What if we start a group design for a new fire-fighting airplane?

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riggerrob

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This was inspired by an aeronautical engineering student posting on this forum. His semester project is to design a fire-fighting airplane.

What if we start a group design of a new fire-fighting airplane.
It cannot be based upon an old military-surplus airframe, but can use military-surplus engines, avionics, etc.

We start by defining the mission.
How far from home base?
What type of terrain around the fire?
What types of trees and fuel?
How quickly do we need to extinguish?
Do we need to knock down the fire with a single drop?
How many tons of water or retardant to knock down a typical fire?
Do we need to be able to refill from a nearby lake or swimming pool?
How many minutes to turn-around at home base?
How long must it loiter?
How many drops before needing to refuel?
Does the airplane need to be able to land on water?
What sorts of avionics: radar, sonar, infrared, synthetic vision, etc.?
Does it need to be manned?
How far away van ground crew be stationed?
Will we need another airplane orbiting over the fire to provide a data link?
How many crew?

I am leaning towards a new airframe built around components (engine, sensors, auto-pilot, etc.) from a military-surplus RQ-?? military drone. The airframe will need to be stronger and lower aspect ratio for maneuverability in steep mountain valleys.

What are your thoughts?
 
Defining the requirement ourselves is going to be tricky. My knowledge of the science and technology of fire-fighting is substantially zero. It may be useful to quantify the relevant parameters for an existing aircraft.
 
uhhh. ok then thats a lot to think about lol but thats understandable they have in fact created an eight rotored *drone* for firefighting. now this can only be used with a connected hose and extremely low altitudes like anywhere from 25 to 60 ft i was thinking about upscaling it. or possibly just making another tanker type aircraft with a better water/retardant container/release. i feel we could in fact revolutionize the way we fight fires with just this forum. seriously. there are some smart people here (not me). in terms of manueverability i would say either a light cessna/beechcraft type aircraft or even a Helicopter. we could build off previous or existing designs and make them even better and more effective. so go ahead and drop some existing firefighting aircraft drawings or plans. do some research. etc. honestly i think we can do this. and we can give the ideas to aircraft manufactuers and they can send them to California USA and Australia and other places in need of these

one idea of mine is modifying a Boeing Vertol 234. it has the power for a large water/retardant load and the manuevering capabilities for tight spaces/low altitudes and valleys/hills etc.
1632437937954.png 1632438040832.png
 
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A lot of research would be required. Essentially, a large area that is burning would create updrafts and those in concert with prevailing winds. A helicopter would work best and be more precise. Time is the other factor. A large load of fire retardant would be important. It would be a function of the size of the fire against the number of aircraft needed to bring it under control quickly. And dropping fire retardant in windy conditions appears to favor the helicopter.
 
While it does get down into a complicated area of niche requirements, in some ways it's a good example for students because it forces you to think about the non-obvious stuff such as safety cases and certification requirements and how they relate not just to role, but how you perform that role - the safety case for a 747 dropping retardant from altitude is going to be substantially different from that for a Firecat actually diving into valleys to deliver it, which will be different from that for a CL415 skimming from lakes, which will be different from a Mil-26 using a bambi bucket.
 
Conspirator said:
...one idea of mine is modifying a Boeing Vertol 234...
Click to expand...

There are a bunch of Chinook air tanker conversions out there already - the Coulson-Unical CU-47 comes to mind. (Or were you talking about just using 234 dynamics with a purpose-built fuselage?)

There is nothing inherently superior about rotary-wing waterbombers. If drop accuracy (including hover) is the priority, then sure, assuming that quick response time and range limitations are not major concerns. A lot of that is going to be dictated by specific geography ... which maybe we should specify?

If transit time is key, fixed-wing is going to be preferred every time. Probably better if this exercise covered the categories already agreed upon by the major users. Water Scoopers and Medium Air Tankers are aging out (although, with its proposed 515, Viking keeps threatening an updated Canadair flying boat). Besides helicopters, that leaves:

Single Engine Airtanker (SEAT), Large Air Tanker (LAT), and Very Large Air Tanker (VLAT).
 
