BAe 125 Series 800
Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Instructor; Flight Crew Multiengine
Flight Crew Last 90 Days 36; Flight Crew Total 9500; Flight Crew Type 36
Human-Machine Interface; Training / Qualification
Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued Advisory / Alert; Aircraft Automation Overrode Flight Crew; Flight Crew Became Reoriented; Flight Crew Returned To Clearance
Human Factors; Weather
After being vectored to intercept the final approach course to the ILS 13R at Seattle Boeing Field; and having selected from a NAV intercept to what we believed to have been the approach mode; the aircraft began a left turn to rejoin the heading bug which was still in the ATC-assigned intercept vector position. Because of this the aircraft achieved an almost full-scale deflection off course to the left; which we immediately took action to remedy. Due to the 30-40 knot crosswind from the right; the 30 degree (re) intercept vector we established did not correct the deflection very quickly; and ATC advised we showed '1/4 mile' left of course. We advised we we're 'correcting' and no further discussions occurred. The result was a stabilized approach to an uneventful landing. Since 'Simultaneous Approaches' we 'in effect' to SeaTac; this could potentially have resulted in a TA/RA or similar to aircraft approaching SEA. There were none that we heard about. I submit this ASRS report to highlight this crew's lack of seat-time in type and the obvious impact this can have on automation management; with the intention of adding some data to that area of research. This was a clear miss-selection of navigation mode; accompanied by a delayed realization and identification of the mistake. This resulted in a good learning experience; but could also have resulted in a traffic conflict.
[Report narrative contained no additional information.]
HS125 flight crew new to the aircraft; report getting well to the left of the localizer before realizing a mistake in mode selection on the MCP.