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Regulatory Brief -- FAA opts out of AD, recommends vacuum system checks prior to IFR flightRegulatory Brief -- FAA opts out of AD, recommends vacuum system checks prior to IFR flight

Regulatory Brief

FAA opts out of AD, recommends vacuum system checks prior to IFR flight

The Issue:

A recent highly publicized accident in Missouri involving a Cessna 335 has focused the FAA regulatory spotlight on potential deficiencies in aircraft equipped with dual vacuum systems. The FAA states that there are 1,990 reports of vacuum system component failures on the Service Difficulty Report database. An undetected failure of components of an aircraft vacuum system can result in total or partial loss of attitude and directional indications, and could possibly lead to spatial disorientation when operating in Instrument Meteorological Conditions (IMC).

The Importance to our Members:

In an effort to preclude the possibility of an undetected vacuum system failure, the FAA published an Airworthiness Concern Sheet (ACS) applicable to "All twin reciprocating engine small airplanes certificated under CAR3 or 14 CFR Part 23 that have gyroscopic instruments which are powered by single or dual vacuum sources." The ACS indicated the FAA was considering an Airworthiness Directive mandating repetitive vacuum system check valve inspections and replacements and solicited input from AOPA, aircraft type-clubs, and other organizations. In response to the ACS, AOPA and aircraft type-clubs opposed an AD mandating repetitive inspections and parts replacements, pointing out that a simple preflight check at engine start-up could completely preclude the possibility of an undetected vacuum system failure. The FAA, in reaction to the recommendations of AOPA and others, opted out of an AD, and instead issued an SAIB recommending a simple preflight verification of the vacuum system's integrity.

Significant Provisions:

  • In response to recent accidents and incidents involving vacuum system failures in aircraft operating in instrument meteorological conditions (IMC), the FAA recently published a Special Airworthiness Information Bulletin (SAIB) recommending a preflight check for proper operation of aircraft vacuum systems.
  • The SAIB is applicable to aircraft equipped with gyroscopic instruments powered by dual vacuum or pressure sources utilizing Airborne Check Valve Manifold or Check Valve Part Numbers 1H5, 1H24, or 1H37.
  • Parker Hannifin Product Reference Memo No. 39 denotes a potential latent failure of the check valves which could lead to a dual vacuum or pressure system failure.
  • SAIB No. CE-01-29 states "The FAA highly recommends that owners and operators of airplanes with dual air sources that power attitude or directional gauges, require the pilot to conduct a preflight check to verify proper operation of the vacuum system."
  • The SAIB contains instructions for conducting the recommended vacuum system check in both single and multi-engine airplanes.

AOPA Position:

AOPA thanks the FAA for affording the General Aviation community an opportunity to participate in their effort to mitigate this airworthiness concern. AOPA believes that the FAA has taken the best possible action by avoiding unnecessary mandatory maintenance actions through the issuance of an SAIB. The quality of industry comments in response to this ACS is an example of how the practical knowledge and expertise of owner's organizations and aircraft type-clubs can result in practical and affordable alternatives to draconian AD actions. AOPA looks forward to continued successes using the airworthiness concern process.


  • On June 21, 2001, FAA published SAIB No. CE-01-29.
  • On February 5, 2001, AOPA responded to the ACS in opposition to an AD.
  • On November 6, 2000, FAA issued an ACS recommending AD action.
  • On January 31, 1996, Parker Hannifin published Product Reference Memo No. 39.

Related Documents:

SAIB No. CE-01-29, June 21, 2001 (requires Adobe Reader)

AOPA Comments to ACS, February 5, 2001 (requires Adobe Reader)

FAA ACS, November 6, 2000 (requires Adobe Reader)

Parker Hannifin Product Reference Memo No. 39 (requires Adobe Reader)