Cessna 320D accident near Mammoth Lakes, California, July 4, 1988
On July 4, 1988 at about 11:52 pm local time, a Cessna 320D, registered N9HS, was destroyed in an accident near Mammoth Lakes, California (Mammoth/June Lakes airport). It was a personal flight under general aviation rules (Part 91). 4 people were killed. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The NTSB has not yet published a probable cause for this accident. Investigations usually take one to two years; this page updates when the final report is released.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- July 4, 1988 · about 11:52 pm local time
- Place
- Mammoth Lakes, California · Mammoth/June Lakes · map
- Type
- Accident
- Injuries
- 4 people were killed.
- Weather
- visual conditions (good weather)
- Aircraft
- Cessna 320D · all 320Ds on the register
- Registration
- N9HS · no longer on the register · serial 320D0028
- Damage
- Destroyed
- Flight
- Personal flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
THE PILOT EXECUTED A LEFT (SOUTH) CROSSWIND DEPARTURE TOWARDS HIGHER TERRAIN AFTER DEPARTING RUNWAY 27; THE PLT WAS FOLLOWING A SLOWER SINGLE ENGINE AIRPLANE THAT HAD PRECEDED HIS DEPARTURE. GROUND WITNESSES REPORTED THAT AS THE AIRPLANE APPROACHED THE HIGHER TERRAIN IT ENTERED INTO A LEFT BANKING TURN. DURING THE TURN THE AIRPLANE'S WINGS OSCILLATED RAPIDLY. THE AIRPLANE STALLED AND CRASHED INTO THE CENTER DIVIDER OF CALIF STATE HWY 395 WHICH IS ADJACENT TO & PARALLELS THE EAST/WEST RUNWAY. THE POST ACCIDENT AIRPLANE/ENGINE EXAMINATION DISCLOSED NO EVIDENCE OF ANY PREEXISTING MALFUNCTIONS OR FAILURES. THE AIRPLANE HAD EXCEEDED ITS MAX GROSS T.O. WEIGHT AND IT WAS NEAR ITS AFT CENTER OF GRAVITY LIMITS. THE PLT HAD COMPLAINED TO HIS DR. ABOUT EPISODES OF FORGETFULNESS AND CONFUSION. THE DR. RECOMMENDED THAT THE PILOT CEASE ANY FLYING ACTIVITIES UNTIL HIS MEDICAL CONDITION WAS DIAGNOSED AND TREATED. THE PLT DID NOT HEED THE DRS. ADVICE.
The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.
The factual record from the NTSB's investigation tables, in plain English
Pilot
- Certificate: private
- Ratings: multi-engine land; single-engine land; single-engine sea; instrument: airplane
- Flight time: 1,789 hours in all; 102 in this make and model; 2 in the last 90 days; 2 in the last 30 days
- Medical certificate: Class 3 (valid medical--w/ waivers/lim.)
- Seat: left
The aircraft
- Airframe total time: 2,731 hours
- Last inspection: annual inspection, August 18, 1987; 37 hours since
- Maximum gross weight: 5,200 lb
- Seats: 6
- Landing gear: retractable
- Engine: Continental TSIO-520-B (piston); 0 hours total
The flight
- Departed from: MMH Mammoth Lakes CA at 11:50 pm
- Destination: TOA Torrance CA
- Flight plan: none
- Runway 27, 7,000 ft by 100 ft
Weather at the time
- Light: daylight
- Wind: from 270° at 20 knots, gusting 30
- Visibility: 50 statute miles
- Sky: scat at 8,000 ft
- Temperature: 72°F (22°C), dew point 0°F (-18°C)
- Altimeter: 30.00 inHg
- Observation at 11:50 pm from MMH, 1 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 1 | |||
| Passengers | 3 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
The docket, the folder of records gathered during an investigation (maintenance records, photographs, witness statements, examinations), has not been read from the NTSB for this case yet; the list appears here once it has. Open the docket at the NTSB.
Everything on this page comes from the NTSB's public records. The narrative, probable cause and findings are the NTSB's own words; the coded tables behind the report are written out in plain English, with pilots' ages, home towns and medical details left out. The documents and photographs are the NTSB's docket, shown as the NTSB released them. This site's own text never names anyone involved. A preliminary report can change; the final report usually follows one to two years later, and the page is refreshed when it does.