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Using a 747 to Fight Wildfires

RotJ writes "It's fire season again. And the government just grounded 33 aging air tankers on Monday due to safety issues. Looking for a modern solution, Evergreen Aviation has come up with a 747 supertanker with 24,000 gallons of tank space onboard, which allows it to cover seven times the area of today's largest existing airtanker. In addition to fighting fires, it will be able to contain oil spills and 'perform challenging homeland security missions' like neutralizing chemical or biological attacks. And think of how many John Goodmans you could cover with fire retardant. Be sure to watch the videos."

47 of 276 comments (clear)

  1. Speed by JohnHegarty · · Score: 5, Interesting

    How much can you slow down a 747.... would it no make it hard to hit the target at 600mph

    1. Re:Speed by Anonymous Coward · · Score: 3, Insightful

      Well, ofcouse, I dont know if the guy is accurate or not.
      But he claims about 170mph for takeoff.
      I would see this as a lowest for flying speed at low altitude.
      But that's still pretty damn fast

      http://pupgg.princeton.edu/~phys103/quiz97/q7_an s. pdf

    2. Re:Speed by AllUsernamesAreGone · · Score: 5, Informative

      747s can go down to 250knots and be managable - heavy load turn stall speed is around 210knots IIRC.

    3. Re:Speed by Analogy+Man · · Score: 5, Informative
      One would not need to be going at cruise speed, but you bring up a very important point. I would shudder to think of a 747 trying to deal with a low altitude drop in mountainous terrain.

      I am not sure a commercial airliner is the best recipe for this problem. In general they are designed to get up to Mach 0.78 - 0.84 and cruise along at 35,000 ft.

      A derivative of a military aircraft would be more appropriate. Problem is, by the time the National Guard has used them up (repair costs exceed operating value) there is not much left to the structural integrity.

      Bottom line, you get what you pay for. Hearing the dollars on NPR, it is amazing to me that companies were able to keep WWII vintage aircraft in the air for what they make.

      --
      When the people fear their government, there is tyranny; when the government fears the people, there is liberty.
    4. Re:Speed by Anonymous Coward · · Score: 5, Informative

      For years, commercial pilots had to essentially make the "low altitude drop in mountainous terrain" you are speaking of at Kai Tak in Hong Kong. The airport was essentially nestled up against a steep mountain, densely populated by tall apartment buildings and the ocean at the end of the runway. This called for some truly interesting descents and there were "incidents" on the runway but none major, if I recall, before the airport was eventually closed.

      Check out this photo:

      http://www.airliners.net/open.file/076911/M/

    5. Re:Speed by neodymium · · Score: 4, Informative

      a 747 in full flap configuration can be slowed down to 210kt (approx. 340km/h) IAS fully loaded, and close to 140kt (approx. 220km/h) IAS empty. the maneuverability is a little bit limited, i.e. bank angles over 25 are forbidden. no steep turns are possible, so it takes over 1 minute to do a 180 turn.

    6. Re:Speed by valiko · · Score: 3, Interesting

      Check this thread well... read the first reply in this thread. US forestries banned the use of IL-76 firefighter, which is twice smaller than 747, how would 747 be any different??? Il-76 payload is 11,000 gallons, pretty good too

    7. Re:Speed by joemc91 · · Score: 5, Informative

      A 747 can actually slow to around 120knots, about 140 mph. The standard approach speed for one of these behemoths is around 140-190 knots, depending on the weight. I don't think the proper question is "can the plane go slow enough?" but "can the plane maneuver at low-altitude among mountains?"

      Here's some more reading from a slightly more advanced aviation source: http://www.avweb.com/eletter/archives/avflash/238- full.html#187301

    8. Re:Speed by Jesrad · · Score: 4, Insightful

      Exactly, and I would rather have a C130 do that work instead of a 747. Hercules can fly half as fast as those big commercial jets when needed. One even landed on a carrier.

