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."