# NTSB MIA93FA200: Beech C35, N5936C, Ocklawaha, FL, September 24, 1993 - Type: NTSB accident investigation - Classification: Accident · Fatal · Field investigation · Final report - Date: September 24, 1993, 16:10 local (20:10 UTC) - Place: Ocklawaha, FL - Location: 29.0459° N, 81.9349° W: Placed by OpenAirDocs: center of Ocklawaha, FL, within about 6 miles (OpenAirDocs) - Nearby events: https://openairdocs.org/map.md?lat=29.0459&lon=-81.9349&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Highest injury: Fatal - Injuries: 1 fatal - Status: Completed, report November 10, 1994 - Report: Approved by Office Director - NTSB case key (mKey): 37356 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=MIA93FA200 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/37356/pdf - Page: https://openairdocs.org/ntsb/MIA93FA200 ## Probable cause FAILURE OF A PROPELLER BLADE FOR AN UNDETERMINED REASON, AND FAILURE OF THE PILOT TO MAINTAIN ADEQUATE AIRSPEED, WHICH RESULTED IN AN INADVERTENT STALL. FACTORS RELATED TO THE ACCIDENT WERE: LOW PASS PERFORMED BY THE PILOT, AND HIS POSSIBLE IMPAIRMENT FROM CONSUMPTION OF ALCOHOL. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, maneuvering - low pass - performed, pilot in command (contributing factor) - impairment(alcohol), pilot in command (contributing factor) - propeller system/accessories - undetermined (cause) - Loss of control - in flight, maneuvering - pull-up - performed, pilot in command - airspeed - not maintained, pilot in command (cause) - stall - inadvertent, pilot in command (cause) - In flight collision with object, descent - uncontrolled - object - tree(s) ## Analysis PURPOSE OF THE FLIGHT WAS TO TEST THE AIRPLANE'S RADIOS. THE PILOT'S WIFE WAS AT THE AIRPARK WITH A PORTABLE VHF RADIO. ACCORDING TO HER, THE AIRPLANE ORBITED THE AIRPARK ABOUT 5 TIMES, THEN FLEW TOWARD AN AREA THE PILOT HAD PREVIOUSLY IDENTIFIED TO HER AS A POSSIBLE FORCED LANDING AREA. SHE SAID THE PILOT CONTACTED HER & ADVISED OF A 'PROBLEM WITH THE PROPELLER.' FOUR WITNESSES SAW THE AIRPLANE MANEUVERING AT LOW ALTITUDE. THEY INDICATED THE PLANE PULLED UP FROM NEAR TREETOP LEVEL, THEN IT ENTERED A DESCENT, HIT TREES, CRASHED & BURNED. ONE WITNESS SAID THE ENGINE SOUNDED LIKE IT WAS RUNNING ROUGH; ANOTHER STATED THE ENGINE POWER STOPPED BEFORE THE AIRPLANE PITCHED NOSE DOWN. NO PREIMPACT FAILURE OF THE ENGINE WAS FOUND. AN EXAM REVEALED THAT 1 OF 2 PROPELLER BLADES HAD SEPARATED DURING THE SEQUENCE. A BRONZE BLADE BUSHING FOR THE SEPARATED BLADE WAS NOT LOCATED. TESTS FOR ETHANOL REVEALED 0.03 GM% IN THE PILOT'S BLOOD, 0.05 GM% IN VITREOUS FLUID, AND 0.05 GM% IN HIS URINE. ALSO, 32 MG/DL OF ACETALDEHYDE WAS DETECTED IN THE PILOT'S BLOOD. ## Factual narrative HISTORY OF FLIGHT On September 24, 1993, about 1610 eastern daylight time, a Beech C35, N5936C, registered to William E. Heifner, crashed near the Woods and Lakes Airpark, Ocklawaha, Florida, while on a 14 CFR Part 91 personal flight. Visual meteorological conditions prevailed at the time and no flight plan was filed. The airplane was destroyed and the private-rated pilot, the sole occupant, was fatally injured. The flight originated from the Woods and Lakes Airpark, Ocklawaha, Florida, about 1550. According to the pilot's wife who was at the airpark at the time of the accident with a portable VHF radio, the purpose of the flight was to test the aircraft's radios. The flight departed, orbited the airpark about five times, then flew to a nearby area which her husband described to her as a possible forced landing area for future reference. Her husband then contacted her and advised of a "problem with the propeller." She thought she heard him say that the propeller hit the ground. She did not witness the accident. One of the witnesses who lives north of the accident site stated that he observed the airplane flying westbound about treetop level then the airplane banked "steeply" to the left. During this time the engine sounded like it oversped. The airplane had completed 180 degrees of the turn when the nose pitched down. The airplane was descending nose and left wing low and after completing about 180 degrees of the turn, he observed the wings roll level. The nose down attitude did not change before impact with trees then the ground. He also stated that he didn't hear any unusual engine sounds nor did he observe anything separate from the airplane. Another witness stated that he observed the accident airplane flying eastbound about 15-20 feet above the tops of trees and stated that the engine sounded normal. The airplane was then observed to bank about 45 degrees to the left and proceeded eastbound, after which he lost sight of the airplane. Shortly thereafter, he heard a "chirping sound" which was similar to tires contacting pavement. He stated that there is a paved road near the area that he thought the airplane had landed on. He then observed the airplane climbing to about 300-400 feet and reported that the engine sounded "rough." He lost sight of the airplane and did not witness the crash. Another witness who is a pilot stated that he observed the airplane flying about 200 feet above ground level (agl) in a climbing left bank with a bank angle between 45 and 60 degrees and a pitch attitude estimated to be 15 to 20 degrees. The airplane climbed to about 450 feet agl when the airplane pitched nose down. He lost sight of the airplane and did not witness the crash. At that time he remarked to himself that the pilot would stall the airplane if he is not careful. He further stated that he doesn't recall if he heard the engine producing power. PERSONNEL INFORMATION Information pertaining to the pilot is contained in the NTSB Factual Report-Aviation. AIRCRAFT INFORMATION Information pertaining to the airplane is contained in the NTSB Factual Report-Aviation, and the NTSB Form 6120.4, Supplements A and B. The installed propeller was purchased on May 13, 1988, however; review of the aircraft and engine logbooks reveal no entry indicating installation of the propeller on the airplane. METEOROLOGICAL INFORMATION Weather information is contained in the NTSB