Whats the deal with counter-rotating props?

[Dico]

Hello,

We're looking into a twin and the Twin Comanche is on our list. I know
that the later models have the counter rotating props -- although i
don't know too much about what this means, other than its "better".

We fly a mooney now and thus I don't worry about the prop -- as long as
it keeps spinning.

Is there a web site that gives a good explanation as to why I want CR
props. There are hundreds of the earlier model Twin Comanches flying
without the CR props --- so what does someone with 300 hours single
engine time need to worry about? What actually goes wrong? And when
it does, what happens? I hear "critical engine" but it means very
little to me.

I like to fly and try to be very careful when I do fly... but I don't
follow too much aviation stuff other than how it affects me -- so I'm
not exactly a "buff", hence the above questions which may seem obvious
to many.

Why are we looking at a Twin Comanche? Because its a twin, safer for
IFR flight (perhaps this is only preceived), plus we live on the east
coast on an island so we're flying over water quite a bit. Also this
plane has decent speed and is an "economical" twin. We rarely fly with
4 people, so we don't need any more seats than 4.

Any help or links to help would be appreciated.

Thanks,

Dico

[Michael Ware]

Think about what you do with your right foot during takeoff.

"Dico" > wrote in message
oups.com...
> Hello,
>
> We're looking into a twin and the Twin Comanche is on our list. I know
> that the later models have the counter rotating props -- although i
> don't know too much about what this means, other than its "better".
> Thanks,
>
> Dico
>

[Ron Wanttaja]

On Sun, 29 Jan 2006 04:17:23 GMT, "Michael Ware" > wrote:


> "Dico" > wrote in message
> oups.com...
> >
> > We're looking into a twin and the Twin Comanche is on our list. I know
> > that the later models have the counter rotating props -- although i
> > don't know too much about what this means, other than its "better".
> > Thanks,
>
> Think about what you do with your right foot during takeoff.

Most trigear pilots are scratching themselves behind the right ear. :-)

Ron Wanttaja

[Dico]

I push the rudder with my right foot. This doesn't really answer my
questions though. Like I said, I'm not a "buff" and don't know much
about twins.

-Dico

[Michael Ware]

that's right. i am trying to get you to think why you have to do this,
therefore leading to the reasons why you might want counter-rotating props.

"Dico" > wrote in message
oups.com...
> I push the rudder with my right foot. This doesn't really answer my
> questions though. Like I said, I'm not a "buff" and don't know much
> about twins.
>
> -Dico
>

[Dico]

So with counter rotating props I won't have the plane want to go left?
Or I'd really have to hammer down the right rudder? Even worse if one
engine quit, I could be screwed? And I'm guessing the critical engine
comes into play here. Although I'm not sure if the critical engine
means its the good one (its critical you keep it) or the bad one (its
critical if you lose it)....

-Dico

[Gerry Caron]

"Dico" > wrote in message
oups.com...
> So with counter rotating props I won't have the plane want to go left?
> Or I'd really have to hammer down the right rudder? Even worse if one
> engine quit, I could be screwed? And I'm guessing the critical engine
> comes into play here. Although I'm not sure if the critical engine
> means its the good one (its critical you keep it) or the bad one (its
> critical if you lose it)....
>
> -Dico
>

Try Googling "minimum controllable airspeed"

Gerry

[Michael Ware]

"Dico" > wrote in message
oups.com...
> So with counter rotating props I won't have the plane want to go left?

Correct. Not when they are both running, anyway!

> Or I'd really have to hammer down the right rudder? Even worse if one
> engine quit, I could be screwed? And I'm guessing the critical engine
> comes into play here. Although I'm not sure if the critical engine
> means its the good one (its critical you keep it) or the bad one (its
> critical if you lose it)....

check this out.

http://avstop.com/Technical/twins.htm

Remember, too, that with a twin (except for planes like a Cessna 337) the
engines are not on the centerline of the fuselage, they are offset a few
feet.

>
> -Dico
>

[BTIZ]

think of the thrust line of the propeller
and for the smart guy that mentioned right foot for take off.. that's some
thrust but also P-factor

without counter rotating propellers,
consider downward arc of prop has more thrust, left engine, downward prop is
next to fuselage, right engine it is on the right side of that engine and
farther from fuselage, if the left (critical) engine fails then all that
thrust is way out on the right side moment arm causing yaw, and if real
slow, roll factors to deal with.

counter rotating propeller means the right engine the propeller rotates
counter clockwise, moving that thrust line closer to the fuselage, (now same
on both sides) and reduces the yaw action in the event of either engine
failing.. thus negating the "critical engine" factor.

