Conair tanker in a drop - note external belly pannier tank modification. (Conair)

DAVID DORMAN looks at how the BAe 146/Avro RJ regional airliner is getting a new lease of life as a converted waterbomber of choice.

August marks the 80th anniversary of Scottish Aviation (SAL) at Prestwick in 1935. Today, the direct descendant of that company is BAE Systems Regional Aircraft, still based at Prestwick, and responsible for the ongoing airworthiness, support and engineering for some 500 British Aerospace-built aircraft serving with 170 customers worldwide. The company, through its EASA Part 21G and J approvals, also carries out upgrades and modifications for any aircraft type.

Most numerous of the aircraft supported is the BAe 146/Avro RJ regional jet, of which some 220 are in service with 50 in long-term storage. Most serve as passenger or freighter aircraft but more are now operating in new niches for the type.

Among the more unusual roles for this ‘second life’ are aircraft that are converted and operating as aerial waterbombers, or airtankers, to fight the wildfires that are prevalent in North America during the summer season. Around 18 aircraft are now earmarked for this role.

The cost of fires

Neptune Aviation Services BAe 146 tackling a fire in the foothills. The 146’s low-speed handling seemed tailor-made for aerial firefighting, according to airtanker pilots.(Bob Cheatham)

Wildfires break out in forests and scrubland, spreading rapidly, fanned by strong winds, and causing enormous damage to property and the environment, plus loss of life. They are prevalent in the western US and Canada, the Mediterranean area and also Australia.

In 2012 across the US, there were 67,774 wildfires, which burned 9·33 million acres of land, costing nearly $2bn to suppress. In Canada, over the past 25 years, the average total area burned annually by wildfires is 2·3 million hectares costing between C$500m to C$1bn to suppress. The five biggest wildfires in California between 1991 and 2007 cost nearly $7bn in insured property damage.

Over the past decade in the US an average of 18 firefighters a year are killed on duty. A Lloyds of London report states 1,900 people were killed by 303 catastrophic wildfires worldwide between1984-2013.

Ground-based firefighters always tackle wildfires and have many techniques to combat the flames. However, remote and difficult terrain means that airtankers are quickest to the scene and able to contain the fires in the initial stages.

Airtankers — enter the quad jet

A Conair RJ85 waterbomber dropping fire retardant. (Conair)

In North America, airtankers are well-established for wildfire suppression but many aircraft used for these missions are of Korean War vintage, such as Neptunes or early turboprops such as Lockheed Electras. Age is catching up with them.

Following tragic accidents in 2002 involving firefighting C-130A Hercules and a Catalina, which both broke up in flight, the US Forest Service (USFS) and the Bureau of Land Management announced in May 2004 they were cancelling contracts with operators of 33 heavy airtankers. Later, after inspections and testing of these aircraft, some companies were re-awarded contracts.

The industry desperately needed new equipment and the USFS was determined to introduce the ‘next-gen’ airtanker. ‘Next-gen’ airtankers had to be better than the previous early generation vintage aircraft. They had to fly faster, be turbine- or jet-powered and, as Type 1 airtankers, have a capacity of at least 3,000 gallons of fire retardant.

Several airtanker operators contacted BAE Systems Regional Aircraft to study the practicality of the BAe 146/Avro RJ as a waterbomber. Sensing an opportunity, Regional Aircraft held discussions with the USFS and other operators. The USFS was particularly encouraged that BAE Systems, as the OEM, was prepared to stand behind the product and that operators could count on engineering and product support as required.

First flight trials were conducted in September 2004 in the US using a BAe 146-100 aircraft (supplied by Tronos plc) and were flown by the Chief Pilot of airtanker company Minden Air Corp. with a BAE Systems test pilot. The results exceeded their expectations and were better than experienced from flying the simulator.

Flying drop-type manoeuvres, the aircraft had a better angle-of-attack than was anticipated and approach angles were better. The aircraft was responsive and easy to fly, low-speed handling was good and there were fewer structural loads than had been anticipated.

Minden Air became the first US operator to select the BAe146 for this new role and acquired two Series 200 aircraft for conversion. Two other operators followed. Neptune Aviation Services of Missoula, Montana, is the biggest operator with six series 200s in operation after conversion by Tronos plc’s engineering facility in Canada, and plans a seventh. Air Spray of Chico, California, is converting three Series 200s, with first flight due in October, and has plans for a further aircraft.

Certification and conversion

Air Spray interior conversion to an airtanker. (via author)

All of these operators/converters have different internal tank and delivery systems designs and they are certificated under Supplemental Type Certificates (STC). Operators engage with BAE Systems in varying ways. For example, Air Spray utilises BAE Systems for loads, stress and fatigue analysis and damage tolerance for the aircraft.

The later build Avro RJ85 is also well suited to this demanding role and has been chosen by Conair of Abbotsford, Canada, for its future large airtanker needs. This followed further flight trials in southern Ayrshire during October 2009 carried out by test pilots from Conair and BAE Systems.

Conair is the world’s largest airtanker operator and converter with a fleet of over 60 fixed-wing aircraft of varying sizes. They have converted three RJ85s and operate them in their own right or through their US subsidiary, Aero Flite. Three more RJ85s are under conversion. They are looking to the long-term and have stated they expect the aircraft to remain in service for the next 20-25 years.

Their design features an external pannier tank wrapped around the fuselage under belly. BAE Systems analysed the structure and aerodynamic shape of the tank and supplied a pilot to help them assess what turned out to be a remarkably benign aerodynamic effect on the aircraft.

All airtankers of whatever design have to get Interagency Airtanker Board approval to demonstrate the accuracy of their retardant delivery systems onto a narrow piece of land and with equal spread over a grid of thousands of cups which measures the volume and consistency of the pattern when it hits the ground. Only with this approval can they be eligible for airtanker contracts.

Water bombers on call

The Neptune 146 waterbomber fleet. (Neptune Aviation Services)

Currently 16 out of 22 large airtankers in the US that are earmarked for six-year ‘Call When Needed’ contracts by the USFS are BAe 146/Avro RJs. In addition, two Conair RJ85s and a Neptune BAe 146 are on exclusive use contracts with the USFS. So the aircraft has really made its mark.

Andrew James, Engineering Director of BAE Systems Regional Aircraft stated: “The authorities are pleased that as the OEM we are taking such a close interest in these programmes. We provide specialist design and engineering services, including aerodynamic and computational fluid dynamics analysis; dynamic loads assessment and structural analysis.

Given the extreme nature of wildfire flying where for every flight cycle on a typical mission, the impact for structural and fatigue life is estimated at between four and seven cycles of normal flight, we think that OEM engagement is very important.”

This view is endorsed by Conair. Ray Horton, one of their most experienced aitanker pilots, recently said: “OEM involvement with such a programme is not a luxury. It’s a necessity.”

 

SAL and its successor companies designed and built nearly 1,000 aircraft. Countless thousands more were overhauled, while aerostructures and sub-contract parts manufacture also played a major role. Today, the continuing aviation legacy at Prestwick is a testament to the determination and vision of the original founders.


7 August 2015