Just to be clear, I wasn't making an endorsement, I was
 just passing on
 the info FYI so to speak. I have used tablet computers
with
 conventional
 hard drives up to 17,000 ft with no problems. Your results
 may vary.
 C. Smith

 That is interesting. Perhaps they have the problem solved.
 What brand? As I understand it the read write head
 "flies" over the surface
 of the disk in ground effect. The theory is the air
density
 needs to be
 reasonable for this to happen. An airplane speeds up and
or
 increases the angle
 of attack to fly at higher altitudes to make up for the
 lower air density.

 --------------------------------------------------------
 Here is a web site on the subject and a recent patent.
 http://www.pcguide.com/ref/hdd/op/heads/op_Height.htm

 Lots of people want to use notebooks with moving map
 software
 as it is 1/10 the cost of aviation moving map software.
 I wrote my own years ago and I used a floppy disk to store
 the FAA airport data base. :)

 The Home Built Glass Cockpit by Paul Lamar
 Kitplanes
 June 1988 page 69
 The future can be here now: electronic
 instrument displays in your homebuilt.

 Glass Cockpit: Part II by Paul Lamar
 Kitplanes
 January 1989 page 66
 Automatic position reporting could be helpful
 when pilot's hands and mind are full.

 Paul Lamar

 I ran tests with the Itronix brand tablet, a couple of
 years back.
 I was flying my 182T. We ascended to 17,500. Stayed there
 for an
 hour and a half, running flitesoft from RMS technologies,
 linked
 to a gps, and XM weather reciever. in the background I was
 running
 a continuous hard drive testing utility. I can't
 remember the drive
 maker off the top of my head. No problems. Also ran a
 Motion (LS-800)
 computing tablet on a long cross country form howell,
 Michigan to
 Phoenix and back, return trip we  ascended to 19k for a
 while to
 take advantage of the tail winds, then my oxygen hose
 popped it's
 fitting, and we flew the rest at around 12k, landed in
 Oklahoma
 for gas, and get my blood oxygen back to normal. No
 problems with
 either one.

 What you say about the drives is still true, the head
 floats on
 a film of air, just that I didn't have any problems. I
 ran the
 testing because I was planning to try to market the
tablets
 to
 the aviation community, when solid state drives were not
 readily available, and I felt that the technology had
 improved
 (there is mil-spec testing criteria on the General
Dynamics
 website)
 and that much of the altitude and hard drives don't
mix
 talk
 was "I once knew a guy who talked to a guy who walked
 past a
 bar where he heard someone say...." I'm sure that
 there is
 some altitude where the drive will become unreliable, I
was
 just unable to find it myself, and it probably varies with
 manufacturer and model of drive.
 Again, your results may vary.
 C. Smith


Paul, I would like to note that it appears the website you
reference was last updated in 2001. The reliability issue
and altitude is like trying to break the perception that
Detroit still makes junk. It just doesn't seem to go
away.
I did not have the resources to make a hard scientific
study,
with lots of testing and data to back it up. Just personal
observation. However that isn't enough to alter the
perception,
we didn't sell any computers to pilots of unpressurized
aircraft.
My contention was that we don't generally operate where
solid
state becomes necesary and current technology hard drives
will
be serviceable for 90% of unpressurized GA missions.
C. Smith

The Hitachi pdf was 2007 and the patent was jan 2008.
A definitive test would be a vacuum chamber and a shake
table.
Of course the sealed hard drive solves the problem no
doubt.

Paul Lamar

Hmm. From what I can determine in reading the patent is that it
applies to a method for determining (measuring) the flying height
of the head, whereas the patent mentions that "there have been
developed heads that include a heater coil". It goes on to state
that the FOD heads have in the past been opticly calibrated, and
the pattent is for an "in-situ" method to calibrate the flying
height within the drive.

It looks to me that the ability to control to some extent the
flying height of the head was developed some time ago, prior
to this patent. That may account for my experiences of satisfactory
hard drive performance at altitude, and this is an improvement
upon that. Technology marches on.

Now that I am reading this, I believe that both drives were in
the tablets were Hitachi's. I took a photo of the system info
screen of the itronix just prior to selling it off, I will see
if I can dig it up to confirm the drive manufacturer.
C. Smith