You need to pick up and read a good multi engine training manual.. something
by Kershner

BT

"Dico" > wrote in message
oups.com...
> Hello,
>
> We're looking into a twin and the Twin Comanche is on our list. I know
> that the later models have the counter rotating props -- although i
> don't know too much about what this means, other than its "better".
>
> We fly a mooney now and thus I don't worry about the prop -- as long as
> it keeps spinning.
>
> Is there a web site that gives a good explanation as to why I want CR
> props. There are hundreds of the earlier model Twin Comanches flying
> without the CR props --- so what does someone with 300 hours single
> engine time need to worry about? What actually goes wrong? And when
> it does, what happens? I hear "critical engine" but it means very
> little to me.
>
> I like to fly and try to be very careful when I do fly... but I don't
> follow too much aviation stuff other than how it affects me -- so I'm
> not exactly a "buff", hence the above questions which may seem obvious
> to many.
>
> Why are we looking at a Twin Comanche? Because its a twin, safer for
> IFR flight (perhaps this is only preceived), plus we live on the east
> coast on an island so we're flying over water quite a bit. Also this
> plane has decent speed and is an "economical" twin. We rarely fly with
> 4 people, so we don't need any more seats than 4.
>
> Any help or links to help would be appreciated.
>
> Thanks,
>
> Dico
>

[BTIZ]

MORE critical if you loose it

consider the single engine service ceiling of most light twin aircraft, and
where you would be flying it

IIRC the SE service ceiling of a Twin Comanche is about 3800MSL (Density
Altitude), or below the ground level of most places out here in the mid
west.

The second engine, on failure of the first engine, will only lead you to a
landing location, not necessarily of your choosing.

BT

"Dico" > wrote in message
oups.com...
> So with counter rotating props I won't have the plane want to go left?
> Or I'd really have to hammer down the right rudder? Even worse if one
> engine quit, I could be screwed? And I'm guessing the critical engine
> comes into play here. Although I'm not sure if the critical engine
> means its the good one (its critical you keep it) or the bad one (its
> critical if you lose it)....
>
> -Dico
>

[BTIZ]

interesting... but a diagram with thrust vectors and with and without
counterrotating propellors would add to the clarification for this poster
BT

"Michael Ware" > wrote in message
. ..
>
> "Dico" > wrote in message
> oups.com...
>> So with counter rotating props I won't have the plane want to go left?
>
> Correct. Not when they are both running, anyway!
>
>> Or I'd really have to hammer down the right rudder? Even worse if one
>> engine quit, I could be screwed? And I'm guessing the critical engine
>> comes into play here. Although I'm not sure if the critical engine
>> means its the good one (its critical you keep it) or the bad one (its
>> critical if you lose it)....
>
> check this out.
>
> http://avstop.com/Technical/twins.htm
>
> Remember, too, that with a twin (except for planes like a Cessna 337) the
> engines are not on the centerline of the fuselage, they are offset a few
> feet.
>
>>
>> -Dico
>>
>
>

[Rob McDonald]

What would you multi folks recommend as good "introductory" reading for
people considering moving up to a twin? Is there a book with a good
discussion of the issues pro and con on moving from a single to a twin?

Rob


"BTIZ" > wrote in
news:CXXCf.53524$V.31153@fed1read04:

> ...
> You need to pick up and read a good multi engine training manual..
> something by Kershner
>
> BT

[Dico]

Thanks for the link.

A very interesting read! I'm that much smarter now!

Another question... can you retro fit planes so that they have CR
props? What kind of cost/job is involved? I am guessing that you'd
need an engine that turns the other way and a different prop... but i'm
sure there is a lot more to it.

-dr

[Henry A. Spellman]

If you are really considering a Twin Comanche, the best places for
answers to your questions are the International Comanche Society
(comancheflyer.com) and the Comanche Owners' Forum in the motor
transport section at delphiforums.com. There is a world of information
regarding Comanches at both of those sites.

Hank
Henry A. Spellman
Comanche N5903P

Dico wrote:
> Hello,
>
> We're looking into a twin and the Twin Comanche is on our list. I know
> that the later models have the counter rotating props -- although i
> don't know too much about what this means, other than its "better".
>

[Mike Noel]

I didn't notice anyone bring this up in the thread. The AOPA published some
interesting stuff on the Twin Commanche without CR props since they were
giving one away last year. With the older style twin, if you slow it down
too much with the engines still developing thrust, it can flip over on its
back. One of the wings is effectively flying at a couple of degrees higher
angle of attach due to the prop airflow. I think this is the main reason
the newer Twin Comanches went to CR props.

--
Mike Noel,
Tucson, Arizona

'Men never do evil so completely and cheerfully as when they do it from
religious conviction.'

-Blaise Pascal
"Dico" > wrote in message
oups.com...
> Hello,
>
> We're looking into a twin and the Twin Comanche is on our list. I know
> that the later models have the counter rotating props -- although i
> don't know too much about what this means, other than its "better".
>
> We fly a mooney now and thus I don't worry about the prop -- as long as
> it keeps spinning.
>
> Is there a web site that gives a good explanation as to why I want CR
> props. There are hundreds of the earlier model Twin Comanches flying
> without the CR props --- so what does someone with 300 hours single
> engine time need to worry about? What actually goes wrong? And when
> it does, what happens? I hear "critical engine" but it means very
> little to me.
>
> I like to fly and try to be very careful when I do fly... but I don't
> follow too much aviation stuff other than how it affects me -- so I'm
> not exactly a "buff", hence the above questions which may seem obvious
> to many.
>
> Why are we looking at a Twin Comanche? Because its a twin, safer for
> IFR flight (perhaps this is only preceived), plus we live on the east
> coast on an island so we're flying over water quite a bit. Also this
> plane has decent speed and is an "economical" twin. We rarely fly with
> 4 people, so we don't need any more seats than 4.
>
> Any help or links to help would be appreciated.
>
> Thanks,
>
> Dico
>

[Dico]

Thanks!

