In the weeks after a medical transport plane crashed in northeast Philadelphia in January within a minute of takeoff, killing seven people, investigators had hoped that the plane’s cockpit voice recorder would contain clues to what had gone wrong.
But after the recorder was recovered from beneath eight feet of soil and debris, those hopes were dashed: The recorder did not record anything during the jet’s final, fatal flight. In fact, it “had likely not been recording audio for several years,” according to a preliminary report released on Thursday by the National Transportation Safety Board.
Jeff Guzzetti, a former accident investigator for the N.T.S.B. and the Federal Aviation Administration, said the finding was “shocking.” Federal rules for medical transport flights on planes registered in the United States require the use of cockpit voice recorders, though the plane in this case was registered in Mexico.
“It really hobbles the investigation at this point, given the lack of other information due to the destruction of this wreckage,” he said.
N.T.S.B. officials did not discuss their four-page report, which contained little information to point to the cause of the crash. It said the flight crew was in communication with air traffic control and that no distress calls from the crew had been received.
Investigators also recovered the computer for the plane’s Enhanced Ground Proximity Warning System, which helps pilots avoid collisions. The computer was still being evaluated to determine whether flight data could be recovered, according to the report.
The small medical transport jet crashed less than a minute after it took off, killing seven people and engulfing homes and vehicles in flames in a densely populated residential and commercial area of northeast Philadelphia.
The disaster occurred on Jan. 31, just two days after the collision of a regional passenger jet and an Army helicopter near Washington, D.C., killed 67 people and became the country’s deadliest air crash in 20 years. The crashes prompted anxiety among air travelers and raised questions about American aviation safety.
Mr. Guzzetti said that even without a functioning voice recorder, investigators could still determine a probable cause of the crash by reviewing other evidence and looking at past crashes with similar flight patterns. A probable cause determination will be included in a final report, which the N.T.S.B. aims to complete within two years.
A spokesman for Jet Rescue Air Ambulance, which operated the carrier and would have been responsible for maintaining its equipment, did not respond to a request for comment Thursday afternoon.
The plane, a Learjet 55, crashed near a busy shopping center, damaging property across several city blocks and injuring 25 people on the ground, one of them fatally, according to city officials.
The Learjet was transporting a pediatric patient from Philadelphia back to her home in Mexico, with a planned refueling stop in Missouri.
The jet took off from Northeast Philadelphia Airport around 6 p.m. It crashed about three miles from the end of the runway.
Air traffic controllers tried several times to communicate with the pilot after the jet took off, but they received no distress calls, according to the report.
After a long silence, according to audio transmissions, a controller said: “We have a lost aircraft. We’re not exactly sure what happened, so we’re trying to figure it out.”
All six people aboard, including the patient’s mother, two pilots, a doctor and a paramedic, were Mexican, Mexico’s Foreign Ministry said.
The patient was 11-year-old Valentina Guzmán Murillo, who had been undergoing treatment for a spinal condition at Shriners Children’s in Philadelphia since late August, according to César Esparza, a family friend.
After the crash, residents were in shock at the devastation: a smoldering crater in a sidewalk outside a department store, homes stained with soot and burned shells of abandoned cars.
A spokesman for the N.T.S.B. said a preliminary report on the deadly collision above the Potomac River may be released next week.
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