On Tuesday, April 28, 2015 at 8:54:14 PM UTC-7, wrote:

Take your alternative systems into a dual aircraft and put some real blinders on and see how you do.

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You cannot accurately touch virtual buttons on your smartphones while tumbling inside a cloud.

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You cannot wait for a system to boot from a cold start.

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Your rational mind will not be working when you try to understand how a compass, ASI, and bubble need to be responded to when you have not practiced this over and over and over.

Bubble tells you nothing that yaw string doesn't (unless yaw string is frozen.) These three things are indeed enough under certain very exceptional circumstances (involving smooth air and freedom to choose heading according to what works with the compass, rather than terrain.) In most real-world circumstances you need much more. If wind is in same ballpark as airspeed, that "something else" had better not be a simple GPS-based map display or "heading" indicator or GPS-derived "bank angle" indicator. An ARHS-based artificial horizon display is great, running on vario or on some sort of RELIABLE, hard-mounted tablet etc. I'm having trouble believing the reliability is really there with most cobbled-together systems, but don't know that much about it. I noted another option on related thread "Emergency instrumentation for cloud encounters": http://store-vllhq23n.mybigcommerce....-in-enclosure/ . Same basic concept as TruTrac which is another option. Either of these is an instant-on or rapid-on piezoelectric turn rate sensor.

S