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

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

tman 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.

When I fill the fuel to the *tabs*, calc everyone's weight honestly and
consider baggage -- I'm 75 lbs over the 2450 gross on departure. Maybe
100 over gross if I assume a "lie about weight" factor or some
inaccuracy with filling the tanks. Now I'm scratching my head about
just how risky this is. I know (others) have pushed over gross in these
planes way more under worse conditions, and have almost always gotten
away with it. I'm inclined to just do it, and be cognizant that it will
perform differently, i.e. don't expect the same picture on climbout that
you would when solo.

Risky? Or just roundoff error on the weight? Here are some other factors:

This is the 160HP C172, standard.
Departure runway is 5000'.
No steep terrain to climb out of.
Plenty of alternates along with the way with 3000 runways.
Not particularly hot, humid, or high. 50 degrees at 1000 MSL for
departure or any point of landing.

I'm figuring I'm 3% over gross, causing most of my V speeds to increase
1.5%, so say -- instead of flying short final at 65 knots, I'd fly at 66
knots... OK wait I can't hold airspeed to +/- 1 knot on most days anyways.

I'm thinking through many of the factors, and it is only a "little" over
gross, only on the first hour or so of the trip. What else should I be
aware of? Am I dangerous?

T

I never advise a pilot to load any airplane over gross.
I will tell you that the big killer in these situations is the cg
location, especially the aft cg.
Tell you what; instead of my "advising you" on what to do specifically
with this flight, let me suggest to you that you run a weight and
balance for this aircraft at full tanks, THEN run the same pax and
baggage loading figuring 1/4 tanks, just to see what this does to the cg.


--
Dudley Henriques

Dudley Henriques wrote:
Tell you what; instead of my "advising you" on what to do specifically
with this flight, let me suggest to you that you run a weight and
balance for this aircraft at full tanks, THEN run the same pax and
baggage loading figuring 1/4 tanks, just to see what this does to the cg.

I did. CG is pretty much center of the acceptable range.
C172 410lbs in the front seats, 170lbs in the back, 30lbs in the baggage
area, fuel to tabs -- CG is "good". Same situation, empty fuel. CG
good too.

A lot of ppl are talking about CG issues. Hey maybe I better check my
math before I fly this thing!

tman wrote:
I did. CG is pretty much center of the acceptable range.
C172 410lbs in the front seats, 170lbs in the back, 30lbs in the baggage
area, fuel to tabs -- CG is "good". Same situation, empty fuel. CG
good too.

A lot of ppl are talking about CG issues. Hey maybe I better check my
math before I fly this thing!


That's because CG is particularly critical when you're heavy. That's one of the
reasons I used to prefer the PA-32 over the C-210 for my runs to the islands.
The PA-32s all have this huge baggage compartment aft of the engine but forward
of the passenger compartment. It allowed me to stuff it full of the heaviest
crap I had to carry. Then loading all the beef in the back would leave me with
a quite acceptable CG. 6 people, baggage, full fuel (didn't mean to do that)
and hot summer day. Slow climbing but I eventually waddled up to 8,000 feet and
had a completely normal flight from that point on.

OTOH, I once took four folks down to Florida in a modified C-172 that had 180 HP
and a constant speed prop. The lardasses in the back threw me into an aft CG
situation that was acceptable until I got 20 degrees of flaps down; then I
didn't have enough trim authority to get all the pressure off the yoke. I had
to muscle it in... a rather uncomfortable situation for a fingertip kind of
flier. Sure did flare easily though...

Somebody said something about you've never carried four passengers in a C-172?
If that's the case I take back what I said earlier about making the flight. You
definitely want to take a few rides around the local area with some folks in the
back... it's not the same as just 2 guys in the front.

The other thing to consider is the very limited baggage space of the C-172.
When you pack it, you want the load as forward as you can make it. As the arm
gets longer, it's amazing the effect of weight back there.

I'm not much for experimenting heavily (pardon the pun) when I have only limited
experience. Will the C-172 fly 50 or even 100 lbs overgrossed? I know it will.
I also know I wouldn't want an inexperienced pilot behind the controls when I
did it. And a cold day would be helpful.



--
Mortimer Schnerd, RN
mschnerdatcarolina.rr.com