Green Arc Red Zone

[john smith]

Jack Allison's discussion of the Hartzell AD for his Arrow has gotten me
to thinking.
What aircraft do you fly/have you flown/do you have first hand knowledge
of which have a red zone somewhere in the green arc of the tachometer?

For example, I know there are/were certain models of Cessna 210's that
had such markings, but I cannot remember the specific models/engine/prop
combinations.

[Jose[_1_]]

> Jack Allison's discussion of the Hartzell AD for his Arrow has gotten me to thinking.
> What aircraft do you fly/have you flown/do you have first hand knowledge of which have a red zone somewhere in the green arc of the tachometer?

There was one aircraft I flew (C172? Arrow?) which had a placard to
avoid operations between (I think) 2000 and 2200, or something like
that. It was not marked as a red zone on the tach though.

Jose
--
He who laughs, lasts.
for Email, make the obvious change in the address.

[Roy Smith]

john smith > wrote:
> Jack Allison's discussion of the Hartzell AD for his Arrow has gotten me
> to thinking.
> What aircraft do you fly/have you flown/do you have first hand knowledge
> of which have a red zone somewhere in the green arc of the tachometer?

My club used to have an Arrow-II which had a red arc from (IIRC 2150 - 2300
RPM). Green above and below that. The POH listed only two allowable
cruise RPMs: 2100 or 2400, nothing in between.

I may be off a little on the actual numeric values.

[Jim Macklin]

Several reasons for a restricted RPM, due to harmonic
vibration...some say not to have prolonged operation in
certain RPM ranges, some have a red range in the green arc.
I think Lycomng has a FAQ on their engines.


"Roy Smith" > wrote in message
...
| john smith > wrote:
| > Jack Allison's discussion of the Hartzell AD for his
Arrow has gotten me
| > to thinking.
| > What aircraft do you fly/have you flown/do you have
first hand knowledge
| > of which have a red zone somewhere in the green arc of
the tachometer?
|
| My club used to have an Arrow-II which had a red arc from
(IIRC 2150 - 2300
| RPM). Green above and below that. The POH listed only
two allowable
| cruise RPMs: 2100 or 2400, nothing in between.
|
| I may be off a little on the actual numeric values.

[BT]

C-177B models also had a red zone range
you could feel the vibration in the floor if you were in the "red zone",
neat trick for instructors..
Instructor to student: "you feel that vibration"
Student: "yes"...
Instructor: "Then do something about it"
Student: "What should I do? I'm not flying to fast.."
Instructor: "You think maybe the engine or prop are trying to tell you
something?"
Student: "Oh yah.. That red arc"

BT

"john smith" > wrote in message
...
> Jack Allison's discussion of the Hartzell AD for his Arrow has gotten me
> to thinking.
> What aircraft do you fly/have you flown/do you have first hand knowledge
> of which have a red zone somewhere in the green arc of the tachometer?
>
> For example, I know there are/were certain models of Cessna 210's that had
> such markings, but I cannot remember the specific models/engine/prop
> combinations.
>
>

[BT]

"john smith" > wrote in message
...
> Jack Allison's discussion of the Hartzell AD for his Arrow has gotten me
> to thinking.
> What aircraft do you fly/have you flown/do you have first hand knowledge
> of which have a red zone somewhere in the green arc of the tachometer?
>
> For example, I know there are/were certain models of Cessna 210's that had
> such markings, but I cannot remember the specific models/engine/prop
> combinations.
>
>

[Mortimer Schnerd, RN[_2_]]

Jose wrote:
> There was one aircraft I flew (C172? Arrow?) which had a placard to
> avoid operations between (I think) 2000 and 2200, or something like
> that. It was not marked as a red zone on the tach though.



I'll bet it was the Arrow. I recall seeing the same sort of placard but nothing
on the tach, either.



--
Mortimer Schnerd, RN
mschnerdatcarolina.rr.com

[Dudley Henriques]

"Jim Macklin" > wrote in message
...
> Several reasons for a restricted RPM, due to harmonic
> vibration...some say not to have prolonged operation in
> certain RPM ranges, some have a red range in the green arc.
> I think Lycomng has a FAQ on their engines.