To narrow the mission: short range is currently covered by helicopters hauling Bambi Buckets. Helicopters may be able to drop precisely while hovering, but hovering vastly reduces their ability to hover out of ground effect. Few western helicopters can carry a full load above 10,000 feet MSL. IOW Helicopters can only carry serious loads while flying 40 knots or faster.

At the other end of the scale, this project will never get enough funding for Large Air Tankers.

So we are stuck somewhere in the middle between SEAT and LAT. For comparison an Air Tractor AT802F - on amphibious floats - has a useful load of 6,800 pounds and its hopper will carry 800 US Gallons. It cruises at 150 knots and climbs at 900 feet per minute. Range is 800 miles.
A Conair Firecat has a useful load of 12,000 and endurance of 5 hours.
A Conair Convair CV580 can carry up to 7,000 pounds in its 2,100 US Gallon tank. It cruises at 270 knots.

Since the average fire will be more than an hour from home base, cruise speed starts to become important.
Since the first part of the mission includes quick knock-down of small fires, speed is important.
The second part of the mission is in support of ground crews by dropping water and/or retardant multiple times per hour along fire lines. This requires endurance (large fuel tanks) to stay on scene for several hours.
The third part of the mission requires precision drops close to threatened buildings and roads ... often danger-close to people on the ground.

Since the first batch will tentatively be based near Denver, Colorado, they will have to fight both grass fires (prairies) and forest fires (mountains). The most dangerous wild fires often ignite near the boundary between grassland and forest. Density altitude is important because Denver is already 5,000 feet above sea level and many fires occur in surrounding mountains, so being able to carry a full load up to 10,000 or even 15,000 feet is important. Also consider that the majority of fires occur during hot summer weather, density altitude is still important.

Can fixed wing airplanes replenish from water without being full-fledged seaplanes?

This new airplane does not have to work alone. It will launch in response to fires detected by satellites, high altitude drones and low altitude spotter planes. Do the low altitude spotter planes need to be manned? Data links will provide quick down-loads of fire and local weather data.
 
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How big is a useful water load? Do we want a specific water load (10,000kg? 30,000kg?), or is it water delivered per hour, i.e. could you trade off size of load versus speed of the vehicle and number of trips per hour/day?

Bell Quad Tiltrotor would combine faster speed with many of the helicopter advantages.
 
Second-hands A380 or Stratolaunch's Roc: 150 to 250 tons of water and fire retardant.
We already know DC-10s and 747s can do it, so why not going for the largest aircraft out there ?

More seriously...

Can fixed wing airplanes replenish from water without being full-fledged seaplanes?
Click to expand...

If one aircraft can ever do that, it is the C-130 Hercules. Which will soon get floats for the USMC.

Icing on the cake: Hercules have fought wildfires since, what, the 60's ? and C-130A/B ?

I would say the stretched C-130J variant, mounted on floats.

Thinking about it, the similar but full-STOL Breguet 941 may have been a very fine "bombardier d'eau".

Beriev may do a similar job turning An-12s into seaplanes...
 
One factor not yet mentioned. It needs to both cheap to acquire and to maintain per flying hour. There is a reason that most of the larger firefighting aircraft come from the used market for conversion.

AIUI most of these aircraft are employed seasonally, and even in fire fighting season spend a lot of time sitting on the tarmac waiting for a fire. So no one wants too much capital tied up in them.

The is a website dedicated to the subject here.

Fire Aviation

News and commentary about wildland fire and aerial firefighting
fireaviation.com fireaviation.com

And the US Forest Service now wants to change the rules on the types of helicopter that can be used. See the lead article on that page. So maybe there is a niche market for a new helicopter.

If you want to grow old quickly (or die young) fly a firefighter!

Edit - and the point is made in a number of places that there is no one size fits all aerial firefighter. It is not all about the volume that can be carried. It is also about small manoeuvrable types that can get into (and out of!) narrow canyons to place a load of retardant just where it is needed.

