From The Cliff Mass Weather Blog
Cliff Mass
A tragedy occur yesterday (Sunday, September 4) with the crash of a float plane over Mutiny Bay of southern Whidbey Island just after 3 PM (see map below, the star indicates the accident site).
The aircraft was en route from Friday Harbor to Renton. Like all aircraft accidents, it will be examined comprehensively by the National Traffic Safety Board (NTSB), which is very valuable. Flying is extraordinarily safe because the causes of past accidents are painstakingly investigated and the system is improved as a result.
Several folks have asked me whether there was a meteorological contributor to this terrible occurrence, and after examining the data, I did find something significant.
Let me show you now.
During the exact time of the accident a front was moving through the region, and this passage, interacting with local terrain, produced a very sharp low-level wind shift in the lee of the Olympics.
Here are the surface observations at 3 PM. To the south of the accident site the winds were from the south (the barbs face the direction from which the wind is coming) while to the north the winds were from the northwest.
Temperatures were much warmer in the southerly flow compared to the northerly flow.
Such convergence of low-level airflow often accompanies frontal passage over Puget Sound and often produces a band of clouds and precipitation: the infamous Puget Sound Convergence Zone.
This transition can be very sharp, as a cool wedge of cold, northerly air undercuts and pushes aside warmer southerly flow (see schematic vertical cross section below).
To see how sharp the transition was, let me show you the observations from a surface observing location (Bush Point), just north of Mutiny Bay (courtesy of the WeatherUnderground).
The bottom panel is wind direction. Wow… a VERY sharp, almost instantaneous wind shift from southerly to northerly at 3 PM. The top panel (red line) shows temperature, which plummeted after the windshift. Other nearby observations showed the same thing.
The visible satellite image 3 PM shows a band of clouds associated with the windshift line.
Really not that impressive and the weather radar showed no active precipitation with the windshift line (see below).
3 PM weather radar
The vertical structure of the leading edge of the wind shift line (illustrated by the figure above) would be a narrow wedge of northerly winds at low levels, with the southerly winds right above. High-resolution UW WRF model simulations indicated such a structure (see simulated sounding with height at 2 PM for the point in question). The Camano Island radar noted the same thing.
With all this meteorology in mind, let’s get back to the float plane accident. According to flightradar24 (below), the plane was flying around 600 ft AGL, climbed to around 1000 ft, and then rapidly lost altitude at 3:09 PM (2209 UTC). Aircraft speed was around 125 knots earlier and then lost speed just after 3:08 PM.
Flying south they had the northerly winds behind them. Then they hit the convergence zone line. Moving from northerly to southerly winds could explain their rapid loss of speed. Although their ground speed would decline, their airspeed could increase, causing more lift. Did that contribute to their increasing elevation at the end?
Not only did the wind reverse suddenly, but there would have been considerable turbulence due to the strong vertical wind shear associated with the convergence/windshift line.
Did this have anything to do with this accident?
I do not know. All I can say is that the accident occurred in an area of an active wind shift and potential low-level turbulence. Is it a coincidence that the accident occurred simultaneously with their traversal of the big wind shift?
Another tragic float plane accident.
Is it just me, or does anyone else detect an increase in float plane downings in recent times?
How did you “detect” it? Any sources, any statistics, or is it just some feelz?
Random news stories.
Should I cobble up a quick hypothesis and apply for a research grant?
Start with the conclusion that it wuz Climate Change™ wot dunnit and work your way back to the grant application.
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Be sure to note your PhD in Feminist Glaciology and success is guaranteed.
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I suppose the field work will have to be conducted on Bali. Like the drunk looking for his keys under the lamppost because the light is better, Bali has better weather than the crash site, so the answers will more likely to be found there.
Yes. Watched a doco last night about Greenpeace exposing the “bomb fishing” that pulverizes coral reefs in marine preservation zones throughout Asian and African coasts.
Yet the UN wallahs don’t go there to berate the governments.
Instead they fly first class to Australia to view 1 / 2999th of the Great Barrier Reef from a glass bottomed boat for half a day, then berate Australia for not doing enough to preserve the GBR.
They should use green walnuts.
AP story by Martha Bellisle on Sept 6 quoting “Jon Gabelein of South Whidby Fire/EMS told KOMO, witnesses on shore reported seeing the plane nose dive into the water.”
That plane has a history of structural failures. A severe wind shear could cause that.
I saw shocking damage from a micro-burst in the mountains years ago. It looked like a giant foot stomped on the forest flattening it like a pancake.
