Why no CAS turboprops?

I presume one reason high-bypass turbofans (A10) are preferred vice
turboprops is that in the balance the fans are a more economical
choice. No props to get nicked, no gearbox to worry about, over-all
less maintenance and less cost. And quieter - the Beech 1900s flying
overhead here really howl when trying to make an ETA. Less noise is
good when prowling around. But what is really good is a supersonic
approach when dealing with a known show target- surprise!
Walt BJ

In article ,
says...

"Abe" wrote in message
...
In article dGKKb.8616$6l1.5192@okepread03, says...
Would a helicopter count as a turboprop? Turbo-blade? :-)

Helo engines are usually referred to as "turboshaft", which aside from
sounding suspiciously like a porn film, is possibly just another name
for a turboprop.

I wonder what the V-22 engines are. Turboprop when facing forward,
turboshaft when facing upward?

Isn't the presence of a transmission in the latter what helps delineate it
from the former?

Turboprops have transmissions also, I'm sure. At least, you'd need to
put some gearing between engine and props.

Abe wrote:

Helo engines are usually referred to as "turboshaft", which aside from
sounding suspiciously like a porn film, is possibly just another name
for a turboprop.

A turboprop engine is configured so the output shaft will
mount a propeller. It has thrust bearings and is geared to
drive a propeller directly.

A turboshaft delivers its output to a shaft which may be
connected to nearly anything except directly to a propeller.

Rick

"Charles Gray" wrote in message
...
On Tue, 6 Jan 2004 22:21:45 -0000, Abe wrote:
On a modern battlefield, I wouldn't give the A-10 much of a life span.
It might armoured like a tank, but it's sitting duck.

How would the A-10 survive in a theatre full of modern vehicle-mounted
SAMs, I wonder?

Not well-- if you sent it in alone. However, with SEAD it would do
pretty well-- A-10's in the first gulf war took plenty of fire from
shoulder fired SAMs' as well as cannon fire and came back in a
landable condition-- imagine an F-22 or F-35 doing the same. Also,
unlike the faster, more "sexy" aircraft, slow CAS can loiter in the
area, prepared to shoot up the odd target.

But doesn't it sort of defeat the very idea of "survivable combat aircraft"
when you need a SEAD package et al to keep it alive?

Sure, passive protection will increase your survival chances in case of hit
but does it really help if you're so slow that you get hit much more often?

It should also be noted that During Desert Storm, A-10's did very
well:

Actually, A-10 operations to some well-defended areas were restricted after
some were shot down. Against something like Crotale or SA-15, I'd rate
A-10's survival odds as very low. Or gun systems like Marksman,
Tunguska...those have _very high_ hit probabilities. A turboprop CAS plane
would be even more vulnerable.

Of course, if you're content about bombing some hapless natives, then maybe
you don't have to worry about such threats and slow attack planes are
viable.

"Abe" wrote in message
...
In article ,
says...

"Abe" wrote in message
...
In article dGKKb.8616$6l1.5192@okepread03, says...
Would a helicopter count as a turboprop? Turbo-blade? :-)

Helo engines are usually referred to as "turboshaft", which aside from
sounding suspiciously like a porn film, is possibly just another name
for a turboprop.

I wonder what the V-22 engines are. Turboprop when facing forward,
turboshaft when facing upward?

Isn't the presence of a transmission in the latter what helps delineate
it
from the former?

Turboprops have transmissions also, I'm sure. At least, you'd need to
put some gearing between engine and props.

Some gearing yes; but I don't think they have anything as complex as the
transmissions employed on helos. Just a guess, though.

Brooks

In article k.net,
says...
Abe wrote:

Helo engines are usually referred to as "turboshaft", which aside from
sounding suspiciously like a porn film, is possibly just another name
for a turboprop.

A turboprop engine is configured so the output shaft will
mount a propeller. It has thrust bearings and is geared to
drive a propeller directly.

A turboshaft delivers its output to a shaft which may be
connected to nearly anything except directly to a propeller.

I'm a bit hazy on the difference here. Are you saying a turboprop has
no reduction gearing between engine and propellor?