And Denver, which is at the heart of the area affected in the Rockies, is already at 5000 ft above sea level. That saps aircraft performance and in particular their ability to lift loads of retardant. I noted somewhere that while a BAe146 can lift 3000 gals that has has to be reduced out of Denver on hot days.

But of course not everywhere has that problem eg Greek islands.
 
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Here's an outline for a rotary solution (from an actual aircraft designer):

hushkit.net

This is the helicopter we need for the most dangerous threat we face

A Helicopter the World Needs Dr Ron Smith joined the British helicopter company Westland in 1975, working in Research Aerodynamics, remotely piloted helicopters, before&nbs…
hushkit.net hushkit.net

HushKit has also featured a list of firefighting aircraft, whether these are "the best" as the title states is another matter:

hushkit.net

11 best firefighting aircraft

The world is burning. Infernos rage across the globe, with many nations in the grip of fires of biblical proportions. Facing these firestorms is a motley force of aircraft, crewed by heroic and exc…
hushkit.net hushkit.net

Not that I'm particularly capable of considering this problem but it seems that wildfires are changing in nature: Extreme drought, adverse changes in biotopes result in more frequent, faster and incredibly vast fires. I'm hard pressed to imagine any aviation solution scaling up to a "mega" fire that's already out of control - in the U.S. steering and containment efforts are practiced, in Russia some fires seem to burn out wholly uncontrolled.

So my, pardon the pun, "hot take" solution would be a system, not a single aircraft. Complete awareness, speed, and accuracy the order of the day, the battle being won or lost in the first minutes or hours of the fire. Constellations of communication satellites could have, among them, early warning IR sensors primed for known risk areas. For really high risk environments, drones could be deployed for either prompt close observation or even as primary responders/fire containment units with limited suppression capabilities.

The main "cavalry" would be fast, near supersonic (or for remote locations, why not supersonic) bespoke airframes with laser/GPS guided precision gliding "bombs". Water and chemical suppressants for inhabited areas, but for remote locations perhaps with a liquid nitrogen payload. You'd have to consult an expert on this, but extreme cold coupled with momentarily depleting atmospheric oxygen could buy enough time for ground units to arrive and still find a manageable situation.* The ground units, btw, might also need a mode of rapid transit - there are skydiving "airborne" units that I know of at least in California but not every firefighter can train up to that level.

Of course all this is a bit cinematic and ridiculous but, frankly, so is the situation.

-

* Edit: Dispersion perhaps by aerodynamic rotation of the gliding container or small/slow explosive charges when on target area. Depending on geography and type of flammable material on site, deploying "clustering" suppressants - i.e. glorified water balloons - could also be advantageous.
 
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Too much speculation. The mission? Extinguish the fire as quickly as possible. Fire season is known and even for non-seasonal events, a series of passive sensors would be more cost-effective. I mean if the National Weather Service is telling civilians that conditions exist that are favorable for fires breaking out, what? Just wait around until it starts? Wrong thinking.

Only two types of aircraft are really suitable: converted cargo planes and bombers.
 
overscan (PaulMM) said:
Bell Quad Tiltrotor would combine faster speed with many of the helicopter advantages.
Click to expand...

I've had the pleasure of making helitack acquaintances, and the advantages (which definitely exist) are not overwhelming, and are commonly misunderstood. The helicopter is best used against smaller grass or brush fires (or simply transporting the work crew). Hover is very infrequently used. Having speed on is much safer, particularly when using the Bambi buckets. Much of the work that requires air attack is happening in terrain and at altitude, which does not favour rotary-wing under heavy load. Add to that the inconsistent air (temps/turbulence/visibility, etc) produced by the fire itself, and there is zero appetite for hovering over a larger fire.

The helicopters and smaller tankers are generally just used for what they call initial attack. They're the guys trying to keep the small fire small. The larger tankers are playing a completely different game.

With a larger fire, the helitack guys are usually deployed to start a new fire line quite a distance from the main fire, or sometimes even starting back burning ops in areas it's difficult to otherwise get a crew to. They aren't really used as tankers in the traditional sense in those scenarios.

