Humidity slows Texas fires, DC-10 drops 58,000 gallons

DC-10 Wildcat fire 2011-04-19
A DC-10 air tanker drops on the Wildcat fire in Texas, Aprilo 19, 2011. Photo: InciWeb

The humid weather that moved into Texas on Wednesday and Thursday has slowed the spread of the fires, after 1 million acres in the state have been blackened since the first of the year.

Here is the status of the five largest fires in the country as of Thursday morning, all of them in Texas. As you can see from the “size change in the last 24 hours” column, there was much less fire growth than in previous days. The data is from the National Interagency Coordination Center.

Top 5 Texas fires, April 21, 2011

The disagreement about the inspections on the P-3 Orions that caused Aero Union to voluntarily ground their eight air tankers has been resolved, following a meeting on Tuesday between the company and the U.S. Forest Service, according to a spokesman for the National Interagency Coordination Center in Boise that Wildfire Today talked with on Thursday.

Today there are seven air tankers in Texas, plus four military MAFFS air tankers. Most heavy air tankers are not on contract this time of the year, so it is not the easiest thing in the world to round them all up and dispatch them to fires.

10 Tanker Air Carrier has two passenger-carrying DC-10 airliners that have been converted into air tankers, carrying, instead of 250 to 380 passengers, 11,600 gallons of retardant. When they received the call about the fires in Texas, both of their DC-10s were undergoing heavy maintenance which they typically do in March and April each year. They were able to button one up and put it back in service fairly quickly, but the second one was torn down and too deep into the maintenance to put it in the air on short notice.

DC-10 air tanker 2011-04-19
DC-10 air tanker dropping on the Wildcat fire in Texas, April 19, 2011. Photo: InciWeb

But 10 Tanker Air Carrier sent one DC-10 to Midland, Texas on Sunday and put it to work. Tuesday it flew five missions, dropping a total of 58,000 gallons of retardant on the Wildcat fire.

Most large air tankers do not always completely fill their retardant tanks. They have to carry less than the maximum capacity depending on the density altitude, which is affected by the temperature, humidity, and the altitude at which the aircraft is operating. As the altitude, temperature, and the humidity increase, an aircraft can carry less weight. But the DC-10 always carries 11,600 gallons of retardant weighing about 100,000 pounds. This is due to the huge fuel capacity which enabled the aircraft to carry passengers on 10 to 11 hour flights halfway around the world without having to refuel. The DC-10 air tanker can vary the amount of fuel carried to offset any density altitude issues.

10 Tanker Air Carrier has one of their DC-10s under an exclusive use 3-year contract with CalFire which goes through 2012. Their second DC-10 is on a call when needed contract and is only activated when it is specifically needed. Rick Hatton, the CEO and President of the company, told Wildfire Today that if the second ship is put on an exclusive use contract, they have the financing available to build a third DC-10 air tanker.

The tanks that are bolted onto the bottoms of their aircraft are the same ones that the Erickson Air Crane helicopters use, but the helicopters only use one instead of the three that the DC-10s carry. The three tanks on the DC-10 can be filled in eight minutes if three retardant hoses are used.

Mr. Hatton told us that with the humid weather that has moved into Texas, their DC-10 may be released by the end of this week.

KTXS has a good video of the DC-10 dropping. Be sure and click on “full screen”. has an interesting interactive map which provides a variety of information about the fires.

National Geographic has a selection of excellent photos of the fires.


Wildcat Fire April 17, 2011
Wildcat Fire April 17, 2011. Photo: InciWeb

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Author: Bill Gabbert

After working full time in wildland fire for 33 years, he continues to learn, and strives to be a Student of Fire.

One thought on “Humidity slows Texas fires, DC-10 drops 58,000 gallons”

  1. re: photo of tanker dropping retardant. Is dropping across power lines common? I do not know a lot about air tanker tactics, but it raises concerns. I’m thinking safety issues, can someone educate me if I’m wrong? Not trying to armchair quarterback, just wondering…


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