ASN Wikibase Occurrence # 17754
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| Date: | Saturday 10 May 2008 |
| Time: | 22:45 |
| Type: |  Eurocopter EC 135T2 |
| Owner/operator: | Air Methods Corp |
| Registration: | N135UW |
| MSN: | 0535 |
| Year of manufacture: | 2006 |
| Total airframe hrs: | 457 hours |
| Engine model: | Turbomeca ARRIUS 2B2 |
| Fatalities: | Fatalities: 3 / Occupants: 3 |
| Aircraft damage: | Destroyed |
| Category: | Accident |
| Location: | Onalaska, WI -
 United States of America
|
| Phase: | En route |
| Nature: | Ferry/positioning |
| Departure airport: | La Crosse, WI (LSE) |
| Madison, WI (WS27) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
After transporting a patient to a local hospital and refueling at La Crosse Municipal Airport (LSE), the emergency medical services (EMS) helicopter departed LSE (elevation 656 feet mean sea level [msl]) about 2234 central daylight time (all times in this brief are central daylight time) on a return flight to its base heliport. Dark night visual meteorological conditions (VMC) prevailed at LSE. A ramp services employee at LSE who had observed the helicopter lift off and proceed east-southeast observed “moderate” rain and “fair” visibility at the time of takeoff. Witnesses located southeast of the airport reported hearing the helicopter in flight about the time of the accident, and one witness reported hearing a loud crashing sound. A search was initiated shortly after the crash but was hampered by the terrain and fog that had formed overnight. A search located the helicopter the following morning; the helicopter had impacted trees along a sparsely populated ridgeline about 5 miles southeast of LSE. The elevation of the ridgeline was approximately 1,164 feet msl, with 50- to 60-foot-tall trees in the area initially struck by the helicopter.
Distribution of the wreckage was consistent with the helicopter impacting the trees in a nearly level flight attitude under controlled flight. Examination of the helicopter’s engines revealed inlet debris, rotational scoring, and centrifugal turbine blade overload failures consistent with the engines being operated at a moderate to high power level (on both engines) at the time of impact. Nonvolatile memory downloaded from the digital engine control units (DECUs) indicated that both engines were in “flight mode” at the time of impact. Although the left engine main selector switch was observed in the “idle” position after the accident, the lack of anomalies related to the switch and the corresponding DECU in flight mode are consistent with the switch having been moved as a result of impact. No preimpact mechanical malfunctions of the helicopter were found.
The reported weather conditions at LSE about 2253 included VMC: calm winds, 8 miles visibility in light rain, few clouds at 1,400 feet above ground level (agl) [2,056 feet msl], overcast clouds at 5,000 feet agl (5,656 feet msl), temperature 10 degrees C, dew point 8 degrees C, and altimeter 29.70 inches of mercury. The preflight weather briefing obtained by the pilot about 1 hour before departure indicated VMC along the route of flight at the time of the briefing but forecasted deteriorating conditions later in the evening after about 2200, including possible instrument meteorological conditions (IMC). Search and rescue personnel reported fog and mist along the ridgeline overnight during the search operations. Additionally, an EMS pilot for another operator reported that when he departed LSE about 2 hours before the accident flight, fog was beginning to form on the west side of the Mississippi River and in the bluffs east of his flight route. He subsequently returned to LSE and declined at least one additional flight that evening due to deteriorating weather conditions. Because of the variability in weather conditions on the night of the accident, the investigation could not determine if the pilot encountered IMC at the time of the accident.
The pilot was transferred to the accident operator as a result of the accident operator’s acquisition of his previous employer about 3 months before the accident. The accident pilot was initially qualified as visual flight rules (VFR)-only. An instrument proficiency check was not completed in conjunction with initial training. As a result, the accident pilot was limited to VFR-only operations at the time of the accident. (The accident pilot was current for instrument flight rules [IFR] at his previous place of employment.)
During preflight planning, the pilot should have identified any obstacles along the route of flight, including the tree-covered ridgeline. Company records indicated that the pilot had completed one prior flight to LSE within the previous 16-month period, which
Probable Cause: The pilot’s failure to maintain clearance from trees along the top of a ridgeline due to inadequate preflight planning, insufficient altitude, and the lack of a helicopter terrain awareness and warning system.
Member Sumwalt did not approve this brief and probable cause. Member Sumwalt filed a dissenting statement that can be found in the public docket for this accident.
Accident investigation:
 |
|
Sources:
NTSB
Location
Images:
(c) NTSB
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 11-May-2008 10:04 | plane freak | Added |
| 11-May-2008 10:07 | harro | Updated |
| 12-May-2008 11:05 | Fusko | Updated |
| 12-May-2008 21:05 | HM SR | Updated |
| 12-May-2008 21:08 | signaal | Updated |
| 12-May-2008 23:39 | harro | Updated |
| 18-May-2008 09:56 | Updated | |
| 21-May-2008 22:57 | HM | Updated |
| 15-Jan-2009 12:08 | harro | Updated |
| 18-Aug-2010 15:34 | TB | Updated [Aircraft type, Cn, Other fatalities, Source] |
| 05-Mar-2013 11:14 | TB | Updated [Aircraft type, Location, Destination airport, Source] |
| 07-May-2016 09:46 | Aerossurance | Updated [Source, Narrative] |
| 07-May-2016 10:48 | Aerossurance | Updated [Aircraft type] |
| 21-Dec-2016 19:14 | ASN Update Bot | Updated [Time, Damage, Category, Investigating agency] |
| 21-Dec-2016 19:16 | ASN Update Bot | Updated [Time, Damage, Category, Investigating agency] |
| 21-Dec-2016 19:20 | ASN Update Bot | Updated [Time, Damage, Category, Investigating agency] |
| 03-Dec-2017 10:50 | ASN Update Bot | Updated [Aircraft type, Operator, Other fatalities, Nature, Departure airport, Destination airport, Source, Narrative] |
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