Instrument Rating: Approaches

When one thinks of what an instrument rating entails, two things are likely come to mind:

  • Flying in the clouds
  • Instrument approaches

An approach is the “fun part” of an instrument rating. It is, after all, one of the most tangible new topics that an instrument student learns as part of their training. The student learns how to read, brief, and interpret an approach plate, and determines from that plate what course to fly, what altitudes to hold, what ground speed to maintain, and what to do if the approach needs to be called off (essentially the equivalent of a go-around, called the “missed approach”). The pilot workload is high during an instrument approach, but with training and a strong basic attitude instrument flying skillset, they can be done confidently and safely.

CDIs and Glideslopes: Understanding the different types of approaches

Pilots will frequently refer to two different sorts of approaches: non-precision approaches and precision approaches. A non-precision approach refers to one that provides lateral guidance only. Lateral course correction can be provided in a variety of ways — VOR or NDB transmitters, localizers, and certain RNAV (GPS) approaches all provide this capability. The way that an aircraft descends to a landing is through the use of predefined stepdown altitudes at waypoints along the approach. These waypoints can be identified through a GPS navigator, a DME readout, or a supporting VOR.

A CDI containing lateral and vertical guidance needles

A precision approach, on the other hand, is an instrument approach that provides both lateral and vertical guidance. This is done through the addition of a glideslope on the CDI, and the objective is to keep both needles centered. An ILS (instrument landing system) is one such example of a precision approach. A PAR approach is another such approach, where a controller guides the aircraft down using radio callouts. These approaches are rare, but do exist.

If you’d like some trivia to impress (or annoy) your friends at the airport, there is a third distinct category of approach, as defined by the FAA: an APV approach, or Approach Procedure with Vertical guidance. A GPS approach with a glideslope (ie an LPV approach) is NOT a precision approach but rather an APV approach. The reason for this distinction is because ICAO defines a precision approach as a very specific thing, and it was ultimately easier for the FAA to create a third category of approach rather than try to retrofit RNAV approaches to fit into the legacy category of “precision”.

If you have read the ACS, you may recall that an applicant must accomplish at least two non-precision approaches and one precision approach, and “acceptable instrument approaches for this [precision] part of the practical test are the ILS and GLS [approaches].” Thankfully, the FAA allows for an LPV approach as well by stating: “..if the installed equipment and database is current and qualified for IFR flight and approaches to LPV minima, an LPV minima approach can be flown to demonstrate precision approach proficiency if the LPV DA is equal to or less than 300 feet HAT [height above terrain].”

So for all intents and purposes, LPV approaches can be treated much in the same way as an ILS is: a very precise approach that gets you down low.

Approach Plates

The VOR-B approach into KSFZ

Let’s look at the VOR-B approach into KSFZ for a reference. We won’t go over absolutely everything, but cover the important parts the apply to civilian aircraft. The way we brief an approach plate like this is top to bottom, right to left.

  • The top briefing strips tells us that the VOR used for navigation is the VOR/DME at Putnam, channel 117.4.
  • The approach course to be dialed into the CDI and flown is the 111 degree radial FROM the PUT VOR.
  • The “T” and “A” embedded in a triangle refers to the fact that non-standard takeoff and alternate requirements exists. The local altimeter setting is required to fly down to 980 feet MSL after the final approach fix, otherwise the Providence altimeter setting must be used and the minimum descent altitude must be increased to 1080 feet MSL. Furthermore, if the approach is made during night, landing on Runway 33 or 15 is not authorized.
  • The missed approach instructions are to make a climbing right turn to 2500 feet MSL via the Norwich 057 degree VOR, and hold at the FOSTY intersection.
  • The plan view shows “the big picture” of the approach. We start the approach at the initial approach fix at the Putnam VOR and it terminates with the missed approach point at JOPVO. Each of the waypoints can be identified in a variety of ways: DME distance from the PUT VOR, identification of VOR radials from the Providence transmitter along the approach course, or using a GPS navigator.
    • The inverted “V” with a dot in the middle represents obstructions. There aren’t a ton on this approach, but one in particular jumps out at us: right near the MAP near the airport! The altitude listed is 573 — thankfully, this is in MSL, not AGL, which means that if we remain at or above our MDA of 980 MSL, we are assured 500 feet of clearance.
    • The circle in the top right corner of the plan view shows the Minimum Sector Altitude in a 25 NM radius around the Putnam VOR. This is a reference that provides us the minimum altitude to avoid all obstacle clearance in the areas depicted.
    • The text in the top left corner of the plan view states that the VOR-B approach is not authorized for aircraft arriving at the PUT VOR via the V146-151 airway. Why is this? It’s due to a national policy called the United States Standard for Terminal Instrument Procedures, also known as “TERPS”. TERPS 2-4-1.a states: “When the IAF is part of the en route structure, the angle of intersection between the en route structure and a ground-based initial approach segment course must not exceed 120 degrees. For RNAV routes, apply Order 8260.58.” What this means is that the turn from V146-151 northwest-bound to the approach course is too sharp, and thus not authorized. What this effectively means is that pilots wishing to execute the VOR-B approach should do so via radar vectors.
    • In the bottom left corner of the plan view, an alternate missed approach fix exists. Instead of holding at the FOSTY intersection, a pilot may elect to hold back at the PUT VOR, allowing for positioning to reattempt the approach.
    • The bottom left corner of the approach plate shows a zoomed in view of the airport, and where the approach terminates. Assuming the approach is flown correctly, the pilot should find themselves approximately midfield of the 5/23 runway. The distance between the final approach fix and the missed approach point is 4.9 NM, and if flown at 90 knots groundspeed, should take three minutes and sixteen seconds.
  • The bottom right corner of the plate shows the profile view. This view shows the approach course to be flown (111 degrees FROM PUT) and the stepdown altitudes. The line underneath the altitude shows the minimum descent altitude for that segment — beginning the approach and until intercepting the BIRDS intersection, the pilot must not descend below 2500 feet. After BIRDS, the pilot may descend no lower than 1800 feet. At the final approach fix, identified on the profile view with a Maltese Cross, the pilot may descend no lower than 980 feet MSL (539 feet AGL) with 1 mile of visibility. Even when the circling approach may be executed, the aircraft may not descend lower than the MDA until three conditions are met:
    1. The aircraft is continuously in a position from which a descent to a landing on the intended runway can be made at a normal rate of descent using normal maneuvers.
    2. The flight visibility (or enhanced flight visibility, if so equipped) is not less than the visibility prescribed in the standard instrument approach being used.
    3. At least one authorized visual reference for the intended runway is distinctly visible and identifiable to the pilot, such as the threshold markings, lights, or threshold itself, the runway lights, the touchdown zone, etc. If the approach light system is in view, the pilot may descend to 100 feet above the touchdown zone, only if the the red terminating bars or the red side row bars are also visible and identifiable.
  • Finally, a short reminder of the missed approach procedure is listed in the profile view.
The VOR-B approach into KSFZ is not authorized if flying northwest bound on the V146-151-405 Victor airway, due to TERPS restrictions.