The Lockheed Electra sure could have used a prop AD for this one!
Dudley Henriques


>
>
> "Roy Smith" > wrote in message
> ...
> | john smith > wrote:
> | > Jack Allison's discussion of the Hartzell AD for his
> Arrow has gotten me
> | > to thinking.
> | > What aircraft do you fly/have you flown/do you have
> first hand knowledge
> | > of which have a red zone somewhere in the green arc of
> the tachometer?
> |
> | My club used to have an Arrow-II which had a red arc from
> (IIRC 2150 - 2300
> | RPM). Green above and below that. The POH listed only
> two allowable
> | cruise RPMs: 2100 or 2400, nothing in between.
> |
> | I may be off a little on the actual numeric values.
>
>

[Morgans[_5_]]

"Dudley Henriques" > wrote

> The Lockheed Electra sure could have used a prop AD for this one!

So there was a RPM restriction on the Electra?

What do you recall? Didn't a constant speed prop pretty much bypass it?
--
Jim in NC

[Dudley Henriques]

"Morgans" > wrote in message
...
>
> "Dudley Henriques" > wrote
>
>> The Lockheed Electra sure could have used a prop AD for this one!
>
> So there was a RPM restriction on the Electra?
>
> What do you recall? Didn't a constant speed prop pretty much bypass it?
> --
> Jim in NC

I only have a vague recall on this. It came up during a safety meeting at
the Naval Test Pilots School many years ago.
If I remember right, it involved a harmonic mode (whirl I believe) not
transmitting correctly through the outboard engine mounts on the airplane.
They specified certain conditions that caused this to happen but I don't
remember what they were. I seem to recall that after the issue was addressed
by Lockheed and the mounts were redesigned, there was a further wing issue
as well that had to be dealt with.
I think Macklin will probably be the guy who can best deal with exactly what
was going on.
Dudley Henriques

[BT]

it is constant speed props on the Arrow and Cardinal..
and there is still a harmonic vibration range

BT

"Morgans" > wrote in message
...
>
> "Dudley Henriques" > wrote
>
>> The Lockheed Electra sure could have used a prop AD for this one!
>
> So there was a RPM restriction on the Electra?
>
> What do you recall? Didn't a constant speed prop pretty much bypass it?
> --
> Jim in NC
>

[Morgans[_5_]]

"Dudley Henriques" > wrote

> I only have a vague recall on this. It came up during a safety meeting at
> the Naval Test Pilots School many years ago.
> If I remember right, it involved a harmonic mode (whirl I believe) not
> transmitting correctly through the outboard engine mounts on the airplane.
> They specified certain conditions that caused this to happen but I don't
> remember what they were. I seem to recall that after the issue was
> addressed by Lockheed and the mounts were redesigned, there was a further
> wing issue as well that had to be dealt with.


Yeah, I remember that coming up once before, now that the whirl mode is
mentioned. I don't recall the details, either.
--
Jim in NC

[Jim Macklin]

Thanks, but I'm not really an expert on the Electra. But I
also read that they harmonic was such that a whirl-mode
began [as you also said] and this caused several complete
airframe failures.

The NTSB probably has a file.


"Dudley Henriques" > wrote in message
...
|
| "Morgans" > wrote in message
| ...
| >
| > "Dudley Henriques" > wrote
| >
| >> The Lockheed Electra sure could have used a prop AD for
this one!
| >
| > So there was a RPM restriction on the Electra?
| >
| > What do you recall? Didn't a constant speed prop pretty
much bypass it?
| > --
| > Jim in NC
|
| I only have a vague recall on this. It came up during a
safety meeting at
| the Naval Test Pilots School many years ago.
| If I remember right, it involved a harmonic mode (whirl I
believe) not
| transmitting correctly through the outboard engine mounts
on the airplane.
| They specified certain conditions that caused this to
happen but I don't
| remember what they were. I seem to recall that after the
issue was addressed
| by Lockheed and the mounts were redesigned, there was a
further wing issue
| as well that had to be dealt with.
| I think Macklin will probably be the guy who can best deal
with exactly what
| was going on.
| Dudley Henriques
|
|

[Jim Macklin]

Google found this
http://www.cs.clemson.edu/~steve/Spiro/electra1.html


"Dudley Henriques" > wrote in message
...
|
| "Morgans" > wrote in message
| ...
| >
| > "Dudley Henriques" > wrote
| >
| >> The Lockheed Electra sure could have used a prop AD for
this one!
| >
| > So there was a RPM restriction on the Electra?
| >
| > What do you recall? Didn't a constant speed prop pretty
much bypass it?
| > --
| > Jim in NC
|
| I only have a vague recall on this. It came up during a
safety meeting at
| the Naval Test Pilots School many years ago.
| If I remember right, it involved a harmonic mode (whirl I
believe) not
| transmitting correctly through the outboard engine mounts
on the airplane.
| They specified certain conditions that caused this to
happen but I don't
| remember what they were. I seem to recall that after the
issue was addressed
| by Lockheed and the mounts were redesigned, there was a
further wing issue
| as well that had to be dealt with.
| I think Macklin will probably be the guy who can best deal
with exactly what
| was going on.
| Dudley Henriques
|
|

