Action
Supplemental notice of proposed rulemaking (SNPRM); reopening of comment period.
Summary
We are revising an earlier proposed airworthiness directive (AD) for The Boeing Company Model 777-200 and -300 series airplanes, equipped with Rolls-Royce Model RB211-Trent 800 engines. The notice of proposed rulemaking (NPRM) proposed to require repetitive inspections of the thrust reverser (T/R) structure and sealant, and related investigative and corrective actions if necessary. The NPRM was prompted by reports of T/R events related to thermal damage of the T/R inner wall. This action revises the NPRM by proposing to add different repetitive inspections requirements for T/R halves with a thermal protective system installed. This action also revises the NPRM by proposing to require installation of serviceable T/R halves, which would terminate the repetitive inspections in this SNPRM. This SNPRM also proposes to revise the inspection or maintenance program by incorporating new airworthiness limitations. We are proposing this SNPRM to detect and correct a degraded T/R inner wall panel, which could lead to failure of the T/R and adjacent components and their consequent separation from the airplane, and which could result in a rejected takeoff (RTO) and cause asymmetric thrust and consequent loss of control of the airplane during reverse thrust operation. If a T/R inner wall overheats, separated components could cause structural damage to the airplane, damage to other airplanes, or possible injury to people on the ground. Since these actions impose an additional burden over that proposed in the NPRM, we are reopening the comment period to allow the public the chance to comment on these proposed changes.