Turbo prop question

[Chris W]

I was channel surfing the other day and caught the tail end of some show
about rich people and their planes. Anyway the pilot of this one single
engine turbo prop said there was no mechanical connection between the
prop and engine. How can that be?


I didn't catch the name of the plane. but as I remember, there were 4
seats in the passenger area, and it was pretty roomy. The only other
distinctive thing I can remember is it had a fairly large cargo door
with a power assist to close it because it was so far over head when it
was open.



--
Chris W
KE5GIX

"Protect your digital freedom and privacy, eliminate DRM,
learn more at http://www.defectivebydesign.org/what_is_drm"

Ham Radio Repeater Database.
http://hrrdb.com

[Bertie the Bunyip[_24_]]

Chris W > wrote in news:74gQj.67968$y05.19485
@newsfe22.lga:

> I was channel surfing the other day and caught the tail end of some
show
> about rich people and their planes. Anyway the pilot of this one
single
> engine turbo prop said there was no mechanical connection between the
> prop and engine. How can that be?
>
>
> I didn't catch the name of the plane. but as I remember, there were 4
> seats in the passenger area, and it was pretty roomy. The only other
> distinctive thing I can remember is it had a fairly large cargo door
> with a power assist to close it because it was so far over head when
it
> was open.
>
>
>

It's a free turbine. Most modern turboprops use that system. There's a
seperate turbine that runs the prop geabox. He's technically incorrect
since that turbine is part of the engine...


Bertie

[Frank Olson]

Bertie the Bunyip wrote:
> Chris W > wrote in news:74gQj.67968$y05.19485
> @newsfe22.lga:
>
>> I was channel surfing the other day and caught the tail end of some
> show
>> about rich people and their planes. Anyway the pilot of this one
> single
>> engine turbo prop said there was no mechanical connection between the
>> prop and engine. How can that be?
>>
>>
>> I didn't catch the name of the plane. but as I remember, there were 4
>> seats in the passenger area, and it was pretty roomy. The only other
>> distinctive thing I can remember is it had a fairly large cargo door
>> with a power assist to close it because it was so far over head when
> it
>> was open.
>>
>>
>>
>
> It's a free turbine. Most modern turboprops use that system. There's a
> seperate turbine that runs the prop geabox. He's technically incorrect
> since that turbine is part of the engine...
>
>
> Bertie


Rich people. More money than brains.

[[email protected]]

On 25 Apr, 11:53, Frank Olson
> wrote:
> Bertie the Bunyip wrote:
> > Chris W > wrote in news:74gQj.67968$y05.19485
> > @newsfe22.lga:
>
> >> I was channel surfing the other day and caught the tail end of some
> > show
> >> about rich people and their planes. *Anyway the pilot of this one
> > single
> >> engine turbo prop said there was no mechanical connection between the
> >> prop and engine. *How can that be?
>
> > It's a free turbine. Most modern turboprops use that system. There's a
> > seperate turbine that runs the prop geabox. He's technically incorrect
> > since that turbine is part of the engine...
>
> > Bertie
>
> Rich people. *More money than brains.- Hide quoted text -
>

I'm not in disagreement with Bertie, wouldn't dare, but it
"could be" electric drive, hydraulic drive.

These are used in other vehicles. Most cars in the US
use an automatic transmission that includes a
torque convertor for example.

I am sure that it is in this case a free turbine - gas drive -
that connects to a propellor - gas-gas drive.

http://www.gasgas.com/index.shtml


http://www.britannica.com/eb/topic-182776/electric-transmission
http://en.wikipedia.org/wiki/Diesel-electric

http://www.fpweb.com/200/FPE/Hydraulics/Article/True/6450/Hydraulics

[Bertie the Bunyip[_24_]]

Frank Olson > wrote in
news:0ShQj.90501$rd2.26964@pd7urf3no:

> Bertie the Bunyip wrote:
>> Chris W > wrote in news:74gQj.67968$y05.19485
>> @newsfe22.lga:
>>
>>> I was channel surfing the other day and caught the tail end of some
>> show
>>> about rich people and their planes. Anyway the pilot of this one
>> single
>>> engine turbo prop said there was no mechanical connection between
the
>>> prop and engine. How can that be?
>>>
>>>
>>> I didn't catch the name of the plane. but as I remember, there were
4
>>> seats in the passenger area, and it was pretty roomy. The only
other
>>> distinctive thing I can remember is it had a fairly large cargo door
>>> with a power assist to close it because it was so far over head
when
>> it
>>> was open.
>>>
>>>
>>>
>>
>> It's a free turbine. Most modern turboprops use that system. There's
a
>> seperate turbine that runs the prop geabox. He's technically
incorrect
>> since that turbine is part of the engine...
>>
>>
>> Bertie
>
>
> Rich people. More money than brains.
>

Well, what he maenas is the prop isn;t connected to the main drive of
the engine. You can actually stop the prop on a free turbine while the
engine is running and it will run just fine. He's not wrong but he's not
right if you know what I mean.

Bertie

[Bertie the Bunyip[_24_]]

wrote in news:de5298d4-778b-475f-9321-
:

> On 25 Apr, 11:53, Frank Olson
> > wrote:
>> Bertie the Bunyip wrote:
>> > Chris W > wrote in news:74gQj.67968$y05.19485
>> > @newsfe22.lga:
>>
>> >> I was channel surfing the other day and caught the tail end of
some
>> > show
>> >> about rich people and their planes. *Anyway the pilot of this one
>> > single
>> >> engine turbo prop said there was no mechanical connection between
the
>> >> prop and engine. *How can that be?
>>
>> > It's a free turbine. Most modern turboprops use that system.
There's a
>> > seperate turbine that runs the prop geabox. He's technically
incorrect
>> > since that turbine is part of the engine...
>>
>> > Bertie
>>
>> Rich people. *More money than brains.- Hide quoted text -
>>
>
> I'm not in disagreement with Bertie, wouldn't dare, but it
> "could be" electric drive, hydraulic drive.
>


Nah, not on a turbine.

> These are used in other vehicles. Most cars in the US
> use an automatic transmission that includes a
> torque convertor for example.
>
> I am sure that it is in this case a free turbine - gas drive -
> that connects to a propellor - gas-gas drive.
>
> http://www.gasgas.com/index.shtml
>
>

Yeah, almost all modern turboprops use this system. Some of the older
ones, like the RR Dart or the Allisons were gear driven off the main
turbine, but this is all but abandoned these days. In fact, even "jets"
are really just ducted fan turboprops with the fan driven by a turbine
in the exhaust.


Bertie

[Maxwell[_2_]]

"Bertie the Bunyip" > wrote in message
.. .
> Frank Olson > wrote in
> news:0ShQj.90501$rd2.26964@pd7urf3no:
>
>> Bertie the Bunyip wrote:
>>> Chris W > wrote in news:74gQj.67968$y05.19485
>>> @newsfe22.lga:
>>>
>>>> I was channel surfing the other day and caught the tail end of some
>>> show
>>>> about rich people and their planes. Anyway the pilot of this one
>>> single
>>>> engine turbo prop said there was no mechanical connection between
> the
>>>> prop and engine. How can that be?
>>>>
>>>>
>>>> I didn't catch the name of the plane. but as I remember, there were
> 4
>>>> seats in the passenger area, and it was pretty roomy. The only
> other
>>>> distinctive thing I can remember is it had a fairly large cargo door
>>>> with a power assist to close it because it was so far over head
> when
>>> it
>>>> was open.
>>>>
>>>>
>>>>
>>>
>>> It's a free turbine. Most modern turboprops use that system. There's
> a
>>> seperate turbine that runs the prop geabox. He's technically
> incorrect
>>> since that turbine is part of the engine...
>>>
>>>
>>> Bertie
>>
>>
>> Rich people. More money than brains.
>>
>
> Well, what he maenas is the prop isn;t connected to the main drive of
> the engine. You can actually stop the prop on a free turbine while the
> engine is running and it will run just fine. He's not wrong but he's not
> right if you know what I mean.
>
> Bertie

Wannnboi, you don't know what you maena.

[Bertie the Bunyip[_24_]]

"Maxwell" <luv2^fly99@cox.^net> wrote in news:%5kQj.67977$y05.64004
@newsfe22.lga:

>
> "Bertie the Bunyip" > wrote in message
> .. .
>> Frank Olson > wrote in
>> news:0ShQj.90501$rd2.26964@pd7urf3no:
>>
>>> Bertie the Bunyip wrote:
>>>> Chris W > wrote in news:74gQj.67968$y05.19485
>>>> @newsfe22.lga:
>>>>
>>>>> I was channel surfing the other day and caught the tail end of
some
>>>> show
>>>>> about rich people and their planes. Anyway the pilot of this one
>>>> single
>>>>> engine turbo prop said there was no mechanical connection between
>> the
>>>>> prop and engine. How can that be?
>>>>>
>>>>>
>>>>> I didn't catch the name of the plane. but as I remember, there
were
>> 4
>>>>> seats in the passenger area, and it was pretty roomy. The only
>> other
>>>>> distinctive thing I can remember is it had a fairly large cargo
door
>>>>> with a power assist to close it because it was so far over head
>> when
>>>> it
>>>>> was open.
>>>>>
>>>>>
>>>>>
>>>>
>>>> It's a free turbine. Most modern turboprops use that system.
There's
>> a
>>>> seperate turbine that runs the prop geabox. He's technically
>> incorrect
>>>> since that turbine is part of the engine...
>>>>
>>>>
>>>> Bertie
>>>
>>>
>>> Rich people. More money than brains.
>>>
>>
>> Well, what he maenas is the prop isn;t connected to the main drive of
>> the engine. You can actually stop the prop on a free turbine while
the
>> engine is running and it will run just fine. He's not wrong but he's
not
>> right if you know what I mean.
>>
>> Bertie
>
> Wannnboi, you don't know what you maena.
>
>
>
snort!


