Accident Cessna 208B Grand Caravan EX N2069B,

ASN Wikibase Occurrence # 318724

Date:	Friday 18 November 2022
Time:	10:19
Type:	Cessna 208B Grand Caravan EX
Owner/operator:	Copper Mountain Aviation LLC
Registration:	N2069B
MSN:	208B5657
Year of manufacture:	2021
Engine model:	Pratt & Whitney Canada PT6A-140
Fatalities:	Fatalities: 4 / Occupants: 4
Aircraft damage:	Destroyed, written off
Category:	Accident
Location:	near Snohomish, WA - United States of America
Phase:	Manoeuvring (airshow, firefighting, ag.ops.)
Nature:	Test
Departure airport:	Renton Airport, WA (RNT/KRNT)
Destination airport:	Renton Airport, WA (RNT/KRNT)
Investigating agency:	NTSB
Confidence Rating:	Information verified through data from accident investigation authorities

Narrative:
The Cessna 208B Grand Caravan EX, N2069B, was destroyed when it impacted terrain in Snohomish, Washington. All four onboard were killed.

The aircraft was operated by Raisbeck Engineering in a flight testing program to obtain a Supplemental Type Certificate (STC) for an aerodynamic drag reduction system (DRS) on the Cessna 208B EX. The company already held such an STC for the Cessna 208B model.
The airplane began flights to support the flight-test three days before the accident. The program started out with flight-test data-collection flights to establish baseline data.
The purpose of the accident flight was to complete a test that was cut short the day prior, which was baseline testing of the airplane's aft CG stall characteristics.
Preliminary radar track data indicated that after departing Renton, Washington around 09:25, the airplane continued to the north in a gradual climb to about 9,500 ft mean sea level (msl) and began a series of turns/maneuvers. The airplane proceeded for about 45 minutes varying in altitude between about 6,500 ft to 10,275 ft msl. At 10:17 the track data indicated the airplane was climbing to an altitude of 9,700 ft msl and turning to the left, making a near 360° turn and then at 10:19:06, there was a sharp 180° left-turn. The track continued west until the last recorded hit at 10:19:18. During the last 12 seconds the track indicated that the airplanes descent rate exceeded 14,000 ft-per-minute (fpm) and gradually lessened to 8,700 fpm.
At the time the flight crew were likely at the second to last maneuver on the test card which specified: 96 kts indicated airspeed; flaps in landing configuration; 930 ft-lbs of torque; propeller rpm fully forward; and accelerated 30° bank to the left.

Witnesses reported that they observed the airplane break-up inflight and watched pieces floating down. The airplane then descended in a nose-low near-vertical corkscrew maneuver toward the ground.

Accident investigation: