SAN FRANCISCO (CBS SF/AP) — The National Transportation Safety Board is urging faster action to correct unsafe wiring found in a type of small airplane that crashed in Northern California last summer, killing all four on board the medical transport flight.
The Piper PA-31T was carrying a flight nurse, transport medic and patient from Crescent City, near the Oregon border, to Oakland on July 29 when the pilot reported smoke in the cockpit and declared an emergency.
The transportation board issued an urgent safety recommendation Monday, asking the Federal Aviation Administration to issue an emergency directive that would require mandatory action and a shorter timeline for addressing the problem.
The transportation board’s recommendation is based on preliminary findings in an ongoing investigation of what caused the transport plane to break apart. Rescue teams found the wreckage in Humboldt County about 280 miles north of San Francisco.
Evidence indicates that an in-flight fire occurred in an area where electrical wires and adjacent hydraulic lines may have been in contact, a press release states. Investigation of six other planes showed electrical lines in direct contact with hydraulic lines, which could chafe and then arc, causing a fire.
“We think it’s a dangerous situation having electrical lines next to hydraulic lines,” said NTSB spokesman Eric Weiss, adding that the investigation is ongoing and no cause has been determined.
FAA spokesman Ian Gregor said in an email Tuesday that the agency is “actively working with Piper on possible additional safety actions” and that it had issued a “special airworthiness information bulletin” in December, noting the problem.
The special bulletin recommends inspections at the aircraft’s next scheduled maintenance visit.
The July crash came as the Federal Aviation Administration continues its efforts to improve the safety of the aircraft known as air ambulances. It began that effort after a series of deadly crashes. In 2008, there were five accidents that killed 21 people.
Piper Aircraft spokeswoman Jacqueline Carlon said in an email that the company has issued a “mandatory service bulletin” for operators. It is working with both agencies, she said.
There are more than 300 31T-series planes registered with the Federal Aviation Administration.
The National Transportation Safety Board traveled to the scene of this accident.
Aviation Accident Preliminary Report - National Transportation Safety Board: https://app.ntsb.gov/pdf
FAA Flight Standards District Office: FAA Oakland FSDO-27
NTSB Identification: WPR16FA153
Nonscheduled 14 CFR Part 135: Air Taxi & Commuter
Accident occurred Friday, July 29, 2016 in McKinleyville, CA
Aircraft: PIPER PA-31T, registration: N661TC
Injuries: 4 Fatal.
This is preliminary information, subject to change, and may contain errors. Any errors in this report will be corrected when the final report has been completed. NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.
On July 29, 2016, about 0105 Pacific daylight time, a twin-engine, turbine-powered, Piper PA-31T Cheyenne II airplane, N661TC, reported smoke in the cockpit and subsequently sustained an in-flight breakup and collision with tree-covered terrain near Arcata/Eureka Airport, McKinleyville, California. The accident airplane was being operated by Cal-Ore Life Flight as an instrument flight rules (IFR) air transport medical flight under the provisions of Title 14, CFR Part 135. The airline transport pilot, two medical personnel, and one patient were fatally injured; the airplane sustained substantial damage. Dark night, instrument meteorological conditions prevailed. The flight departed Crescent City, California, at 0045, destined for Oakland International Airport, Oakland, California
A preliminary review of archived radar and voice communication data from the Federal Aviation Administration (FAA) revealed that at 0058:12, as the airplane reached an altitude of about 15,000 feet msl, the accident pilot contacted Seattle air route traffic control center (ARTCC) and stated that he was going to turn back to Crescent City due to a smell of smoke in the cockpit.
At 0058:26, the ARTCC specialist on duty cleared the accident airplane direct to the Crescent City Airport, issued him a descent clearance to 9,000 feet, and told him to let her know if he needed anything else.
At 0058:41, the accident pilot said "okay," and he stated that it looked like he was going to lose some power shortly, and said he would keep her posted as long as he could.
At 0058:52, the ARTCC specialist issued the Crescent City altimeter of 29.98, and then requested the total number of occupants on board, and how much fuel was remaining.
At 0059:07, the accident pilot stated that he had smoke in the cockpit, declared an emergency, said he was depressurizing and was heading back to Crescent City.
At 0059:21, the accident pilot asked the ARTCC specialist to call the fire department to have them standing by upon arrival.
At 0059:25, the ARTCC specialist then acknowledged that crash rescue would be standing by at the Crescent City Airport, and she again asked how many people were on board.
At 0059:27, the accident pilot stated that he had three on board. There were no further communications received from the accident airplane despite multiple attempts by the ARTCC specialist on duty.
During a telephone conversation with an National Transportation Safety Board (NTSB) investigator, a witness located near Cookson Camp, Arcata, California, reported that in the early morning hours of July 29, she heard an airplane circling overhead before it eventually flew westward, which was followed by about 15 seconds of silence. While looking out the window of her tent, she saw a large dome shaped flash to the west, followed by another flash and a loud rumble.
The NTSB IIC, along with another NTSB investigator, two Federal Aviation Administration safety inspectors from the Oakland Flight Standards District Office (FSDO), two representatives from the Humboldt County Sheriff's Office, representatives from Cal-Ore Life Flight, and an Piper Aircraft air safety investigator reached the accident site on the afternoon of July 30. The accident site was located in an area of brush and heavily forested terrain. Large portions of the burned and fragmented airplane were scattered along a debris path oriented along a magnetic heading of 354 degrees, which measured about 2,400 feet in length. The fuselage, inboard and outboard sections of the wings, vertical tail, and portions of one horizontal stabilizer, were located in separate locations and exhibited minimal impact damage. Both inboard sections of the wings exhibited postcrash fire damage.
The fuselage and empennage came to rest on its left side and facing the direction of travel. The instrument panel and cockpit exhibited extensive impact damage. The cabin area of the fuselage was largely intact. Evidence of thermal damage was present in the forward section of the fuselage. A section of the forward fuselage, wiring, and associated components were removed and sent to the NTSB Materials Laboratory in Washington, D.C., for further examination.
Both engines separated from their respective engine firewalls and sustained impact damage, however; neither engine exhibited any sign of thermal damage.
Control continuity could not be established due to numerous fractures in the system, missing cabling and flight control surfaces; however, all the fractures that were identified exhibited features consistent with tension overload.
The closest weather reporting facility is Arcata/Eureka Airport (KACV), McKinleyville, located approximately 6 miles southwest of the accident site. At 0107, an aviation routine weather report (METAR) at KACV, reported wind 180 degrees at 4 knots; visibility 1/2 statute miles, mist; runway 32 visual range 4,500 feet variable to greater than 6,000 feet, overcast clouds 200 feet; temperature 55 degrees F; dew point 54 degrees F; altimeter 29.85 inHg.