I will check out those sites!

-Dico

[BTIZ]

You would have to find if there is an STC to change an aircraft without CR
to CR
It involves more than just swapping the engine and propeller, also the
"rigging", and testing for the new MCA that the STC owner would have
completed and submitted to the FAA for certification.
BT

"Dico" > wrote in message
oups.com...
> Thanks for the link.
>
> A very interesting read! I'm that much smarter now!
>
> Another question... can you retro fit planes so that they have CR
> props? What kind of cost/job is involved? I am guessing that you'd
> need an engine that turns the other way and a different prop... but i'm
> sure there is a lot more to it.
>
> -dr
>

[Jim Carter]

Mike,
Doesn't that happen in any non-counter-rotating and
non-centerline-thrust twin when you try to operate below Vmc/se? It's
been a few years, so I have to ask: do they still require a Vmc/se
demonstration for the multi ticket?


> -----Original Message-----
> From: Mike Noel ]
> Posted At: Sunday, January 29, 2006 3:05 PM
> Posted To: rec.aviation.owning
> Conversation: Whats the deal with counter-rotating props?
> Subject: Re: Whats the deal with counter-rotating props?
>
> I didn't notice anyone bring this up in the thread. The AOPA
published
> some
> interesting stuff on the Twin Commanche without CR props since they
were
> giving one away last year. With the older style twin, if you slow it
down
> too much with the engines still developing thrust, it can flip over on
its
> back. One of the wings is effectively flying at a couple of degrees
> higher
> angle of attach due to the prop airflow. I think this is the main
reason
> the newer Twin Comanches went to CR props.
>
> --
> Mike Noel,
> Tucson, Arizona
>
> 'Men never do evil so completely and cheerfully as when they do it
from
> religious conviction.'
>
> -Blaise Pascal
> "Dico" > wrote in message
> oups.com...
> > Hello,
> >
> > We're looking into a twin and the Twin Comanche is on our list. I
know
> > that the later models have the counter rotating props -- although i
> > don't know too much about what this means, other than its "better".
> >
> > We fly a mooney now and thus I don't worry about the prop -- as long
as
> > it keeps spinning.
> >
> > Is there a web site that gives a good explanation as to why I want
CR
> > props. There are hundreds of the earlier model Twin Comanches
flying
> > without the CR props --- so what does someone with 300 hours single
> > engine time need to worry about? What actually goes wrong? And
when
> > it does, what happens? I hear "critical engine" but it means very
> > little to me.
> >
> > I like to fly and try to be very careful when I do fly... but I
don't
> > follow too much aviation stuff other than how it affects me -- so
I'm
> > not exactly a "buff", hence the above questions which may seem
obvious
> > to many.
> >
> > Why are we looking at a Twin Comanche? Because its a twin, safer
for
> > IFR flight (perhaps this is only preceived), plus we live on the
east
> > coast on an island so we're flying over water quite a bit. Also
this
> > plane has decent speed and is an "economical" twin. We rarely fly
with
> > 4 people, so we don't need any more seats than 4.
> >
> > Any help or links to help would be appreciated.
> >
> > Thanks,
> >
> > Dico
> >

[BTIZ]

it can happen in any twin, non centerline thrust with or without CR props
it just depends on the severity and size of the rudder needed to control

