An instrument approach procedure is often described as a series of windows, or gates, extending from the final approach fix (FAF) to the missed approach point (MAP). Stay within the ever-narrowing vertical and lateral limits and you’ll arrive at the MAP on glide path and centered on the inbound course. It’s far less common to extend this concept backward from the FAF through the terminal area to the en route environment, and forward from the MAP through the missed approach to the holding fix.
I find it at least as helpful to think in terms of a succession of gates from the beginning of descent to entering the missed approach hold. Approaching each gate prompts you to complete a checklist or flow, and gives you specific criteria to gauge your progress and decide if and how you can continue. To illustrate what I mean, let’s take a hypothetical flight from cruise through an approach and to the missed approach hold, or perhaps breaking out and being able to land.
Top Of Descent Gate
Top of descent (TOD) is a standard concept in multi-pilot turbine operations, but it’s not commonly taught or used in single-pilot situations and—especially—piston-powered airplanes. The TOD is simply the point at which you begin your descent from cruising altitude. You may or may not have intermediate level-offs between TOD and the final altitude inbound to the FAF.
Passing through TOD Gate, complete the Descent checklist. You should already have the weather at your destination, if available, and briefed and set up for the approach to expect or the approach of your choice at a non-towered airport. Adjust power to descend no faster than VNO—in smooth air, I like to descend at the same indicated airspeed I had obtained in cruise. If turbulence is likely, I’ll slow to my target turbulent air penetration speed at TOD. (See the sidebar “The Other Kind Of Best Speed” on page 23 for an explanation of this target speed.)
Entering the terminal environment, signified either by becoming established on a published segment of the approach or the beginning of vectors toward final, is what I called the Vectors Gate. By this time, the approach checklist should be complete. In most cases, this is simply verifying that the avionics are set and activated for the approach, and a final review of approach briefing items.
At the Vectors Gate, and unless you’re keeping your speed up for some reason, slow the airplane to your preferred approach speed, one allowing you to establish the airplane’s preferred approach configuration without any additional adjustments. In other words, you’re below its flap or landing gear extension speeds, as appropriate to the type and your preference. I personally like to slow to something not terribly faster than my final approach speed—about 120 KIAS in the A36. That number works well in a lot of piston airplanes.
Joining the final approach course inbound, I’ll configure the airplane and slow to approach speed—I use 110 KIAS and partial flaps, gear up, in the airplanes I usually fly. At this point advance the propeller to its climb setting and the mixture to a setting well rich of peak exhaust gas temperature (EGT). A lean-of-peak EGT cruise setting requires you to advance two levers, mixture then throttle, to increase power. Going rich if peak at the Approach Inbound Gate gives you highly desirable single-lever power control—the throttle alone—for the remainder of the approach all of the way through and including the missed.
Triple-check the “ADM” killer items for the approach: Altitude (decision height, decision altitude or minimum descent altitude) of the MAP, what Defines the MAP (altitude, waypoint, distance or even old-fashioned approach timing) and the beginning of the Missed (directions, altitude restrictions, and holding altitude) before you near the FAF.
Reaching the FAF, extend the landing gear, if appropriate, or reduce power as necessary to begin your target rate of descent. Some types of retractable gear airplanes have an unusually high amount of drag when the gear is in transit. Others’ gear extends one leg at a time, the drag-inducing yaw during extension. In these cases, you may want to extend the gear before reaching the FAF, adding power as necessary to overcome the drag until ready to begin your descent.
I’ve heard from other pilots who like to extend the gear early for myriad other reasons. Whatever routine works for you is fine, but I suggest you pick one technique and use it consistently. Whatever your technique, confirm the airplane is on speed, on course and descending at the vertical speed necessary to remain on profile. Doublecheck the airplane’s configuration.
1000 Feet To Go Gate
By now, the approach windows—or gates—are narrowing. At 1000 feet above DH, DA or MDA, again check that the airplane is on speed, in configuration, on course and on glide path. Accept no more than five knots deviation from your target speed, and two “dots” deviation on course guidance (GPS, localizer, VOR radial, etc.) and glidepath/glideslope if one is available. That’s nothing more than checkride standards, and you should be able to do better than that. Any greater deviation than that and you should miss the approach.
Yes, I know the FAA permits greater deviation than that in the real world. But history shows that an unstabilized approach is a common contributor to approach crashes. Develop the skill to do better by demanding more from yourself; develop the discipline to miss the approach if you can’t be on target within “two dots and five knots” at 1000 feet to go missed.
500 Foot/visual Gate
With 500 feet to go you should be within one dot and three knots, on vertical speed, in configuration, and tracking the course line within five degrees of heading. If you aren’t, and you’re still in IMC, miss the approach—you are destabilized, or would have to destabilize the approach to correct, and you’re very close to the ground.
If you break out anywhere on the approach, continue. As you pass the 500 feet to go gate, transition to a visual landing. This sounds easy enough, but actually requires skill and practice to do smoothly without losing course and glidepath control during the transition. If you’ve nailed the course guidance and the glidepath looks good, do nothing. Fly to the runway, take over visually and land in the touchdown zone.
Missed Approach Point Gate
If, however, you reach the MAP, still on all your performance and alignment targets, and you cannot descend visually using normal flight maneuvers to the runway, you have no option but to miss the approach. In most light aircraft, this requires you to turn off the autopilot as you add power, adjust attitude and begin climbout with the same precision you (or the autopilot) used to get to the MAP in the first place.
You should not have to look away from the instruments to know the initial heading and altitude for the missed approach, and whether you need to climb on a specific heading to some minimum altitude before making any turns—you don’t have the luxury of turning away from the instruments. Doing this with precision, very close to the ground, while increasing the angle of attack, and all by reference to instruments, is an excellent reason to require the level of precision described for the 1000- and 500-foot gates.
