# NTSB LAX93LA310: Nall Varieze, N75PD, Newark, CA, July 31, 1993 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Limited investigation · Final report - Date: July 30, 1993, 19:32 local (Jul 31, 1993, 02:32 UTC) - Place: Newark, CA - Coordinates: 37.510936, -122.039482 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=37.5109&lon=-122.0395&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: Minor injuries - Injuries: 1 minor - Status: Completed, report September 26, 1994 - Report: Approved by Office Director - NTSB case key (mKey): 28440 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX93LA310 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/28440/pdf - Page: https://openairdocs.org/ntsb/LAX93LA310 ## Probable cause IMPROPER ANNUAL INSPECTION PERFORMED BY OTHER MAINTENANCE PERSONNEL. FACTORS RELATING TO THIS ACCIDENT WERE THE LOOSE EXHAUST BOLTS. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, descent - propeller system/accessories,blade - separation - engine installation,mounting bolt - loose (contributing factor) - engine installation,mounting bolt - separation (contributing factor) - maintenance,annual inspection - improper, other maintenance personnel (cause) - Forced landing, descent - emergency - In flight collision with object, descent - emergency - object - fence ## Analysis WHILE DESCENDING TOWARD THE DESTINATION AIRPORT, AN EXHAUST STACK ATTACH BOLT SEPARATED, ENTERED INTO THE PROPELLER ROTATIONAL PLANE CAUSING ONE PROPELLER BLADE TO SEPARATE. THE AIRPLANE COLLIDED WITH A FENCE DURING THE SUBSEQUENT FORCED LANDING. EXAMINATION OF THE REMAINING ATTACH BOLTS REVEALED SEVERAL BOLTS TO BE LOOSE. ## Factual narrative On July 30, 1993, about 1932 hours Pacific daylight time, a homebuilt P.D. Nall Varieze airplane, N75PD, collided with a barbed wire fence while executing an emergency landing to an open field at Newark, California. The emergency landing was precipitated by a severe vibration, a partial loss of a propeller blade, and an ultimate loss of engine power. The pilot was conducting a visual flight rules personal flight to Palo Alto Airport, Palo Alto, California. The airplane, registered to and operated by the pilot, was destroyed and there was no post-impact fire. The certificated private pilot, the sole occupant, sustained minor injuries. Visual meteorological conditions prevailed. The flight originated at Cameron Airpark, Cameron Park, California, at about 1845 hours. The pilot reported in a telephone interview conducted on August 3, 1993, that when the flight was about 6 miles north of Palo Alto Airport, the airplane suddenly began to vibrate violently and the engine power simultaneously reduced to about 50 percent of its available power. The pilot immediately selected a road to execute a precautionary landing. During the approach to the road, the engine sustained a total loss of power. The airplane's altitude was insufficient to land on the road due to trees crossing the airplane's flight path. The pilot selected a corn field, but collided with a barbed wire fence during the approach. The pilot reported that part of one propeller blade was not found. He also stated that extensive engine maintenance was performed about 3 flight hours preceding the accident. Mr. Roy Hutto, Aviation Safety Inspector [Airworthiness], examined the airplane's engine on August 19, 1993, at the registered owner's facility. He reported that he established continuity of the engine gear and valve train assembly and that compression appeared to be normal. He noted, however, that one bolt/screw was missing on the right side of the engine. This bolt/screw attached the exhaust bracket to the valve cover. The remaining screws in the valve covers had holes for safety wire, but no safety wire was present. Inspector Hutto stated that "... these screws had star-type lock washers that were so old and reused, they did not appear to be locking. Most of the rocker arm cover screws were tight, but three or four were somewhat loose." Both magnetos produced spark during hand rotation of their respective drive shafts. The impulse couplings operated normally. The wooden propeller, a Serba 60 X 68, had one blade that was splintered. The splintered blade exhibited at least one screw indentation on its leading edge. The splinter, however, appeared to originate from the trailing edge. Inspector Hutto, at the request of the Safety Board, sent the propeller to Sensenich Propeller, Inc., Lititz, Pennsylvania, for examination. Mr. Kenneth C. DeGraff, Chief Propeller Engineer, Sensenich, reported that: 1) Several indentations were found on the leading edge and flat face of both blades. After further examination of the indentations, it was determined to have been caused by machine screws and/or bolts which had entered the propeller plane during rotation. 2) One (1) failed edge glued joint was found on the #1 [the splintered propeller blade]. This was an adhesive failure as indicated by a smooth surface at the failed joint. Mr. DeGraff concluded: Although a failed edge glue joint was found in the failed propeller, it is our opinion that this did not cause a propeller blade failure. Based on the extensive cracking from tip to hub, it is our opinion that the damage was a result of an impact with the ground. ## Aircraft - Registration: [N75PD](https://openairdocs.org/deregistered/N75PD-1994-05-02), registration cancelled 1994-05-02, S/N 1406 (OpenAirDocs) - Reported make and model: NALL VARIEZE - Registry model: [Nall P T VARIEZE](https://openairdocs.org/model/nall-p-t-varieze) (registry code 05609CC) (OpenAirDocs) - Category: Airplane, amateur-built - Serial number: 1406 - Engines: CONTINENTAL C-90-8F 90 horsepower reciprocating - Damage: Destroyed - Flight: Personal, Part 91 - Registered owner: Fletcher, Henry H. - Airworthiness certificate: Special, Experimental (Special) - Last inspection: Annual, June 26, 1993, 6 hours before - Departed: O61, CAMERON PARK, CA - Destination: PAO, PALO ALTO, CA - Airport: PAO, Palo Alto ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 33; private; airplane ratings: single-engine land; medical: class 3, valid medical--no waivers/lim.; seat: front ## Weather - Conditions: Visual (VMC), Day - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 75 °F ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Accident 19930730027179A](https://openairdocs.org/incident/19930730027179A), Jul 30, 1993: Amtrru VARIEZE, Palo Alto, CA, Destroyed. During descent to airport exhaust stack bolt came out. Struck prop. Hit fence. Other loosed prop bolts. From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.