My mobile phone is from the ark. It makes calls and has a basic camera. That's it. I know lots of folk with 'smart phones', and one 'app' is an artificial horizon which I'm told uses a giro.
Could one of these phones be used as an emergency AI in a light aircraft?
I would say an absolute serious last-ditch emergency, sure - there are stacks out there, but useless if not calibrated. Pocket Horizon? (PockHorizon is the iPhone/iPad app) and maybe Spirit Level for a sort of slip indicator? Wouldn't like to use them on a dark and dirty though....
I don't think any of these actually work as they come with the phone.
For example this one
needs you to be flying straight and level and then you press a button to tell it so, and from then on it works as an AI... with a certain amount of drift because the accelerometers are not gyro-grade devices.
The basic issue seems to be of self erection 
An aircraft AI is self erecting. A vac one has the pendulous vanes; electric ones have either those or little weights which operate switches. These mechanisms provide a slow "background" erection mechanism which, on the (fair) assumption that mostly you are flying straight and level, delivers an AI which is "right" when you are not flying straight and level.
The AHRS based ones don't have any self erection (they detect acceleration only) so they use either airdata (constant baro altitude, constant heading, constant IAS) or GPS data (constant GPS altitude, constant GPS track, constant GS) to determine a likely "straight and level" condition and they use that instead to provide the slow background erection process. At least that's my understanding, based on what I've read. Obviously there is a weakness in that if you power cycle the system while flying straight upside down, it won't know the difference, but you have to make some assumptions
A workable AI is the "instrument panel" in say a Garmin 496. Provided you avoid any unusual attitudes, it does work. It determines the stuff from the GPS data alone.
There are some fixed AHRS to be connected to smartphones:
http://www.aviation.levil.com/AHRS_mini.htm
I haven't tried one yet
Their statement "guarantees a Zero drift per hour rating" suggests they do the background erection using some sort of static attitude sensor, because a "zero drift" gyro is obviously impossible, especially with AHRS technology which drifts quite a lot.
There are quite a lot of add-on boxes like that (walk around the Friedrichshafen show for example) but I don't think anybody has done it with just a phone by itself. I am not entirely sure why not because some phones do contain a "spirit level" function. My Pentax K5 camera has one too (only in one plane though). Obviously if it were easy then everybody would be doing it, because there are loads of "AI" apps for phones.
Could an Ipad be configured with an AHRS to give both attitude information and also synthetic vision? The illustration on that link seems to indicate that it is possible.
No doubt it can be (the hardware is obviously capable of running what is essentially a "flight sim" app) but you have a few hoops to go through e.g. there is no way to distribute a program for a (non jailbroken) Ipad except by making it available in the Apple shop, and to get there it has to pass the Apple politburo vetting etc.
There is probably another way because some high-end bizjets come with Ipads for interacting with some systems, and those apps are for sure not in the shop, so I guess Apple operate a "back channel" for certain high net worth users...
I also wonder how an Ipad would communicate with the AHRS module. Bluetooth is one option, on which there are no real restrictions on what data is passed. Wifi could also be used.
There is probably another way because some high-end bizjets come with Ipads for interacting with some systems, and those apps are for sure not in the shop, so I guess Apple operate a "back channel" for certain high net worth users...>
Peter, if you write an App you can simply load it onto your iPad/iPhone. End of story. That's how developers test theirs. You only go through the App store if you want to distribute your all-singing, all-dancing App to the world at large. Not necessary with an App that runs in a bizjet cockpit ;-)
If Apple have a say in this (at is it a commercial product after all), I don't know, however.
Fair point. So perhaps those bizjet apps are all simply signed to run on the particular Ipad(s).
The signature must be based on the device ID, otherwise you could just distribute the app to anybody...
Actually, what exactly stops somebody buying the Apple IOS developer kit, and simply custom-signing every app which somebody wants to buy, and bypass the Apple shop thus? That is how a lot of Symbian apps were sold: the developer asked for your IMEI and you got a custom-signed app.
Edit: found this which shows there is a way to develop apps for internal-company use.
I have the Levil AHRS and it seems to work well enough
