Originally Posted by Capn Bloggs
It all depends on how sacrosanct your stabilised approach criteria is. If you need to be stabilised at 500ft AGL on final, you must turn base abeam that point (ie 1.6nm/2900m/40sec at 140GS). It is impossible to remain within circling visibility criteria from the threshold (we need to keep the runway environment in sight; not withstanding metallic obstacles to vision!) while still complying with the turn point.
OK, I’m sure that I’ll get hammered for going on and on – well, I’m used to it by now – but if anyone feels the need to post their objections … fire away:
Capn Bloggs, generally I agree with your statement that … “it depends on how sacrosanct your stabilized approach criteria is…” HOWEVER … I’m sure you would agree that there is no requirement to fly a “squared” traffic pattern (with a downwind, base, and final approach legs) as part of a circle-to-land maneuver. In fact, the pilot is free to maneuver the airplane over virtually any ground track as long as the airplane stays within the circling area and the pilot is cognizant of the referenced obstacles (respecting their location and height) and complies with all the regulatory requirements applicable to the task. Again, while the requirement used to say essentially what is currently said in many other regulatory agencies, but today, in the US at least, the requirement is (and I quote) “…the pilot may not exceed visibility criteria or descend below the appropriate circling altitude until in a position to make a descent to a normal landing.” That does not say that the airplane has to be physically “on” or “above” the final approach path before leaving the MDA – BUT, the requirement DOES say that a “normal rate of descent” is required. Of course, there is no way that I believe having a wide-body airplane wallowing around “down in the weeds” on a circle-to-land authorization is anything close to being a wise decision. I think, as an industry, we were pushing the limits of this particular clearance when we were flying DC-9s and old generation B-737s and B-727s. I think that once we got into the size of a B-757 we had passed into the very gray area of circle-to-land maneuvering – of course that is a highly personal observation – and I understand that various regulatory authorities tend to continue to approve these kinds of approaches for anything with wings. Also, typically, the circle-to-land maneuver is initially taught and evaluated in a simulator. As everyone knows simulators come in a whole litany of visual capabilities … some have VERY restricted visual systems (from having them only directly in front of each pilot – with no cross-cockpit visual capability) all the way to a continuous 220 degree horizontal (essentially visual capability from wing-tip to wing-tip) by 60 degree vertical field of view (mostly with 25 degrees “up” and 35 degrees “down” – and, of course, there are
some variations) all of which is optically correct for both pilots.
There have been operators who have simulators with the more restricted fields of view but who also want to train crews on circle-to-land, and result to exerting a lot of pressure on their respective approving authority … and sometimes this approval is granted. But, in the US at least, each simulator is evaluated and qualified for specific usage by the National Simulator Program staff – a part of FAA's Flight Standards Service. As a part of these evaluations and subsequent qualification, no simulator will be qualified for the circle-to-land task UNLESS the evaluation of that specific simulator has included the evaluation of a successful circle-to-land maneuver, while complying with the regulatory requirement - again, which used to say what is said on some other regulatory environments, but in the US, it clearly states that “an identifiable portion of the airport remains continually in sight throughout the maneuver (except for airplane geometry issues)" and it presumes that the airplane is at it's maximum weight and the maneuver will not be flown unless the minimum visibility authorized for such an approach is reported. Then, as part of the official paper work accompanying the qualification, the specific airport and specific runway combinations evaluated for this task will be clearly indicated for that specific simulator. This is particularly accomplished to ensure that the circle-to-land function may be properly and appropriately conducted in that specific simulator – ensuring that the regulatory requirement that “Whenever an identifiable part of the airport is not distinctly visible to the pilot during a circling maneuver at or above MDA, unless the inability to see an identifiable part of the airport results only from a normal bank of the aircraft during the circling approach … the pilot must execute a missed approach ... and doing precisely that will be completely in compliance with the rules. With the qualification including this specific information, applicable to this specific simulator, the airline or training facility is free to seek approval from the regulator for other operating limitations and requirements, including circle-to-land procedures. But I will also point out that there have been some very “red” faces on some FAA inspectors and some airline or training provider management personnel after it became apparent that the training or checking was not conducted in compliance with these rules.
