Originally Posted by az_gila
Steve, if I am using a G5 as an independent back-up instrument without any other electrical connections in or out to any other data source, how important is the GPS function?
Is it simply an automatic backup if the pitot pressure fails?
The simple answer is yes, having a source of GPS data, internal or external, is important to allow the G5 to perform at it's maximum potential.
While the G5 is not TSO'd, we designed the G5 to meet the TSO-C201 performance requirements.
The TSO-C201 performance requirements are specified for both "normal" mode and "degraded" mode. Each manufacturer is allowed to define what is normal mode for their product, and for the G5, normal mode relies heavily on GPS data for maximum performance to avoid being dependent on air data which could suffer a blocked pitot. One of the reasons we designed a high performance WAAS GPS receiver into the G5 was so it could independently perform at the highest level with no reliance on external GPS sources.
The G5 meets these performance requirements both with GPS (normal mode) and without GPS (degraded mode), but the accuracy requirements for degraded mode are a little less stringent.