What the helitack unit does let you do is bring in a work crew, and support them using the bucket. And you can use the bambi bucket in any nearby lake, pond, cattle ponds, even swimming pools. That lets you, at least in theory, in the right circumstances put more water on target faster to support the ground crew. Low speed and altitude also help drop accuracy and navigating difficult/hazardous terrain.

Even something very small and slow like an Air Tractor lugs four or five times as much retardant or water as a typical helitack unit. The operating costs are lower as well. One issue with both is forward basing-- which usually isn't accounted for in the aircraft costs per hour, but definitely affects the bottom line.

There really isn't a one-size fits all approach. The larger tankers drop bigger loads, but from higher altitudes and speeds, which means the dispersion and accuracy is generally much lower. They also need established airfields. Frequently the smaller guys are able to deploy from forward improvised locations and deliver more load per hour -- a common way of measuring effectiveness. That they also do it much, much cheaper, isn't lost on most organizations, which is why the giant tankers make for impressive photo ops, but are more rarely used. Something like the CL-215 and -415 really hit a sweet spot with the market in regards to load/speed/endurance/cost and the ability to scoop from lakes.

The bigger helos like the Skycrane and Chinook (or your quad tilt-rotor) are a pretty niche role, but they do get used. Generally in hazardous terrain that the larger, faster tankers cannot safely navigate or putting loads on spot fires outside the main fire.

It's pretty fascinating to watch an air op, and all that entails from the tankers to the air attack and management flights. We've got a few units usually deployed nearby, even Skycrane as a frequent visitor at our local field. I'm far from an expert, but there are a lot of guys who like to "talk shop" when they're deployed out here. Makes the summers more interesting.
 
EwenS said:
Did you see this?
Click to expand...

No, hadn't visited the site yet. As said, "hot take". Interesting that the solution was for the containers to rupture in the air already; the ability to use an unconverted Herc for firefighting might have been the main innovation there. I was thinking more in the lines of being able to target specific areas or levels of the fire not unlike direct, delay or proximity fuses (though mechanically "actuated"). I have an affinity or a tendency for complicated solutions though.
 
Archibald said:
Second-hands A380 or Stratolaunch's Roc: 150 to 250 tons of water and fire retardant.
We already know DC-10s and 747s can do it, so why not going for the largest aircraft out there ?

More seriously...

Can fixed wing airplanes replenish from water without being full-fledged seaplanes?
Click to expand...

If one aircraft can ever do that, it is the C-130 Hercules. Which will soon get floats for the USMC.

Icing on the cake: Hercules have fought wildfires since, what, the 60's ? and C-130A/B ?

I would say the stretched C-130J variant, mounted on floats.

Thinking about it, the similar but full-STOL Breguet 941 may have been a very fine "bombardier d'eau".

Beriev may do a similar job turning An-12s into seaplanes...
Click to expand...
Dear Archibald,
We disagree on which C-130 variant would be best for fire-fighting.
I wonder if we even need floats to scoop water from lakes. Can a snow-ski equipped airplane skim a lake slow enough to scoop a full load of water?
Why did you suggest a stretched C-130?
Stretching increases empty weight.
Meanwhile, a short C-130's cabin is already too big for the largest water tanks that a C-130 can lift.
 
When we compare an Air Tractor on wheels versus floats, the wheeled version can lift 8,970 pounds worth of retardant while the version with amphibious floats can only lift 6,800 pounds. That extra 2,175 pounds might require fewer drops to knock down a small fire.
What if you install snow-skis and a snorkel?
Could it scoop water from a lake?

We know that light STOL bush planes on snow-skis have stunted by skimming lakes, but is the technique practical for scooping?
 
We can save hundreds of thousands of dollars in certification costs if the new airframe is un-manned. That also reduces life-insurance costs and crew fatalities. I was thinking of installing auto-pilots and data links from "last week's fashion" in military RQ-??? drones. Also consider that the cost of bolt-in-bits is way more than the cost of the basic airframe.
 
Prevention not certification costs. Put in sensors. Create a ground fire watch consisting of civilians. Scooping water out of a lake at speed is not the same as scooping water out of a bowl. Have drones on standby to video suspected sites.
 
