Cruise RPM setting

[john]

Shortly after getting my private license I went to a different FBO and
got checked out in their aircrafts - C172 and Piper Cherokee.

I talked with the CFI and asked what RPM settings he would recommend.
I'm renting dry, so one way to reduce cost is to slow down and thus
save fuel. At the present time I'm just building hours towards my
commercial ticket. Rarely am I in a hurry to get anywhere. He
mentioned that if I needed to get somewhere quickly, to keep it around
2400. If I'm just building time then to reduce to 2300. It will save
fuel as well as reduce the sound level.

The CFI no longer flies out of that airport, so I don't have contact
with him. I'm interested in others opinions related to rpm settings.
Is there any harm to the engine with reducing the RPM even lower, say
2200 or even 2100 RPM. I will confess to bringing it back to as low
as 1800 for a short X-C and found it to be good slow flight practice.,
which gave my one leg a work out in order to keep the bubble in the
middle. I wouldn't want to make many flights at 1800 though.

In the 172 I have reduced fuel from over 7.5 gph at 2400rpm to about
5.5 gph at 2200-2300.

Thanks,

John

[Newps]

The best setting is whatever gives you the best miles per gallon. You
should find that at around 40% power. The more drag the airframe has
the less it will matter, you'll find yourself saving an extra tenth of a
mpg. Not worth the effort. The 182 I used to have would indicate 135
mph in the summer at 23" and 2450 rpm and 13 gph(10.4 mpg). At 20
squared(about 45%) it would indicate about 100 mph while burning about
9(11.1 mpg). My Bonanza indicates 190 mph at 23/2500 burning 14.5
gph(13.1 mpg). At 19/2100(also 45%) I indicate 160 mph, burning 8(20
mpg). Using true airspeeds would change these slightly but you get the
idea.

john wrote:

> Shortly after getting my private license I went to a different FBO and
> got checked out in their aircrafts - C172 and Piper Cherokee.
>
> I talked with the CFI and asked what RPM settings he would recommend.
> I'm renting dry, so one way to reduce cost is to slow down and thus
> save fuel. At the present time I'm just building hours towards my
> commercial ticket. Rarely am I in a hurry to get anywhere. He
> mentioned that if I needed to get somewhere quickly, to keep it around
> 2400. If I'm just building time then to reduce to 2300. It will save
> fuel as well as reduce the sound level.
>
> The CFI no longer flies out of that airport, so I don't have contact
> with him. I'm interested in others opinions related to rpm settings.
> Is there any harm to the engine with reducing the RPM even lower, say
> 2200 or even 2100 RPM. I will confess to bringing it back to as low
> as 1800 for a short X-C and found it to be good slow flight practice.,
> which gave my one leg a work out in order to keep the bubble in the
> middle. I wouldn't want to make many flights at 1800 though.
>
> In the 172 I have reduced fuel from over 7.5 gph at 2400rpm to about
> 5.5 gph at 2200-2300.
>
> Thanks,
>
> John
>

[Tina]

Since you're building time, why wouldn't you fly at the lowest fuel
consumption settings you're comfortable with that are consistant with
the POH?

You log calendar time for logbook purposes, and done correctly at low
RPM and well leaned you'll really cut back on fuel. In our Mooney,
which gets pulled around by an IO360, we often cruise at 1950 RPM --
allowed in the POH -- and fuel flow is in the 7 or 8 gph.

As an owner, we like low RPM as well, since that extends the real time
between overhaul -- tach hours assume 2400 RPM or so.


, On Oct 13, 11:16 pm, john > wrote:
> Shortly after getting my private license I went to a different FBO and
> got checked out in their aircrafts - C172 and Piper Cherokee.
>
> I talked with the CFI and asked what RPM settings he would recommend.
> I'm renting dry, so one way to reduce cost is to slow down and thus
> save fuel. At the present time I'm just building hours towards my
> commercial ticket. Rarely am I in a hurry to get anywhere. He
> mentioned that if I needed to get somewhere quickly, to keep it around
> 2400. If I'm just building time then to reduce to 2300. It will save
> fuel as well as reduce the sound level.
>
> The CFI no longer flies out of that airport, so I don't have contact
> with him. I'm interested in others opinions related to rpm settings.
> Is there any harm to the engine with reducing the RPM even lower, say
> 2200 or even 2100 RPM. I will confess to bringing it back to as low
> as 1800 for a short X-C and found it to be good slow flight practice.,
> which gave my one leg a work out in order to keep the bubble in the
> middle. I wouldn't want to make many flights at 1800 though.
>
> In the 172 I have reduced fuel from over 7.5 gph at 2400rpm to about
> 5.5 gph at 2200-2300.
>
> Thanks,
>
> John

[Morgans[_2_]]

"Newps" > wrote

> The best setting is whatever gives you the best miles per gallon. You
> should find that at around 40% power.

