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When there are forest fires or other large-scale fires, they’ll bring in planes to help put them out as quickly as possible. But what do planes really drop on fires?

To aid in putting on wildfires, planes will drop hundreds to thousands of gallons of water or other chemicals on and around the fires. Most often, planes will drop a specially designed fire retardant called Phos-Chek, a mixture of mainly water and fertilizer, to help contain the spread of a fire.

If you’ve ever seen an airplane help put out a fire, you might be wondering what the stuff is that they’re dropping from the plane. Is it just water? Why is it red? Don’t worry, we’ve got you covered. In this article, you’ll learn everything you want to know about flame retardant, how it works, what kinds of planes are used, and how the chemicals affect the environment.

To make sure that we’re only putting the best content we can out there, we spend hours researching every topic we post about. In addition to all that research, we include our own personal experiences with the knowledge from other pilots around the country. This way, you get the most accurate information on the web. Including everything there is to know about what planes drop on fires!

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What Is The Red Stuff That Planes Drop On Fires?

Maybe you’ve seen it in person (especially if you live in California!), or maybe you’ve just seen it on TV. But while wildfires are raging, you’ll often see an airplane drop a  massive cloud of liquid on the fire. Most of the time it’s red, but sometimes it’s clear and looks just like water. Like many others who aren’t sure what they’re seeing, you might be wondering: what is that stuff?

Most of the time, the planes are dropping a fire retardant substance known as Phos-Chek. Composed of roughly 88% water, 10% fertilizer, and 2% other chemicals, this substance was specially designed to help contain the spread of fires. Notices that I didn’t say put fires out, but rather to contain the spread.

This is because the planes actually aren't what's really going to put the fires out in the end. Sure, the water-based substance does help to douse the fire to a certain degree. And if the planes dropped regular water on the fires it might help to put them out. But the crews on the ground are really who’s going to put out the fire. The planes and fire retardant are there to assist.

How Effective Is Fire Retardant?

Flame retardant is very effective at doing what it’s designed to do — help to contain the spread of wildfires. The issue with wildfires is that they can grow out of control very quickly, so aerial firefighting is done to help create a blockade of flame retardant in the fire’s path, blocking it from growing and spreading out of control.

The combination of water, fertilizer, and other chemicals help the substances to leave a coating on the plants and trees (and everything else it touches) to help prevent the fire from spreading. This is because since everything is coated, it makes it more difficult for the trees and plants to catch fire. Thus giving the firefighters and round crews more time to get there and put it out.

The red coloration that you see in the mixture is added on purpose to make it easy to see where the retardant has already been dropped. The most effective way to use the retardant is to be able to cover as much of the vegetation as possible in the fire’s path so that the fire hits the wall of retardant and cannot go any further.

But what about the potential effects on the environment that gets covered in flame retardant?

What Happens To The Trees And Plants That Get Covered In Flame Retardant?

Even though Phos-Chek is much less toxic than flame retardants of the past (such as Borate), it still is not something that’s exactly great for the flora and fauna below. In the case of animals, most of them run away and escape the area due to the fire long before the substance is dropped, so very few animals have to deal with any repercussions.

One type of animal that can’t escape, however, is fish. And since fertilizer — which is basically what Phos-Chek is — is something that can contaminate waters and be toxic to the fish, pilots are directed to avoid bodies of water as much as possible. While this isn’t always possible due to the large amounts of retardant that gets dropped at once, pilots do their best to navigate away from any bodies of water.

Similarly, pilots are also directed to avoid landscapes with known plants that are endangered, since the substance has the potential to kill them off. That said, Phos-Chek was partially designed using fertilizer to help regrow the area after the fire is extinguished. The fertilizer will, well, fertilize the area and encourage new plant growth in the aftermath of a wildfire.

For most plants and trees that are doused with the substance, it will naturally go away with rain and time without causing any lasting damage. Scientists have not yet perfected a totally harmless flame retardant that can be released in high volumes like this, but it’s better than the alternative of just letting the fires burn!

Do Planes Drop Water On Fires?

Think about other fires besides wildfires for a minute. If a house catches fire or a building, for example, the fire department will show up with their trucks and spray it with water, right? So how come they don’t just drop water on wildfires to put them out like any other type of fire? Or do they?

In fact, they do! The US Forest Service (who’s typically in charge of putting out wildfires) does use both water drops and fire retardant drops. It mostly depends on what type of aircraft they have on tap, what condition the fire and the surrounding areas are in, and how the fire is responding to the current methods of putting it out.

In most cases, fire retardant is used instead of water because they’re trying to contain the fire rather than extinguish it. And fire retardant is much better at containing a fire and stopping the spread of it than just pure water is. This is because in most cases, the firefighters, bulldozers, and crews on the ground are actually the ones putting the fires out. Not the planes!

But the fact is that some planes are designed to drop water on fires directly to help put them out.

What Kinds Of Planes Are Used For Firefighting?

Now that you have a better idea of the actual substances (retardant and water) that are dropped by planes to help contain fires, you might be wondering what types of planes are used. Can any plane be used? Do they have to be specially-designed planes that can operate in rugged terrain like bush planes, or just modified to carry and drop the flame retardant?

Thankfully, the US Forest Service makes this a super easy question to answer because they actually post information about the types of planes that are used to help with firefighting. According to the US Forest Service, here are the planes currently being used:

  • Single Engine Airtankers (SEAT) — These are the most basic of planes used to fight fires. Single engine aircraft that have been modified to drop fire retardant, capable of delivering around 800 gallons at a time.
  • Large Airtankers  — The Forest Service isn’t exactly clever with the naming scheme, and the planes in this class can deliver 2,000 to 4,000 gallons of water or fire retardant at a time.
  • Very Large Airtankers (VLAT) — The biggest of the retardant-carrying airplanes, VLATs can carry more than 8,000 gallons of flame retardant to help contain the spread of the most intrusive of fires.
  • Water Scoopers — A unique airplane, water scoopers are designed to do exactly what it sounds like, scoop up water. These planes can be flown right along the surface of a body of water to pick up water and deliver it to the wildfire to help extinguish the flame.
  • Smokejumper Airplanes — Unlike the other planes mentioned here so far, smokejumper aircraft don’t deliver flame retardant or water. Instead, they are used to deliver smokejumpers, or field personnel that are dropped into action to join (or start) the fight against the fire from the ground.
  • Unmanned Aircraft — A relatively new addition to the US Forest Service’s lineup, it’s hoped that unmanned aircraft will help keep more people away from the fires, safe from harm, while still providing the abilities needed to help contain or put out wildfires.