Lifeflight Refuel Airport
Aircraft Accident/Incident Report

Fresno, Texas 77545
Saturday, July 17, 1999 12:31 CDT

NTSB Narrative Summary Released at Completion of Accident

The helicopter was making a VFR approach to a fueling site when witnesses observed components of the main rotor system separate from the helicopter. Subsequently, the helicopter entered an uncontrollable descent and impacted the ground. Examination of the helicopter revealed that one of the four main rotor blades separated due to the failure of the tension-torsion strap (T-T strap), which secured the blade to the main rotor head. Examination of the failed T-T strap revealed that the polyurethane protective coating had debonded from a portion of the strap allowing corrosive agents, including carbon, sulphur, and chlorine into the strap. The strap separated as a result of fatigue cracking of the wires making up the strap. The fatigue cracking emanated from corrosion pits and deposits that were introduced to the strap when the polyurethane protective coating debonded. The T-T strap had accumulated a total of 7,815.3 flight hours and 35,971 flights at the time that it failed. It had been in service since the helicopter was manufactured in 1987. Following the accident, a life limit of 120 months or 25,000 flights (whichever comes first) was established for the T-T straps.

NTSB Probable Cause Narrative

the loss of control during approach due to the corrosion of the T-T strap which resulted in fatigue cracking and subsequent separation of the strap and main rotor blade from the helicopter.

Event Information

Type of Event Accident
Event Date 7/17/1999
Event Day of the Week Saturday
Time of Event 1231
Event Time Zone Central Daylight Time
Event City FRESNO
Event State TEXAS
Event Country --
Zipcode of the event site 77545
Event Date Year 1999
Event Date Month 7
MidAir Collision Indicator No
On Ground Collision occurred ? No
Event Location Latitude --
Event Location Longitude --
Event Location Airport LIFEFLIGHT REFUEL
Event Location Nearest Airport ID TE11
Indicates whether the acc/inc occurred off or on an airport Off Airport/Airstrip
Distance from airport in statute miles --
Degrees magnetic from airport --
Airport Elevation 68
Weather Briefing Completeness Unknown
Investigator's weather source Weather Observation Facility
Time of the weather observation 1153 Central Daylight Time
Direction of event from weather observation facility (degrees) 45
Weather Observation Facility ID HOU
Elevation of weather observation facility 47
Distance of event from weather observation facility (units?) 10
Time Zone of the weather observation CDT
Lighting Conditions Day
Lowest Ceiling Height 7000
Lowest Non-Ceiling Height 3000
Sky/Lowest/Cloud Conditions Scattered
Sky Condition for Lowest Ceiling Broken
Visibility Runway Visual Range (Feet) 0
Visibility Runway Visual Value (Statute Miles) 0
Visibility (Statute Miles) 10
Air Temperature at event time (in degrees celsius) 31
Dew Point at event time (in degress fahrenheit) 24
Wind Direction (degrees magnetic) 160
Variable Wind Indicator Unknown
Wind Speed (knots) 7
Wind Velocity Indicator Unknown
Wind Gust Indicator Not Gusting
Wind Gust (knots) 0
Altimeter Setting at event time (in. Hg) 30
Density Altitude (feet) 1772
Intensity of Precipitation Light
METAR weather report --
Event Highest Injury Fatal
On Ground, Fatal Injuries 0
On Ground, Minor Injuries 0
On Ground, Serious Injuries 0
Injury Total Fatal 3
Injury Total Minor --
Injury Total None --
Injury Total Serious --
Injury Total All 3
Investigating Agency NTSB
NTSB Docket Number (internal use) 1911
NTSB Notification Source --
NTSB Notification Date Jul 17 1999 12:00AM
NTSB Notification Time 1300
Fiche Number and/or location -used to find docket information IMAGE
Date of most recent change to record May 11 2001 4:05AM
User who most recently changed record dbo
Basic weather conditions Visual Meteorological Cond
FAA District Office --

Aircraft Involved

Aircraft #1

Aircraft Registration Number N110HH
NTSB Number FTW99FA192
Missing Aircraft Indicator N
Federal Aviation Reg. Part Part 91: General Aviation
Type of Flight Plan filed Company VFR
Flight plan Was Activated? --
Damage Destroyed
Aircraft Fire None
Aircraft Explosion None
Aircraft Manufacturer's Full Name MBB
Aircraft Model BK-117-B2
Aircraft Series Identifier BK-117-B2
Aircraft Serial Number 7122
Certified Max Gross Weight 7055
Aircraft Category Helicopter
Aircraft Registration Class U.S. Registered/U.S. Soil
Aircraft is a homebuilt? No
Flight Crew Seats --
Cabin Crew Seats --
Passenger Seats --
Total number of seats on the aircraft 8
Number of Engines 2
Fixed gear or retractable gear Fixed
Aircraft, Type of Last Inspection AAIP
Date of Last Inspection Jul 7 1999 12:00AM
Airframe hours since last inspection 25
Airframe Hours 7815
ELT Installed Yes
ELT Activated No
ELT Aided Location of Event Site Unknown
ELT Type --
Aircraft Owner Name HERMANN MEMORIAL HOSPITAL SYS
Aircraft Owner Street Address 7737 SW FREEWAY STE 200
Aircraft Owner City HOUSTON
Aircraft Owner State TX
Aircraft Owner Country USA
Aircraft Owner Zipcode 77047
Operator is an individual? No
Operator Name --
Operator Same as Owner? Yes
Operator Is Doing Business As --
Operator Address Same as Owner? Yes
Operator Street Address --
Operator City --
Operator State --
Operator Country USA
Operator Zip code --
Operator Code GVNA
Owner has at least one certificate Yes - certificate holder
Other Operator of large aircraft? No
Certified for Part 133 or 137 Operation --
Operator Certificate Number --
Indicates whether an air carrier operation was scheduled or not --
Indicates Domestic or International Flight --
Operator carrying Pax/Cargo/Mail --
Type of Flying (Per_Bus / Primary) Positioning
Second Pilot on Board No
Departure Point Same as Event No
Departure Airport Code 20TA
Departure City HOUSTON
Departure State TX
Departure Country
Departure Time 1226
Departure Time Zone CDT
Destination Same as Local Flt --
Destination Airport Code TE11
Destination City FRESNO
Destination State TX
Destination Country
Specific Phase of Flight --
Report sent to ICAO? --
Evacuation occurred --
Date of most recent change to record Feb 2 2009 2:55PM
User who most recently changed record johb
Since inspection or accident --
Event Location Runway Number and Location 0
Runway Length --
Runway Width --
Sight Seeing flight No
Air Medical Flight Yes
Medical Flight --