C172 safety: Screws under the wing above the doors

Our 172 has two screws missing from under the wing where
it connects to the fuselage above passenger door.

The size of those screws are quite big. My question is whether
they are important to the stuctural integrity of the wing ? They
may have come off during flight due to the vibrations. But it
is still some hours before the next 100 hours.

Are those screws important for holding the wing to the fuselage ?
or are they only there to cover the holes, and there are some
other bigger screws/nuts inside the wing that are doing the real
work ?

A speedy reply will be appreciated.

P S

sounds like screws that cover the trim piece where the wing and fuselage
meet.

The "Bolts" you seek are rather large.. not screws.. that hold the wing..
and should be found behind the trim piece..

but when in doubt.. ask your mechanic to show things to you.

B

wrote in message
ups.com...
Our 172 has two screws missing from under the wing where
it connects to the fuselage above passenger door.

The size of those screws are quite big. My question is whether
they are important to the stuctural integrity of the wing ? They
may have come off during flight due to the vibrations. But it
is still some hours before the next 100 hours.

Are those screws important for holding the wing to the fuselage ?
or are they only there to cover the holes, and there are some
other bigger screws/nuts inside the wing that are doing the real
work ?

A speedy reply will be appreciated.

P S

They are where the wing and fuselage meet. What you said makes sense.
Those screws looked large compared with those on the household
appliances, but they are not that big. Google'd a bit and found
Sporty's
offering bags of exterior screws and washers, explicitly stating there
are
not interior structural parts.

Do these things fall off often ? like the fasteners in passenger
compartment
in cars.

But what can cause these screws to become loose one by one, over the
period of 3 months ? But no screws from under the other wing ? I
suspect
the AP in the last 100 hours didn't screw them in, if these needed to
be unfastened.

I called our AP and couldn't reach him. Will call again.

Thanks for the response.

P S

On Mar 10, 8:32 pm, "BT" wrote:
sounds like screws that cover the trim piece where the wing and fuselage
meet.

The "Bolts" you seek are rather large.. not screws.. that hold the wing..
and should be found behind the trim piece..

but when in doubt.. ask your mechanic to show things to you.

B

wrote in message

ups.com...

Our 172 has two screws missing from under the wing where
it connects to the fuselage above passenger door.

The size of those screws are quite big. My question is whether
they are important to the stuctural integrity of the wing ? They
may have come off during flight due to the vibrations. But it
is still some hours before the next 100 hours.

Are those screws important for holding the wing to the fuselage ?
or are they only there to cover the holes, and there are some
other bigger screws/nuts inside the wing that are doing the real
work ?

A speedy reply will be appreciated.

P S

On Mar 11, 2:44 am, wrote:
They are where the wing and fuselage meet. What you said makes sense.
Those screws looked large compared with those on the household
appliances, but they are not that big. Google'd a bit and found
Sporty's
offering bags of exterior screws and washers, explicitly stating there
are
not interior structural parts.

Do these things fall off often ? like the fasteners in passenger
compartment
in cars.

But what can cause these screws to become loose one by one, over the
period of 3 months ? But no screws from under the other wing ? I
suspect
the AP in the last 100 hours didn't screw them in, if these needed to
be unfastened.

I called our AP and couldn't reach him. Will call again.

Thanks for the response.

P S

On Mar 10, 8:32 pm, "BT" wrote:

sounds like screws that cover the trim piece where the wing and fuselage
meet.

The "Bolts" you seek are rather large.. not screws.. that hold the wing..
and should be found behind the trim piece..

but when in doubt.. ask your mechanic to show things to you.

B

wrote in message

oups.com...

Our 172 has two screws missing from under the wing where
it connects to the fuselage above passenger door.

The size of those screws are quite big. My question is whether
they are important to the stuctural integrity of the wing ? They
may have come off during flight due to the vibrations. But it
is still some hours before the next 100 hours.

Are those screws important for holding the wing to the fuselage ?
or are they only there to cover the holes, and there are some
other bigger screws/nuts inside the wing that are doing the real
work ?

A speedy reply will be appreciated.

P S


Those screw are likely #8 sheet metal screw with countersunk washers
used to hold the wing root trim panel on. You should check exterior
screws on access panels every couple of flight. The vibration wil
cause them to back out.

On 03/12/07 08:07, wrote:
On Mar 11, 2:44 am, wrote:
They are where the wing and fuselage meet. What you said makes sense.
Those screws looked large compared with those on the household
appliances, but they are not that big. Google'd a bit and found
Sporty's
offering bags of exterior screws and washers, explicitly stating there
are
not interior structural parts.

Do these things fall off often ? like the fasteners in passenger
compartment
in cars.

But what can cause these screws to become loose one by one, over the
period of 3 months ? But no screws from under the other wing ? I
suspect
the AP in the last 100 hours didn't screw them in, if these needed to
be unfastened.

I called our AP and couldn't reach him. Will call again.

Thanks for the response.

P S

On Mar 10, 8:32 pm, "BT" wrote:

sounds like screws that cover the trim piece where the wing and fuselage
meet.

The "Bolts" you seek are rather large.. not screws.. that hold the wing..
and should be found behind the trim piece..

but when in doubt.. ask your mechanic to show things to you.

B

wrote in message

oups.com...

Our 172 has two screws missing from under the wing where
it connects to the fuselage above passenger door.

The size of those screws are quite big. My question is whether
they are important to the stuctural integrity of the wing ? They
may have come off during flight due to the vibrations. But it
is still some hours before the next 100 hours.

Are those screws important for holding the wing to the fuselage ?
or are they only there to cover the holes, and there are some
other bigger screws/nuts inside the wing that are doing the real
work ?

A speedy reply will be appreciated.

P S


Those screw are likely #8 sheet metal screw with countersunk washers
used to hold the wing root trim panel on. You should check exterior
screws on access panels every couple of flight. The vibration wil
cause them to back out.


I'm always tightening screws during the pre-flight inspection.

Just yesterday I found a screw on the front of the cowling that was
backed about half way out.


--
Mark Hansen, PP-ASEL, Instrument Airplane
Cal Aggie Flying Farmers
Sacramento, CA

On Mar 12, 9:12 am, Mark Hansen wrote:
On 03/12/07 08:07, wrote:





On Mar 11, 2:44 am, wrote:
They are where the wing and fuselage meet. What you said makes sense.
Those screws looked large compared with those on the household
appliances, but they are not that big. Google'd a bit and found
Sporty's
offering bags of exterior screws and washers, explicitly stating there
are
not interior structural parts.

Do these things fall off often ? like the fasteners in passenger
compartment
in cars.

But what can cause these screws to become loose one by one, over the
period of 3 months ? But no screws from under the other wing ? I
suspect
the AP in the last 100 hours didn't screw them in, if these needed to
be unfastened.

I called our AP and couldn't reach him. Will call again.

Thanks for the response.

P S

On Mar 10, 8:32 pm, "BT" wrote:

sounds like screws that cover the trim piece where the wing and fuselage
meet.

The "Bolts" you seek are rather large.. not screws.. that hold the wing..
and should be found behind the trim piece..

but when in doubt.. ask your mechanic to show things to you.

B

wrote in message

oups.com...

Our 172 has two screws missing from under the wing where
it connects to the fuselage above passenger door.

The size of those screws are quite big. My question is whether
they are important to the stuctural integrity of the wing ? They
may have come off during flight due to the vibrations. But it
is still some hours before the next 100 hours.

Are those screws important for holding the wing to the fuselage ?
or are they only there to cover the holes, and there are some
other bigger screws/nuts inside the wing that are doing the real
work ?

A speedy reply will be appreciated.

P S

Those screw are likely #8 sheet metal screw with countersunk washers
used to hold the wing root trim panel on. You should check exterior
screws on access panels every couple of flight. The vibration wil
cause them to back out.

I'm always tightening screws during the pre-flight inspection.

Just yesterday I found a screw on the front of the cowling that was
backed about half way out.

--
Mark Hansen, PP-ASEL, Instrument Airplane
Cal Aggie Flying Farmers
Sacramento, CA- Hide quoted text -

- Show quoted text -

Those screws go into anchor nuts that have a self-locking
feature. The nuts wear out and don't hold the screw snug anymore and
vibration will shake them out. It's not a big deal unless enough of
them fall out that the trim starts beating around in the wind. It
could foul the flap, besides beat the windows up. Or make you mess
your pants.
The nuts need replacing, but the wing tank has to come out
to do it. Pain in the neck. Maybe a bit of Loctite on the screw would
do it. Use the Loctite 222 purple (low strength) stuff.

Dan

On Mar 10, 8:00 pm, wrote:
Our 172 has two screws missing from under the wing where
it connects to the fuselage above passenger door.

The size of those screws are quite big. My question is whether
they are important to the stuctural integrity of the wing ? They
may have come off during flight due to the vibrations. But it
is still some hours before the next 100 hours.

Are those screws important for holding the wing to the fuselage ?
or are they only there to cover the holes, and there are some
other bigger screws/nuts inside the wing that are doing the real
work ?

A speedy reply will be appreciated.

P S

My old CFI used to say that screws were used for things that were not
very important. Important stuff has rivets. I've mostly found that to
be true.

-Robert

On Mar 10, 10:00 pm, wrote:
Our 172 has two screws missing from under the wing where
it connects to the fuselage above passenger door.

The size of those screws are quite big. My question is whether
they are important to the stuctural integrity of the wing ? They
may have come off during flight due to the vibrations. But it
is still some hours before the next 100 hours.

Are those screws important for holding the wing to the fuselage ?
or are they only there to cover the holes, and there are some
other bigger screws/nuts inside the wing that are doing the real
work ?

A speedy reply will be appreciated.

P S

Those screws are for the fairing that covers the joint between the
fuselage and the wing. There is a long narrow fairing panel secured
with a 10 or 12 screws. The holes in the panel are quite large ( to
allow for variation in space between the wing and fuselage when first
installed) the screws are put in with countersunk washers to cover the
holes. The holes in the wing have #8 size Tinnerman nuts. These are
sheet metal type fasteners and take a type B sheet metal screw. A
type B sheet metal screw has a blunt point and a different thread
pitch than the more common Type A screw which has a sharp point.
These are not self locking nuts so the screws can back out over time
if not properly torqued. Type B screws will torque up properly many
times Type A screws will eventually damage the nut and lose torque
more easily. Some times a loose or damaged #8 tinnerman nut will take
a #10 screw for a while. Sometimes when the Tinnerman nuts are
completely stripped out they will be replaced with a Rivnut which is
an aluminum nut designed to be installed in a blind area. These take
machine screws so you might have a mix of both styles.

On Mar 13, 6:49 am, "John" wrote:
On Mar 10, 10:00 pm, wrote:





Our 172 has two screws missing from under the wing where
it connects to the fuselage above passenger door.

The size of those screws are quite big. My question is whether
they are important to the stuctural integrity of the wing ? They
may have come off during flight due to the vibrations. But it
is still some hours before the next 100 hours.

Are those screws important for holding the wing to the fuselage ?
or are they only there to cover the holes, and there are some
other bigger screws/nuts inside the wing that are doing the real
work ?

A speedy reply will be appreciated.