Bertie

[Robert M. Gary]

On Apr 25, 3:26*am, Bertie the Bunyip > wrote:
> Frank Olson > wrote innews:0ShQj.90501$rd2.26964@pd7urf3no:

> He's not wrong but he's not
> right if you know what I mean.

Yes, we all lived through the Clinton years, we know that it depends
on the definition of "it" and not wrong but not right, etc.

-Robert

[Bertie the Bunyip[_24_]]

"Robert M. Gary" > wrote in
:

> On Apr 25, 3:26*am, Bertie the Bunyip > wrote:
>> Frank Olson > wrote
>> innews:0ShQ
> j.90501$rd2.26964@pd7urf3no:
>
>> He's not wrong but he's not
>> right if you know what I mean.
>
> Yes, we all lived through the Clinton years, we know that it depends
> on the definition of "it" and not wrong but not right, etc.


Em, ok, not quite the same thing...


You would think that if you could grasp that subtlety, though, you'd
have sussed out the more recent string of lies...


Bertie


Bertie

[[email protected]]

On Apr 25, 4:37 am, Bertie the Bunyip > wrote:
> wrote in news:de5298d4-778b-475f-9321-
> :
>
>
>
>
>
> > On 25 Apr, 11:53, Frank Olson
> > > wrote:
> >> Bertie the Bunyip wrote:
> >> > Chris W > wrote in news:74gQj.67968$y05.19485
> >> > @newsfe22.lga:
>
> >> >> I was channel surfing the other day and caught the tail end of
> some
> >> > show
> >> >> about rich people and their planes. Anyway the pilot of this one
> >> > single
> >> >> engine turbo prop said there was no mechanical connection between
> the
> >> >> prop and engine. How can that be?
>
> >> > It's a free turbine. Most modern turboprops use that system.
> There's a
> >> > seperate turbine that runs the prop geabox. He's technically
> incorrect
> >> > since that turbine is part of the engine...
>
> >> > Bertie
>
> >> Rich people. More money than brains.- Hide quoted text -
>
> > I'm not in disagreement with Bertie, wouldn't dare, but it
> > "could be" electric drive, hydraulic drive.
>
> Nah, not on a turbine.
>
> > These are used in other vehicles. Most cars in the US
> > use an automatic transmission that includes a
> > torque convertor for example.
>
> > I am sure that it is in this case a free turbine - gas drive -
> > that connects to a propellor - gas-gas drive.
>
> >http://www.gasgas.com/index.shtml
>
> Yeah, almost all modern turboprops use this system. Some of the older
> ones, like the RR Dart or the Allisons were gear driven off the main
> turbine, but this is all but abandoned these days. In fact, even "jets"
> are really just ducted fan turboprops with the fan driven by a turbine
> in the exhaust.
>
> Bertie

The Garrett TPE 331 is still a fixed turboprop. Lots of those
flying, especially on some upscale kitplanes. Isn't the Swearingen
Merlin powered by those, too?
http://www.aircraftenginedesign.com/pictures/TPE331.gif

Dan

[Matt W. Barrow]

"Frank Olson" > wrote in message
news:0ShQj.90501$rd2.26964@pd7urf3no...
> Bertie the Bunyip wrote:
>> Chris W > wrote in news:74gQj.67968$y05.19485
>> @newsfe22.lga:
>>
>>> I was channel surfing the other day and caught the tail end of some
>> show
>>> about rich people and their planes. Anyway the pilot of this one
>> single
>>> engine turbo prop said there was no mechanical connection between the
>>> prop and engine. How can that be?
>>>
>>>
>>> I didn't catch the name of the plane. but as I remember, there were 4
>>> seats in the passenger area, and it was pretty roomy. The only other
>>> distinctive thing I can remember is it had a fairly large cargo door
>>> with a power assist to close it because it was so far over head when
>> it
>>> was open.
>>>
>>>
>>>
>>
>> It's a free turbine. Most modern turboprops use that system. There's a
>> seperate turbine that runs the prop geabox. He's technically incorrect
>> since that turbine is part of the engine... Bertie
>
>
> Rich people. More money than brains.

Envious people - generally stupid.

[Bertie the Bunyip[_24_]]

wrote in news:e508d435-db20-4b21-9c9b-
:

> On Apr 25, 4:37 am, Bertie the Bunyip > wrote:
>> wrote in news:de5298d4-778b-475f-9321-
>> :
>>
>>
>>
>>
>>
>> > On 25 Apr, 11:53, Frank Olson
>> > > wrote:
>> >> Bertie the Bunyip wrote:
>> >> > Chris W > wrote in news:74gQj.67968$y05.19485
>> >> > @newsfe22.lga:
>>
>> >> >> I was channel surfing the other day and caught the tail end of
>> some
>> >> > show
>> >> >> about rich people and their planes. Anyway the pilot of this
one
>> >> > single
>> >> >> engine turbo prop said there was no mechanical connection
between
>> the
>> >> >> prop and engine. How can that be?
>>
>> >> > It's a free turbine. Most modern turboprops use that system.
>> There's a
>> >> > seperate turbine that runs the prop geabox. He's technically
>> incorrect
>> >> > since that turbine is part of the engine...
>>
>> >> > Bertie
>>
>> >> Rich people. More money than brains.- Hide quoted text -
>>
>> > I'm not in disagreement with Bertie, wouldn't dare, but it
>> > "could be" electric drive, hydraulic drive.
>>
>> Nah, not on a turbine.
>>
>> > These are used in other vehicles. Most cars in the US
>> > use an automatic transmission that includes a
>> > torque convertor for example.
>>
>> > I am sure that it is in this case a free turbine - gas drive -
>> > that connects to a propellor - gas-gas drive.
>>
>> >http://www.gasgas.com/index.shtml
>>
>> Yeah, almost all modern turboprops use this system. Some of the older
>> ones, like the RR Dart or the Allisons were gear driven off the main
>> turbine, but this is all but abandoned these days. In fact, even
"jets"
>> are really just ducted fan turboprops with the fan driven by a
turbine
>> in the exhaust.
>>
>> Bertie
>
> The Garrett TPE 331 is still a fixed turboprop. Lots of those
> flying, especially on some upscale kitplanes. Isn't the Swearingen
> Merlin powered by those, too?
> http://www.aircraftenginedesign.com/pictures/TPE331.gif
>
> Dan
>

Yeah, Garret are one of the holdouts. They're on alot of airplanes. the
Metro, the turbine commanders. I think there's a Walter that's in th
esame class being used on quite a few airplanes as well. The Pratts are
all free turbines, AFAIK. The older ones are centrifugal engines with a
revese flow, that is, the intake is on the back and they exhaust in
front, which is why the PT6 's have those stovepipes just behind the
prop, and the newer 120 and newers are axial with the air coming in the
front and the fire going out the back. The 120 has a prop brake with
which you can stop the prop while the engine is running ( on the ground)
and use the engine for an APU.


Bertie

[Frank Olson]

Matt W. Barrow wrote:
> "Frank Olson" > wrote in message
> news:0ShQj.90501$rd2.26964@pd7urf3no...
>> Bertie the Bunyip wrote:
>>> Chris W > wrote in news:74gQj.67968$y05.19485
>>> @newsfe22.lga:
>>>
>>>> I was channel surfing the other day and caught the tail end of some
>>> show
>>>> about rich people and their planes. Anyway the pilot of this one
>>> single
>>>> engine turbo prop said there was no mechanical connection between the
>>>> prop and engine. How can that be?
>>>>
>>>>
>>>> I didn't catch the name of the plane. but as I remember, there were 4
>>>> seats in the passenger area, and it was pretty roomy. The only other
>>>> distinctive thing I can remember is it had a fairly large cargo door
>>>> with a power assist to close it because it was so far over head when
>>> it
>>>> was open.
>>>>
>>>>
>>>>
>>> It's a free turbine. Most modern turboprops use that system. There's a
>>> seperate turbine that runs the prop geabox. He's technically incorrect
>>> since that turbine is part of the engine... Bertie
>>
>> Rich people. More money than brains.
>
> Envious people - generally stupid.
>
>


Touché! :-)

[muff528]

