National Transportation Safety Board
Aviation Accident Final Report

 

 

Location:

Kenai, AK

Accident Number:

ANC12LA075

Date & Time:

07/14/2012, 1515 AKD

Registration:

N7154Z

Aircraft:

PIPER PA-18-150

Aircraft Damage:

Substantial

Defining Event:

Powerplant sys/comp malf/fail

Injuries:

2 None

Flight Conducted Under:

Part 91: General Aviation - Personal

Analysis

The pilot, with one passenger aboard, departed in a float-equipped airplane from a remote lake. Shortly after takeoff, about 100 feet above the water, the airplane's engine began to vibrate violently. The pilot reduced engine power, turned the airplane left to avoid trees at the departure end of the lake, and attempted an emergency landing on the lake. The airplane continued to descend, and it subsequently collided with a shallow portion of the lake, sustaining substantial damage to the wings, fuselage, and empennage. A postaccident examination revealed that a 6-inch portion of one propeller blade separated, resulting in a severe imbalance.

An NTSB metallurgical examination of the fractured propeller blade revealed evidence of an unauthorized and undocumented repair of a nearly cylindrical hole, measuring about 0.3 inch in diameter. The examination also revealed areas where a white, opaque, plastic-like filler material, consistent with automotive body repair filler, was used to cover the hole before it was painted over, which subsequently made the unauthorized repair undetectable.

The airplane owner reported that the propeller was already installed when he recently purchased the airplane. In addition, no logbook entry was found that would have indicated any damage, repairs, modifications, or a propeller assembly installation.

 

 

 

 

 

 

 

 

Probable Cause and Findings

The National Transportation Safety Board determines the probable cause(s) of this accident to be:
The in-flight separation of a propeller tip due to an unauthorized and undocumented propeller repair.

Findings

Aircraft

Propeller assembly - Fatigue/wear/corrosion (Cause)

Personnel issues

Incorrect action selection - Maintenance personnel (Cause)

Factual Information

HISTORY OF FLIGHT

On July 14, 2012, about 1515 Alaska daylight time, a float-equipped Piper PA-18-150 airplane, N7154Z, sustained substantial damage during a forced landing shortly after takeoff from a remote lake about 6 miles north of Kenai, Alaska. The airplane was being operated as a visual flight rules (VFR) cross-country personal flight under Title 14, CFR Part 91, when the accident occurred. The pilot and the sole passenger were not injured. Visual meteorological conditions prevailed, and no flight plan had been filed. The flight was en route to the Lake Hood Seaplane Base, Anchorage, Alaska.

During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) on July 15, the pilot reported that just after takeoff, as the airplane climbed to 100 feet above the water, the engine began to vibrate so violently that he was concerned that the engine may possibly separate. He reduced engine power, turned the airplane left to avoid trees at the departure end of the lake, and attempted an emergency landing on the lake. During the turn, the airplane continued to descend, and it subsequently collided with a shallow portion of the lake. The airplane sustained substantial damage to the wings, fuselage, and empennage.

The pilot reported that a postaccident examination revealed that a 6-inch portion of the propeller appeared to be missing. The pilot added that the remaining portion of the fractured propeller blade had a semi-circular hole that was consistent with a high caliber bullet hole. The pilot reported that the tip portion of the blade was not recovered.

The airplane was equipped with a McCauley, two-bladed, fixed pitch, metal propeller, model number DES1A175.

On July 18, the NTSB IIC examined the airplane wreckage after it was recovered to the owner's hangar in Anchorage, and confirmed that a 6-inch portion of one propeller blade tip was missing.

The NTSB IIC's examination revealed a semi-circular hole located at about 1/3 of the chord width from the trailing edge. The semi-circular hole measured about 1/4 inch in diameter.

During an interview with the NTSB IIC on July 18, the owner of the airplane reported that the propeller was the original propeller installed when he purchased the airplane in September of 2011. He added that there was no preaccident damage to the propeller.

A review of the accident airplane's maintenance logs revealed that the serial number of the propeller reportedly installed on the accident airplane did not match the serial number of the one actually installed. In addition, no log book entry was found that would have indicated any damage, repairs, modifications, or propeller assembly installations.

TESTS AND RESEARCH

A sectioned portion of the fractured propeller blade was sent to the NTSB's Materials Laboratory for examination.

A senior Safety Board metallurgist reported that a magnified examination of the fracture face revealed a relatively flat fracture surface, with features consistent with fatigue progression through the aluminum alloys. He added that there was a nearly cylindrical hole, measuring about 0.3 inch in diameter, and oriented about 20 degrees from perpendicular to the flat side of the blade.

A scanning electron microscope (SEM) examination revealed fracture traces indicating fatigue initiation in the vicinity of the corners formed by the intersection of the hole and the flat side of the propeller blade.

