There are certain scenarios that simply cannot be accurately or safely trained in flight -- especially in multiengine airplanes. Further, even after attending and completing the Beechcraft Pilot Proficiency Program and other training resources available to Baron pilots, we find that there's greater value in simulator training for the more complex scenarios.
At the Advanced Baron Seminar we explored circling approaches at very low or "minimums" weather. Circles are almost impossible to schedule for a realistic practice session in actual low-viz low-ceilings weather because it's so weather-dependent.
The Circle To Land procedure is a VISUAL maneuver, executed under Instrument Flight Rules. There are number of ways to execute these procedures.
We had discussed circling approaches on the BeechList chatline. This was the procedure that triggered the creation of the Advanced Baron Seminar. We worked with very high winds, with the weather dialed down to 20-100' above MDA. Tough work, but a great learning experience. Myself? I learned a lot. My notes below have been collected from the Advanced Baron Seminar, and the chatrooms of the BeechList, and BeechTalk. I compiled this memo over a decade simply to improve my own understanding of technique. I hope you find it useful. I'm not suggesting that you use these techniques. Intentionally, there is nothing in this memo that suggests WHETHER or WHEN to accept or choose the Circle To Land procedure
THE MOST EXPERIENCED PILOTS ALL SAY:
"Never, NEVER, NEVER! just show up and "wing it"
None of this stuff should be calculated as the maneuver is being flown; these are precise procedures that need to be trained into our minds and routinely practiced, then planned and briefed for the specific destination...and flown precisely.
Simcom's instructors, with full participation of the Seminar attendees (we all building on Old Bob Siegfried, John Deakin, Stuart Spindel, Larry Olson, John Collins, and others) taught me to fly a circle...
1: much like a Hold (ICAO: at Standard Rate Turn or 25deg. bank, whichever is less bank. Below ~180KIAS, that math means: Standard Rate Turns)
2: with FD/AP ON and using ALT HOLD to ensure that the MDA is nailed
3: to use the HDG bug to maneuver around the circle in level flight; staying at MDA until on or very near the extended runway centerline.
4: at a constant Airspeed and using identical banks (because the math works best to standardize the turn radii and make the maneuver work out)
IMPORTANT: Know the Non-Landing procedure. Down low in poor weather, we won't have time to look it up. If we lose sight of the airport ... IMMEDIATELY get out of there. Know the Missed Approach initial heading and altitude.
At 100KIAS (170ft/sec. Five seconds is ~850ft traveled, ten is ~1700 ft,) and a standard turn radius will be ~2900 ft. Bank Angle is approx 15 deg.
At 120KIAS (~200ft/sec. Five seconds is ~1000ft traveled, ten is ~2000 ft,) and a standard turn radius will be ~3500 ft. Bank Angle is approx 17 deg.
Doubling the bank angle, doubles the turn rate and halves the turn radius.
Use an offset buffer to prevent overshoot of Final. That buffer is included early as the maneuver is begun. If we don't need it, we'll give it back on Base or as we are turning Final. The size of the buffer will depend greatly on the winds at pattern altitude.
A Tip: dial your navigator's Map page down to its lowest range so the runway pattern appears. It's a good quick-glance reference for this VISUAL maneuver.
~~~~~~~~~~~~~~ CIRCLING EXAMPLE 1 ~~~~~~~~~~~~~~~~
Circle into a Left traffic pattern to a long runway, with Autopilot ON, HDG mode alive. This example is flown at 120KIAS (~200ft/sec.) with all turns at Standard Rate, so bank angle will be about 17degrees. Slower speeds would result in a tighter circle, as would steeper banks.
Arriving at midfield (configured for landing, except perhaps for Full Flaps) turn just before arrival so as cross the midfield pre-aligned to fly 90 degrees away from the runway—keeping the Touchdown Zone (TDZ) in sight behind the left wing—towards the Downwind leg. Fly five seconds at level flight. That's the buffer (~1000 ft). We'll use it up on the Base leg.
(We could use a ten-second buffer if the visibility is good, but we'd need to give back the same amount of time later on Base leg). Do NOT make the buffer longer than necessary; you'll be pushing the limits of the obstacle-protected area. In very low visibility? Slow down the aircraft! See the math, above.
Then turn the HDG bug 90 Left to parallel the runway. The turn takes 30 seconds, its radius is ~3500 ft. That puts us on Downwind with a ~4500 ft offset. Fly wings level until abeam the Touchdown point, the TDZ.
When ABEAM the TDZ, start a count for five seconds (another ~1000ft) to extend the Downwind leg just a bit. (In very low visibility to a long runway? perhaps skip this step and land long). After the timer runs, turn the HDG bug 90 Left to Base Leg. The turn takes 30 seconds, its radius is ~3500 ft. That puts us on Base at a ~4500ft offset from the TDZ.
IMMEDIATELY...as the wings come level...look to your right for other traffic--this is just a short level segment (using up some of your buffer)--then immediately turn the HDG bug again 90 Left to align with the Final leg. This last turn takes 30 seconds, its radius is the same ~3500 ft. That puts us inbound on Final and now less than the 4500ft offset from the TDZ. Done correctly, we'll probably have to REDUCE the rate of the last turn, as we give back the buffer. (About the last thing we'd want to do, would be: steepen the bank. But we could...as we are only using standard rate banks. Myself, to tighten the radius, I'd slow the aircraft to the 1.3Vso donut on my AoA-equipped aircraft. That also tightens a turn.)
ONLY NOW while completing the last turn and aligned with the runway, may we descend from the MDA. BUT! ... even then....
DESCENT FROM MDA
Wally Roberts (a retired TWA Captain, served as Chairman of the Air Line Pilots Association [ALPA] Charting and Instrument Procedures Committee working with the FAA in approach procedure design and points out that—except when the circling MDA is the lowest permitted by TERPS: 350 HAA (CAT A), 450 HAA (CATs B/C), 550 HAA (CAT D)—there is something sticking up to 300 feet below MDA. If you descend from MDA before being on final, or are very close to being on final, you could hit it...especially when it's dark or rainy out.
~~~~~~~~~~~~~~ CIRCLING EXAMPLE 2 ~~~~~~~~~~~~~~~~
A 180 degree Reversal from a Straight In Approach
We occasionally get an instrument approach with a tailwind. When we need to circle into a Left Hand Traffic pattern (in this example) for an opposite runway end, John Collins--a prominent CFII in North Carolina; a widely-respected aviation author--suggests using a 45R--LevelSegment--45L entry, and that math works, too. We need to ensure that the offset is adequate. That amount depends on the Airspeed flown and the bank chosen. John clarifies:
"I teach a circling technique that is specifically designed with the intention of avoiding the need for the extra bank required by an overshoot. It all has to do with proper spacing from the runway on the circle. For circling to the opposite direction runway after a straight-in approach, I use TIME for spacing myself out to the downwind leg:
"Assuming an airspeed of 120 Kts or less, once inside of the circling area and with the straight-in runway in sight, I make a right turn (assuming left traffic) of 45 degrees. Then I time a 25 to 30 second straight and level leg followed by another 45 degree turn to the left to align with the downwind. The two 45 degree turns have consumed 90 total degrees of turn and spacing and 30 seconds in the turns. The 25 to 30 second level leg gives me the time needed to make another two 90 degree turns later, on the Base leg. So when I am abeam the numbers of the opposite direction runway, I still have 180 degrees of turn remaining to accomplish; I'll use the same bank angle I used to space myself out from the runway. The time can be adjusted for a significant crosswind. The 45 degree turn allows me to keep the airport environment in sight at all times
John comments here on the example above, the Ninety Degree entry from midfield:
"If a pilot flew at 120KIAS for 15 seconds at 90 degrees to the runway, he'd be almost a mile away after completing the turn to the downwind using a 20 degree bank angle. (120 Kts is 120 x 6076ft/3600sec = 202 feet per second traveled. 15 seconds at 120 Kts is 3038 feet traveled.) In a 90 degree turn, the radius is the offset at rollout. At 120 Kts and [my tighter] 25 degree bank, the rate of turn is 4.2 degrees/second and the radius is 2735 feet. Not counting the roll in roll out, the total offset is 5773 feet or 1.09 SM.
"I still would prefer the turn to 45 degrees as it's easier for me to better keep the airport in sight while spacing to the downwind.
"Slowing to 105 Kts is a big improvement (in my Bonanza). I won't need to space myself so far out from the runway. I prefer to limit my bank angle to 20deg. on the turns to downwind, as that leaves the base to final turns easier to manage and I still have a good out of increasing my bank angle to final up to 30 degrees to adjust for winds."
END of MEMO on technique. I'm not advocating any "best way" and am fully open to learning better methods. Please suggest yours, by email below.
~~~~~~~~~ OTHER THOUGHTS from OLD PILOTS ~~~~~~~~~~.
CHEATING: Do NOT! The single most difficult thing about circling in low ceilings weather is flying at MDA just below the bases of an overcast ... especially when it's a bit ragged underneath. The runway will be in sight and the temptation to descend "only 50-100 feet lower" is huge ... and deadly.
DO NOT CHEAT! There are rocks not far below.
AUTOPILOTS: The use of the HDG bug to turn the aircraft should result in a Standard Rate Turn (that is: on any AP I have owned/flown. I gather that some rate-based autopilots won't turn at Standard Rate.)
RIGHT HAND TURNS: My King Air has poor visibility from my pilot seat to starboard, as do several other cabin class aircraft, so a few of us will not fly a Right Hand Circle when solo. An untrained passenger does not count, for me.
FROM A FREIGHT DOG, Is there ice in the lower clouds?: (This from an FAA designated pilot examiner, Airline Transport Pilot rated, Certified Flight Instructor for both Instrument & Multi-engine, Single and Multi Engine Seaplane rating, a glider rating and type ratings in the Citation, CitationJet, B25, DC-3, PBY and authorizations in the P-51, P40, F4-U, F6-F, Zero, and T-28 with an “All makes and models, single and multi-engine piston powered” endorsement.) ...
Doug Rozendaal adds to the subject of circling approaches, suggesting a few of his old "freight hound" tricks;.
"If one thinks there might be significant ice in the lower clouds on final approach to a RWY36, then ask for the ILS to 36, circle to 36. [Yes, that is perfectly acceptable, but descend no lower than your RWY36 Circling MDA...not to the ILS DH].
"It goes like this: Stay above the clouds until the IAF inbound, and pick up the GS in clear on top. Leave the gear up and come down the GS at about 160 KIAS. When you break out, fly up the runway to the touchdown point. Pull back the power, and do a nice 30 degree bank 360 turn. You'll be below gear speed at the 180 degree point and can configure to land.... This minimizes the time spent in the layer, and if the windshield is obscured, you can still see out the side window. Just like a carrier approach or flying a blind-forward taildragger....
"I have 'a friend' who says it works very well..... Frankly if you come down the GS at 160 KIAS, in anything but freezing rain, you will seldom get more than a trace of ice, and NEVER FLY IN FREEZING RAIN..... Needless to say...briefing Approach Control on your plan would be warranted, in case you are following someone, or someone is following you, but out here in Non-radar country (Iowa) it works really well. Practicing this once or twice VMC is warranted before trying it for real.....
"But long before the approach: if you are not hauling freight, and the ceilings are close to, or below circling minimums, with any chance of significant ice, don't fly at all"
MORE "AVIATOR-MATH": John "Tramp" McMurray, a career Air Force pilot/instructor and Bonanza owner offers a few "aviator-math" shortcuts. He says that for those who enjoy doing their own math, the following formulas might prove helpful. The values are approximate but are more than accurate enough to work out the kinds of problems we are solving here.
Std rate turn, bank angle in degrees = KTAS * 1.5 / 10
Similarly... (Knots / 10) + 5 = Bank Angle in degrees
Std rate turn, radius in feet = 32 * KTAS
Std rate turn, radius in nm = KTAS / 200
Doubling the bank angle, doubles the turn rate, and halves the turn radius.
TAS in feet/second = KTAS * 1.7 (ex: 120K x 1.7 = ~200ft/sec)
TAS in nm/minute = KTAS / 60
120 KTAS is 200 feet/ second or 2 nm/minute
For example, at 120 KTAS and a standard rate turn (3 deg/sec):
Bank = 18 deg
Radius = 3840 feet
Radius = 0.6 nm
Increase the bank to 36 deg and the turn rate becomes 6 deg/sec.; the turn radius becomes 1820 feet or 0.3 nm.