Airworthiness Directive AD 76-07-12 requires a functional check of certain Bendix rotary-action ignition switches at intervals not exceeding 100 hours of time-in-service, and the check must confirm that the switch actually grounds the magnetos when the key is turned to “OFF.” The directive has been in effect since August 1977, applies to any aircraft fitted with the covered switches regardless of airframe manufacturer, and is repetitive for as long as the switch remains installed. Operating an aircraft that is out of compliance is a violation of 14 CFR 39.7 and renders the aircraft unairworthy.1eCFR. 14 CFR 39.7 – What Is the Legal Effect of Failing To Comply With an Airworthiness Directive
Which Switches Are Covered
The AD does not target a specific airplane. It reaches any aircraft equipped with magnetos and fitted with certain Bendix rotary-action ignition switches, identified by part number series including the 10-357XXX, 10-126XXX, and 10-157XXX series, in both “Twist-to-Start” and “Push-to-Start” configurations. Because these switches were widely used across general aviation, the directive touches a broad range of single-engine and light twin aircraft.
Two markings take a switch out of the directive. If the switch carries a four-digit date code, or a white dot on the support plate near the Bendix logo, it has already been modified or is a newer design that eliminates the failure mode. Aircraft with those marked switches do not need to comply. If you are unsure whether your switch falls under the AD, compare the installed part number against the series above and check the maintenance records for any prior AD compliance or switch replacement.
The Unsafe Condition Behind the Check
A magneto generates its own current to fire the spark plugs. Turning the ignition switch to “OFF” is supposed to ground the magneto’s primary circuit so it cannot produce a spark. The Bendix switches covered by this AD can fail to ground the magneto even when the key reaches the “OFF” position. The engine remains capable of firing, and if anyone moves the propeller by hand during preflight or maintenance, it can start without warning. The NTSB has documented cases where loss of ignition switch integrity led to unintended engine startups with serious injuries and fatalities.2National Transportation Safety Board. NTSB Safety Alert 080 – Check Ignition Switch/Key Integrity
How To Perform the 100-Hour Functional Check
The check happens on the ground, after the engine has been run through normal ground run-up procedures and reached operating temperature. With the engine at idle, rotate the ignition key or lever through the “OFF” detent to the full limit of travel in the “OFF” direction. The engine should stop firing immediately. If it does, the switch is working and the aircraft passes.
If the engine keeps running after the key reaches its full “OFF” travel, the switch has failed. The aircraft is unairworthy until the switch is repaired or replaced.
An unusual feature of this AD is that the pilot may perform the functional check. Most airworthiness directives require a certified mechanic, but this test is straightforward enough that the FAA allows pilot compliance under the existing authority for owner-operators to perform preventive maintenance.3eCFR. 14 CFR 43.3 – Persons Authorized To Perform Maintenance, Preventive Maintenance, Rebuilding, and Alterations The corrective action after a failed check is a different matter.
If the Switch Fails
Do not fly the aircraft. Corrective action follows the procedures in Bendix Service Bulletin No. 583, originally dated April 1976 and now superseded by Service Bulletin No. 583A, issued July 21, 2008, which is the current reference document for inspection, repair, and replacement.4Lycoming. Service Bulletin No. 583 A The repair or replacement itself must be performed by a certified mechanic or repair station, not by the pilot.
If the aircraft sits at a location without maintenance capability, a special flight permit under 14 CFR 21.197 may allow you to fly it to a facility where the work can be done. The FAA issues these permits for aircraft that do not currently meet airworthiness requirements but are still capable of safe flight, specifically for the purpose of reaching a maintenance base.5eCFR. 14 CFR 21.197 – Special Flight Permits The application goes to your local Flight Standards District Office. Moving the aircraft without the permit is itself a violation.
The Repetitive 100-Hour Interval
The original compliance deadline required the first functional check within 100 hours of time-in-service after the AD’s effective date in August 1977.2National Transportation Safety Board. NTSB Safety Alert 080 – Check Ignition Switch/Key Integrity That initial window closed long ago, but the AD is repetitive. Every aircraft with an affected Bendix switch must have the check accomplished at intervals not exceeding 100 hours of time-in-service, indefinitely, for as long as the switch remains installed.
For aircraft that fly around 100 hours per year, that works out to roughly an annual check. Higher-utilization aircraft need it more often. Owners frequently align the AD check with the 100-hour inspection required for aircraft used in commercial operations or flight training, but the AD’s clock runs independently. Letting it lapse even by a few hours makes the aircraft technically unairworthy.
Recording the Check in the Logbook
Every compliance action goes in the aircraft’s maintenance records. Under 14 CFR 43.11, an inspection entry must include the type of inspection performed with a brief description, the date, and the aircraft’s total time-in-service.6eCFR. 14 CFR 43.11 – Content, Form, and Disposition of Records for Inspections Conducted Under Parts 91 and 125 A typical entry for this AD notes that the AD 76-07-12 functional check was performed, whether the switch passed, the date, and airframe total time at the time of the check. If a pilot performs the check, the pilot signs the entry. If a mechanic performs it as part of a broader inspection, the mechanic signs.
The NTSB has flagged accidents in which maintenance records showed no evidence of AD 76-07-12 compliance.2National Transportation Safety Board. NTSB Safety Alert 080 – Check Ignition Switch/Key Integrity Missing or incomplete records also surface as problems during aircraft sales and annual inspections.
What Noncompliance Costs
Anyone who operates a product that does not meet the requirements of an applicable AD is in violation of 14 CFR 39.7.1eCFR. 14 CFR 39.7 – What Is the Legal Effect of Failing To Comply With an Airworthiness Directive The aircraft owner or operator bears primary responsibility for keeping the aircraft in compliance with all ADs under 14 CFR 91.403.7eCFR. 14 CFR 91.403 – General
The FAA’s enforcement toolkit for AD violations includes both certificate actions and civil penalties. Certificate actions range from fixed-duration suspensions, to indefinite suspensions that keep a pilot grounded until they demonstrate they meet certification standards, to full revocation for serious or repeated offenses.8Federal Aviation Administration. Legal Enforcement Actions Civil penalties can reach up to $17,062 per violation for individuals who are not serving as airmen, with a cap of $100,000 per enforcement action.9Federal Register. Civil Monetary Penalty Adjustments for Inflation Suspensions and revocations can be appealed through the NTSB and, ultimately, a U.S. court of appeals.