With the Cape fire season having a particularly bad year, many property owners owe a large debt of gratitude to the huge Air Tractor 802F firebombers. They have become an invaluable weapon in the armoury against the fires that sweep through the Cape nature reserves and threatened farms and houses.

The Air Tractor’s unique proposition is its ability to respond quickly and fly fast to a fire and quench it with 3000 litres of water – thereby often preventing a fire getting out of control. This is particularly important in the crucial early minutes of a wildfire, before ground forces can mobilise and get to the fire.

Development

In 1989 Air Tractor founder Leland Snow wanted to insulate his aircraft sales from farm economy downturns, which had harmed ag-plane sales. He consulted forestry and firefighting professionals and decided to upscale the AT503 into a two-seat 3000 litre AT-802F specifically for the initial attack of aerial firefighting.

The Air Tractor firebomber role was a natural outgrowth for the already successful Air Tractor 400 and 500 series crop sprayer.

Snow worked with a young engineer named Victor Trotter to develop and patent the world’s most advanced computerised, rotary, water bomb doors.

The 802F was a victory for Snow’s vision as it proved capable of working fires from remote strips, carrying an 800-gallon load, with the reliability of a PT6A turbo-prop and easy maintenance of a new airframe.

Firefighting

In Africa, KishuguAviation is the biggest operator of the AT-802s. It owns four AT-802Fs which they operate on behalf of the South African government’s Working on Fire (WOF) Expanded Public Works Programme. Kishugu also provides services to other clients such as local municipalities, large landowners and Fire Protection Associations across South Africa.

As all the Air Tractor 802Fs in South Africa are single-seaters, we asked Koos Kieck, a retired SAAF Mirage pilot and now an Air Tractor 802 fire-bomber instructor, to share his in-depth experience with his massive weapon for the fight against wildfires.

Koos explains that a key to the Air Tractor’s effectiveness is its hydraulically-driven rotary fire-gate doors on its hopper. The computer-controlled doors provide an even flow rate and allow the pilot to select gallons to drop, coverage level, and ground speed adjustment. In addition, there is an accelerometer for automatic adjustment of the fire doors.

Koos explains, “There are five settings for the width of the bomb gate opening we can use: if the spotter wants a long water drop, he will say give me coverage Level 1. Normally we use between a full load and Level 3.5. Thanks to the bomb gate computer, we have great control over the load drop rate. If we drop the whole load at once it covers about 150 metres, but we can extend that to 700-800 metres by reducing the flow rate.

On the Ground

I had seen the Air Tractors parked at Stellenbosch Airfield, but it was not until I got close that I realised that it’s a huge beast of an aeroplane. The propeller is an awe-inspiring 10 ft diameter.

Koos invited me to climb up to the cockpit, but I tried and then sheepishly gave up, as I had forgotten my mountaineering skills and was just not nimble enough to scale the slab sided fuselage and climb into the high cockpit.

With a maximum weight of 7,500 kg (16,000 lbs) the 802 is equivalent to seven Cessna 172s. Its empty weight is typically 3,200 kg so it is one of the few aircraft that can comfortably lift its own weight.

To power a firebomber designed to haul a large load fast, the 802 uses a Pratt & Whitney PT6-67AG, flat rated at 1,350 shp. It also has an overpower setting to 1600 shp which can be used for 20 seconds, as the limitation is the inter-stage turbine temperature (ITT), for really demanding airstrips.

With this much flat rated power, they are happy to operate even at a density altitude of 8000 ft out of Warburton and Ermelo in Mpumalanga. Working on Fire also have an 802F whose engine is rated at 1600 shp with an overpower of 1800 shp (Bomber 23 ZS-TFH).

The 802F burns around 300 litres of fuel and hour in the cruise and can carry 1,400 litres of fuel in the wings, in addition to 3,000 litres of fire retardant in the fuselage. Koos says that they normally only operate with 1,000 litres of fuel, so they can fill the hopper tank.

Flying the Air Tractor 802F

Koos describes what is like to fly this big machine onto a raging fire on a mountainside. “Once you have climbed into the cockpit, it is large and well laid out. The high cabin is incredibly strongly built and is air conditioned. The instrument panel is however unusual in that it is built around a large window into the hopper tank, with a prominent sub-panel directly in front of the pilot for switches.

The controls are conventional. There is a large control stick and three axis trim, so it can be trimmed for all phases of flight. It has a manual rudder and elevator trim, but surprisingly, the aileron trim is electric. Pitch trim is important as, when we dump the load, the CG runs backwards so it pitches up like a bitch. You have to push the stick into the instrument panel to stop the pitch, but quite often we are happy to just let it pitch up.

We can get airborne real fast when we are scrambled. The quickest we have done it is in three minutes. The aeroplane waits loaded, pre-flighted and ready to go. We use ground power for the first start of the day – thereafter the aircraft’s batteries. We do the pre-takeoff checks during the taxy out and being a turbine, it doesn’t need a run up.