As mentioned earlier, this particular type of approach doesn’t provide the pilot with any vertical guidance, hence the “non-precision” nature of the approach. Let’s look at another plate, this time being a precision approach.

Introducing the Glideslope and DAs

ILS RWY 5 at KPVD

With an ILS approach, the glideslope is introduced to the pilot to guide them down from the final approach fix. We brief the approach in much the same manner as we did the VOR-B into KSFZ by reviewing the briefing strips, the plan view, and the profile view of the plate. Some key differences between the VOR-B and this approach:

  • A procedure turn exists if intercepting the localizer between CUTSI and KENTE intersection. However, if we are on radar vectors to the FAF (which will almost certainly will be), we will not fly the procedure turn.
  • The glideslope should be intercepted and alive at CUTSI. At this point, we may fly the glideslope, but we may not descend below 740 feet until we intercept FEXUX. After FEXUX, we may descend to an altitude of 253 feet MSL. At this time, we MUST execute a missed approach if not able to meet the three criteria listed previously (position to land normally, visibility adequate, at least one visual reference). This is why the DA is called a “decision height”.
  • There is a V denoted on the profile view 2.8NM DME out from the localizer. This is the Visual Descent Point. This would apply if we were flying the LOC approach, but doesn’t apply to the ILS approach. A VDP is a point on the final approach course of a non-precision straight-in approach from which normal descent from the MDA to the runway touchdown point may begin provided adequate visual reference is established. We’ll go over VDPs in a separate post in the future, as there is a lot of confusion surrounding what they are and what they do.

The main advantage of a precision approach versus a non-precision approach is that with a precision approach, you have an established, stabilized approach for most of the approach. The Instrument Procedures Handbook states:

“A constant-rate descent has many safety advantages over non-precision approaches that require multiple level-offs at stepdown fixes or manually calculating rates of descent. A stabilized approach can be maintained from the FAF to the landing when a constant-rate descent is used. Additionally, the use of an electronic vertical path produced by onboard avionics can serve to reduce CFIT, and minimize the effects of visual illusions on approach and landing. Some countries even mandate the use of continuous descent final approaches (CDFAs) on non-precision approaches.”

Conclusion

There is a lot of information on approach plates, but the information is always presented in a logical, standardized manner. It is always wise to brief approaches before takeoff and during cruise so that we are not rushing to familiarize ourselves with this critical and information-rich chart. Given enough practice, an instrument student will find themselves able to read plates quickly and effectively so that any approach will make sense to them.

Instrument Rating Training: Honing the BAI-Blade and Introducing Approaches

Things are starting to get a little more interesting!

The following two weeks of instrument training since beginning on the 13th of June were very productive! In fact, since the first lesson on basic attitude flying, I managed to fly (or log time in a sim) nine times within a two week period. Paradoxically, the best way to save time and money while pursuing any rating or certificate is to fly as often as your schedule and instructor availability allow for. By building on top of previous lessons quickly, you forget less over time and refine technique without letting the concepts lapse. (In psychology, this is referred to as the Ebbinghaus forgetting curve and is a fundamental topic that is taught to flight and ground instructors. We’ll cover that one at another time…)

The way that Doug has been introducing new instrument flying concepts is layering something new on top of old topics. So, day one was all about basic attitude flying: turns and basic navigation with reference only to the instruments. Then we started introducing wind correction and course tracking — keeping the CDI needle aligned and centered under less-than-perfect conditions (hint: it’s always less than perfect out… especially with IFR weather!).