For just building time, MPG is not significant. He wants to stay in the air
for the least gas. For him, I think the old joke, " if that last engine
quits, we'll be up here all day" is probably the "best" he could do. <g>

I guess the best for him is the slowest speed that he can go, and not put up
with too much aggravation flying the plane. Whether or not that harms the
engine, I'll leave to others much more qualified than me.

P.S. Long taxi times help out, too! <g>
--
Jim in NC

[Mortimer Schnerd, RN[_2_]]

john wrote:
> The CFI no longer flies out of that airport, so I don't have contact
> with him. I'm interested in others opinions related to rpm settings.
> Is there any harm to the engine with reducing the RPM even lower, say
> 2200 or even 2100 RPM. I will confess to bringing it back to as low
> as 1800 for a short X-C and found it to be good slow flight practice.,
> which gave my one leg a work out in order to keep the bubble in the
> middle. I wouldn't want to make many flights at 1800 though.
>
> In the 172 I have reduced fuel from over 7.5 gph at 2400rpm to about
> 5.5 gph at 2200-2300.


The 1981 C-172P POH I just looked at listed 2100-2450 as the normal operating
range at sea level. The redline climbs with altitude to as much as 2700 rpm at
10,000 feet but it doesn't drop below 2100 on the lower end.

One thought about continued flight at 1800 rpm: if you were running with the
carb heat on to avoid icing, then you're ingesting unfiltered air. Best to keep
that at a minimum if you can.



--
Mortimer Schnerd, RN
mschnerdatcarolina.rr.com

[Thomas Borchert]

John,

> n the 172 I have reduced fuel from over 7.5 gph at 2400rpm to about
> 5.5 gph at 2200-2300.
>

First of all, the power settings in the POH mostly make a lot of sense.
Secondly, if you pay by Hobbs time, many people use what is referred to
as "rental cruise", aka full throttle full rich. You probably save
money by that, the rental outift probably won't.

Your objective of saving fuel and prolonging flight time is unusual for
a renter. Still, if I were to build time with a rental aircraft and
cost would be the same regardless of power settings, I would GO to
exciting new places at the fullest speed available rather than dawdling
around in the area I know. With respect to time building for a
commercial, that tactic would be immensely valuable since it would
expose you to new terrain, different weather and unknown fields. So,
again, if cost remains the same regardless of power setting, IMHO you
might want to rethink how you build time. I would even suggest a
multi-day cross country to an area of the country you always wanted to
go to.

As a general rule, I normally use the maximum recommended cruise power
setting from the POH, since I normally want to go somewhere. That's
mostly 75 percent. I use best economy mixture if I have a tail wind and
best power if I have a headwind. Also, I use as low an RPM setting as
possible for noise reduction, but I have a choice, since my airplane
has a constant speed prop.

--
Thomas Borchert (EDDH)

[kontiki]

Thomas Borchert wrote:

> Your objective of saving fuel and prolonging flight time is unusual for
> a renter. Still, if I were to build time with a rental aircraft and
> cost would be the same regardless of power settings, I would GO to
> exciting new places at the fullest speed available rather than dawdling
> around in the area I know. With respect to time building for a
> commercial, that tactic would be immensely valuable since it would
> expose you to new terrain, different weather and unknown fields. So,
> again, if cost remains the same regardless of power setting, IMHO you
> might want to rethink how you build time. I would even suggest a
> multi-day cross country to an area of the country you always wanted to
> go to.
>
> As a general rule, I normally use the maximum recommended cruise power
> setting from the POH, since I normally want to go somewhere. That's
> mostly 75 percent. I use best economy mixture if I have a tail wind and
> best power if I have a headwind. Also, I use as low an RPM setting as
> possible for noise reduction, but I have a choice, since my airplane
> has a constant speed prop.
>

I would say this is very good advice. I would much prefer to go
somehwere and visit new and different airports to gain experience
not just mindlessley logging time for your logbook. The goal of
the 250 hours for the commercial is for you to gain flying
experience and build skills.

