Move Follows Findings In South Carolina Lear Accident

The NTSB has made a series of recommendations to the FAA following its findings in an accident in South Carolina in which tires were deemed to be a contributing factor.

The board recommends that the FAA provide pilots and maintenance personnel with information that:

• Transport-category aircraft tires can lose up to 5 percent pressure per day.
• It may take only a few days for such tires to reach an underinflation level below what the aircraft maintenance manual specifies for tire replacement.
• The underinflation level that would require tire replacement is not visually detectable.

In addition, the board says the FAA should require that all 14 Code of Federal Regulations Part 121, 135, and 91 subpart K operators perform tire pressure checks at a frequency that will ensure that the tires remain inflated to within aircraft maintenance manual-specified inflation pressures, require that aircraft maintenance manuals specify, in a readily identifiable and standardized location, required maintenance intervals for tire pressure checks (as applicable to each aircraft), and allow pilots to perform tire pressure checks on aircraft, regardless of whether the aircraft is operating under 14 Code of Federal Regulations Part 91, Part 91 subpart K, or Part 135.

It is also calling for tire pressure monitoring systems for all transport- category airplanes.

As relates to the specific accident, the NTSB has recommended that the FAA identify deficiencies in Learjet's system safety analyses, both for the original Learjet 60 design and for the modifications after the 2001 accident, that failed to properly address the thrust reverser system design flaws related to this accident, and require Learjet to perform a system safety assessment in accordance with 14 Code of Federal Regulations 25.1309 for all other systems that also rely on air-ground signal integrity and ensure that hazards resulting from a loss of signal integrity are appropriately mitigated to fully comply with this regulation.

It further recommends that the Agency revise available safety assessment guidance (such as Advisory Circular 25.1309-1A) for manufacturers to adequately address the deficiencies identified in Safety Recommendation A-10-51, require that designated engineering representatives and their FAA mentors are trained on this methodology, and modify FAA design oversight procedures to ensure that manufacturers are performing system safety analyses for all new or modified designs that effectively identify and properly mitigate hazards for all phases of flight, including foreseeable events during those phases (such as a rejected takeoff). The board says that tire testing criteria should reflect the actual static and dynamic loads that may be imposed on tires both during normal operating conditions and after the loss of one tire and consider less-than-optimal allowable tire conditions, including, but not limited to, the full range of allowable operating pressures and acceptable tread wear.

And finally the NTSB says the FAA should require that pilots who fly in 14 Code of Federal Regulations (CFR) Part 135 operations in an aircraft that requires a type rating gain a minimum level of flight time in that aircraft type, similar to that described in 14 CFR 121.434, taking into consideration the unique characteristics of Part 135 operations, to obtain consolidation of knowledge and skills.

FMI: www.ntsb.gov