The original Air Tractor FRDS represented a leap forward in fire gate control technology for aerial firefighting applications. With its computerized fire gate technology, air tanker pilots could simply and quickly dial-in coverage level and drop amount. Calculations were then handled by the system’s on-board computer, making it possible for the pilot to deliver a consistent and controlled amount of fire retardant to the specified drop zone.

Since its introduction, the Air Tractor FRDS fire gate has earned a reputation in wildland firefighting circles for uniform coverage and system reliability. But in the past 16 years computer technology has made exponential advances, so the Generation II FRDS fire gate has been updated to allow pilots and operators to take full advantage of those advances.

Says Leland Snow, President of Air Tractor, Inc., “The Air Tractor FRDS has been the most precise and accurate fire gate for single engine air tankers since its introduction with the AT-802F in 1993. Now it’s been improved with the latest computer technology and self-diagnostics. It’s the next logical step in the evolution of this computerized fire gate.”

Improved delivery accuracy, improved door speed and new advanced leakage compensation algorithms are among the second generation FRDS enhancements. The fire gate doors — which open and close with timing that’s measured in milliseconds — are even more responsive.

Numerous reliability enhancements have been designed-in throughout the new Air Tractor FRDS system. The components of the system have been “hardened” to protect against the effects of vibration and humidity; the system also has improved waterproofing throughout. Microprocessor and electro-mechanical back-up systems have been added. A three valve redundant auto salvo system assures reliable door opening for accurate drops.

Computer processing advances make the FRDS pilot interface more user friendly. An easy-to-read display allows pilots to assess system status at a glance.

Field service and maintenance has been simplified with a “black box” or cable swap-out program and self-diagnostic and alert message features that indicate possible malfunctions and help isolate problems in the system.

The hydraulic system of the FRDS also reflects numerous reliability improvements. The new dual-head hydraulic pump is 93% efficient, and powered by a heavy-duty DC motor. An inlet filter helps prevent contaminants from entering the hydraulic system and extends component life. The entire hydraulic system has been tested in a controlled environment of over 160° (F) for more than 6,000 flight hours.

The previous FRDS system’s servo valve has been replaced with three identical directional valves, providing three levels of redundancy when opening and closing fire gate doors. An independent pressure switch (electro-mechanical system) and pressure sensor control the hydraulic pump.

In total, all these improvements work together to make the Generation II FRDS easier for operators to use and even more reliable and simple to maintain. The minimal initial training that is required for system maintenance further improves the operational economics of the new system.

Since its introduction, ease of use and ease of maintenance have been the hallmark of the Air Tractor FRDS-equipped AT-802A and 802AF. In 3 to 5 seconds the pilot can dial-in the coverage level, the drop amount, the ground speed and arm the system. With a press of the trigger on the control stick, the computer opens and closes the fire gate doors according to the selected parameters. For pilots, operators and fire management personnel on the ground, it’s a “point and shoot” system that proves its worth with every fire drop.

The first AT-802F aircraft equipped with the Generation II FRDS will be shipped to Avialsa, based near Valencia, Spain to join their fleet of 22 other AT-802F and AT-802AF single engine air tankers.

The initial plan was to break into multiple teams and perform key upgrades to the system before the Spain fire season started. In the course of doing these upgrades a number of maintenance issues were found and a 2nd round of maintenance was deemed necessary.

Unfortunately, by this time fire season had started and the crews in Spain were forced to work during off hours (at night) under a strict mandate that the planes must be ready to fly by the next day. This meant a rather odd schedule for the Trotter Controls crew and many a sunrise. By the end of summer Trotter Controls had met or exceeded all goals for the trip, performing much needed maintenance and system upgrades to the Spanish fleet of over 40 aircraft.