National Transportation Safety Board
Aviation Accident Final Report

 

 

Location:

SEVIERVILLE, TN

Accident Number:

MIA99LA181

Date & Time:

06/11/1999, 1700 EDT

Registration:

N49669

Aircraft:

Robinson R-44

Aircraft Damage:

Substantial

Defining Event:

 

Injuries:

3 None

Flight Conducted Under:

Part 91: General Aviation -  - Sightseeing

Analysis

The pilot reported that about 10 minutes into his sightseeing flight, at 400 to 500 feet of altitude, in cruise flight, he heard a noise similar to a shotgun blast and experienced vibration, uncommanded yaw, and low rotor and engine rpm. He regained control and conducted a successful autorotation. Postcrash examination of the helicopter revealed drive train, framework, and fuel tank shrapnel damage originating from a failed transmission forward main driveshaft yoke.  Examination of the failed yoke by the NTSB Materials Laboratory revealed a cracked weld that originated during manufacture.

Probable Cause and Findings

The National Transportation Safety Board determines the probable cause(s) of this accident to be:
The induced fatigue fracture of a component in the engine-to-transmission rotor drive system resulting in a disconnection of the drive system during cruise flight caused by inadequate inspection processes by the manufacturer and the subsequent autorotative emergency descent and forced landing.

Findings

 

Occurrence #1: AIRFRAME/COMPONENT/SYSTEM FAILURE/MALFUNCTION
Phase of Operation: CRUISE

Findings
1. ROTOR DRIVE SYSTEM,ENGINE TO TRANSMISSION DRIVE - CRACKED
2. (C) INADEQUATE SUBSTANTIATION PROCESS - MANUFACTURER
3. ROTOR DRIVE SYSTEM,ENGINE TO TRANSMISSION DRIVE - FATIGUE
4. ROTOR DRIVE SYSTEM,ENGINE TO TRANSMISSION DRIVE - DISCONNECTED
----------

Occurrence #2: FORCED LANDING
Phase of Operation: DESCENT - EMERGENCY

Findings
5. AUTOROTATION - PERFORMED - PILOT IN COMMAND

 

Factual Information

  On June 11, 1999, about 1700 eastern daylight time, a Robinson R-44, N49669, registered to Highway 66 Aviation, LLC, dba Scenic Helicopter Tours, operating as a Title 14 CFR Part 91 sightseeing flight, crashed into a field near Sevierville, Tennessee, after sustaining a main and tail rotor drive failure while in cruise flight. Visual meteorological conditions prevailed and no flight plan was filed. The aircraft sustained substantial damage and the airline transport-rated pilot and two passengers were uninjured. The flight originated about 10  minutes before the flight.

 According to the pilot, he was in cruise flight at 400 to 500 feet agl, when he heard a loud "pop" and the helicopter vibrated and yawed without a control input. Shortly thereafter, he got a low rotor warning horn and light, both main and tail rotor tachometer indications went to zero, and he commenced an autorotation. He landed in a tobacco field, and applied the rotor brake, which had no effect.

 Examination by FAA personnel revealed no damage to the external fuselage; however, removal of the rear cowling revealed (1) the forward yoke of the main drive shaft at the transmission end had failed and was in several pieces,  (2) the tubular framework to the left and below the main drive shaft had been mangled and was in two pieces, (3) a 4-inch by 2-inch puncture of the left fuel tank was present, (4) the double drive belts had been displaced as was their drive pulleys,  (5) the tail rotor drive shaft was sheared and its forward drive shaft yoke had failed,  (6) the tail rotor control tube rod ends had failed. 

 The Robinson Helicopter Factory arranged for shipping the wreckage for NTSB disassembly examination at their Torrance, California, facilities.  Examination of the helicopter's rotor drive systems revealed that the sequence of failure events began with engine-to-transmission drive shaft excessive end play at the transmission end. The component that supports the drive shaft in that location is the forward main rotor drive yoke, part number C908-1. The component was subsequently removed and shipped to the NTSB Materials Laboratory, Washington, D.C. for further examination.