yes, Vmc/se is still required on the check ride
BT

"Jim Carter" > wrote in message
et...
> Mike,
> Doesn't that happen in any non-counter-rotating and
> non-centerline-thrust twin when you try to operate below Vmc/se? It's
> been a few years, so I have to ask: do they still require a Vmc/se
> demonstration for the multi ticket?
>
>
>> -----Original Message-----
>> From: Mike Noel ]
>> Posted At: Sunday, January 29, 2006 3:05 PM
>> Posted To: rec.aviation.owning
>> Conversation: Whats the deal with counter-rotating props?
>> Subject: Re: Whats the deal with counter-rotating props?
>>
>> I didn't notice anyone bring this up in the thread. The AOPA
> published
>> some
>> interesting stuff on the Twin Commanche without CR props since they
> were
>> giving one away last year. With the older style twin, if you slow it
> down
>> too much with the engines still developing thrust, it can flip over on
> its
>> back. One of the wings is effectively flying at a couple of degrees
>> higher
>> angle of attach due to the prop airflow. I think this is the main
> reason
>> the newer Twin Comanches went to CR props.
>>
>> --
>> Mike Noel,
>> Tucson, Arizona
>>
>> 'Men never do evil so completely and cheerfully as when they do it
> from
>> religious conviction.'
>>
>> -Blaise Pascal
>> "Dico" > wrote in message
>> oups.com...
>> > Hello,
>> >
>> > We're looking into a twin and the Twin Comanche is on our list. I
> know
>> > that the later models have the counter rotating props -- although i
>> > don't know too much about what this means, other than its "better".
>> >
>> > We fly a mooney now and thus I don't worry about the prop -- as long
> as
>> > it keeps spinning.
>> >
>> > Is there a web site that gives a good explanation as to why I want
> CR
>> > props. There are hundreds of the earlier model Twin Comanches
> flying
>> > without the CR props --- so what does someone with 300 hours single
>> > engine time need to worry about? What actually goes wrong? And
> when
>> > it does, what happens? I hear "critical engine" but it means very
>> > little to me.
>> >
>> > I like to fly and try to be very careful when I do fly... but I
> don't
>> > follow too much aviation stuff other than how it affects me -- so
> I'm
>> > not exactly a "buff", hence the above questions which may seem
> obvious
>> > to many.
>> >
>> > Why are we looking at a Twin Comanche? Because its a twin, safer
> for
>> > IFR flight (perhaps this is only preceived), plus we live on the
> east
>> > coast on an island so we're flying over water quite a bit. Also
> this
>> > plane has decent speed and is an "economical" twin. We rarely fly
> with
>> > 4 people, so we don't need any more seats than 4.
>> >
>> > Any help or links to help would be appreciated.
>> >
>> > Thanks,
>> >
>> > Dico
>> >
>
>

[Jim Burns]

One of my favorites is Bob Gardner's book The Complete Multi-Engine Pilot.
It's written in a very easy to read down to earth manner. The Jeppesen
Guided Flight Discovery, Multi Engine book is very complete, but in my
opinion hard to read due to the distracting pictures and captions.
Jim


Rob McDonald" > wrote in message
...
> What would you multi folks recommend as good "introductory" reading for
> people considering moving up to a twin? Is there a book with a good
> discussion of the issues pro and con on moving from a single to a twin?
>
> Rob
>
>
> "BTIZ" > wrote in
> news:CXXCf.53524$V.31153@fed1read04:
>
>> ...
>> You need to pick up and read a good multi engine training manual..
>> something by Kershner
>>
>> BT

[Michael]

> IIRC the SE service ceiling of a Twin Comanche is about 3800MSL

You don't recally correctly, it's 5800. It goes down to 3800 if you
get the Robertson STOL kit - but that's because of the 200 lb gross
weight increase.

> The second engine, on failure of the first engine, will only lead you to a
> landing location, not necessarily of your choosing.

My experience differs. When the left (critical) engine of my Twin
Comanche failed (due to undetectable corrosion in the fuel servo) the
remaining engine took me to a normal landing at an airport. Had I been
in a single engine plane in the same situation, well, let's just say I
was over Arkansas and there was an avtive airmet for mountain
obscuration.

Michael

[The Visitor]

Mike Noel wrote:
if you slow it down
> too much with the engines still developing thrust, it can flip over on its
> back.


So you can't practice power on stalls? How about landing, on final
approach? Sounds pretty dicey. This is with both engines running?

[Michael]

> We're looking into a twin and the Twin Comanche is on our list. I know
> that the later models have the counter rotating props -- although i
> don't know too much about what this means, other than its "better".

You've gotten a lot of uninformed opinions here. I started countering
them, and after the first post decided it would be better to put it all
in one place. I have over 900 hours in Twin Comanches of various
flavors (including the CR), I've instructed in them, and I've worked on
them. Having said that, here's what you're dealing with.

There are exactly two things a counter-rotating prop does for you in
flight.

First, it relieves you of the necessity of applying right rudder on
takeoff or climb.

Second, it allows you to fly at a slightly lower airspeed in the event
the left engine fails without rolling over - which boils down to being
able to fly not just much too slow, but much, much too slow. The
reality of the situation is that the PA-30 should never be flying at
less than 90 mph unless
(a) the runway is made and you are decelerating in preparation for the
flare, in which case power is near-idle and an engine failure is
irrelevant,
(b) you are in ground effect accelerating after takeoff, in which case
an engine failure calls for an immediate idling of the throttles and a
touchdown straight ahead, or
(c) you are at a safe altitude doing training.

The downside is you get an engine where the prop, prop governor,
magnetos, alternator, vacuum pump, fuel pump, oil pump, and tach
adapter are nonstandard, and thus rarely stocked. On top of that, some
of those parts are used only on that one engine (the counter-rotating
IO-320) which is used on only that one airplane (the PA-30CR or PA-39)
which hasn't been made in decades and of which relatively few were
made. The impact on maintenance is spectacular.

