Sierra 24
Flight Crew Commercial; Flight Crew Flight Instructor; Flight Crew Instrument
Flight Crew Last 90 Days 100; Flight Crew Total 4000; Flight Crew Type 500
Training / Qualification; Situational Awareness; Confusion; Human-Machine Interface
Aircraft Equipment Problem Critical; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented
Chart Or Publication; Aircraft; Human Factors; Procedure
While inbound on the RNAV 17 approach into THV Harrisburg Approach advised me that I was 3-1/2 miles west of the final approach course; even though my instruments showed me on course and directly over the intermediate fix; which I reported to the Controller. My approach clearance was cancelled and I was instructed to climb; but since I was in visual conditions by that time; with the Controller's concurrence I continued to and landed at the airport visually.My GPS database was known to me to be out of date; but I had current approach plates aboard; had compared the plate to the approach in the database when I loaded it; and determined that; while the approaches were not identical; the intermediate and final approach fixes had the same name (WABEP and AZBIC; respectively); and the missed approach point was over the runway threshold for both approaches. On that basis; I concluded that the segments of the approach in my database that I would be using were identical to those of the current procedure. However; in the most recent amendment to the approach; the final approach course had been pivoted about the runway threshold eastward by fifteen degrees. The two fixes had been moved accordingly; but their names had not been changed.I wrongly believed myself to be in compliance with AIM 1-1-19.f; which states in part that a GPS approach in an expired database can be used if it is retrievable from the database and the waypoints are compared to the current chart. I inadvertently overlooked; in fact was ignorant of; the further requirement to verify that the procedure had not been amended since the database's expiration date. (Note that the AIM is ambiguous as to whether a current database is required to fly a GPS approach. Subparagraph 1(c)(1)[a] of AIM 1-1-19.f states that the database must not be expired; while footnote (3) to AIM Table 1-1-6 allows use of an expired database subject to the previously described verification.)Although it does not excuse my omission to compare database and approach amendment dates; I would have caught the error and not used the retrieved procedure if WABEP and AZBIC had been renamed when they were moved; or alternatively that new approach fixes with different names had been created. It is disconcerting to learn that; as AIM 1-1-19.b.3.(b)(3) states; '. . . waypoints are added; removed; **relocated** or re-named as required to meet operational needs [emphasis added].' The fact that waypoints and fixes can be; and apparently are; relocated without re-naming renders the subparagraph 1(c)(2)[b] inflight determination 'that the waypoints are generally logical in location' useless and; as my experience illustrates; potentially misleading and dangerous. Moreover; there is no practical way inflight to perform a subparagraph 1(c)(2)[c] 'verification of latitude and longitude' of approach fixes; as this information is not routinely available to pilots. Even on the ground and with internet access and no time limitations; I have not been able to locate an official source of approach fix coordinates.If not using a current database (a very common practice); a pilot should always check the date of the approach procedure amendment against the date of the database. As it turns out; this appears to be the most important GPS approach verification procedure of all.The FAA should absolutely abstain from moving IFR waypoints and fixes without renaming them. If it's necessary to put a waypoint in a new location; it is also necessary to clearly distinguish it from the old location. In the confines of the cockpit in flight; the pilot must be able to rely on his verification of fix names; because it is impossible; as a practical matter; to verify fix locations in any other way.
The pilot of a BE-24; flying with a known out of date GPS database; attempted to fly the THV RNAV (GPS) Runway 17 approach utilizing the database and was advised by Approach Control he was 3.5 miles west off course while showing on course. After the fact he determined the approach waypoints were still identified by the same names; but the inbound course had been altered 15 degrees to the left of that in his expired database.