Seaplane down off Miami Beach....

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

This thing's just a heart breaker. I see them flying all the
time when I'm in Miami. They've been flying off Watson Island
forever. I've always thought it would be fun to fly with them
over to the Bahamas.


Jim Macklin 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.. The airplane seems to have
been very sturdy, since the fuselage is intact after the
impact.

Thanks.

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.


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

--
Merry Christmas
Have a Safe and Happy New Year
Live Long and Prosper
Jim Macklin
"Otis Winslow" wrote in message
...
| I'm wondering if fitting turbine engines on the old
airframes
| didn't pull something loose in the wing/mount.
|
| This thing's just a heart breaker. I see them flying all
the
| time when I'm in Miami. They've been flying off Watson
Island
| forever. I've always thought it would be fun to fly with
them
| over to the Bahamas.
|
|
| Jim Macklin 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.. The airplane seems to
have
| been very sturdy, since the fuselage is intact after the
| impact.
|
| Thanks.
|
|

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.
|
|

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'd agree with the other posters that it sounds more like a
leaking/broken fuel fitting that went bad, ignited and led to
structural failure.

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

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

"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