Federal Aviation Administration April 14, 2005 – Federal Register Recent Federal Regulation Documents

Pursuant to FAA's rulemaking provisions governing the application, processing, and disposition of petitions for exemption, part 11 of Title 14, Code of Federal Regulations (14 CFR), this notice contains a summary of a certain petition seeking relief from specified requirements of 14 CFR. The purpose of this notice is to improve the public's awareness of, and participation in, this aspect of FAA's regulatory activities. Neither publication of this notice nor the inclusion or omission of information in the summary is intended to affect the legal status of any petition or its final disposition.

The FAA proposes to adopt a new airworthiness directive (AD) for certain Learjet Model 23, 24, 24A, 24B, 24B-A, 24D, 24D-A, 24E, 24F, 25, 25A, 25B, 25C, 25D, and 25F airplanes. This proposed AD would require removing the thrust reverser accumulator, and making the thrust reverser hydraulic system and the thrust reversers inoperable. This proposed AD is prompted by reports of the failure of two thrust reverser accumulators. We are proposing this AD to prevent failure of the thrust reverser accumulators, due to fatigue cracking on the female threads, which could result in the loss of hydraulic power and damage to the surrounding airplane structure.

The FAA is adopting a new airworthiness directive (AD) for certain Cessna Model 680 airplanes. This AD requires revising the airplane flight manual (AFM) to add procedures to facilitate recovery of the cockpit display units in the event that the cockpit display units go blank, and to add flight crew briefings on the use of standby instruments in case the cockpit display units go blank and do not recover. This AD also requires repetitive tests of the avionics standard communication bus (ASCB) for any failures, and corrective action if any failure is found. This AD also requires installing hardware and avionics software upgrades; installing the upgrades will allow removal of AFM revisions and will end the repetitive inspections of the ASCB. This AD is prompted by a report indicating that analysis of the Honeywell Primus Epic systems installed on Cessna Model 680 airplanes revealed that all four of the cockpit display units could go blank simultaneously. We are issuing this AD to prevent a simultaneous loss of data from all four cockpit display units, and loss of primary navigation instruments, autopilot, flight director, master caution/ warning lights, aural warnings, global positioning system position information, and air data and altitude information to non-avionics systems. These losses could reduce the flightcrew's situational awareness, increase flightcrew workload, and consequently reduce the ability to maintain safe flight of the airplane.