A few nights ago I flew with a student in a 152 on a night
cross country and didn't get back till 11PM. He chose the 152
because it was cheaper per hour. When we got back I was able to
demonstrate that by flying the 172 which is faster and rents at
a higher rate per hour would have been pretty close to the same
amount of money. And no, we didn't need to go slow just to make
XC for his logbook.

[Tina]

If John needs to log 100 more hours to get his Commercial, and he's
paying $100 an hour dry Hobbs time, the airplane cost is $10,000. If
he burns 12 gallons an hour of $4 avgas he'll spend $4,800 on fuel --
if he does it at 7 gph $2,800. Crank in your own numbers, of course.
As those Wentworth commercials on TV say, "It's your money, use it
when you want to." Saving a couple of thousand dollars might be a
worthwhile consideration.

With respect to going to new and interesting places? Sure, but in
terms of learning good flying techniques, don't you think slower is
better than faster? Cross winds, airplane control, all of that matters
at least as much as flying into a new airport. My favorite pilot,
during his BFRs and check rides with his friends, doesn't often
demonstrate straight and level, but slow flight (I hate a Mooney's
attitude when he practices slow flight at 25 square, hanging that
thing on its prop.)


On Oct 14, 7:26 am, kontiki > wrote:
> Thomas Borchert wrote:
> > Your objective of saving fuel and prolonging flight time is unusual for
> > a renter. Still, if I were to build time with a rental aircraft and
> > cost would be the same regardless of power settings, I would GO to
> > exciting new places at the fullest speed available rather than dawdling
> > around in the area I know. With respect to time building for a
> > commercial, that tactic would be immensely valuable since it would
> > expose you to new terrain, different weather and unknown fields. So,
> > again, if cost remains the same regardless of power setting, IMHO you
> > might want to rethink how you build time. I would even suggest a
> > multi-day cross country to an area of the country you always wanted to
> > go to.
>
> > As a general rule, I normally use the maximum recommended cruise power
> > setting from the POH, since I normally want to go somewhere. That's
> > mostly 75 percent. I use best economy mixture if I have a tail wind and
> > best power if I have a headwind. Also, I use as low an RPM setting as
> > possible for noise reduction, but I have a choice, since my airplane
> > has a constant speed prop.
>
> I would say this is very good advice. I would much prefer to go
> somehwere and visit new and different airports to gain experience
> not just mindlessley logging time for your logbook. The goal of
> the 250 hours for the commercial is for you to gain flying
> experience and build skills.
>
> A few nights ago I flew with a student in a 152 on a night
> cross country and didn't get back till 11PM. He chose the 152
> because it was cheaper per hour. When we got back I was able to
> demonstrate that by flying the 172 which is faster and rents at
> a higher rate per hour would have been pretty close to the same
> amount of money. And no, we didn't need to go slow just to make
> XC for his logbook.- Hide quoted text -
>
> - Show quoted text -

[Peter Dohm]

"Thomas Borchert" > wrote in message
...
> John,
>
>> n the 172 I have reduced fuel from over 7.5 gph at 2400rpm to about
>> 5.5 gph at 2200-2300.
>>
>
> First of all, the power settings in the POH mostly make a lot of sense.
> Secondly, if you pay by Hobbs time, many people use what is referred to
> as "rental cruise", aka full throttle full rich. You probably save
> money by that, the rental outift probably won't.
>
> Your objective of saving fuel and prolonging flight time is unusual for
> a renter. Still, if I were to build time with a rental aircraft and
> cost would be the same regardless of power settings, I would GO to
> exciting new places at the fullest speed available rather than dawdling
> around in the area I know. With respect to time building for a
> commercial, that tactic would be immensely valuable since it would
> expose you to new terrain, different weather and unknown fields. So,
> again, if cost remains the same regardless of power setting, IMHO you
> might want to rethink how you build time. I would even suggest a
> multi-day cross country to an area of the country you always wanted to
> go to.
>
> As a general rule, I normally use the maximum recommended cruise power
> setting from the POH, since I normally want to go somewhere. That's
> mostly 75 percent. I use best economy mixture if I have a tail wind and
> best power if I have a headwind. Also, I use as low an RPM setting as
> possible for noise reduction, but I have a choice, since my airplane
> has a constant speed prop.
>
> --
> Thomas Borchert (EDDH)
>
Remember, he's renting dry.

Admittedly, that has been a little unusual for some time; but, with
fluctuating fuel prices, who knows?

In addition to asking the owner, I would ask around the local flying
clubs--since many flying clubs have tended to operate their equipment in a
similar manner.

