It may be that current technology is not up to the task we're discussing, but it may just be though. If not now, certainly soon. But now it should be good enough to give the crew decent gen in a calamity than the current state of the art, as emergency data?
Don't just put GPS unit on the extremities, put IRS units there too. I know its hardly a comparison to what will be needed, but imagine an iPhone on each wingtip, the nose and the tail. The accelerometer data is not for navigation, so 0.3 ANP etc isnt relevant. It's for attitude info only, realtime. The more accurate the GPS the better, and each system would complement the others and make it even more accurate.
Lets think a bit about this, we need..
EADI - derive attitude from the system I'm talking about (lets call it 3AE, 3 axis at extremities)
VSI - derived from GPS
ALT - derive from GPS
HDG - derive from GPS
ASI - derive anticipated airspeed (ie. What it would be if not acted upon by wind gusts) by calculating what airspeed should be at calculated attitude with known thrust setting at given altitude (temp you'll need a probe). Mach data by referring to temp and TAS (more about which to come!)
To adjust for immediate windspeeds, possibly use very accurate doppler radar which will reveal the speed of water particles in the air in the case of 'wet gusts' , and to measure the speed of dry gusts, the aircraft could issue a high pitched sound of a given frequency from the nose, receive it in the tail and wingtips, and using doppler effect calculations by comparing the frequency difference at reception could determine the speed of the air passing by the aircraft, like hearing a whistling train go by. I'm not sure how mach compressibility effects might upset this, perhaps someone here does.
Because a gust will not hit all parts of the aircraft simultaneously, if the 3AE system is accurate enough it would be able to compare how the airframe has responded in realtime to a database of known possibilities. Very very simplistically, if the left wing lifts suddenly before the right, and the aircraft then yaws left more than is usual and climbs, it compares it to the database test data which says, yes, that gust was from X bearing and direction. Speed of gust calculated by micro-time between motions of extremities.* We're talking vast computer power here, but it is available. The latest mobile phone chip can do a teraflop of throughput, which is what the worlds fastest supercomputer could do in 2000, only 14 years ago.
Combining these different results with each other will make the final result more accurate, as will analysing instantaneous changes in groundspeed (GPS) and adding that to the mix. The clues are all there, we just have to link them all up like a high speed detective case. Sounds silly but thats essentially what it is.
There we have our blind flying instruments back.
We know the crew shouldn't be faced with conflicting data and spurious alarms. If crucial data is lost, or if the data falls in the defined to be rubbish category, the computer needs to make up for its loss and not either just jack it in or pull some dangerous kneejerk move. At worst it needs to do nothing and display "Stand by!" leave all controls in last setting including engine controls, and display the known required pitch attitude on the EADI for that power setting for level flight at the aircraft's altitude and weight until the crew make a decision and intervenes, or good data returns.
The 3AE system could display the aircraft from a 3rd person view, in 3D as a friend of mine on here recognised. The pilots could watch themselves spinning. (Airline livery obviously a manufacturer extra!) You could even view yourself landing it from a lateral perspective. Its really now just a big computer game with a real plane attached, all the data is there, we just couldnt use it before because it took such processing power, and such accurate instruments. It may not surprise some of you that nowadays its possible to take photographs at a rate of one trillion frames a second, fast enough to freeze a photon. There's yet another solution to the no pitot tube problem - measure the progress of particles in the airstream using this technology...we're back to casting a log overboard and measuring the knots
