Accidents: Final Report Roundup

 - July 15, 2008, 9:21 AM

CESSNA 303, BINGHAMTON, N.Y., NOV. 1, 1999–The NTSB issued a final report on the Cessna twin that landed short after executing a single-engine missed approach (Accident Recaps, January 2000). Safety Board investigators determined probable cause as “the pilot’s improper in-flight decision to descend below the decision height without the runway environment in sight, and his failure to execute a missed approach. A factor in the accident was the failed crankshaft.”

The pilot–commercially certified with 2,430 hr total time and 200 hr multi-engine experience–departed Portland, Maine shortly before 0400. In cruise en route to Youngstown, Ohio, the left engine oil pressure fluctuated and then went to zero. The pilot attempted a restart without success, and in doing so was unable to feather the propeller. He told the NTSB the prop eventually feathered; however, during attempts to restart the engine, the Cessna’s airspeed degraded to blue line.

The pilot contacted Binghamton Approach and asked for the closest VFR airport. That was 60 miles away. No longer able to maintain altitude, he initiated a descent into Binghamton (BGM); proximity and radar coverage played a part in his decision.
Binghamton weather at 0608 EST reported wind calm, quarter-mile visibility in fog, vertical visibility of 100 ft and temperature and dew point of 45 deg F.

The pilot shot the ILS to Runway 16 but DH yielded no visible landmarks so he initiated a missed approach. Unable to climb higher than 2,200 ft–BGM’s elevation is 1,636 ft–he told the controller of his predicament. The controller vectored him inside the outer marker for the ILS Runway 34, since the minimum altitude outside the marker is 3,900 ft.

During the second approach the pilot told the controller he was going to fly the aircraft all the way down to the runway. Unlike the first approach, he shot this one with the gear down. He told the NTSB investigators he “flew down past decision height” and at about 70 ft to 80 ft agl “added a little power to smooth the landing.” He also told investigators, “The last thing I remember was the aircraft nose contacting the runway; I may have instinctively pushed the throttle forward…” One of his passengers later told the NTSB the engine noise near touchdown sounded much like the full go-around noise he had heard on the first approach. While the pilot sustained serious injuries, the two passengers received only minor injuries.

Investigators oversaw the disassembly of the twin’s left engine and found the crankshaft fractured between the number two connecting rod journal and its main. The Safety Board’s materials lab examined the crankshaft by optical microscopy and found “several areas of smooth features, curving boundaries and ratchet marks, all typical of fatigue.”

CESSNA 421, HOMEWOOD, MISS., JULY 25, 2000–Four passengers and two pilots walked away from what the NTSB describes as an uneventful landing. While the landing may have been uneventful the fact that the right propeller “completely separated” from the engine in flight and hit the right horizontal stabilizer on departure may have aroused interest (Accident Recaps, September 2000). While in cruise flight at 12,000 ft, the PIC recalled he felt only a slight vibration before the propeller fell off the airplane. He declared an emergency and diverted into Jackson International (JAN).

An airworthiness inspector examined the airplane for the NTSB and found the top of the horizontal stabilizer crushed “nearly full span;” the impact had also pushed the outboard section down nearly 35 deg. Insurance representatives offered a reward for the missing propeller, and it was found in mid-November.

The Safety Board concluded the separation was caused by “the inadequate installation of the right propeller by the mechanic for his failure to properly torque the eight nuts, resulting in fatigue failure of the studs and separation of the right propeller during cruise flight.” Findings in the investigation: the mechanic who installed the right propeller used un-calibrated torque wrenches and an outdated Service Manual.”

EUROCOPTER AS 355, BURLINGTON, N.C., OCT 16, 2000–The NTSB issued its final report in the fatal crash of a Eurocopter TwinStar owned by Duke University (Accident Recaps, December 2000). Operated by Corporate Jets, Inc., the flight’s mission was a Part 91 ferry flight to return the aircraft to its base for maintenance.