      --
      Maybe we deserve this world ?
    9. Re:Speed by steve_l · · Score: 4, Funny

      they are very disconcerting to encounter in the mountains. I was driving up in scotland when this hercules crawled overhead at about 100' - it is a lot harder to avoid reacting badly to the sight of something that looks about to land on you, than it is it deal with a fighter plane going above you at that height -they are usually gone before you have time to notice.

    10. Re:Speed by lunartik · · Score: 4, Informative

      Bombardier's 415 is an awesome plane and doesn't have the concern of decades-old surplus planes (remember that video from a couple years ago of a C-130 losing its wings during a drop?). From their site:
      It takes only 12 seconds, travelling at 130 km/h (70 knots) to scoop up the 6137-litre (1621-US gallon) water load. This requires an on-water distance of only 410 metres (1350 feet). The Bombardier 415 can scoop water from sites as shallow as 2 metres (6.5 feet) and 90 metres (300 feet) wide. This means that a great number of water sites can be used to reload its tanks. The aircraft doesn't need a completely straight scooping path. Since it's still in "flying" mode while scooping, the pilots can maneuver the Bombardier 415 around river bends or avoid visible obstacles in the water. As well, if the water site is too small for a full pick-up, the Bombardier 415 can take a partial load and return to the fire.

    11. Re:Speed by Analogy+Man · · Score: 5, Informative
      I used to work at Boeing in the performance group working out how to do this. The approaches and procedures are all worked out with margins for all obstacles and provisions for engine out, performance adjustments for temperature etc. In the case of Hong Kong it is at sea level so the performance is much better than it would be at 8000 ft somewhere in the Sierras or Rockies

      In the case of dropping on a fire, it is an ad hoc mission, the pilots would have to eyeball the situation and think on their feet. Also, suppose they count on being rid of 150,000 lbs of water before they need to do a climbing turn at the end of a valley and a hydraulic valve sticks? The only good news as that 25,000 gallons of water would help extinguish the 30,000 gallons of jet fuel.

      The wind conditions around a forest fire are also dangerous. Fires create their own weather.

      --
      When the people fear their government, there is tyranny; when the government fears the people, there is liberty.
  2. Refills? by MrIrwin · · Score: 4, Interesting
    I know one feature of firefighting planes such as the Canadair is the ability to refill by skimming the surface of a lake or the sea.

    Somehow I can't envisage this with a 747, and how many 747 sized airstrips do you find near forestry areas?

    --

    And if you thought that was boring you obviously havn't read my Journal ;-)

    1. Re:Refills? by CommandNotFound · · Score: 5, Informative

      But I thought 747's weren't particularly strong.

      They were strong enough to carry the shuttles around on its back. According to the specs, the 747-400ER has a maximum takoff weight of 910,000 lbs. A fully-loaded 18-wheeler dirt truck averages around 80,000 lbs, to put that into perspective. I don't see how it gets off the ground. 11 trucks are heavy.

    2. Re:Refills? by MrIrwin · · Score: 4, Informative
      It is about 12 times the capacity of a Canadair.

      But Canadair turnrounds can be as low as 15 mins between bombings, and that is also usefull for ground crews to provide feedback. I think little and often is a better strategy than big drop/big interval.

      BTW, the 747 not only needs a significant airstip, you have to get all that water on board and it has to come from somewhere!

      True, my knowledge of Canadairs comes from thier use in Italy, where you are never far from a lake or the sea, I can imagine some areas of the US may be different.

      --

      And if you thought that was boring you obviously havn't read my Journal ;-)

    3. Re:Refills? by twbecker · · Score: 5, Informative

      24000 gallons of water weighs 99.96 tons.

      Load capacity of a 747 is just over 116 tons.

      But yeah, that sure is a lot of weight. Amazing aircraft.

      --
      "The problem with internet quotations is that many are not genuine" -Abraham Lincoln
    4. Re:Refills? by general_re · · Score: 4, Informative
      How much does all that water weigh compared with what a 747 could carry?

