Seaplane down off Miami Beach....

"Flyingmonk" wrote in message
ups.com...
Toks wrote:
Perfect evidence on why you shouldn't trust media that much!

Well, I never really trusted them.

Don't trust them if you want, but don't blame them for this one.
The infants are not ticketed passengers and therefore are not listed on the
manifest given to the media.

wrote in message
ups.com...
I'm wondering if fitting turbine engines on the old airframes
didn't pull something loose in the wing/mount.

Turbines run a whole lot smoother than the round Pratts that were on
originally. They don't have the power pulses that radial engines have.

I assume he was referring to the increased thrust that was probably obtained
with the turbine installation, which would create higher forces on the
structure transmitting that thrust to the airframe.

Of course, one would think that in a turbine retro-fit, that structure would
be upgraded to compensate. Hopefully, that's not actually the problem.

But I don't think Otis was suggesting that turbines would cause more fatigue
due to vibration than the original engines.

Pete

I assume he was referring to the increased thrust that was probably obtained
with the turbine installation, which would create higher forces on the
structure transmitting that thrust to the airframe.

I assumed the same. The round Pratts were 550hp engines, and the STC'd
PT6A-27 engines are flat-rated to 650hp. While the increased thrust
might add stress, my assumption was the weight reduction of the
turbines and their much smoother operation might nullify the power
increase as it relates to airframe stresses. It seemed a safe
assumption that that's what he was suggesting.

wrote in message
oups.com...
I assume he was referring to the increased thrust that was probably
obtained
with the turbine installation, which would create higher forces on the
structure transmitting that thrust to the airframe.

I assumed the same.

Curious you would introduce "run a whole lot smoother" and "power pulses"
then, if you thought those issues weren't relevant. Very odd. Even
stranger that those issues were the sum total of your rebuttal to his post.

The round Pratts were 550hp engines, and the STC'd
PT6A-27 engines are flat-rated to 650hp. While the increased thrust
might add stress, my assumption was the weight reduction of the
turbines and their much smoother operation might nullify the power
increase as it relates to airframe stresses. It seemed a safe
assumption that that's what he was suggesting.

I don't see how the smoothness of the operation of the engine relates.

As far as the weight reduction goes, if anything that would exacerbate the
problem, especially if that weight reduction is permitted to be moved over
to useful load. A heavier engine will dampen the initial acceleration (a
certain amount of the thrust is applied to accelerating the engine, rather
than the airframe to which it's attached), while a heavier airframe (ie
higher useful load) will allow higher forces to occur during that initial
acceleration.

Of course, once acceleration is relatively constant, the only real
difference is the difference in thrust, but again 100 more hp certainly
translates to more acceleration, and thus more force on the airframe.

All that said, as I mentioned before, I would expect certification of the
engine to take all of that into account.

Pete

One news report was watching last night mentioned 'the NTSB is attempting to
recover the cockpit voice recorder'. Are these small charter lines equipped
with those?

Peter Duniho wrote:

A heavier engine will dampen the initial acceleration (a
certain amount of the thrust is applied to accelerating the engine, rather
than the airframe to which it's attached), while a heavier airframe (ie
higher useful load) will allow higher forces to occur during that initial
acceleration.

Really?

Just how elastic do you think the connections between the airframe and
the engine are? When it comes to acceleration, they better form pretty
much one piece, don't you think?

Gross weight is what we accelerate, not components.

Or are you speaking metaphysically?


Jack

FAR 135 and 121 require cockpit voice recorders on turbine
powered aircraft. They are very simple, just a microphone
and an armored box.


--
James H. Macklin
ATP,CFI,A&P



"Michael Ware" wrote in message
news | One news report was watching last night mentioned 'the
NTSB is attempting to
| recover the cockpit voice recorder'. Are these small
charter lines equipped
| with those?
|
|

"Jay Honeck" wrote

The wing clearly departed the airframe before the crash. I wonder if
these
old birds are simply fatigued?

I wonder about catastrophic unconfined engine failure, severing the spar.
There was an account of the sound and sight of an explosion before the wing
departed, wasn't there?
--
Jim in NC

Curious you would introduce "run a whole lot smoother" and "power pulses"
then, if you thought those issues weren't relevant. Very odd. Even
stranger that those issues were the sum total of your rebuttal to his
post

Ya got me there Pete... nothing escapes your eagle-eyed gaze, eh?

Not really sure where I was going with that. On reflection, Otis' post
would suggest the higher power turbine conversion might have have an
adverse effect on the old Mallard airframe, even though as you
mentioned the STC should include reinforcing mounts, spars etc. to
allow for the increased stress on the airframe. If anything, I'd guess
the smoother running turbines should stress the airframe less than the
throbbing & vibrating radials in spite of their higher power.

(Disclaimer: I'm not an engineer, just an aero turbine analyst)

Jay

A monday morning WAG.

Turbine (disk) blew up and destroyed enough of the wing structure that
it failed.

Fuel tank(s) in wing then dumped fuel on hot parts of turbine and
caught fire.

Wingless (one wing) fuselage impacted water and broken off wing
floated down burning until it hit the water.

Lets see if my years of experience with accidents guessed right on
this bad accident.

Big John
`````````````````````````````````````````````````` `````````````

On Tue, 20 Dec 2005 14:08:24 GMT, "Jay Honeck"
wrote:

My guess is that they had a loose or broken fuel line,
caught fire and the fuel vapor exploded and the fire melted
the spar enough for it to fail.

Boy, I sure hope that's "all" it was. (Who'd ever think we'd be saying that
kind of stuff?)

With everyone describing an "explosion" (which the video tends to
support) -- and Chalk's not having to do much in the way of security
screening, as a small carrier -- this could easily have been some kind of a
nut-job with a shoe bomb and a "cause".

And *then* we'd start seeing all sorts of stupid proposals for "enhanced
security" that we don't want or need.

Sad to say, a mechanical problem is the best-case scenario.