Factual Report-Aviation. WRECKAGE AND IMPACT INFORMATION The airplane came to rest upright on a magnetic heading of 030 degrees with several tree branches laying across the wreckage. Examination of the branches reveal signatures consistent with propeller blade contact. The fuselage from the cockpit area to forward of the ruddervators was consumed by the postcrash fire. Additionally, the wing root section of each wing was damaged by the postcrash fire. The right wing with attached flap and aileron exhibited chordwise crushing. The left wing tip was located adjacent to a tree about 48 feet from the wreckage. Examination of signatures of the left wing aileron revealed evidence that it was slightly down at impact. Examination of the airframe revealed that the ruddervators were installed and the control cables were attached to the bellcranks for the ailerons and ruddervators. The control cables and the control yoke in the cockpit were damaged by postcrash fire. A small quantity of fuel was located in the left wing. The fuel was not tested. Postcrash fire destroyed the cockpit controls. One of the propeller blades was found about 198 feet from the wreckage and the tip of the other propeller blade was found about 75 feet from the wreckage. The propeller assembly was attached to the engine which was partially attached to the airframe. The engine with attached propeller was removed for further examination. Examination of the engine assembly revealed that the magnetos which were attached to the engine, were damaged by the postcrash fire, therefore magneto to engine timing and operational testing of the magnetos could not be accomplished. The carburetor was separated from the engine assembly and was damaged by the postcrash fire. The throttle control cable was attached and the throttle was in the idle position. The mixture control at the carburetor and cable were destroyed by the post crash fire. The carburetor heat control cable was attached to the carburetor heat control valve lever assembly. The carburetor heat control was in the cold position. Postcrash fire damage to the carburetor precluded determination of preimpact failure or malfunction. The spark plugs were removed and the propeller was rotated by hand which revealed crankshaft, camshaft, valve train, and continuity to the accessory section. Differential compression check of each cylinder assembly was not performed. The oil filter was removed, cut open, and examination of the filter element revealed no metal particles. The propeller was removed for further examination. Examination of the propeller revealed that the propeller blade angle was near the low pitch position. The low pitch constant speed switch tripping arm was contacting the constant speed switch actuator cam. Both safety low pitch stop nuts were attached and secured to each control bolt which was secured to each side of the yoke. The drive gear of the electric motor was contacting the ring gear and was nearly contacting the spring stop. The drive gear teeth of the motor and the ring gear were examined; no teeth were missing or damaged. Examination of the separated propeller blade revealed that the apex of the threads on the butt end of the blade were damaged. The paint near the tip of the propeller blade was slightly eroded in the chordwise direction and the tip was bent toward the noncambered side of the blade. Examination of the fracture surfaces of propeller blade tip revealed signatures consistent with overload failure. The propeller blade was bent toward the non-cambered side and the cambered side of the blade was scratched in the chordwise direction. Examination of the inside of the propeller hub of each adjacent surface to the butt end of the blades revealed cracking and impact signatures. The two propeller blade retention nut locks for each blade were installed in the propeller hub assembly. Nondestructive testing of the propeller hub assembly revealed no cracks. The bronze bushing which is placed over the actuator bolt for the separated blade was not located. The electric motor was operationally tested and found to operate in both directions. The constant speed switch assembly was examined and the low pitch tripping arm would not return when pushed to actuate the operating plunger. Continuity of each micro-switch assembly to the electric motor was verified. MEDICAL AND PATHOLOGICAL A postmortem examination of the pilot ## Aircraft - Registration: [N5936C](https://openairdocs.org/deregistered/N5936C-2014-10-29), registration cancelled 2014-10-29, S/N D-3297, built 1952 (OpenAirDocs) - Reported make and model: BEECH C35 - Registry model: [Beech C35](https://openairdocs.org/model/beech-c35) (registry code 1151508) (OpenAirDocs) - Registry engine: [Continental E185 series](https://openairdocs.org/engine/continental-e185-series) (registry code 17014, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: D-3297 - Engines: CONTINENTAL E-185-11 185 horsepower reciprocating - Damage: Destroyed - Fire: On-Ground - Flight: Personal, Part 91 - Registered owner: Heifner, William E. - Airworthiness certificate: Standard, Normal - Last inspection: Annual, May 12, 1993, 16 hours before - Departed: 36X - Destination: 36X - Airport: 36X, Woods And Lakes Airpark ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 71; private; airplane ratings: single-engine land; instrument ratings: airplane; medical: class 3, valid medical--w/ waivers/lim; seat: left; toxicology performed; flight hours: 4,576 total, 4,471 as pilot in command, 11 in the last 90 days, 8 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: 90° at 5 knots - Visibility: 6 statute miles - Lowest ceiling: none - Temperature: 88 °F, dew point 66 °F - Altimeter: 30.00 inHg - Observed at: GNV, 40 nm away ## 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 19930924036279A](https://openairdocs.org/incident/19930924036279A), Sep 24, 1993: Beech C35BEECH, Oklawaha, FL, Destroyed, 1 fatal. Reported propeller problem. May have tried land in field. Stalled steep turn low. Prop flat pitch. Alcohol positive. 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.