Not true. DeHaviland Otters are among the sturdiest and most reliable aircraft in the world. But they are flown in highly challenging conditions, being a common heavy duty bush plane, that most aircraft do not fly in.
Aircraft don’t just fly apart, especially at low altitude, unless they fly into a thunderstorm cell, which was not reported in the area (and is rather uncommon in the Puget Sound area). NTSB will investigate, and determine most probable cause(s), and silly speculation is just a waste of time.
Looks like this one has a history:
https://youtu.be/J2MqTGx3Xq4
“Aircraft don’t just fly apart”
Sometimes they do. Cliff identified a possible wind sheer which is a possible cause of that.
“The failure of the outboard and inboard lug plates led to the separation of the righthand wing lift strut from the wing and, subsequently, the separation of the right wing from the aircraft. … Crash of a De Havilland DHC-3T Otter in the George Inlet: 1 killed. Date & Time: May 13, 2019 at 1221 LT Type of aircraft: De Havilland DHC-3 Otter”
There may have been a structural issue with the tail, also. I’ve flown the single engine Otter, and flew for a commuter airline in the Seattle are. If you are not expecting that Convergence zone, it can be a surprise.
Could the additional lift from the convergence zone caused the plane to
climb, thereby dropping the airspeed below stall speed without the pilot
realizing what was happening? The Seattle terminal area is quite busy
with a lot of traffic & many different airports so it would be quite easy to
keep your eyes peeled outside the cockpit looking for traffic & visual
navigation cues vs monitoring instruments as one would normally do in a less busy environment.
He would have been on Whidbey NAS radar, I wonder if they would have any info.
No, it works thegotgerway around. Trasitioning INTO a headwind causes a plane to balloon up as it suddenly has excess airspeed. It woukdnt then normally crash, just gain height undexpecdely.
Its when you lose airspeed – i,e, lose a headwind or gain a tailwind, that you fall out of the sky.
But the wind shear associated with this weather condition would have led to massive turbulence at the point the air masses met. And anything is possible in terms of up/down and sidedraughts.
Methinks turbulence/wind shear is the winner, in this case. Thanks.
I have some time in floatplanes and they are a different animal with all the drag hanging out below. Also they can also be a little underpowered in some circumstances. Could the weather be a factor? Absolutely. Was it? As mentioned in the article we really have to wait on the NTSB. I’m sure they will do a professional and thorough analysis, but even then sometimes they can’t figure what exactly happened.
Most of the Otters currently in service have been retrofitted with PT-6A-27 or 34 turboshaft engines, with horsepower ratings about double to triple the SHP of 600 hp radial engines that were original equipment. Therefore not likely to be under powered – they’re heavy haulers well suited for commercial float plane ops as well as heavy duty bush flying.
My training for find the root cuase of a problem said weather could not never be the root cuase. If you correct the root cuase of a problem it will not happen again. Clearly you can not correct the weather.
Yesterday I was out for a walk in Ocean Shores Washington state. It was windy. A small single engine plane was on a glide pattern to land. Thought it was a crash and burn situation. Said outloud, “What is this clown doing?”
There was a lud engine roar and the plane headed for someplace else.
Last month I was helping a friend step a mast on a sailboat. I did not like the looks of the clouds, so we took a break. Then it opened up and I ran from shelter. He made fun of me.
He grew up in SanDiego surfing and had never seen hail, I grew up in the midwest hail and tornadoes is why you watched the clouds.
Bottom someplaces have mild weather and not prepared for anything else.
It is called being stupid.
Wind shear. Looking at the wind plots showing 180 degree change. Would be interesting to see the METAR and where the front was. Pilots are taught this. So probable.
Good detective work.
Just one more thing for alarmists to blame on
weatherclimate change™.That ole climbit chainge hasa lot to anser four.
In today’s COVID-and-“vaccine”-saturated world, it is not beyond the realm of possibilities that the pilot had received the “vaccine” and “boosters” and suffered a debilitating adverse effect and became incapacitated. The reports of such happenings are increasing at an alarming rate.
The latest term being applied to these mysterious adverse effects and especially the unexplained deaths of perfectly healthy and in many cases amateur or professional athletes in great condition is “Sudden adult death syndrome,” also known as “SADS”. It occurs when a person under the age of 40 years old suffers a sudden death without a known cause and is determined to have been the cause of death after an autopsy and toxicology screen (drug test). SADS causes a cardiac arrest when the heart rapidly stops pumping, and the body loses heart function, breathing, and consciousness. Virtually all of the victims have received more than one COVID shot/booster.
https://health-desk.org/articles/what-is-sudden-adult-death-syndrome
Rampant speculation.