P S

Those screws are for the fairing that covers the joint between the
fuselage and the wing. There is a long narrow fairing panel secured
with a 10 or 12 screws. The holes in the panel are quite large ( to
allow for variation in space between the wing and fuselage when first
installed) the screws are put in with countersunk washers to cover the
holes. The holes in the wing have #8 size Tinnerman nuts. These are
sheet metal type fasteners and take a type B sheet metal screw. A
type B sheet metal screw has a blunt point and a different thread
pitch than the more common Type A screw which has a sharp point.
These are not self locking nuts so the screws can back out over time
if not properly torqued. Type B screws will torque up properly many
times Type A screws will eventually damage the nut and lose torque
more easily. Some times a loose or damaged #8 tinnerman nut will take
a #10 screw for a while. Sometimes when the Tinnerman nuts are
completely stripped out they will be replaced with a Rivnut which is
an aluminum nut designed to be installed in a blind area. These take
machine screws so you might have a mix of both styles.- Hide quoted text -

- Show quoted text -

The Tinnermans often lose one side of their "thread." The
steel is brittle and the thing will break off. There's the possibility
of a Rivnut but the Tin nut has to be removed first, and doing so will
leave loose bits rattling around under the fuel tank. Those bits have
a way of wedging into places they shouldn't be and will wear holes in
the tank. The better solution is to replace the nut, but the tank has
to come out. To do that, the tank has to be completely drained,
another pain.
Still, it's a better system than Citabria uses. They have
really short sheet metal screws into the root rib, and the compression
rib is just inside that root rib and gets in the way. The rib holes
strip out and won't hold the screws anymore.

Dan

Hi everyone,

On Mar 13, 7:57 am, wrote:
On Mar 13, 6:49 am, "John" wrote:



On Mar 10, 10:00 pm, wrote:

Our 172 has two screws missing from under the wing where
it connects to the fuselage above passenger door.

The size of those screws are quite big. My question is whether
they are important to the stuctural integrity of the wing ? They
may have come off during flight due to the vibrations. But it
is still some hours before the next 100 hours.

Are those screws important for holding the wing to the fuselage ?
or are they only there to cover the holes, and there are some
other bigger screws/nuts inside the wing that are doing the real
work ?

A speedy reply will be appreciated.

P S

Those screws are for the fairing that covers the joint between the
fuselage and the wing. There is a long narrow fairing panel secured
with a 10 or 12 screws. The holes in the panel are quite large ( to
allow for variation in space between the wing and fuselage when first
installed) the screws are put in with countersunk washers to cover the
holes. The holes in the wing have #8 size Tinnerman nuts. These are
sheet metal type fasteners and take a type B sheet metal screw. A
type B sheet metal screw has a blunt point and a different thread
pitch than the more common Type A screw which has a sharp point.
These are not self locking nuts so the screws can back out over time
if not properly torqued. Type B screws will torque up properly many
times Type A screws will eventually damage the nut and lose torque
more easily. Some times a loose or damaged #8 tinnerman nut will take
a #10 screw for a while. Sometimes when the Tinnerman nuts are
completely stripped out they will be replaced with a Rivnut which is
an aluminum nut designed to be installed in a blind area. These take
machine screws so you might have a mix of both styles.- Hide quoted text -

- Show quoted text -

The Tinnermans often lose one side of their "thread." The
steel is brittle and the thing will break off. There's the possibility
of a Rivnut but the Tin nut has to be removed first, and doing so will
leave loose bits rattling around under the fuel tank. Those bits have
a way of wedging into places they shouldn't be and will wear holes in
the tank. The better solution is to replace the nut, but the tank has
to come out. To do that, the tank has to be completely drained,
another pain.
Still, it's a better system than Citabria uses. They have
really short sheet metal screws into the root rib, and the compression
rib is just inside that root rib and gets in the way. The rib holes
strip out and won't hold the screws anymore.

Dan

I just found there were so many more helpful posts.
Very educational. I sure hope the parts broken off inside the wing
do not get caught under the fuel tank.

I flew that airplane. Funny thing is that when I took off, I was
a bit close to another small plane (1/2 mile), and got in its wake.
The plane shook and one wing dropped. I kept turning my
head to look at the right wing. Silly, but I couldn't stop
wanting a visual confirmation that that wing was still the-).

If we have to take out the fuel tank to fix those screws, it probably
will not be done until it is absolutely necessary. Will watch out
for the other screws around that area.

I bought a small screw/bit set, and will tighten the loose ones in
my next pre-flight.

Thanks much for all the insight.

P S