      24,000 gallons of water weighs just shy of 200,000 pounds. A quick glance at the technical specs for the 747 says that the maximum payload capacity of a 747-400 cargo freighter is 244,000 pounds.

      --
      ABSURDITY, n.: A statement or belief manifestly inconsistent with one's own opinion.
    5. Re:Refills? by confused+one · · Score: 4, Insightful
      The plane has no problems staying in the air with one engine out. Even if they lost two, it would be a simple matter to dump their payload: It's only water.

      Some people might get a little wet... and appropriately ticked off; but, it's better to get suddenly drenched than to have a 747 crash land on your head.

    6. Re:Refills? by Rolo+Tomasi · · Score: 4, Interesting

      Beriev makes amphibious planes, some of which are designed for firefighting. The Be-200 has about 1/7th of the water capacity of the 747 mentioned in the article, but it can scoop up water during touch-and-go on a lake or river. It can also land on a lake or river to refuel (you'd just have to get a fuel truck near to where the fire is, and the plane could operate there all day). The 747 would have to fly to a big airport (needs a long runway), and this airport would have to be situated next to a body of water, or have some other kind of huge water reservoir. IMHO this looks highly impractical vs. an amphibian plane.

      --
      Did you know you can fertilize your lawn with used motor oil?
    7. Re:Refills? by confused+one · · Score: 3, Interesting
      As the water falls, it tends to break up into droplets (aka rain) due to aerodynamic forces. It would not stay in one large mass.

      The plane would have no way to dump it all at once. It would pump it out just as if it was dumping the water over a fire. Firefighters working a forest fire get dumped on ocassionally.

      You would get VERY wet; and, you might actually be swept away by a sudden rush of water (along the ground)... But, unless you fell and hit your head on something, you wouldn't be killed.

  3. There is of course the giant Russian water bomber by njh · · Score: 5, Interesting

    This "11,000-gallon tanker plane pours 'too much water,'". I guess 24,000 gallons (90000L) is not too much though...

  4. Re:Be sure to watch the videos. by lordsilence · · Score: 3, Funny

    Oh, don't worry about bandwidth.
    They deliver the videos to your doorstep!

  5. Our govs' been spending its money on coke, again! by t_allardyce · · Score: 3, Interesting

    After watching a programme last night on a (mockup) terrorist attack on london (about 2000 people died when a chlorine tanker was blown up) i want one of these for stopping chemical attacks! apparently we have 1 air-ambulance for the whole city and a fraction of the police have chemical/biological training and equipment and the tube staff have nothing except some training that said "get everyone out of the nearest exit as fast as you can" wow i think i might become an emergency training consultant, i could make millions!

    --
    This comment does not represent the views or opinions of the user.
  6. Re:How Slow by System.out.println() · · Score: 5, Funny

    Then again, in a flight simulator I've flown the 747 straight up so you could approach the burn and then climb hard while dropping the water.


    Do I even need to add anything to make you sound less credible? :)

  7. A few Problems.... by Graemee · · Score: 4, Insightful

    Cost - even the smaller water bomber's are expensive. Operating cost of a 747 would be even higher again.

    Accessability - a 747 doesn't operate from small dirt airfields or remote areas. I can see one of these trying to fly from a larger area to a remote area to drop water. (See costs)

    Speed - they'd be running a lot faster than most water bombers. I can here the STALL STALL warnings now.

    Accuracy - See Speed.

    They might be good for fast burning "California or OZ" fires but I not sure they would be much use for most medium size forest fires. IMHO

  8. What about a Airbus 380 tanker? Bio/Chem defense.. by tronicum · · Score: 3, Insightful
    Imaging building suchs a tanker from a Airbus 380 Specs

    Interesting is that it covers "7 times" of what a normal air tank covers. As amateur I would assume that it takes similar time to cover the burning area, it just takes makes re-fitting faster. It is probably harder to fly as whell.

    Beside that the chemical and biological "homeland" security aspect is ridiculous. You dont have such planes equipped in time fight such attacks.

