Grid testing for the 737

Coulson Aviation intends for the 737 to be able to haul 4,000 gallons of retardant, or passengers

737 air tanker T-137 grid test retardant

Above: Air tanker 137, a 737-300, at the grid test near Lancaster, California, September 3, 2018. Coulson photo.

Coulson Aviation posted these photos September 3, 2018 of one of their recently converted 737-300’s, Tanker 137, as it was undergoing grid testing in Lancaster, California.

The process involves dropping retardant over a grid of thousands of cups intended to measure the volume and consistency of the pattern when it hits the ground. The Interagency AirTanker Board requires passing this and other certifications before an aircraft can be “carded” as a federal air tanker, which makes it eligible for a contract to fight fires.

Some air tankers are required to make 20 to 25 drops over several days at the test. Firefighting hand crews are usually hired or borrowed to retrieve the cups after each drop. It is a very expensive process. The last time we checked the price of retardant was $2.50 to $3.00 a gallon, depending on which air tanker base it is delivered to.

737 air tanker T-137 grid test retardant
Air tanker 137, a 737-300, at the grid test near Lancaster, California, September 3, 2018. Coulson photo.
737 air tanker T-137 grid test retardant
Air tanker 137, a 737-300, at the grid test near Lancaster, California, September 3, 2018. Coulson photo.

The interior of Coulson’s 737 looks futuristic.

737 air tanker T-137
Coulson’s installation of the internal retardant tank in the passenger compartment of their 737-300. They intend for the aircraft to have seats available for passengers, enabling it to do double-duty; drop retardant or haul passengers. Coulson photo.

They intend for it to be able to haul 4,000 gallons of retardant, or passengers. Last year Britt Coulson said, “With a full retardant load and 4.5 hours of fuel we are so far under max gross weight we are going to leave the full interior and galleys in even when just in airtanker mode.”

The company purchased six 737-300’s from Southwest Airlines.

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