10540
Partial Panel is tested on Licence renewal but usually only on some of the smaller types. It is limited to basic exercises and does not include any approaches.
Trials in simulators, carried out in the USA, giving unexpected Vacuum Pump failures to experienced, but unsuspecting crews, frequently resulted in disaster.
There have been a sucession of accidents, here in the UK, following Instrument failures (for whatever reason). The latest and most notable, of course, being the Beoing 747 at Stansted.
In my opinion an instrument failure in IMC (for whatever reason) is an extremely serious event.
Quite a few aircraft cleared for "real IFR" as you put it do not have a second Artificial Horizon of any description, even though they may have two engines! In this case they will, of course, have two Vacuum Pumps, but what about the singles??
UV