  9. Firefighter for the Forest Service for 5 years by Anonymous Coward · · Score: 5, Interesting

    And here's the thing, once a fire gets to the size that you start thinking about dropping 24,000 gallons of water on it, YOU'VE ALREADY LOST! Water sure as hell ain't stopping it, unless it happens to be in the form of a severe rainstorm, and even then fires can burn underground for months. There were fires in Yellowstone that started in late fall, got snowed on, smolderd the entire winter underground and then reemerged the next spring.

    What the Forest Service needs to do, and to their credit seem to at least be aware of on the ground (at least from my personal experience), is have quick response helicopters that can get to fires before they have blown up (read, still under 100 acres, give or take). Once a fire gets much bigger than say 1000 acres, it starts to create its own weather - at this point, the effort becomes more one of 'figure out where the wind will push the fire and get the hell out of the way!'

    The only possible use I see for this plane, and one in which it is probably well-suited for, is in protecting man made structures from large, fast moving fires. Let's say there was a fire bearing down on Denver and threatening a rather pricey subdivision. This plane would be perfect for that job - they could load it up with fire retardant and create a huge 'wet line' in front of the subdivision. Maybe make a couple drops and you would be golden. My guess is that's what they have in mind, but I could be wrong.

    1. Re:Firefighter for the Forest Service for 5 years by Anonymous Coward · · Score: 3, Interesting

      From my personal experience, 50 acres (give or take of course) is about the threshold between a small manageable fire, and a larger, 'project' type fire. Maybe you've never been on a real fire before? I don't know. The 50 acre fires that I have been on have involved large numbers of engine, multiple helicopters, and lots of support personell, not to mention the people digging line and dropping trees. Get to 1,000 acres and you can EASILY justify calling in smokejumpers or a shot team from NIFC. When I was working (late 90's), the going rate for a jumper team was about $1 million per DAY! If you call that an EASY fire, more power to you chief!

      50 acres of fire is a site to behold, 1,000 acres would blow most people's minds.

      The largest I have seen in person is about 75,000 acres. The fire was whipping up fire tornados, trees were blowing up left and right (literally exploding) and flame lengths were close to 100 vertical feet. There is little, if anything people can do to fight fires like this directly. The best bet in such situations is to dig a huge fire break with dozers way in front of the fire, and maybe lay down wet line with the help of large air tankers (such as the 747 mentioned in the article). If you're lucky the weather will cooperate and the fire will eventually burn itself out. I wouldn't consider this 'putting it out' so much as 'averting further destruction.'

      Anyway, I'm in cube farm land now, so about all I can do is relive the glory days. Maybe those still involved can speak directly to the issue, but chances are they are the lucky ones without internet access ;-)

  10. Re:There is of course the giant Russian water bomb by Analogy+Man · · Score: 5, Interesting

    One thing the Russians are good at is making things tough. Their design philosophy on military aircraft (including their fighters) is to make them robust to hostile environments including unimproved runways etc. On the surface this looks like a far more economical model using either the Russian or Canadian equipment than to retrofit some used up aircraft not designed for anything like this mission.

    --
    When the people fear their government, there is tyranny; when the government fears the people, there is liberty.
  11. Re:How Slow by mumblestheclown · · Score: 5, Informative
    You know, I've been studying 747-400 systems for the last few months in preparation for some work i am going to do (I am an experienced pilot).

    "flown the 747 straight up" sounds about as dumb to a pilot as those tech support calls that ask what the cupholder is for to a computer company.

    Now, I can't speak for the -200, but as far as the -400 goes, if you fly the 747 straight up in real life, you will in all probability die.

  12. Converstion inside the cockpit: by Molina+the+Bofh · · Score: 4, Funny

    Jeff, you moron ! That was not the water release button !! That was the emergency fuel dump button !

