Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Aircraft Equipment Problem Critical; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued New Clearance; Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Returned To Departure Airport
Aircraft; Software and Automation
Scheduled flight was a completion test flight of a new Gufstream 650ER by the OEM from ZZZ. Brief; start; and taxi were uneventful. Immediately after takeoff from Runway XX; the PIC experienced a failure of the primary attitude reference and erroneous airspeed and altitude indications in the Heads Up Display (HUD) and the Pilot's Primary Flight Display (PFD). Initial assigned altitude was 3;000 ft. Approaching assigned altitude it became apparent that capturing and holding altitude would be difficult so a block altitude of 3;000 to 5;000 ft. was requested by the copilot and assigned by ZZZ Approach Control. An altitude of approximately 3200 to 3300 ft. was reached prior to ZZZ Approach Control granting the requested block altitude. ZZZ Approach Control vectored us for an uneventful ILS approach to landing on runway XY at ZZZ.
[Report narrative contained no additional information.]
G650 flight crew reported erroneous airspeed and altitude indications after takeoff.