Have you seen the article over at Epoch Times about the huge number of clots being found by embalmers? https://www.theepochtimes.com/embalmers-have-been-finding-numerous-long-fibrous-clots-that-lack-post-mortem-characteristics_4696015.html?utm_source=ref_share&utm_campaign=navigator&rs=SHRNBSWT
Wind shear is a fairly common phenomenon associated with aircraft loss of control accidents (LOCA) for aircraft flying relatively close to the ground (especially common in landing or take off where the aircraft obviously is very close to the ground), But in most if not all instances where wind shear was a contributing factor to a LOCA it was due to flying in an area with headwinds that suddenly shear to tailwinds, the opposite what is described here. In that circumstance – low effective airspeed and close to the ground, if the aircraft enters an aerodynamic stall, the pilot may not have sufficient altitude to recover.
I’ve personally experienced low altitude wind shear on final approach to landing at low altitude, when flying in the mountains, just above a deep canyon, on a windy day. It certainly got my attention, and I learned a valuable lesson as a result – don’t fly in the mountains on windy days!
And this problem has been recognized for 80 years. I recently read an article in an 80 year old flying magazine about this very problem. Trouble is, very few people (pilots) pay attention, because it’s not frequent. I regularly land at a strip with a large obstruction at one end, and when coming in from that direction, always have to add a lot of power to prevent dropping out when the wind is high, and the wind rolls back from the obstruction turning a headwind into a sudden tailwind.
Even highly experienced, knowledgeable, and safe pilots get tripped up flying in mountainous terrain on windy days. The guy who literally wrote the book on mountain flying – Sparky Imeson – died flying in the Rockies on a windy day. I personally knew two acknowledged experts with more than 30 thousand hours each in the cockpit as former military and airline pilots and flight instructors killed in such conditions. They both flew on windy days in varied terrain when they shouldn’t have. Wind sheer is a proven killer.
Juan Browne (blancolirio) reports: “DHC-3 Turbine Otter N725TH Crash 4 Sept 2022”
“From high to low, look out below.” is a familiar adage for pilots flying in “indian country”. It refers to the indicated altitude on the aircraft’s altimeter, which is derived from static barometric pressure. So, when you fly from a high-pressure cell to a low-pressure cell your altimeter is going to read higher than your actual altitude agl (above ground level). You’re skimming the tree tops, but relying on your instrument, you falsely believed that you had 400ft. agl under your wing. Been there done that! In this case, it was the opposite. I would think the aircraft went from low to high pressure, but most critical is that the aircraft hit a wall of extreme “sink”, a steep downdraft, to which if you weren’t ready for it, drop the nose and pour on the power, you could literally fall out of the sky.
And Dan Gryder of “Probable Cause”
Note: There appear to be issues with this aircraft series prior that were not addressed by the NTSB, even after defects were found.
A guy posting vids on the internet is not a reliable source of anything. And I totally reject any and all commentary from some clown who based upon nothing but an hour’s worth of internet research and no personal experience with either the aircraft (has never flown one hour in an Otter as pilot in command), the operators, the maintenance facility, or the conditions that day during the accident flight. This guy is a know-it-all crank.
Not that NTSB is the sole source of expertise here.
Three of the incidents he cited were not the accident aircraft, as you claim. They were just other Otters.
Again, these aircraft are flown quite often in very challenging conditions, very different than the typical airliner. What the status of the maintenance of the aircraft, the conditions of the flight, the mental state of the pilot (even the greatest pilots have off days – the guy who quite literally wrote the book on mountain flying, the bible of all mountain pilots, himself was killed flying in bad conditions in the Rockies), and a whole host of other potential contributing factors is all at this point totally unknown by this internet clown, and us, and probably won’t be known for months by NTSB as well as airframe experts for the Otter aircraft who will certainly be engaged in the NTSB investigation.
The internet – where everyone is a self- proclaimed expert on everything all the time.
The accident happened in cruise, so the change in wind direction is not likely the direct cause, because the aircraft is operating well above stall speed. But, wind shear often has associated turbulence and that’s a possibility. At any rate, yeah — need to wait for more info.
If you want to view a blog with pilot’s hypothesizing about the probable cause, see here:
http://www.kathrynsreport.com/2022/09/de-havilland-canada-dhc-3t-turbine.html
Salt environment – Aluminum – Turbo-prop retofit on an float plane with prior, I say PRIOR issues – yeah, “weather”.
