Aviation Accident Summaries

Aviation Accident Summary OPS12IA303

Farmersville, TX, USA

Aircraft #1

N639AE

EMBRAER EMB-145LR

Analysis

A regional jet departed from Dallas-Fort Worth International Airport on a scheduled passenger flight to Madison, Wisconsin. About 15 minutes after takeoff, the crew declared an emergency because the airplane had been struck by lightning and requested to divert to Little Rock, Arkansas. After landing, the airplane was inspected and found to have sustained damage from the lightning strike requiring repairs to the left wing skin and rivets and replacement of the left wingtip and aileron. At the time of the incident, the airplane was being handled by controllers at the Fort Worth Air Traffic Control Center. Significant convective weather was in the area and along the airplane's route, resulting in closures of several routes into and out of the Dallas area. The controllers did not provide specific information on the location of the convective activity along the airplane's route until the crew asked for the information. However, in response to a question, the controllers did advise the crew that there was moderate to heavy precipitation ahead. The crew attempted to identify areas where they could divert to avoid the convective activity, but the controller was unable to approve significant deviations because of other traffic flows in the vicinity. Shortly afterward, the lightning strike occurred. Because of the lightning strike and requests for weather deviations by other aircraft flying through the same area, the center's Traffic Management Unit began rerouting aircraft away from the area and toward other routes less affected by convective weather. When interviewed, traffic management staff noted that this pattern was normal: it was not unusual to wait until pilots refused to fly a route because of weather impact before discontinuing its use. This incident was included as an example in a recommendation letter to the FAA, available at http://www.ntsb.gov/doclib/recletters/2012/A-12-018-020.pdf, which recommends improved transmission of real-time lightning data to both controllers and pilots.

Factual Information

On January 24, 2012, at about 1927 Central standard time, American Eagle flight EGF3376 (EGF3376), an Embraer E145LR regional jet, was struck by lightning shortly after departure from Dallas-Fort Worth International Airport. Review of National Weather Service radar data for the area showed the presence of moderate to extreme intensity precipitation along the aircraft's route of flight. Archived lightning data obtained by Safety Board meteorologists after the accident showed that EGF3376 passed through an area of recorded scattered lightning and close to an area of concentrated lightning activity coincident with extreme precipitation just before the crew reported the strike. At the time of the incident, EGF3376 was operating on an instrument flight rules (IFR) flight plan and receiving air traffic control (ATC) services from Fort Worth Air Route Traffic Control Center (ZFW). EGF3376 was a scheduled passenger flight under operating under 14 Code of Federal Regulations part 121 between DFW and Madison, Wisconsin (MSN). Following the lightning strike, the crew declared an emergency and diverted to Little Rock, Arkansas. After landing at Little Rock, the aircraft was inspected and damage was found that required replacement of the left wingtip and left aileron, as well as additional repairs to skin and rivets on the left wing. There were no injuries reported to the 50 passengers and 3 crewmembers. EGF3376 departed DFW airport at 1912 and was given radar vectors toward the "east gate" used for departures from Fort Worth Terminal Radar Approach Control's (D10) airspace. Because of severe weather affecting the entire area, D10's arrival and departure routes to the north and south were closed, and aircraft wishing to proceed toward the northeast were being sent through the east gate via the DFW VORTAC 064 radial or south of that radial. Airspace to the north of the east gate was occupied by arriving traffic. Before being transferred to ZFW, EGF3376 was instructed to proceed direct to NOBLY waypoint, which is on the Maverick (TTT) VORTAC 064 radial. The aircraft first called ZFW sector 83 at 1923, climbing through 12,000 feet for 17,000 feet. The R83 controller recleared the pilot to climb and maintain FL190. About 20 seconds later, the pilot requested a 20 degree left deviation for weather. The R83 controller asked to confirm the request, and the pilot responded, "That's going to take us further away from the weather." The controller approved a ten degree deviation. At 0124, the controller contacted the D10 departure controller, advising, "We're losing the 064 radial – we're going to be shutting off the east gate because they can't stay south of the 064 radial." At 1924:51, EGF3376 asked, "What's the weather look like ahead of us?" The controller replied that there were, "…moderate and heavy precipitation returns until at least north of Texarkana." The pilot then asked, "what about turning left back direct to Dallas?" The controller responded, "okay EGF3376 understand you want to return back to Dallas?" The pilot responded, "yeah… That would get us out of the weather quicker for 3376?" The controller then asked, "EGF3376 understand that you're requesting a clearance back to Dallas-Fort Worth. Is that correct?" At 1925:25, the pilot asked, "how's the weather look that direction for 3376?" The controller replied, "well behind you, I've got moderate precipitation as well and to the south of you." The pilot of EGF3376 then asked, "what about to the north… We are (unintelligible) here." The controller then advised the pilot, "… You cannot go to the north and that's the arrivals in over Bonham (BYP) and they got a bunch of airplanes. I can't let you go that far north." At 1927:38, EGF3376 called the center controller. The controller acknowledged the call, and EGF3376 continued, "yeah were going to go ahead and declare an emergency. We've been hit by lightning and we'd like to divert to Little Rock." The controller immediately cleared EGF3376 direct to the Little Rock airport at flight level 180. He then asked if there was any additional assistance required and the pilot responded "not now." The aircraft was subsequently handled by ZFW sectors 37 and 27 before being handed off to Memphis Center and eventually Little Rock approach, where the aircraft landed without further incident. According to information provided by American Eagle, a post-flight maintenance inspection revealed lightning damage to various components of the left wing. For further information, see the ATC Group Chairman's Factual Report in the docket for this case.

Probable Cause and Findings

The flight's continued operation through an area containing substantial convective weather activity. Contributing to the accident was the air traffic control/traffic management unit's lack of awareness and recognition of the effect of weather movement on the departure route in use and the flight crew's acceptance of a route and limited weather deviation that was inadequate to maintain a safe distance from the thunderstorms in the area.

 

Source: NTSB Aviation Accident Database

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