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SB20, Unalaska AK USA, 2019
From SKYbrary Wiki
|On 17 October 2019, a Saab 2000 overran the landing runway at Unalaska and after exiting the airport perimeter finally came to rest on shoreline rocks. One passenger was killed, one was seriously injured and three others sustained minor injuries. The Investigation has so far established that the overrun occurred after completion of a second approach following a go around from the first after it became unstabilised and that touchdown was made with a tailwind component in excess of 10 knots.|
|Actual or Potential
|Human Factors, Runway Excursion|
|Operator||Peninsula Aviation Services Inc.|
|Type of Flight||Public Transport (Passenger)|
|Intended Destination||Unalaska Airport|
|Take off Commenced||Yes|
|Location - Airport|
|Tag(s)||Procedural non compliance|
|Tag(s)||Overrun on Landing,|
Significant Tailwind Component
|Damage or injury||Yes|
|Fatalities||Few occupants (1)|
On 17 October 2019, a Saab 2000 (N686PA) being operated on a domestic passenger flight from Anchorage to Unalaska as PenAir flight 3296 overran the destination runway after touching down on destination runway 13 following its second approach there in day VMC. One passenger amongst the 42 occupants was killed, one passenger was seriously injured and three other passengers sustained minor injuries. The aircraft was substantially damaged.
The flight was cleared to make an RNAV approach to runway 13 - see the illustration below. The only other published instrument approach procedure was an NDB approach to the same runway. Prior weather reports from the local weather observer had been passed giving the wind as initially from 210° at 8-14 knots and then 180° at 7 knots with visibility in the range 7 to 10 miles and the ceiling initially at 4,300 feet and later at 3,900 feet. The aircraft was fully configured for a flap 20 approach with the gear down and the spot wind passed as from 270° at 10 knots but the approach then became unstable and was discontinued. During this go around, the surface wind was initially passed as from 300° at 8 knots but later on after it had been completed as from 290° at 16-30 knots. Communications between the weather observer and another aircraft, which would have been heard by the Saab 2000 crew, were then recorded which had “indicated that winds favoured runway 31 but could shift back to runway 13”.
The aircraft was then positioned visually onto a second runway 13 approach configured as for the first approach. During this second approach, the surface wind was passed as from 300 degrees at 24 knots but the approach was still continued to a landing. Touchdown occurred at approximately 129 KIAS with a 13 knot tailwind component and the landing roll, with a recorded peak deceleration of -0.48g, lasted around 25 seconds and was assisted by use of propeller reverse pitch until the aircraft departed the runway. It then crossed the overrun area and some grass, passed through a metre-high chain-link perimeter fence leaving signs of left engine propeller contact and successively crossed a ditch, hit a large rock and crossed a public road before coming to a stop on the shoreline. In the vicinity of the road, the aircraft left wing or left engine propeller struck a 4 to 5 feet high post and the left propeller struck a 2.5 metre high yellow diamond shaped road sign. There were also strike marks consistent with the right engine propeller tips contacting the ground near where the aircraft stopped.
The crew ordered an emergency evacuation using exits on the right hand side of the aircraft and made a radio call for assistance. The Captain subsequently stated that after initially selecting reverse and applying normal brake pressure, he had increased this to maximum braking at around 80 knots.
Damage to the aircraft fuselage included a hole and impact damage to the left forward fuselage just forward of the propeller plane in the vicinity of seat 4A with one propeller blade loosely stuck in the surrounding structure outside the fuselage and virtually the complete length of another - 1.5 metres long - inside the passenger cabin. Internal damage to the passenger cabin was limited to the left side between rows 3 and 6 where the overhead stowage had become partially detached with associated debris hanging down into the seats or lying on the floor.
The four main landing gear assemblies were examined and it was noted that the left outboard tyre was holed and completely deflated due to apparently impeded rotation. The left inboard tyre was found to be significantly below the recommended inflation pressure but both right main gear tyres were likely to have been within the recommended inflation pressure range. The brake wear pins on both assemblies appeared to have been within the serviceable range. There was considerable impact-related damage to the left engine and propeller but the right engine was intact as was its propeller minus all six propeller tips.