"Bertie the Bunyip" > wrote in message
.. .
> wrote in news:e508d435-db20-4b21-9c9b-
> :
>
>> On Apr 25, 4:37 am, Bertie the Bunyip > wrote:
>>> wrote in news:de5298d4-778b-475f-9321-
>>> :
>>>
>>>
>>>
>>>
>>>
>>> > On 25 Apr, 11:53, Frank Olson
>>> > > wrote:
>>> >> Bertie the Bunyip wrote:
>>> >> > Chris W > wrote in news:74gQj.67968$y05.19485
>>> >> > @newsfe22.lga:
>>>
>>> >> >> I was channel surfing the other day and caught the tail end of
>>> some
>>> >> > show
>>> >> >> about rich people and their planes. Anyway the pilot of this
> one
>>> >> > single
>>> >> >> engine turbo prop said there was no mechanical connection
> between
>>> the
>>> >> >> prop and engine. How can that be?
>>>
>>> >> > It's a free turbine. Most modern turboprops use that system.
>>> There's a
>>> >> > seperate turbine that runs the prop geabox. He's technically
>>> incorrect
>>> >> > since that turbine is part of the engine...
>>>
>>> >> > Bertie
>>>
>>> >> Rich people. More money than brains.- Hide quoted text -
>>>
>>> > I'm not in disagreement with Bertie, wouldn't dare, but it
>>> > "could be" electric drive, hydraulic drive.
>>>
>>> Nah, not on a turbine.
>>>
>>> > These are used in other vehicles. Most cars in the US
>>> > use an automatic transmission that includes a
>>> > torque convertor for example.
>>>
>>> > I am sure that it is in this case a free turbine - gas drive -
>>> > that connects to a propellor - gas-gas drive.
>>>
>>> >http://www.gasgas.com/index.shtml
>>>
>>> Yeah, almost all modern turboprops use this system. Some of the older
>>> ones, like the RR Dart or the Allisons were gear driven off the main
>>> turbine, but this is all but abandoned these days. In fact, even
> "jets"
>>> are really just ducted fan turboprops with the fan driven by a
> turbine
>>> in the exhaust.
>>>
>>> Bertie
>>
>> The Garrett TPE 331 is still a fixed turboprop. Lots of those
>> flying, especially on some upscale kitplanes. Isn't the Swearingen
>> Merlin powered by those, too?
>> http://www.aircraftenginedesign.com/pictures/TPE331.gif
>>
>> Dan
>>
>
> Yeah, Garret are one of the holdouts. They're on alot of airplanes. the
> Metro, the turbine commanders. I think there's a Walter that's in th
> esame class being used on quite a few airplanes as well. The Pratts are
> all free turbines, AFAIK. The older ones are centrifugal engines with a
> revese flow, that is, the intake is on the back and they exhaust in
> front, which is why the PT6 's have those stovepipes just behind the
> prop, and the newer 120 and newers are axial with the air coming in the
> front and the fire going out the back. The 120 has a prop brake with
> which you can stop the prop while the engine is running ( on the ground)
> and use the engine for an APU.
>
>
> Bertie

Amazing how after a while you can tell the difference between the Pratts and
the Garretts from the ground while the plane is at 13,500 ft above you. Many
times we had a Twin Otter with Pratts and a Casa 212 with Garretts flying on
the same day and you could tell which was on jump run just by the sound. I
just assumed it was because of the different methods of coupling the props
to the powerplant.

TonyP.

[Bertie the Bunyip[_24_]]

"muff528" > wrote in
news:krtRj.968$lc6.775@trnddc04:

>
> "Bertie the Bunyip" > wrote in message
> .. .
>> wrote in news:e508d435-db20-4b21-9c9b-
>> :
>>
>>> On Apr 25, 4:37 am, Bertie the Bunyip > wrote:
>>>> wrote in news:de5298d4-778b-475f-9321-
>>>> :
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> > On 25 Apr, 11:53, Frank Olson
>>>> > > wrote:
>>>> >> Bertie the Bunyip wrote:
>>>> >> > Chris W > wrote in news:74gQj.67968$y05.19485
>>>> >> > @newsfe22.lga:
>>>>
>>>> >> >> I was channel surfing the other day and caught the tail end
>>>> >> >> of
>>>> some
>>>> >> > show
>>>> >> >> about rich people and their planes. Anyway the pilot of this
>> one
>>>> >> > single
>>>> >> >> engine turbo prop said there was no mechanical connection
>> between
>>>> the
>>>> >> >> prop and engine. How can that be?
>>>>
>>>> >> > It's a free turbine. Most modern turboprops use that system.
>>>> There's a
>>>> >> > seperate turbine that runs the prop geabox. He's technically
>>>> incorrect
>>>> >> > since that turbine is part of the engine...
>>>>
>>>> >> > Bertie
>>>>
>>>> >> Rich people. More money than brains.- Hide quoted text -
>>>>
>>>> > I'm not in disagreement with Bertie, wouldn't dare, but it
>>>> > "could be" electric drive, hydraulic drive.
>>>>
>>>> Nah, not on a turbine.
>>>>
>>>> > These are used in other vehicles. Most cars in the US
>>>> > use an automatic transmission that includes a
>>>> > torque convertor for example.
>>>>
>>>> > I am sure that it is in this case a free turbine - gas drive -
>>>> > that connects to a propellor - gas-gas drive.
>>>>
>>>> >http://www.gasgas.com/index.shtml
>>>>
>>>> Yeah, almost all modern turboprops use this system. Some of the
>>>> older ones, like the RR Dart or the Allisons were gear driven off
>>>> the main turbine, but this is all but abandoned these days. In
>>>> fact, even
>> "jets"
>>>> are really just ducted fan turboprops with the fan driven by a
>> turbine
>>>> in the exhaust.
>>>>
>>>> Bertie
>>>
>>> The Garrett TPE 331 is still a fixed turboprop. Lots of
>>> those
>>> flying, especially on some upscale kitplanes. Isn't the Swearingen
>>> Merlin powered by those, too?
>>> http://www.aircraftenginedesign.com/pictures/TPE331.gif
>>>
>>> Dan
>>>
>>
>> Yeah, Garret are one of the holdouts. They're on alot of airplanes.
>> the Metro, the turbine commanders. I think there's a Walter that's in
>> th esame class being used on quite a few airplanes as well. The
>> Pratts are all free turbines, AFAIK. The older ones are centrifugal
>> engines with a revese flow, that is, the intake is on the back and
>> they exhaust in front, which is why the PT6 's have those stovepipes
>> just behind the prop, and the newer 120 and newers are axial with the
>> air coming in the front and the fire going out the back. The 120 has
>> a prop brake with which you can stop the prop while the engine is
>> running ( on the ground) and use the engine for an APU.
>>
>>
>> Bertie
>
> Amazing how after a while you can tell the difference between the
> Pratts and the Garretts from the ground while the plane is at 13,500
> ft above you. Many times we had a Twin Otter with Pratts and a Casa
> 212 with Garretts flying on the same day and you could tell which was
> on jump run just by the sound. I just assumed it was because of the
> different methods of coupling the props to the powerplant.

!!! I don't think I could except by seeing the airplane. Yeah, you get
tuned in to any engine you're familiar with, though, don't you?


Bertie

[muff528]

"Bertie the Bunyip" > wrote in message
...
> "muff528" > wrote in
> news:krtRj.968$lc6.775@trnddc04:
>
>>
>> "Bertie the Bunyip" > wrote in message
>> .. .
>>> wrote in news:e508d435-db20-4b21-9c9b-
>>> :
>>>
>>>> On Apr 25, 4:37 am, Bertie the Bunyip > wrote:
>>>>> wrote in news:de5298d4-778b-475f-9321-
>>>>> :
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> > On 25 Apr, 11:53, Frank Olson
>>>>> > > wrote:
>>>>> >> Bertie the Bunyip wrote:
>>>>> >> > Chris W > wrote in news:74gQj.67968$y05.19485
>>>>> >> > @newsfe22.lga:
>>>>>
>>>>> >> >> I was channel surfing the other day and caught the tail end
>>>>> >> >> of
>>>>> some
>>>>> >> > show
>>>>> >> >> about rich people and their planes. Anyway the pilot of this
>>> one
>>>>> >> > single
>>>>> >> >> engine turbo prop said there was no mechanical connection
>>> between
>>>>> the
>>>>> >> >> prop and engine. How can that be?
>>>>>
>>>>> >> > It's a free turbine. Most modern turboprops use that system.
>>>>> There's a
>>>>> >> > seperate turbine that runs the prop geabox. He's technically
>>>>> incorrect
>>>>> >> > since that turbine is part of the engine...
>>>>>
>>>>> >> > Bertie
>>>>>
>>>>> >> Rich people. More money than brains.- Hide quoted text -
>>>>>
>>>>> > I'm not in disagreement with Bertie, wouldn't dare, but it
>>>>> > "could be" electric drive, hydraulic drive.
>>>>>
>>>>> Nah, not on a turbine.
>>>>>
>>>>> > These are used in other vehicles. Most cars in the US
>>>>> > use an automatic transmission that includes a
>>>>> > torque convertor for example.
>>>>>
>>>>> > I am sure that it is in this case a free turbine - gas drive -
>>>>> > that connects to a propellor - gas-gas drive.
>>>>>
>>>>> >http://www.gasgas.com/index.shtml
>>>>>
>>>>> Yeah, almost all modern turboprops use this system. Some of the
>>>>> older ones, like the RR Dart or the Allisons were gear driven off
>>>>> the main turbine, but this is all but abandoned these days. In
>>>>> fact, even
>>> "jets"
>>>>> are really just ducted fan turboprops with the fan driven by a
>>> turbine
>>>>> in the exhaust.
>>>>>
>>>>> Bertie
>>>>
>>>> The Garrett TPE 331 is still a fixed turboprop. Lots of
>>>> those
>>>> flying, especially on some upscale kitplanes. Isn't the Swearingen
>>>> Merlin powered by those, too?
>>>> http://www.aircraftenginedesign.com/pictures/TPE331.gif
>>>>
>>>> Dan
>>>>
>>>
>>> Yeah, Garret are one of the holdouts. They're on alot of airplanes.
>>> the Metro, the turbine commanders. I think there's a Walter that's in
>>> th esame class being used on quite a few airplanes as well. The
>>> Pratts are all free turbines, AFAIK. The older ones are centrifugal
>>> engines with a revese flow, that is, the intake is on the back and
>>> they exhaust in front, which is why the PT6 's have those stovepipes
>>> just behind the prop, and the newer 120 and newers are axial with the
>>> air coming in the front and the fire going out the back. The 120 has
>>> a prop brake with which you can stop the prop while the engine is
>>> running ( on the ground) and use the engine for an APU.
>>>
>>>
>>> Bertie
>>
>> Amazing how after a while you can tell the difference between the
>> Pratts and the Garretts from the ground while the plane is at 13,500
>> ft above you. Many times we had a Twin Otter with Pratts and a Casa
>> 212 with Garretts flying on the same day and you could tell which was
>> on jump run just by the sound. I just assumed it was because of the
>> different methods of coupling the props to the powerplant.
>
> !!! I don't think I could except by seeing the airplane. Yeah, you get
> tuned in to any engine you're familiar with, though, don't you?
>
>
> Bertie
>