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riggerrob said:
Archibald said:
Second-hands A380 or Stratolaunch's Roc: 150 to 250 tons of water and fire retardant.
We already know DC-10s and 747s can do it, so why not going for the largest aircraft out there ?

More seriously...

Can fixed wing airplanes replenish from water without being full-fledged seaplanes?
Click to expand...

If one aircraft can ever do that, it is the C-130 Hercules. Which will soon get floats for the USMC.

Icing on the cake: Hercules have fought wildfires since, what, the 60's ? and C-130A/B ?

I would say the stretched C-130J variant, mounted on floats.

Thinking about it, the similar but full-STOL Breguet 941 may have been a very fine "bombardier d'eau".

Beriev may do a similar job turning An-12s into seaplanes...
Click to expand...
Dear Archibald,
We disagree on which C-130 variant would be best for fire-fighting.
I wonder if we even need floats to scoop water from lakes. Can a snow-ski equipped airplane skim a lake slow enough to scoop a full load of water?
Why did you suggest a stretched C-130?
Stretching increases empty weight.
Meanwhile, a short C-130's cabin is already too big for the largest water tanks that a C-130 can lift.
Click to expand...

"The best is the ennemy of the good" - unfortunately.

I suggested it
- because Hercs are already valuable fire-fighters
- because the C-130J is the more recent variants
- because the USMC has a "Herc on floats" project

Also this

Can fixed wing airplanes replenish from water without being full-fledged seaplanes?
Click to expand...

this begs the following question. That USMC Hercules-on-floats
- is the modification permanent ?
- or can the floats be removed and wheels extended ?

This will determine the "fully fledged" (or not), side of your question (and my answer to it).

An amphibious Herc' - with "wheels inside the floats" or "wheels besides the floats" would be nice.
For firefighting it could take water either from the ground or from a lake - just like Canadairs do nowadays.
 
UpForce said:
".... perhaps with a liquid nitrogen payload. You'd have to consult an expert on this, but extreme cold coupled with momentarily depleting atmospheric oxygen could buy enough time for ground units to arrive and still find a manageable situation.* ... * Edit: Dispersion perhaps by aerodynamic rotation of the gliding container ... when on target area. Depending on geography and type of flammable material on site, deploying "clustering" suppressants - i.e. glorified water balloons - could also be advantageous.
Click to expand...
Proper application of aerodynamics and centrifugal force can disperse liquid cargoes without explosives.
 
riggerrob said:
Proper application of aerodynamics and centrifugal force can disperse liquid cargoes without explosives.
Click to expand...

Yup, meant as alternatives.

Liquid inertia in a container, as well as changes in mass distribution during dispersion are likely very non-trivial, especially if the thing is (somewhat) guided. Might as well go for an aerodynamically rotated pump only but assuming these gliding "drop tanks" or whatchamacallit are non-retrievable, all complexity adds to the cost and increases possible failure modes. Plus the currently preferred drop mode seems to be a rather (ahem) sudden dump, suggesting anything lighter might be insufficient. Perhaps water balloons of different constructions and volumes are a better idea to get through and douse every aspect of the fire column at once. But note that these speculations of mine are becoming more, not less, uninformed, at least for the time being.

Someone mentioned fire seasons above. That made me think of firefighting aircraft carrier groups ...
 
riggerrob said:
Archibald said:
If one aircraft can ever do that, it is the C-130 Hercules. Which will soon get floats for the USMC.
Click to expand...
... Meanwhile, a short C-130's cabin is already too big for the largest water tanks that a C-130 can lift.
Click to expand...

Granted the short Hercules' cabin is too big for the largest retardant tanks it can lift. However, if those tanks can be removed in the 'off season', the aircraft's owners can employ if as a profit-making cargo aircraft. All dedicated air tankers are hangar queens when they aren't waterbombing.

