Seaplane down off Miami Beach....

In article ,
"Morgans" wrote:

"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?

Snapping structures sound a lot like explosions -- especially to
nonexpert witnesses.

--
Remve "_" from email to reply to me personally.

The PT6 is mounted above and forward of the wing leading
edge, if the turbine had a failure, the bits and pieces are
not likely to impact the wing. But, if that happened
there will be positive evidence.

The PT6 is a pretty small turbine, they don't have many
problems internal to the engine.


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

--
Merry Christmas
Have a Safe and Happy New Year
Live Long and Prosper
Jim Macklin
"Big John" wrote in message
...
| 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.
|

"Jack" wrote in message
. net...
[...]
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?

For the sake of this discussion, it doesn't really matter. The difference
in forces may be negligible, but *inasmuch as they might not be*, a lighter
engine doesn't help, it hurts.

Still, your comment about elasticity is irrelevant.

Gross weight is what we accelerate, not components.

The components are connected by structure designed for specific forces.

For example, I can add a one ounce weight to the back of my airplane with
some scotch tape, and it won't fall off, no matter how fast I accelerate.
But if I tried to pull the entire airplane by pulling on that one ounce
weight, the tape will fail, even at extremely low acceleration.

Pete

This news article
(http://www.breitbart.com/news/2005/12/20/D8EKBRTG0.html) says that the
wing was recovered from the water today, and the engine and prop are
still attached. There's even a photo showing it. Looks like the wing
separated pretty well inboard of the engine. At this point,
speculation seems that either a fuel leak/fire melting the spar... or
perhaps just simple plain structural failure of the spar with the fire
happening afterwards could both possibly explain the wing separation.


Jim Macklin wrote:
More likely that a fuel line was not properly safetied or
otherwise failed. Turbine engines have fuel pressures as
high a 1,000 PSI, so the fuel system in the engine is highly
stressed. The fuel supply pumps are high capacity and 50 to
100 PSI, so again, the fuel connections and lines are
stressed.

If there was a fuel leak into the nacelle, wing root area,
any source of ignition could cause an explosion and the
resulting fire would soften the aluminum spar quickly. The
emergency procedure for a fire is to shut off the fuel
valves, but if the failure was between the tank and fuel
tank or the valve was damaged, it might not be possible to
shut the fuel off.

The NTSB is very good at investigating this type of failure,
the will track melted and bent metal, see the pattern of
soot and follow the fractures in the metal.

The Chalk Island web site says that their airplanes were in
the shop for the engine changes and complete mechanical
refurbishment and new paint/interiors.

There should be some preliminary data released by the NTSB
before Christmas or New Year, I would expect.


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

--
Merry Christmas
Have a Safe and Happy New Year
Live Long and Prosper
Jim Macklin
wrote in message
ps.com...
| This news article
| (http://www.breitbart.com/news/2005/12/20/D8EKBRTG0.html)
says that the
| wing was recovered from the water today, and the engine
and prop are
| still attached. There's even a photo showing it. Looks
like the wing
| separated pretty well inboard of the engine. At this
point,
| speculation seems that either a fuel leak/fire melting the
spar... or
| perhaps just simple plain structural failure of the spar
with the fire
| happening afterwards could both possibly explain the wing
separation.
|
|
| Jim Macklin wrote:
| More likely that a fuel line was not properly safetied
or
| otherwise failed. Turbine engines have fuel pressures
as
| high a 1,000 PSI, so the fuel system in the engine is
highly
| stressed. The fuel supply pumps are high capacity and
50 to
| 100 PSI, so again, the fuel connections and lines are
| stressed.
|
| If there was a fuel leak into the nacelle, wing root
area,
| any source of ignition could cause an explosion and the
| resulting fire would soften the aluminum spar quickly.
The
| emergency procedure for a fire is to shut off the fuel
| valves, but if the failure was between the tank and fuel
| tank or the valve was damaged, it might not be possible
to
| shut the fuel off.
|
| The NTSB is very good at investigating this type of
failure,
| the will track melted and bent metal, see the pattern of
| soot and follow the fractures in the metal.
|
|

wrote:
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.

Not that they aren't subject to resonance issues. Remember the Electra?

Reports I saws this morning said that the NTSB said they
found a fatigue crack in the main spar, maybe the conversion
was not done well or the maintenance was not though enough.
I'll bet the fleet is grounded and they require immediate,
"before further flight" NDT inspections of the wings, etc.


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

--
Merry Christmas
Have a Safe and Happy New Year
Live Long and Prosper
Jim Macklin


"Ron Natalie" wrote in message
m...
| wrote:
| 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.
|
| Not that they aren't subject to resonance issues.
Remember the Electra?

Jim Macklin wrote:
Reports I saws this morning said that the NTSB said they
found a fatigue crack in the main spar, maybe the conversion
was not done well or the maintenance was not though enough.
I'll bet the fleet is grounded and they require immediate,
"before further flight" NDT inspections of the wings, etc.

Chalk's has voluntarily grounded thier Mallards and is performing an exhaustive
test of the spars on one of them now. The NTSB rep voiced the opinion that age
alone would not be sufficient to cause this failure; some additional stress
would be required.

George Patterson
Coffee is only a way of stealing time that should by rights belong to
your slightly older self.

That is probably true. The odds are that inspections will
not find any other similar cracks in the rest of the Chalk
fleet, I imagine that every Mallard, worldwide, will be
inspected soon. It is even possible that the crack that was
found was recent, metallurgical tests will have to be done
to know for sure. It is even possible that it was caused by
some defect dating back 50 years and was not visible on the
surface.

I'm sure that it will be fixed, too bad, a wing coming off
has only one recovery mode, parachute a la Cirrus.


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

"George Patterson" wrote in message
news:ixoqf.29956$CL.291@trnddc04...
| Jim Macklin wrote:
| Reports I saws this morning said that the NTSB said they
| found a fatigue crack in the main spar, maybe the
conversion
| was not done well or the maintenance was not though
enough.
| I'll bet the fleet is grounded and they require
immediate,
| "before further flight" NDT inspections of the wings,
etc.
|
| Chalk's has voluntarily grounded thier Mallards and is
performing an exhaustive
| test of the spars on one of them now. The NTSB rep voiced
the opinion that age
| alone would not be sufficient to cause this failure; some
additional stress
| would be required.
|
| George Patterson
| Coffee is only a way of stealing time that should by
rights belong to
| your slightly older self.

George Patterson wrote:

Jim Macklin wrote:

Reports I saws this morning said that the NTSB said they found a
fatigue crack in the main spar, maybe the conversion was not done well
or the maintenance was not though enough. I'll bet the fleet is
grounded and they require immediate, "before further flight" NDT
inspections of the wings, etc.


Chalk's has voluntarily grounded thier Mallards and is performing an
exhaustive test of the spars on one of them now. The NTSB rep voiced the
opinion that age alone would not be sufficient to cause this failure;
some additional stress would be required.

A pretty irresponsible statement for an NTSB person. Fatigue can cause
a stressed member to fail at a very low load, much less than even flight
loads. I seem to remember a picture of a Buff whose wing had failed on
the ground. It has been years and I don't remember the details, but it
seems like it was due to something fairly innocous such as refueling. I
believe fatigue was determined to be the root cause.


Matt