[Morgans[_5_]]

> Google found this
> http://www.cs.clemson.edu/~steve/Spiro/electra1.html

And here is part 2.
http://www.cs.clemson.edu/~steve/Spiro/electra2.html
--
Jim in NC

[Peter Dohm]

"Jim Macklin" > wrote in message
...
> Google found this
> http://www.cs.clemson.edu/~steve/Spiro/electra1.html

The second page of the above story is located at:
http://www.cs.clemson.edu/~steve/Spiro/electra2.html
(The link embedded at the end of the first page is obsolete)
Peter

>
>
> "Dudley Henriques" > wrote in message
> ...
> |
> | "Morgans" > wrote in message
> | ...
> | >
> | > "Dudley Henriques" > wrote
> | >
> | >> The Lockheed Electra sure could have used a prop AD for
> this one!
> | >
> | > So there was a RPM restriction on the Electra?
> | >
> | > What do you recall? Didn't a constant speed prop pretty
> much bypass it?
> | > --
> | > Jim in NC
> |
> | I only have a vague recall on this. It came up during a
> safety meeting at
> | the Naval Test Pilots School many years ago.
> | If I remember right, it involved a harmonic mode (whirl I
> believe) not
> | transmitting correctly through the outboard engine mounts
> on the airplane.
> | They specified certain conditions that caused this to
> happen but I don't
> | remember what they were. I seem to recall that after the
> issue was addressed
> | by Lockheed and the mounts were redesigned, there was a
> further wing issue
> | as well that had to be dealt with.
> | I think Macklin will probably be the guy who can best deal
> with exactly what
> | was going on.
> | Dudley Henriques
> |
> |
>
>

[Jim Macklin]

I saw part two is linked at the bottom of the page, so
didn't bother to put both there.
Didn't know the link was bad when I posted. Thanks.


What did you think of the article? It seems to be a an
aviation history students
paper.


"Morgans" > wrote in message
...
|> Google found this
| > http://www.cs.clemson.edu/~steve/Spiro/electra1.html
|
| And here is part 2.
| http://www.cs.clemson.edu/~steve/Spiro/electra2.html
| --
| Jim in NC
|
|

[Bob Moore]

Morgans wrote
> So there was a RPM restriction on the Electra?
> What do you recall? Didn't a constant speed prop pretty much bypass it?

The Electra (L-188) engine (Allison) always turned at 1061 RPM except at
ground idle. It had no Prop Control.

Bob Moore
ATP L-188
Combat Aircrew Commander P-3B

[Morgans[_5_]]

"Jim Macklin" > wrote in message
...
>I saw part two is linked at the bottom of the page, so
> didn't bother to put both there.
> Didn't know the link was bad when I posted. Thanks.
>
>
> What did you think of the article? It seems to be a an
> aviation history students
> paper.

Perhaps more like a journalist student who is interested in aviation. I
noticed the poetic license, and the big buzz words, like "tube of death."

Some technical items not quite right, but if this is a journalist, it is
better accident reporting, than most! <g>
--
Jim in NC

[Morgans[_5_]]

"Bob Moore" > wrote in message
46.128...
> Morgans wrote
>> So there was a RPM restriction on the Electra?
>> What do you recall? Didn't a constant speed prop pretty much bypass it?
>
> The Electra (L-188) engine (Allison) always turned at 1061 RPM except at
> ground idle. It had no Prop Control.

So, fixing the mounts and stiffening the wings was the only thing that was
changed; no different operating procedures?
--
Jim in NC

[Bob Moore]

Morgans wrote
> So, fixing the mounts and stiffening the wings was the only thing that
> was changed; no different operating procedures?

The "old" Electras that I flew at Air Florida did have a speed limit
imposed by the FAA. I have forgotten just what it was...34 years ago.

Bob Moore

[Scott Skylane]

Bob Moore wrote:

>
> The Electra (L-188) engine (Allison) always turned at 1061 RPM except at
> ground idle. It had no Prop Control.

