Should I be scared -- C172 over Gross

On Apr 17, 11:27 am, "Robert M. Gary" wrote:
On Apr 17, 2:53 am, tman inv@lid wrote:

Flown C172's for quite a while, and never had anybody in the back.
Now I'm planning on quite a trip, with 2 pax and luggage.

The biggest problem with flying a little overgross is the same problem
with flying at high density altitude. The plane will perform different
and a pilot who isn't expecting this can run into serious problems.
The site picture over the nose will look a bit different. This is why
I always teach my students to climb out on airspeed. I know some CFIs
focus on the site pitch picture but that only works with consistant
weight, altitude, etc.
Many pilots have bitten the big one because they keep pulling the nose
up when climbing out of mountain airports until they stall it. They
keep trying to achieve the site picture their CFI taught them down in
the valley.

-robert, CFII

Consider this. When was the last time the airplane was weighed? Does
your engine performance exactly the same as when it was manufactured?
Do you get the same cruise speeds as published on the AFM?

Even if the airplane is perfectly airworthy, and all maintenance done
properly, you don't know if the engine is producing 160HP (or whatever
the rated power for your airplane). There is no signature in the
logbook that certifies that the airplane engine has been tested and
found to produce the specified power. I have flown rentals that flew
like a 120HP Cessna instead of a 160 HP. RPM can't tell you the true
power because every airplane uses a different pitch prop.

Chances are this airplane is a little heavier, and engine is little
weaker. Almost every rental airplane I have flown does not cruise as
the book says. Takeoff and landing performance has a lot to do with
pilot capability, but cruise performance is a good benchmark that does
not involve pilot capability.

If you have ever flown an airplane at max gross or close to it, then
you have flown it overgross. Legally the airplane may not be over
gross, but practically it is.

Not only do I recommend against flying overgross, I do not recommend
flying at gross either, unless you are the owner of that airplane and
are very familiar its performance.

Almost every rental airplane I have flown does not cruise as
the book says.

Nither do the new cessna right out of the factory! I have flown plenty
Now Cirrus Hell yea better than Book most the time!

On Apr 18, 9:20*am, Andrew Sarangan wrote:

Even if the airplane is perfectly airworthy, and all maintenance done
properly, you don't know if the engine is producing 160HP (or whatever
the rated power for your airplane). There is no signature in the
logbook that certifies that the airplane engine has been tested and
found to produce the specified power. I have flown rentals that flew
like a 120HP Cessna instead of a 160 HP. RPM can't tell you the true
power because every airplane uses a different pitch prop.


Well if the renter is slappin' on any old prop then you should not go
there. How does a 120 HP 172 reach cruise airspeed at cruise RPM?

Cheers

WingFlaps wrote in news:d33d5865-938c-4cae-acb3-
:

On Apr 18, 9:20*am, Andrew Sarangan wrote:

Even if the airplane is perfectly airworthy, and all maintenance done
properly, you don't know if the engine is producing 160HP (or
whatever
the rated power for your airplane). There is no signature in the
logbook that certifies that the airplane engine has been tested and
found to produce the specified power. I have flown rentals that flew
like a 120HP Cessna instead of a 160 HP. RPM can't tell you the true
power because every airplane uses a different pitch prop.


Well if the renter is slappin' on any old prop then you should not go
there. How does a 120 HP 172 reach cruise airspeed at cruise RPM?

Coasely pitched props don't allow good static HP because the RPM doesn't
get up to where it needs to be to produce HP. That's what variable pitch
props are all about.

Bertie

On Apr 18, 2:43Â*pm, Bertie the Bunyip wrote:
WingFlaps wrote in news:d33d5865-938c-4cae-acb3-
:



On Apr 18, 9:20�am, Andrew Sarangan wrote:

Even if the airplane is perfectly airworthy, and all maintenance done
properly, you don't know if the engine is producing 160HP (or
whatever
the rated power for your airplane). There is no signature in the
logbook that certifies that the airplane engine has been tested and
found to produce the specified power. I have flown rentals that flew
like a 120HP Cessna instead of a 160 HP. RPM can't tell you the true
power because every airplane uses a different pitch prop.

Well if the renter is slappin' on any old prop then you should not go
there. How does a 120 HP 172 reach cruise airspeed at cruise RPM?

Coasely pitched props don't allow good static HP because the RPM doesn't
get up to where it needs to be to produce HP. That's what variable pitch
props are all about.


Yes, but my point is that cruise speed also tells you about HP on a
daily basis. As far as I know, there are only a very limited number of
approved props for each 172 variant. If you don't see the magic static
RPM as specified in the POH it's time to investigate not fly -right?

Cheers

WingFlaps wrote in news:cb62baf1-cf48-423f-b9c5-
:

On Apr 18, 2:43Â*pm, Bertie the Bunyip wrote:
WingFlaps wrote in news:d33d5865-938c-4cae-
acb3-
:



On Apr 18, 9:20�am, Andrew Sarangan wrote:


Even if the airplane is perfectly airworthy, and all maintenance
done
properly, you don't know if the engine is producing 160HP (or
whatever
the rated power for your airplane). There is no signature in the
logbook that certifies that the airplane engine has been tested
and
found to produce the specified power. I have flown rentals that
flew
like a 120HP Cessna instead of a 160 HP. RPM can't tell you the
true
power because every airplane uses a different pitch prop.

Well if the renter is slappin' on any old prop then you should not
go
there. How does a 120 HP 172 reach cruise airspeed at cruise RPM?

Coasely pitched props don't allow good static HP because the RPM
doesn't
get up to where it needs to be to produce HP. That's what variable
pitch
props are all about.


Yes, but my point is that cruise speed also tells you about HP on a
daily basis. As far as I know, there are only a very limited number of
approved props for each 172 variant. If you don't see the magic static
RPM as specified in the POH it's time to investigate not fly -right?

Oh, OK, yeah, that's right. But you can have an absolutely beat engine
and still get the revs in cruise for most airplanes. My father had an
old Mercedes I borrowed off him once. Went fine, but he lived in a very
flat area and I took it to a multi story parking lot and couldn't get it
up the ramp. I looked around it the next day and found the cam lobes
almost round!




Bertie

On Apr 17, 8:39 pm, WingFlaps wrote:
On Apr 18, 9:20 am, Andrew Sarangan wrote:

Even if the airplane is perfectly airworthy, and all maintenance done
properly, you don't know if the engine is producing 160HP (or whatever
the rated power for your airplane). There is no signature in the
logbook that certifies that the airplane engine has been tested and
found to produce the specified power. I have flown rentals that flew
like a 120HP Cessna instead of a 160 HP. RPM can't tell you the true
power because every airplane uses a different pitch prop.

Well if the renter is slappin' on any old prop then you should not go
there. How does a 120 HP 172 reach cruise airspeed at cruise RPM?

Cheers

You can't just slap on any old propeller, legally. The Type
Certificate Data Sheet for any particular models lists the props that
may be used, and any other prop would require an STC. The TCDS also
gives the maximum and minimum static RPM for each model of propeller,
and if the engine can's get into that range it's either sick or the
prop's a dud. We do a full-power static runup on practically every
inspection. Take three seconds.
TCDS's are on the FAA's website.

Dan

wrote:
The TCDS also
gives the maximum and minimum static RPM for each model of propeller,
and if the engine can's get into that range it's either sick or the
prop's a dud.

I HAVE to remember to do something about the use of the word "Dud"
around here!!!!
:-))))))))))))


--
Dudley Henriques