When the portion of the propeller blade was received at the NTSB's materials laboratory, both sides of the blade section were painted black. The paint was removed, which revealed shiny surface markings and abrasion patterns, on both the camber and flat sides of the propeller blade. These marking were consistent with local abrasive reworking around the hole. The flat side of the propeller blade had heavy deep scratches in addition to a finely sanded ring around the hole. The unabraded surfaces of the propeller blade had a dull greenish grey appearance consistent with green primer paint. A closer examination of the camber side revealed two areas with a white opaque plastic-like filler material, which is consistent with automotive body repair fillers.

A complete copy of the NTSB's materials laboratory factual report is included in the public docket of this report.

ADDITIONAL INFORMATION

The accident sequence was recorded on the aft-seated passenger's iPhone, and a copy of that recording was sent to the NTSB vehicle recorder laboratory in Washington, DC for review. After a review of key events on the video recording, it was determined that neither the images, nor audio portion of the recording, offered any additional information that had not already been obtained from the pilot. No video group was convened, and no video transcript was created. A summary report of the video is included the public docket for this accident.

 

History of Flight

Initial climb

Powerplant sys/comp malf/fail (Defining event)

Maneuvering-low-alt flying

Loss of control in flight

Uncontrolled descent

Collision with terr/obj (non-CFIT)

 

 

Pilot Information

Certificate:

Airline Transport

Age:

42

Airplane Rating(s):

Multi-engine Land; Single-engine Land; Single-engine Sea

Seat Occupied:

Front

Other Aircraft Rating(s):

None

Restraint Used:

Seatbelt, Shoulder harness

Instrument Rating(s):

Airplane

Second Pilot Present:

No

Instructor Rating(s):

None

Toxicology Performed:

No

Medical Certification:

Class 1 Without Waivers/Limitations

Last FAA Medical Exam:

12/22/2011

Occupational Pilot:

Yes

Last Flight Review or Equivalent:

01/06/2012

Flight Time:

5837 hours (Total, all aircraft), 18.4 hours (Total, this make and model), 3597 hours (Pilot In Command, all aircraft), 76 hours (Last 90 days, all aircraft), 25 hours (Last 30 days, all aircraft), 0.6 hours (Last 24 hours, all aircraft)

 

 

Aircraft and Owner/Operator Information

Aircraft Make:

PIPER

Registration:

N7154Z

Model/Series:

PA-18-150

Aircraft Category:

Airplane

Year of Manufacture:

 

Amateur Built:

No

Airworthiness Certificate:

Normal

Serial Number:

18-8268

Landing Gear Type:

Float

Seats:

2

Date/Type of Last Inspection:

05/05/2012, Annual

Certified Max Gross Wt.:

 

Time Since Last Inspection:

36 Hours

Engines:

1 Reciprocating

Airframe Total Time:

9336 Hours at time of accident

Engine Manufacturer:

LYCOMING

ELT:

C91 installed, not activated

Engine Model/Series:

IO 360 SER

Registered Owner:

MIDNIGHT SUN ADVENTURES

Rated Power:

150 hp

Operator:

Tyler Renner

Operating Certificate(s) Held:

None

 

Meteorological Information and Flight Plan

Conditions at Accident Site:

Visual Conditions

Condition of Light:

Day

Observation Facility, Elevation:

 

Distance from Accident Site:

 

Observation Time:

 

Direction from Accident Site:

 

Lowest Cloud Condition:

Thin Overcast / 4000 ft agl

Visibility

10 Miles

Lowest Ceiling:

Overcast / 5000 ft agl

Visibility (RVR):

 

Wind Speed/Gusts:

Light and Variable /

Turbulence Type Forecast/Actual:

/

Wind Direction:

Variable

Turbulence Severity Forecast/Actual:

/

Altimeter Setting:

 

Temperature/Dew Point:

18°C

Precipitation and Obscuration:

No Obscuration; No Precipitation

Departure Point:

Kenai, AK

Type of Flight Plan Filed:

None

Destination:

Anchorage, AK

Type of Clearance:

None

Departure Time:

1515 ADT

Type of Airspace:

 

 

 

Wreckage and Impact Information

Crew Injuries:

1 None

Aircraft Damage:

Substantial

Passenger Injuries:

1 None

Aircraft Fire:

None

Ground Injuries:

N/A

Aircraft Explosion:

None

Total Injuries:

2 None

Latitude, Longitude:

60.652500, -151.127778 (est)

 


 


Administrative Information

Investigator In Charge (IIC):

Clinton O Johnson

Report Date:

02/03/2014

Additional Participating Persons:

Randy S Smith; Federal Aviation Administration - Operations; Anchorage, AK

Publish Date:

02/03/2014

Investigation Docket:

http://dms.ntsb.gov/pubdms/search/dockList.cfm?mKey=84350