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Pen Air Saab Overrun Unilaska with Injuries

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Pen Air Saab Overrun Unilaska with Injuries

Old 19th Oct 2019, 16:45
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According to the NTSB they had already done a missed approach prior to the overrun landing attempt.

NTSB: Unalaska crash occurred on plane's 2nd landing attempt
Friday, October 18th 2019, 11:55 PM AKDT
By: Dave Leval
The National Transportation Safety Board says Thursday night's deadly crash of PenAir Flight 3296 in Unalaska took place during the second landing attempt.
NTSB Region Chief Clint Johnson said preliminary witness interviews report the plane attempted to land once, then circled back around. The second time, the plane landed then ran off the runway, crossed a road and almost ended up in the water.
There were 42 people on the flight — 39 passengers and three crew. Alaska State Troopers on Friday named 38-year-old David Oltman from Washington state as the passenger who was killed. He died from injuries sustained in the crash.
"Our entire team is devastated by this tragic accident," said PenAir President/COO Brian Whilden as he fought back tears in a video statement. "On behalf of PenAir, Ravn Air Group, and all of our employees with the company, I would like to extend our deepest sympathy and condolences to the family and loved ones of our passenger who passed away."
Eleven people, including Oltman, were transported for medical care. One person was medevaced to Anchorage, while others are receiving medical care in Unalaska, according to a release on the City of Unalaska website Friday.
The NTSB will now work to find out what caused the crash. Johnson said investigators have plenty of clues.
"The flight data recorder, the cockpit voice recorder, lots and lots of data in addition to the physical evidence," he said. "The airplane itself as far as crush zones, damage to the airplane, all that is going to be studied."
It could take at least a year to find out what caused the crash.
Fuel that had been leaking into the water from the Saab 2000 aircraft has been contained and removed, city officials stated. Remaining fuel in the plane has been removed.
Alaska Department of Transportation & Public Facilities officials have determined the runway was not damaged during the crash, according to a release from the City of Unalaska. A later statement from the city said plans were underway to remove the wreckage on Saturday. The runway and surrounding roadways are expected to reopen once cleared.
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Old 19th Oct 2019, 22:05
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Originally Posted by Australopithecus View Post


Nope. They cannot make an engine containment ring strong enough for turbine blades, so imagine the energy in a much heavier object released from the hub. A friend was once torpedoed by a runaway towbar as they we’re taxiing onto the gate in a Convair 580. The engine was already running down when the towbar hit the prop (at 700 rpm). The blade released and ended up 200m away planted vertically in the ramp.
Actually, turbine blades are required to be contained (as are compressor blades - including the fan) as a cert requirement. They can come out the back (or front) as low energy debris, but not out the side. Turbine (and compressor/fan) discs are another story - the energy is so high that containment is simply not practical (we're talking inches of armor plate).
I'm not sure how practical it would be to shield passengers from propeller intrusion - the energy of a released prop is going to be very high, so it would take a considerable amount of Kevlar/carbon fiber/whatever to prevent intrusion, and due to the aerodynamic properties of a prop blade, the trajectory is rather unpredictable so the potential impact area of the fuselage would be rather large.
I did some work on another proposed installation of the engine used on the Saab many years ago, and as I recall the prop was certified as primary structure - i.e. it should never fail - because if they lost a prop at power the resultant imbalance could fail the wing structure.
Then again, I don't think the structural cert requirement for the props included impacting a rock wall...
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Old 19th Oct 2019, 23:09
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due to the aerodynamic properties of a prop blade, the trajectory is rather unpredictable
Like all blades, the only aerodynamic properties it has after release is drag. If the prop has no outer case to guide it or other blades to interact,, It will go aft
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Old 19th Oct 2019, 23:12
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Originally Posted by Airbubba View Post
The runway is now charted as 4500 feet long. Was it lengthened when it was paved? I remember seeing those Alaska B-737's with the gravel kit in ANC years ago. There are still a couple of B-734 combi's flying for the Department of Energy carrying nuke materials and commandos to guard them.