    --

    -
    Roses are #FF0000, Violets are #0000FF, find / -name '*base*' |xargs chown -R us && mv zig greatjustice
  13. Re:Too Heavy? by blancolioni · · Score: 5, Funny

    Hi Tom. I'm going to go out on a limb here, and guess that the 747 won't be completely full of water. I know what you're thinking -- that's crazy talk! But I have this funny feeling that just won't go away: maybe the people who think of this stuff have better things to do than make up stupid shit that doesn't work.

    I'm just guessing, of course. It's quite possible that the plan involves filling a 747 up with water and watch it sit on the tarmac. That could also be fun.

  14. Use the right tool for the job by EulerX07 · · Score: 4, Interesting

    Bombardier CL415

    Check the description and FAQ here.

    Retrofitting a 747 for firefighting? Why not buy a plane designed from the ground off for firefighting purposes? It can drop 32000 to 65000 gallons of water between refueling. In real life situation it has proven to be able to deliver up to 30 000 gallons per hour.

    Ever since I was a kid I'd seen videos of CL215 (the predecessor) fighting the big forest fires, and I was always wondering why the US used small choppers carrying minuscule payloads of water to fight the fires. Can anyone clear this up?

  15. From someone who knows by Anonymous Coward · · Score: 5, Informative
    (This is a post from a pilot forum by a tanker pilot with considerable experience.)

    All tanker delivery systems in use today, except the MAFFs systems (modular airborne firefighting system; military) are capable of multiple drops, split loads, and variable coverage level on every drop. It's part of the basic requirement to field a tank system for use over the fire.

    The Evergreen project is being tested at Marana (AZ) now through the middle of next month.

    I believe it holds a certain amount of promise, but also some challenges. Like every asset over the fire, it has advantages and drawbacks.

    The delivery system is reported to use water injection ahead of the retardant stream to break up the airflow; a fairly complex and weighty soloution to an otherwise simple problem.

    The aircraft is swept wing, which presents certain difficulties at low speeds in the fire environment. The concept is of a tanker that makes high retardant or water drops, rather than using it for directly fighting fire. The aircraft will be very limited in the fields from which it can operate, restricting it from being useable at most tanker bases. It also means the airplane will have to make longer ferry's to get to fires, which will give it longer turn around times, greater costs, and may negate any advantages to carrying a greater retardant payload.

    Large burning objects fly around over a fire, including trees or parts of trees. A turbofan engine is subject fo FOD contamination by smoke on the compressor blades, but also to direct strike damage from objects over the fire. It is also subject to flame-out, a greater liklihood than a piston engine that has continuous ignition

    Drops are typically best done slow; the faster the tanker is moving, the higher the drop needs to be in order to allow the retardant to stop it's forward motion and fall straight down. Retardant moving forward on contact with the fuels only coats one side, an effect known as 'shadowing.' This leaves one side of the fuel unprotected, and negates the value of dropping the retardant.

    A fast tanker may need to drop so high that the benifits of the retardant drop are muted. The higher the drop, the greater the drift isue, meaning reduced accuracy, and consequently reduced usefulness.

    A DC-4 can be supported by the flight crew; often mechanics who can work on the aircraft as well as fly it. Often a single additional mechanic is a luxury, or all that is necessary to keep the airplane flying. Not the case with a B747.

    Maneuverability close to the fire, in terrain with severe or extreme turbulence and reduced visibility may present a number of unique problems for the B747.

    If it's viable, the B747 concept (and the DC-10 being fielded by Omni) will present a useful and valueable tool over the fire. It's just one tool, however, and not a soloution of a panacea for other problems plaguing the industry right now. Each aircraft over the fire, heavy fixed wing, single engine fixed wing, light helicopters, heavy helicopters, lead aircraft, air attacks, jump ships, etc, all have important roles. No one aircraft can or should perform them all. Additional available resources such as a B747 only mean that additional tools are available from which to choose when deciding how to most effectively fight a fire.

    I fully support any developmental effort to enhance the industry. I tend to take a wait-and-see attitude; these aircraft were never intended to enter or operate in an environment such as the fire ground. Only time will tell what the success of these projects will be.

  16. Re:There is of course the giant Russian water bomb by sharrestom · · Score: 5, Informative

    Back in the 80's, I worked 3 summers as a Smokejumper for the BLM out of Fairbanks, Alaska, and was detailed to the lower 48 on 2 occasions. Smokejumpers and air tanker are considered initial attack resources, so, getting to the fire while it was small and containable was the primary mission. Personally, I find that the aging A-10 aircraft would be more practical than the 747, as it can be forward positioned to the existing air tanker support facilities (Minden, NV being nearest to my neck of the woods/desert), and is fast and exceptionally maneuverable, a requirement for the mountainous terrain of much of the west.

  17. Re:There is of course the giant Russian water bomb by EinarH · · Score: 4, Interesting
    A very interesting article indeed, I read something similar on USENET but this one is more extensive. As somone said; it's all about two things:
    1. The NIH, Not Invented Here-syndrome and
    2. Money.
    In addition to his work for BLM, Lamun heads the Interagency Airtanker Board that represents air tanker contractors and federal firefighting agencies. It is responsible for setting criteria for air tankers and overseeing the certification process.
    Am I the only one that can see a clear conflict of interest situation in this case? The same guy in both a "criteria role" and as representative for contractors (both private and federal)...

    Ten bucks that The Forest Service will abandon it's "too much water" policy when a US-company comes up with a US-built plane doing the exact same thing as these Ilyushins. And that despite the advantages of the Ilyushins like better maneuverability, reduced cost and shorter takeoff.

    --

    Melius mori in libertate quam vivere in servitute.

  18. Wow, there's a lot of misinformation out there... by coyote_oww · · Score: 3, Informative
    Here's a little more general information about the industry For those who are too lazy to click, existing airtankers apparently run from 800-3000 gallons.

    AVWeb ran an article about "heavy airtankers" - used ex-Airforce/Navy C-130 and P-3s pressed into service as tankers. From this, we get a weight of 9.3lb/gallon for retardant, for those interested. For our 747, this would be 223,200lb, or 111.6 tons. The most interesting part of this paper is where they talk about the fatigue resulting from the rapid unloading of the aircraft. Apparently, this is the main cause of catastrophic wing failure. When you suddenly change the aircraft load by 15-20%, you get a definite bending action in the wings. Just like bending a paperclip, eventually this leads to failure.

    The paper also briefly mentions the super-tanker idea (747 or DC10 based).

    The other big concern is that the economic payback for larger aircraft is longer than for smaller aircraft. They were talking about the proposition being questionable with an $8 million acquistion cost. I don't think you could get an operation 747 for anything close to that...

    I've heard of proposals like this before. For a while there, the FUSSR was trying to get interest up in Western countries to buy/lease IL-76's for similar duty. FUSSR aircraft might make more sense, they are notoriously inexpensive.

  19. One of the old ones went down near my cabin by ianscot · · Score: 4, Informative
    A couple of years back, one of the old WWII-era planes that just got grounded crashed on Highway 36 east of Estes Park, Colorado. We're a couple of miles off the other highway into Estes Park, up a mountain, and between the fire and the crash we had to take a different route home that year.

    What happened in that 2002 crash was, one of the wings of the plane just sheared off in flight as it came out of a turn. It was structural fatigue, as this article says. The plane involved was just under 60 years old, IIRC.

    The pilots got profiled in the papers. Impressive people. Most pilots are flying for the love of it, they get paid next-to-nothing even for the airlines until they have tons of seniority, but these guys were what you'd call heroic characters.

    They're truly old planes; it was like seeing a B-24 Liberator at an airshow, only instead of being carefully eased along in their dotage they were still hauling massive loads of water at low altitudes and speed, flying risky in the mountains in this case, for decades after the war. Pretty hard use.

