Annual Off to a Good Start

I'm using Torx on the plane I'm building in several access panel locations.

That is SO smart.

Is it illegal to subsitute Torx (or square-drive) screws in
certificated aircraft? If so, why?
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

"Jay Honeck" wrote in message
oups.com...
I'm using Torx on the plane I'm building in several access panel
locations.

That is SO smart.

Is it illegal to subsitute Torx (or square-drive) screws in
certificated aircraft? If so, why?

Nope.

Jim

Is it illegal to subsitute Torx (or square-drive) screws in
certificated aircraft? If so, why?

Nope.

Okay, that said, why is it that everyone (that I've seen, anyway)
continues to use the (too easily strippable) Phillips screws?

Inertia? Cost? No one has thought of it? No one else cares, cuz
their A&Ps do all the work?

It just seems so bloody obvious, yet I've never seen a certificated
plane with anything but Phillips screws.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

Jay Honeck wrote:
Is it illegal to subsitute Torx (or square-drive) screws in
certificated aircraft? If so, why?

Nope.


Okay, that said, why is it that everyone (that I've seen, anyway)
continues to use the (too easily strippable) Phillips screws?

Inertia? Cost? No one has thought of it? No one else cares, cuz
their A&Ps do all the work?

It just seems so bloody obvious, yet I've never seen a certificated
plane with anything but Phillips screws.

Jay,

I'm not sure if MilSpec Torx screws are readily available. I wouldn't
have a problem using N(ational)A(erospace)P(arts)A(ssociation) torx
screws on non-structural parts, but for the important bits, e.g. fuel
tanks and stressed skins, I just have never seen anything that would
qualify. I've been out of the maintenance arena for a few years,
though, maybe they are starting to show up?

Happy Flying!
Scott Skylane
N92054

Probably because no "airplane parts store" (including the highly respected
discounter o'them all, Chief) carries anything but Phillips.

Now that you've put the bug in my ear, I'm gonna order a bag of a hundred
each of the flatheads I use on the inspection plates and the pan
heads/flatheads that hold on the cowling. These two are the primary
offenders on The Manly HighWing 182. I'll be glad to order some for you if
you tell me the thread and the length. A point or B point? Stainless or
alloy? I don't go through the NAPA airplane store, but through an
industrial supply company that DOES have traceable parts.

I'm gonna replace stainless with stainless. They are a BIT harder and don't
rust up quite as bad. Stainless to speednut has never been a problem
insofar as I know.

Jim


"Jay Honeck" wrote in message
ups.com...
Is it illegal to subsitute Torx (or square-drive) screws in
certificated aircraft? If so, why?

Nope.

Okay, that said, why is it that everyone (that I've seen, anyway)
continues to use the (too easily strippable) Phillips screws?

Inertia? Cost? No one has thought of it? No one else cares, cuz
their A&Ps do all the work?

It just seems so bloody obvious, yet I've never seen a certificated
plane with anything but Phillips screws.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

Now that you've put the bug in my ear, I'm gonna order a bag of a hundred
each of the flatheads I use on the inspection plates and the pan
heads/flatheads that hold on the cowling. These two are the primary
offenders on The Manly HighWing 182. I'll be glad to order some for you if
you tell me the thread and the length. A point or B point? Stainless or
alloy? I don't go through the NAPA airplane store, but through an
industrial supply company that DOES have traceable parts.

Thanks, but I'm (hopefully) done with "screwing around" (sorry!) with
the access panels on my plane for another year. I'll look into it in
March '08, however.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

Probably because no "airplane parts store" (including the highly respected
discounter o'them all, Chief) carries anything but Phillips.
.stuff snipped

I'm gonna replace stainless with stainless. They are a BIT harder and don't
rust up quite as bad. Stainless to speednut has never been a problem
insofar as I know.

.other stuff snipped

Now that we have broached the subject, where do you find stainless
threaded speed nuts. There are a pile of them used on Cherokees to hold
on the wing/stabilator tips (8-32 I believe). I have never been able to
get a source.

Anyone?

Thanks,
Mike

My airplane (Diamond DA 40) uses stainless hex head cap screws for all
of the access plates and external fasteners. The only issue is that
they are metric, but Diamond was nice enough to include a set of
extras with the airplane. They are real easy to R&R, just had to get a
3mm hex bit for my electric screwdriver.

Mike Spera wrote:
Probably because no "airplane parts store" (including the highly
respected discounter o'them all, Chief) carries anything but
Phillips. .stuff snipped

I'm gonna replace stainless with stainless. They are a BIT harder
and don't rust up quite as bad. Stainless to speednut has never
been a problem insofar as I know.

.other stuff snipped

Now that we have broached the subject, where do you find stainless
threaded speed nuts. There are a pile of them used on Cherokees to
hold on the wing/stabilator tips (8-32 I believe). I have never been
able to get a source.

Anyone?

Thanks,
Mike

If one of these places don't have them they probably don't exsist.

http://www.gen-aircraft-hardware.com/

http://www.mcmaster.com/ (Not Aircraft but great none the less)

Jay Honeck wrote:
Okay, that said, why is it that everyone (that I've seen, anyway)
continues to use the (too easily strippable) Phillips screws?

The one problem I've run into with internal Torx screws (on cars) is
that if there is even a little bit of crud in the recess in the screw
head, the correct-size bit doesn't want to fit and the next size smaller
bit will feel like it fits just fine. If the screw is holding down a
piece of trim you can get away with it. If there's a lot of torque on
it, the too-small bit will strip out and maybe damage some of the lobes
on the screw head. The two ways around this are 1) make sure the screw
head is clean and 2) if you're not sure what bit a Torx screw takes,
once you've found one that seems to fit, get the next bigger one and
make a good effort to fit it in the screw head - don't use a hammer,
but do more than just hold it near the screw head and look at it.

Inertia?

Yep.

Cost?

Yep. I think any patents on Phillips had run out long before any
patents on Torx. On the other hand, you'd think if anybody would use
Torx, Cessna would, because at one point or another they are/were both
part of the same conglomerate, Textron.

No one has thought of it?

Nope. There is nothing new under the sun.

No one else cares, cuz their A&Ps do all the work?

Maybe some of that. I think your "average" GA pilot probably _knows_
more about turning wrenches than your "average" car driver, but that
doesn't mean they actually turn the wrenches themselves.

You might care more than the "average" because you're probably used to
doing maintenance things around the hotel, where you have a lot of
discretion on changing the design. If the nail keeps pulling out, use
a wood screw. If the wood screw keeps stripping out, use a bolt and a
nut. No paperwork, just your own judgement and "try it and see".

One factor may be support. Every A&P is guaranteed to have regular
and Phillips screwdrivers and bits. Torx may be common enough now
that the bits are in all the tool chests as well, but maybe not. If
you put a lot of Torx screws on your plane, it might be cheap and
light insurance to carry a set of Torx bits.

Personally, I think good-quality Allen (internal hex) screws are the
One True Screw[tm]. The drive tool doesn't slip out. They are older,
so the bits/drivers for them are more common. They are second only to
slotted screws in their ability to accept improvised drive tools - this
is a feature if you're trying to fix something while stranded at East
Armadillo Toe International Airport and a bug if you're the _next_ guy
to have to touch that fastener.

Matt Roberds