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#41
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"John Clonts" wrote
Thanks, this is as I hoped. Somewhere along the way I had picked up a suspicion that I couldn't legally descend from MDA until aligned with the runway. This is often taught as normal procedure but (1) it's not regulatory and (2) on most circling approaches to minimums (meaning visibility minimums) it's either dangerous or just plain unworkable. Look at it this way - the visibility min on most circling approaches is 1 sm. That means that in order to keep the runway in sight, you can't ever get more than a mile from it. That means that your pattern will be 3/4 mile wide, max, if you're not going to exceed 1 sm from the runway when turning base. That means that when you turn final, you have 3/4 of a mile to get down, max. On a 4 degree glideslope (which is about the steepest I would recommend in low vis) that's 300 ft. On a 7 degree glideslope (which is normal power-off 10:1 glide for a light single) that's barely over 500 ft. Circling minimums are usually higher than 500 ft. Does that mean you're going to slip down final with a mile of vis? Are you planning on trying this trick at night too? Personally, I recommend starting the descent early enough that you can maintain a constant and comfortable 3 degree descent (about 500 fpm at 90 kts) all the way to touchdown. When the sky is blue, it's no big deal to pull the power to idle, roll into a maximum effort slip, get down, roll out just before the flare, and put it on the numbers. Any reasonably competent VFR pilot should be able to do it. When visibilities drop below 2 miles, especially at night, with rain and mist, or both, it's really not a good idea. The subtle visual cues that form the true basis for "seat of the pants" flying are gone. As a rule of thumb, if you wouldn't maneuver that way in IMC, don't do it when the vis is less than 2 miles. 2) Once I get to class G airspace on my approach and am clear of clouds in 1 mi vis, can I then descend below MDA by doing something like declaring myself visual, contact, or canceled IFR. If you are actually in Class G and have 1 mile and clear of clouds, you can cancel IFR. IMO this is a suboptimal procedure. For example, suppose that an airplane is holding for release. The moment you cancel IFR, the controller will release it. If you are operating at low altitude in minimum visibility near the airport, do you really want company? A visual approach requires VFR minimums to be issued. I believe you need 3 miles of visibility for that. A contact approach is fine with 1 mile and clear of clouds, and can be issued in controlled airspace. However, if you can see the runway, you don't need a contact approach. On the other hand, if you can't see the runway but can see the ground, are familiar with the area, know where you are, and are confident you can fly to the airport visually while remaining clear of clouds and maintaining 1 mile flight visibility, a contact approach is the way to go. Michael |
#42
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wrote in message ... Your usual fine observations aside, as you well know some IAPs with circling-only minimums are aligned exactly with a runway but don't have straight-in minimums because of descent gradient requirements. This ain't one of 'em. They are set forth in 91.175 as you well know. They? Hmmmm.... They, third-person plural pronoun, hmmmm...... I can find only one reference to circle-to-land in FAR 91.175, and it doesn't apply below the MDA. § 91.175 Takeoff and landing under IFR. (e) Missed approach procedures. Each pilot operating an aircraft, except a military aircraft of the United States, shall immediately execute an appropriate missed approach procedure when either of the following conditions exist: (2) 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. |
#44
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"Michael" wrote in message om... "John Clonts" wrote Thanks, this is as I hoped. Somewhere along the way I had picked up a suspicion that I couldn't legally descend from MDA until aligned with the runway. This is often taught as normal procedure but (1) it's not regulatory and (2) on most circling approaches to minimums (meaning visibility minimums) it's either dangerous or just plain unworkable. Look at it this way - the visibility min on most circling approaches is 1 sm. That means that in order to keep the runway in sight, you can't ever get more than a mile from it. That means that your pattern will be 3/4 mile wide, max, if you're not going to exceed 1 sm from the runway when turning base. That means that when you turn final, you have 3/4 of a mile to get down, max. On a 4 degree glideslope (which is about the steepest I would recommend in low vis) that's 300 ft. On a 7 degree glideslope (which is normal power-off 10:1 glide for a light single) that's barely over 500 ft. Circling minimums are usually higher than 500 ft. Does that mean you're going to slip down final with a mile of vis? Are you planning on trying this trick at night too? Personally, I recommend starting the descent early enough that you can maintain a constant and comfortable 3 degree descent (about 500 fpm at 90 kts) all the way to touchdown. When the sky is blue, it's no big deal to pull the power to idle, roll into a maximum effort slip, get down, roll out just before the flare, and put it on the numbers. Any reasonably competent VFR pilot should be able to do it. When visibilities drop below 2 miles, especially at night, with rain and mist, or both, it's really not a good idea. The subtle visual cues that form the true basis for "seat of the pants" flying are gone. As a rule of thumb, if you wouldn't maneuver that way in IMC, don't do it when the vis is less than 2 miles. 2) Once I get to class G airspace on my approach and am clear of clouds in 1 mi vis, can I then descend below MDA by doing something like declaring myself visual, contact, or canceled IFR. If you are actually in Class G and have 1 mile and clear of clouds, you can cancel IFR. IMO this is a suboptimal procedure. For example, suppose that an airplane is holding for release. The moment you cancel IFR, the controller will release it. If you are operating at low altitude in minimum visibility near the airport, do you really want company? A visual approach requires VFR minimums to be issued. I believe you need 3 miles of visibility for that. A contact approach is fine with 1 mile and clear of clouds, and can be issued in controlled airspace. However, if you can see the runway, you don't need a contact approach. On the other hand, if you can't see the runway but can see the ground, are familiar with the area, know where you are, and are confident you can fly to the airport visually while remaining clear of clouds and maintaining 1 mile flight visibility, a contact approach is the way to go. Michael Excellent elaborations as usual, thanks! John |
#45
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"John Clonts" wrote in message .. .
1) Does "having the runway environment in sight...make a normal landing" in 91.175 mean its ok to descend below MDA, fly a couple more miles to the airport and then fly the pattern (circle to land), as long as the runway is still in sight. FWIW, that's my understanding. If you have the vis and you have the runway environment clearly in sight. Just realize that circling is tricky, and descending then circling doesn't make it less tricky. Also, if the cloud deck is ragged and you lose the airport, what's your plan for how low you will go to stay visual? The "MDA" gives you a firm floor until you have the airport and the vis. Once you start your descent, if you're far enough from the airport that you might realistically lose it if conditions change a mite, what's your personal "floor" and how did you choose it? 2) Once I get to class G airspace on my approach and am clear of clouds in 1 mi vis, can I then descend below MDA by doing something like declaring myself visual, contact, or canceled IFR. Personally, if you have to descend below MDA to stay visual I think I would vote for "none of the above". What if the cloud deck is ragged and something rolls in, you have to go missed? What if there's someone else waiting for the same approach? Or another IFR waiting to be released? I don't see what a contact approach gains you. For visual approach you need 3 miles vis. FWIW, Sydney |
#46
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A visual approach requires VFR minimums to be issued. I believe you
need 3 miles of visibility for that. I think it depends on your AGL altitude. If you're below 1200' AGL outside any magenta circles you only need 1mile vis. and inside the magenta circle you would have to be below 700' AGL and only need 1 mile vis. If it was a class E surface area then you would need 3 miles vis. to get in VFR. I think. Kobra A contact approach is fine with 1 mile and clear of clouds, and can be issued in controlled airspace. However, if you can see the runway, you don't need a contact approach. On the other hand, if you can't see the runway but can see the ground, are familiar with the area, know where you are, and are confident you can fly to the airport visually while remaining clear of clouds and maintaining 1 mile flight visibility, a contact approach is the way to go. Michael |
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