1. Training
2. Tier 2 Approach
3. Hillsboro NDB-B Approach

Hillsboro has a couple of non-precision approaches. For this example, we'll focus on the NDB-B Approach. NDB stands for Non-Directional Beacon.

First, we'll focus on how the aircraft navigates to the airport, after that we'll focus on the altitudes the aircraft should fly, and finally, we'll give you an example transcript of pilot/atc communications.

Navigation:

Aircraft with an Automatic Direction Finder can tune into the BANKS NDB and fly directly to it. This is the Initial Approach Fix (IAF). Unlike a VOR, it has no radials to intercept, so you can only clear an aircraft "direct Banks".  The aircraft will know they've reached BANKS as their directional needle will "flip" from a to arrow to a from arrow. Once that happens, the aircraft will turn the bezel (the ring around ADF with degree markers) on his ADF to 302 degrees and fly outbound for a couple of minutes (the number of minutes depends on aircraft speed). The aircraft will then turn left 45 degrees (or in this instance a heading of 77 degrees) and fly for 1 minute, then turn right 180 degrees. After completing this turn the aircraft has reached "Procedure Turn Inbound". He will then adjust his bezel to a heading of 122 degrees and when the ADF needle aligns, he turns right to a heading of 122 and should be on course heading directly to the NDB. 

CLICK HERE TO VIEW KHIO NDB-B

Now the NDB isn't at the airport, but about 6 miles away. The aircraft will again pass over the NDB on his way to the airport, once the needle "flips" again he's at the Final Approach Fix (FAF). The pilot will start his timer. On the approach chart, there's a table that shows, based on the aircraft speed, how long they can fly until they MUST have visual on the airport. This point in space (based on time from the FAF) is called the Missed Approach Point (MAP). 

Altitudes: 

In the chart, you can see that the aircraft must pass below 6,000ft at the BANKS NDB, but above 3,600ft (his procedure turn minimum altitude). After the procedure turn the pilot must maintain at least 3,200ft until he passes back over BANKS inbound to the field. After passing BANKS inbound he can then begin his descent to either 900ft or 960ft depending on his aircraft category, but never below that altitude. He can continue at this minimum altitude until he reaches the Missed Approach Point.

If the aircraft doesn't have the field in sight by the missed approach point, he must execute the missed approach as depicted in the upper right-hand corner of the chart above. The missed approach instructs the pilot to climb to 1,000 ft, then turn right climbing to 3,000 ft direct to Newburg (UBG) VOR and hold as published (see navigation chart above).

If the aircraft has the field in sight, then he will follow the tower's instructions on how to circle to enter the pattern for the active runway. Although the NDB approach puts the pilot on a straight-in approach for runway 12 (within 30 degrees), the NDB is not located on the field, and therefore, he must still be given "circling to land runway 12" because the pilot may or may not be directly aligned with the runway.

For more information on reading approach plates, visit http://www.navfltsm.addr.com/ndb-appr.htm

Sample Transcript:

Assumptions: the aircraft is airborne somewhere about 3 miles south of the Portland Airport at 4,000ft. 

PDX_APP: N63022, cleared direct BANKS. Hillsboro altimeter 30.12

Note: If the field is reporting IFR, you must also give the pilot the visibility and cloud conditions, or ask the pilot to verify he has the current weather for HIO.

N63022: Cleared direct BANKS, N63022

PDX_APP: N63022, cross banks at 4,000. Cleared NDB-B approach, circle to land runway 20. Report Procedure Turn Inbound

N63022: Cleared for the NDB-B approach, cross BANKS at 4,000. will report Procedure Turn Inbound.

N63022: N63022 is Procedure Turn Inbound

PDX_APP: N63022, Contact Hillsboro Tower on 119.3

N63022: Over to tower, N63022

N63022: Hillsboro Tower, N63022 on the NBD-B inbound

HIO_TWR: N63022, Hillsboro Tower, report field in site to circle north of the field to enter a right base for runway 20

N63022: Will call you field in sight to enter right base for runway 20 for N63022

N63022: N63022 has field in sight

HIO_TWR: N63022, wind 190 at 9, runway 20, cleared to land

N63022: Cleared to land runway 20, N63022

If aircraft doesn't have the field in site:

N63022: N63022 is going missed

HIO_TWR: N63022, Contact PDX_APP on 124.35

N63022: Going over to approach, N63022

N63022: PDX_APP, N63022, Missed approach at Hillsboro

PDX_APP: N63022, PDX_APP, Ident

PDX_APP: N63022, Radar Contact. climb and maintain 3,000. Say intentions