[Editor’s Note: We received this from one of our reader’s. Thank you for your contribution. This Civil Air Patrol plane crash in California Wing was caused by pilot error.]
While flying on a moonless night in mountainous terrain to an airport in a mountain valley, the [N7292W] aircraft encountered mountain wave conditions and downdrafts in the 500 to 1,000 foot-per-minute range, which resulted in a collision with mountainous terrain. The two-man aircrew participated in a Civil Air Patrol (CAP) search and rescue training exercise (SAREX) being held over the weekend, and had flown from the mountain valley airport along the accident route of flight that morning. The CAP group was informed that high winds were expected the following day and flying operations might be cancelled. The aircrew decided to return to their home base in a small mountain town (elev: 6,748 feet) instead of staying at the SAREX base for the night.
The aircrew had commented to the CAP Incident Commander that they had experienced some moderate turbulence on the flight out of the mountains severe enough to have their heads hit the cockpit canopy and toss a cell phone out of the passenger’s shirt pocket. They departed the SAREX base at night and there was no moon illumination at the time they approached the 8,000-9,000 foot mountain ridgeline. The airplane approached the mountains at 10,300 feet, and shortly thereafter entered a mountain wave, and experienced turbulence and downdrafts. Radar data showed that the airplane steadily descended through 8,000 feet during the last 4 minutes of the flight.
The airplane impacted the side of the mountain at the 6,970 foot elevation with low energy, in a very steep left turn; left wing down. Analysis of the weather conditions established that mountain wave conditions existed at 9,000 feet with a wavelength of 2.79 miles, amplitude of 717 feet, and a maximum vertical velocity of 1,185 fpm. This wave had a potential for moderate to severe turbulence. There is no record that the pilot requested or received a weather briefing. At the cruise altitude of the airplane, the performance charts show that it had a maximum climb capability of about 400 feet per minute.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The pilots inadequate pre-flight planning and intentional flight into known adverse weather conditions. Contributing to this accident was the fact that it was a dark night with no moon illumination.