Peter

[Thomas Borchert]

Peter,

> Remember, he's renting dry.
>

Darn, I overread that. Sorry. Might still be a good idea to find a
different rental place and go somewhere for the money.


--
Thomas Borchert (EDDH)

[Thomas Borchert]

Tina,

> and he's
> paying $100 an hour dry Hobbs time,

As I said, my remarks hold only if cost is independent of power setting.
Dry rentals are very uncommon, AFAIK. And I overread his remark that he
is indeed renting dry <blush>. Sorry!


> Sure, but in
> terms of learning good flying techniques, don't you think slower is
> better than faster?

Not at all. Both is important, IMHO.

--
Thomas Borchert (EDDH)

[Matt Whiting]

john wrote:
> Shortly after getting my private license I went to a different FBO and
> got checked out in their aircrafts - C172 and Piper Cherokee.
>
> I talked with the CFI and asked what RPM settings he would recommend.
> I'm renting dry, so one way to reduce cost is to slow down and thus
> save fuel. At the present time I'm just building hours towards my
> commercial ticket. Rarely am I in a hurry to get anywhere. He
> mentioned that if I needed to get somewhere quickly, to keep it around
> 2400. If I'm just building time then to reduce to 2300. It will save
> fuel as well as reduce the sound level.
>
> The CFI no longer flies out of that airport, so I don't have contact
> with him. I'm interested in others opinions related to rpm settings.
> Is there any harm to the engine with reducing the RPM even lower, say
> 2200 or even 2100 RPM. I will confess to bringing it back to as low
> as 1800 for a short X-C and found it to be good slow flight practice.,
> which gave my one leg a work out in order to keep the bubble in the
> middle. I wouldn't want to make many flights at 1800 though.
>
> In the 172 I have reduced fuel from over 7.5 gph at 2400rpm to about
> 5.5 gph at 2200-2300.

What power settings are in the airplane's operation manual? Any setting
listed by Cessna in the manual should be fine. Just don't forget to
lean properly.

Matt

[The Visitor[_2_]]

I cannot speak about a 172 but if you are actually cruising in slow
flight, as opposed to flying slow, I hope you are considering your
cylinder head temperatures and oil temperature.

John

john wrote:
> Shortly after getting my private license I went to a different FBO and
> got checked out in their aircrafts - C172 and Piper Cherokee.
>
> I talked with the CFI and asked what RPM settings he would recommend.
> I'm renting dry, so one way to reduce cost is to slow down and thus
> save fuel. At the present time I'm just building hours towards my
> commercial ticket. Rarely am I in a hurry to get anywhere. He
> mentioned that if I needed to get somewhere quickly, to keep it around
> 2400. If I'm just building time then to reduce to 2300. It will save
> fuel as well as reduce the sound level.
>
> The CFI no longer flies out of that airport, so I don't have contact
> with him. I'm interested in others opinions related to rpm settings.
> Is there any harm to the engine with reducing the RPM even lower, say
> 2200 or even 2100 RPM. I will confess to bringing it back to as low
> as 1800 for a short X-C and found it to be good slow flight practice.,
> which gave my one leg a work out in order to keep the bubble in the
> middle. I wouldn't want to make many flights at 1800 though.
>
> In the 172 I have reduced fuel from over 7.5 gph at 2400rpm to about
> 5.5 gph at 2200-2300.
>
> Thanks,
>
> John
>

[john]

Thanks for all of your imputs.

I don't have a 1974 POH, but I do have one for the 1978. It list the
green arc as 2200 - 2700, so as long as I keep it in the green I
should be alright. I'll check the 1974 POH next time I use that
plane, but I would be surprised if it is different since they have the
same engine. I do keep an eye on the temp guage. The main plane that
I fly tends to run a little hot anyways so reducing the throttle helps
keep the temps where they need to be.

In response to Kontiki's suggestion on new and interesting place, I
need the X-C time as well, so yes, I try to pick x-c trips when I have
more than an hour or two planned. Last week I took a friend up so
that he could take pictures of some land. When he was finished I
asked if he needed to get back right away. Since he didn't, I
diverted to an airport 30 miles further south where we landed and
grabbed a coke. I only need another 2 hours to complete the X-C
requirement, which I should complete next week when I take another
friend out for dinner. However, my goal is to land at every public
airport in the state. So I will have more than the hours needed in
that catagory.

