Auburn, Washington RNAV GPS-A
STEEPER THAN NORMAL
The only IFR approach to Auburn, Washington (S50), is hardly a procedure anyone would consider straightforward, despite the airport’s 63-foot field elevation. Also known as Dick Scobee Field, named for the late Challenger shuttle commander, Auburn sits just a few miles southeast of the busy Sea-Tac Class B, while farther southeast the terrain rises to well over 14,000 feet approaching Mount Rainier. Be prepared for considerable GA traffic at Auburn, a known Sea-Tac reliever.
A. APPROACH NOTES
Notes are always important, and S50 has a pair of them. One warns pilots that the procedure is not authorized at night, while the other points to a steeper-than-normal 4-degree descent angle, steeper than the 3-degree rate most pilots expect during nonprecision approaches. This steeper descent angle demands a higher rate of descent to reach the minimum descent altitude in time.
A quick glance at the “Gnd speed-Kts” note offers a heads-up on the descent rate needed for a safe approach. If, for example, the procedure is flown at 120 knots, an 850-foot-per-minute rate of descent is required.
B. CIRCLING MINIMUMS
This Auburn procedure is considered a circling approach, despite a final approach radial of 331 degrees. While a GPS approach along the 331 radial will allow the pilot to descend eventually to 920 or 1,040 feet (depending on the approach speed), a pilot must wait until he or she has passed the final approach fix due to a radio tower sitting just outside the FAF that rises to 853 feet msl.
Due to local traffic, all circling must be conducted east of Runway 16/34 to keep from interfering with inbound Sea-Tac traffic. This actually puts the circle closer to the terrain to the east, and while it can look daunting, there is actually plenty of room.
C. THE RUNWAY
S50’s Runway 16/34 is just 3,400 feet long, another reason only circling minimums are offered for aircraft approach categories A and B. Importantly, aircraft with approach speeds greater than 120 knots are not authorized to conduct the approach. But with a short runway, larger aircraft with approach speeds greater than 120 might find it hard to stop on Auburn’s short runway anyway.
D. INITIAL APPROACH FIXES
Pilots navigating on their own may choose from one of two initial approach fixes, one at CIDUG, the other at ORTIN. Pilots selecting the path from CIDUG to ORTIN may skip the holding pattern as indicated by the “NoPT” notation northeast of CIDUG. Should the pilot choose to proceed direct to ORTIN as the initial approach fix, a trip around the holding pattern would be required.
E. MISSED APPROACH
A missed approach from this GPS approach requires a right turn back to ORTIN, where the pilot would enter the hold. Again, there’s more room laterally to the east than it might seem at first. Also worth noting is that the missed approach point is not actually over the runway itself, but rather ½ mile short of the approach end. Pilots watching the GPS count down to the MAP must remember the distance indicated is from the MAP. The airport itself is actually ½ mile farther north.
F. MORE ON MINIMUMS
A good case for never busting approach minimums can be made on the Auburn GPS. Remember that 853-foot radio tower adjacent to JISTA? The crossing altitude is, of course, more than 1,000 feet above that height. But if the aircraft broke out of the clouds just before reaching the FAF, the blinking lights ahead and beneath them could fool the pilot into thinking they’re seeing the runway end.