Actually, I have been in cruise flight many times where wind shear affected my flight. All it takes is to be cruising downwind of any mountain range on a windy day, even as much as 20-30 miles from the mountain crest. That’s something that all experienced mountain flyers quickly learn, if they survive their first encounters before they realize what it means and provide themselves plenty of excess altitude above ground should they encounter a rotor.
What happens is strong winds over mountains result in “rotor” winds (literally, winds that swirl around like a sort of wind pipeline (akin to a “pipeline” wave near the beach that surfers love to surf). Depending upon where the aircraft is with respect to those rotors, it can result in a sudden wind shear, from down draft to up draft, and from headwind to tailwind, within a relatively short distance (hundreds to thousands of feet).
I flew through a rotor once where I was cruising at 3 thousand feet AGL in parallel to a mountain chain on a windy day, probably 20 miles downwind of the crest. Suddenly I found myself in a downdraft with a descent rate of 1,500 FPM. I applied full throttle, dropped in partial flaps to lower my stall speed, and the aircraft bottomed out less than 1 thousand feet AGL. Seconds later, the downdraft was gone and I was back to climbing back to my cruise altitude – plus another 2 thousand feet to give me the margin that I lacked moments earlier.
A heavily loaded aircraft near its placarded max gross weight, flying even 1,000 ft AGL, can easily be either down-drafted right down to the ground, or the water surface, or encounter a sudden tail wind putting it into an aerodynamic stall which can then result in a spin right down into the surface.
This particular flight by the Otter was conducted on a windy day, with mountains located virtually all around Puget Sound, so avoiding being downwind of mountains when the wind suddenly shifts, and any rotors that may have formed, might be a near impossibility. As I understand it was a heavily loaded flight too.
I do not claim at all to know the cause of this crash … but certainly winds and other factors (such as aircraft loading and cruise altitude being relatively low) cannot be dismissed out of hand as some commenters are trying to do here in this thread.
The chart demonstrates a possible, theoretical and approximate 20 mph drop in airspeed. It is unlikely that this aircraft would be flying within 20 mph of its stall speed at any time other than takeoff or approach/landing. Also, its apparent altitude of 1,000 feet is more than enough to recover from an aerodynamic stall.
Other possible causes — Center of gravity too far aft; Structural failure; Pilot incapacitation; Passenger interference with controls.
Nine passengers seems like a lot for a Beaver.
Update: “The National Transportation Safety Board said the plane was a de Havilland Canada DHC-3 Turbine Otter, a single-engine, propeller plane, reported Seattle Times.”
https://bit.ly/3x3HnBO
(IBTimes)
Turbine Otters generally have plenty of power and legendary reliability. A simple engine failure should have resulted in an uneventful landing on the water.
The chart is of ground speed not airspeed. We don’t know what the airspeeds were, and likely never will know since these aircraft don’t have flight data recorders.
As for 1,000 ft being plenty of room to recover, that’s actually not true at all. If an aircraft gets caught in a strong downdraft due to a rotor wind coming off a mountain range on a windy day, 1,000 ft may not be anywhere nearly enough altitude to recover (I’ve personally experienced much larger altitude losses, 2,000 ft or so, in such conditions). Plus we don’t know how the pilot reacted if his aircraft did enter a stall. If he did not immediately lower the nose, apply full power, and maintain coordinated flight, it would have been extremely easy to enter a full spin which generally requires at least 2 to 3 thousand feet to recover from.
That’s why flight instructors generally require their students to practice stalls and stall recoveries at a minimum of 3,000 AGL.
Duane wrote, “I’ve personally experienced much larger altitude losses, 2,000 ft or so, in such conditions.”
Say aircraft type.
Duane also wrote, “Plus we don’t know how the pilot reacted if his aircraft did enter a stall. If he did not immediately lower the nose, apply full power, and maintain coordinated flight … it would have been extremely easy to enter a full spin which generally requires at least 2 to 3 thousand feet to recover from.”
So … this crash required that the pilot did nothing he/she was taught to do (apply full opposite rudder, lower the nose, apply full power) and did several things he/she was taught not to do. I suppose that’s possible.
Maybe he/she ran out of fuel or experienced some other type of engine failure and blew the landing. Maybe some one or some thing came loose inside the airplane resulting in a shift in the CG that rendered the aircraft uncontrollable. Maybe something came apart. Maybe the pilot suffered a myocardial infarction.