The reason Piper modified the original PA-30 (in many ways - they added
control linkages, stall strips, and finally the counter-rotating props)
was to make it a more docile trainer. They didn't succeed. If you buy
the plane, make sure you find an experienced Twin Comanche instructor
to train you. No amount of time in Seminoles, Duchesses, Apaches,
Geronimos, or similar trainers prepares someone to fly a PA-30. I've
seen what happens when someone who just took an MEI ride in a Duchess
gets into a PA-30 - he can't hold on to the tail. You rarely see
PA-30's as trainers anymore, and for good reason. When MEI's with
50-100 hours multi time tried to teach in them, the carnage was
spectacular.

You do not need an STC to convert a straight PA-30 to CR. There is a
service bulletin from Piper for the conversion. All you need to do is
buy the parts and convert the engine by simple parts replacement. That
won't be cheap either.

With the low altitudes and cool weather of the East coast, the service
ceiling of the PA-30 is quite high enought (5800ft density altitude at
gross). Contrary to popular opinion, the PA-30 will fly just fine on
one engine, even at gross. BTDT.

Most of the PA-30's out there now have been modified to reduce Vmc.
The popular mod is the rudder fin (Knots-2-U and Robertson make them)
which improves lateral stability and reduces Vmc.

The real Vmc of a PA-30 without CR props is 80 mph. That's what was
designed in and verified by flight test at Swearingen. However, that
assumes you do everything right. Relatively small errors in technique
can raise that. This was fixed by raising the Vmc marking on the ASI
and in the AFM to 90 mph by AD (no changes were made to the airframe).

If you want more info, just ask

Michael

[BTIZ]

>> IIRC the SE service ceiling of a Twin Comanche is about 3800MSL
>
> You don't recally correctly, it's 5800. It goes down to 3800 if you
> get the Robertson STOL kit - but that's because of the 200 lb gross
> weight increase.

The aircraft I recently looked at did have the STOL kit.. thanx

>
>> The second engine, on failure of the first engine, will only lead you to
>> a
>> landing location, not necessarily of your choosing.
>
> My experience differs. When the left (critical) engine of my Twin
> Comanche failed (due to undetectable corrosion in the fuel servo) the
> remaining engine took me to a normal landing at an airport. Had I been
> in a single engine plane in the same situation, well, let's just say I
> was over Arkansas and there was an avtive airmet for mountain
> obscuration.
>
> Michael
>

Out here, most airports are around 3000MSL, with terrain over 8000MSL
between them, add in the density altitude factor on a standard 100F or
higher day.. and that single engine is not going to be me to an airport.
BT

[Roger]

On Sat, 28 Jan 2006 20:22:23 -0800, Ron Wanttaja
> wrote:

>On Sun, 29 Jan 2006 04:17:23 GMT, "Michael Ware" > wrote:
>
>
>> "Dico" > wrote in message
>> oups.com...
>> >
>> > We're looking into a twin and the Twin Comanche is on our list. I know
>> > that the later models have the counter rotating props -- although i
>> > don't know too much about what this means, other than its "better".
>> > Thanks,
>>
>> Think about what you do with your right foot during takeoff.
>
>Most trigear pilots are scratching themselves behind the right ear. :-)

Not the ones behind big engines. <:-))

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com
>
>Ron Wanttaja

[Jim Carter]

Michael,
You only left out one part: when a pilot does learn to fly the
PA30 and stay ahead of it, it's a blast to fly!! (especially the turbo'd
model)

> -----Original Message-----
> From: Michael ]
> Posted At: Monday, January 30, 2006 11:54 AM
> Posted To: rec.aviation.owning
> Conversation: Whats the deal with counter-rotating props?
> Subject: Re: Whats the deal with counter-rotating props?
>
> > We're looking into a twin and the Twin Comanche is on our list. I
know
> > that the later models have the counter rotating props -- although i
> > don't know too much about what this means, other than its "better".
>
> You've gotten a lot of uninformed opinions here. I started countering
> them, and after the first post decided it would be better to put it
all
> in one place. I have over 900 hours in Twin Comanches of various
> flavors (including the CR), I've instructed in them, and I've worked
on
> them. Having said that, here's what you're dealing with.
>
> There are exactly two things a counter-rotating prop does for you in
> flight.
>
> First, it relieves you of the necessity of applying right rudder on
> takeoff or climb.
>
> Second, it allows you to fly at a slightly lower airspeed in the event
> the left engine fails without rolling over - which boils down to being
> able to fly not just much too slow, but much, much too slow. The
> reality of the situation is that the PA-30 should never be flying at
> less than 90 mph unless
> (a) the runway is made and you are decelerating in preparation for the
> flare, in which case power is near-idle and an engine failure is
> irrelevant,
> (b) you are in ground effect accelerating after takeoff, in which case
> an engine failure calls for an immediate idling of the throttles and a
> touchdown straight ahead, or
> (c) you are at a safe altitude doing training.
>
> The downside is you get an engine where the prop, prop governor,
> magnetos, alternator, vacuum pump, fuel pump, oil pump, and tach
> adapter are nonstandard, and thus rarely stocked. On top of that,
some
> of those parts are used only on that one engine (the counter-rotating
> IO-320) which is used on only that one airplane (the PA-30CR or PA-39)
> which hasn't been made in decades and of which relatively few were
> made. The impact on maintenance is spectacular.
>
> The reason Piper modified the original PA-30 (in many ways - they
added
> control linkages, stall strips, and finally the counter-rotating
props)
> was to make it a more docile trainer. They didn't succeed. If you
buy
> the plane, make sure you find an experienced Twin Comanche instructor
> to train you. No amount of time in Seminoles, Duchesses, Apaches,
> Geronimos, or similar trainers prepares someone to fly a PA-30. I've
> seen what happens when someone who just took an MEI ride in a Duchess
> gets into a PA-30 - he can't hold on to the tail. You rarely see
> PA-30's as trainers anymore, and for good reason. When MEI's with
> 50-100 hours multi time tried to teach in them, the carnage was
> spectacular.
>
> You do not need an STC to convert a straight PA-30 to CR. There is a
> service bulletin from Piper for the conversion. All you need to do is
> buy the parts and convert the engine by simple parts replacement.
That
> won't be cheap either.
>
> With the low altitudes and cool weather of the East coast, the service
> ceiling of the PA-30 is quite high enought (5800ft density altitude at
> gross). Contrary to popular opinion, the PA-30 will fly just fine on
> one engine, even at gross. BTDT.
>
> Most of the PA-30's out there now have been modified to reduce Vmc.
> The popular mod is the rudder fin (Knots-2-U and Robertson make them)
> which improves lateral stability and reduces Vmc.
>
> The real Vmc of a PA-30 without CR props is 80 mph. That's what was
> designed in and verified by flight test at Swearingen. However, that
> assumes you do everything right. Relatively small errors in technique
> can raise that. This was fixed by raising the Vmc marking on the ASI
> and in the AFM to 90 mph by AD (no changes were made to the airframe).
>
> If you want more info, just ask
>
> Michael