    --
    "Fundamentalism" isn't about divine morality. It's about human authority.
  20. Re:Popular Science by ericspinder · · Score: 3, Interesting

    I love Popular Science as well, but almost all of their "forward-looking" inventions are vaporware. Sometimes, I think, their qualification for story submission is a good color drawing of the "product" and lots of hype about how the worlds going to change because of it in 2 to 6 years. For how many years now have they been saying "flying cars are right around the corner". I am not saying that they are always wrong (or every fraudulent), their coverage on new products and (working) prototypes is good, but just don't count on anything that needs an "artist rendering", like the fire-fighting plane you (apparently) saw in that mag.

    --
    The grass is only greener, if you don't take care of your own lawn.
  21. I've had these things fly over my house by Wacky_Wookie · · Score: 4, Informative
    I used to live on Vancouver Island, Canada. We get one or two big fires every year and these planes are called in when things get hairy.

    During a fire a few years back, the pilots were using are road as ref. point for heading back to the fire after scooping up a new load of water. These things were passing over our house not more then 100 ft from the top of our roof. With a full load of water then engines make one hell of a noise.

    Vancouver Island is home to two other interesting fire fighting planes: The Mars Water Bombers.

    The Mars planes fight fires in the US all the time since they are privetly owned.

  22. Loosing weight ... by wwwillem · · Score: 3, Insightful

    Besides all the discussions about flying a 747 at very low speed and about the manouvrability at low altitude, what happens to the plane when in a few seconds it becomes 100 tons lighter? Don't know the ratio between the empty and full weight of the plane, but loosing weight that fast doesn't seem to be a situation when I would like to be a pilot. And definitely not one when you are low speed, low altitude.

    --
    Browsers shouldn't have a back button!! It's all about going forward...
  23. It's not the DROP that causes fatigue by Goldenhawk · · Score: 5, Informative
    Yes, I am an aerospace engineer.

    It's the turbulence that causes fatigue, not the action of unloading a lot of water at once. If you think about it, when you go flying in an airliner and you hit a bumpy patch of air, it's usually around clouds. The reason clouds usually form is that air (moist air) is rising, and carrying the water vapor up to a height where the temperature drops enough for the water to condense. The point is, the air is RISING. As the plane flies thru this rising air, the direction the wing is encountering the airflow suddenly changes slightly. Not a lot, but enough that the lift on the wings suddenly increases. The lift (the force that holds the plane up) is a function of angle of the airflow to the wing, as well as airspeed squared. So when you increase the angle of airflow, the lift increases. Now you have more lift than weight, so the plane bumps upwards. But the area of rising air is relatively small, so you get a short transient bump.

    Over a fire, you've got LOTS of bumpy air - the fire is superheating patches of air, and it's all bumpy and roiling around. All that mess is rising rapidly into the sky, and fresh cold air is rushing in around the edges (remember Backdraft, the movie?), moving downward.

    To be an effective air drop platform, you need to fly very low, so that the water doesn't disperse too much before it hits the target zone. So you're deliberately flying an airplane thru extremely unstable (rapidly rising and falling) patches of air, with very large vertical speeds (which means, larger changes in airflow direction, which means more severe turbulence).

    As any materials engineer knows, and as most of us geeks know, if you bend something often enough, it breaks. And the further you bend it each time, the faster it breaks. An airplane wing is designed for a certain "fatigue life" - a certain number of cycles of bending. With the above primer on turbulence, you can imagine how drastically different from the design you will be using the airplane when you fly it 500 ft over a forest fire, compared to relatively smooth air at 38,000 ft.

    So watch the amazing video from last year of a C130 losing its wings over a fire - it's a natural but hopefully rare consequence of abusing an airplane this way. The way the airplane owner SHOULD handle this is frequent and intensive inspections. That C130, as I recall, was NOT properly inspected and was well past its service life. You can read the NTSB report on that accident at http://www.ntsb.gov/Recs/letters/2004/A04_29_33.pd f (PDF file). A particularly telling quote: "The rate that maneuver load factors between 2.0 and 2.4 were experienced by firefighting aircraft was almost 1,000 times that for aircraft flown as commercial transports." (Load factor is engineer-speak for "g-force" - 1g is normal gravity; most transports never exceed 1.4g except in severe turbulence.)