Once Doug was satisfied enough with my BAI flying and being able to control the airplane with foggles on, it was time to introduce basic procedures. The first procedure we started with were holds and hold entries. The FAA makes a big production out of the proper entry type for holds on the written, but holds are also important in the sense that procedure turns in approaches are basically the same thing as a hold. Holds aren’t terribly difficult in of themselves; unless otherwise stated, a hold has a fix and the legs are supposed to be one minute in length each. The GPS in my plane makes holds incredibly easy to manage, but we still timed each leg one minute using a timer before conducting a standard rate turn 180 degrees. One thing that I need to get better at is tightening up the inbound leg turn so that I’m not overshooting into the nonholding side…

Anatomy of a hold. Things get more interesting when you factor in wind correction.

After introducing altitude changes into holds, we reviewed the VOR-A approach into Danielson. My plane has two VORs in addition to the GPS, so it makes for a very capable instrument trainer. I actually like VOR approaches, as I learned how to fly them back when I had a Cessna 172K with only two VOR receivers.

As of mid-2020, KLZD only has a single instrument approach (the VOR-A depicted here).

The VOR-A into KLZD is relatively simple on paper, but it’s actually a somewhat challenging approach. You start with a hold at the Putnam VOR no lower than 2600 feet (ie, a procedure turn), and then you turn inbound to the 211 approach course. This point represents your final approach fix and you descend to an MDA of 1120 feet MSL, with obstructions all around. The approach dumps you perpendicular to the runway and your only option for landing is to circle to either 13 or 31. A missed approach has you climb back to 2600 and head back to the Putnam VOR and hold.

We were to fly this approach in my plane, but a thunderstorm popped up right in our flight path before we took off (realities of summer). Thankfully, AirVentures has a basic aviation training device — in other words, a certified computer with a flight simulator program on it. A BATD can be used for up to ten hours of simulated instrument training, so if the weather is too bad for us to go flying, we can still get useful time out the day! I shot the approach into Danielson using the sim and worked on VOR tracking.

Doug had to go on a multi-day trip, so he left me to my own devices for a few days. You need forty hours of simulated instrument time to take the checkride but twenty five of those hours can be accumulated with a safety pilot — in other words, it doesn’t have to be done with an instructor, but it can be done with other private pilots. I have two friends (both commercial pilots and instrument rated) that are happy to provide safety pilot time, and once I had something to work on (ie, the approaches), it was a no-brainer to get them engaged.

Holding altitude, being precise, and demanding excellence

While flying with my friend Bill, we shot two VOR approaches (VOR-A LZD, VOR-B SFZ) and a localizer approach (LOC 05 SFZ) as well as two RNAV approaches into 23 SFZ (ignoring the glideslope and using LNAV minimums). During this time, I got myself down to the MDA, but flew below the MDA a handful of times. The MDA is a minimum descent altitude, meaning that by busting through the altitude assigned to the MDA, I would flunk the checkride. The ACS states the following:

“For the final approach segment, maintain no more than a 3/4-scale deflection of the CDI, maintain airspeed +/- 10 knots, and altitude, if applicable, above MDA, +100/-0 feet, to the Visual Descent Point (VDP) or Missed Approach Point (MAP).”

The ACS (Airman Certification Standards) has replaced the old PTS for most certificates and ratings. It prescribes the expected knowledge, risk assessment, and skills expected from an airman applicant, and is in essence an open-book test. No surprises, which means no excuses…

A side note about a pilot’s certificate being “a license to learn”: it’s critical that as pilots, we demand excellence from ourselves and not be complacent with lax tolerances. In VFR flying, being sloppy with your altitude or heading leads to sloppy performance further into the flight. In IFR flying, sloppy flying will get you violated or worse, careening into terrain or other obstruction. The message here is even if you’re not a professional pilot, strive for professionalism. I’m certainly not perfect at this, nor is any weekend warrior private pilot, but the constant pursuit should be ever present. We owe it to ourselves and to our passengers, and in fact, this is why I am pursuing an instrument rating in the first place.

Conclusion

The biggest takeaway that I have had so far is that the parts that will eat non-proficient instrument pilots alive are the transitions. Takeoff to cruise is a transition, cruise to approach is a transition, and approach to landing is a transition. Each one of these segments has a sudden burst of workload and it’s up to the instrument pilot to manage them appropriately. The biggest and most important task, however, is to maintain positive aircraft control through these transitions. That is why there has been so much emphasis on basic attitude instrument flying, so far. As the time and lessons have progressed, I have been tasked with doing more and more items that an instrument pilot would be expected to do. The “big picture” is starting to come into focus as I become more proficient and comfortable with being a pilot without reference to the ground. Stay tuned for what comes next: flying in the actual clouds…