If it does have gearing, then I'm not sure of the clear-cut difference
between that and a more complex transmission. Could you elaborate?

Abe wrote:

I'm a bit hazy on the difference here. Are you saying a turboprop has
no reduction gearing between engine and propellor?

No, a turboprop engine has reduction gearing between the
power turbine and the propeller shaft. The output shaft on a
turboprop engine is the propeller shaft, it is reduced in
speed to that required by the propeller and incorporates a
thrust bearing to transfer thrust to the engine mounts.

If it does have gearing, then I'm not sure of the clear-cut difference
between that and a more complex transmission. Could you elaborate?

If by "more complex transmission" you mean that of a
turboshaft then you are still a bit confused. The
"transmission" or reduction gear can and often is very
simple and less complicated than that of a turboprop engine.

Some turboshaft engines do not even have a reduction gear or
transmission, the power turbine is designed to turn at the
required speed for the application.

Look at it as a turboprop is only made to turn a propeller.
A turboshaft can turn everything else

Rick

"Kevin Brooks" wrote:


"Abe" wrote in message
.. .
In article ,
says...

"Abe" wrote in message
...
In article dGKKb.8616$6l1.5192@okepread03, says...
Would a helicopter count as a turboprop? Turbo-blade? :-)

Helo engines are usually referred to as "turboshaft", which aside from
sounding suspiciously like a porn film, is possibly just another name
for a turboprop.

I wonder what the V-22 engines are. Turboprop when facing forward,
turboshaft when facing upward?

Isn't the presence of a transmission in the latter what helps delineate
it
from the former?

Turboprops have transmissions also, I'm sure. At least, you'd need to
put some gearing between engine and props.

Some gearing yes; but I don't think they have anything as complex as the
transmissions employed on helos. Just a guess, though.

Brooks

Yes, that's roughly correct AFIK. I know turboprops but not
Helicopters and I'd think that helicopters would require much
more complicated transmissions. Turboprops aren't very
complicated, just quite rugged, about 10 to 1 or so reduction
planetary gear-train with a 'torsion bar' type of driveshaft to
measure torque and some method of preventing the prop from
driving the engine (
--

-Gord.

Rick wrote:

Abe wrote:

Helo engines are usually referred to as "turboshaft", which aside from
sounding suspiciously like a porn film, is possibly just another name
for a turboprop.

A turboprop engine is configured so the output shaft will
mount a propeller. It has thrust bearings and is geared to
drive a propeller directly.

A turboshaft delivers its output to a shaft which may be
connected to nearly anything except directly to a propeller.

Rick

What aircraft would use that setup Rick? I can't imagine how you
could drive a prop directly from a turbine engine with no
reduction gearing? (or did I misread you?)
--

-Gord.

"Gord Beaman" wrote in message
...
"Kevin Brooks" wrote:


"Abe" wrote in message
.. .
In article ,
says...

"Abe" wrote in message
...
In article dGKKb.8616$6l1.5192@okepread03, says...
Would a helicopter count as a turboprop? Turbo-blade? :-)

Helo engines are usually referred to as "turboshaft", which aside
from
sounding suspiciously like a porn film, is possibly just another
name
for a turboprop.

I wonder what the V-22 engines are. Turboprop when facing forward,
turboshaft when facing upward?

Isn't the presence of a transmission in the latter what helps
delineate
it
from the former?

Turboprops have transmissions also, I'm sure. At least, you'd need to
put some gearing between engine and props.

Some gearing yes; but I don't think they have anything as complex as the
transmissions employed on helos. Just a guess, though.

Brooks

Yes, that's roughly correct AFIK. I know turboprops but not
Helicopters and I'd think that helicopters would require much
more complicated transmissions. Turboprops aren't very
complicated, just quite rugged, about 10 to 1 or so reduction
planetary gear-train with a 'torsion bar' type of driveshaft to
measure torque and some method of preventing the prop from
driving the engine (

Thanks. I don't know squat about turboprops, but I do know that helo
transmissions are typically pretty complex and are a rather common source of
maintenance trouble, not to mention being one of the more vulnerable spots
in terms of combat damage.

Brooks

--

-Gord.