ASN Wikibase Occurrence # 153625
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| Date: | Thursday 27 March 2003 |
| Time: | 16:36 |
| Type: |  Bell 407 |
| Owner/operator: | U.S. Forest Service |
| Registration: | N175PA |
| MSN: | 53154 |
| Year of manufacture: | 1997 |
| Total airframe hrs: | 3339 hours |
| Fatalities: | Fatalities: 2 / Occupants: 5 |
| Aircraft damage: | Destroyed |
| Category: | Accident |
| Location: | Broadus, TX -
 United States of America
|
| Phase: | Manoeuvring (airshow, firefighting, ag.ops.) |
| Nature: | Survey |
| Departure airport: | Lufkin Angelina County Airport, TX (LFK/KLFK) |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
On March 27, 2003, at 1636 central standard time, a Bell 407 helicopter, N175PA, registered to I Inc., of Kirkland, Washington, and operated as a Public Use aircraft under contract to the US Forest Service (USFS), was destroyed when it crashed into heavily wooded terrain near Broadus, Texas, while conducting low level flight operations in support of the Federal Emergency Management Agency's (FEMA) mission to support an inter-agency (NASA, Texas Forest Service, USFS) search/recovery effort of Columbia Space Shuttle debris. The pilot and 1 crewmember were fatally injured and 3 other crewmembers sustained serious injuries. Visual meteorological conditions prevailed and a VFR flight following plan was filed for the Title 14 Code of Federal Regulations Part 91 Public Use flight. The flight originated at 1515 from the search operation's Helibase, located at the Angelina County Airport, 7 miles south of Lufkin, Texas.
While establishing a 125-foot out of ground effect hover during a search and recovery mission of Columbia Space Shuttle debris, the helicopter lost power without warning, descended rapidly into a forest with 80-foot tall trees, and impacted the ground. There were no reported radio communications or distress calls. During post accident component examinations, while performing the rigging procedure for the Hydro-Mechanical Unit (HMU) during an engine test cell run, anomalies were noted with the actual position of the throttle Position Lever Angle (PLA) and the readings obtained from the Electronic Control Unit (ECU). During the test cell run, the Full Authority Digital Electronic Control System (FADEC) controlled engine operated erratically in the Auto mode when rigged with its original Electronic Control Unit (ECU) and (HMU). The engine control was then changed from Auto to Manual mode, and the engine responded to throttle input as required; however, the ECU readings were erratic. After a slave ECU was installed, the engine operated with similar erratic readings. A slave HMU was installed, and the engine operated normally without erratic readings. The ECU's nonvolatile memory was downloaded, and revealed no faults on the accident flight. Extensive electrical and mechanical testing of the HMU revealed severe signal fallout on the PLA signal, which was found to be random in location, bi-directional, and present during both rotational and stationary operation of the PLA input of the HMU. The source of the fallout was traced to the HMU potentiometer. The PLA potentiometer examinations consisted of mechanical measurements, electrical testing, inspection of the conductive epoxy joints, and microscopic examination of the three lead wire connections to the potentiometer elements. The PLA potentiometer was found faulty due to insulation breakdown between the rotor and shaft, resulting in a single-point failure that induced erratic fuel metering to the engine. As a result of the findings from this investigation, the Safety Board issued four safety recommendations (A-03-18 through A-03-21), on May 27, 2003, to the FAA that addressed the PLA potentiometer deficiencies.
Probable Cause: The partial loss of engine power due to erratic fuel flow metering to the engine resulting from the single point failure of the PLA potentiometer in the hydro-mechanical fuel control unit. A contributing factor was the lack of suitable terrain to execute a forced landing.
Accident investigation:
 |
|
Sources:
NTSB: https://www.ntsb.gov/_layouts/ntsb.aviation/brief.aspx?ev_id=20030502X00613&key=1
History of this aircraft
Other occurrences involving this aircraft
| 16 April 2000 | N175PA | Papillon Airways Inc. | 0 | GRAND CANYON, Arizona | |
sub |
Location
Images:
Photos: NTSB
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 01-Mar-2013 10:48 | TB | Added |
| 21-Dec-2016 19:28 | ASN Update Bot | Updated [Time, Damage, Category, Investigating agency] |
| 08-Dec-2017 18:28 | ASN Update Bot | Updated [Operator, Nature, Departure airport, Source, Narrative] |
| 29-Apr-2020 07:43 | Anon. | Updated [Nature] |
| 29-Apr-2020 07:44 | harro | Updated [Operator] |
| 01-May-2022 08:35 | Ron Averes | Updated [Operator] |
| 12-Nov-2022 01:58 | Ron Averes | Updated [Operator, Departure airport] |
Corrections or additions? ... Edit this accident description
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