[Mike Noel]

This if from the August 2004 issue of AOPA Pilot:

'NASA's July 1971 final report reached three conclusions about the PA-30
Twin Comanche:

* At the stall, large rolling and yawing moments occurred as a result of
asymmetric wing stall. The left wing stalled, NASA said, at an angle of
attack about 2 degrees lower than the right wing.
* These rolling and yawing moments are larger than the corrective
moments produced by aileron and rudder controls.
* The airplane exhibits a flat spin under certain conditions involving
the use of asymmetric power.'

I interpret the first two items to apply to a Comanche with both engines
operative, with only the last referring to a single engine Vmc situation.


--
Mike Noel,
Tucson, Arizona

'Men never do evil so completely and cheerfully as when they do it from
religious conviction.'

-Blaise Pascal
"Mike Noel" > wrote in message
. ..
> I didn't notice anyone bring this up in the thread. The AOPA published
some
> interesting stuff on the Twin Commanche without CR props since they were
> giving one away last year. With the older style twin, if you slow it down
> too much with the engines still developing thrust, it can flip over on its
> back. One of the wings is effectively flying at a couple of degrees
higher
> angle of attach due to the prop airflow. I think this is the main reason
> the newer Twin Comanches went to CR props.
>
> --
> Mike Noel,
> Tucson, Arizona
>
> 'Men never do evil so completely and cheerfully as when they do it from
> religious conviction.'
>
> -Blaise Pascal
> "Dico" > wrote in message
> oups.com...
> > Hello,
> >
> > We're looking into a twin and the Twin Comanche is on our list. I know
> > that the later models have the counter rotating props -- although i
> > don't know too much about what this means, other than its "better".
> >
> > We fly a mooney now and thus I don't worry about the prop -- as long as
> > it keeps spinning.
> >
> > Is there a web site that gives a good explanation as to why I want CR
> > props. There are hundreds of the earlier model Twin Comanches flying
> > without the CR props --- so what does someone with 300 hours single
> > engine time need to worry about? What actually goes wrong? And when
> > it does, what happens? I hear "critical engine" but it means very
> > little to me.
> >
> > I like to fly and try to be very careful when I do fly... but I don't
> > follow too much aviation stuff other than how it affects me -- so I'm
> > not exactly a "buff", hence the above questions which may seem obvious
> > to many.
> >
> > Why are we looking at a Twin Comanche? Because its a twin, safer for
> > IFR flight (perhaps this is only preceived), plus we live on the east
> > coast on an island so we're flying over water quite a bit. Also this
> > plane has decent speed and is an "economical" twin. We rarely fly with
> > 4 people, so we don't need any more seats than 4.
> >
> > Any help or links to help would be appreciated.
> >
> > Thanks,
> >
> > Dico
> >
>
>

[Michael]

> You only left out one part: when a pilot does learn to fly the
> PA30 and stay ahead of it, it's a blast to fly!! (especially the turbo'd
> model)

You're right - I left that out. I figured that part was obvious :)

Seriously - the plane had some rough edges, but nothing touches it for
comfort and efficiency in twins, and it is a blast to fly once you get
out in front of it. The turbo is OK, but the premier one is the Miller
Mod with IO-360's. Now THAT is a machine.