Would the Saab 2000 be category B for circling?
Bubba, did you notice the displaced thresholds on either end?
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Old 19th Oct 2019, 23:50
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Originally Posted by lomapaseo View Post
Like all blades, the only aerodynamic properties it has after release is drag. If the prop has no outer case to guide it or other blades to interact,, It will go aft
But it will have a significant forward force on it up to the point where it releases - so it will initially start moving forward. Combine that with the variable affect of forward speed (anywhere from static to the max forward speed of the aircraft) and where the prop might impact the fuselage a significant distance away and you're talking a rather large potential impact area.
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Old 20th Oct 2019, 00:50
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Originally Posted by Lake1952 View Post
Bubba, did you notice the displaced thresholds on either end?
I did. It looks to me like the runway length (TORA) is 4500 feet on the approach plate posted earlier. The LDA is charted as 3900 feet. Did the 4100 feet come from Wikipedia or an old approach plate perhaps?
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Old 20th Oct 2019, 01:08
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Airport diagram in a several year old AOPA airport guide.
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Old 20th Oct 2019, 02:12
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Originally Posted by tdracer View Post
But it will have a significant forward force on it up to the point where it releases - so it will initially start moving forward. Combine that with the variable affect of forward speed (anywhere from static to the max forward speed of the aircraft) and where the prop might impact the fuselage a significant distance away and you're talking a rather large potential impact area.
the forward force is "lift" and like a leaf that goes to zero in much less than a second as it stalls. The forward speed of the blade is then matched by the forward speed of the aircraft and that leaves the unbalanced force of fore and aft drag relative to the aircraft
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Old 20th Oct 2019, 02:21
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Is this the second U.S. Part 121 passenger fatality in the decade since the Buffalo Colgan Air 3407 crash?
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Old 20th Oct 2019, 02:43
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Originally Posted by lomapaseo View Post
the forward force is "lift" and like a leaf that goes to zero in much less than a second as it stalls. The forward speed of the blade is then matched by the forward speed of the aircraft and that leaves the unbalanced force of fore and aft drag relative to the aircraft
Yes, but the momentum of a propeller blade is significant, and what if you don't have a meaningful forward speed when it lets go (e.g. takeoff power setting)? A prop can move a long way in that fraction of a second before drag takes over. If you're going to try to protect the fuselage, you need to assume it might go forward from the plane of rotation.
For uncontained engine failures I think the assumed scatter trajectory was +10/-10 degrees for high energy debris (-30 degrees for low energy debris IIRC). For a released propeller blade think you'd need assume something like +10/-30 degrees - given the distance from the engine to the fuselage that's a pretty large chunk of fuselage you'd need to protect.
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Old 20th Oct 2019, 03:23
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And then, of course, it could be providing reverse thrust ... I don't know whether or not the SAAB 2000 has reverse thrust (beta) capability, but I believe the SAAB 340 does.
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Old 20th Oct 2019, 03:40
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I'm reasonably sure it has reverse beta capability - it certainly did on the installation I was involved with (the engine was an Allison at that time - which was bought by Rolls about the time I left the project).
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Old 20th Oct 2019, 04:56
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PADU 180156Z 30021G27KT 5SM -RA BKN039 06/02 A2953 RMK AO2 PK WND 30027/0154 RAB41 SLP004 P0002 T00560017=
PADU 180056Z 31011KT 10SM FEW034 BKN047 BKN060 07/01 A2950 RMK AO2 SLP995 T00720011=

