Yes, this jittering problem apparently results from that these sensors are not sampled synchronously with the application. A stable support is probably necessary to get a good picture of the sky in sync with sensor data. Also, most PEDs provide, by default, rather low refresh rate; for instance my Sony apparently samples its sensors somewhere around 30 Hz whereas if told to do so as fast as possible, the rates are in order of 350 to 400 Hz (not really usable for any vibration analysis for instance, but easily good enough for simpler purposes).
Somewhat off-topic, there have been some glass cockpit retrofits available for many years that are based on MEMS gyroscopes, in principle similar to the ones used in PEDs for measuring angular rates. I was loosely involved with one such installation many years back. It replaced the primary attitude gyro and the HSI in Piper Archer or Warrior, I don't remember which. I did find it somewhat dubious, even if the operators liked it. I wondered how the sensors could keep their ups and downs in constantly vibrating and shaking environment of a single-engine piston aircraft. Your regular vacuum gyro is biased towards vertical: it slowly uprights itself, often within some limits. This means that if you fly in circles for long enough, your attitude indicator ends up showing some bank after you level out. The electronic MEMS gyros were probably treated similarly. The shocker came when we were doing the altimeter tests. When the static tester was adjusting for different altitude equivalent ("climbing" or "descending"), the attitude indicator went nuts. Very steep climb or descend attitude was shown. The attitude fail flag soon came out. When the new "altitude" was reached, the indications soon returned to normal.
The system used barometric vertical speed to bias the pitch indication! I don't remember if this was explicitly documented anywhere. Probably only the designers themselves knew how it really worked. While I generally dislike vacuum gyros, in that occasion I was silently glad that this was probably one of the few PA-28s with triple-redundant attitude indications, for it retained the original co-pilot's vacuum AI and the electrical backup attitude indicator.
-Esa
Would you be interested in realistic celestial navigation?
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- Senior Airman
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Re: Would you be interested in realistic celestial navigation?
Good times! That's interesting stuff to test, but I'm with you... unless we're talking real IRS or AHRS, I'll take redundant gyro instruments over the science project stuff .
Re: Would you be interested in realistic celestial navigation?
Yeah that was one of the early, fully IFR-certified retrofit glass cockpits. 'Proper' IRSes are usually found rather high in the food chain. Even lighter business jets often do without.Stearmandriver wrote: ↑08 Dec 2019, 23:54 Good times! That's interesting stuff to test, but I'm with you... unless we're talking real IRS or AHRS, I'll take redundant gyro instruments over the science project stuff .
-Esa
Re: Would you be interested in realistic celestial navigation?
Thought some folks would be interested in this free add-on just released for MSFS. Now all we need is the A2A Connie for MSFS!
https://www.avsim.com/forums/topic/6032 ... -on-guide/
Mike
https://www.avsim.com/forums/topic/6032 ... -on-guide/
Mike
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