Sill/Thomas LONG EZ N977ST
20 June 1993 · Lone Pine, California, United States · Minor injuries
Summary
On 20 June 1993 at about 21:00 local time, a Sill/Thomas LONG EZ registered N977ST was involved in an accident near Lone Pine, California, United States. One person was on board and one had minor injuries. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.
The record
- Date
- at 21:00
- Classification
- Accident
- Location
- Lone Pine, California, United States
- Coordinates
- 36.8292, -118.2409
- Aircraft
- Sill/Thomas LONG EZ
- Registration
- N977ST
- Category
- Airplane
- Engines
- 1
- Operator
- Not recorded
- Operating rule
- Part 91: General Aviation
- Purpose of flight
- Personal
- Phase of flight
- Not recorded
- Route
- Mammoth → Van Nuys
- Aircraft damage
- Substantial
- Weather
- VMC
- Light
- Day
- NTSB number
- LAX93LA263
People
1 person had minor injuries.
| On board | Died | Serious | Minor | Uninjured |
|---|---|---|---|---|
| 1 | 0 | 0 | 1 | 0 |
Probable cause
the failure of the number four cylinder exhaust valve due to excessive heat exposure and lack of maintenance.
Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.
Read the full NTSB narrative
THE PILOT STATED THAT HE WAS IN LEVEL CRUISE AT 10,500 FEET MSL WHEN THE ENGINE SUDDENLY QUIT. HE MADE A FORCED LANDING ON OWENS DRY LAKE, WHICH WAS SOFT FROM RECENT RAINS. THE NOSE GEAR COLLAPSED AND THE AIRPLANE NOSED OVER INVERTED. POST CRASH EXAMINATION OF THE ENGINE REVEALED THAT THE EXHAUST VALVE HAD FAILED IN THE NUMBER FOUR CYLINDER. THE VALVE HEAD HAD SEPARATED FROM THE VALVE STEM. EXAMINATION OF THE VALVE SPRING AREA REVEALED OVERHEAT SIGNATURES IN THE FORM OF OIL COKING AND OXIDIZATION, AND CARBON DEPOSITS. THE NTSB METALLURGY LABORATORY FOUND THAT THE VALVE STEM WAS DEVOID OF CHROME PLATING IN THE AREA OF THE FRACTURE, WAS REDUCED IN DIAMETER, AND HAD A SIGNIFICANTLY DECREASED MATERIAL HARDNESS, ALL PRINCIPALLY DUE TO HEAT EXPOSURE. POST ACCIDENT EXAMINATION OF THE LOG BOOKS AND THE FAA OPERATING LIMITATIONS REVEALED NO RECORD OF A REQUIRED CONDITION (ANNUAL EQUIVALENT) INSPECTION SINCE THE AIRCRAFT WAS PLACED INTO SERVICE. EXAMINATION OF THE ENGINE REVEALED MANY AREAS OF SUBSTANDARD MAINTENANCE PRACTICES.
Quoted verbatim from the NTSB record.
Other accidents in this area
| Date | Aircraft | Location | Operator | Outcome | Died |
|---|---|---|---|---|---|
| 26 Jul 1993 | Cessna 310H | Lancaster, California, United States | Yehiem Konski | Fatal | 6 |
| 14 Nov 1993 | Cessna 182 | Colusa, California, United States | - | No injuries | - |
| 20 Jan 1993 | Cessna 172P | Sun City, California, United States | Hiser Helicopters, Inc. | Fatal | 1 |
| 31 Jul 1993 | Robinson R44 | El Monte, California, United States | Benjamin F. Venti, SR. | Fatal | 3 |
| 17 Nov 1993 | Piper PA-38-112 | Fresno, California, United States | - | No injuries | - |
| 21 Jan 1993 | Beechcraft A35 | Tulare, California, United States | Rent and Lease Programs | Fatal | 2 |