It is my contention that this particular practice is part of the developing of a “cheat sheet” approach to operations – almost all of which have been developed almost exclusively to allow, or at least assist, pilots in passing check rides and showing satisfactory progress during training. Unfortunately, when a pilot demonstrates his/her ability to perform any task for an FAA Inspector OR for a Company Check Airman, and is
passed on that check, that pilot invariably feels supremely confident in performing that same set of procedures during normal line operations. However, if the simulator task was dependent upon starting a stop watch when passing the approach end of the landing runway, continuing to fly for some designated number of seconds toward a black void, using only the flight instruments for reference (i.e. NOT maintaining visual contact with the airport), then turn a prescribed number of degrees for some other specified number of seconds on that stop watch, and then again turn to the runway heading, anticipating the airplane to be aligned with that landing runway … and now that identical procedure is performed in an airplane, THAT is absolute folly, if for NO other reason than it is performed in direct opposition to the regulatory requirements – in the US at least – and may lead to the ultimate penalty for doing so. And it is for THAT reason that members of the FAA’s National Simulator Program staff will not qualify a simulator for circle-to-land UNLESS it can be accomplished completely in accordance with the regulations.
If, in accordance with company procedures, the pilot must have the airplane
stabilized on final approach, on or approaching the glide slope (visual or electronic) while still at an altitude no lower than circling minimums (and a good share of the approach plates I’ve seen that authorize “Circle” show that to be somewhere between 400 and 500 feet AGL for Category C airplanes – and of course there are exceptions on both sides of that range) then that pilot is going to have to allow for the course intercept, final flap configuration, final airspeed and final descent rate adjustments PRIOR to initiating a descent – which, with little doubt would increase the difficulty of completing the task successfully. However, on most of the approach charts with which I am familiar, the circling MDA is equal to or almost equal to, the altitude that should be cross-referenced at the MM if flying a precision approach to that same runway, ON the glide slope. Those charts show the location of the MM to be at a point on the final approach course at a distance from the runway threshold of between 0.9 and 1.2 NM – meaning that the altitude flown during the circle-to-land would intersect the ILS glide slope at a point inside of, and therefore closer to the runway, than the visibility limit, which is usually between 1.5 and 1.6 NM. Also, since those distances are to the runway threshold, should there be an approach lighting system installed for that particular runway, or other identifiable airport structures, lights, etc., the final visual alignment should present even less of a challenge. However, let me quickly say that a circle-to-land is, in my opinion, a VERY challenging task under the best of conditions, and I am NOT attempting to “make lite” of the knowledge and proficiency requirements involved. But, if the pilot has maintained an identifiable portion of the airport throughout the circle, regardless of the ground path flown, and is of the opinion that he/she may begin a “normal rate of descent to the landing runway” prior to fully aligning with the final approach course, he/she is permitted to depart that MDA altitude
while finally aligning with the landing runway. These requirements are not cavalierly chosen nor intended to be indiscriminately flown – but they do not allow continuing with the procedure when an identifiable portion of the landing airport cannot be continually maintained.
It is my understanding that as long as a company chooses to do so, they may set specifically designed minimum criteria for a circle-to-land maneuver, and as long as they do not violate any regulatory requirement (including the requirements posted on the approach plate) and can obtain appropriate authorization from their assigned regulatory authority, they may do just that. Again, my reason for jumping into this thread is to offer an observation that, in my experience, is becoming all too frequent … the development of a procedure that works – or generally works – in a simulated environment – but leaves out one or two or more very specific requirements that are more than likely to appear in the real world. I call these “sometimes-they-work” solutions “cheat sheet” approaches to getting through training and/or passing tests … and unfortunately, I am beginning to see this occur with much greater frequency … and it’s something that I think any professional pilot should be aware of and avoid at all costs.