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Recommendation issued to: United States Federal Aviation Administration

Recommendation details
Output No: R20060017
Date issued: 07 July 2006
Safety action status: Closed - No Action
Background: Why this Recommendation was developed

Output text

Safety Recommendation

The Australian Transport Safety Bureau recommends that the United States Federal Aviation Administration consider revising Title 14 Code of the Federal Regulations, Part 23.1155, to require a positive means to prevent operation of the propeller in the beta mode while in flight (regardless of pilot action), unless the aircraft is certified for such use.

Initial response
Date issued: 10 January 2007
Response from: United States Federal Aviation Administration
Action status: Closed - Not Accepted
Response text:

The FAA has reviewed its current regulations and policies, and decided to not adopt the specific recommendation. A copy of the analysis accomplished by the FAA Small Airplane Directorate is enclosed for your information.

14 CFR, part 23, §23.1155 states:

For turbine engine installations, each control for reverse thrust and for propeller pitch settings below the flight regime must have means to prevent its inadvertent operation. The means must have a positive lock or stop at the flight idle position and must require a separate and distinct operation by the crew to displace the control from the flight regime (forward thrust regime for turbojet powered airplanes).

The National Transportation Safety Board (NTSB) issued a safety recommendation, A-94-62, dated March 2,1994, to revise 14 CFR, part 23, 23.1155 to require beta lock-out systems on small airplanes to prevent operation of the propeller beta mode while in flight. The National Transportation Safety Board cited similar instances on different aircraft over the last 12 years supporting the safety recommendation requiring an in-flight beta lock-out system. The FAA stated its response to the NTSB in a letter dated March 20, 2001:

" ... based on the results of its evaluation, requiring beta lock-out systems for small airplanes would most likely result in an overall decrease in the level of safety for the small airplane fleet. The FAA evaluated accident/incident data over a 20-year span and found only one case where incorporation of a lock-out system would have precluded the incident. However, the FAA found six accidents/incidents caused by the inability to obtain beta when needed. Incorporation of beta lock-out systems would most likely cause this number to increase, effectively lowering the overall level of safety for small airplanes. The service history shows that a more critical consideration for small airplanes is the ability to obtain beta on the ground when required."

The FAA reiterated its March 20, 2001 response to the NTSB in a letter dated October 22, 2001:

"On March 20. 2001, the Federal Aviation Administration (FAA) informed the Board that. based on the results of its evaluation, requiring beta lock-out systems for small airplanes would most likely result in an overall decrease level of safety for the small airplane fleet."

The addition of a beta lock-out system requires increased system complexity:

  • Ground mode sensors: weight on wheels (WOW) switches, wheel spin-up sensors, radar altimeter, etc.
  • Throttle quadrant beta lock-out solenoids.
  • Throttle quadrant balk solenoids.
  • Electronic control containing logic necessary for the interpretation of the ground mode sensors and the subsequent control of the throttle quadrant lock-out and balk solenoids.

Some of the associated failure modes of a beta lock-out system include:

  • Inability to achieve beta during ground operation due to failure of the ground mode sensors, throttle quadrant beta lock-out solenoids or electronic control.
  • Inability to abort a landing once beta has been selected due to a failure of the balk solenoids or electronic control.
  • Ability to select beta mode only on one engine due to a failure of one throttle quadrant beta lock-out solenoid, resulting in a large asymmetric thrust.

The Australian Transportation Safety Board (ATSB) Aviation Occurrence Report - 200404589 Final, cites the in-flight usage of beta in a Fairchild Industries SA227-AC Metro III aircraft as an example supporting the safety recommendation. The FAA issued an Airworthiness Directive (AD 92-18-07) on October 2, 1992 specifically addressing the flight idle detent functionality for the Fairchild Aircraft (formerly Swearingen Aircraft Corporation) SA226-T, SA226- T(B), SA226-AT, SA226-TC, SA227-TT, SA227-AT, SA227-AC and SA227-BC Airplanes.

The specifics of the occurrence cited in the ATSB report clearly point to a situation in which the Airplane Flight Manual (AFM) procedures were not followed. There was a separate and distinct operation by the crew to place the power lever in the beta range, when the AFM specifically states that propeller reversing in flight is prohibited.
Based upon the crew actions cited in the ATSB report, and our position that requiring beta lockout systems for small airplanes would most likely result in an overall decrease in the level of safety for the small airplane fleet, we do not feel that any further action is warranted. Therefore, we propose this recommendation be classified this as "Closed - Not Adopted."

 
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Last update 05 April 2012