Mystery still shrouds deadly weekend small plane crash

The coroner in Boulder County has yet to identify the remains of four people on board a Cessna Skymaster that went down in Lefthand Canyon Sunday morning. The plane was operated by Bluebird Aviation said the NTSB. The company based out of Rocky Mountain Metropolitan Airport in Broomfield flew for only about ten minutes before going down on a steep incline and starting a fire.

"Everything's going to be looked at, I mean the toxicology reports are going to be looked at. The maintenance of the aircraft and whether the engines were performing properly. Weather, performance, maintenance, human factors, they're all going to be looked at, to see if one was a major contributing factor, or if all were a contributing factor," explained Kevin Kuhlmann, chair of the Aviation and Aerospace Science department at Metropolitan State University of Denver.

Flight data shows the plane was cruising at over 100 miles an hour shortly after takeoff until it made a turn in the canyon after going over Gold Hill. Then the airspeed fell into the 70s as the plane turned. Then it turned again while losing altitude and crashed.

The company flew sightseeing tours, carrying passengers often over the foothills. Its state registration shows Benjamin Thompson of Louisville as registrant and director of operations. The Bluebird Aviation website, now down, showed a picture of pilot Benjamin Thompson. FAA records show the plane's registration lapsed at the end of April. The FAA said the registration would be part of the investigation.

But the airport is not under any requirement to check a plane's registration prior to departure or landing. 

"The person flying the aircraft might not necessarily be the person that owns the aircraft. But it is still the responsibility of the pilot when he gets in that aircraft to make sure that the registration is current. Because that is one thing that is required to be on board and visible. It all boils down to the pilot," said Justin Parrow, longtime owner of an aircraft maintenance company based at the airport, which he recently sold. 

The registration is not dependent on the airworthiness of the aircraft. 

"No it's completely separate," said Parrow.

 Required logs keep track of items like an aircraft's maintenance.

"Every year an aircraft has to go through the annual inspection process," explained Parrow. 

"You do a physical inspection on the engine, the airframe, that landing gear. Make sure all bearings are within tolerances, the engines are the compressions on the engines are good," he said. 

"Same thing with the airframe itself. You take out all the seats, open up the floors, and do a real good inspection on all that," said Parrow. 

But there's no indication yet that the aircraft's condition was to blame, or that there was any failure to do the annual maintenance.

"The rising of the terrain in the performance of the aircraft don't always match up and especially when you're talking about fixed wing single engine multi-engine aircraft small aircraft," said Kuhlmann, noting that less experienced pilots might have difficulty. Colorado's mountains hold special challenges with the thin air at altitude. 

"You certainly can get weather conditions that are different and influenced by the rising and descending terrain, so you do get updrafts and downdrafts," said Kuhlmann. 

Planes have gone down when pilots get into canyons from which there is no escape, but over altitude, they cannot achieve. 

"The pilot may have tried to climb, and when the airspeed gets below a certain level the wing can stall, which is not to be confused with engines stopping," said Kuhlmann.  

A stall in an aircraft is a matter of aerodynamics. There isn't enough lift.  All are only potential, noted Kuhlmann, in a process that could take a long time. None of the potentials are to blame until an investigation is complete.