MITSUBISHI MU-2, LEWISTON, IDAHO, FEB. 11, 2000–“The pilot failed to follow the flight manual procedures and did not engage the continuous ignition system, resulting in both engines flaming out when ice blocked the air induction system. Additional factors to the accident included the hilly terrain, the icing conditions and the operator’s non-compliance with a Service Bulletin for the installation of an auto-ignition system.” So reads the probable cause in the NTSB’s final report on N152BK, an American Check Transport MU-2. The pilot died when he hit a ridge a mile-and-a-half short of the runway at Lewiston-Nez Perce Airport.
The flight departed Boise, Idaho, at 0723 destined for Lewiston. A second leg of an all- day cargo run, the flight originated in Salt Lake City. The routine, which the pilot regularly flew during the preceding 12 months, was to fly during the morning from Salt Lake City to Boise to Lewiston and then to Coeur d’Alene, Idaho. In the early evening the pilot would return to Salt Lake City via Lewiston and Boise. Aircraft records showed the flight time to complete the run was 5.2 hr; in between, the pilot got nine hours of rest.
Retired from a major airline, the pilot was an ATP and CFI in single and multi-engine land airplanes. He held type ratings in several transport-category aircraft, including the Boeing 747. The NTSB estimated his total flight time at 21,000 hr, with all but 1,300 hr in multi-engine airplanes. He had flown approximately 1,100 hr in the 13 months preceding the accident and 321 hr in the 90 days before the accident. He was qualified to fly the company’s MU-2s and PA-31s.
En route to Lewiston, the pilot talked to Seattle Center and finally the Lewiston Tower. At approximately 0756, N152BK descended from cruise at 16,000 ft to 6,000 ft. Controllers issued a hold for spacing before shooting the ILS to Runway 26. Various pireps between 0644 and 0916 indicated the presence of light to moderate rime and mixed icing between 7,000 and 15,000 ft. Airmet Zulu was valid for moderate rime and mixed icing in clouds and precipitation below 15,000 ft.
While radar contact was lost below 6,000 ft, ATC records show at 0810:37 the pilot reported inbound on the ILS 26 approach. Minutes later the controller said, he saw the MU-2 break out of the clouds roughly four miles out. He gave the pilot the option of landing on Runway 29 as the wind was 300 deg at 13 kt gusting to 21 kt. The pilot elected to land on Runway 29 and almost simultaneously radioed, “I just had two flameouts. I’m going in.” Five seconds later, at 0815:30, N152BK reported, “I’m gonna pick out ah, ah...” His last transmission was at 0815:32: “Pickin out, ah, I’ll go as far as I...” The ELT went off at 0815:48.
The aircraft hit the ridge line about 20 ft from the top and about 1.5 mi east of the airport. On-site examination of the turboprop found the pilot’s shoulder harness was hanging loose and not attached to the seatbelt buckle. Fire department personnel confirmed, when they arrived at the accident site, the pilot’s seatbelt was fastened but the shoulder harness was not. Cockpit switches were found in the following positions: main fuel valves open; left and right pitot heat on; left and right engine inlet heat off; propeller anti-ice, left off, right on; oil cooler inlet anti-ice, left on, right off; left and right continuous ignition off.
According to the aircraft flight manual for the MU-2B-60, “The continuous ignition system, which operates engine ignition manually, shall be selected to on during takeoff, landing or flight in severe weather conditions, especially all operations in actual or potential icing conditions described herein and where there is water, slush or snow on the runway.”
The AFM further states the continuous ignition should be on “during takeoff and climbout in actual or potential icing conditions; when ice is visible on or shedding from the propeller(s), spinner(s) or leading edge(s); before selecting anti-ice when ice has accumulated; immediately, any time engine fadeout occurs as a possible result of ice ingestion; during approach and landing while in or shortly following flight in actual or potential icing conditions; or where there is water, slush or snow on the runway.”
An operation information (OI) letter issued in November 1998 (about the same time the pilot was hired by American Check Transport) by the engine manufacturer, AlliedSignal, emphasized proper use of engine inlet anti-ice and recommended operators provide additional information on the use of engine ignition in icing conditions. It further stated, “There have been incidents in which TPE engines have flamed out during or following operation in icing conditions. Several dual engine flameouts have occurred. Typically, fadeout events have occurred after departing icing conditions into clear air and especially after descending out of icing conditions into warmer air.”
In addition, the OI letter recommended the installation of automatic ignitions systems. According to the NTSB, N152BK was not equipped, nor was it required to be equipped, with an automatic ignition system. The final report included the following timeline toward an AD issued in May last year.
“The FAA issued a fact-finding focused special certification review (FFFSCR) of the Mitsubishi MU-2B series on June 27, 1997. The FFFSCR contained 10 Airworthiness Directive (AD) recommendations. Recommendation No. 9 stated the following: ‘Require an AD to incorporate the auto relight ignition system per the manufacturer’s Service Bulletin, and require both engines to be modified with the auto relight ignition system.’”
Mitsubishi Heavy Industries issued a mandatory Service Bulletin No. 086/74-002 on Nov. 15, 1995, concerning the installation of an auto-ignition system. The SB stated: “An auto-ignition system shall be installed, in addition to the existing continuous ignition system, to reduce the possibility of engine flameout when icing conditions are encountered and the continuous ignition is not selected.”
The Japanese Civil Aviation Bureau (JCAB) issued TCD 2679A-97 (JCAB equivalent of the FAA Airworthiness Directive) on Feb. 6, 1997, to mandate the installation of the auto-ignition system on A2PC certified MU-2Bs. N152BK was not manufactured under A2PC certification requirements, but under A10SW certification requirements regulated by the FAA. N152BK was not required to have the auto-ignition system installed.
On May 13, 1998, the FAA issued a notice of proposed rulemaking (NPRM) that proposed an auto-ignition (relight) system be installed in all MU-2Bs. On May 5, 2000, the FAA issued Airworthiness Directive (AD) 2000-09-15, which required the installation of an auto-ignition (relight) system on MU-2B series airplanes per the manufacturer’s instructions. Mitsubishi issued SB No. 226B dated Oct. 27, 1997, and SB 086/74-001 dated Nov. 15, 1995, to install the auto-ignition (relight) system.”
While toxicology results did not make it to the final cut of probable cause factors in the accident, the NTSB reported that the autopsy found “extremely high levels of dihydrocodeine in the pilot’s blood.” Dihydrocodeine is a prescription narcotic painkiller use to control moderate to severe pain. In August 1995 the pilot received a special-issuance second-class medical after receiving treatment for a self-disclosed history of drug abuse. According to the NTSB, “The drug testing that this pilot underwent as a consequence of his previous self-disclosed history of drug abuse would not have detected these substances.”