    --
    --Brandon / Split Infinity Music

  24. Re:There is of course the giant Russian water bomb by dj51d · · Score: 3, Interesting

    I couldn't agree with you more, however, the US seems to suffer from a major case of Not Invented Here Syndrome. At one point in time, the Alaskan legislature appropriated funds to purchase two Canadair fire bombers, and the state's top fire fighting official wouldn't let the purchase go through, claiming they would do no good in Alaska. Some progress is being made, Hawkins and Powers, one of the major contractors is in negotiations to buy several of the Russian Be-200's. The problem is, the US Forest Service has stated they won't contract Be-200's because they don't have a US Type Certificate. Oh, BTW, I'm from Minnesota, one of the two states that has realized the value of a purpose-built fire bomber(North Carolina being the other has a single Canadair CL-215), we have 2 Canadair CL-215's protecting our property and forests.

  25. Density Altitude by eutychus_awakes · · Score: 3, Informative

    Forest fires typically occur in mountains. Mountains are usually between 1,000 feet and 13,000 feet tall (300 - 4000 meters). Forest fires usually occur in the summertime. Forest fires make a lot of hot, dry air. The net result of this is a substantial increase in the density altitude in the region around a forest fire.

    The density altitude is the altitude the airplane "sees" - taking into account air density, temperature, humidity, etc. Above a 5,000ft density altitude (~1,500m), most airplanes have a hard time just taking off with a full fuel load, much less performing high-g maneuvers close to the ground. At Las Cruces, New Mexico, the airport here is at about 4,500ft (1,370m) mean airfield elevation. Density altitudes above 7,000 feet (2,130m) are not uncommon - even early in the morning.

    To operate under these conditions, pilots simply reduce their passenger and fuel loads. I haven't done the math, but I suspect that to make a 747 light enough to operate safely "down low" at a high density altitude, it wouldn't be able to carry much more water than the C-130 tankers we already use. Plus, a loaded 747 would tend to perform like an elephant on ice skates - a consequence of its swept wing and turbine engines - which don't "spool up" as fast as props. There would be zero margin for error.

    --
    This sig is a test. If this had been an actual sig, you would be reading something quite a bit wittier than this now.
  26. Re:Be sure to watch the videos. by pixelpusher220 · · Score: 3, Funny

    Um...after the /. crowd comes a knockin'....

    All their server will be good for *IS* a doorstep!

    --
    People in cars cause accidents....accidents in cars cause people :-D
  27. Los B52s by n9fzx · · Score: 3, Insightful

    Rather than cutting them up, why not cut a deal with the Russians and keep a few B52H bombers in water tanker service? With the appropriate firefighting gear in the bomb bay, it would be difficult if not impossible to revert back to a bomber; heck, give the Russians the contract for the firefighting mods.

    After all, the BUFF has a proven track record of being stressed properly for low-altitude flight; there are plenty of retired USAF pilots and navigators out there who have 1000+ Time-in-Type, as well as mechanics, spare parts, etc.

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    ...-.-
  28. Some things just aren't meant to be. by Uberbot · · Score: 3, Insightful
    Airplanes just weren't meant to carry water.

    Try this gedanken experiment: Fill a bucket about half full of water. Now grab the bucket with both hands and run down the street. Once you get up to speed, try to stop or turn quickly without spilling any water. In fact, try to do it without letting the weight shift inside the bucket.

    You see, as soon as you try to quickly change speed or direction, the weight shifts. When 24,000 gallons of water shifts, you have a lead sinker on your hands.

    Watch the videos of those planes crashing. That is exactly what it looks like happened. The pilot tried to pull up, but the water shifted, and the plane lost it's wings under the intense weight shift.

    This reminds me of a friend in highschool who's dream car was a hearse with a waterbed in the back. Sounds like a good idea untill you try to turn a corner at any speed greather than 5 mph!

    By the way, Shane, if you are reading this, contact me.