It looks from the photo they landed rwy 13. can anyone confirm....?
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Old 20th Oct 2019, 06:43
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the momentum of a propeller blade is significant
Plenty of experience around, one example.
Eastern Air Lines Flight 611 originated at Boston, MA, for Miami, FL, with stops scheduled at New York-LaGuardia Field, NY, and West Palm Beach, FL.
Takeoff from LaGuardia was at 10:09 and the flight climbed to the cruising altitude of 22.000 feet.
At about 13:09, the No.3 propeller failed and a portion of one blade was thrown through the fuselage. It entered the lower right side at the galley section, severing control cables, electrical wires and engine controls, came up through the floor, fatally injuring a purser and left through the upper left side. A momentary fogging of the cockpit resulted due to the sudden depressurization of the fuselage. Heavy vibration was felt and all of the flight and engine instruments became either inoperative or impossible to read. Power was reduced and a rapid descent was started. An attempt was made to feather No.3 engine and orders were given to prepare for ditching.
An estimated one or two minutes after the failure of the No.3 propeller the front portion of No.3 engine and some of its cowling fell free of the aircraft. Concurrently the heavy vibration stopped.
A fire followed in No.3 nacelle but quickly extinguished itself. The crew set course to the Florida coast. At 13:12, the aircraft could no longer transmit because of failure of electrical power.
At the 12,000-foot level the descent was stopped. It was then found that controlled power was available from Nos. 1 and 2 engines, that No. 4 engine was running, although it could not be controlled by its throttle and that No. 3 engine had stopped.
Near the coast low clouds prevailed and the aircraft was let dawn visually to about 1,000 feet altitude, as most of the flight instruments remained inoperative.
The airport at Bunnell. FL, was sighted and circled. All emergency doors and exits were opened on approach and as the aircraft passed over the boundary of the runway and landing seemed assured, the ignition switch of No. 4 engine was cut. Brakes were applied hard during the landing roll causing one of the left tires to blow out.
When the aircraft stopped, fires started in No.4 engine and in the right landing gear. Both were quickly extinguished..
All passengers were evacuated.
https://aviation-safety.net/database...php?Event=ACET
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Old 20th Oct 2019, 09:48
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Originally Posted by tdracer View Post
But it will have a significant forward force on it up to the point where it releases - so it will initially start moving forward. Combine that with the variable affect of forward speed (anywhere from static to the max forward speed of the aircraft) and where the prop might impact the fuselage a significant distance away and you're talking a rather large potential impact area.
i don't think that's necessarily the case. The same principle applies to ice being shed from a blade as does to the release of the blade itself (apart from the vastly different amounts of energy involved, obviously).

In the former case, airframe manufacturers reinforce a relatively small length of the fuselage in the plane of the prop, because that's the part of the cabin that's at risk from ice being shed. Exactly the same applies to the trajectory of a departing blade, except of course that's there's no hope of stopping it if it's heading for the fuselage (which is why it's not supposed to happen).
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Old 20th Oct 2019, 11:18
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S2000 does have beta reverse and excellent short field performance. It's so well (over)powered the yaw damper is on the MEL...
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Old 20th Oct 2019, 15:50
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Originally Posted by Airbubba View Post
Is this the second U.S. Part 121 passenger fatality in the decade since the Buffalo Colgan Air 3407 crash?
The lady who was sucked out the window on SWA?
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Old 20th Oct 2019, 16:07
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That's what I'm thinking is the only other Part 121 passenger fatality in the past decade. FedEx, UPS and Atlas have had fatal freighter crashes since the Colgan mishap but is this only the second passenger fatality in this time frame?
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Old 20th Oct 2019, 16:44
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Here's a passenger's account of the Pen Air landing from a KUCB news article.

Unalaska Passenger Recounts PenAir Plane's Crash Landing
By Nathaniel Herz Oct 18, 2019

Before Thursday night’s plane crash, the PenAir pilot had missed his first attempt at landing flight 3296 in Unalaska. So he circled around for a second try.
Patrick Lee, 57, was on the plane returning home with his wife, daughter, and granddaughter.

He said the approach was bumpy. The engines reversed and the flaps went up. But the plane never slowed down.

