Wasaya caravan missing

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goingnowherefast
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Re: Wasaya caravan missing

Post by goingnowherefast »

"Event 1" is a pretty clear stall and into incipient stage of a spin, but initially recovered. Climb rate is increased at the cost of airspeed, airfoil is contaminated, so stalls at an (unexpected) higher than usual airspeed. There was no "shear" at 4500', that's over 3000' AGL. At best there was light turbulence due to stratocumulus clouds.
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pdw
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Re: Wasaya caravan missing

Post by pdw »

A steep pressure gradient to the 986hPa, southeast from YPL into southeast Lake Superior. The pirep of "ragged stratus" is an indicator of the resulting increased aircurrents above the "stratocumulus" moving along this pattern.
goingnowherefast wrote:"Event 1" is a pretty clear stall and into incipient stage of a spin, but initially recovered.
If I've interpreted right, the report stated "not sure" (not 100% understood) whether that was the 'intentional turn' or not.

The report doesn't seem to want to judge "not recoverable" for certain during "event 2", so that leaves open that it's also possible the flight was stable enough just before "event 1" .. where then having experienced the bleedoff-tendency (short period of decline during slight descent rate) ... immediately following the stiffer 'extra climbrate' (confirmed in the report).
Climb rate is increased at the cost of airspeed, airfoil is contaminated, so stalls at an (unexpected) higher than usual airspeed.
Yes.
______________
At best there was light turbulence due to stratocumulus clouds.
With the stratus, there is likely nothing convective nor sharply-advective up there (report concludes no moderate nor severe turbulence) in that climb-through setting; "light turbulence" is accurate there, even when more-sharply entering/exiting a different / faster air moving above this cloud.
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Sidebar
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Re: Wasaya caravan missing

Post by Sidebar »

The lesson here is that the airplane was severely contaminated with ice. That's why it stalled.

If you fly a Caravan and you encounter ice, don't continue flight in the icing! If there's icing forecast, don't depart.

All the discussion of wind shear and turbulence is not relevant. It was the decision to depart and then to continue flight in icing that caused this flight to crash.

As others have said, the company managers were a major contributing factor.
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MortyBubba
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Re: Wasaya caravan missing

Post by MortyBubba »

I understand that the caravan was not certified for flight into known icing and we keep mentioning that. I am curious how do you file a VFR flight plan at 5500 feet when to me it looks like a strictly IFR day?
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spongebob
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Re: Wasaya caravan missing

Post by spongebob »

MortyBubba wrote:I understand that the caravan was not certified for flight into known icing and we keep mentioning that. I am curious how do you file a VFR flight plan at 5500 feet when to me it looks like a strictly IFR day?
No filing necessary if you are on a flight itinerary and in uncontrolled airspace. Nobody outside the company would know in that case of what the plan for the flight was.
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justwork
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Re: Wasaya caravan missing

Post by justwork »

pdw wrote:Yet is not as simple as an icing encounter in perfectly smooth air.
Yes it is.
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pdw
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Re: Wasaya caravan missing

Post by pdw »

(that's a semi-colon after "air" .. that first part was only a portion of the sentence context)

Never-the-less, the affirmative statement "Yes it is." conceeds that your opinion is 'slim chance of recovery' at "event 2" ?

(I'm still hoping to find an answer of how the CAS & IAS is figured here, ... how it is proven / determined for this report, before continuing useful discussion on that point. It seems to me that on the charts the fluctuations ahead-of "event 1" are close to groundspeed.)
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Sidebar
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Re: Wasaya caravan missing

Post by Sidebar »

See section 1.16.1 of the report for an explanation of how the TSB used GPS and met info to calculate aircraft performance.

Based on my long ago aerodynamics classes, my understanding of the calculations are as follows. Wiith the GPS position and time they were able to figure out the ground speed and track. Using wind info, track and ground speed they worked out the TAS. From temperature aloft and GPS altitude you get air density, which is used to convert TAS to EAS (equivalent airspeed?). A correction for compressibility, and EAS becomes CAS.
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pdw
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Re: Wasaya caravan missing

Post by pdw »

(equivalent airspeed?)
"estimated airspeed" is used 7 times there in 1.16.1 .. [in paragraphs 3,4(x2),5(x2), 6 & 8 of that section].

( Also "estimated 104kts calibrated airspeed" in paragraph 3 of 1.16.1)
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Sidebar
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Re: Wasaya caravan missing

Post by Sidebar »

EAS as used in my post refers to equivalent airspeed.

I think the TSB probably used “estimated” because they were using met data from an observation done about 2 hours before the accident.
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pdw
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Re: Wasaya caravan missing

Post by pdw »

Sidebar wrote:I think the TSB probably used "estimated" because they were using met data from an observation drone about two hours before the accident.
"Estimated" component data which KCAS values are based on, starting at 9:03 (represented by the light green line of the TSB flight data chart above dark-green/groundspeed) is pretty close. Maybe is a bit faster AS at a couple of spots ...

The "radiosonde" component-info (chevrons between 2500' and somewhere just below 5000') are given North at 20-25kts (looks like) for/after the early altitude ("5kts-NNE"/lowest chevron) where the northerly course started around 2500ft around the left turnout. IMO there must be at least the 20kt spread between these two speedlines for the middle of this five minute northerly climb .. in-between 9:03:10 and 9:08:30.

The first track data "9:03 to 9:03:34" includes "800fpm" for 10-15sec and the "100ft" lost right-after, which is signature of some brief performance increase, yet still ends up only 240ft of net altitude gained in that 34sec segment.

Following the +/- fluctuation and after another five minutes of climb to 9:08:41 there is obviously performance decrease (shearlike) where the Cargo Caravan transitioned into lighter/warmer West component moving at/above 5000' (indicated by radiosonde-infochart/wind-chevrons) near where the climb-rate ceased. Such relativewind reduction going-on ahead-of "event 1" is a secondary climb-performance loss coming alongside the primary one (the lift-degrading icing buildup/encounter described in the report).
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pdw
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Re: Wasaya caravan missing

Post by pdw »

rxl wrote:This airplane has a deplorable safety record.
27 years old (1990) with 36,063 hours on the airframe.
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GyvAir
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Re: Wasaya caravan missing

Post by GyvAir »

pdw wrote:
rxl wrote:This airplane has a deplorable safety record.
27 years old (1990) with 36,063 hours on the airframe.
A more interesting number and more relevant to the initial comment would be the worldwide fleet hours.
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pdw
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Re: Wasaya caravan missing

Post by pdw »

Can you get an average?
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GyvAir
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Re: Wasaya caravan missing

Post by GyvAir »

pdw wrote:Can you get an average?
Tough to find real or current stats.

https://www.avbuyer.com/articles/jets-f ... -one-19970

8,400,000 fleet hours according to the above article from back in 2005.

7,000,000 hours/1522 produced to date = average of 2800


So, add 12 years of fleet flight time and 1000 new production units, minus retired and destroyed airframes and there's your average.

I'm sure it's been argued a thousand times that the Caravan accident statistics have more to do with pilot experience, mission type, runway conditions and the parts of the world that many of them operate in than the airframe itself.
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pdw
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Re: Wasaya caravan missing

Post by pdw »

GyvAir wrote:pilot experience, mission type
For this profile (mission type), namely the icing related accidents in the database of reports for this aircraft, there seems to be a mix of low and hightime pilots (pilot experience) in 60-70 that are in there.
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