@STEVE
The ISIS is one display that takes the place of the Standby Instruments on older aircraft. It doesn't have a DG, it has a Ring Laser Gyro.
I think the ISIS message is because it lost valid inputs from its Air Data sources. These come from the Standby system ADMs (Air Data Modules that convert pitot and static to digital close to the probes/ports
)
maybe in Stockholm they feed an STANDBY SYSTEM with values from ADM's.
DESCRIPTION
The back of ISIS is fitted with two pressure connectors:
- One is connected to the standby pitot probe for total pressure
acquisition.
- The other one is connected to the left and right standby static probes
for static pressure acquisition.
ISIS is fitted with:
- One pressure module,
- one inertial module,
- one computation module,
- one display module,
- and one interface module.
The pressure module is connected to the total and static pressure
connectors.
Each pressure line is connected to a pressure sensor in the pressure
module.
The inertial module is composed of three single-axis rate gyros and
two acceleration sensors.
The computation module performs the computing and graphics
generation functions.
The display module is fitted on the front face of ISIS. It is of the
Liquid Crystal Display (LCD) type.
The front face is also fitted with
several knobs for operation purposes.
The interface module is composed of:
- a filtering board linked to an electrical connector at the back of ISIS,
- the 28VDC power supply unit,
- the interface board which links the pressure, inertial, computation
Thats why it is called STANDBY, apart from normal ADIRU SYSTEM 