(Originally published at 11:24 a.m. MDT, August 3, 2014; revised August 4, 2014)
The issues that kept one of the DC-10s and all three of the MD-87 air tankers grounded for a while have been partially mitigated for the MD-87s, and totally fixed in the case of the DC-10.
Tanker 910, a DC-10 operated by 10 Tanker Air Carrier, suffered some damage to a wing on July 19 as it was taxiing at the air tanker base at Moses Lake, Washington. While relocating in the loading pit area the aircraft struck a portable “air stair”, a structure that can be pushed up to the aircraft door. Two people on the ground were marshaling the DC-10 as it slowly moved, directing it where to go and supposedly watching for obstructions. Rick Hatton, President of 10 Tanker, told us that the air tanker was back in service on July 28.
Mr. Hatton said their second DC-10, Tanker 911, has been busy on fires. The third one being built now, Tanker 912, was test flown on August 2. It will enter service later this month, perhaps as early as August 11.
On June 27 Erickson Aero Tanker recalled the three MD-87s they were operating, tanker numbers 101, 103, and 105, “due to intermittent engine surges when dropping [retardant at] high coverage levels”, according to the U.S. Forest Service. The Oregonian later reported that retardant was being ingested into the engines. On June 30 Tanker 101 returned to service, but with restrictions. Tanker 105 should be in service the week of August 4, but with same restrictions.
We have confirmed that the air tanker is limited to no more than coverage level four, which is four gallons per 100 square feet — about half of the maximum coverage level for fully capable air tankers. Our understanding of the issue is that the MD-87s have two retardant openings on the belly. On most air tankers they are called “doors”, since they operate much like a door on a hinge, swinging down on some air tankers. But the MD-87 has two “spades”, which function like a stopper in a bathtub. The spade in the aircraft normally plugs the hole, but raises, in a constant-flow manner, to allow retardant to flow around it and exit the aircraft.
Tanker 101 is using just the left spade instead of both. That spade now has half a funnel at the leading edge to get the retardant moving backwards as it comes out. There is a report that a slight mist was still contacting the wing but it appears that retardant is no longer going into the engines. The leading edge slats make that small amount of retardant that touches the wing look worse than it is.
One of the MD-87 pilots is qualified for initial attack.
Phone calls to Erickson Aero Tanker requesting comments on this issue were not returned.