Approach Clearances

This article has been corrected to address an error regarding the KLATU and HIKES fixes.

One of the most critical communications from ATC to an IFR aircraft is the approach clearance. Unfortunately, it’s often read at breakneck speed while the pilot is scrambling to maneuver the aircraft onto the approach course, turning to a new heading and descending to a new altitude.  

FAA Order 7110.65 gives a very specific formula for the controller to use, but my experience giving the IPC (Instrument Proficiency Check), not to mention just listening to the frequencies, suggests many instrument pilots don’t know exactly what the controller is supposed to be telling them and how to sort the wheat from a large pile of chaff. It doesn’t help when the pilot doesn’t have a clear understanding of the rules about leaving the last assigned altitude in conjunction with beginning an instrument approach procedure. 

It’s worth mastering because there’s a lot at stake. A long time ago a disconnect between an airline crew and a controller over an approach clearance killed 92 people.

Elements of an Approach

There are several elements to an approach clearance, some of which may be omitted when certain conditions are met. The full list:

• Distance from the first point on the approach to be crossed and the identification of that point.
• Heading or routing to join the approach.
• Altitude to maintain until established on the approach.
• “Cleared” or “cleared straight in.”
• Approach name.

There are two ways a controller can get you onto the approach: pilot nav or vectors. For pilot nav, you must already be established on a published route that connects to the approach or able to navigate direct to an allowable entry point on the approach, like an IAF or IF. That navigation could be either using a ground navaid or RNAV system like GPS.

Say you’re established southbound on T335 at 4000 from Smyrna (ENO) 7 miles north of EZIZI to land at Salisbury, Maryland (KSBY) using the RNAV (GPS) RWY 23 approach. The controller can say, “N12345, you’re 7 miles from EZIZI cleared RNAV 23 approach” without any further routing or altitudes. No routing is needed because T335 leads to EZIZI, which is an initial approach fix for that approach, so you simply stay on that airway to EZIZI and then follow the initial segment from there to OKKOE and continue on the approach. No altitude is needed because you’re already on a published segment (T335) with a published minimum altitude (the MEA of 1700) so you could immediately begin a descent to 1700 feet. Of course, as you reached EZIZI, you’d have to climb back to the published 2000 feet for the initial segment, so stopping at 2000 feet would probably make sense.

On the other hand, if you’re not on T335, the controller could clear you direct to EZIZI and clear you for the approach. The difference here is that the controller would have to give you an altitude to maintain until you reach EZIZI.

This also works for points on airways that are designated fixes for a transition route to an IAF, such as HIKES intersection on V276 for the RNAV(GPS) RWY 11 approach to Quakertown PA (KUKT). HIKES is not part of that approach, but there is a segment from HIKES to the IAF (KLATU), and since it has a course, altitude, and distance, it is a “published route segment.” If you were westbound on V276 at 6000, the clearance could be, “N12345, 6 miles from HIKES, cleared RNAV 11 approach,” and you could immediately descend to the V276 MEA of 4000 to HIKES and then after HIKES down to 2700 to KLATU. (Fans of old science fiction movies may recognize the fixes on this approach from the 1951 sci-fi thriller The Day the Earth Stood Still as the Earth-saving phrase Michael Rennie gives to Patricia Neal to say to his robot Gort: “Gort – Klaatu barada nikto!”)

Vectors to Final

The second possibility is vectors to final (VTF). This is probably the easiest for the pilot since they need only fly the controller-issued heading to intercept the final approach course (FAC) and then proceed on the approach. For a controller to issue vectors to final, several conditions must be met:

• The FAC must be depicted on the controller’s scope. You may not be able to get VTF when an Air Route Traffic Control Center (ARTCC) owns the airspace rather than a Terminal Radar Control Facility (TRACON); FACs are often not depicted on ARTCC equipment.
• The FAA limits the intercept angle to 30°. International Civil Aviation Organization (ICAO) standards allow intercept angles of up to 45° degrees.
• The final vector must put the aircraft through the final approach gate on the scope outside the final approach fix (FAF). This is depicted by a symbol that looks like football goalpost 1 to 2 miles outside the FAF.
• The last assigned altitude must allow glideslope intercept from below.

A point of occasional confusion is when the controller gives you “vectors for the approach” rather than “vectors to final.” “Vectors for the approach” take you to where the controller can clear you direct to a fix on the approach (usually an IAF or intermediate fix (IF) but it can be any fix on the approach more than 3 nm outside the FAF). However, if you hit that “VTF” button on your GPS anticipating vectors to final, it could be a problem if the controller then says “you’re five miles from BUNGO, turn left direct BUNGO, cleared RNAV 27 approach” and your GPS deleted all the fixes outside the FAF when you hit that VTF button. I recommend not activating VTF until you are 100% positive you’re actually getting vectors to final. Until then, it’s generally better to activate the leg on the approach it looks like you’ll intercept so you’ve still got all the fixes in your FPL in case you need one.

