Summary
We propose to adopt a new airworthiness directive (AD) for certain The Boeing Company Model 747-400 and 747-400F series airplanes. This proposed AD was prompted by reports of cracking in the main equipment center (MEC) drip shield and exhaust plenum. This proposed AD would require installing a fiberglass reinforcing overcoat on the MEC drip shield. We are proposing this AD to prevent water penetration into the MEC, which could result in an electrical short and potential loss of several functions essential for safe flight.