ASN Wikibase Occurrence # 205770
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| Date: | Tuesday 21 February 2017 |
| Time: | 10:15 |
| Type: |  Eurocopter AS 350B3 |
| Owner/operator: | Private |
| Registration: | N413LP |
| MSN: | 3228 |
| Year of manufacture: | 1999 |
| Total airframe hrs: | 1846 hours |
| Engine model: | Turbomeca Arriel 2B |
| Fatalities: | Fatalities: 0 / Occupants: 2 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | San Juan -
 Puerto Rico
|
| Phase: | En route |
| Nature: | Training |
| Departure airport: | San Juan, PR (TJIG) |
| San Juan, PR (TJIG) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
The pilot/owner of the turbine helicopter was practicing autorotations with a flight instructor. After completing several autorotations uneventfully, the instructor asked if he could perform one, and the pilot agreed. Near the flare at the end of the maneuver, the pilot heard the engine overrev, followed by an Nr (rotor speed) aural warning, followed by a fire warning light illumination on the instrument panel. After landing, the pilot exited the helicopter with a fire extinguisher and attempted to extinguish an engine fire.
Review of data downloaded from a vehicle-engine multifunction display and digital engine control unit revealed that the first failure recorded during the flight indicated that the gas generator rotation speed (N1) reached an out-of-limit value. At that time, the fuel regulation was in mixed mode, as the collective twist grip throttle control was out of the “flight” detent and the pilot was manually controlling the throttle. A second failure was recorded 2 seconds later, which indicated that the free turbine rotation speed (N2) reached an out-of-limit value. The failure was triggered by the maximum recorded value of 545 rpm, which equated to a turbine speed (Nr) of 140%.
The engine’s freewheeling turbine was designed to separate turbine blades at 150% Nr in order to prevent the turbine disc separating at 170% Nr. It is likely that the flight instructor excessively opened the fuel metering unit via the twist grip throttle manual control, which resulted in an engine overspeed, turbine blade separation, and subsequent engine fire.
Probable Cause: The flight instructor's incorrect manipulations of the twist grip throttle control during a practice autorotation, which resulted in an engine overspeed and subsequent fire.
Accident investigation:
 |
|
Sources:
NTSB
History of this aircraft
Other occurrences involving this aircraft
| 30 July 2011 | N413LP | Helicorp Inc | 0 | Humacao, Puerto Rico |  |
sub |
| Tailstrike | ||||||
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 07-Feb-2018 13:48 | ASN Update Bot | Added |
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