An interesting theory

[elaw]

NTSB report apparently is out on the Caravan that crashed in Burley IA a while back. Our speakist Juan has an interesting theory on a partial cause of the accident: https://www.youtube.com/watch?v=EWCkzJEpcnw

Report (PDF): https://data.ntsb.gov/carol-repgen/api/ ... 104938/pdf

[3WE]

1. I infer that Dan Juan stole the light bulb? IMHOAHO, he is bat shit certifiably crazy and needs to be banned.

2. I call bullcrap that a sudden density altitude increase caused a loss of altitude.

3. One might cite procedures, that she was more than one dot low, and that maybe 98 feet is adequate by the book? 3a: Conversely the stacks are “right there” and the nose/panel possibly obscuring them was bad.

4. If I heard the weather right, she had not_challenging ceilings and not_the worst visibility: Could she have visually avoided the steam clouds and landed?

5. I find it very sad that she made a successful first approach, but did not_land…lost opportunity.

6. The video of her being nose-up, looks a little extreme- then again, maybe she saw she was aiming for the stack.

/3BS spewing

[ocelot]

The sudden increase in density altitude doesn't have to directly cause you to drop 100 feet; it just has to cause you to stall, which is quite plausible.

(1) if we suppose for the moment that the stack cloud was around 50C, that's a 15/13 increase in absolute temperature and thus (from the ideal gas law) a 13/15 decrease in density. If you're a bit slow already, that's definitely enough to create problems. What temperature was the stack gas? 50C could be too low, even in winter.

(2) one of the hazards of airframe icing is that the ice can break off and cause a sudden change in handling characteristics; if you are getting some ice buildup and you fly into a much warmer cloud, that can easily dislodge the ice, and in these circumstances there's no margin to recover from a sudden upset.

[3WE]

I’m, I think you mean 2/15 (or 2/13) increase in density altitude.

…and factor in whatever the stack is spewing- water is lighter than oxygen, thus less lift when you shove it down.

I still think that’s a bit far fetched…yeah, they said she got a little slow.

Additionally, hot gasses form updrafts…yeah, Gabe will say that increases AOA, but I’ve never been aware of a plane dropping significantly because you suddenly hit less dense air.

[3WE]

Am I the only one tragically laughing that Dan Gryder seems to have stolen the warning light from the stack?

[flyboy2548m]

I’m, I think you mean 2/15 (or 2/13) increase in density altitude.

water is lighter than oxygen,

WHAAAAAT?!!!!

[Gabriel]

I’m, I think you mean 2/15 (or 2/13) increase in density altitude.

water is lighter than oxygen,

WHAAAAAT?!!!!

Thank yo FB. With a single word you saved the forum from my 2-pages-long comment.

[3WE]

I’m, I think you mean 2/15 (or 2/13) increase in density altitude.

water is lighter than oxygen,

WHAAAAAT?!!!!

I got a beer on it flyboy. As a gas, by water is among the lighter molecules.

First: While I don’t think we put RH or dewpoint into our fancy E-6B computers for density altitude, the air is thinner/higher altitude on humider days.

Water is a lighter molecule: . Roughly 18 AMUs versus 28 for nitrogen and 32 for oxygen.

Fly your aeroplanie through helium at 1913 millibar pressure at 20C, you get a lot less lift than pure oxygen at 1013 millibar /20C. When the air is humid, there’s less lift as lighter individual water molecules have displaced heavier nitrogen and oxygen molecules. This is because your wing shoves basically the same number of molecules down. But the weight of the molecules matters. /fiziks and chemistry gas law stuff.

Now, for a confession- I’m not sure how clouds figure in when you are loaded with itty bitty droplets of liquid water. Maybe that blows it all up and I’m wrong.

By the way, it sure is creepy that Dan stole the beacon.

[3WE]

https://commons.erau.edu/cgi/viewconten ... text=ijaaa

…and Dan stole the beacon!

[elaw]

Dan Gryder seems to have stolen the warning light from the stack?

Did he blame it on the NTSB?

[flyboy2548m]

I got a beer on it flyboy. As a gas, by water is among the lighter molecules.

First: While I don’t think we put RH or dewpoint into our fancy E-6B computers for density altitude, the air is thinner/higher altitude on humider days.

Water is a lighter molecule: . Roughly 18 AMUs versus 28 for nitrogen and 32 for oxygen.

Which matters not one bit since it's not like she flew from pure oxygen into pure water vapor.

But carry on.

[3WE]

Which matters not one bit since it's not like she flew from pure oxygen into pure water vapor.

But carry on.

If you wish to follow the thread, I don’t think hitting a warm plume of smokestack gas is going to kill enough lift to stall the plane unless you are really hanging there basically at stall speed…dry air or moist air.

Even though we, with type-specific training on fixed pitch props and passively-aspirated engines, are taught to respect high, hot and humid and check the book of acronyms for performance figures.

They said she was a little slow, but don’t think it was that slow.

I’ll leave it to Gabe to run the numbers.

[3WE]

BUT

Is he basically correct that the gal did almost nothing wrong hitting a lightless tower that basically was in a reasonable, instrument-enhanced glide path?

[Hour-long video and I’ve only skimmed it]

https://www.youtube.com/watch?v=aRN3RJaW618

[3WE]

To clarify:

What I’m getting from DAN is the approach being insidiously bad.

The steepening approach path with horrendously bad timing causes the pilot to be ever so slightly behind…WITH VERY CRAPPY TIMING

Descending fat, dumb, happy and competently.

Ok, I’m high, I need to correct…look away briefly to check something…oh, I’m a little SPLAT!

(Yes, the tower height and steam obscuring stuff is huge).

PS: DAN Juan stole the beacon AND I don buy Dan JUAN’S density altitude theory.