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Crash of a Cessna 421C Golden Eagle III in Longmont

Date & Time: Jul 10, 2021 at 0845 LT
Operator:
Registration:
N66NC
Flight Phase:
Flight Type:
Survivors:
Yes
Schedule:
Longmont – Aspen
MSN:
421C-0519
YOM:
1978
Crew on board:
1
Crew fatalities:
Pax on board:
3
Pax fatalities:
Other fatalities:
Total fatalities:
0
Captain / Total flying hours:
2801
Captain / Total hours on type:
169.00
Aircraft flight hours:
5476
Circumstances:
The pilot reported that he performed the “before starting engine” and “starting engine” checklists and everything was normal before taking off in the twin-engine airplane. He performed an engine runup and then started his takeoff roll. The pilot reported that about halfway down the runway the airplane was not accelerating as fast as it should. He attempted to rotate the airplane; however, “the airplane mushed off the runway.” The airplane settled back onto the runway, then exited the departure end of the runway, where it sustained substantial damage to the wings and fuselage. The airplane engine monitor data indicated the airplane’s engines were operating consistent with each other at takeoff power at the time of the accident. Density altitude at the time of the accident was 7,170 ft and according to performance charts, there was adequate runway for takeoff. The reason for the loss of performance could not be determined.
Probable cause:
The loss of performance for reasons that could not be determined.
Final Report:

Crash of a Travel Air 4000 in Palmer Lake: 2 killed

Date & Time: Mar 2, 2016 at 0800 LT
Type of aircraft:
Registration:
N6464
Flight Phase:
Flight Type:
Survivors:
No
Schedule:
Longmont – Casa Grande
MSN:
785
YOM:
1928
Crew on board:
1
Crew fatalities:
Pax on board:
1
Pax fatalities:
Other fatalities:
Total fatalities:
2
Captain / Total flying hours:
5000
Circumstances:
The commercial pilot and the pilot-rated passenger were flying the biplane to a fly-in gathering in another state. Witnesses saw the airplane flying over a frozen lake at a low altitude and low airspeed. One witness saw the airplane "listing" left and right before it entered a left turn, and he lost sight of it. Other witnesses saw the airplane turn left and nose-dive into the ground. A postimpact fire consumed most of the airplane. Damage to the wreckage indicated that the airplane impacted the ground in a nose down attitude. The examination did not reveal evidence of any preimpact anomalies with the airframe, engine, or the control system of the airplane. A witness reported that, at the time of the accident, the wind was from the south about 30 miles per hour. However, a burnt area extending east from the airplane's impact point indicated the wind was from the west. Additionally, although wind information from nearby weather stations varied in direction and intensity. One station, about 14 miles west-northwest of the accident site reported calm wind., However, another station, located about 11 miles south of the accident site, recorded wind from the west at 11 knots with gusts to 27 knots about the time of the accident and wind from the west at 33 knots with gusts to 48 knots about an hour after the accident. Further, the forecast for the accident area called for wind gusts to 40 knots from the west-northwest. Therefore, it is likely that strong gusty west winds prevailed in the accident area at the time of the accident. Although some witnesses speculated that the pilot may have been attempting to land the airplane on the frozen lake, the airplane was not equipped to land on ice, and the reason the pilot was maneuvering at a low altitude in strong gusty winds could not be determined. Based on the witness observations and the damage to the wreckage, it is likely that the pilot allowed the airspeed to decrease to a point where the critical angle of attack was exceeded, and the airplane entered an aerodynamic stall/spin. Although the pilot was known to have heart disease, it is unlikely that his medical condition contributed to the accident. The witness observations indicate that the pilot was actively flying the airplane before the loss of control. Toxicology testing showed the presence of chlorpheniramine in the pilot's blood at a level that was likely in the therapeutic range. Chlorpheniramine is a sedating antihistamine available in a number of over the counter products, and it carries the warning, "May impair mental and/or physical ability required for the performance of potentially hazardous tasks (e.g., driving, operating heavy machinery)." Because of its sedating effect, chlorpheniramine may slow psychomotor functioning and cause drowsiness. It has also been shown in a driving simulator (after a single dose) to suppress visual-spatial cognition and visual-motor coordinating functions when compared to placebo. Such functions would have been necessary for the pilot to maintain control of the airplane while maneuvering close to the ground in the strong gusty wind conditions. Therefore, it is likely that the pilot's ability to safely operate the plane was impaired by the effects of chlorpheniramine.
Probable cause:
The pilot's failure to maintain sufficient airspeed while maneuvering at low altitude in strong gusting winds, which resulted in exceedance of the airplane's critical angle of attack and an aerodynamic stall/spin. Contributing to the accident was the pilot's impairment due to the effects of a sedating antihistamine.
Final Report:

Crash of a Beechcraft C-45H Expeditor in Longmont

Date & Time: Jul 19, 2007 at 0900 LT
Type of aircraft:
Operator:
Registration:
N9562Z
Flight Phase:
Flight Type:
Survivors:
Yes
Schedule:
Hudson - Boulder
MSN:
AF-12
YOM:
1946
Crew on board:
2
Crew fatalities:
Pax on board:
0
Pax fatalities:
Other fatalities:
Total fatalities:
0
Captain / Total flying hours:
15000
Copilot / Total flying hours:
20000
Copilot / Total hours on type:
13
Aircraft flight hours:
3925
Circumstances:
During the instructional flight, the instructor shut down the right engine and feathered the propeller. It was subsequently restarted, but the left engine started running rough and began to vibrate. The left engine was shut down and the propeller feathered. Level flight was maintained from power produced by the right engine. The left engine was then restarted but instead of producing thrust, the engine produced more drag so it was secured again. Then the right engine began losing power. Full power was applied but the airplane continued to descend. The instructor lowered the landing gear and while in-transit, the airplane clipped the tops of trees. He was able to guide the airplane between two houses and impacted an open field. The airplane bounced across the road, struck a power pole, and caught fire. The two pilots evacuated the airplane via the main cabin door. Examination at the airport of departure disclosed two pools of oil at the approximate positions of the two engines. There were two trails of oil leading from the parking spot down the taxiway and onto the runway. Both engines were partially disassembled and examined. There was evidence that both engines had failed catastrophically due to oil starvation. The left engine crankshaft was broken and all the piston heads were at the tops of their cylinders. Pieces of metal were recovered from the right engine oil sump. According to the operator, the engine rocker box recovery system must be drained during preflight to avoid hydraulic lock. The instructor stated that when they preflighted the airplane, the drain valves were open (the drained oil is captured and recycled). He thought they had closed both valves. According to the operator, either the pilot's failed to close the drain valves or they were jammed in the open position. The operator said the latter was unlikely "because you can feel it move when you close it."
Probable cause:
The instructor pilot's improper preflight in that he failed to close the rocker box recovery system drain valves, resulting in a total loss of lubricating oil and subsequent oil starvation to both engines. A contributing factor was the trees.
Final Report:

Crash of a Beechcraft B90 King Air in Longmont

Date & Time: Jan 23, 1997 at 2050 LT
Type of aircraft:
Operator:
Registration:
N76GM
Flight Type:
Survivors:
Yes
Schedule:
Louisberg – Louisville – Vandalia – Longmont
MSN:
LJ-498
YOM:
1970
Crew on board:
1
Crew fatalities:
Pax on board:
0
Pax fatalities:
Other fatalities:
Total fatalities:
0
Captain / Total flying hours:
1310
Captain / Total hours on type:
42.00
Aircraft flight hours:
10530
Circumstances:
The pilot had made a refueling stop at Vandalia, Illinois. She did not observe the refueling process, but the FBO also operated a King Air and she felt he knew the proper procedure to follow. The airplane was reportedly serviced with 235 gallons of Jet-A fuel (total capacity is 384 gallons). The pilot flew between 7,500 and 10,500 feet. When the airplane was 45 minutes from its destination, the fuel transfer pump lights illuminated, indicating the wing tanks were empty. The nacelle tank gauges registered 3/4 full and the pilot determined she had sufficient fuel to complete the flight. When the airplane was three minutes from its destination, both engines flamed out and the pilot made a wheels up forced landing. When the salvage company recovered the airplane, they reported finding no evidence of fuel aboard. The pilot was provided and used performance charts for the Beech 65-A90 instead of the Beech B90.
Probable cause:
Failure of the pilot to refuel the airplane, resulting in fuel exhaustion. Factors were the pilot's reference to similar but different aircraft performance charts, and the operator's failure to provide the pilot with the proper performance charts.
Final Report:

Crash of a Douglas DC-6B near Longmont: 44 killed

Date & Time: Nov 1, 1955 at 1903 LT
Type of aircraft:
Operator:
Registration:
N37559
Flight Phase:
Survivors:
No
Schedule:
LaGuardia – Chicago – Denver – Portland – Seattle
MSN:
43538
YOM:
1952
Flight number:
UA629
Crew on board:
5
Crew fatalities:
Pax on board:
39
Pax fatalities:
Other fatalities:
Total fatalities:
44
Captain / Total flying hours:
10086
Captain / Total hours on type:
703.00
Copilot / Total flying hours:
3578
Copilot / Total hours on type:
1062
Aircraft flight hours:
11949
Circumstances:
After a routine radio ramp check, Flight 629 taxied to runway 08R (80 degrees, right) and at 1844 the flight was in runup position where it was given ATC clearance for the flight to Portland, the first intended landing. The clearance, in part, included compulsory radio reports from the flight upon passing the Denver Omni and when climbing through 18,000 feet to its assigned flight altitude, 21,000 feet. Following takeoff the flight reported its "off time" to the company as 1852 and thereafter reported passing the Denver Omni at 1856. The latter communication was the last from the flight. About 1903 the Denver tower controllers saw two white lights, one brighter than the other, appear in the sky north-northwest of the airport and fall to the ground. Both lights were observed 30-45 seconds and seemed to fall with approximately the same speed. There was then a momentary flash originating at or near the ground which illuminated the base of the clouds, approximately 10,000 feet above. When the controllers observed the lights they initiated action to determine if any aircraft were in distress. Radio calls were made to all aircraft in the Denver area of responsibility and all except flight 629 were accounted for. It was soon learned that the flight had crashed and all 44 occupants had been killed. It was later confirmed that the disintegration of the aircraft in the air was caused by a bomb. Two weeks later, on November 15, investigators confirmed that an explosive device has been placed on board by John Gilbert Graham aged 23 who signed a US$ 37,500 life-insurance for his mother who was on board. Convicted guilty for murder and terrorism, he was sentenced to death penalty and executed on January 11, 1956.
Probable cause:
The Board determines that the probable cause of this accident was the disintegrating force of a dynamite bomb explosion which occurred in the number 4 baggage compartment. The following findings were reported:
- At 1903, eleven minutes after departure, an in-flight disintegrating explosion occurred aboard Flight 629,
- The aircraft was climbing normally and was on course when the explosion occurred,
- Physical evidence showed conclusively the explosion took place in the number 4 baggage compartment of the aircraft,
- The violence of the explosion and the physical evidence proved the explosion was not caused by any system or component of the aircraft,
- Physical evidence at the scene and laboratory tests confirmed that the explosive material was dynamite, in the form of a bomb,
- There was no evidence found to indicate malfunction or failure of the aircraft or its components prior to the explosion.
Final Report: