TERPS REVIEW Circle-To-Land Tactics The circling maneuver varies widely, from almost a straight-in to a large visual segment.
By Wally Roberts port in distinct view, except when get into the final approach area of banking temporarily blocks the view. the landing runway is there any of- THE CIRCLING MANEUVER IS Further, FAR 91.175(c) comes into fer of obstacle protection below one of the more demanding aspects play once you’re satisfied it’s time MDA. If the landing runway has a of instrument flying. This is espe- to leave MDA because you’re “in the VASI or PAPI, you’re in good shape cially true when the ceiling is near slot” for the landing runway. once you’re within 10 degrees of the MDA, the visibility is near mini- extended runway centerline. Also, if mums, and there’s turbulence with Those high MDAs the runway has approach lights and rain or snow thrown into the mix. The FAA view of circling really straight-in minimums on a different In my article “Circling and the Vi- only covers circling MDAs to per- IAP of three-quarters of a mile or less, sual Segment” (January 1996 IFRR), haps a few hundred feet higher than you’re in good shape. (However, I discussed the technical aspects of the standard 350/450/550. Once the chances are you would have flown circling approach design. This article MDA reaches a height where you the straight-in approach in this case, will review the fundamentals and must depart MDA much before roll- right?) provide a more technique-oriented ing out on a final within the distance If the landing runway has neither perspective than the previous article. limitations of your approach category VASI/PAPI nor approach lights with (1.3 nm for Category A), then you one-half or three-quarter mile Fundamentals should think twice about circling at straight-in minimums, then you’re on Figure 1 (below right) is from the such an airport unless you know your own. Once you’re 300 feet be- AIM and shows how the circling ma- where every big brick pile is located. low MDA there could be anything neuvering area is constructed. At an If you depart the circling MDA on sticking up, even to the runway airport with all five approach catego- downwind or base, the FAA takes a threshold. This is where a local pilot’s ries, the radii and tangents must be walk at that point. Only where you knowledge equates to a big edge calculated five times with larger di- over the hapless itinerant. mensions for each approach cat- egory. The minimum obstacle clear- AIM view of circling ance within each approach category AIM 5-4-18f. states: “Circling circling maneuvering area is 300 feet. Minimums: In some busy terminal Also, the height above airport areas, ATC may not allow circling (HAA) of the MDA cannot be less and circling minimums will not be than: Cat A – 350 feet, Cats B and C published. Published circling mini- – 450 feet, and Cats D and E – 550 mums provide obstacle clearance feet. These minimum HAAs for cir- when pilots remain within the appro- cling are just that: minimums. Nei- priate area of protection. Pilots ther the minimum circling HAAs nor should remain at or above the cir- the lateral areas protected by the cling altitude until the aircraft is con- table in Figure 1 are conservative. tinuously in a position from which a Instead, they are biased toward op- descent to a landing on the intended erational necessity with the presump- runway can be made at a normal rate tion of a high degree of pilot skill of descent using normal maneuvers. and airport familiarity. ICAO inter- “Circling may require maneuvers national circling areas are much at low altitude, at low airspeed, and larger than those provided by the in marginal weather conditions. Pi- FAA, which should give you addi- Figure 1. Circling approach pro- lots must use sound judgment, have tional pause about the FAA’s circling tected airspace varies by aircraft an in depth knowledge of their ca- criteria and philosophies. category. The HAA must be at least pabilities, and fully understand the FAR 91.175(e)(2) requires you to 350 feet for Cat A, 450 feet for B & aircraft performance to determine the keep an identifiable part of the air- C, and 550 feet for D & E. exact circling maneuver since
10 IFR Refresher, November 1997 TERPS REVIEW weather, unique airport design, and some terrain or other obstacle whiz- no business circling at an airport un- the aircraft position, altitude, and zing by only 300 feet below you? less the reasons for application of airspeed must all be considered. The With all this taking place at night, in such a note for that airport is obvi- following basic rules apply: strong winds, and perhaps rain or ous to you. “1. Maneuver the shortest path to snow with one-mile visibility? The Keep in mind the excluded sector the base or downwind leg, as appro- MDA is just that; you cannot go be- might be defined by the extended priate, considering existing weather low it under any circumstances until runway centerline of the runway to conditions. There is no restriction you’re in a position to make a nor- which you’re circling. Assume, es- from passing over the airport or mal descent to landing—hopefully pecially at night, that a brick wall ris- other runways. on, or near, final. ing to infinity is just to the restricted “2. It should be recognized that side of runway centerline. Slightly circling maneuvers may be made Restricted sector undershooting your turn to final is while VFR or other flying is in Where there are really high ob- the best bet at such an airport. progress at the airport. Standard left stacles on only one side of the air- turns or specific instruction from the port, the circling minimums will of- Classic circle-to-land controller for maneuvering must be ten be annotated with a restriction, Figure 2 (below left) illustrates the considered when circling to land. such as “Circling not authorized “classic” circle-to-land maneuver “3. At airports without a control west of Runway 18-36.” These notes where the landing runway is the re- tower, it may be desirable to fly over are easy to miss. The FAA has no ciprocal of the runway to which the the airport to observe wind and turn responsibility for obstacles that exist IAP leads. Single-pilot operations dic- indicators and other traffic which in such a restricted sector. You have tate circling so the critical part of the may be on the runway or flying in airport is to your left. If a restricted the vicinity of the airport.” sector note forces you to circle with the critical part of the airport to your Be careful out there right, that is a very loud hint you This AIM guidance basically says, shouldn’t be circling at all, unless “you all better be careful out there.” you know the lay of the land so well Subparagraphs 1 and 3 are seem- that peeks out the right side will keep ingly contradictory. If you keep in you both safe and legal. mind that subparagraph 1 is focused In Figure 2, I recommend against on towered airports, whereas sub- departing the electronic final ap- paragraph 3 is not, it becomes proach guidance until within one clearer what the FAA is trying to say. mile of the approach end of the run- Circling at a busy, non-tower air- way served by the IAP. This assures port in marginal weather is fraught adequate visual reference and initial with the hazard potential of a mid- containment within the circling ma- air collision, in addition to the sub- neuvering area. The broken line is stantial hazard of exposure to con- the visual flight track and should re- trolled flight into terrain during mar- main well within the distance speci- ginal or minimal conditions. When fied for your approach category in weather conditions permit, never use Figure 1. Ideally, you shouldn’t leave the circling MDA when a higher traf- MDA until rolling out on the land- fic pattern altitude will suffice. ing runway’s final leg. Only where you need to operate at the minimum descent altitude for Lined up, but too steep circling should you operate below Figure 3 (page 12) is the profile pattern altitude. The circling MDA view and minimums for the LOC- is different than a straight-in MDA Figure 2. “Classic” circle-to-land DME (BACK CRS)-B at Medford, OR in that it becomes an operational al- scenario with electronic guidance to (MFR). On this IAP, the localizer is titude for a sometimes lengthy visual Runway 36, followed by circling ma- perfectly lined up with the runway, circuit of the airport, with precious neuver to Runway 18. In this situa- but the descent gradient is too steep little margin for error. Are you satis- tion, don’t depart the electronic fi- for TERPs straight-in minimums. For fied your skills permit a sustained nal approach guidance until within straight-in minimums, the final ap- visual circuit around the airport at one mile of the approach end of the proach course must be aligned within only 350 - 450 feet agl, and with runway served by the IAP. (continued on next page)
IFR Refresher, November 1997 11 TERPS REVIEW
