Today's Message Index:
----------------------
1. 11:03 AM - Re: Aerobatics with FP prop (rv6capt@pacificcoast.net)
2. 02:39 PM - Re: Aerobatics with FP prop (Robert Lake)
3. 03:44 PM - SEC: UNCLASSIFIED Re: Aerobatics with FP prop (Francis, David CMDR)
4. 04:28 PM - Re: UNCLASSIFIED Re: Aerobatics with FP prop (sjevans)
5. 06:05 PM - Re: UNCLASSIFIED Re: Aerobatics with FP prop (cary rhodes)
6. 10:28 PM - SEC: UNCLASSIFIED Re: Aerobatics with FP prop (Francis, David CMDR)
7. 10:53 PM - Re: UNCLASSIFIED Re: Aerobatics with FP prop (Dan Checkoway)
8. 11:39 PM - SEC: UNCLASSIFIED Re: Aerobatics with FP prop (Francis, David CMDR)
Message 1
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| Subject: | Re: Aerobatics with FP prop |
--> RV7-List message posted by: rv6capt@pacificcoast.net
I do all the aerobatics metioned in Vans construction manual with no problems
with the fixed pitch prop, including 1 1/4 to 1 1/2 rotations in a vertical
climb.
Quoting Allen Fulmer <afulmer@charter.net>:
> --> RV7-List message posted by: "Allen Fulmer" <afulmer@charter.net>
>
> I am trying to decide the Fixed Pitch/Constant Speed Prop question. Lots of
> interesting opinions/experiences on the list lately. One thing I have not
> seen mentioned is whether the mild, positive G aerobatics I want to be able
> to do can be done as well with a FP prop as with a CS?
>
> Opinions/experience?
>
> Thanks,
>
> Allen Fulmer
> RV7 Wings
> N808AF reserved
>
>
>
>
>
>
Message 2
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| Subject: | Re: Aerobatics with FP prop |
--> RV7-List message posted by: Robert Lake <oai@direcway.com>
Gentlemen:
I am in the middle of a RV-7 and have decided on a fixed pitch prop.
It's a cost factor. I've got an IO-360 A1A. A C/S prop is $5,000....and
the governor cost....and the costs every year for the additional inspections
during the annual........
Anyway, Van's told me that the cruise speed will be just about the same
with a fixed pitch and I will only give up about 200 feet with the take-off
roll.
Bob Lake
Austin, Tx
----- Original Message -----
From: "Allen Fulmer" <afulmer@charter.net>
Subject: RV7-List: Aerobatics with FP prop
> --> RV7-List message posted by: "Allen Fulmer" <afulmer@charter.net>
>
> I am trying to decide the Fixed Pitch/Constant Speed Prop question. Lots
of
> interesting opinions/experiences on the list lately. One thing I have not
> seen mentioned is whether the mild, positive G aerobatics I want to be
able
> to do can be done as well with a FP prop as with a CS?
>
> Opinions/experience?
>
> Thanks,
>
> Allen Fulmer
> RV7 Wings
> N808AF reserved
>
>
Message 3
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| Subject: | Aerobatics with FP prop |
--> RV7-List message posted by: "Francis, David CMDR" <David.Francis@defence.gov.au>
Allen,
Aeros with a fixed pitch prop can be done. The main impact of a CS prop is
lower workload for the pilot and kinder treatment to the engine. The
governor ensures that the engine is neither oversped nor overtorqued during
aeros. With FP the pilot becomes the governor.
Personnally I would not pay the huge price premium just to get lower
workload aerobatics. The large price premium for a CS prop buys versatility.
The compromise involved with a FP prop is removed at a price and weight
premium. What you get is shorter takeoff, better climb, and same cruise
speed (compared to a cruise FP prop). Additionally, if you also have fuel
injection and an engine analyser a CS prop means you can more accurately
optimise the MAP/rpm? mixture to run lean of peak and get very good miles
per gallon in the cruise.
Generally (with many exceptions) engine cofigurations fall into two opposite
camps:
a. low cost high fuel consumption - carburettor, magnetos, fixed pitch,
simple instruments, or
b. high cost, low fuel consumption - injected, electronic ignition, constant
speed, engine analyzer.
Combinations in between tend to be inefficient comromises.
