Depression after Washing

"Mike" wrote in message
news:2Rrbk.459$713.307@trnddc03...
Nonsense. If you are human, and especially if you lack x-ray vision, you
can miss damage on a preflight.

The chances of any such 'invisible' damage being a safety of flight issue are
pretty much nil. Someone might crinkle a firewall with a wheelbarrow landing
or overstress the airframe, but the chances of that being a safety of flight
issue in the near term are next to nothing. But if someone bangs up a wing or
a tail against a hanger, flat spots a tire, or has a prop strike this is going
to show up during a proper pre-flight.

Obviously, you haven't seen some of the things I have seen. One of the more
tender, and more invisible spots on some airframes is where the horizontal
stabilizer connects to the fuze. Many designs allow a tremendous moment arm for
any non-balanced load on the stabilizer to stress the attachment points. This
shows up as cracked spars on Cessnas, and I have seen stressed and cracked
fittings from another airframe. How can this happen? Well on Cessnas it
happens from folks using improper procedures to back the plane into a parking
spot. It can also happen from innocent (but ignorant) bystanders, mowers,
animal activity, or any of thousands of other posibilities.

Also, you don't know what happened on the last flight. Excessively hard
landing? Botched manuver? These and countless other things can cause
difficult-to-detect damage to an airframe.

One list item: The standard for passing a preflight inspection is not
"safety of flight in the near term". I would hope that you would consider an
airplane not airworthy long before that.


So what trick do you use to get them to do the runup?

The most polite thing I can say is that was an unnecessary comment.

(I don't want this to turn into a flame war so you may have the last word.)

Vaughn

"Vaughn Simon" wrote in message
...

"Mike" wrote in message
news:2Rrbk.459$713.307@trnddc03...
Nonsense. If you are human, and especially if you lack x-ray vision,
you can miss damage on a preflight.

The chances of any such 'invisible' damage being a safety of flight issue
are pretty much nil. Someone might crinkle a firewall with a wheelbarrow
landing or overstress the airframe, but the chances of that being a
safety of flight issue in the near term are next to nothing. But if
someone bangs up a wing or a tail against a hanger, flat spots a tire, or
has a prop strike this is going to show up during a proper pre-flight.

Obviously, you haven't seen some of the things I have seen. One of the
more tender, and more invisible spots on some airframes is where the
horizontal stabilizer connects to the fuze. Many designs allow a
tremendous moment arm for any non-balanced load on the stabilizer to
stress the attachment points. This shows up as cracked spars on Cessnas,
and I have seen stressed and cracked fittings from another airframe. How
can this happen? Well on Cessnas it happens from folks using improper
procedures to back the plane into a parking spot. It can also happen from
innocent (but ignorant) bystanders, mowers, animal activity, or any of
thousands of other posibilities.

I always give each side a good heave up and down for this very reason, so
such can easily be checked on the preflight for impending failure.

Also, you don't know what happened on the last flight. Excessively
hard landing? Botched manuver? These and countless other things can
cause difficult-to-detect damage to an airframe.

Certainly. But that's what pre-flight and annual inspections are for. My
A&P found a cracked bulkhead in the tail on my first annual after I bought
the plane. It had probably been that way for years. Such problems you
mentioned are common, but how many airframes do you see breaking up in
flight because of it?

One list item: The standard for passing a preflight inspection is not
"safety of flight in the near term". I would hope that you would consider
an airplane not airworthy long before that.

The preflight is just a simple way to find out if the aircraft is airworthy
to the best of the pilot's ability. I never suggested it was anything else,
so you should go back and check your inference for any degree of
reasonableness.

So what trick do you use to get them to do the runup?

The most polite thing I can say is that was an unnecessary comment.

(I don't want this to turn into a flame war so you may have the last
word.)

Vaughn

So why do you take a simple statement and take it to the nth degree? The
previous poster (who has no flight experience, btw) condemned partial
ownership because another owner might "damage" the airplane and not tell
anyone. It was a ridiculous statement to begin with because a proper
preflight and regular inspections make such a non issue to the safety of
flight. That was the context of my statement. Instead you want to turn
this into some obscure situation. Is it possible to have damage that goes
undetected during a preflight? Yes. Is such damage a concern? The
statistics suggest you should be more concerned about being hit by
lightning. If you don't want to get flamed, try working your way up the
thread and figuring out what the context is before you jump on a comment and
try to make it something it isn't.