… Until Established

Next is the altitude to maintain “until established.”  “Established” means the needle is within half scale and under control. Thus, as you intercept a black line of the approach with a course, altitude, and distance, once the needle is within half scale you can begin descent to the altitude for that segment; you don’t have to wait for the needle to center completely. If you are receiving vectors to final for that SBY RNAV 23 approach and are told “fly heading 200, maintain 2000 until established, cleared RNAV 23,” you can leave 2000 for 1700 as soon as the needle is within half scale inside OKKOE. 

Where this went badly wrong in the case of TWA514 in 1974 was the crew’s misinterpretation of their clearance to descend. They were at 7000 feet joining the IAD VOR/DME RWY 12 from the west on an assigned heading of 090 when the controller told them to join the AML 300 radial (the final approach course) and cleared them for the approach.  While the controller erred by not giving them a lower altitude to maintain until established on the approach, the crew erred worse by beginning a descent all the way to 1800 (the first altitude on the profile view) as soon as they joined the radial.

What the crew missed was that 1800 altitude was the minimum to cross the FAF at 6 DME, not the altitude for the segment they were joining. At more than 25 nm from AML there was a 1900-foot ridge between them and Round Hill, where the 1800-foot segment began.  As a result, at 21 DME they hit the west face of the Blue Ridge about 50 feet from the top. But even though the 300 radial wasn’t part of the approach outside 18 DME, had they looked at their en route chart, they would have seen that the AML 300 radial was in fact a “published route segment”, specifically V4, with an MEA of 5000. If they had recognized that fact and leveled at 5000, and waited until they passed Round Hill to descend to 1800, this accident would not have occurred. You can read the full story in NTSB AAR 75-16.

Cleared Straight In

I find many instrument pilots have some confusion about course reversals and the “cleared straight in” instruction.  This comes up when you’re joining an approach that has a published course reversal such as a holding pattern in lieu of procedure turn (HPILPT).  The fundamental rule in such cases is that you must execute the reversal maneuver (i.e., cross the fix exactly twice—once entering, once exiting) unless one of the following conditions exists:

• Receiving vectors to final (not just vectors for the approach, as discussed above).
• On a depicted “no procedure turn” (NoPT) route.
• Already established in the hold.
• Cleared straight in for the approach (“Cleared straight in RNAV 23 approach”) rather than just cleared for the approach (“Cleared RNAV 23 approach”).
  
  … in which case you will cross the holding fix only once, then turn to the next fix. You have no choice in this matter—if you meet one of the four conditions, you must go straight in; if not, you must do the reversal. You must get an explicit ATC clearance to do anything else. 

Looking at the UKT RNAV 11 approach, this means if you’re arriving via the HIKES fix and “cleared for the RNAV 11 approach,” none of those four conditions apply, so you cross KLATU, turn out, complete the entry maneuver, and when you cross KLATU again continue inbound to BRDDA. On the other hand, if arriving from ETX or FLOAT, you’re on a NoPT route, so you would go straight in from KLATU the first time you cross it even without being “cleared straight in.” In fact, in that NoPT case, it would be improper to do the holding pattern without explicit clearance for a turn in the hold from ATC.

What if you’re arriving at KLATU from the west on a “direct KLATU” clearance rather from ETX or FLOAT?  It certainly seems that you could go straight in safely. However, by the book, you do not meet any of the four criteria for skipping the reversal, and you would be required to do it unless the controller explicitly said “cleared straight in.”  Where this gets problematic is when the controller really wants you to go straight in but forgets to say so explicitly (a not-uncommon occurrence in my experience).  

In this case, it’s important for you to query the controller, perhaps saying, “Approach, N12345, confirm cleared straight in RNAV 11 approach.” You just don’t know for sure otherwise if the controller really wants you to hold or just forgot to say “straight in,” and if you guess wrong, the consequences could be serious. For a great discussion of this issue, see “Cones of Confusion,” the cover story in the March 2010 issue of ASRS Callback, available on asrs.arc.nasa.gov.

Finally, just as with VTF, for a controller to clear you straight in, certain conditions must be met:

• The joining fix must be an IAF, IF, or other fix on the approach more than 3 nm outside the FAF.
• The turn from your arrival course to the next course after the joining fix must be no more than 90°.
• Your joining altitude must meet TERPS descent gradient limits to the next fix.

The last option to discuss is the Terminal Arrival Area, as seen on the THV RNAV (GPS) RWY 35. The “pie slices” constitute published segments for approach clearance purposes. 

If you’re inside the slice cleared to the center fix for the slice and then cleared for the approach, you can immediately leave your last assigned altitude for the slice altitude, and if labeled NoPT, skip the reversal. If arriving from the west cleared direct LACES at 5000, once within 30 nm and cleared for the approach, you can descend to 3800. Since LACES-XOPPA is NoPT, you won’t do the reversal. Likewise, if arriving from the southeast at 4000 cleared direct XOPPA, when you’re within 30 nm and cleared for the approach, you can descend to 2800 and, since that slice is labeled NoPT, you would go straight in from XOPPA. The only time you’d do the reversal would be cleared direct XOPPA from the north, but then the controller should send you to LACES or PAYCO, not XOPPA.