Yeah, I think the fact that they were flying within a few minutes of each
other all day makes the comparison easier. The main difference seems to me
to be the "loudness" of the beat freq. generated by slightly "out-of-sync"
props, especially when the "cut" occurs just before exit time. The Garretts
sounded "gutsier" for lack of a better term and the beat frequency amplitude
was much greater than the PT6's. Even during the climbout to jump altitude
the Garretts seemed to sound more authoritative. But that brings up another
question that I have wondered about. For a twin, for example, does the force
of the atmosphere pushing against the props have an "equalizing" effect on
the propeller speeds of turbine-coupled props on slightly out-of-sync
engines? I would intuitively think that such a moderating effect would
account for differences in beat sounds between them and direct-coupled twins
which were a few rpm's out.

TP

[[email protected]]

On Apr 28, 7:24 pm, "muff528" > wrote:
> "Bertie the Bunyip" > wrote in .130...
>
>
>
> > "muff528" > wrote in
> >news:krtRj.968$lc6.775@trnddc04:
>
> >> "Bertie the Bunyip" > wrote in message
> .. .
> >>> wrote in news:e508d435-db20-4b21-9c9b-
> >>> :
>
> >>>> On Apr 25, 4:37 am, Bertie the Bunyip > wrote:
> >>>>> wrote in news:de5298d4-778b-475f-9321-
> >>>>> :
>
> >>>>> > On 25 Apr, 11:53, Frank Olson
> >>>>> > > wrote:
> >>>>> >> Bertie the Bunyip wrote:
> >>>>> >> > Chris W > wrote in news:74gQj.67968$y05.19485
> >>>>> >> > @newsfe22.lga:
>
> >>>>> >> >> I was channel surfing the other day and caught the tail end
> >>>>> >> >> of
> >>>>> some
> >>>>> >> > show
> >>>>> >> >> about rich people and their planes. Anyway the pilot of this
> >>> one
> >>>>> >> > single
> >>>>> >> >> engine turbo prop said there was no mechanical connection
> >>> between
> >>>>> the
> >>>>> >> >> prop and engine. How can that be?
>
> >>>>> >> > It's a free turbine. Most modern turboprops use that system.
> >>>>> There's a
> >>>>> >> > seperate turbine that runs the prop geabox. He's technically
> >>>>> incorrect
> >>>>> >> > since that turbine is part of the engine...
>
> >>>>> >> > Bertie
>
> >>>>> >> Rich people. More money than brains.- Hide quoted text -
>
> >>>>> > I'm not in disagreement with Bertie, wouldn't dare, but it
> >>>>> > "could be" electric drive, hydraulic drive.
>
> >>>>> Nah, not on a turbine.
>
> >>>>> > These are used in other vehicles. Most cars in the US
> >>>>> > use an automatic transmission that includes a
> >>>>> > torque convertor for example.
>
> >>>>> > I am sure that it is in this case a free turbine - gas drive -
> >>>>> > that connects to a propellor - gas-gas drive.
>
> >>>>> >http://www.gasgas.com/index.shtml
>
> >>>>> Yeah, almost all modern turboprops use this system. Some of the
> >>>>> older ones, like the RR Dart or the Allisons were gear driven off
> >>>>> the main turbine, but this is all but abandoned these days. In
> >>>>> fact, even
> >>> "jets"
> >>>>> are really just ducted fan turboprops with the fan driven by a
> >>> turbine
> >>>>> in the exhaust.
>
> >>>>> Bertie
>
> >>>> The Garrett TPE 331 is still a fixed turboprop. Lots of
> >>>> those
> >>>> flying, especially on some upscale kitplanes. Isn't the Swearingen
> >>>> Merlin powered by those, too?
> >>>>http://www.aircraftenginedesign.com/pictures/TPE331.gif
>
> >>>> Dan
>
> >>> Yeah, Garret are one of the holdouts. They're on alot of airplanes.
> >>> the Metro, the turbine commanders. I think there's a Walter that's in
> >>> th esame class being used on quite a few airplanes as well. The
> >>> Pratts are all free turbines, AFAIK. The older ones are centrifugal
> >>> engines with a revese flow, that is, the intake is on the back and
> >>> they exhaust in front, which is why the PT6 's have those stovepipes
> >>> just behind the prop, and the newer 120 and newers are axial with the
> >>> air coming in the front and the fire going out the back. The 120 has
> >>> a prop brake with which you can stop the prop while the engine is
> >>> running ( on the ground) and use the engine for an APU.
>
> >>> Bertie
>
> >> Amazing how after a while you can tell the difference between the
> >> Pratts and the Garretts from the ground while the plane is at 13,500
> >> ft above you. Many times we had a Twin Otter with Pratts and a Casa
> >> 212 with Garretts flying on the same day and you could tell which was
> >> on jump run just by the sound. I just assumed it was because of the
> >> different methods of coupling the props to the powerplant.
>
> > !!! I don't think I could except by seeing the airplane. Yeah, you get
> > tuned in to any engine you're familiar with, though, don't you?
>
> > Bertie
>
> Yeah, I think the fact that they were flying within a few minutes of each
> other all day makes the comparison easier. The main difference seems to me
> to be the "loudness" of the beat freq. generated by slightly "out-of-sync"
> props, especially when the "cut" occurs just before exit time. The Garretts
> sounded "gutsier" for lack of a better term and the beat frequency amplitude
> was much greater than the PT6's. Even during the climbout to jump altitude
> the Garretts seemed to sound more authoritative. But that brings up another
> question that I have wondered about. For a twin, for example, does the force
> of the atmosphere pushing against the props have an "equalizing" effect on
> the propeller speeds of turbine-coupled props on slightly out-of-sync
> engines? I would intuitively think that such a moderating effect would
> account for differences in beat sounds between them and direct-coupled twins
> which were a few rpm's out.
>
> TP

Propeller speeds are controlled by the governor, which controls
propeller blade pitch. Adjusting pitch up or down loads or unloads the
prop, which will change its RPM. The governor is controlled by the
propeller RPM control on the panel. Many twins have either a
synchronizer that will adjust one governor a bit to keep the RPM the
same as the other propeller, or a synchrophaser that does the same
thing plus adjusts the rpm the tiniest bit to minimize the cabin
noise. The pilot can adjust the synchrophaser to get the prop blades
passing the fuselage at the same time or alternately or whatever makes
the least noise. The synchro will then hold everything right there.
If an airplane doesn't have either of those and the RPM is
obviously off, the pilot is either ignoring it or doesn't notice. He
can adjust one prop lever to stop it.
An excerpt from Hartzell's material at
http://www.hartzellprop.com/engineering/engineering_constant_speed.htm

"On twin-engine aircraft, whether they are reciprocating or
turbine-powered, the propeller governor or synchronizer may be
supplemented with an electronic synchrophaser. One purpose of the
synchrophaser is to match the two propellers to the same RPM. However,
the more difficult and relevant task of the synchrophaser is to match
not only the RPM, but also the phase position between the two
propellers. In other words, when a blade on one propeller passes the
fuselage, a blade on the other propeller is operating at the same
speed and is at a specific and predefined relative position. In doing
so, airframe vibration and cabin noise can be substantially reduced. "