C'mon Bob, I seriously doubt the *engine* ran at 1061 RPM! ;)

Happy Flying!
Scott Skylane

[Morgans[_5_]]

"Scott Skylane" > wrote in message
...
> Bob Moore wrote:
>
>>
>> The Electra (L-188) engine (Allison) always turned at 1061 RPM except at
>> ground idle. It had no Prop Control.
>
> C'mon Bob, I seriously doubt the *engine* ran at 1061 RPM! ;)
>
Why not? It is a turbine engine, after all.
--
Jim in NC

[Matt Whiting]

Morgans wrote:

> "Scott Skylane" > wrote in message
> ...
>
>>Bob Moore wrote:
>>
>>
>>>The Electra (L-188) engine (Allison) always turned at 1061 RPM except at
>>>ground idle. It had no Prop Control.
>>
>>C'mon Bob, I seriously doubt the *engine* ran at 1061 RPM! ;)
>>
>
> Why not? It is a turbine engine, after all.

That would make it even more surprising. That would be extremely slow
for a turbine. It isn't bad for a large piston engine, but still on the
slow side.


Matt

[Al G[_1_]]

"Scott Skylane" > wrote in message
...
> Bob Moore wrote:
>
>>
>> The Electra (L-188) engine (Allison) always turned at 1061 RPM except at
>> ground idle. It had no Prop Control.
>
> C'mon Bob, I seriously doubt the *engine* ran at 1061 RPM! ;)
>
> Happy Flying!
> Scott Skylane

Well, the output shaft & prop did. As I remember there was about an 11:1
reduction from the turbine.

Al G

VP-48 Crew 6 Moffat/Adak/Agana

[Morgans[_5_]]

"Matt Whiting" > wrote

>
> That would make it even more surprising. That would be extremely slow for
> a turbine. It isn't bad for a large piston engine, but still on the slow
> side.

Note to self: remove egg from face. <g>

I finally saw it. I was looking at it and sseing 10,610 RPM, or something
like that.

Perhaps that is prop speed, at 1,061 RPM ?
--
Jim in NC

[Matt Whiting]

Morgans wrote:
> "Matt Whiting" > wrote
>
>
>>That would make it even more surprising. That would be extremely slow for
>>a turbine. It isn't bad for a large piston engine, but still on the slow
>>side.
>
>
> Note to self: remove egg from face. <g>
>
> I finally saw it. I was looking at it and sseing 10,610 RPM, or something
> like that.
>
> Perhaps that is prop speed, at 1,061 RPM ?

That would make a lot of sense. 1,000 RPM for a large prop would be
plenty fast.

Matt

[Ross[_1_]]

john smith wrote:
> Jack Allison's discussion of the Hartzell AD for his Arrow has gotten me
> to thinking.
> What aircraft do you fly/have you flown/do you have first hand knowledge
> of which have a red zone somewhere in the green arc of the tachometer?
>
> For example, I know there are/were certain models of Cessna 210's that
> had such markings, but I cannot remember the specific models/engine/prop
> combinations.
>
>
I have a modified Cessna 172 with the Lycoming O-360-A1A engine and
Hartzel prop. I have a redline limitation between 2100 and 2250 rpm.
Really stinks.

--
Regards,

Ross
C-172F 180 hp
KSWI

[john smith]

Although there is red marking in the green arc, the POH for the 1979
Piper Turbo Arrow IV/PA28RT-201T, the LIMITATIONS SECTION lists the
following placards:

AVOID CONTINUOUS GROUND OPERATION 1700-2100 RPM IN CROSS/TAIL WIND OVER
10 KTS.

AVOID CONTINUOUS OPERATION 2000-2200 RPM ABOVE 32" MANIFOLD PRESSURE

I believe this applies to the two-bladed prop only and not the
three-bladed prop, but I can find nothing in the manual to support this
theory. I do not find the placards on the panel of the aircraft I fly
which has the three-bladed prop.

These two lines in the LIMITATIONS SECTION are the only place in the
POH which mention this condition.

[Bob Moore]

Morgans wrote
> Perhaps that is prop speed, at 1,061 RPM ?

Obviously.... :-)

Bob Moore

[john smith]

Should read: "Although there is no red marking..."

> Although there is red marking in the green arc, the POH for the 1979
> Piper Turbo Arrow IV/PA28RT-201T, the LIMITATIONS SECTION lists the
> following placards:
>
> AVOID CONTINUOUS GROUND OPERATION 1700-2100 RPM IN CROSS/TAIL WIND OVER
> 10 KTS.
>
> AVOID CONTINUOUS OPERATION 2000-2200 RPM ABOVE 32" MANIFOLD PRESSURE
>
> I believe this applies to the two-bladed prop only and not the
> three-bladed prop, but I can find nothing in the manual to support this
> theory. I do not find the placards on the panel of the aircraft I fly
> which has the three-bladed prop.
>
> These two lines in the LIMITATIONS SECTION are the only place in the
> POH which mention this condition.

