ANC23LA053

NTSB accident investigation · Aeronca 7DC · Ninilchik, AK · July 13, 2023

Accident · No injuriesClass 3 · LimitedFinal report
Date
July 12, 2023, 16:20 local (Jul 13, 2023, 00:20 UTC)
Place
Ninilchik, AK · Highway
Injuries
2 uninjured
Damage
Substantial damage
Phase of flight
Enroute
Aircraft
N83391Aeronca 7DC
Defining event
Enroute: Loss of engine power (total)
Weather
Visual (VMC) · Day
Status
Completed
Report
Approved by Office Director
Investigation class
Class 3
NTSB office
Alaska Regional Office
Parties
FAA
FAA report
20230712014669A
Case key
192670

From the NTSB’s public API. By law, NTSB reports can’t be used as evidence in lawsuits over the accident.

On this page

Probable cause

A total loss of engine power due to a shift of a crankshaft main bearing, which resulted in a lack of lubrication and subsequent overheating and failure of the engine crankshaft.

Findings · 2

NTSB’s coded findings. Those marked are part of the probable cause; the rest are factors or other findings. Under each, the cases with the same finding.

Engine (reciprocating): recip eng oil sysAircraft › Aircraft power plant · Damaged/degradedAeronca 7DC: 1 caseAll aircraft: 130 casesProbable cause
Engine (reciprocating): recip engine power sectionAircraft › Aircraft power plant · Damaged/degradedAeronca 7DC: 1 caseAll aircraft: 233 casesProbable cause

Sequence of events

The events NTSB coded, in order, by phase of flight. The defining event is the one that best describes the accident. Under each, the cases with the same event anywhere in their sequence.

Analysis

While en route during a scenic flight, the pilot noticed the engine was not making enough power for the set power setting and the oil pressure and oil temperature gauges both indicated zero. He started a climb to clear rising terrain when the engine started to vibrate violently and then the engine lost all power. The pilot made a forced landing on to a road and, after touching down, veered to avoid traffic. The airplane impacted a guardrail and nosed over, sustaining substantial damage to the fuselage and wings. A postaccident examination of the engine revealed that the crankshaft’s No. 1 main bearing had spun, smearing metal into the crankcase and blocking the oil port. Numerous fragments of bearing material were found inside the engine. Based on the available information, it is likely that the shift of the No. 1 main bearing resulted in a lack of lubrication and subsequent failure of the engine. The reason for the bearing shift was not determined; the owner was not able to provide maintenance records for the engine.

Factual narrative

On July 12, 2023, about 1620 Alaska daylight time, a Aeronca 7DC airplane, N83391 sustained substantial damage when it was involved in an accident near Ninilchik, Alaska. The pilot and passenger were not injured. The airplane was operated by the pilot as a Title 14 Code of Federal Regulations Part 91 personal flight. Pilot reported that he and a friend were on a scenic flight from the Homer Airport (HOM), Homer, Alaska, to the Soldotna Airport (SXQ), Soldotna, Alaska. En route he noticed the engine was not making enough power for the set power setting. At full throttle the engine was only producing about 2,400 rpm. He ran through checklist memory items for loss of engine power, which included applying carburetor heat; however, there was no change in the engine power. The pilot also opened both wing tanks to increase fuel in the header tank, which also resulted in no change. He then noticed the oil pressure gauge and oil temperature gauge both indicated zero. The pilot initiated a climb to clear rising terrain when the engine started to vibrate violently and then lost all power. He initiated a forced landing on to a road and, after touching down, he veered left to avoid cars. The airplane impacted a guardrail and then nosed over. The airplane sustained substantial damage to the fuselage and wings. A postaccident examination of the engine revealed that the crankshaft’s No. 1 main bearing had spun, smearing metal into the crankcase and blocking the oil port. Numerous fragments of bearing material were found inside the case. The owner was not able to provide maintenance records for the engine.

Aircraft

Registration
N83391
Reported as
Aeronca 7DC
Category
Airplane
Serial number
7AC2058
Built
1946
Airframe hours
4,542.6
Engine
Continental C-85-12, 96 horsepower, reciprocating
Damage
Substantial damage
Flight
Personal · Part 91
Airworthiness certificate
Standard, Normal
Last inspection
Annual · March 3, 2023 · 55 hours before
Departed
PAHO · Homer, AK
Destination
PASX · Soldotna, AK
Airport
PASX · Soldotna
Equipment
Electronic flight bag or handheld device

Matched to the registry by N-number and the event date; the registry’s history has gaps, so older matches can be wrong. Compare the reported make and model.

Flight crew

As NTSB recorded them. NTSB leaves out names.

Role
Pilot
Age
26
Injuries
None
Certificate
Private
Airplane ratings
Single-engine land
Medical
Class 1, With waivers/limitations
Seat
Front
Restraint
3-point
Flight hours
79.9 total · 17.9 in this make and model · 23.5 as pilot in command · 50.7 in the last 90 days · 21.9 in the last 30 days · 0 in the last 24 hours

Weather

Conditions
Visual (VMC) · Day
Wind
250° at 9 knots
Visibility
10 statute miles
Lowest ceiling
5,000 ft broken
Temperature
57 °F, dew point 54 °F
Altimeter
30.16 inHg
Observed at
PAHO

Docket · 4

The files NTSB released with the investigation on May 16, 2024, on NTSB’s docket system: statements, records, photos and specialists’ reports. 6.8 MB in all.

FAA reports on this event · 1

The FAA’s own accident and incident reports, matched to the aircraft by N-number and date.

Other investigations on N83391 · 1

Matched to the same aircraft by N-number and date.