A totally new airframe design won't save you on certification and, besides, existing air tankers all fly under experimental status anyway. If "we are stuck somewhere in the middle between SEAT and LAT", you are in the realm of the Viking 515. And Viking is trepidatious about building this warmed-over 54-year-old design for which they already own the tooling and hold the rights to. Like Canadair before them, Viking needs a convincing argument that their air tanker can 'moonlight' as something else outside of fire season.

In BC, the 'customer' has skewed away from old 'Medium Air Tankers' in favour of SEATs on floats. The argument is that the Air Tractors can get into smaller lakes (or lakes in steep-side valleys) for scooping. In reality, it is about finding the cheapest solution that it politically-acceptable when wildfires aren't actually burning Lytton to the ground.

So, your challenge is to produce a design with multiple uses to make useful year-round. Or, so cheap (and simple to understand), that politicians will yum it up ;)
 
what about low budget fire departments/states/countries??? i was thinking something like a Sikorsky VH-92 with the Heavy Lift system implemented into the airframe. and the rear cargo area replaced with massive water/retardant tanks??
everyone knows about the Erickson Aircrane Firefighting. its absolutely genius with the interchangeable water/retardant containers that are possibly pre-filled. but they are extremely expensive to purchase/operate/maintain and most fire departments dont have any.
 
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Beriev's seaplane is already very apt for it's mission. Needs new engines, tho.
 
It's enormous! Not quite suitable for the mission here.

Regarding seaplane Vs Land, I think it's possible to design a high speed snorkel to scoop water, alleviating the needs for a seaplane and inherently heavier structure.
 
For me, you are talking of two or three specialist aircraft. For inland areas with a decent lake in range you can use a rotary wing like the Chinook or CH-53K with a hose for replenishing water from lakes.

The rest is not so easy but two fixed wing types makes sense. No point in using a behemoth when something smaller can do the job while the larger type will have longer legs and carry more retardant/water. There is a reasonable number to chose from.

Ability to operate and stage from water based environments definitely helps which does reduce that number somewhat.
 
Locate the most fire-prone areas. Get the length and width. Determine the number of aircraft needed based on the total land area. Divide into grids and assign. Speed of detection is the first priority.
 
Some thoughts:
1. Given the sparse demand, cost per flight hour is not a very important consideration. Instead maximum capacity in a short amount of time is needed.

This is inverse of most commercial aircraft made to optimize flight hour cost over decades of high uptime use.

An alternative solution is multi-use aircraft, but without identifying the other use cases a design could not be optimized and as such I'll skip this concept.

2. Speed requirements really depends on the stage of fire that this is expected to fight and the amount of early warning.

Given that the globe now has persistent coverage of IR early warning satellites, the if data access is granted fires can potentially be located down to the minute.

One can combine this with very fast responding systems to defeat fires before they could spread, reducing the problem exponentially. Thus, Rockets as the fast response system can be useful despite low payload per unit cost. Gain reuse via wings/propulsive.
 
Conspirator said:
what about low budget fire departments/states/countries??? i was thinking something like a Sikorsky VH-92
Click to expand...
The S-92 (I think we can rate the Presidential level of fittings on the VH-92 as nice to have rather than mission-essential) is still a $15-27m helicopter. Even second hand it's a $6.5m helicopter (figures from a quick web-search, so don't bet the company on them). Taking an aircraft of that size and cost and making major structural modifications is going to be massively costly. As is certification. Even fairly minor STCs can have major certification costs. Accessible to low budget organisations this won't be.

Affordability is a reason fire-fighting aircraft tend to be overwhelmingly second hand. In the article below, an operator considers a requirement for an extra $60k of equipment to be virtually pricing him out of the market. Rather than a new design, we might be better off looking at new concepts of operations for existing designs.

fireaviation.com

Forest Service makes major changes in helicopter contracts - Fire Aviation

One vendor said new requirements could reduce the number of helicopters on contract
fireaviation.com fireaviation.com
 
DWG said:
Affordability is a reason fire-fighting aircraft tend to be overwhelmingly second hand. In the article below, an operator considers a requirement for an extra $60k of equipment to be virtually pricing him out of the market. Rather than a new design, we might be better off looking at new concepts of operations for existing designs.
Click to expand...

