing. Embedded and deformed copper foil was visible near fastener holes. A screw attaching the navigation light lens showed melting. The upper right navigation light receptacle was melted. The back plate's wire harness was burned through. Two bonding jumpers were attached to the navigation light fixture back plate, one with arc pitting. The internal aluminum bulkhead was separated and loose inside the fairing, with some rivets pulled through their holes and a crack in the bottom pointed end.
Weather Conditions
The NTSB Meteorological Factual Report indicated that the area was under overcast skies with light rain and mist. At 1802, Chicago Midway International Airport (MDW) reported wind from 030 degrees at 13 knots, visibility 4 miles, light rain and mist, broken ceiling at 1,100 feet, and overcast at 1,600 feet. At 1806, MDW reported thunderstorms and light rain with mist, cumulonimbus clouds. Lightning data from the National Lightning Detection Network (NLDN) detected two cloud-to-ground strokes within 15 miles between 1730 and 1830, but neither was coincident with the aircraft. The WeatherBug Total Lightning Network (WTLN) detected four cloud-to-ground and two intracloud strokes, with one cloud-to-ground occurring within one second and one mile of the incident. No Convective SIGMETs were issued over Illinois. The dispatch did not forecast lightning at the time and location of the strike.
Post-Incident Actions
Subsequent to the incident, Embraer redesigned the tailcone (Tail Boom Fairing) with part number 145-54608-407, incorporating three reinforcement frames internally. The center frame is aluminum without lightening holes, while the other frames are fiberglass with open design. A light assembly is secured by an aluminum retaining strap. Four diverters are installed on the exterior skin, with electrical bonding to the retaining strap and bonding plates. The redesign is detailed in Service Bulletin 145-55-0030, titled "Stabilizers - Improvement in lightning protection of tail boom," released June 30, 2011.