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2009 Articles

JUL 30 2009
Marsh Aviation's TurboTracker

As part of its response plan to wildfires, the CDF operates a network of air attack bases, equipped with a team of aircraft and ground personnel, who work in unison to battle these fires as soon as they are detected. The aerial component consists of fixed wing tanker aircraft, helicopters and also observation aircraft equipped for command and control of the assets deployed. Currently the air tanker portion of this team is the Marsh Aviation S-2 TurboTracker, an updated and modernised variant of the Grumman S-2 Tracker, produced at Marsh Aviationís facility in Mesa, Arizona.

The Grumman S-2 Tracker first flew in 1952, and entered service with the US Navy in 1954. It was the first purpose built, single airframe anti-submarine warfare (ASW) aircraft, and was designed to operate from aircraft carriers. This requirement meant that the airframe needed to be very rugged, and as a consequence the airframe has a long design life. Despite being retired from US Navy service in 1976, many of the ex-US Navy airframes still had an appreciable number of hours left at time of retirement, meaning they had the potential to see further service.

With large numbers of aircraft becoming available in the 1970s, Aero Union converted some S-2s into tankers for the State of California, with the first aircraft being delivered in 1973. These aircraft retained the original S-2ís Wright R-1820 radial engines, and were useful fire fighting aircraft, but it was not until the 1980s that the full potential of the airframe was realised, with Marsh Aviationís modernisation program.

Realising the market for an improved, higher performance tanker aircraft, Marsh Aviation developed the first turboprop powered S-2 in the 1980s, with the aircraft flying for the first time in 1986. Tanker 180, as it was known, was evaluated by the CDF for six seasons, and even made the journey across the Atlantic to appear at the Paris Airshow in 1989. Impressed by the performance of the TurboTracker, the CDF ordered a fleet of 22 aircraft, with the first being delivered in 1998.

Marsh Aviation replaced the original radial, piston engines with modern Honeywell TPE331-14GR turboprops, driving five-bladed Hartzell propellers. The nacelles and other areas of the airframe were modified to be more aerodynamically efficient, and the aircraft received new fuel, lubrication and fire-extinguishing systems. The airframe and hydraulic system was completely overhauled and the cockpit modernised, with new instruments and navigation systems.

All of the military equipment was removed to make way for fire-fighting equipment - the fuselage and torpedo bay were modified to make room for a retardant tank system, which is filled from the tail, where the MAD boom was located on the original S-2. The location of the filling point means that the TurboTracker can re-load on the ground with the engines running, a procedure which takes roughly three minutes, leading to hugely decreased turnaround times.

The benefits of the modernisation program are obvious - retardant capacity increased from 800 gallons in the piston-engined S-2 to 1200 gallons (or 1100 gallons in some versions), cruise speed increased from 150 mph to 280 mph, and general performance, especially in hot weather, improved. The TurboTracker also has an increased endurance of up to five hours - most flights only last 30 mins, so this improved endurance, coupled with the rapid re-loading, means that the aircraft can operate many trips to a fire before needing to be refuelled.

In addition to these benefits, the TurboTracker is also much more reliable and economical than earlier S-2s, boasting the highest dispatch reliability in the air tanker industry. It is also capable of operating from smaller airfields than larger air tankers, and is rated to be flown by a single pilot, offering further cost savings.

The retardant tank fitted to the TurboTracker is an advanced, computer controlled system, capable of dropping specific quantities of retardant at different rates and coverage levels. This enables a flexible response, appropriate to the conditions at the fire site, meaning that it is much more effective in controlling and containing fires than older tankers, which lack the more up to date technology.

In addition to the aircraft delivered to the CDF, Marsh Aviation has also been involved in S-2 conversions for the Argentine Navy (Armada Argentina) and the Turkish government. The Argentine aircraft were modified in Argentina with kits supplied by Marsh Aviation and are annually deployed aboard the Brazilian Navyís aircraft carrier NAe Sao Paolo, having been certified to operate from carriers at the US Navy Test and Evaluation Center at Patuxent River, MD. In Turkey, Marsh Aviation worked with Turkish Aerospace Industries to convert retired Turkish Navy S-2Es into TurboTracker fire fighters.

Currently Marsh Aviation is involved in supporting the aircraft delivered to the CDF, but the company remains hopeful that further customers will order this highly capable aircraft. The yard at their facility at Falcon Field, Mesa, AZ holds several airframes purchased from surplus US Navy and Japanese Maritime Self Defence Force (JMSDF) stocks, which will hopefully one day be upgraded to TurboTracker standard and return to the air to perform the vital air tanker role.

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