Dan

[Bertie the Bunyip[_24_]]

"muff528" > wrote in
news:SMuRj.25645$TS5.1624@trnddc08:

>
> "Bertie the Bunyip" > wrote in message
> ...
>> "muff528" > wrote in
>> news:krtRj.968$lc6.775@trnddc04:
>>
>>>
>>> "Bertie the Bunyip" > wrote in message
>>> .. .
>>>> wrote in news:e508d435-db20-4b21-9c9b-
>>>> :
>>>>
>>>>> On Apr 25, 4:37 am, Bertie the Bunyip > wrote:
>>>>>> wrote in news:de5298d4-778b-475f-9321-
>>>>>> :
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> > On 25 Apr, 11:53, Frank Olson
>>>>>> > > wrote:
>>>>>> >> Bertie the Bunyip wrote:
>>>>>> >> > Chris W > wrote in
>>>>>> >> > news:74gQj.67968$y05.19485 @newsfe22.lga:
>>>>>>
>>>>>> >> >> I was channel surfing the other day and caught the tail end
>>>>>> >> >> of
>>>>>> some
>>>>>> >> > show
>>>>>> >> >> about rich people and their planes. Anyway the pilot of
>>>>>> >> >> this
>>>> one
>>>>>> >> > single
>>>>>> >> >> engine turbo prop said there was no mechanical connection
>>>> between
>>>>>> the
>>>>>> >> >> prop and engine. How can that be?
>>>>>>
>>>>>> >> > It's a free turbine. Most modern turboprops use that system.
>>>>>> There's a
>>>>>> >> > seperate turbine that runs the prop geabox. He's technically
>>>>>> incorrect
>>>>>> >> > since that turbine is part of the engine...
>>>>>>
>>>>>> >> > Bertie
>>>>>>
>>>>>> >> Rich people. More money than brains.- Hide quoted text -
>>>>>>
>>>>>> > I'm not in disagreement with Bertie, wouldn't dare, but it
>>>>>> > "could be" electric drive, hydraulic drive.
>>>>>>
>>>>>> Nah, not on a turbine.
>>>>>>
>>>>>> > These are used in other vehicles. Most cars in the US
>>>>>> > use an automatic transmission that includes a
>>>>>> > torque convertor for example.
>>>>>>
>>>>>> > I am sure that it is in this case a free turbine - gas drive -
>>>>>> > that connects to a propellor - gas-gas drive.
>>>>>>
>>>>>> >http://www.gasgas.com/index.shtml
>>>>>>
>>>>>> Yeah, almost all modern turboprops use this system. Some of the
>>>>>> older ones, like the RR Dart or the Allisons were gear driven off
>>>>>> the main turbine, but this is all but abandoned these days. In
>>>>>> fact, even
>>>> "jets"
>>>>>> are really just ducted fan turboprops with the fan driven by a
>>>> turbine
>>>>>> in the exhaust.
>>>>>>
>>>>>> Bertie
>>>>>
>>>>> The Garrett TPE 331 is still a fixed turboprop. Lots of
>>>>> those
>>>>> flying, especially on some upscale kitplanes. Isn't the Swearingen
>>>>> Merlin powered by those, too?
>>>>> http://www.aircraftenginedesign.com/pictures/TPE331.gif
>>>>>
>>>>> Dan
>>>>>
>>>>
>>>> Yeah, Garret are one of the holdouts. They're on alot of airplanes.
>>>> the Metro, the turbine commanders. I think there's a Walter that's
>>>> in th esame class being used on quite a few airplanes as well. The
>>>> Pratts are all free turbines, AFAIK. The older ones are centrifugal
>>>> engines with a revese flow, that is, the intake is on the back and
>>>> they exhaust in front, which is why the PT6 's have those
>>>> stovepipes just behind the prop, and the newer 120 and newers are
>>>> axial with the air coming in the front and the fire going out the
>>>> back. The 120 has a prop brake with which you can stop the prop
>>>> while the engine is running ( on the ground) and use the engine for
>>>> an APU.
>>>>
>>>>
>>>> Bertie
>>>
>>> Amazing how after a while you can tell the difference between the
>>> Pratts and the Garretts from the ground while the plane is at 13,500
>>> ft above you. Many times we had a Twin Otter with Pratts and a Casa
>>> 212 with Garretts flying on the same day and you could tell which
>>> was on jump run just by the sound. I just assumed it was because of
>>> the different methods of coupling the props to the powerplant.
>>
>> !!! I don't think I could except by seeing the airplane. Yeah, you
>> get tuned in to any engine you're familiar with, though, don't you?
>>
>>
>> Bertie
>>
>
> Yeah, I think the fact that they were flying within a few minutes of
> each other all day makes the comparison easier. The main difference
> seems to me to be the "loudness" of the beat freq. generated by
> slightly "out-of-sync" props, especially when the "cut" occurs just
> before exit time. The Garretts sounded "gutsier" for lack of a better
> term and the beat frequency amplitude was much greater than the PT6's.
> Even during the climbout to jump altitude the Garretts seemed to sound
> more authoritative. But that brings up another question that I have
> wondered about. For a twin, for example, does the force of the
> atmosphere pushing against the props have an "equalizing" effect on
> the propeller speeds of turbine-coupled props on slightly out-of-sync
> engines? I would intuitively think that such a moderating effect would
> account for differences in beat sounds between them and direct-coupled
> twins which were a few rpm's out.



Well, I've only flwon one type with the turbine directly geared to the
prop and it was a single lever operation which meant you were altering
the power as well as the prop pitch whne you mover the lever. it had no
autosynch so you did it the old fashioned way and it was out of synch a
good bit of the time. I can't remember hat we had in the King Airs I
flew, but the PW120 had an autosynch so that might account for it.


Bertie

[muff528]