My "comment" was far more valid than yours, BTW. If you have a student that
you can't even trust to do a preflight, how are you going to trust them to
do anything else that can save their lives? If you have such students you
can't trust to perform basic safety of flight tasks, you shouldn't let them
solo until they mature.

Mike writes:

I always give each side a good heave up and down for this very reason, so
such can easily be checked on the preflight for impending failure.

It is unlikely that you can create the same magnitude and type of stress with
"a good heave" that the aircraft would or could experience in flight.

Certainly. But that's what pre-flight and annual inspections are for. My
A&P found a cracked bulkhead in the tail on my first annual after I bought
the plane. It had probably been that way for years. Such problems you
mentioned are common, but how many airframes do you see breaking up in
flight because of it?

More than necessary. And an annual inspection provides a year for things to
go wrong in flight.

The preflight is just a simple way to find out if the aircraft is airworthy
to the best of the pilot's ability. I never suggested it was anything else,
so you should go back and check your inference for any degree of
reasonableness.

You said that if a pilot doesn't find damage, he hasn't done a preflight,
which implies that a preflight will find all damage. Have you changed your
mind?

So why do you take a simple statement and take it to the nth degree?

It is only necessary to show that the statement cannot stand, which has been
done.

The previous poster (who has no flight experience, btw) condemned partial
ownership because another owner might "damage" the airplane and not tell
anyone. It was a ridiculous statement to begin with because a proper
preflight and regular inspections make such a non issue to the safety of
flight.

Except that this is not true.

You made an absolute statement where a qualified one was required.

If you don't want to get flamed, try working your way up the
thread and figuring out what the context is before you jump on a comment and
try to make it something it isn't.

In the future, structure your statements more carefully, and you will not find
yourself in a corner in debate.

My "comment" was far more valid than yours, BTW.

Your statement that, in effect, a preflight cannot fail to find damage and
that a pilot who does not find damage has not done a preflight inspection was
manifestly false, and does a disservice to pilots who do a thorough preflight
inspection and yet die anyway as a consequence of damage that no preflight
inspection can detect.

"Mxsmanic" wrote in message
...
Mike writes:

I always give each side a good heave up and down for this very reason, so
such can easily be checked on the preflight for impending failure.

It is unlikely that you can create the same magnitude and type of stress
with
"a good heave" that the aircraft would or could experience in flight.

Nor is that the intention.

Certainly. But that's what pre-flight and annual inspections are for.
My
A&P found a cracked bulkhead in the tail on my first annual after I
bought
the plane. It had probably been that way for years. Such problems you
mentioned are common, but how many airframes do you see breaking up in
flight because of it?

More than necessary.

How many do you think that is?

The preflight is just a simple way to find out if the aircraft is
airworthy
to the best of the pilot's ability. I never suggested it was anything
else,
so you should go back and check your inference for any degree of
reasonableness.

You said that if a pilot doesn't find damage, he hasn't done a preflight,
which implies that a preflight will find all damage. Have you changed
your
mind?

Actually I said damage was a non-issue because of the preflight because any
damage that would be an issue for the next flight is going to be found
during the preflight.


So why do you take a simple statement and take it to the nth degree?

It is only necessary to show that the statement cannot stand, which has
been
done.

The previous poster (who has no flight experience, btw) condemned partial
ownership because another owner might "damage" the airplane and not tell
anyone. It was a ridiculous statement to begin with because a proper
preflight and regular inspections make such a non issue to the safety of
flight.

Except that this is not true.

You made an absolute statement where a qualified one was required.

Actually what I have done is show that your fear of "damage" by someone else
is irrational and a weak point against partial ownership.

So once again you've shown your "experience" is limited by what Microsoft FS
can offer.


If you don't want to get flamed, try working your way up the
thread and figuring out what the context is before you jump on a comment
and
try to make it something it isn't.

In the future, structure your statements more carefully, and you will not
find
yourself in a corner in debate.

My "comment" was far more valid than yours, BTW.

Your statement that, in effect, a preflight cannot fail to find damage and
that a pilot who does not find damage has not done a preflight inspection
was
manifestly false, and does a disservice to pilots who do a thorough
preflight
inspection and yet die anyway as a consequence of damage that no preflight
inspection can detect.

Go do a search of the NTSB database sometime and see how many of those cases
you can find, then tell me again about my "disservice".

