Smoke or gas was observed in the cockpit of a Learjet 35A by flight crewmembers shortly before it crashed earlier this month just off of San Clemente Island in California.
The aircraft, operated by a naval contractor, was being trailed by a second Learjet to participate in military training exercises in Warning Area 291 on May 10, according to an NTSB preliminary report released on Friday. Two pilots and a third civilian crewmember are missing and presumed dead in the crash.
The accident aircraft was using the callsign FENIX01 and was closely trailed in formation by FENIX02. Shortly after entering the warning area, the crew of the trailing aircraft noticed the lead aircraft’s flaps partially deploy at 15,000 feet.
After they notified FENIX01, they noticed the flaps retract.
“Seconds later, the aircrew of FENIX01 radioed that they detected an odor in the cabin,” the preliminary report states. “The aircrew of FENIX02 then radioed that observed white or gray colored ‘smoke or gas’ coming from the ‘left side AFT Cabin area.’ Unidentified fluid was also observed trailing the airplane. At this point the lead airplane was not maintaining heading or altitude.”
Then the crew in the trailing plane saw flames coming from around the aft equipment door. They told the crew of the lead Learjet, who then declared an emergency with intentions to land at San Clemente Island Naval Auxiliary Landing Field (NUC).
FENIX02 took over as lead, maneuvering in front of FENIX01, to lead them to the airfield. They last observed and heard radio transmissions from FENIX01 as they descended through about 9,000 feet, according to the NTSB prelim.
“Automatic Dependent Surveillance–Broadcast (ADS-B) data showed only the lead airplane’s track until after the accident occurred, and FENIX02 turned their transponder on,” the report states. “The data showed that FENIX01 proceeded on about a 165° heading until about 30 miles south of NUC, where the airplane began a left turn. FENIX01 subsequently made a series of descending turns before the data ended. The last recorded data point showed the airplane at 1,338 ft and heading northwest about a half-mile off the southwest side of San Clemente Island.
Wreckage of the Learjet 35A was found four miles northwest of the last recorded ADS-B data point and one mile offshore in about 300 feet of water.
A visual inspection was conducted using a remotely operated vehicle, showing the remaining debris “was highly fragmented and evidence of a preimpact fire was visible on portions of the wreckage.”
Information in a preliminary report is subject to change. It typically takes around a year for NTSB reports to be finalized.