We may never know.
Duane wrote, “The chart is of ground speed not airspeed.”
I was referring to Cliff’s chart which was of wind speed. Cliff then stated that a sudden change in wind direction could, with no other changes, result in a drop of airspeed.
In my experience most pilots respond to a sudden drop of airspeed by adding power, lowering the nose or both. This is why airplanes are not constantly falling out of the sky while on short approach in gusty weather.
But they occasionally do fall out of the sky while on approach in gusty weather. A very extreme example which doesn’t have much to do with this accident …
“As the plane flew into strong headwinds, the pilot slowed the thrust, expecting an updraft to hold the plane’s altitude. Instead, there was a sudden downward wind shear, with a blast of wind from the tail. The Lockheed plane is relatively heavy and was not able to [add] thrust quickly in response.”
https://www.history.com/this-day-in-history/sudden-thunderstorm-causes-plane-crash
Stick to weather Cliff! The very mild shift in wind speed, or simply the wind shear did NOT cause this plane to crash. The speed on the ADS-B data is GROUND SPEED. When the plane is nose diving due to a structural failure, the ground speed is minimal.
Your suggestion that wind shear is a factor is unfounded, uninformed and without merit. (eyewitnesses heard a very loud bang just before it took a nose dive into the water)
https://www.youtube.com/watch?v=J2MqTGx3Xq4&t=126s (10 Dead in Fatal Sea Plane Crash – N725TH. Here’s Why.)
This plane, and sister planes have had a number of structural issues with the horizontal stabilizers. (the elevator, which controls pitch) And one of the sister ships had a crash in May and the NTSB listed cracks in the structure as the probable cause, where substantial damage and 8 injuries occurred.
Dan Gryder is an in your face curmudgeon who is a real pilot, airline transport rated, flight instructor and is fed up with the NTSB not doing it’s job and making proper safety recommendations. Here there were 4 prior incidents of this exact plane or it’s close sister ships of corrosion in the structure, affecting the pitch control, and they did not flag any recommendations to the FAA to mandate changes.
Dan’s done a sarcastic take on the NTSB calling his assessments the DTSB – but his analyses are right on, and don’t take 3 years to conclude they could not figure out what happened.
It is criminal for these obvious structural deficiencies in very old seaplanes, operating in salt water (salt water and aluminum do not get along), to get ignored or swept under the carpet by the NTSB for 4 serious past incidents which are related to this one.
Did wind shear provide the final straw that broke the camel’s back – perhaps, but it would have happened in short order with or without the added stress of a bit of wind shear due to the structural deficiency, demonstrated in this and it’s sister ships in the past, and inadequate safety monitoring or airworthiness directives from those past incidents!
In fact it did happen to the sister ship back on May 24, 2022 – structural failure of the elevator, caused a severe nose up attitude and it stalled (wings loose lift) at 300 feet AGL, and then it went into a 45 degree nose down attitude and impacted a forested region. (which if you look at the ADS-B data, is precisely what this plane did – a sharp nose up, then plunged into the water at a steep nose down angle)
Single Otters can handle 10-20 times more wind shear than was experienced.
Blancolirio is more diplomatic in his report on this accident, but also reveals witnesses hear a loud bang before the plunge:
https://www.youtube.com/watch?v=9vQJ6T9wmyM (DHC-3 Turbine Otter N725TH Crash 4 Sept 2022)
Blancolirio is a 777 pilot, who provides initial and final reports on accidents, and even he indicates it is most likely a structural failure, and many commenters on his video have direct experience with these kinds of planes and confirm that structural deficiencies exist and are addressed at other operations.
Finally the ADS-B data (transponder in the aircraft transmits altitude and ground speed to various ground receivers) shows the final dive reached around 5,000 feet per minute descent. This is 49.4 knots and the stall speed of the DHC-3 is 51 knots. So it was stalled as it dove into the water – with something like a 45 to 60 degree nose down pitch. At this speed, water is as hard as concrete. (condolences to those close to the deceased, but for the living, we must learn from this, which is why both Dan and Juan do their reporting to the aviating community)
https://aviationweek.com/business-aviation/safety-ops-regulation/searchers-find-wreckage-dhc-3-seaplane
More at the link.
NTSB Releases Preliminary Report on Seattle Seaplane Accident, Including Witness AccountsPlans are in the works for wreckage recovery in Mutiny Bay.
https://bit.ly/3dqRBFN
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