On Jul 4, 4:56 pm, "Mike" wrote:

Obviously, you haven't seen some of the things I have seen. One of the
more tender, and more invisible spots on some airframes is where the
horizontal stabilizer connects to the fuze. Many designs allow a
tremendous moment arm for any non-balanced load on the stabilizer to
stress the attachment points. This shows up as cracked spars on Cessnas,
and I have seen stressed and cracked fittings from another airframe. How
can this happen? Well on Cessnas it happens from folks using improper
procedures to back the plane into a parking spot. It can also happen from
innocent (but ignorant) bystanders, mowers, animal activity, or any of
thousands of other posibilities.

I always give each side a good heave up and down for this very reason, so
such can easily be checked on the preflight for impending failure.

A good heave up and down on the end of the stab of a 172
flexes the center of the forward spar, eventually cracking it. A
gentle bit of push-pull is all that's needed, to see if there's
unusual tip travel. I bet your spar is cracked now. Many are. Cessna
calls for stopdrilling the crack unless it has reached the spar
flange, in which case it has to be repaired. I once flew a 172 that I
subsequently found had a broken spar, busted clear through both
flanges so that the skin was all that was holding it. The thing could
have killed me if I gotten into turbulence or had to take violent
evasive action. We run several 172s and have seen cracks, up to four
of them, in a spar; we now forbid students to push down on the things.
No more cracks.
172s suffer cracking at the bottom of the aft doorposts. Some
models crack inside the forward doorposts. Do I need to point out that
these doorposts are what the wing pulls on to lift the airplane, along
with the struts? No preflight will find those. The wing spar attach
lugs are known to crack at the bolt holes. In older 172s the forward
elevator bellcrack bracket would break loose, reducing elevator
control. In newer 172s (rod-style gear; 1973 or so and on) the landing
gear retaining bolt sometimes shears and totals the airplane on
landing. As the years go by, these older airplanes will become the
subjects of ADs addressing age-related airframe failure, probably
after a couple come apart in flight. Sooner or later.

Dan

On Jul 6, 4:45*am, wrote:
On Jul 4, 4:56 pm, "Mike" wrote:

*Obviously, you haven't seen some of the things I have seen. *One of the
more tender, and more invisible spots on some airframes is where the
horizontal stabilizer connects to the fuze. *Many designs allow a
tremendous moment arm for any non-balanced load on the stabilizer to
stress the attachment points. *This shows up as *cracked spars on Cessnas,
and I have seen stressed and cracked fittings from another airframe. *How
can this happen? *Well on Cessnas it happens from folks using improper
procedures to back the plane into a parking spot. *It can also happen from
innocent (but ignorant) bystanders, mowers, animal activity, or any of
thousands of other posibilities.

I always give each side a good heave up and down for this very reason, so
such can easily be checked on the preflight for impending failure.

* * * * *A good heave up and down on the end of the stab of a 172
flexes the center of the forward spar, eventually cracking it. A
gentle bit of push-pull is all that's needed, to see if there's
unusual tip travel. I bet your spar is cracked now. Many are. Cessna
calls for stopdrilling the crack unless it has reached the spar
flange, in which case it has to be repaired. I once flew a 172 that I
subsequently found had a broken spar, busted clear through both
flanges so that the skin was all that was holding it.


Why did your push-pull test not detect it? I prefer to give a shake
and feel the nature of surface response.

Cheers

On Jul 5, 3:58 pm, More_Flaps wrote:

Why did your push-pull test not detect it? I prefer to give a shake
and feel the nature of surface response.

That's why I have a push-pull test now. Didn't do it until
after I flew that airplane and took it apart after I got it here.
Found a lot of other stuff, too: lower strut attach bolts with no
nuts, and backing out of their holes; cracks in lots of places; scary
stuff galore. The owner trucked it away. In pieces.

Dan

On Sat, 5 Jul 2008 09:45:11 -0700 (PDT),
wrote:


evasive action. We run several 172s and have seen cracks, up to four
of them, in a spar; we now forbid students to push down on the things.
No more cracks.

Just out of curiosity, is this before or after Cessna put the
reinforced spars (R and S models?) in at the factory? I don't believe
the newer models are prone to this kind of issue, but wouldn't do it
in practice anyway - using the towbar is always better for the
aircraft, and done by hand I don't think it's possible to damage a
172/182 nosewheel.

On Jul 5, 4:26 pm, Peter Clark
wrote:
On Sat, 5 Jul 2008 09:45:11 -0700 (PDT),
wrote:

evasive action. We run several 172s and have seen cracks, up to four
of them, in a spar; we now forbid students to push down on the things.
No more cracks.

