Why can't helicopters or Zeppelins drop fire-fighting material on burning buildings?

Question

There have been a number of tragic cases where tall buildings have caught fire for various reasons, and fire-fighters on the ground appear to have been unable to reach the upper stories with fire hoses.

As a child watching 9/11 unfold, I remember wondering why, given that helicopters were being used to film the events, it would not be possible for helicopters, or perhaps airships, to be loaded with water or foam and fly over burning buildings, dousing them.

Of course, in retrospect, I understand that the World Trade Centre buildings were so vast and the fire (and structural damage) so enormous that this would have made little practical difference. But what about cases of relatively smaller tower blocks, such as the recent tragedy in the Grenfell block in London?

I assume that there must be some practical reason why this cannot be done, on the grounds that this is something which presumably would be being done if it were possible.

Is it simply that the weight of a large amount of water would be too heavy for a helicopter to carry? Would this apply to airships?

Answer 1

First, they have been used, like in case of the Federation tower fire in Moscow on 2012. The image below shows a Kamov Ka-32A11BC being used to fight fire in that case.

^{Helicopter fighting Federation Tower fire in Moscow; image from dailymail.co.uk}

According to a news article

The Ka-32A11BC proved its fire-fighting credentials in April 2012, when a blaze engulfed ... the 67th floor at the Federation Tower in Moscow, Russia, more than 270 meters above ground level. ... the fire was only contained after two Ka-32As belonging to the Russian Emergencies Ministry were called into action and ferried in water from the nearby Moscow River.

However, there are multiple issues in using helicopters for urban firefighting.

• Helicopters are all but powerless is case of fires breaking out over the lower floors. Even in the above case, the helicopters were useful only as the fire broke out in the top floor of the (then under construction) skyscraper. For lower floors, the helicopter would have to carry the spraying equipment in the fuselage, which would make the useful payload impractical. Airships are all but useless in this case, while even helicopters would have difficulty getting through the buildings.

• Firefighting using helicopters is not a precision business as it would be difficult to position the helicopters directly overhead due to the intense heat and the turbulence produced. For safety, the helicopters have to fly higher, which reduces efficiency due to winds.

• Aerial firefighting is a costly business. As LA times puts it:

  It costs up to \$14,000 a day to keep an air tanker on call and as much as \$4,200 per hour to put it in the air. Heavy-duty helicopters, the workhorses of aerial firefighting, can cost \$32,000 a day on standby, plus \$6,300 per hour of flight time.

  and this in the US where the need to put out forest fires is all but certain. Major fires in skyscrapers are infrequent and too scattered around the world to justify the expense of keeping a helicopter on standby in any given city.

• The crew have to trained for this- firefighting is a dangerous business:

  But unpredictable atmospheric conditions make flying over wildfires difficult and dangerous. Thirty-seven firefighters have died in aerial firefighting accidents in the last decade.

  Urban environment with high rise buildings and power lines pose a separate set of challenges.

• Water and firefighting slurry supplies have to made available- this is important in cases where for example, the rivers are seasonal. Not only is the normally used firefighting slurry costly, it is also not environment friendly.

  ... the slurry, which is rich in nitrogen, can harm fish, wildlife and watersheds, despite agency guidelines to prevent drops onto vulnerable areas.

  Aerial firefighting is expensive. Tankers cost upwards of \$6,000 per hour to operate. The slurry itself averages about \$2 per gallon, and the Forest Service used almost 9 million gallons of it last year.

Airships have the same issues, and some more (payload and speed/maneuverability come into mind).

Answer 2

Fire creates heat, which in turn creates turbulence. While soaring enthusiasts welcome this as thermals, lighter-than-air captains dread such turbulence as their worst enemy. When the airship enters such a warm updraft, first the nose is lifted, and then the whole ship. At the same time, the airship starts to drop within that hot, rising air column, because now the density of the outside air is reduced, reducing buoyancy. The ship will be tossed around and be very hard to control.

Dropping a large load at the same time makes matters worse. Now the ship has excessive lift and will accelerate upwards like a cork in water. If that upward movement cannot be stopped before the bounce height of the ship is reached, the gas bags will burst.

No, airships are completely unusable to fight fires.

Helicopters, on the other hand, make excellent precision firefighters. They can carry a limited load but place this with much higher precision than airplanes. Airplanes have an advantage in cost per ton of water and when the source of that water is some distance away.

