Does anyone know if these small ex-crop-spraying aircraft are really effective, or is it a matter of being seen to do something by the authorities?
Ag aircraft were the first aircraft used for firefighting. Today's ag aircraft that are used in firefighting operations are quite different than typical older era "crop dusters," however.
The AT-802 is about the size of a King Air 200, but with a gross weight of 16,000 lbs, half of which is payload. It can fly at 170 knots to the fire, and carries as much as the S2 Tracker as a tanker, before they were converted to turbines. With bigger hoppers on the way, the 802 is classified in the US as a Type III tanker.
What's important isn't how much the aircraft can carry. More is useful up to a point, but Single Engine Air Tankers (SEATs) can be based at smaller airports, and can be based in many cases locally, closer to the fire. They're an "initial attack" tool, meaning they're often first on scene with a fire.
A SEAT is not only an initial attack tool, however. I've worked large fires with a SEAT quite effectively, building line, hot spotting, and doing tactical drops to support ground troops. Several SEATS can keep a nearly constant application on a fire, as opposed to a single large air tanker which can make one drop, then may have a long turnaround time when going back for retardant or foam/water, and fuel. I've done fires with other SEATs, for example, in which our turns were fast enough that our biggest delay was runway time...the holdup was on the ground loading and getting on and off the runway, rather than over the fire. Very effective at the fire side, where the incident command had a tanker overhead ready to drop continuously.
SEATs also offer cost advantages in some cases with respect to total cost of the aircraft and operation, and in many cases can deliver the retardant for less money per gallon or liter than other equipment. What aircraft is in use, how it's used, where, the distance to the fire, etc, are all important factors in making this determination. Suffice it to say that if a structure or life can be saved because the SEAT is closer on a given day and can get on the fire sooner, then it's a lot more cost effective...especially to the life saved or the home/property owner.
I've flown large air tankers and small air tankers, and each have their place. I spent years fighting fire on the ground, as well, and see it from that perspective, too. I've flown a variety of different single engine air tankers with different hopper sizes, configurations, types, and engines, and had an opportunity to evaluate their effectiveness from a pilot perspective, as well as go back and walk the fireline after and see how the coverage was on the ground, and the effect on the fire. I've also had the experience of making a forced landing in a fire once due to an engine failure in a SEAT, and have a little insight from that perspective, as well.
The SEAT program in the United States has been very effective.
I can't speak regarding finding employment in fire in Europe, but I can tell you that in the US it's nearly impossible. Very few positions come open, there are qualified people waiting when they do, and to get qualified takes a number of years of very specialized fire experience. The SEAT program is perhaps a little easier, but one will require experience in ag aircraft, at least a thousand hours of ag time, and in most cases needs to arrive already experienced in the 802 (or decreasingly, the Dromader). I turned down an AT-602 position this year in a brand new airplane, and I know that operator was having a hard time finding a pilot...but it wasn't a very good position and a friend of mine was killed in his other 602 last year at the same location...so I did fire in other ways, instead.
Aircraft like the M18 Dromader in question in this thread are very hardy, very simple aircraft, easy to work on, with low maintenance demands, and reliable systems and components. They're inexpensive to buy and to maintain. They've got a large hopper for chemical or water, and they are relatively easy to fly, as that type of equipment goes. They've got a big wing, they handle mountain flying and dropping well, and they're very commonly found in fire operations around the world.
They've got disadvantages, too. They have a very narrow drop speed range...only about 15 knots. Too slow, and the aircraft will stall on the drop, and too fast, and it will pitch up and may not be survivable. I've experienced both. I have experienced aerodynamic lockup of the controls and high speed buffet during dive recoveries in the Dromader. It's got a low flap speed range, which limits it's ability to drop downhill, as well as it's low drop speed range. Energy management is important, because one is restricted from having a lot of energy due to the lower drop speeds required. This is also a bonus for retardant delivery, however, as it allows better targeting and coverage consistency. The airplane has a long takeoff roll, but it's much better than the 802. The airplane has a more forgiving wing than the 802. The airframe is built like a tank. There have been three Dromaders that lost their wings in flight as a result of improper maintenance (overtorquing on the wing attach clevis fittings due to improper conversion from metric to SAE); the pilots survived in each case.
SEATs aren't used because they're window dressing. Large air tankers are a lot more impressive to the public. SEATs are used because they're effective, cost effective, and many programs find that they can field multiple airplanes with SEATs for the money, enabling them to be widespread with more immediate local coverage. They fly from smaller airfields in many cases, enabling more airfields to be used. They take very little support in the field, depending on how they're used.
It's important to remember that a SEAT, just like a Large Air Tanker, is simply another tool in the toolbox for the firefighters on the ground...and fires aren't fought from the air. It's the troops on the ground that put out fires. Aircraft simply assist them by performing precision work where the ground pounders want it done. In the air, we help modify fire behavior, but we're not there to put out a fire. It doesn't work that way. Even in an initial attack operation, our function is to slow the spread or treat surrounding materials to give those on the ground time to come in and work the fire by hand.