Updated February 6, 2012

The National Business Aviation Association (NBAA) alerted members Monday to a recent Federal Aviation Administration (FAA) opinion on Part 91 crew rest procedures that is in “stark disagreement” with international guidelines, and scientific findings.

In a ruling issued January 20, FAA Associate Chief Counsel of Regulations Rebecca MacPherson stated that under Part 91.105(a), flight crew members are only allowed to leave their stations during takeoff, cruise flight and landing if “the absence is necessary to perform duties in connection with the operation of the aircraft,” or if the absence is “in connection with physiological needs” such as using the lavatory. MacPherson asserted neither condition applies to crew rest, stating “in-flight sleep is not a duty that is necessary to operate the aircraft,” and that physiological needs do “not extend to sleeping during a flight.

“Accordingly, since neither exception to the requirements of § 91.105(a)(l) applies to in-flight sleep, § 91.105(a)(l) prohibits a required flight crew member from taking a ‘controlled rest period’ during an unaugmented flight,” MacPherson concluded. A flight is considered “unaugmented” when there are no relief crew members available to take over flight operations.

Doug Carr, NBAA Vice President, Safety, Security & Regulation, noted that the finding runs contrary to a large body of scientific research on effective fatigue mitigation, that has determined a “controlled cockpit rest” period can raise crew alertness when normal rest periods are compromised. “It is a tactical tool that has been identified as one of the most effective mitigations for fatigue, and recognized in regulatory structures for air carriers throughout the world,” he said. “We are concerned a mitigation tool – one that has been put in place, accepted, and scientifically documented as a significant benefit – has now been ripped out of the hands of Part 91 operators.”

William Voss, president and CEO of Flight Safety Foundation, pointed specifically to studies conducted by the National Aeronautics and Space Administration (NASA) on fatigue mitigation. “Since the mid-1990s, there has been widespread acceptance of controlled cockpit rest,” he said. “This would be going against a vast array of unrefuted scientific research that says it results in a substantial improvement in safety in critical phases of flights. The ruling also leaves the United States in stark disagreement with international standards, and most civil aviation authorities including the International Civil Aviation Organization (ICAO).”

Responding to MacPherson’s ruling, NBAA president and CEO Ed Bolen appealed to FAA Chief Counsel Kathryn Thomson for common sense to prevail. “We believe that this interpretation will have a direct, negative effect on aviation safety,” he wrote in a January 30 letter. “Years of research conducted by NASA and independent sleep experts has shown that, when used as part of a broader safety program, controlled rest effectively reduces the occurrence of ‘micro-sleeps’ that can affect pilots during the most critical phases of flight, approach and landing. Read the NBAA letter to FAA Chief Counsel Kathryn Thomson (PDF).

“We would like the opportunity to discuss this issue with you and your staff as soon as reasonably possible to identify a path forward, balancing the regulation, as written and interpreted, with aviation safety,” Bolen added.

Carr noted the association remains “hopeful” the matter can be resolved within the FAA, but added “in the interim, it is very important that members understand that this document and interpretation exists.”