Regards,
David Francis, Canberra Australia, RV7, airframe complete, ordering the
engine.
Subject: Re: RV7-List: Aerobatics with FP prop
--> RV7-List message posted by: rv6capt@pacificcoast.net
I do all the aerobatics metioned in Vans construction manual with no
problems
with the fixed pitch prop, including 1 1/4 to 1 1/2 rotations in a vertical
climb.
Quoting Allen Fulmer <afulmer@charter.net>:
> --> RV7-List message posted by: "Allen Fulmer" <afulmer@charter.net>
>
> I am trying to decide the Fixed Pitch/Constant Speed Prop question. Lots
of
> interesting opinions/experiences on the list lately. One thing I have not
> seen mentioned is whether the mild, positive G aerobatics I want to be
able
> to do can be done as well with a FP prop as with a CS?
>
> Opinions/experience?
>
> Thanks,
>
> Allen Fulmer
> RV7 Wings
> N808AF reserved
>
>
>
>
>
>
Message 4
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| Subject: | Aerobatics with FP prop |
--> RV7-List message posted by: "sjevans" <sjevans@cox.net>
David,
My plan at this time is a 360 engine with a FP prop. I am planning to
use electronic ignition on one side to help smooth-out the engine &
improve performance. Are you saying this combination is an "inefficient
compromise"?
I'm sort of new at this, so if there is something I'm missing, please
let me know. I sure don't want to spend extra bucks if I'm not going to
realize any benefit.
Thanks,
Sam Evans
Working on wings
N350SE, reserved
-----Original Message-----
From: owner-rv7-list-server@matronics.com
[mailto:owner-rv7-list-server@matronics.com] On Behalf Of Francis, David
CMDR
Subject: SEC: UNCLASSIFIED RE: RV7-List: Aerobatics with FP prop
--> RV7-List message posted by: "Francis, David CMDR"
<David.Francis@defence.gov.au>
Allen,
Aeros with a fixed pitch prop can be done. The main impact of a CS prop
is
lower workload for the pilot and kinder treatment to the engine. The
governor ensures that the engine is neither oversped nor overtorqued
during
aeros. With FP the pilot becomes the governor.
Personnally I would not pay the huge price premium just to get lower
workload aerobatics. The large price premium for a CS prop buys
versatility.
The compromise involved with a FP prop is removed at a price and weight
premium. What you get is shorter takeoff, better climb, and same cruise
speed (compared to a cruise FP prop). Additionally, if you also have
fuel
injection and an engine analyser a CS prop means you can more accurately
optimise the MAP/rpm? mixture to run lean of peak and get very good
miles
per gallon in the cruise.
Generally (with many exceptions) engine cofigurations fall into two
opposite
camps:
a. low cost high fuel consumption - carburettor, magnetos, fixed pitch,
simple instruments, or
b. high cost, low fuel consumption - injected, electronic ignition,
constant
speed, engine analyzer.
Combinations in between tend to be inefficient comromises.
Regards,
David Francis, Canberra Australia, RV7, airframe complete, ordering the
engine.
Subject: Re: RV7-List: Aerobatics with FP prop
--> RV7-List message posted by: rv6capt@pacificcoast.net
I do all the aerobatics metioned in Vans construction manual with no
problems
with the fixed pitch prop, including 1 1/4 to 1 1/2 rotations in a
vertical
climb.
Quoting Allen Fulmer <afulmer@charter.net>:
> --> RV7-List message posted by: "Allen Fulmer" <afulmer@charter.net>
>
> I am trying to decide the Fixed Pitch/Constant Speed Prop question.
Lots
of
> interesting opinions/experiences on the list lately. One thing I have
not
> seen mentioned is whether the mild, positive G aerobatics I want to be
able
> to do can be done as well with a FP prop as with a CS?
>
> Opinions/experience?
>
> Thanks,
>
> Allen Fulmer
> RV7 Wings
> N808AF reserved
>
>
>
>
>
>
==
==
==
==
Message 5
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| Subject: | Aerobatics with FP prop |
--> RV7-List message posted by: cary rhodes <rhodeseng@yahoo.com>
sam
don't back off on the electronic ign.