Missed Approach Climb Gate
Once a climb is established, stay on the approach course to 400 feet agl before making any turns, unless directed otherwise. After passing through 400 agl and as soon as workload permits, transition to normal cruise climb and verify your actions with your airplane’s cruise climb checklist. Exit the GPS navigator’s suspend mode as applicable. Confirm the route and altitudes for the missed (you’ve briefed this before; this is a quick refresher) and fly the procedure. Remember you must fly as precisely here as you did inbound in the approach.
Despite the need to fly the airplane through a climb and into what might be a complicated hold, you also need to review what to do next. You should have planned for Plan B already, and now’s the time to implement it.
Leveling On The Missed Gate
This should be treated the same as the inbound gate. Level the airplane, establish a low-speed, level cruise and confirm your actions with the cruise—or top of climb (TOC) if you prefer—checklist. Review the holding pattern entry; enter the hold. Eventually you’ll transition to cruise as you fly to an alternate, or you’ll brief, enter and fly another approach, passing through another series of gates to the ground or another missed.
Thinking of the various points on the approach as “gates” through which we fly and by which we need to accomplish certain obvious tasks isn’t revelatory or difficult. It’s what we do to manage airplane configuration and maximize the ease with which we fly stabilized approaches.
Depending on the approach, which also depends on the airspace and terrain, the typical instrument approach offers numerous “gates”—opportunities to gauge our progress from the en route environment to the runway. These gates—fixes—also offer us the opportunity to get and stay ahead of the airplane during one of the more complicated maneuvers instrument pilots perform.
Along the way, the gates we fly through provide a yardstick by which to measure our progress. Thanks to standardization, we know that when we fly past the FAF, we should be on speed and configured. Using the gates properly, we always will be.
Standard Terminal Arrival Procedures, or STARs, are used in busy airspace to funnel large numbers of aircraft into one or more airports. Many general aviation pilots have trepidations about flying STARs—there was a time when it was common for pilots to enter “No SID [standard instrument departures]/no STAR” into the Remarks block of an IFR flight plan to avoid having to fly the procedures. (To be fair, this was primarily to avoid having to purchase the separate SID/STAR books, back in the bad ol’ days when we all flew with at least one piece of luggage filled with paper charts.)
In many ways, however, STARs (and SIDs) make flying in busy terminal airspace easier. Think of them as a published approach procedure from the en route environment to an approach’s IAF. A STAR allows you to anticipate and plan for a route and series of altitudes as an alternative to when you’re often left guessing what ATC is going to do with you without a STAR. (In some terminal areas, it’s not at all likely ATC knew what they wanted you to do, either.) Today’s IFR GPS systems include STARs in the database, allowing you to load the route and let the autopilot fly you through it if you wish.
Like an instrument approach, you may enter a STAR at one of several fixes along its route. In general, then, I treat the first fix on a STAR as a vectoring gate, and complete my approach checklist and transition to vectoring speed accordingly. The exception is when I enter a STAR at a fix well away from the airport—after all, STARs are designed primarily for fast jet traffic, and some of the fixes are very far out. In the fast singles and piston twins I usually fly, I join a STAR closer in to the airport.
STARs like this one, the CAVLR Three Arrival into the Washington Dulles International Airport, can be considered as a series of gates, in this case starting at FL220 some 87 nm from the airport. Fly the descent with the same planning and configuration considerations as you would the approach, and you’ll be prepared for the transition from en route to terminal procedures.
One Kind Of ‘Best Speed’
As we discussed in some detail last month, ATC may ask you to maintain your “best speed” to some fix on your arrival and/or approach procedure. Sometimes, you’ll be asked to maintain a specific indicated airspeed.
If I’m asked to maintain best speed, I use a power setting and airplane configuration that puts me up to 40- to 50-percent above my approach gate speed and, in the case of a retractable gear airplane, just below gear extension/operation speed (VLE/VLO). That way, I can extend the rubber-coated speed brakes to slow down and descend when reaching the final approach fix inbound.
When ATC asks you to fly best speed during an arrival or approach, it’s up to you to define what “best” means. Sometimes that is actually slowing down for turbulence; tell controllers so. If they want you to fly a specific speed and for any reason you cannot, decline the clearance and tell them why: “Unable due to turbulence.” The worst that can happen is you get vectored out of sequence while you fly at the necessary speed. You are always the pilot-in-command.
The Other Kind Of ‘Best Speed’
There’s another kind of “best speed”: the speed for turbulent air penetration. In moderate or greater turbulence, you need to be no faster than the manufacturer’s published turbulent air penetration speed. For most of us, maneuvering speed (VA) is the only guidance we have for flying in moderate or great turbulence.
Two common questions about flying in turbulent air are, “When do I slow down?” and “What speed do I fly?” I advise that we can’t wait until entering turbulence before slowing down because the airplane may overstress at the higher speed. You don’t get a free bump—you must anticipate when you might enter moderate or greater turbulence, and slow down before you get into it.
The second question’s answer is we always need to be below weight-adjusted VA, which is about two percent slower for each 100 pounds below maximum gross weight in personal airplanes. But in turbulent air, you need to fly at an airspeed at which the maximum airspeed increase is still lower than the weight-adjusted turbulence penetration speed. In the airplanes I commonly fly, with a maximum-weight VA of 141 KIAS and 125 KIAS at the lowest reasonable operating weight, I use a target turbulent air speed of 110 KIAS. This gives me a 15-knot buffer for shear-driven speed increases. If LLWS alerts indicate speed fluctuations greater than that, I’ll divert.