‘Hijack’ xponder proposed for all Part 121 operators

Aviation International News » February 2003
January 14, 2008, 7:02 AM

Regional airlines and other Part 121 operators may have to equip their aircraft with a switch within easy reach of the pilot or copilot that immediately activates the transponder hijacking code, if a proposed rule is adopted. Although the proposal would apply initially only to airlines, the FAA is asking industry to comment on its appropriateness to Part 91 and 135 operators.

The FAA said that “during normal operations it is expected that a flight crew could manually dial in a new ATC-directed code, through the transponder control panel, in roughly five to 10 seconds. However, under the stress of a hijacking it may take considerably longer than 10 seconds to dial in the designated hijack alert code, or it may not be possible at all if the crew is distracted by a flight-deck intruder.” In addition, during a hijacking, the current requirements do not prevent an airplane’s transponder from being switched to the “standby” position, or having its circuit breaker pulled, actions that would disable the transponder’s response to an ATC ground-radar beacon interrogation.

Although the agency believes that activation of the code through a “single action” would allow the crew to alert ATC sooner and less obviously to hijackers, the FAA has also determined that there should be a means to protect against unintentional activation of the hijack alert code. Therefore, as an example, a motion that lifts a guarded switch or breaks a frangible wire in the process of activation would still be considered a “single action.”

Specifically, the proposal would require that three conditions be met upon activation of the hijack code: that the altitude-reporting system be maintained; that installation considerations help ensure continuous operation once activated; and that a visual indication be provided to the flight crew. In reference to this last condition, the FAA said a recent incident has shown the agency the importance of visual feedback to the flight crew.

“An airplane with a system similar to that proposed by this rule departed on a flight without realizing that the hijack alert code had been activated. Upon takeoff, ATC immediately detected the hijack alert code and challenged the flight crew. The airplane subsequently returned to its departure airport, escorted by two fighter aircraft. On further investigation, it was determined that the airplane’s hijack alert code had been activated unintentionally by ground personnel.”

The FAA also believes that continuous operation considerations should include inhibiting any further inputs from the ATC transponder control panel–for example, any attempts to change beacon codes or to switch the transponder to standby–as well as for improving the security of electrical power to the transponder equipment. In addition, resetting the transponder to a normal mode of operation should be through a ground action by appropriate personnel.

Further, this rule would require (upon activating the hijack alert code) the removal of power from the electrical breakers for the transponders in the flight deck, and the transfer of power to remotely mounted breakers not accessible from the flight deck or cabin.

Dedicated Hijack Transponder OK

It is expected that most operators will add the capability required by the new rule to function with the existing transponder equipment installed on their airplanes. However, some operators may want to retain their existing equipment configuration, and instead choose to install an additional and dedicated transponder to meet the requirements.

“Because one cannot ensure that a hijacker will, in fact, disable an airplane’s normally operating transponder, it is possible that more than one transponder could be operating and attempting to respond to the ATC secondary surveillance interrogation,” the FAA said. “This could result in an inaccurate reply, and subsequent rejection of both transponders’ Mode 3A/C beacon codes by ATC.” To prevent this, operators who choose to install an additional and dedicated transponder “should provide a means to inhibit replies from all other ATC transponders installed on the airplane [while] this dedicated ATC transponder is activated.”

Given the importance of these proposed requirements, the FAA would prefer to put them into effect as quickly as possible. However, the agency said it’s aware that operators will need approved installation data to accomplish the airplane modifications required by this proposed rule. Therefore, the agency has proposed a compliance date of March 29, 2005. This date was selected because it coincides with the compliance deadline for installation of terrain awareness and warning systems “to minimize the amount of downtime for any given airplane.” This date may slip, however, because it was based on an assumption that a final rule would have been published last December.

Comments on the proposal are due by March 17. For more information, contact Richard Jennings, FAA aircraft certification service in Atlanta, at (770) 703-6090; fax: (770) 703-6055; e-mail: Richard.Jennings@faa.gov.

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