Date:	Monday 18 March 2019
Time:	15:37
Type:	IAI 1124 Westwind
Owner/operator:	Sundance Airport FBO LLC
Registration:	N4MH
MSN:	232
Year of manufacture:	1978
Total airframe hrs:	11030 hours
Engine model:	Garrett TFE731-3D-1G
Fatalities:	Fatalities: 2 / Occupants: 2
Aircraft damage:	Destroyed, written off
Category:	Accident
Location:	Oklahoma City-Sundance Airport, OK (HSD) -   United States of America
Phase:	Landing
Nature:	Private
Departure airport:	Panama City-Northwest Florida Beaches International Airport, FL (ECP/KECP)
Destination airport:	Oklahoma City-Sundance Airpark, OK (HSD/KHSD)
Investigating agency:	NTSB
Confidence Rating:	Accident investigation report completed and information captured

Narrative:
An IAI 1124 Westwind aircraft was destroyed when it was involved in an accident near Oklahoma City-Sundance Airpark, Oklahoma. Both pilots sustained fatal injuries.
The two commercial pilots were conducting a personal, cross-country flight. As the airplane approached the approach end of the landing runway, it began to climb, rolled left, became inverted, and then impacted terrain.
The left thrust reverser (T/R) was found open and unlatched at the accident site. An asymmetric deployment of the left T/R would have resulted in a left roll/yaw. The lack of an airworthy and operable cockpit voice recorder, which was required for the flight, precluded identifying which pilot was performing pilot flying duties, as well as other crew actions and background noises, that would have facilitated the investigation.
Postaccident examination of the airplane revealed that it was not equipped, nor was required to be equipped, with a nose landing gear ground contact switch intended to preclude inflight operation of the thrust reverser.
Further, electrical testing of the T/R left and right stow microswitches within the cockpit throttle quadrant revealed that the left stow microswitch did not operate within design specifications. Disassembly of the left and right stow microswitches revealed evidence of arc wear due to aging. Based on this information, it is likely that the airplane’s lack of an NLG ground contact switch and the age-related failure of the stow microswitches resulted in an asymmetric T/R deployment while on approach and a subsequent loss of airplane control. Also, there were additional T/R system components that were found to unairworthy that would have affected the control of the T/R system.

Cause:
The airplane’s unairworthy thrust reverser (T/R) system due to inadequate maintenance that resulted in an asymmetric T/R deployment during an approach to the airport and the subsequent loss of airplane control.

20:05 UTC / 15:05 local time:
KHSD 182005Z AUTO 00000KT 10SM CLR 19/M02 A3026 RMK A01

20:25 UTC / 15:25 local time:
KHSD 182025Z AUTO 18007KT 10SM CLR 20/M02 A3025 RMK A01

20:45 UTC / 15:45 local time:
KHSD 182045Z AUTO VRB03KT 10SM CLR 20/M02 A3025 RMK A01

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photo (c) NTSB; Oklahoma City-Sundance Airport, OK (HSD); 18 March 2019; (publicdomain)

photo (c) NTSB; Oklahoma City-Sundance Airport, OK (HSD); 18 March 2019; (publicdomain)

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