Embraer EMB-145LR N639AE incident near Farmersville, Texas

Probable cause

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.

NTSB 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.

Text from the NTSB. Open the NTSB docket for OPS12IA303 for the full record.