- Date
- July 6, 1985, 11:09 local (17:09 UTC)
- Place
- Keystone, SD
- Injuries
- 4 fatal, 1 serious
- Damage
- Destroyed
- Phase of flight
- Approach
- Aircraft
- N5410WHughes 369HS
- Weather
- Visual (VMC) · Day
- Status
- Completed
- Report
- Approved by Office Director
- FAA report
- 19850706033369A
- Case key
- 16544
From the NTSB’s public API. By law, NTSB reports can’t be used as evidence in lawsuits over the accident.
On this page
Sequence of events
NTSB’s coding before 2008: each occurrence and phase of flight, and the causes and factors under it. The codes are defined in NTSB’s coding manual.
Analysis
Main rotor hub was overhauled by a repair station that was not authroized by Hughes helicopters for hub overhauls. The main rotor hub and blades separated in-flt 279 hrs after overhaul. The acft crashed in a densily wooded area. Post accident exam of the main rotor system revealed the torsion-tension strap pack failed due to fatigue cracking in the stainless steel laminants. Metallurgical exam revealed evidence of corrosion pitting in the laminants. The corrosion pits were the origin of fatigue cracks. The maximum allowable number of laminant failures in any one strap is 3. The failed strap pack contained 9 fatigue failed laminants.
Aircraft
- Registration
- N5410W
- Reported as
- Hughes 369HS
- Category
- Helicopter
- Serial number
- 900255S
- Airframe hours
- 7,007
- Engine
- Allison 250-C18B, 278 horsepower, turbo shaft
- Damage
- Destroyed
- Flight
- Part 91
- Operator
- Rushmore Helicopters, Inc.
- Airworthiness certificate
- Standard, Normal
- Last inspection
- Annual · September 5, 1984 · 100 hours before
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
- 24
- Certificate
- Commercial
- Airplane ratings
- Single-engine land
- Medical
- Class 2, Valid Medical--w/ waivers/lim
- Seat
- Left
- Flight hours
- 1,479 total · 500 in this make and model · 1,389 as pilot in command · 87 in the last 90 days · 3 in the last 24 hours
Weather
- Conditions
- Visual (VMC) · Day
- Wind
- Variable at 5 knots
- Visibility
- 20 statute miles
- Lowest ceiling
- None
- Temperature
- 84 °F
FAA reports on this event · 1
The FAA’s own accident and incident reports, matched to the aircraft by N-number and date.