Just out of curiosity, is this before or after Cessna put the
reinforced spars (R and S models?) in at the factory? I don't believe
the newer models are prone to this kind of issue, but wouldn't do it
in practice anyway - using the towbar is always better for the
aircraft, and done by hand I don't think it's possible to damage a
172/182 nosewheel.

There's a Service Bulletin dealing with this, and it's dated to
before the R/S models went into production, so it's safe to figure
that Cessna fixed the problem in these models. The SB calls for
stopdrilling and monitoring every 100 hours, and fixing it by
installing a doubler either right away or when the cracks go too far.
The problem with waiting is that the centre section needs to be
replaced if the cracks reach the flanges.
I'll know more later. We're getting a new or newer one, maybe
two, soon. Interesting to see what they've improved, and what they
haven't but should have.
Which reminds me: there are other places that crack, not
readily visible. The rudder hinge brackets (on the rudder itself, not
the fin) will break in the bend radii. The top hinge is the worst, as
it has the loads of the lead balance weight wobbling around in the
turbulence to deal with. Got to use a tiny mirror and lots of light to
see the break. We spin these airplanes all the time, and in a spin
the tail wiggles around a lot, so maybe the non-spinning pilot won't
have a problem with these. Spins are also hard on gyros, whacking the
internal gyro cases against their stops and Brinelling the bearings.
But that's all part of flight training, and we charge enough to cover
things like that. We go through more propellers, too, operating off
rougher strips and picking up small stones.
These rudder brackets also wear against the fin lugs, since the
spacing at the factory was often screwed up so that the bottom hinge's
top bracket doesn't ride on its bearing flange like it's supposed to,
letting the middle and/or upper hinges take the thrust loads so they
wear thin. No thrust flanges on those bearings; just aluminum against
aluminum, and sitting outside in the wind those hinges get full of
grit and the wind wiggles the rudder and the brackets eat themselves.
I've asked Cessna to issue some teflon washers to shim the bottom
bearing and get the load off the others, but they pay no attention to
a hick from rural Canada. The law here says we have to use only the
stuff from the parts manuals, and they don't list any such washers.
The rudder bar springs put tension on the rudder cables. Those
cables aren't pulling perpendicular to the hinge line becease the
rudder is tilted back, so the rudder is pulled down, increasing the
load on the hinge thrust faces.

Dan

wrote in message
...
On Jul 4, 4:56 pm, "Mike" wrote:

Obviously, you haven't seen some of the things I have seen. One of
the
more tender, and more invisible spots on some airframes is where the
horizontal stabilizer connects to the fuze. Many designs allow a
tremendous moment arm for any non-balanced load on the stabilizer to
stress the attachment points. This shows up as cracked spars on
Cessnas,
and I have seen stressed and cracked fittings from another airframe.
How
can this happen? Well on Cessnas it happens from folks using improper
procedures to back the plane into a parking spot. It can also happen
from
innocent (but ignorant) bystanders, mowers, animal activity, or any of
thousands of other posibilities.

I always give each side a good heave up and down for this very reason, so
such can easily be checked on the preflight for impending failure.

A good heave up and down on the end of the stab of a 172
flexes the center of the forward spar, eventually cracking it. A
gentle bit of push-pull is all that's needed, to see if there's
unusual tip travel. I bet your spar is cracked now. Many are. Cessna
calls for stopdrilling the crack unless it has reached the spar
flange, in which case it has to be repaired. I once flew a 172 that I
subsequently found had a broken spar, busted clear through both
flanges so that the skin was all that was holding it. The thing could
have killed me if I gotten into turbulence or had to take violent
evasive action. We run several 172s and have seen cracks, up to four
of them, in a spar; we now forbid students to push down on the things.
No more cracks.
172s suffer cracking at the bottom of the aft doorposts. Some
models crack inside the forward doorposts. Do I need to point out that
these doorposts are what the wing pulls on to lift the airplane, along
with the struts? No preflight will find those. The wing spar attach
lugs are known to crack at the bolt holes. In older 172s the forward
elevator bellcrack bracket would break loose, reducing elevator
control. In newer 172s (rod-style gear; 1973 or so and on) the landing
gear retaining bolt sometimes shears and totals the airplane on
landing. As the years go by, these older airplanes will become the
subjects of ADs addressing age-related airframe failure, probably
after a couple come apart in flight. Sooner or later.

1. By "good heave" I don't mean raising the nosewheel off the ground. I
just mean applying enough pressure both directions to listen for any
irregularities.

2. I don't have a 172.