_{Kamov helicopter dropping water (picture source)}

In all cases, water would only be dropped from above, like rain, and buildings are designed to prevent rain from entering. Therefore, unless the roof structure is ablaze, this water would not reach the burning structure. With current technology, fires on higher floors of tall buildings can only be extinguished with a pre-installed sprinkler system or firefighters using water from pre-installed standpipes and hoses. Optimistic scenarios of helicopters shooting jets of water horizontally into a burning high-rise building have not materialized because the reaction force from shooting that jet of water would make the helicopter hard to control.

Answer 3

The most extensive use of helicopters for firefighting (and sealing a reactor) was Chernobyl. The Helicopters of Chernobyl In fact, nothing but a helicopter could possibly have performed the partial sealing of the exposed reactor, preventing a far worse release of radiation.

Sadly, the crews of those helicopters who responded immediately, died from radiation exposure not long after the initial disaster. The very radioactive helicopters were quarantined in a field for decades, until they were eventually destroyed to stop looting of parts.

Large airships... are just too vulnerable to extreme weather to be considered a reliable tool. While everyone remembers the fire of the Hindenburg, the only non wartime loss of an airship to a hydrogen fire, few remember the large dirigibles lost to storms: three notable examples are the USS Akron, USS Macon, and the British R101.

Answer 4

Helicopter firefighters do exist, and are used here in Australia for extinguishing bushfires. Elvis is here on a regular basis.

Bushfires just require to plonk a load of water on top of the burning area (just, as in doing a heroic job flying above a roaring fire) - spraying a water jet sideways from a heli would be more complicated but could probably be done, the dynamics would be analogous to those of a cannon on an attack helicopter. Airships might work yeah, the helium filled ones, if only they wouldn't blow away.

Image source

It probably boils down to a question of economics. This document lists the number of fires in tall buildings, and mentions that built-in fire suppression systems are effective. The Twin Towers was a highly visible event, but how many tall building fires are there per year in NY City, and would that justify having a highly specialised team of helicopters availabe, with the pumping equipment and amount of water on board to squirt sideways into mid building?

Helicopters don't have much speed and range and each big city with skyscrapers would have to maintain a fleet. There are 12 fires in tall buildings listed for New York City in the last 100 years in Wikipedia. It would be conceivable to seek cooperation with the Army to use attack helicopters and exchange cannon & ammunition for a water cannon & water payload - the highly trained expert pilots would do a grand job at this.

Answer 5

Special airplanes and specially equipped helicopters ARE used to fight fires, mainly forest fires.

In parts of Europe, where I live, the name "Canadair" was synonym with the special firefighting planes, such as Canadair CL-215 and Canadair CL-415. Through my youth I was convinced that Canadair manufactures only firefighting planes, and only later I found out that they make passenger planes as well.

So the answer to that part is, they are used.

As to why they are (mostly) not used in urban environments, the answer is, there are better ways to prevent and fight fires in urban environments, so the need for a firefighting aircraft in urban areas is very infrequent. In properly maintained urban buildings you have fire alarms, sprinklers, and good access for the fire engines - while in the remote forests you have no such things.

Forest fires in southern Europe are quite regular and predictable occasion (due to tourists/visitors, sparks from the railways, etc.) so you can be sure that the fleet of firefighting aircraft in any country will be engaged for large part of the summer (and when not in use, they will be sent to help to their neighboring countries to help).

As people already explained, maintenance of these aircraft is costly and you cannot expect them to be sitting ready on the tarmac in London (for example) for 10 years without any engagement, until a fire breaks out in the building that was refurbished with flammable materials in what it seems now a criminal negligence. They also need time to be loaded with water (and perhaps chemicals, depending on the nature of the fire). When fighting fires in the wild (forests) they are never used alone (or even as first response), but always in combination with firefighters on the ground, if the terrain is difficult to access.

So, sadly, while a fully loaded Canadair CL-415 sitting on the tarmac with pilots ready for action 24/7 would perhaps help in Grenfell tower fire, having such aircraft ready 24/7 in urban environments simply does not pay off. And if it would not have been ready 24/7 it could not make any difference, since with Grenfell, the building was engulfed with flames within half an hour, if I remember correctly.

Of course, the issue of flying low in the city during the night over the fire also poses far greater risk than flying over a remote burning forest with accurately mapped topography (elevation).

Answer 6

First, the fire is inside the building, and dumping water on the outside of the building and roof wouldn't help. Second, the upper part of the building being burned is very likely to fall down. The pulling of fire-fighting material may make it worse.