[Jack Allison[_1_]]

john smith wrote:
> Jack Allison's discussion of the Hartzell AD for his Arrow has gotten me
> to thinking.
Wow...attribution and getting Mr. S to think. My work here is done :-)

> What aircraft do you fly/have you flown/do you have first hand knowledge
> of which have a red zone somewhere in the green arc of the tachometer?
Ours is a yellow arc that goes from...rats, I don't have it written down
anywhere. IIRC, the upper end of the yellow is 2300, maybe 2350. I'll
have to check tomorrow, make a note, and report back.

At any rate, it's really not much of a deal for our plane since,
basically, we use three prop settings:

1) Full forward for takeoff
2) 2500 rpm at 1000 AGL (and 25 inches MP)
3) 2400 rpm at cruise (and 21 inches MP...or, if you want to burn more
100ll for only a couple kt gain, go with 24 inches MP).


--
Jack Allison
PP-ASEL-Instrument Airplane

"To become a Jedi knight, you must master a single force. To become
a private pilot you must strive to master four of them"
- Rod Machado

(Remove the obvious from address to reply via e-mail)

[john smith]

Jack Allison wrote:

> john smith wrote:
>
>> Jack Allison's discussion of the Hartzell AD for his Arrow has gotten
>> me to thinking.
>
> Wow...attribution and getting Mr. S to think. My work here is done :-)

Should I respond to that?

Naw! I don't feed trolls. :-))

[JGalban[_1_]]

I don't think anyone mentioned the early Cherokee 180s. They have (or
should have) a red arc on the tach from 2150 to 2350 and a placard
stating that continuous operation should be avoided in that range.
The reason was harmonic vibrations developed between the Sensenich 76"
prop and the hollow cranked O-360-A3A. There were some prop tip
losses in the late 60s that prompted the restriction.

The restriction was removed in the '68 and later models, with the
introduction of the solid cranked O-360-A4A engine.

John Galban=====>N4BQ (PA28-180)


--
JGalban
Posted at www.flight.org

[Jack Allison[_1_]]

john smith wrote:
>>> Jack Allison's discussion of the Hartzell AD for his Arrow has gotten
>>> me to thinking.
>>
>> Wow...attribution and getting Mr. S to think. My work here is done :-)
>
> Should I respond to that?

Too late, you just did! :-)

> Naw! I don't feed trolls. :-))

Oh sure, break out the 'T' word. :-)


--
Jack Allison
PP-ASEL-Instrument Airplane

"To become a Jedi knight, you must master a single force. To become
a private pilot you must strive to master four of them"
- Rod Machado

(Remove the obvious from address to reply via e-mail)

[nrp]

Assuming a certain amount of artistic license, the reference article is
probably correct. I worked on another project with Prof Robt Scanlan
of Princeton Univ who was in charge of that Electra analysis.

As I recall he said that when an Electra was newly manufactured, the
whirl mode resonant frequency of the engine mount was about 5 Hz & the
flutter frequency of the wing was 3 Hz. After a period of service, the
engine mounts would crack (not that unusual in large aircraft) and
eventually the engine mount frequency would decay to the point that the
two frequencies would become so close that the engine motion would
couple into the wing flutter. Eventually the dynamic system became
divergent resulting in wing structural failure.

You must recognize however that the Electra whirl mode problem was and
is unrelated to the RPM restrictions with certain engine propeller
combinations. These restrictions address torsional resonance modes of
the propeller engine crankshaft combination - not whirl modes.

I understand the frequencies of concern are in the 220 Hz range (a
couple of half-steps below middle C on a piano) which is the sixth
harmonic of crankshaft rotation in a 4 cylinder engine. The resonant
mode shape is the back of the crank going to-and-fro while the prop
tips go fro-and-to assuming a theoretical observer riding on the
spinner (read that again carefully!). Changing the stiffness of the
crank (i, e, the solid core) changes the natural frequency of the
system enough to get it out of the operating harmonics range. Adding a
damper mass on the back of the crank is another way to reduce the
torsional vibration buildup and the resulting prop and crank stresses.


I could hear the 6th harmonic in my 172M at low cruise too even though
it was not placarded against it. There was a certain ringing harshness
in the noise, and any musical ear could recognize that component in the
cabin noise once it is pointed out. As a precaution I stayed away from
that RPM.

Frankly from my limited experience in vibration, I am surprised that
narrow a restriction is sufficient to prevent problems in the fleet.