Fire supertanker to return to duty next week - Is it worth the danger?

By RICHARD BROOKS
The Press-Enterprise

The nation's only jumbo fire bomber is scheduled to return to duty next week following repairs to a wing that was damaged when the converted jetliner hit several treetops and nearly crashed, officials say.

"We're thankful that no one got hurt and the damage was as minimal as it was," said Rick Hatton, managing partner of the company that owns the Victorville-based DC-10. "It's a testament to the robustness of the airplane."

The DC-10 became the nation's first giant supertanker last year when it fought fires in California and Washington.

The near-crash happened July 25 when the big jet clipped trees along a ridge top while its crew was preparing to drop 12,000 gallons of sticky red fire retardant -- 10 times the payload of California's regular air tankers -- on a blaze near Tehachapi.

"While in a left turn (onto final approach to the target) the left wing dropped downward and impacted several trees," according to a preliminary report by the National Transportation Safety Board.

The cause of the accident has not been determined. But the pilots say they hit air turbulence immediately before they hit the trees, Hatton said.

Since the accident, two of the DC-10's captains and one co-pilot, all experienced airline pilots, have undergone refresher training for air-tanker operations and have been accompanying veteran tanker pilots in the state's medium-sized S-2T tankers, state fire aviation officials say.

The accident inflicted substantial damage on the leading and trailing edges of the jet's left wing, including portions of the leading-edge slats, the ailerons and flaps, according to the preliminary report and Hatton.

Fixing the plane amounted largely to removing and replacing the damaged parts. The No. 1 engine was unscathed.

"That was pretty lucky, because it hangs down off the left wing, and there was damage to either side of it," Hatton said.

Two earlier drops that day on the same fire were uneventful. Hatton attributed the accident to unanticipated "extreme turbulence" near the ridge.

"The description I heard from the crew ... was that there was nothing abnormal about the situation. It was going very well," Hatton said. "Then 'the bottom fell out' on the left wing due to this condition of air (turbulence) that can sometimes happen in mountain flying."

As part of its standard procedures, the jet was following a much smaller "lead plane" that points out the target and acts as a pathfinder to the drop point.

The lead plane made its run successfully. But it may have taken a slightly different path than the jet, or the turbulence may have developed after the lead plane passed the trouble spot, Hatton said.

The jet fights fires under a $5 million contract with Cal Fire, the California Department of Forestry and Fire Protection, which operates its own fleet of 23 medium-size air tankers and uses the DC-10 as its "big gun."

Cal Fire Investigating

Cal Fire is doing its own investigation of the accident.

"We know (the cause) is not mechanical," said Chief Mike Padilla, who oversees the agency's aviation division. "There was turbulence that day, but we don't think that was the sole cause.

"We're looking at everything from the weather -- turbulence -- on that date to our procedures for lining up the aircraft (toward the target) and how the pilots were perceiving the drop."

Although it's common practice for tanker pilots to jettison their retardant during an emergency, the DC-10 crew didn't drop the 96,000-pound load.

"They did not perceive that they had a need to do that," said Padilla.

"They thought they'd hit some turbulence because they felt the bump," he said.

But the treetops apparently caused most of the bump, although the crew didn't realize it.

"As they pulled up, the lead (plane pilot) looked back ... and advised them that they had damage to the wing," Padilla said.

Emphasizing that his agency's investigation isn't complete, Padilla said that accidents rarely happen for only one reason.

Fooled by Terrain

In this case, the pilots were turning onto their final approach near a ridgeline in a type of plane that is new to firefighting and low-level mountain flying.

"Even experienced pilots get fooled by the (mountainous) terrain, which affects your perception," Padilla said. "We've had several tree strikes this year."

Preventing additional accidents requires detailed analysis of many factors, he said, ranging from the agency's procedures for lead planes and tankers to the DC-10's operating methods and the pilots' training, decisions and actions.

There are many questions to be answered, he said.

"What is the pilot perceiving? What is he looking at? How do we give him an extra margin of safety? Do we line him up sooner? Do we not turn over ridgelines?" Padilla mused. "Do we drop (the retardant) from a higher altitude?"

And since pilots can't see wind, they have to know how it behaves near ridgelines and what to expect.

"You get lift on the side where the wind's coming from," Padilla said. "And as it goes over the hill, you'll get turbulence as (it breaks like a wave at the beach and) it begins to burble.

"Aerial firefighting is more of an art than a science."