Okay, this might be more of a 'scenario' but I've posted it here because I'm looking for more of a engineering critique.
In a nutshell (spoiler alert!), the concept is to revive the concept of land-based Medium Air Tankers (MATs) using the growing number of now-redundant early-model Dash 8 regional airliners. The idea is to use greater numbers of landing-based MATs capable of operating out of rural airstrips close to the action.
My sense is that the size of air tankers is being driven up, in part, by budgetary considerations - ie: if firefighting agencies lease small numbers of Large Air Tankers, it makes it more difficult for Government to cut their operational budgets.
A second component of the proposal is finding 'gainful employment' for these Medium Air Tankers outside of fire season. Surplus early-model Dash 8s are already being converted into cargo carriers. That seems a nature fit for work during the off-season.
The point of that 'extracurricular employment' is making the concept more fiscally palatable to both Government and wildfire response agencies. In this scheme for a Common Medium Air Transport, the agencies of Australia, Western Canada, and the Western US would be able to share interchangeable retardant tanks and ancillary air tank gear during their local fire seasons (although I'm aware that the respective fire seasons are beginning to merge).
I am hoping that this just might turn into an actual RW proposal. So, if you see any holes in the concept, let 'er rip!
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Oversight of Firebombing in Australia - Fixed-Wing Air Tankers
For those who aren't familiar, waterbombers in Oz fall under the umbrella of the National Aerial Firefighting Centre (NAFC) but it is the Governments of each Australian State and Territory which is directly responsible for fighting bushfires. As NAFC puts it, "the aim is to facilitate resource sharing and cooperation between agencies across the country."
Up here in the Great White North, there is a similar arrangement through the Canadian Interagency Forest Fire Centre in Winnipeg. As with NAFC, CIFFC began with a mandate primarily concerned with coordinating equipment-sharing among local wildfire firefighting organizations in Canada. The dissemination of fire management information naturally followed. And then, in common with any centralized bureaucracy, the dictating of 'standards' inevitably begins. This could be helpful but such organizations drop into following the latest in bureaucratic fads.
What if the bureaucracy is just wrong? According to NAFC: "Fixed-wing aircraft that are used for firebombing tend to be of the larger agricultural-style, specially modified for firebombing. These aircraft are sometimes referred to as SEATs (Single-Engined Air Tankers).
This type of aircraft particularly suits the conditions most often encountered in Australia where there are relatively few long paved runways, but plenty of agricultural airstrips." One follow-on sentence covers all other classed of air tanker, saying: "Larger fixed-wing aircraft have been used where appropriate and cost-effective." Really?
"Rum: Opinion is divided on the subject." - or Size Matters
That NSW just bought a 737 Fireliner suggests that the NAFC conclusion is far from universally accepted. A quick scan of the Aussie press and social media posts, reveals a lively debate about the appropriate size of fixed-wing air tankers for Australia. In the last federal election, the Labor Party advocated buying "six Large or Very Large Air Tankers". No aircraft types were mentioned but NSW refers to its Coulson 737 conversion as a Large Air Tanker (LAT) whereas 10 Tanker's borrowed DC-10s are considered Very Large Air Tankers (VLAT). Both are impressive - the LAT carrying more than 15,000 litres of retardant, the VLAT having more than twice that capacity at just over 35,500 litres. Indeed, one drop by a DC-10 Air Tanker is said to be "equivalent to 12 drops" by a propeller-driven Firecat. And that's the part that has me wondering about an air tanker category which is altogether missing in this debate.
What about the Medium Air Tanker category? In a 03 January 2020 radio interview, former NSW Fire Commissioner, Greg Mullins, said "... large aircraft don't put out fires ... if you had 20 to 30 of these medium-sized aircraft, that have rapid turn-around, you could make a material difference ...". Mullins' point about large aircraft is true of all air tankers. The purpose of firebombing is to "give firefighters on the ground an edge". The medium-sized aircraft Mullins refers to are the Canadair and Bombardier 415 'Superscooper' flying boats. But there is also a case to be made for land-based Medium Air Tanker.
Australia uses US aerial firefighting terminology and classifications. Under the latter, a mid-sized or Medium Air Tanker is classed as one capable of carrying 2,000-to-3,000 US gallons (7,500-to-11,500 litres) of fire retardant or water. So, what ever happened to the medium air tanker category? It seems to have been overshadowed by those smaller SEATs. A typical small air tanker - the AT-802F - carries 3,104 litres (the float-fitted Fire Boss is reduced to 3.028L). That compares well with typical old-school medium air tanker - the Conair Turbo Firecat conversion which could only carry 3,296L despite having almost twice the power. [1] According to Conair Group, the natural replacement for their old Firecat series is the Q400-MR. [2] France decided to bite and their Securite Civile now fields Q400-MRs to replace its Turbo Firecats. [3]
So, an airframe with a wing area of 64.00 m² instead of 45.06 m²; twin 5,071 shp turboprops instead of 1,220 shp; and an empty weight of 39,284 lbs/17,819 kg instead of 15,000 lbs/6,803 kg. I get it, Conair had to work with Bombardier and Bombardier was pushing its then-current production Q400 airframe (and offering a trade-in programme for older Q400s had obvious benefits for new Bombardier production). Fortunately, Bombardier has since pulled itself out of the equation. [4] I'm thinking that this may free up another airframe which Bombardier wanted to downplay.
The Conair/Cascade Q400-MR air tanker can carry 10,000 liters of retardant. It earns its 'Multi-Role' suffix by being about to revert to a passenger- (or cargo-) carrying role in a few hours. Of course, that long Q400-MR fuselage is mainly empty while firefighting. In other words, while acting as an air tanker, the Q400 airframe represents a lot of dead. That wouldn't be the case were air tanker conversions based upon the earlier-model Dash 8 airframes - what Bombardier redubbed the Q100 and Q200. [5] Those earlier Dash 8 fuselages are 10.26 metres shorter than the Q400. Eliminating added-on fuselage sections reduces airframe empty weight by 6,700 kg. [6]
(Caption: The sideview, below, shows a Securite Civile Q400-MR dropping water. The inset is to help give a better sense of the 'extra' airframe for the stretched Q400 series.)
(To be continued ...)
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[1] The AT-802F has a 1,350 shp PT6A-67AG, the Fire Boss a 1,600 shp PT6A-67F. The Conair Turbo Firecat needed two 1,220 shp PT6A-67AFs to carry a similar load.
[2] The actual Q400-MR conversions were performed by a former Conair division - Cascade Aerospace (bought by IMP in 2012). As a result, Conair's Q400-MR is closely related to the Cascade Aerospace Q400-PF (Package Freighter) conversion.
[3] The 'FireGuard' package (retardant tank and associated plumbing) can be removed from the Q400-MR in a few hours. This is to allow the Securite Civile to employ its aircraft as passenger carriers in the off-season.
[4] Bombardier sold the rights for the Q400 to Longview/Viking in November 2018. Back in May of 2009, Bombardier had ended Q200 and Q300 production (which will not be revived in production, DH/Viking said in December 2019).
[5] Q100 and Q200 were marketing names, the proper designations remain DHC-8-100 and DHC-8-200 series. Simplified ICAO codes are DH4A and DH4B (with DH4C and DH4D being the longer Q300 and Q400, respectively). CASA sometimes just refers to these aircraft as an '8Q'.
[6] The airframe empty weight difference is based on 17,819 kg for the base Q400 versus 10,477 kg for the Q100/Q200 less the ~635 kg difference in dry weight between a of pair of PW123 and PW150A turboprops.