Accident Swearingen SA227-TT Merlin IIIC N6UP,
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ASN Wikibase Occurrence # 221704
 
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Date:Friday 19 January 2018
Time:16:30
Type:Silhouette image of generic SW3 model; specific model in this crash may look slightly different    
Swearingen SA227-TT Merlin IIIC
Owner/operator:Airco JN LLC
Registration: N6UP
MSN: TT-441
Year of manufacture:1981
Total airframe hrs:9258 hours
Engine model:Garrett TPE 331
Fatalities:Fatalities: 0 / Occupants: 4
Aircraft damage: Substantial
Category:Accident
Location:Houston, TX -   United States of America
Phase: En route
Nature:Executive
Departure airport:Beaumont, TX (BPT)
Destination airport:Uvalde, TX (UVA)
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
Narrative:
During a corporate flight, as the pilots climbed the airplane to flight level 180, both electrical generators failed and would not reset. The pilots attempted to troubleshoot the problem but could not regain electrical power. The airplane’s battery power was rapidly deteriorating, so the pilots declared an emergency and diverted to the nearest airport. Due to the loss of electrical power, the pilots lost communications and had to manually extend the landing gear. They could not verify, with air traffic control tower personnel, if the landing and nose gear were extended and locked. The pilots made a forced landing with the nose landing gear not fully extended, causing the airplane to skid on the forward fuselage after touchdown and substantially damaging the engines.
Postaccident examination of the airplane revealed the right generator current limiter had failed. A mechanic connected a battery to the airplane, and the left propeller immediately began to rotate. The mechanic determined that there was uncommanded voltage to the left starter, which was caused by a failure of the left starter relay when the engine was started before the flight. During the flight, the right generator was managing all of the airplane’s electrical load, the cumulative electrical load exceeded the capacity of the right generator current limiter, and the generator failed. At that point, the airplane’s electrical load was only being supplied by battery power, which was quickly depleted. Postaccident examination of the nose landing gear did not identify a mechanical reason to explain why the nose landing gear did not extend during the pilots’ emergency landing gear extension procedure.



Probable Cause: The failure of the left starter relay during engine start, which resulted in a loss of electrical and battery power during the flight and led to a forced landing with the nose landing gear not fully extended, causing substantial damage to the engines.

Accident investigation:
cover
  
Investigating agency: NTSB
Report number: CEN18LA086
Status: Investigation completed
Duration: 1 year
Download report: Final report

Sources:

NTSB

History of this aircraft

Other occurrences involving this aircraft
29 March 1988 N30042 FMI Financial Corp. 0 Miami International Airport, FL (MIA/KMIA) sub
Collision with other aircraft on apron

Location

Revision history:

Date/timeContributorUpdates
10-Feb-2019 10:48 ASN Update Bot Added

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