Michael

[Robert M. Gary]

What's the deal with counter-rotating props? I mean they're props,
don't they all rotate? And what's up with this counter stuff. Who's
counting, why is everyong always trying to count everything.

(Sorry, couldn't help but hear Jerry Senfield in there somewhere).

-Robert

[Henry A. Spellman]

One thing that hasn't been mentioned in this thread is the tremendous
amount of pure BS that is published and retold as the truth concerning
both single and twin Comanches. Flight instructors check out new
Comanche pilots without having a clue as to what they are doing.
Mechanics work on Comanches and just make things worse.

Two tales concerning the landing gear illustrate the point. Perhaps you
recall the pictures of the Comanche landing gear up (in California, I
think). The newsies called it a Cherokee, but it really was a Comanche.
Anyway, a flight instructor was checking out a new Comanche pilot.
The gear failed to extend, so they went to the emergency gear extension
option. They removed the floor plate to access the release lever and
proceeded to pump the gear down for the next hour, but could never get
it to lock. Finally they landed gear up. The problem? The Comanche
gear has no hydraulics to pump down! It is all electrical and
mechanical. You simply push the lever all the way forward, and leave it
there (like the manual gear in the early Mooneys)! Of course, neither
pilot bothered to read the emergency extension procedure which was
written on the back of the access plate they removed as the first step.

The second tale concerns a Comanche pilot whose plane developed a
hesitation in retraction after gear up was selected. So he went to his
mechanic and described the symptoms. The mechanic thought a minute and
then opined that it was probably a problem with the hydraulic power pac.
There still aren't any hydraulics in the Comanche landing gear.

The International Comanche Society and the Comanche Flyer Foundation
have spent a bunch of money providing Comanche specific training for
flight instructors. Use them. While it is very important for a single
Comanche, it is vital for a twin. ICS can tell you who and where they
are. Similarly, find an experienced Comanche mechanic. It will save
you money in the long run.

Hank
Henry A. Spellman
Comanche N5903P

Dico wrote:
> Hello,
>
> We're looking into a twin and the Twin Comanche is on our list. I know
> that the later models have the counter rotating props -- although i
> don't know too much about what this means, other than its "better".
>
> We fly a mooney now and thus I don't worry about the prop -- as long as
> it keeps spinning.
>
> Is there a web site that gives a good explanation as to why I want CR
> props. There are hundreds of the earlier model Twin Comanches flying
> without the CR props --- so what does someone with 300 hours single
> engine time need to worry about? What actually goes wrong? And when
> it does, what happens? I hear "critical engine" but it means very
> little to me.
>
> I like to fly and try to be very careful when I do fly... but I don't
> follow too much aviation stuff other than how it affects me -- so I'm
> not exactly a "buff", hence the above questions which may seem obvious
> to many.
>
> Why are we looking at a Twin Comanche? Because its a twin, safer for
> IFR flight (perhaps this is only preceived), plus we live on the east
> coast on an island so we're flying over water quite a bit. Also this
> plane has decent speed and is an "economical" twin. We rarely fly with
> 4 people, so we don't need any more seats than 4.
>
> Any help or links to help would be appreciated.
>
> Thanks,
>
> Dico
>

[Rob McDonald]

Thanks Jim

"Jim Burns" > wrote in
:

> One of my favorites is Bob Gardner's book The Complete Multi-Engine
> Pilot. It's written in a very easy to read down to earth manner. The
> Jeppesen Guided Flight Discovery, Multi Engine book is very complete,
> but in my opinion hard to read due to the distracting pictures and
> captions. Jim
>
>
> Rob McDonald" > wrote in message
> ...
>> What would you multi folks recommend as good "introductory" reading...

[Rob McDonald]

I suspect that our perception of the dangers are skewed by the fact that
the failures (i.e. "second engine took them to the crash site") are
reported in both the official records and the media, but we are less likely
to hear about successful outcomes like yours.

Rob


"Michael" > wrote in
oups.com:

> ...
>> The second engine, on failure of the first engine, will only lead you
>> to a landing location, not necessarily of your choosing.
>
> My experience differs. When the left (critical) engine of my Twin
> Comanche failed (due to undetectable corrosion in the fuel servo) the
> remaining engine took me to a normal landing at an airport. Had I
> been in a single engine plane in the same situation, well, let's just
> say I was over Arkansas and there was an avtive airmet for mountain
> obscuration.
>
> Michael
>

[Rob McDonald]

On the other hand, out here (central Ontario) most of the real estate does
not much exceed 1000' ASL. I have the Great Lakes on three sides and most
of the territory I fly over when going any distance is trees, rocks, and
small lakes - no emergency land sites, just crash sites. Even the 3800' SE
ceiling of the Twinkie with the Robertson STOL kit would be enough to
prevent an engine failure from ruining my day.