That just immediately makes me worry that the damage of (large scale) fires isn't appreciated realistically, or that there's something very much off about managing the issue and the procurement of appropriate capabilities.

Merely by happenstance, just a couple of days ago, I saw a literary review of research on the subject of how wild animal (and subsequently zoonotic) diseases are driven by wildfires. Pretty specific, but apparently still widely enough considered worthy of study. This tells me that likely the problem isn't the lack of knowledge, only that there remains a deep disconnect in how human economy values nature's "services" (another discussion altogether whether it is appropriate or an existential threat to measure those services in fungible ways or in any way commensurate to human technologies, but that is not to say they shouldn't be valued in some rational, ethical and actionable fashion).

Not that I'd declare it knowable on these bases that new bespoke firefighting aviation designs are called for. Many human/technological capabilities are poorly apportioned and woefully underutilized as it is. All ideas welcome, I guess.
 
UpForce said:
DWG said:
Affordability is a reason fire-fighting aircraft tend to be overwhelmingly second hand. In the article below, an operator considers a requirement for an extra $60k of equipment to be virtually pricing him out of the market. Rather than a new design, we might be better off looking at new concepts of operations for existing designs.
Click to expand...

That just immediately makes me worry that the damage of (large scale) fires isn't appreciated realistically, or that there's something very much off about managing the issue and the procurement of appropriate capabilities.
Click to expand...
Pacific Gas & Electric's involvement in the 2019 California wildfires is a pretty classic example of people not paying attention. They cut back on brush clearing and equipment replacement for their electricity transmission lines to maximise profit, and ended up bankrupting the company to the point they owed $25.5Bn in fire liabilities even after taking shelter in Chapter 11.

The wiki article on Cal Fire's air branch is probably worth a read to get a perspective:

en.wikipedia.org

CDF Aviation Management Program - Wikipedia

en.wikipedia.org en.wikipedia.org

This is probably the best funded aviation fire fighting unit there is, and it's almost always bought its aircraft second hand.
 
Arguably though, the use of primarily secondhand aircraft for firefighting has long since reached the point of diminishing returns in those cases where it wasn't a cost fallacy from the outset.
 
riggerrob said:
I am leaning towards a new airframe built around components (engine, sensors, auto-pilot, etc.) from a military-surplus RQ-?? military drone. The airframe will need to be stronger and lower aspect ratio for maneuverability in steep mountain valleys.
Click to expand...
Conspirator said:
one idea of mine is modifying a Boeing Vertol 234. it has the power for a large water/retardant load and the manuevering capabilities for tight spaces/low altitudes and valleys/hills etc.
Click to expand...
I took this as a challenge to (poorly) "design" a mishmash of some concepts posted here:
1632687813047.png
If you think about it, the truncated (for low aspect ratio like riggerrob wanted) RQ-4 wings look like the Boeing Vertol 347 wings... (sorry no quadrotor: I felt it's unproven tech and wanted to be as conservative as possible).
However this drawing is for laffs as the scale is incorrect: the RQ-4 is at most 15ft tall while the Chinook is 8 minus the rotor. It mean it still might work but anyway we don't actually need a great deal of RQ-4 subsystems, it might be better to incorporate the MQ-8C systems in the Chinook cockpit (the Bell 407 is around 8 ft minus the rotor)

Let's assume for this scenario the fire is the Henry fire in California, an F class fire (1320 acres) contained on 7/30/21. It's 34 days so close to average for a large fire. (This probably doesn't matter so much though as it should be able to fight any kind of fire)

