News Archive
AOPA petitions FAA to rescind Precise Flight standby vacuum system AD, says AD may cause new safety problems
An airworthiness directive on the Precise Flight SVS III Standby Vacuum system may cause more safety problems than it solves, according to the Aircraft Owners and Pilots Association. AOPA has petitioned the FAA to rescind AD 99-24-10.
“The AD requires a biannual ‘test’ that could cost more than the price of a new unit,” said Dennis Roberts, AOPA vice president and executive director of government and technical affairs. “Many pilots will view the cost of compliance to be greater than the benefit of a simple standby vacuum system, and they’ll remove the system from their aircraft. That could have an unfortunate safety impact.”
The AD calls for an annual inspection to ensure the system is working properly and can be relied upon in an emergency. It also requires an annual flight check, confirming that the system still functions at six different altitudes.
(The Precise Flight system uses engine manifold vacuum to power an aircraft’s attitude indicator and directional gyro in the event of a vacuum pump failure. It’s an emergency system because only partial power settings, not full throttle, will generate enough vacuum. During initial installation, the aircraft is flown to develop a chart of reduced power settings adequate to power the gyro instruments.)
The FAA estimates the annual inspection will require some three hours. The flight check may require up to six hours (two hours to prepare the aircraft by disconnecting the vacuum pump and installing temporary filters to protect the vacuum system, two hours for the actual flight check, and another two hours to return the aircraft to service).
An inspection and flight check could cost as much as $540 for a system with a retail list price of $429.
“But the flight check is not to identify an airworthiness problem, it’s to train the pilot,” said Roberts. “That’s an inappropriate use of an airworthiness directive.”
A Precise Flight engineer, in an e-mail to an aircraft owners group, acknowledged that the biannual flight check is for recurrent pilot training, “not for the operational life of the standby components.... Pilots are purchasing used aircraft with the standby systems installed and are not trained in how to operate the aircraft with a primary vacuum failure.”
According to this engineer, the impetus for the AD was a report of a pilot who departed VFR, had a primary vacuum failure, but continued his climb into IFR conditions using the Precise Flight Standby System.
“That’s an operational issue, not an airworthiness concern,” said AOPA’s Roberts. “Operating procedures should be addressed in the aircraft flight manual or pilot’s operating handbook and by educational materials for the pilot community.”
Roberts also noted that the AD doesn’t, in fact, mandate pilot training because it does not require the pilot or aircraft owner to participate in the flight check.
“AOPA and the AOPA Air Safety Foundation encourage pilots to install standby vacuum systems in aircraft that are regularly flown in instrument meteorological conditions,” Roberts concluded. “Unfortunately, this AD will likely discourage the use of a simple, cost-effective standby vacuum source.”
AOPA asked the FAA to rescind final rule AD 99-24-10 and reissue a proposed AD for public comment. A copy of AOPA’s petition is available on AOPA Online.
AOPA’s review of airworthiness directives is part of the association’s mission to make general aviation flying safer, more affordable, and more fun.
The Aircraft Owners and Pilots Association, based outside Washington, D.C., represents more than 355,000 pilots who own or fly three quarters of the nation’s 192,000 general aviation aircraft.
99-4-071
December 22, 1999