“I looked out the window and I could see the terminal, and he was flying to the terminal,” said Lee on Friday morning. “I yelled to my wife, ‘He’s not going to stop — we’re going into the water!’ She yelled at my daughter to hunker down and hold on to the baby as tight as possible, which she did.”

As the Saab 2000 twin-engine turboprop, with 42 people aboard, hurtled toward the water at the end of the runway, the pilot jerked the plane to the right, said Lee. It slid across the road before teetering to a stop on a rocky bank just above the water.

In the process, something — Lee thinks it was debris — crashed through the side of the plane above where his daughter Cody was sitting, with her baby in her lap. The two weren’t severely injured, but a man sitting nearby was knocked unconscious.

Eleven passengers were ultimately taken to the Iliuliuk Family and Health Services clinic, with injuries ranging from “minor to critical,” said a statement from local officials. One passenger, David Oltman, 38, died from traumatic injuries suffered during the crash, and another was medevaced back to Anchorage for treatment.

Unalaska’s 4,500-foot runway sits below Mount Ballyhoo with water on both sides. Pilots often face strong winds, and they’re sometimes forced to divert to a longer jet runway in the community of Cold Bay, nearly 200 miles northeast.

Lee, who runs a heavy equipment shop and has lived in Unalaska for more than 30 years, compares the Unalaska runway to landing on an aircraft carrier. He and his family were returning from a trip to Idaho for medical appointments and seeing friends.

He said the PenAir flight was smooth until it ran into turbulence on its approach to the airport, as it descended below the clouds. Even so, he said, “We’ve landed in far worse weather.”

On the pilot’s first attempt at landing, Lee said, he came higher than normal. “I could look at the ground and knew he was going way too fast,” he said.

After circling around Mount Ballyhoo, the pilot lined up again. He hit the ground “a little hard,” though not unusually so, said Lee. But “it was almost like he didn’t have brakes.”

“It was either that, or he was maybe thinking he could pop back up again,” he said.

The plane ran off the end of the runway and the pilot swerved, which Lee said likely stopped it from sliding into the water.

“It was a pretty violent crash,” he said.

Lee said only one of the plane’s emergency hatches would open, and passengers focused on unloading the women and children onboard, including 11 students from Cordova’s swim team, which was visiting for a meet.

They also tried to move the unconscious man before emergency responders took over, he said.

Lee’s granddaughter had a little bump on her head, and his daughter Cody’s hand was smashed. She went to the clinic afterward to get it checked out, but it was so busy that the family left to allow staff to help more seriously injured passengers.

Lee credited the quick action of volunteers and other emergency responders.

“They were there fast,” said Lee. “The community really came together.”



https://www.kucb.org/post/unalaska-p...-crash-landing

The plane has been removed from the scene and put on a barge.


Laura Kraegel/KUCB

A cynical but possibly accurate reader comment on one of the news sites:

They'll take a year and spend $30 million on the investigation and come up with the conclusion that the pilot should have landed into the wind.
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Old 20th Oct 2019, 17:45
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Originally Posted by tdracer View Post
Yes, but the momentum of a propeller blade is significant, and what if you don't have a meaningful forward speed when it lets go (e.g. takeoff power setting)? A prop can move a long way in that fraction of a second before drag takes over. If you're going to try to protect the fuselage, you need to assume it might go forward from the plane of rotation.
For uncontained engine failures I think the assumed scatter trajectory was +10/-10 degrees for high energy debris (-30 degrees for low energy debris IIRC). For a released propeller blade think you'd need assume something like +10/-30 degrees - given the distance from the engine to the fuselage that's a pretty large chunk of fuselage you'd need to protect.
Your summary is fine, Not practical to protect so lower your window shade and don't think about it

Don't confuse momentum fore and aft with polar moment of inertia because the fore and aft considerations are only in regard to the fuselage which is also moving with the prop
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