> wrote in message
...
> On Apr 28, 7:24 pm, "muff528" > wrote:
>> "Bertie the Bunyip" > wrote in
>> .130...
>>
>>
>>
>> > "muff528" > wrote in
>> >news:krtRj.968$lc6.775@trnddc04:
>>
>> >> "Bertie the Bunyip" > wrote in message
>> .. .
>> >>> wrote in news:e508d435-db20-4b21-9c9b-
>> >>> :
>>
>> >>>> On Apr 25, 4:37 am, Bertie the Bunyip > wrote:
>> >>>>> wrote in news:de5298d4-778b-475f-9321-
>> >>>>> :
>>
>> >>>>> > On 25 Apr, 11:53, Frank Olson
>> >>>>> > > wrote:
>> >>>>> >> Bertie the Bunyip wrote:
>> >>>>> >> > Chris W > wrote in news:74gQj.67968$y05.19485
>> >>>>> >> > @newsfe22.lga:
>>
>> >>>>> >> >> I was channel surfing the other day and caught the tail end
>> >>>>> >> >> of
>> >>>>> some
>> >>>>> >> > show
>> >>>>> >> >> about rich people and their planes. Anyway the pilot of this
>> >>> one
>> >>>>> >> > single
>> >>>>> >> >> engine turbo prop said there was no mechanical connection
>> >>> between
>> >>>>> the
>> >>>>> >> >> prop and engine. How can that be?
>>
>> >>>>> >> > It's a free turbine. Most modern turboprops use that system.
>> >>>>> There's a
>> >>>>> >> > seperate turbine that runs the prop geabox. He's technically
>> >>>>> incorrect
>> >>>>> >> > since that turbine is part of the engine...
>>
>> >>>>> >> > Bertie
>>
>> >>>>> >> Rich people. More money than brains.- Hide quoted text -
>>
>> >>>>> > I'm not in disagreement with Bertie, wouldn't dare, but it
>> >>>>> > "could be" electric drive, hydraulic drive.
>>
>> >>>>> Nah, not on a turbine.
>>
>> >>>>> > These are used in other vehicles. Most cars in the US
>> >>>>> > use an automatic transmission that includes a
>> >>>>> > torque convertor for example.
>>
>> >>>>> > I am sure that it is in this case a free turbine - gas drive -
>> >>>>> > that connects to a propellor - gas-gas drive.
>>
>> >>>>> >http://www.gasgas.com/index.shtml
>>
>> >>>>> Yeah, almost all modern turboprops use this system. Some of the
>> >>>>> older ones, like the RR Dart or the Allisons were gear driven off
>> >>>>> the main turbine, but this is all but abandoned these days. In
>> >>>>> fact, even
>> >>> "jets"
>> >>>>> are really just ducted fan turboprops with the fan driven by a
>> >>> turbine
>> >>>>> in the exhaust.
>>
>> >>>>> Bertie
>>
>> >>>> The Garrett TPE 331 is still a fixed turboprop. Lots of
>> >>>> those
>> >>>> flying, especially on some upscale kitplanes. Isn't the Swearingen
>> >>>> Merlin powered by those, too?
>> >>>>http://www.aircraftenginedesign.com/pictures/TPE331.gif
>>
>> >>>> Dan
>>
>> >>> Yeah, Garret are one of the holdouts. They're on alot of airplanes.
>> >>> the Metro, the turbine commanders. I think there's a Walter that's in
>> >>> th esame class being used on quite a few airplanes as well. The
>> >>> Pratts are all free turbines, AFAIK. The older ones are centrifugal
>> >>> engines with a revese flow, that is, the intake is on the back and
>> >>> they exhaust in front, which is why the PT6 's have those stovepipes
>> >>> just behind the prop, and the newer 120 and newers are axial with the
>> >>> air coming in the front and the fire going out the back. The 120 has
>> >>> a prop brake with which you can stop the prop while the engine is
>> >>> running ( on the ground) and use the engine for an APU.
>>
>> >>> Bertie
>>
>> >> Amazing how after a while you can tell the difference between the
>> >> Pratts and the Garretts from the ground while the plane is at 13,500
>> >> ft above you. Many times we had a Twin Otter with Pratts and a Casa
>> >> 212 with Garretts flying on the same day and you could tell which was
>> >> on jump run just by the sound. I just assumed it was because of the
>> >> different methods of coupling the props to the powerplant.
>>
>> > !!! I don't think I could except by seeing the airplane. Yeah, you get
>> > tuned in to any engine you're familiar with, though, don't you?
>>
>> > Bertie
>>
>> Yeah, I think the fact that they were flying within a few minutes of each
>> other all day makes the comparison easier. The main difference seems to
>> me
>> to be the "loudness" of the beat freq. generated by slightly
>> "out-of-sync"
>> props, especially when the "cut" occurs just before exit time. The
>> Garretts
>> sounded "gutsier" for lack of a better term and the beat frequency
>> amplitude
>> was much greater than the PT6's. Even during the climbout to jump
>> altitude
>> the Garretts seemed to sound more authoritative. But that brings up
>> another
>> question that I have wondered about. For a twin, for example, does the
>> force
>> of the atmosphere pushing against the props have an "equalizing" effect
>> on
>> the propeller speeds of turbine-coupled props on slightly out-of-sync
>> engines? I would intuitively think that such a moderating effect would
>> account for differences in beat sounds between them and direct-coupled
>> twins
>> which were a few rpm's out.
>>
>> TP
>
> Propeller speeds are controlled by the governor, which controls
> propeller blade pitch. Adjusting pitch up or down loads or unloads the
> prop, which will change its RPM. The governor is controlled by the
> propeller RPM control on the panel. Many twins have either a
> synchronizer that will adjust one governor a bit to keep the RPM the
> same as the other propeller, or a synchrophaser that does the same
> thing plus adjusts the rpm the tiniest bit to minimize the cabin
> noise. The pilot can adjust the synchrophaser to get the prop blades
> passing the fuselage at the same time or alternately or whatever makes
> the least noise. The synchro will then hold everything right there.
> If an airplane doesn't have either of those and the RPM is
> obviously off, the pilot is either ignoring it or doesn't notice. He
> can adjust one prop lever to stop it.
> An excerpt from Hartzell's material at
> http://www.hartzellprop.com/engineering/engineering_constant_speed.htm
>
> "On twin-engine aircraft, whether they are reciprocating or
> turbine-powered, the propeller governor or synchronizer may be
> supplemented with an electronic synchrophaser. One purpose of the
> synchrophaser is to match the two propellers to the same RPM. However,
> the more difficult and relevant task of the synchrophaser is to match
> not only the RPM, but also the phase position between the two
> propellers. In other words, when a blade on one propeller passes the
> fuselage, a blade on the other propeller is operating at the same
> speed and is at a specific and predefined relative position. In doing
> so, airframe vibration and cabin noise can be substantially reduced. "
>
> Dan

Thanks Dan. I was referring to the few seconds after the engines are
throttled back on jump run......during that interval when the engines are
revving down. This is when the sound is most obvious from the ground. Do the
governors or synchronizers work (or are they supposed to work) during that
brief deceleration window?
This is when the differences between the PT6's and the Garretts are most
noticeable, with the Pratts sounding "mushier". Now another ? ......Is
synchronization of twin Garretts (or other directly coupled engine/prop)
done primarily by propeller pitch adjustments without regard, within reason,
to engine RPM?

TonyP.

[muff528]

"Bertie the Bunyip" > wrote in message
.. .
> "muff528" > wrote in
> news:SMuRj.25645$TS5.1624@trnddc08:
>
>>
>> "Bertie the Bunyip" > wrote in message
>> ...
>>> "muff528" > wrote in
>>> news:krtRj.968$lc6.775@trnddc04:
>>>
>>>>
>>>> "Bertie the Bunyip" > wrote in message
>>>> .. .
>>>>> wrote in news:e508d435-db20-4b21-9c9b-
>>>>> :
>>>>>
>>>>>> On Apr 25, 4:37 am, Bertie the Bunyip > wrote:
>>>>>>> wrote in news:de5298d4-778b-475f-9321-
>>>>>>> :
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> > On 25 Apr, 11:53, Frank Olson
>>>>>>> > > wrote:
>>>>>>> >> Bertie the Bunyip wrote:
>>>>>>> >> > Chris W > wrote in
>>>>>>> >> > news:74gQj.67968$y05.19485 @newsfe22.lga:
>>>>>>>
>>>>>>> >> >> I was channel surfing the other day and caught the tail end
>>>>>>> >> >> of
>>>>>>> some
>>>>>>> >> > show
>>>>>>> >> >> about rich people and their planes. Anyway the pilot of
>>>>>>> >> >> this
>>>>> one
>>>>>>> >> > single
>>>>>>> >> >> engine turbo prop said there was no mechanical connection
>>>>> between
>>>>>>> the
>>>>>>> >> >> prop and engine. How can that be?
>>>>>>>
>>>>>>> >> > It's a free turbine. Most modern turboprops use that system.
>>>>>>> There's a
>>>>>>> >> > seperate turbine that runs the prop geabox. He's technically
>>>>>>> incorrect
>>>>>>> >> > since that turbine is part of the engine...
>>>>>>>
>>>>>>> >> > Bertie
>>>>>>>
>>>>>>> >> Rich people. More money than brains.- Hide quoted text -
>>>>>>>
>>>>>>> > I'm not in disagreement with Bertie, wouldn't dare, but it
>>>>>>> > "could be" electric drive, hydraulic drive.
>>>>>>>
>>>>>>> Nah, not on a turbine.
>>>>>>>
>>>>>>> > These are used in other vehicles. Most cars in the US
>>>>>>> > use an automatic transmission that includes a
>>>>>>> > torque convertor for example.
>>>>>>>
>>>>>>> > I am sure that it is in this case a free turbine - gas drive -
>>>>>>> > that connects to a propellor - gas-gas drive.
>>>>>>>
>>>>>>> >http://www.gasgas.com/index.shtml
>>>>>>>
>>>>>>> Yeah, almost all modern turboprops use this system. Some of the
>>>>>>> older ones, like the RR Dart or the Allisons were gear driven off
>>>>>>> the main turbine, but this is all but abandoned these days. In
>>>>>>> fact, even
>>>>> "jets"
>>>>>>> are really just ducted fan turboprops with the fan driven by a
>>>>> turbine
>>>>>>> in the exhaust.
>>>>>>>
>>>>>>> Bertie
>>>>>>
>>>>>> The Garrett TPE 331 is still a fixed turboprop. Lots of
>>>>>> those
>>>>>> flying, especially on some upscale kitplanes. Isn't the Swearingen
>>>>>> Merlin powered by those, too?
>>>>>> http://www.aircraftenginedesign.com/pictures/TPE331.gif
>>>>>>
>>>>>> Dan
>>>>>>
>>>>>
>>>>> Yeah, Garret are one of the holdouts. They're on alot of airplanes.
>>>>> the Metro, the turbine commanders. I think there's a Walter that's
>>>>> in th esame class being used on quite a few airplanes as well. The
>>>>> Pratts are all free turbines, AFAIK. The older ones are centrifugal
>>>>> engines with a revese flow, that is, the intake is on the back and
>>>>> they exhaust in front, which is why the PT6 's have those
>>>>> stovepipes just behind the prop, and the newer 120 and newers are
>>>>> axial with the air coming in the front and the fire going out the
>>>>> back. The 120 has a prop brake with which you can stop the prop
>>>>> while the engine is running ( on the ground) and use the engine for
>>>>> an APU.
>>>>>
>>>>>
>>>>> Bertie
>>>>
>>>> Amazing how after a while you can tell the difference between the
>>>> Pratts and the Garretts from the ground while the plane is at 13,500
>>>> ft above you. Many times we had a Twin Otter with Pratts and a Casa
>>>> 212 with Garretts flying on the same day and you could tell which
>>>> was on jump run just by the sound. I just assumed it was because of
>>>> the different methods of coupling the props to the powerplant.
>>>
>>> !!! I don't think I could except by seeing the airplane. Yeah, you
>>> get tuned in to any engine you're familiar with, though, don't you?
>>>
>>>
>>> Bertie
>>>
>>
>> Yeah, I think the fact that they were flying within a few minutes of
>> each other all day makes the comparison easier. The main difference
>> seems to me to be the "loudness" of the beat freq. generated by
>> slightly "out-of-sync" props, especially when the "cut" occurs just
>> before exit time. The Garretts sounded "gutsier" for lack of a better
>> term and the beat frequency amplitude was much greater than the PT6's.
>> Even during the climbout to jump altitude the Garretts seemed to sound
>> more authoritative. But that brings up another question that I have
>> wondered about. For a twin, for example, does the force of the
>> atmosphere pushing against the props have an "equalizing" effect on
>> the propeller speeds of turbine-coupled props on slightly out-of-sync
>> engines? I would intuitively think that such a moderating effect would
>> account for differences in beat sounds between them and direct-coupled
>> twins which were a few rpm's out.
>
>
>
> Well, I've only flwon one type with the turbine directly geared to the
> prop and it was a single lever operation which meant you were altering
> the power as well as the prop pitch whne you mover the lever. it had no
> autosynch so you did it the old fashioned way and it was out of synch a
> good bit of the time. I can't remember hat we had in the King Airs I
> flew, but the PW120 had an autosynch so that might account for it.
>
>
> Bertie
>

