Mao 1
I think the vacuum failure ASI incident must have been confused with the day he/she had a pitot static problem. On that occasion the DI and AI were all over the place and it was impossible to maintain straight and level flight. Fortunately the GPS still worked, thus avoiding imminent danger to schools and hospitals.
Warning to instructors - do not ever attempt to cover the flight instruments with stick-it notes or similar to show your students that flight by reference to the horizon is possible. It is not. Modern aircraft require, as a minimum, the following:
Glass panel PFD and MFD (e.g. Garmin 1000/600/500)
Autopilot
Twin G430/500
FADEC
and failure of any of these is not possible because the manufacturers guarantee their 100% reliability.
http://www.aaib.gov.uk/cms_resources...AB%2009-09.pdf
BJ