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Sept 2003 - Forest Fires

Air Power

New Brunswick’s Forest Protection Limited has recently invested in six new Air Tractor 802 units, the world’s largest single-engine, fixed wing air tanker—complete with a high-tech GPS system—which is offering greater versatility in fighting forest fires and aerial spraying.

By George Fullerton

Gerry Cormier, information services manager with FPL. Top, a new Air Tractor 802 with a TBM Avenger in the background.

What is the optimum service life for forestry equipment and at what point do you make the trade up to new equipment? The service life, of course, depends on the engineering and quality control that went into manufacturing the equipment and the maintenance and operating conditions through its life. In the forest industry, some high tech equipment can have a service life of just a few years before companies want to trade it in for new iron that promises performance and reliability.

Forest Protection Limited (FPL) of Fredericton, New Brunswick had an impressive 30 years of service on their fleet of water bombers—which they purchased used in the early 1970s—before they figured it was time to update their equipment. Their fleet of TBM Avengers was originally designed to fly combat missions from aircraft carriers in World War II. They had power and agility that won them a reputation as heavy haulers and a quick response time that helped New Brunswick develop an enviable fire fighting reputation. However, 30 years of service had thinned out the spare parts availability and service and maintenance schedules had become more and more challenging. Additionally, it was proving difficult to incorporate new technologies into the old aircraft.

The gas turbine engines on the Air Tractor tankers generate 1,350 horsepower. The tanks situated forward of the cockpit, centred between the wings, carry 3,100 litres of fire suppressant or forestry pesticide.

FPL is a not-for-profit company, overseen by a board of directors representing New Brunswick’s forest products companies and the New Brunswick government. The company was established in 1952 with a mandate to protect the forests of New Brunswick. Through the last half-century they have provided fire, pest and vegetation management service, as well as aerial surveys and inspections, mapping and GIS services. FPL initially purchased the fleet of war surplus TBM Avengers and outfitted them for aerial spraying, primarily spruce budworm, as well as doing water-bombing duty for the New Brunswick Department of Natural Resources and Energy.

When the decision is made to change the fleet, you can come ahead some or you can move right to the head of the class. FPL went all the way and purchased a fleet of six Air Tractor 802’s, the world’s largest single-engined fixed wing air tanker. Air Tractors have the typical spray plane configuration, with a lot of fuselage between the cockpit and the propeller. That expanse of fuselage contains a 3,100-litre tank located directly in the middle of the aircraft. The Pratt and Whitney PT6A-67AG gas turbine engine that powers the Air Tractor is, in fact, an extremely compact size for delivering 1,350 horsepower. The airframe on the AT 802 is fabricated with bright yellow, chrome/moly tubing reminiscent of race car chassis construction.

An Air Tractor 802 being loaded with fire suppressant (above). The Air Tractors have done contract work in a number of locations, and were used this past summer in the large-scale firefighting efforts in British Columbia.

The airframe is rugged and heavily triangulated, built to handle heavy loads, rough strips and the severe frame load stressing that is presented in challenging flying conditions. The Air Tractor provides top of the line options like auto pilot, reverse thrust, lightning protection, air conditioning, and a 1,400-litre fuel capacity for long range hauling. It also features dual seating, and one of the FPL 802s has dual controls for pilot training. Eric Bradley, chief pilot with FPL, says that his pilots have adapted quickly to the comfort and power features of the new aircraft. The biggest challenge for the pilots was adapting to the electronic navigation and application features. And although the 802s have great performance and reliability, “they don’t have the grin factor that flying the old war birds have.”

The nature of forest protection has advanced notably over the past 50 years. There is now a greater understanding of fire behaviour with respect to fuel qualities and weather conditions, and how to work with these elements. The pest control side has also seen a higher degree of sophistication, not only for product delivery, but also for things like respecting no-spray riparian zones within spray blocks. FPL ordered their AT 802 units with a slew of options that allows them to take advantage of the most up to date technologies to get the best work results. For example, the DGPS (Digital Global Positioning System) guidance system features a moving map display in the cockpit, and light bar guidance system for precision location and application.

The DGPS software is programmable, and also records multiple parameters to allow post flight analysis and can be integrated with other GPS databases. Flight analysis data includes local time, longitude and latitude, cross track error (relation of aircraft to target swath) track angle, ground heading relative of swath heading, locked line and target swath line. Other available data includes flow rate per minute, boom pressure, average spray speed, average speed of aircraft, rpm of rotational speed of atomizers, time in and out of spray block and time of boom on and off.