John


On Oct 14, 8:08 am, The Visitor > wrote:
> I cannot speak about a 172 but if you are actually cruising in slow
> flight, as opposed to flying slow, I hope you are considering your
> cylinder head temperatures and oil temperature.
>
> John
>
>
>
> john wrote:
> > Shortly after getting my private license I went to a different FBO and
> > got checked out in their aircrafts - C172 and Piper Cherokee.
>
> > I talked with the CFI and asked what RPM settings he would recommend.
> > I'm renting dry, so one way to reduce cost is to slow down and thus
> > save fuel. At the present time I'm just building hours towards my
> > commercial ticket. Rarely am I in a hurry to get anywhere. He
> > mentioned that if I needed to get somewhere quickly, to keep it around
> > 2400. If I'm just building time then to reduce to 2300. It will save
> > fuel as well as reduce the sound level.
>
> > The CFI no longer flies out of that airport, so I don't have contact
> > with him. I'm interested in others opinions related to rpm settings.
> > Is there any harm to the engine with reducing the RPM even lower, say
> > 2200 or even 2100 RPM. I will confess to bringing it back to as low
> > as 1800 for a short X-C and found it to be good slow flight practice.,
> > which gave my one leg a work out in order to keep the bubble in the
> > middle. I wouldn't want to make many flights at 1800 though.
>
> > In the 172 I have reduced fuel from over 7.5 gph at 2400rpm to about
> > 5.5 gph at 2200-2300.
>
> > Thanks,
>
> > John- Hide quoted text -
>
> - Show quoted text -

[Newps]

Mortimer Schnerd, RN wrote:

>
> One thought about continued flight at 1800 rpm: if you were running with the
> carb heat on to avoid icing, then you're ingesting unfiltered air. Best to keep
> that at a minimum if you can.



In a cruise flight you should be running the amount of carb heat that
gives you a carb temp of 40F.

[[email protected]]

Don't they teach Flight for Range in the U.S.?

Start at cruise RPM. Record the airspeed when things have
stabilized. Reduce the RPM by 100, wait for everything to stabilize,
including adjusting the throttle for the RPM target, trim the airplane
for level flight, and record the airspeed again. Do this in 100 RPM
increments until the airspeed suffers a much bigger drop than with the
previous settings, and go back to the last setting. Now you have the
lowest fuel flow for the best airspeed. Be sure to lean as necessary
and keep that RPM where it should be. Remember the power setting for
that airplane for the next time.
Best endurance involves finding the lowest RPM where the
airplane will maintain altitude. It'll be a pretty slow airplane. Slow
flight involves a lower airspeed but more power to maintain the
altitude.

Dan

[JGalban via AviationKB.com]

john wrote:
>
>I don't have a 1974 POH, but I do have one for the 1978. It list the
>green arc as 2200 - 2700, so as long as I keep it in the green I
>should be alright. I'll check the 1974 POH next time I use that
>plane, but I would be surprised if it is different since they have the
>same engine.

That's simply the normal operating range. The POH will also have graphs
or tables that will give you power and fuel burn information for various
altitudes and temperatures. Use them.

I often hear pilots saying things like, "What rpm should I use for cruise?
" and hardly ever hear the correct answer, which is : It depends. What it
depends on is the amount of power you wish to generate, and the density
altitude at which you'll be flying. To make a given percentage of power,
the rpm required will increase as the density altitude increases (in a fixed
pitch plane like the 172). If you want to fly around at an economical 55%
power setting, the rpm you should set will be very different if you're flying
low on a cold day, or high on a hot day.

Quick example : The rpm that I use in my Cherokee to fly 75% cruise at 6,
000 ft. on a hot day is very close to the rpm that I'd use to fly at 100%
power (not a good cruise setting) near sea level on a standard day.

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

--
Message posted via AviationKB.com
http://www.aviationkb.com/Uwe/Forums.aspx/aviation/200710/1

[Brett Meares]

It seems to me that you would set up whatever power required to cruise at
best L/D and that would necessarily give you best range. Brett



