http://www.androidzoom.com/android_applications/productivity/aircraft-horizon_zcuz.html

 Robin Bergland.

 That would be worth buying a small Android tab just for that.

 http://www.everbuying.com/**smlclass854.html?gclid=**
 CJr9qfbE7awCFUWMtgodigzI9A<http://www.everbuying.com/smlclass854.html?gclid=CJr9qfbE7awCFUWMtgodigzI9A

 Paul Lamar


 I know many phones and tablets can sense which way is down to
 determine portrait or landscape orientation of the display but that
 is a single axis sensor.  How does he get roll AND pitch?  i am suspicious!

 SD

 I suspect the sensors are 3 axis.

 There is an ap out there where you can look at the night sky and identify
 star names by merely tilting the tab back and fourth pointing it in
 the direction of interest. It also uses the GPS to locate one on the
 planet.

 Paul Lamar



It can do all of that stuff with just 3-axis accel, compass, and GPS. To
get "real" horizon info and not just a toy that works while you're standing
on earth, you need a gyro. I believe some phones may have a MEMS gyro, but
that software only claims to use the accelerometer, which is a flawed
method.

-Chris W

It sure keeps my toy helicopter flying straight.
A lot depends on the A to D used. A 16 bit A to D is one part in
65,000 more or less. In terms of percentage that is .0000153% I think.

Having said that I don't know what the A to D is but 12 bits are very
common and cheap. One part in 4096 or .000244%.  Modern CPU chips found in
desk tops and tabs have enormous computing power.


Paul Lamar



The big problem is long term drift..  A MEMS can provide something
that's close, but you may get slow roll, yaw, and pitch errors.  These
can be zero'ed by a variety of methods, but can't be ignored.

The RC helicopter takes trim input from you - you know if it's yawing
by looking at it.  If you're in the clouds, you don't have that
benefit.

It's common for AHRS devices to get drift correction from a
magnetometer (electronic compass).  Something which many of the
iDevices have.

It's also possible to use GPS to provide drift correction.

Consider that the device's drift characteristics will likely change
over Voltage and Temperature, and that each device may have somewhat
unique behavior.  Having a robust drift correction strategy is
important.

I think MEMS and other means of providing low cost attitude control
are great.  I just don't think tablet computers or iPhones are robust
enough.  That they aren't designed for this kind of thing means you
don't have control over quality of either the software nor the
hardware.  Everyone I know that has Android devices spends a fair
amount of time staring at them with a furrowed brow, wondering, "Why
did it do that??  Again?"  Apple stuff is a bit better (because of the
closed architecture), but it's still not perfect.

Paul, you know how you don't like computerized EFI written with C
because it's too complex and difficult to control to the last nth
detail?  I feel the same way about C based devices for flight
instruments.  Anything you have to reboot fairly regularly doesn't
have a place as a piece of the primary flight instrument puzzle.

PDA based moving map might be OK.

Regards,

Matt-


I think the multi sensor approach is the way to go. I mentioned that in one
of my messages above.

 "IMHO combining the GPS with the rate gyro info can produce a good attitude
 gyro and is not out of the question for an experimenter on here (once one
 learns AVR asm :)) to build using a cheap $30 microcomputer board with A
 to D's.

 Assuming for the moment the throttle is fixed and the GPS speed is
 increasing the aircraft is diving.  If the GPS is telling you there is a
 heading change and the readings for the yaw rate gyro and roll rate gyro
 are significant you know the roll angle assuming a coordinated turn.  One
 can then get data from the ball in a turn and bank in an uncoordinated
 turn.  If the GPS says there is no speed change and and no turn you are
 obviously flying straight and level.  Other parameters that could be
 monitored is the manifold pressure and RPM to detect a change in power.

 The basic idea  here is take data in from multiple sensors (not just the
 rate gyro's) and use logic and reason to determine what the pitch and roll
 angles are.

 The classic mechanical attitude gyro uses only one sensor, namely the
 spinning flywheel."


I would not use if for IFR but for everyday VFR I think it would be OK.
I am not IFR rated anyway.

Paul Lamar