Shortly after 2200, the helicopter departed Duke University Medical Center in Durham for Alamance Regional Medical Center in Burlington, about a 25-nm flight.
The pilot and two flight nurses were on board. On the flight to Alamance, the main transmission oil pressure warning light illuminated. The flight nurses recalled the pilot told them they were halfway between the Burlington-Alamance Regional Airport and their destination. They decided to continue to the hospital and land. After landing, the pilot immediately shut down the engines and told the flight nurses he would not do an engine cooldown. He canceled the return transport flight and called for a mechanic. One flight nurse checked back with the pilot before heading out, and the pilot told her the warning light had probably been illuminated by a short in the switch.

When the mechanic arrived at 2330, the pilot briefed him that all was normal except the transmission oil pressure light. He inspected the helicopter for excessive oil leaks and found none. Satisfied with the inspection of the engine, he disconnected the wire from the transmission oil pressure switch and the light went out.

In an interview with NTSB investigators, the mechanic verified he did not reconnect the switch. He didn’t have fault isolation manuals with him. Both the mechanic and pilot knew the switch had a history of trouble, so they decided to ground run and hover the helicopter. If this produced no indications of vibration, noise, chip light or temperature irregularities, the pilot would ferry the aircraft back to Duke Hospital. After “a period of runup and then hovering time” the pilot turned his landing light off and departed the helipad. The crash site was found 1.3 mi east-southeast of the departure point where the helicopter had collided with trees, separating the tail boom from the fuselage.

The Safety Board determined probable cause as “the mechanic’s failure to comply with manufacturer’s instructions for correction of an illuminated main rotor gearbox oil pressure warning light, resulting in the helicopter being dispatched on a ferry flight with a failed main rotor gearbox oil pump, failure of the main rotor gearbox combining gearbox gears due to oil starvation, loss of main rotor rpm, and the helicopter colliding with trees and the ground during an uncontrolled descent.”

BEECH KING AIR B90, WEST PALM BEACH, FLA., SEPT. 3, 1999–“A total loss of engine power due to fuel exhaustion” is the conclusion the NTSB drew in the fatal crash of a Lifeguard flight that killed the pilot and seven passengers. Contributing factors included over-gross weight and inadequate preflight and in-flight planning.

The pilot filed an IFR flight plan departing Pontiac, Mich. at 2100 for Boca Raton, Fla. with a cruising altitude of 15,000 ft. His flight plan estimated the time en route at five hours with six hours of fuel on board. Investigators verified with the refueler that the tanks were topped as requested; records showed line service pumped 282 gal (1,889 lb) into the King Air at Pontiac. The FAA calculated the aircraft departed some 720 lb over mtow.

The flight (callsign Lifeguard 8AS) departed Pontiac at 2231, climbed to 15,000 ft and flew uneventfully until 0323, when the pilot asked Palm Beach tower if he could change his destination and land at Palm Beach International (PBI). The controller told the pilot the airport was at his 10 to 11 o’clock position and five miles. The pilot told the controller he had the airport in sight, and the controller cleared him to land.

Less than three minutes later, at 0325:27, the pilot radioed “Alpha Sierra, we need, ah, we got mayday, Alpha Sierra mayday.” A sheriff’s department helicopter called the tower at 0325:40 to say they spotted the aircraft wreckage and requested fire and rescue. According to the NTSB final report, the airplane struck a building and power lines before coming to rest in a cluster of trees about half a mile short of Runway 13. Post-crash fire and impact forces destroyed about 80 percent of the fuselage and the cabin was found inverted. Investigators found the crossfeed switch in a position that suggested the pilot was attempting to “operate both engines on one fuel system.”

Investigators at Pratt & Whitney Canada concluded neither engine was producing power at the time of impact, and neither propeller was feathered. Substantiating those efforts, a sound spectrum analysis was conducted by the NTSB’s vehicle recorders division on the ATC tapes. Investigators found the only signatures present in the aircraft’s last transmissions were voice.

Using the airplane flight manual, investigators calculated the fuel flow at 15,000 ft to be 524 pph. They used ATC transcripts to calculate the actual time to climb (34 min vs 24 predicted for a mtow climb) and figured the King Air burned an extra 73 lb in the climb. Regardless, the manual showed the flight required four pounds more fuel than the aircraft had capacity for, and that did not include the required night reserves.