"JGalban via AviationKB.com" <u32749@uwe> wrote in message
news:79bea10122a88@uwe...
> john wrote:
>>
>>I don't have a 1974 POH, but I do have one for the 1978. It list the
>>green arc as 2200 - 2700, so as long as I keep it in the green I
>>should be alright. I'll check the 1974 POH next time I use that
>>plane, but I would be surprised if it is different since they have the
>>same engine.
>
> That's simply the normal operating range. The POH will also have graphs
> or tables that will give you power and fuel burn information for various
> altitudes and temperatures. Use them.
>
> I often hear pilots saying things like, "What rpm should I use for
> cruise?
> " and hardly ever hear the correct answer, which is : It depends. What
> it
> depends on is the amount of power you wish to generate, and the density
> altitude at which you'll be flying. To make a given percentage of
> power,
> the rpm required will increase as the density altitude increases (in a
> fixed
> pitch plane like the 172). If you want to fly around at an economical
> 55%
> power setting, the rpm you should set will be very different if you're
> flying
> low on a cold day, or high on a hot day.
>
> Quick example : The rpm that I use in my Cherokee to fly 75% cruise at 6,
> 000 ft. on a hot day is very close to the rpm that I'd use to fly at 100%
> power (not a good cruise setting) near sea level on a standard day.
>
> John Galban=====>N4BQ (PA28-180)
>
> --
> Message posted via AviationKB.com
> http://www.aviationkb.com/Uwe/Forums.aspx/aviation/200710/1
>

[EridanMan]

By Aerodynamic Definition, your most efficient cruise speed for time
aloft is the the drag curve minima (point between the induced drag
curve and the profile drag curve), which also conveniently happens to
be defined as Vg. This is the speed at which the aircraft requires
the least amount of energy to stay aloft.

Power back to maintain Vg, lean the hell out of it (At such a low
power setting detonation is a non-issue), and cruise to your hearts
content.

Do not fly "as slow as possible", keep in mind if your airspeed drops
below Vg, your power requirements will actually go back up.

-Scott

[Bertie the Bunyip[_19_]]

Bob Moore > wrote in
46.128:

> EridanMan wrote
>> By Aerodynamic Definition, your most efficient cruise speed for time
>> aloft is the the drag curve minima (point between the induced drag
>> curve and the profile drag curve), which also conveniently happens to
>> be defined as Vg. This is the speed at which the aircraft requires
>> the least amount of energy to stay aloft.
>
> By who's definition? In 50 years of flying, 39 years of instructing,
> 10 years military and 25 years of airline flying, I've never heard
> of Vg, L/D Max maybe, even Best Glide Speed, but Vg? Not here in the
> USofA.


Neither have I. And I can add glider to that list.


Bertie

[Bertie the Bunyip[_19_]]

Bob Moore > wrote in
46.128:

> EridanMan wrote
>> By Aerodynamic Definition, your most efficient cruise speed for time
>> aloft is the the drag curve minima (point between the induced drag
>> curve and the profile drag curve), which also conveniently happens to
>> be defined as Vg. This is the speed at which the aircraft requires
>> the least amount of energy to stay aloft.
>
> By who's definition? In 50 years of flying, 39 years of instructing,
> 10 years military and 25 years of airline flying, I've never heard
> of Vg, L/D Max maybe, even Best Glide Speed, but Vg? Not here in the
> USofA.
>

Found it . It's a Nigel thing.


Bertie

[Bush]

Hmm most airliners are set up to operate most efficiently at L/D Max
+5%. In the case you cannot achieve this in a piston powered aircraft,
please read the POH section on performance. 2300 rpm was always good
in a 172 IIRC, the fact that you can rent dry is a plus.

Have a great one!

Bush

On Sun, 14 Oct 2007 03:16:39 -0000, john > wrote:

>Shortly after getting my private license I went to a different FBO and
>got checked out in their aircrafts - C172 and Piper Cherokee.
>
>I talked with the CFI and asked what RPM settings he would recommend.
>I'm renting dry, so one way to reduce cost is to slow down and thus
>save fuel. At the present time I'm just building hours towards my
>commercial ticket. Rarely am I in a hurry to get anywhere. He
>mentioned that if I needed to get somewhere quickly, to keep it around
>2400. If I'm just building time then to reduce to 2300. It will save
>fuel as well as reduce the sound level.
>
>The CFI no longer flies out of that airport, so I don't have contact
>with him. I'm interested in others opinions related to rpm settings.
>Is there any harm to the engine with reducing the RPM even lower, say
>2200 or even 2100 RPM. I will confess to bringing it back to as low
>as 1800 for a short X-C and found it to be good slow flight practice.,
>which gave my one leg a work out in order to keep the bubble in the
>middle. I wouldn't want to make many flights at 1800 though.
>
>In the 172 I have reduced fuel from over 7.5 gph at 2400rpm to about
>5.5 gph at 2200-2300.
>
>Thanks,
>
>John

[EridanMan]

Vg = Best Glide Speed (I'm sorry, I should have specified) = L/D max.

Sorry, I should have made that clear.