Spray booms can be switched on and off manually by the pilot or the DPGS can be programmed to automatically switch the booms on and off when entering or exiting a spray block, even when entering and exiting riparian no-spray zones within a spray block. FPL was the first aerial operator in Canada to integrate GPS-controlled booms into fixed wing aircraft. Bradley says that the integration of the GPS system is extremely important when pilots have to identify the spray blocks on the landscape and riparian zones from the air. “When you are flying over unfamiliar landscape, looking for landmarks to identify spray blocks, it can be difficult to locate them accurately. With GPS technology, the guesswork is out of it. Similarly, at 150 miles per hour at low altitude over forest cover, the accuracy of spray swaths is often questionable.

Again, the GPS systems keep things on track and the product where it needs to be,” explains Bradley. FPL opted to equip their AT 802 tankers with Micronair’s controlled droplet application system. This rotary atomizer uses blade angle adjustment to determine the speed of its rotating wire mesh cage, which breaks the liquid pesticide into smaller droplets. Currently, most of the aerial agricultural spray industry uses hydraulic nozzles, which gives a relatively large particle delivery. Particle size of pesticides is critical for successful control programs because different problem pests require different application density. Typically, flying insects are targeted with a product particle size of 10 to 50 microns, while insects on plant surfaces are at 30 to 150 microns.

Plant diseases require 30 to 150 microns and weeds are 100 to 300 microns. Bradley points out that the new Air Tractor will deliver a bigger load than the TBM, but at a slightly lower top speed, (155 knots versus 165 knots). He adds that because the Air Tractors have a faster pre-flight mechanical check time, and faster warm-up time, they are able to get on fires faster than the TBM’s. Bradley says that options for the delivery of suppressant make the Air Tractor a far more effective fire-fighting tool. Where TBM had the option to dump half or full load, the AT 802 has a computerized delivery system that infinitely controls the rate and amount of suppressant dropped. The delivery system, he says, gives them a wider range of options for attacking fires.

One of the selling points for the AT 802 was the option to dual role the aircraft between pesticide spraying and fire duty. FPL staff felt that it was feasible to have the aircraft on spray work during early mornings—while wind and air turbulence is at its lowest and application conditions are best—and then return to base to remove spray booms and be configured for fire fighting by noon. Bradley said that making the fast switch looked do-able, and during the 2003 season FPL put their theory to the test and got reconfiguration completed, suppressant loaded and on fire standby in less than one hour. Gerry Cormier, FPL’s information services manager, came to the team with a degree in forest engineering and a specialization in information technology.

He has helped their pilots and technical crew to get the most out of the GPS technology built into the tankers, and even develop some tools that others have picked up on. Cormier’s expertise has been put to work integrating the aircraft’s DGPS with a land based GIS database. He is able to program the DGPS to provide a map of the flight line from base to spray block and display the spray swath pattern on the block, even programming boom on-off sequences at the beginning and end of the block and any riparian or other non-spray zones along the spray swath.

Cormier plans spray blocks on a personal computer, downloads the data to a 3.5-inch floppy and then uploads the stored data to the aircraft’s computer system. Once the pilot gets his aircraft in the air, the entire spray plan can be brought up on screen, and the pilot’s primary duty is to fly the airplane by the light bar on the fuselage forward of the cockpit. If all goes technically well, the pilot focuses on flying while the computer takes care of the geography and the application. In case things do not go technically well with the computer system, the pilot can switch to the manual system and deliver the load, either pesticide or fire suppressant, in the pre-computer mode.

Despite the opportunity for technical snags, Cormier says FPL is becoming increasingly comfortable and reliant on GIS and GPS interfacing. The air tractors have given FPL the opportunity to provide services, both spray and forest fire fighting. FPL Air tractors have worked on BC forest fires in 2002 and again in 2003. Chief pilot Eric Bradley says that the planes flew cross-country and were able to work effectively with British Columbia’s fire fighting efforts. FPL has also contracted services in Ontario, Quebec, Nova Scotia and Newfoundland and the northeast US. Meanwhile, FPL has seven operational TBM Avengers for sale, and still gets one out from time to time to thunder across the sky, with the Air Tractors, on exhibition and water bombing demonstrations.

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