Eric Greenwell wrote:

I'm under the impression that the cylinders we use in our gliders are
NOT classified as aircraft components, but are, instead, considered
"portable" equipment. To be aircraft components, the glider would have
to be certified with an oxygen system, and none of them are.

This MAY not be true. The FAA reference in Sect 3(Guidance), para D(4)
says:
Any cylinder that is part of a supplementary oxygen system,
that in the course of its normal operation is gradually
depleted, may remain in service if it meets the operational
requirements in 14 CFR § 91.211, Supplemental oxygen.

I would have thought that the oxygen systems we use in gliders are the
same conceptually as the portable cylinders carried on most commercial
airliners for crew use in the event of a decompression. I thought (but
could be wrong) that these were "supplementary oxygen systems"? If so,
DOT markings are unnecessary. I flew with an airline for some years but
I don't recall seeing DOT marked on any of the portable cylinders on the
flight deck.

...What we do
is (I believe) no different than the airplane pilot that carries on a
cloth bag with the cylinder and regulator in it, then uses the seat belt
to strap it down next to him. In other words, our gliders do not have
oxygen systems in them, just carry-on baggage that happens to be an
oxygen system.

If true, then the cylinders have to meet the regulations for carrying
these cylinders around in cars, busses, etc, which would be DOT
regulations.

I'm not sure about that. If we forget how it came into your possession,
the FAA reference in 2(Background) says:

C. Title 49 CFR parts 171 through 180, Hazardous
Materials Regulations (HMR), pertains to the retest
and inspection of cylinders in transportation in
commerce. However, cylinders used as components in
aircraft are not considered to be in transportation in
commerce when installed in an aircraft.

That seems to me to imply that carriage as a supplementary oxygen system
in an aircraft does not qualify as "transportation in commerce". Again,
DOT regs would be inapplicable.

I recall once that a request from our navigators to have a pencil
sharpener clamped to the edge of their table was refused because that
would "install it" in the aircraft. Drawings would have to be drawn,
stress calculations made, Engineering Orders would have to be approved.
A maintenance schedule would need to be developed, transit
qualifications and MELs would have to be considered. I think they were
each issued with pocket sharpeners.

Bush lawyer anybody?

Graeme Cant