Rob


"BTIZ" > wrote in
news:auyDf.54832$V.15854@fed1read04:
>
> Out here, most airports are around 3000MSL, with terrain over 8000MSL
> between them, add in the density altitude factor on a standard 100F or
> higher day.. and that single engine is not going to be me to an
> airport. BT
>
>

[Private]

"Dico" > wrote in message
oups.com...
> Is there a web site that gives a good explanation as to why I want CR
> props. There are hundreds of the earlier model Twin Comanches flying
> without the CR props --- so what does someone with 300 hours single
> engine time need to worry about? What actually goes wrong? And when
> it does, what happens? I hear "critical engine" but it means very
> little to me.
>

I would like to throw an interesting (if maybe false? I have no personal
experience or a cite.) factoid into this discussion.

I have read that the P38 Lightning was equipped with counter rotating props
that rotated in the opposite (down going blades on outboard side of engines)
from normal direction resulting in an aircraft with two critical engines and
much increased yaw force when either engine failed. This was done despite
control issues because it resulted in 15 knots extra top speed as compared
with CR props using typical configuration (down going blade on inboard side
of engines)

Someone more knowledgeable may be able to explain why.

[[email protected]]

Private > wrote:
: I would like to throw an interesting (if maybe false? I have no personal
: experience or a cite.) factoid into this discussion.

: I have read that the P38 Lightning was equipped with counter rotating props
: that rotated in the opposite (down going blades on outboard side of engines)
: from normal direction resulting in an aircraft with two critical engines and
: much increased yaw force when either engine failed. This was done despite
: control issues because it resulted in 15 knots extra top speed as compared
: with CR props using typical configuration (down going blade on inboard side
: of engines)

: Someone more knowledgeable may be able to explain why.

Interesting. Perhaps less downward propwash on outboard ends of wings? Or
maybe propwash vorticies "lifting" the fuselage rather than "swatting it down?"

Just WAGs on my part.

-Cory


--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

[Michael]

Private wrote:
> I have read that the P38 Lightning was equipped with counter rotating props
> that rotated in the opposite (down going blades on outboard side of engines)
> from normal direction resulting in an aircraft with two critical engines and
> much increased yaw force when either engine failed.

This is definitely true, in the sense that the props did counter-rotate
opposite to what is now normal. However, the whole critical engine
thing is way overrated. Vmc is a control speed, not a performance
speed. It is quite a bit lower than Vyse, which is as slow as you ever
want to fly with anything close to full power (other than in a training
situation) whether you have an engine out or not. In other words, it's
really not a big deal, which is why it's rare to see counter-rotating
props in anything other than a trainer.

> This was done despite
> control issues because it resulted in 15 knots extra top speed as compared
> with CR props using typical configuration (down going blade on inboard side
> of engines)

That doesn't sound right. My understanding is that the reason was to
make the plane more maneuverable (using differential thrust for yaw).
Of course you could get the same effect by using a bigger rudder, but
that would mean more weight and drag, so maybe it boils down to the
same thing - a cleaner, lighter, and thus faster airframe with the same
maneuverability.

It is also my understanding that the extra maneuverability was rarely
used due to the complexity of engine management involved. Late in the
game, a prototype was built with single-lever engine controls. Richard
Bong, one of the most famous of the WWII aces, died test flying it when
an engine blew up.

Michael

[JJS]

"Michael" > wrote in message
oups.com...
snip
> Late in the game, a prototype was built with single-lever engine controls. Richard
> Bong, one of the most famous of the WWII aces, died test flying it when
> an engine blew up.
>
> Michael

I thought he died in one of the first jets... perhaps a P-80?

Joe Schneider
8437R



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[Matt Barrow]

"JJS" <jschneider@remove socks cebridge.net> wrote in message
...
>
> "Michael" > wrote in message
> oups.com...
> snip
>> Late in the game, a prototype was built with single-lever engine
>> controls. Richard
>> Bong, one of the most famous of the WWII aces, died test flying it when
>> an engine blew up.
>>
>> Michael
>
> I thought he died in one of the first jets... perhaps a P-80?
>
Correct.

Fuel Pump failure (IIRC) which he did not know how to handle as he was too
much the "hot shot" pilot to read the operating manual.

Interestingly...both Bong and McConnell, the highest scoring aces in WW2 and
Korea, both died right at the respective wars end while test flying, both in
low altitude accidents.

[Michael]

> I suspect that our perception of the dangers are skewed by the fact that
> the failures (i.e. "second engine took them to the crash site") are
> reported in both the official records and the media, but we are less likely
> to hear about successful outcomes like yours.

Yes, that's part of it. My engine failure was under IFR, but while I
reported it to ATC, that was as far as it went. I requested priority
handling (not wanting to descend low over trees until I was closer to
the airport) but that was as far as it went. After a throrough
cleaning and flush of the fuel servo, I was back in action. There was
no accident or incident.

Engine failures do not figure heavily in the accident stats, but I've
noticed that this is because single engine pilots are noticeably more
conservative about flying in situations where an engine failure is
likely to kill you. I think nothing of making an overwater flight
dozens of miles from land, or a flight over rough terrain with
widespread low IFR. I do it routinely in the twin. I will do it in a
single, but only if I really need to make the flight.

Michael