 According to the NTSB Materials Laboratory, the yoke failure was an induced fatigue fracture originating from a defective inertia weld at fabrication. Paint found within the crack confirmed the defect existed since manufacture, and probably occurred as a result of a straightening operation. Although the component is subjected to magnetic particle inspection after straightening and before finishing, plating, and painting, this defective component had been allowed to be installed. The report from the NTSB Materials Laboratory is included under, "Materials Laboratory Factual Report".

 

 

 

Pilot Information

Certificate:

Airline Transport; Commercial

Age:

46, Male

Airplane Rating(s):

Multi-engine Land; Single-engine Land

Seat Occupied:

Right

Other Aircraft Rating(s):

Helicopter

Restraint Used:

Seatbelt, Shoulder harness

Instrument Rating(s):

Airplane; Helicopter

Second Pilot Present:

No

Instructor Rating(s):

Helicopter

Toxicology Performed:

No

Medical Certification:

Class 2 Valid Medical--w/ waivers/lim.

Last FAA Medical Exam:

04/01/1999

Occupational Pilot:

 

Last Flight Review or Equivalent:

 

Flight Time:

9000 hours (Total, all aircraft), 100 hours (Total, this make and model), 8700 hours (Pilot In Command, all aircraft), 70 hours (Last 90 days, all aircraft), 20 hours (Last 30 days, all aircraft), 1 hours (Last 24 hours, all aircraft)

 

 

Aircraft and Owner/Operator Information

Aircraft Make:

Robinson

Registration:

N49669

Model/Series:

R-44 R-44

Aircraft Category:

Helicopter

Year of Manufacture:

 

Amateur Built:

No

Airworthiness Certificate:

Normal

Serial Number:

562

Landing Gear Type:

Skid

Seats:

4

Date/Type of Last Inspection:

05/19/1999, Annual

Certified Max Gross Wt.:

2400 lbs

Time Since Last Inspection:

80 Hours

Engines:

1 Reciprocating

Airframe Total Time:

279 Hours

Engine Manufacturer:

Lycoming

ELT:

Installed, activated, did not aid in locating accident

Engine Model/Series:

O-540-F1B5

Registered Owner:

HWY 66 AVIATION LLC

Rated Power:

260 hp

Operator:

 

Operating Certificate(s) Held:

None

Operator Does Business As:

RAMBO HELICOPTER CHARTER, INC.

Operator Designator Code:

 

 

Meteorological Information and Flight Plan

Conditions at Accident Site:

Visual Conditions

Condition of Light:

Day

Observation Facility, Elevation:

TYS, 981 ft msl

Distance from Accident Site:

24 Nautical Miles

Observation Time:

1653 EDT

Direction from Accident Site:

262°

Lowest Cloud Condition:

Scattered / 6500 ft agl

Visibility

9 Miles

Lowest Ceiling:

None / 0 ft agl

Visibility (RVR):

0 ft

Wind Speed/Gusts:

6 knots /

Turbulence Type Forecast/Actual:

/

Wind Direction:

60°

Turbulence Severity Forecast/Actual:

/

Altimeter Setting:

30 inches Hg

Temperature/Dew Point:

33°C / 19°C

Precipitation and Obscuration:

 

Departure Point:

SEVIERVILLE, TN

Type of Flight Plan Filed:

None

Destination:

 

Type of Clearance:

None

Departure Time:

1450 EDT

Type of Airspace:

Class G

 

 

Wreckage and Impact Information

Crew Injuries:

1 None

Aircraft Damage:

Substantial

Passenger Injuries:

2 None

Aircraft Fire:

None

Ground Injuries:

N/A

Aircraft Explosion:

None

Total Injuries:

3 None

Latitude, Longitude:

 

 


 


Administrative Information

Investigator In Charge (IIC):

ALAN       C STONE

Report Date:

12/04/2000

Additional Participating Persons:

ROCKY   DAVIDSON; NASHVILLE, TN

PAM   CHARLES; NASHVILLE, TN

Publish Date:

 

Investigation Docket:

NTSB accident and incident dockets serve as permanent archival information for the NTSB’s investigations. Dockets released prior to June 1, 2009 are publicly available from the NTSB’s Record Management Division at pubinq@ntsb.gov, or at 800-877-6799. Dockets released after this date are available at http://dms.ntsb.gov/pubdms/.