Regulatory and Certification Policy
FAA approves alternate compliance method for Precise Flight standby vacuum system AD
On November 30, 1999, the FAA published final rule airworthiness directive (AD) 99-24-10, mandating repetitive inspections and repetitive flight testing of Precise Flight Model SVS III Standby Vacuum Systems. Citing the high cost of AD compliance AOPA petitioned the FAA to rescind the AD and reopen the public comment period. On December 20, 1999, AOPA petitioned the FAA to rescind AD 99-24-10 and reissue the proposed AD for public comment. On January 19, 2000, the FAA approved an alternate compliance method developed by Precise Flight.
The importance to our members:
This AD affects approximately 10,000 U.S. registered aircraft currently equipped with Precise Flight Model SVS III standby vacuum systems. Affected aircraft owners were alarmed by the repetitive cost of AD compliance, which, in some cases, may be higher than the cost of a brand new SVS III system. Most owners indicate that such high compliance costs may force them to remove these systems from their aircraft.
- The FAA cited 14 incidents of failed control valves and 2 accidents where improper use of standby vacuum systems were factors.
- The AD is applicable to all aircraft equipped with a Precise Flight Model SVS III standby vacuum system installed either through an STC or field approval.
- The AD requires repetitive inspection of the push-pull cable, vacuum lines, saddle fittings, and shuttle valve for correct installation, damage and wear. Additionally, the AD requires extensive repetitive flight tests in accordance with Precise Flight Instructions for Continued Airworthiness.
- According to officials from Precise Flight, the repetitive flight testing requirements were included to ensure that pilots received adequate training in the operation of their systems.
- Historically, AOPA and the AOPA Air Safety Foundation have advocated the use of standby vacuum systems as an operational adjunct for any pilot operating in instrument meteorological conditions (IMC). In the event of a vacuum related gyro failure in IMC, standby vacuum systems can reduce pilot workload and decrease the likelihood of spatial disorientation, thus enhancing aviation safety.
- The Alternative Method of Compliance (AMOC) eliminates the flight-testing requirement by providing a provision to upgrade to a SVS Model V system.
- Owners of SVS III systems with shuttle valve serial # 10243 and higher may upgrade by simply obtaining an updated copy of the Airplane Flight Manual Supplement (AFMS). Owners of pre-1991 shuttle valves (#10242 and lower) must replace the shuttle valve at a cost of $77 plus undetermined labor costs and obtain an updated AFMS.
- Owners with working (airworthy) shuttle values (serial #10242 and lower) who elect to forego replacement must still comply with the twice-a-year flight-testing compliance procedure.
AOPA agrees that, in this particular situation, inspection of cables, lines, fittings, and valves of Precise Flight Model SVS III systems is an appropriate way to ensure proper continued operation of these systems. However, AOPA fails to see the merit in repeating a testing procedure designed to test the standby vacuum system�s operating parameters directly following its installation. AOPA maintains that the repetitive flight testing requirements of this AD are designed to address purely operational concerns. Operational concerns, such as this one, could be more effectively addressed in other non-regulatory arenas. Further, AOPA fears that the high cost of AD compliance may prompt most affected aircraft owners to remove these systems from their aircraft. To address these concerns, AOPA has requested that the FAA rescind AD 99-24-10 and reissue the proposed AD for public comment.
AOPA is pleased with the AMOC for Models III with shuttle valve serial numbers 10243 and higher. However, since the AMOC requires owners of certain systems to replace working shuttle valves, AOPA feels that the AMOC not sufficient. Therefore, AOPA will not withdraw its petition to rescind the AD.
Contrary to some reports, AOPA was not involved in the development of the alternate compliance procedure. In the future, AOPA urges Precise Flight and the FAA to include aircraft owners/operators in the development of alternative methods of AD compliance.
- On November 30, 1999, the FAA published, as final rule, AD 99-24-10.
- On December 20, 1999, AOPA petitioned the FAA to rescind AD 99-24-10 and reissue the proposed AD for public comment.
- On January 19, 2000, the FAA approves an alternative compliance procedure submitted by Precise Flight, Inc. that eliminates the in-flight testing procedure for 1991 and later models.
- As of January 19, 2000, AOPA is still awaiting a FAA response to our petition to rescind AD 99-24-10.
AOPA rulemaking petition, December 20, 1999