Denver-Stapleton

As the cargo jet was taxiing for takeoff in a non movement area, it was struck by an airport employee shuttle bus. The airplane captain was seriously injured. Visual meteorological conditions prevailed, and the collision occurred during predawn hours. The bus driver said he stopped at the stop sign, turned on the 4-way flasher lights, and looked both ways. He saw one inbound aircraft to the right that had stopped. He did not see the airplane approaching from the left as he started across the cargo ramp. The airplane crew stated they did not see the bus until seconds before impact. Airplane skid marks, measuring 22 and 24 feet in length, were noted on the taxiway. No bus skid marks were noted on the roadway.

While in a descent for arrival at the destination airport, the aircraft sustained structural failure with the right outer wing, horizontal stabilizer, and vertical stabilizer separating from the aircraft. The aircraft impacted approximately 10 miles from the planned destination. According to radar data and other research, the descent was conducted at vne and known severe turbulence was present in the area at the time of the accident.

The pilot of the air ambulance feathered the right propeller after reporting 'a bit of a problem' with the right engine. He attempted to divert to the nearest suitable airport, but after receiving its latest weather report, elected to return to base. The airplane made a left turn, reentered IMC, and impacted a mountainside on a magnetic heading of 092°. The heading to the airport of intended landing was 272°. The accident occurred during a snowstorm at night. All five occupants survived and were rescued the following afternoon. Thick grease on the right engine fuel control camshaft prevented a spring from returning the 3d cam to a lower altitude position. The cam was found struck on the shaft at a position equating to an altitude of approximately 15,000 feet. The fuel flow schedule for flight idle was below specifications. In addition, shroud material was found delaminated from the left engine second stage compressor housing.

On March 3, 1991, a United Airlines Boeing 737, registration number N999UA, operating as flight 585, was on a scheduled passenger flight from Denver, Colorado, to Colorado Springs, Colorado. Visual meteorological conditions prevailed at the time, and the flight was on an instrument flight rules flight plan. Numerous witnesses reported that shortly after completing its turn onto the final approach course to runway 35 at Colorado Springs Municipal Airport, about 0944 mountain standard time, the airplane rolled steadily to the right and pitched nose down until it reached a nearly vertical attitude before hitting the ground in an area known as Widefield Park. The airplane was destroyed, and the 2 flight crewmembers, 3 flight attendants, and 20 passengers aboard were fatally injured.

The Cessna 208A was on an IFR flight to haul freight from Aspen to Denver, Colorado. Moderate to heavy icing conditions were forecast for the Denver area. While on an ILS runway 36 approach, the aircraft encountered icing conditions. Subsequently, it entered a steep descent and crashed about 3 miles from the approach end of the runway. No preimpact part failure of the aircraft was found during the investigation. The 1950 mst weather at the airport was in part: 800 feet scattered, 1,000 feet broken, visibility 4 miles with freezing drizzle and snow showers, temp 28°, dew point 25°.

PM Air flight 824, a Federal Express scheduled domestic cargo flight, departed Denver, CO, at 0642, IFR to Montrose, CO. Flight was cleared to FL180, but pilot cancelled IFR at 0653. Radar showed aircraft leveled off at 14,500 feet on southwest heading. Aircraft maintained relative constant altitude and heading before crashing 50 feet below summit of 14,221-feet Mt Massive, second tallest peak in Colorado, at approximately 0719. Weather was cavu. Toxicological tests revealed marijuana metabolite level of 37 ng/ml in urine and 1 ng/ml in blood. Pilot was once convicted in 1974 for possession of controlled substance, but had no other alcohol/drug convictions. Evidence indicates pilot obtained adequate sleep prior to flight. During autopsy, two pages from airmen's information manual were found clutched in plt's hands. The pilot, sole on board, was killed.