Circle-To-Land… (continued from page 11) 30 degrees of the runway and the final segment descent gradient must not exceed 400 feet per mile to touch- down. With circling minimums, how- ever, the FAA only calculates the 400-foot-per-mile limitation to MDA, which leaves the pilot hang- ing to figure out what’s needed to get from MDA to landing. I believe the FAA should chart the descent gradient on such potentially dangerous and misleading proce- REPRODUCED WITH PERMISSION © JEPPESEN SANDERSON, INC., 1996. ALL RIGHTS RESERVED. dures. In the example illustrated in Figure 3. The LOC-DME (BACK CRS)-B at Medford, OR. Figure 3, that big blank box to the The localizer is aligned within 30 degrees of the run- left of the circling minimums could way, yet this IAP has circling-only minimums because (should) state, to the effect, “Descent of the steep descent gradient. You’d be much more aware gradient from D9.0 IMFR LOC to and prepared if the chart noted: “Descent gradient from Runway 32 touchdown is 645 feet D9.0 IMFR LOC to Runway 32 touchdown is 645 feet per mile (6.1 degrees).” Nonetheless, per mile (6.1 degrees).” you can make such a calculation as part of your preflight familiarization with the airport. Safety and efficiency influenced the der such conditions and when ATC latter group for pilots. The FAA ex- has cleared them for landing on that The 800 pound gorilla perts (mostly pilots) were sometimes runway, pilots are not expected to Both FAA experts and industry pi- for pilots, but more often for opera- circle even though only circling mini- lot representatives authored the tional “flexibility.” Then, after the mums are published. If they desire TERPs instrument approach criteria. fact, the FAA 800-pound gorilla to circle, they should advise ATC.” (ATC “metal movers”) placed its spin on the situation when necessary for “the service.” A classic example is illustrated in Figure 3, which is a lined-up, but steep, circling-only IAP. MFR is a part-time Class D airport. The AIM has something to say about such approaches at towered airports: (5-4-18d.) “Straight-in Minimums: Are shown on the IAP when the fi- nal approach course is within 30 de- grees of the runway alignment and a normal descent can be made from the IFR altitude shown on the IAP to the runway surface. When either the nor- mal rate of descent or the runway alignment factor of 30 degrees is exceeded, a straight-in minimum is not published and a circling minimum Figure 4. For a circling approach applies. The fact that a straight-in Figure 5. Because the intersection of where the electronic final is aligned minimum is not published does not Runway 23 with the IAP runway is with the runway, fly down the run- preclude pilots from landing straight sufficiently down-field, you can way at MDA until it’s about to disap- in if they have the active runway in break off the electronic final in a pear under the nose, then enter the sight and have sufficient time to make manner similar to the “classic” close-in circle-to-land maneuver. a normal approach for landing. Un- circle-to-land in Figure 2.
12 IFR Refresher, November 1997 TERPS REVIEW
If you’re not comfortable landing the intersection of Runway 23 with Roulette. straight in with an IAP like the MFR the IAP runway is sufficiently down- example, the burden is upon you to field, you can break off the electronic Wally Roberts is a retired airline advise the tower as early as possible. final in a manner similar to the “clas- captain, former chairman of the sic” circle-to-land to Runway 18. ALPA TERPs Committee, and an ac- Circling to land straight-in In Figure 6 (on right), however, tive CFII in San Clemente, CA. Figure 4 (page 12) is the method I Runway 29 intersects your IAP run- recommend for handling a situation way too close in order to break-off like the MFR IAP, where you aren’t and enter left circling. If you attempt comfortable landing straight-in. The to directly enter left downwind for first reaction of both pilots and con- Runway 29, you would either be trollers is to “do a 360 on final” rather forced to depart the electronic guid- than what I’ve illustrated. A 360-de- ance at a point where visual cues gree turn on final is fine on a clear might be marginal, or you might un- VFR day. That’s not the type of day wittingly depart the circling maneu- with which this article is concerned, vering area protected airspace, or however. I’m assuming night or day you might end up atop Runway 29 with precip, bumps, gusty winds, with no place to go. My recom- etc. When you really need to circle mended maneuver in Figure 6, al- at MFR, Figure 4 is the way to do it. though a bit more complex at first Fly down the runway at MDA until glance, will keep you where you it’s about to disappear under the nose, want to be. then enter the close-in circle-to-land maneuver. Beware the dangers Figure 6. You want to land on Run- There are many variations on the way 29, but it’s too close to break-off Variations on the theme themes of Figures 5 and 6. The game and enter left circling. In this situa- Figures 5 and 6 show more com- plan is best figured out over a cup of tion, fly down the runway until cross- plex airport configurations. In Fig- coffee. A good principle to keep in ing Runway 11/29 and circle to the ure 5 (page 12), you want to circle mind is this: circling at an unfamil- left in order to keep the runway vis- to intersecting Runway 23. Because iar airport is a form of IFR Russian ible at all times.
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IFR Refresher, November 1997 13