You will be sorry if u stick with the dual mags.
just my 2 cents
cary
--- sjevans <sjevans@cox.net> wrote:
> --> RV7-List message posted by: "sjevans"
> <sjevans@cox.net>
>
> David,
> My plan at this time is a 360 engine with a FP
> prop. I am planning to
> use electronic ignition on one side to help
> smooth-out the engine &
> improve performance. Are you saying this
> combination is an "inefficient
> compromise"?
> I'm sort of new at this, so if there is something
> I'm missing, please
> let me know. I sure don't want to spend extra bucks
> if I'm not going to
> realize any benefit.
> Thanks,
> Sam Evans
> Working on wings
> N350SE, reserved
>
> -----Original Message-----
> From: owner-rv7-list-server@matronics.com
> [mailto:owner-rv7-list-server@matronics.com] On
> Behalf Of Francis, David
> CMDR
> To: 'rv7-list@matronics.com'
> Subject: SEC: UNCLASSIFIED RE: RV7-List: Aerobatics
> with FP prop
>
> --> RV7-List message posted by: "Francis, David
> CMDR"
> <David.Francis@defence.gov.au>
>
>
> Allen,
> Aeros with a fixed pitch prop can be done. The main
> impact of a CS prop
> is
> lower workload for the pilot and kinder treatment to
> the engine. The
> governor ensures that the engine is neither oversped
> nor overtorqued
> during
> aeros. With FP the pilot becomes the governor.
>
> Personnally I would not pay the huge price premium
> just to get lower
> workload aerobatics. The large price premium for a
> CS prop buys
> versatility.
> The compromise involved with a FP prop is removed at
> a price and weight
> premium. What you get is shorter takeoff, better
> climb, and same cruise
> speed (compared to a cruise FP prop). Additionally,
> if you also have
> fuel
> injection and an engine analyser a CS prop means you
> can more accurately
> optimise the MAP/rpm? mixture to run lean of peak
> and get very good
> miles
> per gallon in the cruise.
>
> Generally (with many exceptions) engine
> cofigurations fall into two
> opposite
> camps:
> a. low cost high fuel consumption - carburettor,
> magnetos, fixed pitch,
> simple instruments, or
> b. high cost, low fuel consumption - injected,
> electronic ignition,
> constant
> speed, engine analyzer.
>
> Combinations in between tend to be inefficient
> comromises.
>
> Regards,
> David Francis, Canberra Australia, RV7, airframe
> complete, ordering the
> engine.
>
>
> Subject: Re: RV7-List: Aerobatics with FP prop
>
>
> --> RV7-List message posted by:
> rv6capt@pacificcoast.net
>
> I do all the aerobatics metioned in Vans
> construction manual with no
> problems
> with the fixed pitch prop, including 1 1/4 to 1 1/2
> rotations in a
> vertical
> climb.
>
> Quoting Allen Fulmer <afulmer@charter.net>:
>
> > --> RV7-List message posted by: "Allen Fulmer"
> <afulmer@charter.net>
> >
> > I am trying to decide the Fixed Pitch/Constant
> Speed Prop question.
> Lots
> of
> > interesting opinions/experiences on the list
> lately. One thing I have
> not
> > seen mentioned is whether the mild, positive G
> aerobatics I want to be
> able
> > to do can be done as well with a FP prop as with a
> CS?
> >
> > Opinions/experience?
> >
> > Thanks,
> >
> > Allen Fulmer
> > RV7 Wings
> > N808AF reserved
> >
> >
> >
> >
> >
> >
>
>
> ==
> ==
> ==
> ==
>
>
>
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> any other
> Forums.
>
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Message 6
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| Subject: | Aerobatics with FP prop |
--> RV7-List message posted by: "Francis, David CMDR" <David.Francis@defence.gov.au>
Sam,
The answer depends on your choice of fuel delivery system. I shall explain.
Starting point - a carburetted engine must cruise rich of peak, where fuel
is used to cool the interior of the cylinder. Fuel injection has better fuel
delivery to cylinders, and it is therefore possible to cruise lean of peak
where air is used to cool the inside of a cylinder. Major fuel savings in
the cruise are possible.
A magneto delivers spark at fixed timing of 25 degrees BTDC. The engineers
chose 25BTDC because it provides adequate performance at full power, and is
optimum for rich of peak cruise at around 2400rpm. These are conditions
typical for a carburetted engine.