Henry Fire | CAL FIRE

www.fire.ca.gov www.fire.ca.gov
How far from home base?Not sure, not enough data. ~60.5 miles from Bald Mountain helitack base in Long Barn, CA to fire midpoint (but that's by walk)
What type of terrain around the fire? Sierra Nevada mountain range. Lots of dense forest, 3 nearby lakes and lots of rivers and small streams. When the fire was contained, it was bordered around where large rivers and highways were.
What types of trees and fuel?Douglas Fir, Redwood, Sequoia, etc. Large, possibly old-growth forest
How quickly do we need to extinguish?Wildfires last on average 37 days. Aim for 30% containment by 2 days and 80% by 6 days if possible.
Do we need to knock down the fire with a single drop?I think this is physically impossible :( It would be nice if we had that big of a plane though...
How many tons of water or retardant to knock down a typical fire?Like previous q, retardant isn't dropped directly on fires but around it, to contain it, box it in. Even water isn't dropped directly on, it's dropped right in front
Do we need to be able to refill from a nearby lake or swimming pool? We can, not sure how big the creeks/streams are but the rivers and lakes and reservoirs seem quite large. No swimming pools
How many minutes to turn-around at home base?TBD/not sure. 234 carries a 3000 gal bambi bucket, but that shouldn't take much time to put on, right? Possibly could take some time if rotors need to be unfolded
How long must it loiter?TBD/not sure
How many drops before needing to refuel?Likely several
Does the airplane need to be able to land on water?No
What sorts of avionics: radar, sonar, infrared, synthetic vision, etc.? MQ-8 uses the tactical common data link (TCDL). Things to make Helicopter UAVs fly (I wouldn't know, I work in propulsion and even there I'm bad)
Does it need to be manned?No
How far away van ground crew be stationed?Some around the fire but otherwise back at base?
Will we need another airplane orbiting over the fire to provide a data link?Unmanned, so we might? Firefighters use aircraft like the OV-10 Bronco for recon (they don't drop any retardant), these can be used to guide it
How many crew?Drone pilot

I'll work on a better 3 view (prob CAD) and the math for this in a bit (I generally dislike math). Could also make an excel calculator for some kind for people to experiment with say different rotor blade lengths. This would change a lot of minor factors such as blade solidity and a lot of major factors like whether it'll get off the ground or not. To convert to tiltrotor, I'm changing the blade length to 70% the original (252 in radius) otherwise it'll hit the sides so that's not good...

An educational website containing extensive information on the Boeing CH-47 Chinook helicopter.

The CH-47D Chinook Structural Drawings.
www.chinook-helicopter.com
(If this design is bad, at least these links are good)

One more thing: lot of discussion on water/retardant but there are alternate ways of fighting fires that are still on the drawing board. I heard a lot about using lasers (I believe to start smaller fires and starve the large one of fuel) and my wild guess is it could be possible to use sonic booms low to the ground (though that would destroy other nearby things). That would require the YAL-1 or the Myasishchev M-25 to be developed however, bit overkill for firefighting.
 
Hypersonics Anonymous said:
riggerrob said:
E
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One more thing: lot of discussion on water/retardant but there are alternate ways of fighting fires that are still on the drawing board. I heard a lot about using lasers (I believe to start smaller fires and starve the large one of fuel) and my wild guess is it could be possible to use sonic booms low to the ground (though that would destroy other nearby things). That would require the YAL-1 or the Myasishchev M-25 to be developed however, bit overkill for firefighting.
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has that ever been done? the sonic booms? i can only seem to find proposals for it. using high speed military aircraft. Sonic booms experienced by communities usually have overpressures of less than two pounds per square foot (psf). Buildings in good structural condition generally bear no damages from overpressures smaller than 16 psf. Minor damage, such as shattering of windows, may occur between 2 and 5 psf. However, this is rare.
 
Hypersonics Anonymous said:
Conspirator said:
has that ever been done? the sonic booms?
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This article claims tests with Mig-21s did what you say but an aircraft designed to intentionally cause damaging sonic booms (that would be blunter, though other factors play) would cause bigger ones: https://www.aerotime.aero/26067-myasishchev-m-25-soviet-plane-that-would-kill-with-sound
Just throwing ideas out there, for the budget of your local fire department none of said thrown ideas could be developed...
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i have in fact seen the model but i would love more info. now i understand the budget issue but i mean scaling them down quite a bit. without cutting corners because we all know what happens if you cut corners in aircraft design. im just trying to stimulate the mentalities here. apologies.
 

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