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ASN Wikibase Occurrence # 162506
Last updated: 10 November 2020
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Date:25-NOV-2013
Time:18:04
Type:Silhouette image of generic PA23 model; specific model in this crash may look slightly different
Piper PA-23-160 Apache
Owner/operator:Private
Registration: N4016P
C/n / msn: 23-1491
Fatalities:Fatalities: 1 / Occupants: 1
Aircraft damage: Substantial
Category:Accident
Location:Twin Lakes Airport - KS17, Graniteville, SC -   United States of America
Phase: Take off
Nature:Private
Departure airport:Graniteville, SC (S17)
Destination airport:Graniteville, SC (S17)
Investigating agency: NTSB
Narrative:
During the initial climb after a night takeoff, the left engine lost power. A witness reported that the pilot attempted to return to the runway he had taken off from, but he lost control. The airplane descended, struck trees, and came to rest next to a taxiway that paralleled the departure runway.

Examination of the wreckage revealed that the airplane had not been configured for single engine flight; the left engine's propeller was not feathered, and the landing gear was down. Because the hydraulic pump was installed on the left engine, it would not have been operating after the engine lost power. Therefore, the pilot would have had to manually retract the landing gear by pumping the emergency pump handle 30 to 40 times. However, given the pilot's decision to return to the airport, he may have elected not to retract the landing gear. With the left engine's propeller not feathered and the landing gear down, the airplane would have rapidly decelerated unless the pilot lowered the airplane's nose to maintain airspeed. Additionally, in order to maintain control during the right turn, the pilot needed to counteract the tendency for the airplane's bank angle to increase due to the asymmetrical power from the right engine. The airplane's airspeed likely decreased below the single engine minimum controllable airspeed (Vmc), which resulted in the loss of control.

Before the accident, the pilot conveyed concerns about the airplane's left fuel valve control to two separate airframe and powerplant mechanics. During the conversations, he detailed his plans to troubleshoot and attempt to repair the problem himself. The mechanics urged the pilot not to perform the maintenance himself and to have the problem diagnosed by a knowledgeable certificated mechanic. The pilot was not a certificated mechanic and was not authorized to perform maintenance on the accident airplane.

Postaccident examination of the airplane's fuel system revealed that, although the left and right fuel valve controls were selected to the main tank positions, the left and right main fuel tank shutoff valves were closed, and the left and right auxiliary fuel tank shutoff valves were open. Therefore, the left and right engines were being supplied with fuel from their respective auxiliary tanks instead of from the main tanks. The fuel tanks were damaged; however, fuel was observed in the corners of the left and right main tanks and in the right auxiliary tank, but the left auxiliary fuel tank was devoid of fuel. Therefore, the left engine loss of power was due to fuel starvation.

Examination of the fuel valve control cable assemblies revealed that neither the left or right cable assembly was connected to its respective auxiliary fuel valve arm assembly, which controlled both the main and auxiliary fuel shutoff valves. Because the securing hardware was still in place and was undamaged, it is likely that the control cable assemblies had, at some point, been disconnected from the arm assemblies and not reconnected. This resulted in the engines receiving fuel from the auxiliary tanks when the fuel valve controls were selected to the main tank positions. Given the pilot's discussions with the mechanics, it is likely that he disconnected the control cable assemblies from the arm assemblies when he attempted to troubleshoot the problem.


Probable Cause: The pilot's improper maintenance of the airplane's fuel system, which resulted a loss of power in the left engine due to fuel starvation. Also causal was the pilot's failure to maintain minimum controllable airspeed following the loss of engine power, which resulted in a loss of airplane control.

Sources:

NTSB: https://www.ntsb.gov/_layouts/ntsb.aviation/brief.aspx?ev_id=20131125X94952&key=1
FAA register: http://registry.faa.gov/aircraftinquiry/NNum_Results.aspx?NNumbertxt=4016P


Revision history:

Date/timeContributorUpdates
26-Nov-2013 01:34 Geno Added
26-Nov-2013 06:41 Geno Updated [Aircraft type, Total fatalities, Total occupants, Other fatalities, Source, Narrative]
26-Nov-2013 17:26 Geno Updated [Aircraft type, Registration, Cn, Operator, Source, Embed code, Damage, Narrative]
26-Nov-2013 17:53 Alpine Flight Updated [Time, Location, Damage, Narrative]
06-Dec-2013 22:54 Geno Updated [Time, Phase, Nature, Departure airport, Source, Narrative]
21-Dec-2016 19:28 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]
29-Nov-2017 09:23 ASN Update Bot Updated [Operator, Other fatalities, Departure airport, Destination airport, Source, Narrative]

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