- Date
- August 30, 2002, 10:06 local (17:06 UTC)
- Place
- Lytle Creek, CA
- Injuries
- 1 uninjured
- Damage
- Substantial damage
- Phase of flight
- Enroute
- Aircraft
- N747ASikorsky S-55T
- Weather
- Visual (VMC) · Day
- Status
- Completed · report February 5, 2004
- Report
- Approved by Office Director
- Parties
- Federal Aviation Administration
- FAA report
- 20020830022079A
- Case key
- 55603
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
Failure of the hydraulic system due to contamination in the hydraulic fluid, which resulted in an in-flight loss of control.
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
The helicopter collided with terrain while attempting a precautionary landing due to a hydraulics system failure. The helicopter was engaged in firefighting water drops. While returning to pickup additional fuel, and make bucket repairs, the red hydraulic failure light illuminated and the flight controls became stiff. About 10 feet above the ground, the cyclic flight control moved "hard over," which resulted in the nose moving up and to the right until the main rotor blades contacted the ground. The helicopter came to rest on its right side. Post crash examination by a laboratory revealed contamination of the hydraulic fluid by water and microbial growth.
Factual narrative
On August 30, 2002, at 1006 Pacific daylight time, a Sikorsky S-55T, N747A, collided with terrain while attempting a precautionary landing in a dry creek bed in Lytle Creek, California. The helicopter sustained substantial damage and the commercial pilot, the sole occupant, was not injured. The U.S. Forest Service was operating the helicopter as a fire suppression unit under the provisions of 14 CFR Part 133. The flight originated from a temporary helipad about 0830. Visual meteorological conditions prevailed and no flight plan had been filed.
The Forest Service reported that the helicopter had been engaged in water bucket support on a fire for about 2 hours. During the last water drop the bucket failed to release the water. Repeated attempts to release the water failed so the pilot decided to return to base and refuel and repair the bucket.
The pilot stated that a red hydraulic warning light illuminated and the flight controls became stiff. He began a precautionary approach to an open area. About 10 feet above the ground, the cyclic flight control moved "hard over," which resulted in the nose moving up and to the right. The pilot was unable to regain control before the main rotor blades made contact with a rocky shelf. The helicopter came to rest on its right side.
Post crash examination of the wreckage by the Forest Service investigation team did not reveal evidence of ruptured hydraulic lines. They took a sample of hydraulic fluid from the reservoir and stated that it appeared to be severely contaminated. Post crash examination by a laboratory revealed contamination of the hydraulic fluid by water and microbial growth.
Aircraft
- Registration
- N747A
- Reported as
- Sikorsky S-55T
- Category
- Helicopter
- Serial number
- 55-910
- Airframe hours
- 12,689
- Engine
- Garrett-AiResearch TSE 331-3LL, 800 horsepower, turbo shaft
- Damage
- Substantial damage
- Flight
- Public aircraft · Part 133
- Registered owner
- Central Sierra Helicopters
- Airworthiness certificate
- Standard, Normal
- Last inspection
- Annual · October 20, 2001 · 74.7 hours before
- Departed
- Lytle Creek, CA
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
- 32
- Injuries
- None
- Certificates
- Commercial, Flight instructor
- Airplane ratings
- Multi-engine land, Single-engine land
- Instrument ratings
- Airplane
- Medical
- Class 2, Valid Medical--w/ waivers/lim
- Last flight review
- July 11, 2002
- Seat
- Right
- Flight hours
- 1,815 total · 85 in this make and model · 1,719 as pilot in command
Weather
- Conditions
- Visual (VMC) · Day
- Wind
- 190° at 3 knots
- Visibility
- 7 statute miles
- Lowest ceiling
- None
- Temperature
- 84 °F, dew point 48 °F
- Altimeter
- 29.90 inHg
- Observed at
- KONT, 15 nm away
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 N747A · 1
Matched to the same aircraft by N-number and date.