Friends Says Report "Hugely" Shocking

The crash of a firefighting helicopter near Estes Park (CO) in 2002 was caused by pilot error, according to the NTSB final report, a finding that shocked the pilot's best friend.

"That floors me," said Gresham (OR) resident Jim Parker, who was business partners with the pilot, Gordon Knight. "I'd never expect anything like that."

Knight was 52, a Vietnam veteran and an experienced pilot. On July 30th, 2002, he got the call to drop water on the Big Elk fire, as officials hoped to keep it from spreading to Estes Park. He went to work flying an Aerospatiale SA315B file photo of type, below), beginning at about eight in the morning. He ran into trouble at about 3:30 that afternoon.

The NTSB report said, "According to witnesses, as the pilot made his approach for a third water drop, they heard engine sounds described as the 'engine screaming'; like a 'car was in neutral and the engine was running fast'; a 'high-pitch whine'; a 'high-pitch noise'; a 'strange noise' like the engine was 'under strain' or 'bogging down'; 'Rrrrrr'; and an 'electronic sound with grinding metal.' Some witnesses heard 'a loud pop,' or a 'snap.' Witnesses said the rotor blades were 'still turning' or 'slowing' or 'winding down.' One witness said the 'rotor sound was gone.' Many reported hearing the rotor blades making a 'thump, thump, thump,' or 'whoop, whoop, whoop' sound.

"Witnesses monitoring the helicopter's radio frequency reported hearing the pilot say, 'Hey guys, I'm having trouble, I'm going down'; 'I'm having trouble here'; 'Helicopter going down'; 'Going down, going down'; 'Boat down,' or words to that effect,' said the finding. 'Witnesses on the ground saw purple or blue flames coming from the exhaust stack. One witness said they were 'pinkish-colored.' Another witness said the flames 'took on a flame-thrower effect,' shooting flames two to three feet out the exhaust stack. Another witness reported seeing the helicopter falling 'skid down.' Another witness said that hitting the ground and rolling over, they heard the engine spooling down. Flames were seen 'coming from the engine after impact' and it 'sounded like a blowtorch.'"

The NTSB's initial survey of the wreckage indicated the helicopter's engine turbine blades had been severely overheated. "Longitudinal sectioning of the 1st, 2nd, and 3rd stage blades and 3rd stage NGV vanes were subjected to microscopic examination. The report stated, 'The deterioration found on all the above components result from overheating over a short period of time.' The report also stated that hardness tests indicated 'the temperature reached in the area of the turbine blades was around 1,000 degrees C.'"

So you'd think that means a mechanical failure rather than pilot error caused the crash, right? The NTSB says that's not the case. Investigators decided that Knight found himself settling with power, a situation where power decreases even as thrust is applied. The Bureau blamed Knight's "abrupt collective input" for the turbine overheating problem which led to the crash. Specifically the NTSB said his abrupt control manipulation caused a "ring vortex" at the engine's air intakes.

Investigators quoted author RW Prouty, who wrote Helicopter Aerodynamics. He wrote, "If the rate of descent exceeds 1/4 of the hover induced velocity, the flow conditions are such that the air is going both up and down through and around the rotor in a disorganized and unsteady manner. This is called 'vortex ring' state. It exists until the helicopter is descending at about twice the hover induced velocity.

"In the vortex ring state," Prouty continuted, "the helicopter pilot may find himself in the unusual situation where pulling up the collective pitch does not slow the rate of descent."

Parker called the NTSB's finding of pilot error "the second most shocking piece of news out of this whole thing, next to hearing that Gordon went down in a helicopter, even knowing that he was flying in some of the most dangerous conditions. Pilot error is the last thing that I would ever even conceive. Meticulous was an understatement when it came to Gordon. He was the most careful guy I have ever known."

FMI: NTSB Final Report