United Flight 232 departed Denver-Stapleton International Airport, Colorado, USA at 14:09 CDT for a domestic flight to Chicago-O'Hare, Illinois and Philadelphia, Pennsylvania. There were 285 passengers and 11 crew members on board. The takeoff and the en route climb to the planned cruising altitude of FL370 were uneventful. The first officer was the flying pilot. About 1 hour and 7 minutes after takeoff, at 15:16, the flightcrew heard a loud bang or an explosion, followed by vibration and a shuddering of the airframe. After checking the engine instruments, the flightcrew determined that the No. 2 aft (tail-mounted) engine had failed. The captain called for the engine shutdown checklist. While performing the engine shutdown checklist, the flight engineer observed that the airplane's normal systems hydraulic pressure and quantity gauges indicated zero. The first officer advised that he could not control the airplane as it entered a right descending turn. The captain took control of the airplane and confirmed that it did not respond to flight control inputs. The captain reduced thrust on the No. 1 engine, and the airplane began to roll to a wings-level attitude. The flightcrew deployed the air driven generator (ADG), which powers the No. 1 auxiliary hydraulic pump, and the hydraulic pump was selected "on." This action did not restore hydraulic power. At 15:20, the flightcrew radioed the Minneapolis Air Route Traffic Control Center (ARTCC) and requested emergency assistance and vectors to the nearest airport. Initially, Des Moines International Airport was suggested by ARTCC. At 15:22, the air traffic controller informed the flightcrew that they were proceeding in the direction of Sioux City; the controller asked the flightcrew if they would prefer to go to Sioux City. The flightcrew responded, "affirmative." They were then given vectors to the Sioux Gateway Airport (SUX) at Sioux City, Iowa. A UAL DC-10 training check airman, who was off duty and seated in a first class passenger seat, volunteered his assistance and was invited to the cockpit at about 15:29. At the request of the captain, the check airman entered the passenger cabin and performed a visual inspection of the airplane's wings. Upon his return, he reported that the inboard ailerons were slightly up, not damaged, and that the spoilers were locked down. There was no movement of the primary flight control surfaces. The captain then directed the check airman to take control of the throttles to free the captain and first officer to manipulate the flight controls. The check airman attempted to use engine power to control pitch and roll. He said that the airplane had a continuous tendency to turn right, making it difficult to maintain a stable pitch attitude. He also advised that the No. 1 and No. 3 engine thrust levers could not be used symmetrically, so he used two hands to manipulate the two throttles. About 15:42, the flight engineer was sent to the passenger cabin to inspect the empennage visually. Upon his return, he reported that he observed damage to the right and left horizontal stabilizers. Fuel was jettisoned to the level of the automatic system cutoff, leaving 33,500 pounds. About 11 minutes before landing, the landing gear was extended by means of the alternate gear extension procedure. The flightcrew said that they made visual contact with the airport about 9 miles out. ATC had intended for flight 232 to attempt to land on runway 31, which was 8,999 feet long. However, ATC advised that the airplane was on approach to runway 22, which was closed, and that the length of this runway was 6,600 feet. Given the airplane's position and the difficulty in making left turns, the captain elected to continue the approach to runway 22 rather than to attempt maneuvering to runway 31. The check airman said that he believed the airplane was lined up and on a normal glidepath to the field. The flaps and slats remained retracted. During the final approach, the captain recalled getting a high sink rate alarm from the ground proximity warning system (GPWS). In the last 20 seconds before touchdown, the airspeed averaged 215 KIAS, and the sink rate was 1,620 feet per minute. Smooth oscillations in pitch and roll continued until just before touchdown when the right wing dropped rapidly. The captain stated that about 100 feet above the ground the nose of the airplane began to pitch downward. He also felt the right wing drop down about the same time. Both the captain and the first officer called for reduced power on short final approach. The check airman said that based on experience with no flap/no slat approaches he knew that power would have to be used to control the airplane's descent. He used the first officer's airspeed indicator and visual cues to determine the flightpath and the need for power changes. He thought that the airplane was fairly well aligned with the runway during the latter stages of the approach and that they would reach the runway. Soon thereafter, he observed that the airplane was positioned to the left of the desired landing area and descending at a high rate. He also observed that the right wing began to drop. He continued to manipulate the No. 1 and No. 3 engine throttles until the airplane contacted the ground. He said that no steady application of power was used on the approach and that the power was constantly changing. He believed that he added power just before contacting the ground. The airplane touched down on the threshold slightly to the left of the centerline on runway 22 at 16:00. First ground contact was made by the right wing tip followed by the right main landing gear. The airplane skidded to the right of the runway and rolled to an inverted position. Witnesses observed the airplane ignite and cartwheel, coming to rest after crossing runway 17/35. Firefighting and rescue operations began immediately, but the airplane was destroyed by impact and fire. The accident resulted in 111 fatal, 47 serious, and 125 minor injuries. The remaining 13 occupants were not injured.

During flight, crew shut down the right engine when warning light for gearbox oil pressure illuminated and pressure was noted below minimum limit of 130 psi. Shortly after securing right engine, left engine lost power (fuel tank shutoff valve switch and fuel crossfeed valve switch were located near each other). Attempts to restart left engine were unsuccessful. With lack of alternative current electrical power, captain could not unfeather right engine for restart. During emergency landing, aircraft was damaged on uneven terrain. Operational check of right engine (at ground level) revealed no malfunction that would have prevented normal operation. Examination of left engine revealed turbine section had overheated and turbine blades had severe heat damage. Captain said that when he tried to restart left engine, fuel valves were in normal position and power lever was 1' above idle. He recalled an engine rpm of 8000, but didn't recall if he had used feather button to reduce rpm to 3000 (as directed by checklist). He verified fuel switches were 'on' and he tried to crossfeed fuel (in event of blockage). Cross feeding of fuel was not part of restart procedure. Flight manual cautioned about importance of reducing power to flight idle, to decrease fuel flow to engine and minimize possible overheating.

The pilot was on a flight from Greeley to Denver, Colorado to obtain minor maintenance on a cargo door. As the aircraft was being vectored on final approach, the pilot reported that he believed the aircraft had fuel starvation. Subsequently, the aircraft was observed to make a complete roll and crash in a residential area. Only about 1.5 gallon of fuel was found in the right wing tank. The left wing and fuel tank were destroyed, but no odor of fuel was noted on the ground around the left wing. Also, a lack of fuel was noted in the fuel lines. The aircraft had not been refueled after the previous flight. The pilot that had flown the aircraft on a previous flight estimated there was 100 lbs of fuel remaining in each tank after his flight.

After making an IFR approach, the pilot made a go-around because he was blinded by the reflection of the landing/taxi lights against the falling snow. The pilot landed the aircraft after the second approach. The pilot said he sensed the aircraft drifting to the left and he tried to correct, but it collided with a snow bank. The investigation disclosed no evidence of aircraft hydroplaning or skidding. Airport management elected to delay plowing the runway for fear of it freezing over. Passengers claimed there was 2-3 inches of snow on top of a 3/4- inch layer of slush. Further investigation revealed that the runway lights were of various intensities because some unapproved light bulbs of different amperage were used. The runway was not equipped with centerline lighting. The painted white centerline stripe was covered by snow and slush.