Thanks, I never thought of propellers as such complex devices. Dan's link to
Hartzell was pretty informative.
TP

[Bertie the Bunyip[_24_]]

"muff528" > wrote in
news:REvRj.11461$Rk6.9130@trnddc07:

>
> "Bertie the Bunyip" > wrote in message
> .. .
>> "muff528" > wrote in
>> news:SMuRj.25645$TS5.1624@trnddc08:
>>
>>>
>>> "Bertie the Bunyip" > wrote in message
>>> ...
>>>> "muff528" > wrote in
>>>> news:krtRj.968$lc6.775@trnddc04:
>>>>
>>>>>
>>>>> "Bertie the Bunyip" > wrote in message
>>>>> .. .
>>>>>> wrote in
>>>>>> news:e508d435-db20-4b21-9c9b-
>>>>>> :
>>>>>>
>>>>>>> On Apr 25, 4:37 am, Bertie the Bunyip > wrote:
>>>>>>>> wrote in news:de5298d4-778b-475f-9321-
>>>>>>>> :
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> > On 25 Apr, 11:53, Frank Olson
>>>>>>>> > > wrote:
>>>>>>>> >> Bertie the Bunyip wrote:
>>>>>>>> >> > Chris W > wrote in
>>>>>>>> >> > news:74gQj.67968$y05.19485 @newsfe22.lga:
>>>>>>>>
>>>>>>>> >> >> I was channel surfing the other day and caught the tail
>>>>>>>> >> >> end of
>>>>>>>> some
>>>>>>>> >> > show
>>>>>>>> >> >> about rich people and their planes. Anyway the pilot of
>>>>>>>> >> >> this
>>>>>> one
>>>>>>>> >> > single
>>>>>>>> >> >> engine turbo prop said there was no mechanical connection
>>>>>> between
>>>>>>>> the
>>>>>>>> >> >> prop and engine. How can that be?
>>>>>>>>
>>>>>>>> >> > It's a free turbine. Most modern turboprops use that
>>>>>>>> >> > system.
>>>>>>>> There's a
>>>>>>>> >> > seperate turbine that runs the prop geabox. He's
>>>>>>>> >> > technically
>>>>>>>> incorrect
>>>>>>>> >> > since that turbine is part of the engine...
>>>>>>>>
>>>>>>>> >> > Bertie
>>>>>>>>
>>>>>>>> >> Rich people. More money than brains.- Hide quoted text -
>>>>>>>>
>>>>>>>> > I'm not in disagreement with Bertie, wouldn't dare, but it
>>>>>>>> > "could be" electric drive, hydraulic drive.
>>>>>>>>
>>>>>>>> Nah, not on a turbine.
>>>>>>>>
>>>>>>>> > These are used in other vehicles. Most cars in the US
>>>>>>>> > use an automatic transmission that includes a
>>>>>>>> > torque convertor for example.
>>>>>>>>
>>>>>>>> > I am sure that it is in this case a free turbine - gas drive
>>>>>>>> > - that connects to a propellor - gas-gas drive.
>>>>>>>>
>>>>>>>> >http://www.gasgas.com/index.shtml
>>>>>>>>
>>>>>>>> Yeah, almost all modern turboprops use this system. Some of the
>>>>>>>> older ones, like the RR Dart or the Allisons were gear driven
>>>>>>>> off the main turbine, but this is all but abandoned these days.
>>>>>>>> In fact, even
>>>>>> "jets"
>>>>>>>> are really just ducted fan turboprops with the fan driven by a
>>>>>> turbine
>>>>>>>> in the exhaust.
>>>>>>>>
>>>>>>>> Bertie
>>>>>>>
>>>>>>> The Garrett TPE 331 is still a fixed turboprop. Lots of
>>>>>>> those
>>>>>>> flying, especially on some upscale kitplanes. Isn't the
>>>>>>> Swearingen Merlin powered by those, too?
>>>>>>> http://www.aircraftenginedesign.com/pictures/TPE331.gif
>>>>>>>
>>>>>>> Dan
>>>>>>>
>>>>>>
>>>>>> Yeah, Garret are one of the holdouts. They're on alot of
>>>>>> airplanes. the Metro, the turbine commanders. I think there's a
>>>>>> Walter that's in th esame class being used on quite a few
>>>>>> airplanes as well. The Pratts are all free turbines, AFAIK. The
>>>>>> older ones are centrifugal engines with a revese flow, that is,
>>>>>> the intake is on the back and they exhaust in front, which is why
>>>>>> the PT6 's have those stovepipes just behind the prop, and the
>>>>>> newer 120 and newers are axial with the air coming in the front
>>>>>> and the fire going out the back. The 120 has a prop brake with
>>>>>> which you can stop the prop while the engine is running ( on the
>>>>>> ground) and use the engine for an APU.
>>>>>>
>>>>>>
>>>>>> Bertie
>>>>>
>>>>> Amazing how after a while you can tell the difference between the
>>>>> Pratts and the Garretts from the ground while the plane is at
>>>>> 13,500 ft above you. Many times we had a Twin Otter with Pratts
>>>>> and a Casa 212 with Garretts flying on the same day and you could
>>>>> tell which was on jump run just by the sound. I just assumed it
>>>>> was because of the different methods of coupling the props to the
>>>>> powerplant.
>>>>
>>>> !!! I don't think I could except by seeing the airplane. Yeah, you
>>>> get tuned in to any engine you're familiar with, though, don't you?
>>>>
>>>>
>>>> Bertie
>>>>
>>>
>>> Yeah, I think the fact that they were flying within a few minutes of
>>> each other all day makes the comparison easier. The main difference
>>> seems to me to be the "loudness" of the beat freq. generated by
>>> slightly "out-of-sync" props, especially when the "cut" occurs just
>>> before exit time. The Garretts sounded "gutsier" for lack of a
>>> better term and the beat frequency amplitude was much greater than
>>> the PT6's. Even during the climbout to jump altitude the Garretts
>>> seemed to sound more authoritative. But that brings up another
>>> question that I have wondered about. For a twin, for example, does
>>> the force of the atmosphere pushing against the props have an
>>> "equalizing" effect on the propeller speeds of turbine-coupled props
>>> on slightly out-of-sync engines? I would intuitively think that such
>>> a moderating effect would account for differences in beat sounds
>>> between them and direct-coupled twins which were a few rpm's out.
>>
>>
>>
>> Well, I've only flwon one type with the turbine directly geared to
>> the prop and it was a single lever operation which meant you were
>> altering the power as well as the prop pitch whne you mover the
>> lever. it had no autosynch so you did it the old fashioned way and it
>> was out of synch a good bit of the time. I can't remember hat we had
>> in the King Airs I flew, but the PW120 had an autosynch so that might
>> account for it.
>>
>>
>> Bertie
>>
>
> Thanks, I never thought of propellers as such complex devices. Dan's
> link to Hartzell was pretty informative.


On the fixed shaft turboprops they're extremely complex. All sorts of
gadgets on them to keep them under control. on the old Allisons the most
common reason for shutdown by far was a prop problem of one type or
another. but giving your observation about the Garret vs PW it's
probably due to the Garret fineing off as the throttles close as opposed
to the Pratts where they do, but not so much...


Bertie

[K l e i n]

On Apr 28, 9:03*pm, Bertie the Bunyip > wrote:
> "muff528" > wrote innews:REvRj.11461$Rk6.9130@trnddc07:
>
>
>
>
>
>
>
> > "Bertie the Bunyip" > wrote in message
> .. .
> >> "muff528" > wrote in
> >>news:SMuRj.25645$TS5.1624@trnddc08:
>
> >>> "Bertie the Bunyip" > wrote in message
> ...
> >>>> "muff528" > wrote in
> >>>>news:krtRj.968$lc6.775@trnddc04:
>
> >>>>> "Bertie the Bunyip" > wrote in message
> .. .
> >>>>>> wrote in
> >>>>>> news:e508d435-db20-4b21-9c9b-
> >>>>>> :
>
> >>>>>>> On Apr 25, 4:37 am, Bertie the Bunyip > wrote:
> >>>>>>>> wrote in news:de5298d4-778b-475f-9321-
> >>>>>>>> :
>
> >>>>>>>> > On 25 Apr, 11:53, Frank Olson
> >>>>>>>> > > wrote:
> >>>>>>>> >> Bertie the Bunyip wrote:
> >>>>>>>> >> > Chris W > wrote in
> >>>>>>>> >> > news:74gQj.67968$y05.19485 @newsfe22.lga:
>
> >>>>>>>> >> >> I was channel surfing the other day and caught the tail
> >>>>>>>> >> >> end of
> >>>>>>>> some
> >>>>>>>> >> > show
> >>>>>>>> >> >> about rich people and their planes. *Anyway the pilot of
> >>>>>>>> >> >> this
> >>>>>> one
> >>>>>>>> >> > single
> >>>>>>>> >> >> engine turbo prop said there was no mechanical connection
> >>>>>> between
> >>>>>>>> the
> >>>>>>>> >> >> prop and engine. *How can that be?
>
> >>>>>>>> >> > It's a free turbine. Most modern turboprops use that
> >>>>>>>> >> > system.
> >>>>>>>> There's a
> >>>>>>>> >> > seperate turbine that runs the prop geabox. He's
> >>>>>>>> >> > technically
> >>>>>>>> incorrect
> >>>>>>>> >> > since that turbine is part of the engine...
>
> >>>>>>>> >> > Bertie
>
> >>>>>>>> >> Rich people. *More money than brains.- Hide quoted text -
>
> >>>>>>>> > I'm not in disagreement with Bertie, wouldn't dare, but it
> >>>>>>>> > "could be" electric drive, hydraulic drive.
>
> >>>>>>>> Nah, not on a turbine.
>
> >>>>>>>> > These are used in other vehicles. Most cars in the US
> >>>>>>>> > use an automatic transmission that includes a
> >>>>>>>> > torque convertor for example.
>
> >>>>>>>> > I am sure that it is in this case a free turbine - gas drive
> >>>>>>>> > - that connects to a propellor - gas-gas drive.
>
> >>>>>>>> >http://www.gasgas.com/index.shtml
>
> >>>>>>>> Yeah, almost all modern turboprops use this system. Some of the
> >>>>>>>> older ones, like the RR Dart or the Allisons were gear driven
> >>>>>>>> off the main turbine, but this is all but abandoned these days.
> >>>>>>>> In fact, even
> >>>>>> "jets"
> >>>>>>>> are really just ducted fan turboprops with the fan driven by a
> >>>>>> turbine
> >>>>>>>> in the exhaust.
>
> >>>>>>>> Bertie
>
> >>>>>>> * * * * The Garrett TPE 331 is still a fixed turboprop. Lots of
> >>>>>>> * * * * those
> >>>>>>> flying, especially on some upscale kitplanes. Isn't the
> >>>>>>> Swearingen Merlin powered by those, too?
> >>>>>>>http://www.aircraftenginedesign.com/pictures/TPE331.gif
>
> >>>>>>> * Dan
>
> >>>>>> Yeah, Garret are one of the holdouts. They're on alot of
> >>>>>> airplanes. the Metro, the turbine commanders. I think there's a
> >>>>>> Walter that's in th esame class being used on quite a few
> >>>>>> airplanes as well. The Pratts are all free turbines, AFAIK. The
> >>>>>> older ones are centrifugal engines with a revese flow, that is,
> >>>>>> the intake is on the back and they exhaust in front, which is why
> >>>>>> the PT6 's have those stovepipes just behind the prop, and the
> >>>>>> newer 120 and newers are axial with the air coming in the front
> >>>>>> and the fire going out the back. The 120 has a prop brake with
> >>>>>> which you can stop the prop while the engine is running ( on the
> >>>>>> ground) and use the engine for an APU.
>
> >>>>>> Bertie
>
> >>>>> Amazing how after a while you can tell the difference between the
> >>>>> Pratts and the Garretts from the ground while the plane is at
> >>>>> 13,500 ft above you. Many times we had a Twin Otter with Pratts
> >>>>> and a Casa 212 with Garretts flying on the same day and you could
> >>>>> tell which was on jump run just by the sound. I just assumed it
> >>>>> was because of the different methods of coupling the props to the
> >>>>> powerplant.
>
> >>>> !!! I don't think I could except by seeing the airplane. Yeah, you
> >>>> get tuned in to any engine you're familiar with, though, don't you?
>
> >>>> Bertie
>
> >>> Yeah, I think the fact that they were flying within a few minutes of
> >>> each other all day makes the comparison easier. The main difference
> >>> seems to me to be the "loudness" of the beat freq. generated by
> >>> slightly "out-of-sync" props, especially when the "cut" occurs just
> >>> before exit time. The Garretts sounded "gutsier" for lack of a
> >>> better term and the beat frequency amplitude was much greater than
> >>> the PT6's. Even during the climbout to jump altitude the Garretts
> >>> seemed to sound more authoritative. But that brings up another
> >>> question that I have wondered about. For a twin, for example, does
> >>> the force of the atmosphere pushing against the props have an
> >>> "equalizing" effect on the propeller speeds of turbine-coupled props
> >>> on slightly out-of-sync engines? I would intuitively think that such
> >>> a moderating effect would account for differences in beat sounds
> >>> between them and direct-coupled twins which were a few rpm's out.
>
> >> Well, I've only flwon one type with the turbine directly geared to
> >> the prop and it was a single lever operation which meant you were
> >> altering the power as well as the prop pitch whne you mover the
> >> lever. it had no autosynch so you did it the old fashioned way and it
> >> was out of synch a good bit of the time. I can't remember hat we had
> >> in the King Airs I flew, but the PW120 had an autosynch so that might
> >> account for it.
>
> >> Bertie
>
> > Thanks, I never thought of propellers as such complex devices. Dan's
> > link to Hartzell was pretty informative.
>
> On the fixed shaft turboprops they're extremely complex. All sorts of
> gadgets on them to keep them under control. on the old Allisons the most
> common reason for shutdown by far was a prop problem of one type or
> another. but giving your observation about the Garret vs PW it's
> probably due to the Garret fineing off as the throttles close as opposed
> to the Pratts where they do, but not so much...
>
> Bertie- Hide quoted text -
>
> - Show quoted text -

Here are a few numbers for you (taken from my Flight Safety big book
on the Twin Commander 1000). This airplane uses the Garrett TPE331-10
engines with 1000 shaft horsepower, flat rated back to 800 hp. The
800 hp are available up to 18,000 ft. Naturally, this means these
airplanes climb like scalded cats (3000+ fpm.) The engine has all the
turbines on a single shaft which runs at 41,730 rpm maximum. Cruise
rpm is 96-100%. This shaft is geared down by a planetary gear
reduction with 26:1 ratio, giving a max prop rpm of 1591 rpm. Engine
rpm is pretty much controlled by propellor blade angle. A Beta mode
(reverse thrust) is available for ground use only. No question about
it, they are very loud. Even in ground idle mode, the prop rpm is 65%
of max. One always receives the Twin Commander salute (index fingers
in both ears) from anybody standing around on the ramp. One advantage
of the single shaft design is fuel efficiency. The airplane cruises
at 300+ knots true at 26,000 ft on 80 gph after a maximum gross weight
takeoff of 11,700 lbs. Try that in your P&W turboprop. ;-) Beside
the Twin Commanders, these engines are also used in the Mitsubishi
MU-2. TBO on the engines is 5,000 hours with a hot section inspection
at 2500 hours.

K l e i n

[muff528]

Here are a few numbers for you (taken from my Flight Safety big book
on the Twin Commander 1000). This airplane uses the Garrett TPE331-10
engines with 1000 shaft horsepower, flat rated back to 800 hp. The
800 hp are available up to 18,000 ft. Naturally, this means these
airplanes climb like scalded cats (3000+ fpm.) The engine has all the
turbines on a single shaft which runs at 41,730 rpm maximum. Cruise
rpm is 96-100%. This shaft is geared down by a planetary gear
reduction with 26:1 ratio, giving a max prop rpm of 1591 rpm. Engine
rpm is pretty much controlled by propellor blade angle. A Beta mode
(reverse thrust) is available for ground use only. No question about
it, they are very loud. Even in ground idle mode, the prop rpm is 65%
of max. One always receives the Twin Commander salute (index fingers
in both ears) from anybody standing around on the ramp. One advantage
of the single shaft design is fuel efficiency. The airplane cruises
at 300+ knots true at 26,000 ft on 80 gph after a maximum gross weight
takeoff of 11,700 lbs. Try that in your P&W turboprop. ;-) Beside
the Twin Commanders, these engines are also used in the Mitsubishi
MU-2. TBO on the engines is 5,000 hours with a hot section inspection
at 2500 hours.

K l e i n


Yes!.........LOUD...........That's the word I was looking for! :-))
Always a treat to get on a Casa load and watch runway rapidly drop away
through the open tailgate when the pilots decided to do a "high-performance"
takeoff.
With 23-24 people sitting toboggan-style on the floor the only outside view
is through the tailgate.

TP