The wind is particularly important for gross weight take-offs out of Stellenbosch. The 802F can cope with operating out of the relatively short and uphill runway 19 with a full load only if I have a 20 knot headwind. Otherwise even in a 10 knot tailwind, I takeoff downhill, but I first let out 200 of the 800 gallons of water. During the takeoff roll we keep our hands on the dump leaver and are prepared to dump the load if we are not getting airborne soon enough. We have had to do it if the wind changes unexpectedly.

At max weight we rotate at about 90 knots and it normally unsticks at about 95 – 100 knots. We use about 10 degrees of flap. We climb at Vx which is 120 knots and then Vy of 130 knots.

Once airborne there’s no stress – loaded we get about 1000-1500 fpm climb. The plane is that powerful. We get given a rough heading and some landmarks for the fire vicinity and we can see the smoke from far. Depending on the load, we cruise to the fire at 160 – 180 knots using 3400 ft/lb torque and just 1550 rpm on the prop. It hums along nicely using about 280 litres per hour.

We approach a fire at 120 knots with 10 degrees of flap. But sometimes rising terrain means we have to come in a bit hot. You don’t want to get slow with this big heavy plane as the speed bleeds off very quickly – especially uphill.

For the actual firebombing, we aim by just eyeballing it and using our experience and judgement. The spotter pilot tells us how we have done so we can quickly learn what works for any particular fire. The Incident Commander on the ground decides whether to use planes or choppers. He usually goes in first with a heli-tac team. Then he and the spotter decide what aircraft to use.

Knowing what the wind is doing is important. We drop the load downwind so we release it before we get to the fire. We normally aim to drop between 40 -50 ft above ground level. But when we have a crosswind it can get seriously difficult as the wind makes the water swirl anywhere so we then normally drop a bit lower. Even at 30 ft over the fire we don’t feel much heat as we are in it for less than four seconds and gone before it can get to us – and the Air Tractor is air conditioned.

In a narrow kloof you don’t want to get near 60 degrees of bank – because it wants to roll onto its back. And you can’t pull the stick back because it’s heavy. In tight spots we put the nose down to 190 knots (Vne is 225 knots) and we fly up the slope without flaps. When we dump the load we leave it to pitch up into the valley. The speed comes down to 75-80 knots and you fly it out. So we dump our load, pitch up, take our rivets while they’re still in formation, and go.

Once we have bombed, we head back to base the quickest way. The ATC at Cape Town International is always very accommodating, at times letting me cross the runways directly over the tower. But paradropping can be a real problem – their radio work is terrible, we can’t see the meatbombs and so we often do not know whether they are there or not. At Stellenbosch we have a gentleman’s agreement with the flying school students to extend their downwind to accommodate us. We have never had a problem.

We use 120 knots in the circuit as it slows down very quickly. Full flap limitation speed is 138 knots. We aim to cross the fence at 85 knots as it can really fall out the sky if you get slow, especially the one bomber we have which doesn’t have vortex generators.

We normally keep the engine in high flight idle, which reduces the spool-up from seven seconds to five. If we have to go around, that 7 seconds from ground idle to full power can feel like forever.

The landing is always interesting. It has a spring undercarriage so it’s like a Cessna 185 in that you can go bouncing down the runway, and it doesn’t stop. The stick doesn’t have to be all the way back, otherwise we hit the tailwheel first. So we hold-off until the long nose is parallel to the ground. Then we just hold the stick until it settles – which it does in a three pointer. If you do an unintentional wheeler you just relax back pressure on the stick and let the tail come down naturally. Don’t try and force it down because you want to apply the brakes. Full reverse thrust stops you as effectively as running into a wall.

We prefer to use reverse thrust on the prop to slow as it saves on tyres. But it has excellent short field performance – landing on 19 at Stellenbosch, we can easily make the first turnoff.

Depending on the distance to the airfield, we aim to do four to eight loads in an hour. Returning to base to reload is surprisingly quick. We don’t shut down the engine and the ground crew are really well trained, so it only takes around 2-3 minutes to refill. The fire retardant is already onboard so we just hit a button and it injects 1 litre per 1000 litres of water.

We don’t work a fire for more than three hours. We need a mental rest and body break.

The aircraft and engines have held up to South African conditions very well. You really can trust in Pratt and Whitney. I cannot think of any incident we have had engine-wise. We have had the odd wing scrape and runway excursion though. The 802 has teeth because of the tailwheel. It has a locking tailwheel – you lock it when you start the takeoff roll and unlock it when you get off the runway. You can land it without the tailwheel locked without too much trouble.

Conclusion

The Air Tractor 802F is a great first response weapon, but it works best when used in conjunction with the helicopters, and as part of a team of up to four Air Tractor firebombers. Fires don’t normally burn in a straight line, but we can only bomb in a straight stripe, so we need the choppers for the bits that get missed.

The spotter pilot is the key member of the team – he does all the work – but we get the glory. Whether we dump the full or a partial load is determined by the spotter.

It really is an incredibly effective fire fighting machine and is particularly vital for first response, as it can get to the fire fast and dump a load three times larger than a Huey,” Koos concludes.