Modified McDonnell Douglas DC-10: A look at 10 tanker’s aerial firefighting airplane

USA – These trijets fight hundreds of fires across the world each year.

When fighting forest fires, dropping enough water or fire suppressants from above can be one of the most impactful solutions. That’s why massive jets that previously flew commercially, such as the McDonnell Douglas DC-10, have been modified to become aerial firefighters. Since 2006, aerial firefighting firm 10 Tanker and its fleet of DC-10s have operated missions responding to wildfires worldwide.

Humble beginnings

The aerial firefighting organization, 10 Tanker, was established in 2006 and has been fighting fire for almost 18 years. This Albuquerque, New Mexico-based company started operations with a single particular modified McDonnell Douglas DC-10 aircraft registered N17085 (officially delivered on December 1, 2007) and has since taken delivery of three more for a total fleet of four.

Although the DC-10 is the newest generation of large aircraft used for aerial firefighting, early aerial firefighting aircraft were surplus military planes repurposed for peacetime. These types were modified to carry water and chemical flame retardants, operating for decades. However, a fatal crash in 2002 led to the grounding of these jets, and companies needed new jets to assist with aerial firefighting.

Then 10 Tanker emerged onto the aerial firefighting scene, operating a DC-10, making it the first company to use turbine-powered jets to fight fires. Since its founding, 10 Tanker’s DC-10 jets have played a pivotal role in fighting fires in the United States and abroad.

Today, it is one of the only companies to operate newly developed very large air tankers (VLATs) and responds to hundreds of wildfires while delivering millions of gallons of retardant. As such, the company is contracted by the United States Forestry Service through the United States National Interagency Coordination Center in addition to state government agencies such as the California Department of Forestry and Fire Protection, also known as CAL FIRE.

These DC-10 jets are based in the United States during the fire season, which generally lasts from spring to fall or from April through October, where they are contracted to by the government. Then, in the other months, the DC-10s are based in the Southern Hemisphere, as the company is employed by countries such as Australia and Chile to assist during their fire season.

Inside the jet

10 Tanker’s DC-10s are some of the most efficient and advanced air tankers operating. The aircraft are modified by removing the center gear to feature a gravity feed tank system carrying up to 11,600 gallons of water or fire retardant known as Phos-Chek. The system comprises three aptly-named tanks: 1, 2, and 3, which hold 2,700, 4,000, and 2,700 gallons, respectively. According to 10 Tanker, these aircraft can deliver the full 9,400 gallons of fire retardant or water within 8 seconds and up to a mile long.

In 2018, the delivery computer on the DC-10s was upgraded to feature a gang drop where all the tanks are released simultaneously. The jets are programmed to perform sequence drops, where one retardant drop overlaps with the following, and split drops, where one part of the retardant is released in one area of the fire, and the other part of the retardant is released in a different part of the fire. Each drop is based on the drop requirements and coverage levels.

These aerial firefighting planes are operated by two pilots and one flight engineer responsible for monitoring the systems and inputting the drops. The aircraft is accompanied by multiple maintenance technicians who travel with a trailer full of spare parts and equipment needed to operate the DC-10, ranging from tires to brakes. Although the average duty day for pilots is nine hours, they can fly for up to 14 hours, depending on the situation. Each mission is around an hour of flight time. Once the plane empties its supply of fire retardant, it returns and is reloaded, which takes 15 to 20 minutes before heading back out again. When dropping the retardant, the DC-10 flies between 200 and 300 feet above ground at 161 miles per hour or 140 knots.

Why the DC-10

The DC-10 is an excellent aircraft for aerial firefighting as the tanks at the bottom of the jet enable it to carry three times as much retardant as other large air tankers. This allows the crews to do three times the amount of work at the exact cost, equating to a cost-effective and efficient operation. Additionally, the tanks of the DC-10 are capable of dropping fire retardant in a straight line ranging from a quarter-mile up to a mile.

Another feature of the DC-10 is that it can fly downhill, so it can drop retardant in areas other planes can’t reach, such as the sides of mountains. The three powerful General Electric CF6-50C2 engines allow it to drop downhill and still have enough power to fly back uphill.

These DC-10 firefighters have responded to hundreds of wildfires over the years, creating vast fire containment areas in less time and saving lives and wildlife. According to 10 Tanker, during the United States fire season in 2023, they have flown 405 firefighting missions, dropping 3,678,003 gallons as of October 23, 2023. In 2022, 10 Tanker repainted its fleet of DC-10s in a new livery ahead of the upcoming firefighting season.