Now electronic ignition provides three benefits - variable timing, a hotter
spark, and a longer duration spark.
Electronic ignition on a carburetted engine will self-select 15BTDC in the
cruise - because it is the optimum. So apart from easier starting and a
slight advantage from a hotter & longer spark, its performing the same as a
much cheaper magneto. Not a good choice.
Now if you have electronic ignition on a fuel injected engine, and you
choose to cruise lean of peak, then the flame front slows down. The ignition
will compensate and optimise timing by advancing it to maybe 40BTDC. This
generates major improvements in miles per gallon. You will fly a little
slower, with a big improvement in mpg. Electronic ignition plus fuel
injection should definitely pay for themselves in fuel savings, and more.
Improvements in fuel efficiency compared to rich of peak in the range of
15%-25% are possible.
A CS prop can add a little more to fuel efficiency by allowing wide open
throttle and oversquare operations and also operations above 10,000 ft as
follows.
The optimum cruise altitude for a normally aspirated plane is in the region
8000-9500 depending on seasonal temperature. The peak torque in an 0360 from
Aerosport occurs at 2300rpm. So the optimum cruise is 8000 or so ft, wide
open throttle, 2300 rpm, lean of peak. With FP prop hitting this combination
is a hit or miss affair, but not with a CS prop. Also to go above 10,000 to
take advantage of drag reduction/improved TAS you need to restore lost
engine power by selecting a higher rpm - 2450 for instance, which is
unavailable in a FP installation. That is how Jon Johanson gets
extraordinarily good fuel efficiency on his long range flights. Need oxy of
course.
To confirm this short story read:
for running lean of peak, the Pelicans Perch articles by John Deakin on
Avweb, and also see the GAMI site.
for electronic ignition the research papers on the CAFE site.
for a good knowledge of your 0360 the Skyranch Engineering Manual.
Have fun, David Francis, Canberra, Australia.
--> RV7-List message posted by: "sjevans" <sjevans@cox.net>
David,
My plan at this time is a 360 engine with a FP prop. I am planning to
use electronic ignition on one side to help smooth-out the engine &
improve performance. Are you saying this combination is an "inefficient
compromise"?
I'm sort of new at this, so if there is something I'm missing, please
let me know. I sure don't want to spend extra bucks if I'm not going to
realize any benefit.
Thanks,
Sam Evans
Working on wings
N350SE, reserved
Message 7
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| Subject: | Re: Aerobatics with FP prop |
--> RV7-List message posted by: "Dan Checkoway" <dan@rvproject.com>
> Starting point - a carburetted engine must cruise rich of peak, where fuel
> is used to cool the interior of the cylinder. Fuel injection has better
fuel
> delivery to cylinders, and it is therefore possible to cruise lean of peak
> where air is used to cool the inside of a cylinder. Major fuel savings in
> the cruise are possible.
Possible...only if you have the appropriate equipment. Specifically,
balanced injectors. LOP operation isn't something that any old fuel
injected engine should be subjected to. Probably what you meant, but I
wanted to clarify for the record. 8-)
)_( Dan
RV-7 N714D
http://www.rvproject.com
Message 8
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| Subject: | Aerobatics with FP prop |
--> RV7-List message posted by: "Francis, David CMDR" <David.Francis@defence.gov.au>
Dan,
You are correct, the injectors need to be balanced. Additionally, in the
interest of keeping a long story short, I did not mention the need for good
instrumentation to support LOP - as a minimum you need EGT and EGT for all
cylinders, and an accurate fuel flow meter is highly recommended too.
Regards, David Francis, Canberra, Australia, in the middle of a dry, cold
windy winter.
--> RV7-List message posted by: "Dan Checkoway" <dan@rvproject.com>
> Starting point - a carburetted engine must cruise rich of peak, where fuel
> is used to cool the interior of the cylinder. Fuel injection has better
fuel
> delivery to cylinders, and it is therefore possible to cruise lean of peak
> where air is used to cool the inside of a cylinder. Major fuel savings in
> the cruise are possible.
Possible...only if you have the appropriate equipment. Specifically,
balanced injectors. LOP operation isn't something that any old fuel
injected engine should be subjected to. Probably what you meant, but I
wanted to clarify for the record. 8-)
)_( Dan
RV-7 N714D
http://www.rvproject.com
_-
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