Fatal Plane Crash In The SanBernardino Hills — Turbulence and Icing

The Flight Home

The Gulfstream 695A was supposed to be on its way home.

The pilot had just completed recurrent training in the aircraft and departed Stockton Metropolitan Airport for Chino, California, on the evening of April 13, 2024.

The plan discussed with the instructor was straightforward: depart early enough to remain west of certain mountainous terrain and reach Chino before darkness.

Instead, the aircraft departed later than planned.

It took a route east of the terrain that had been discussed.

And as darkness arrived, the airplane entered an environment containing turbulence, instrument conditions and moderate to severe icing. (NTSB Data)

The aircraft, N965BC, climbed to Flight Level 250 during cruise.

For most of the flight, everything appeared normal.

Then the descent began.

The airplane encountered turbulence.

The autopilot disengaged.

The pilot began correcting his course while communicating with Southern Californiair traffic control.

Within minutes, the flight would become a fight against ice, altitude, automation and deteriorating aircraft performance.

The airplane eventually entered a rapid descent and struck mountainous terrain northeast of Chino.

The pilot, the only person aboard, was killed.

The final NTSB investigation concluded that the critical mistake was not simply encountering icing.

It was continuing to use the autopilot after entering moderate to severe icing conditions. (NTSB Data)

A Flight That Was Already Running Late

The instructor later told investigators that the return flight had been planned around the weather.

The intended departure time was no later than approximately 6:30 p.m.

The pilot ultimately departed Stockton at approximately 7:03 p.m.

That delay mattered because the weather and lighting conditions were changing.

The NTSB found that the later departure and different route placed the airplane into severe weather conditions after dark. (NTSB Data)

This is an important human-factors element of the accident.

The aircraft was not initially trapped by a sudden weather surprise.

There had been a plan designed to reduce exposure to the most difficult conditions.

Once the aircraft was airborne, the pilot had to manage a progressively more difficult environment.

The Descent

The aircraft cruised at Flight Level 250.

During the descent, near the FLAVR waypoint, ATC asked the pilot to confirm that he was established on the ZIGGY arrival.

The autopilot had already disengaged during turbulence.

ATC cleared the aircraft down to 12,000 feet.

The controller offered vectors to help the pilot rejoin the arrival.

The pilot declined, indicating that he was correcting toward another intersection.

At this stage, the situation was still recoverable.

ATC knew where the aircraft was.

The aircraft was still under control.

But the next phase introduced a much more serious threat: icing. (NTSB Data)

The Icing Warning

ATC relayed a PIREP from another pilot reporting icing.

The pilot of N965BC acknowledged that he was experiencing moderate rime icing.

ATC offered a lower altitude.

He descended toward 8,000 feet.

Then ATC asked whether he remained in icing conditions.

The answer was yes.

There was some improvement, but the airplane was still in icing.

The controller subsequently cleared the aircraft lower, toward 7,400 feet.

The aircraft leveled at approximately 7,200 feet.

At this point, the airplane was flying through an environment in which ice was accumulating on the airframe while the pilot was also dealing with the effects of turbulence and an autopilot problem. (NTSB Data)

The weather forecast had already contained warnings.

The pilot's ForeFlight briefing included G-AIRMETs, PIREPs and METARs, and the potential for moderate icing and supercooled liquid droplets on the descent was included in the available information. (NTSB Data)

Why Structural Ice Is So Dangerous

Icing is not simply a problem because it makes an airplane heavier.

Ice changes the aerodynamic shape of the wing.

It increases drag.

It can reduce lift.

It increases stall speed.

And, critically, ice can change the handling characteristics of an airplane without giving the pilot a simple visual indication of how close the aircraft has moved toward the aerodynamic limit.

The Twin Commander operating guidance specifically warned that severe icing could exceed the capability of the airplane's ice-protection system.

The same guidance warned that the autopilot could mask tactile cues associated with deteriorating handling characteristics. (NTSB Data)

That detail became central to the NTSB investigation.

The Autopilot

When an airplane accumulates ice, the pilot may feel increasing control forces or changes in trim and handling.

Those cues are valuable.

They tell the pilot that the airplane is becoming aerodynamically compromised.

But an autopilot can compensate for some of those changes.

The aircraft can therefore continue flying apparently normally while the underlying aerodynamic margin becomes progressively smaller.

If the autopilot reaches its limits and disconnects suddenly, the pilot may inherit an airplane that is already operating much closer to the stall than expected.

The NTSB's final report found that this was likely part of the sequence involving N965BC.

The Final Minutes

At approximately 8:18 p.m. PDT, ATC stated that the Ontario altimeter was 30.05 inches of mercury.

The pilot asked for the transmission to be repeated and reported that he was having problems with the autopilot.

ATC asked whether he could turn back to the left.

The response was partially received.

Then the controller noticed the airplane descending.

The minimum vectoring altitude in the area was 7,400 feet.

ATC issued a low-altitude alert.

But the aircraft was already rapidly descending.

The final ADS-B points showed a dramatic deterioration.

The airplane went from 6,800 feet to 5,200 feet and then to 2,600 feet while groundspeed remained extremely low.

The aircraft eventually struck mountainous terrain at an elevation of about 2,541 feet. (NTSB Data)

The wreckage was found on a steep ridgeline roughly 20 miles northeast of Chino.

The accident occurred at night in mountainous terrain.

No Engine Failure

The wreckage examination did not identify a pre-existing mechanical failure that would have prevented normal operation.

Both engines were recovered.

The major structural components were identified.

The investigation did not find evidence that an engine failure had forced the aircraft toward the mountains. (NTSB Data)

This distinction is critical.

The aircraft was not destroyed because one engine suddenly failed.

It was not destroyed because the flight controls had mechanically jammed.

The chain was aerodynamic.

The aircraft slowed dramatically.

And it eventually entered an aerodynamic stall from which there was insufficient altitude to recover.

NTSB Probable Cause

The National Transportation Safety Board determined:

— National Transportation Safety Board, WPR24FA124. (NTSB Data)

The Board's findings specifically included incorrect use of the autopilot, pilot decision-making, reliance on equipment, aircraft control and task overload, along with environmental conditions conducive to structural icing. (NTSB Data)

The Human Side

Contemporary reporting described the crash as a nighttime search through difficult weather in the San Bernardino Mountains.

The Los Angeles Times reported that rain and wind initially complicated the search and that authorities located the debris field the following morning. (Los Angeles Times)

The circumstances also explain why the flight attracted attention beyond the technical investigation.

He had substantial flight experience.

The airplane was a capable twin-engine turboprop.

And the flight had been planned specifically to avoid some of the weather and terrain risks.

This was not an example of an inexperienced pilot simply wandering into a storm.

It was a case in which a trained and experienced pilot entered a situation that progressively eroded the safety margin.

Accident Facts

The Broader Safety Lesson

The San Bernardino accident demonstrates why icing should be treated as an aerodynamic threat, not merely a weather inconvenience.

ATC offered vectors.

ATC offered altitude changes.

But every minute spent in icing increased exposure.

The airplane's autopilot provided convenience, but it also reduced the tactile feedback that could have warned the pilot about deteriorating handling.

The most important lesson is therefore simple:

When ice begins accumulating, getting out of the icing environment must become the priority—not simply continuing the original flight while trying to manage the ice.

An airplane can remain mechanically healthy and still become aerodynamically uncontrollable.

At San Bernardino, the aircraft did not run out of engines.

It ran out of aerodynamic margin.

Sources

• Original ATC recording