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Circle To Land

Mon Nov 17, 2003 2:09 pm

I understand that "circle to land" feature consists when you are doing a Standart ILS approach, to lets say Runway 18, and you are supposed to land in 36, but the ILS approach in 36 does not exist or is limited by terrain, so you begin a ILS approach to rwy 18, but the ATC clears you to land in 36.

What are the procedures when you are in the ILS approach for that runway, and then you have to make a left or right turn to begin a Visual?

What are the minimuns?

What are the speed limits?

In what cases is this "circle to land" feauture more used?

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RE: Circle To Land

Mon Nov 17, 2003 3:29 pm

A circling approach is conducted when you gain visual reference and can not make a normal descent to land on the chosen runway from your current position.

In a nutshell, when circling to land, you fly the traffic pattern as much as possible, and remain at or above the circling MDA until you are continuously in a position from which a descent to land can be made at normal descent rates and with normal maneuvers. Depending on the position of the landing runway and the aircraft, the exact maneuver will vary, generally it is the shortest path from the current position to the downwind or base leg of the landing runway. The pattern can be either left or right at the pilot's discretion, though a control tower will often specify how they want you to circle.

Circling minimums vary according to the approach type and terrain/obstacle considerations. Circling minimums are usually higher than straight-in minimums.

There is no speed limit specifically for circling approaches, just the usual airspace speed limits, 250 knots below 10,000 MSL and 200 knots within 4 miles of the primary airport of class C or D airspace below 2,500 AGL.

There are category speed limits which define various minimums for the approach. The speed at which you fly the circling maneuver defines the minimums required, they vary for each approach, and may be the same for each category. Example: less than 91 knots is category A, 91-120 knots is category B, 121-140 is category C, 141-165 is category D, 166 or greater is category E. Contrary to what many people believe, the category you use depends on the speed you are currently flying. This means that if you are bombing along in your C172 at 141 knots, you must use the category D minimums, even though approaches are usually flown at 90 knots.

Circle to land is used whenever the chosen approach does not put you in a position from which you can execute a straight in landing on the chosen runway. Many non-precision approaches have the missed approach point right over the center of the airport. If you break out there, you're not going to be able to land straight in on any runway and must circle. Some approaches are not aligned with any runway at all, and only have circling minimums. However, if you break out early enough, you can enter into a straight in approach on a runway.

Hope that made some sense.
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RE: Circle To Land

Mon Nov 17, 2003 3:46 pm

...ditto above.. and if I remember correctly, the circling minimums are based on remaining within 1.3 miles of the runway.
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RE: Circle To Land

Mon Nov 17, 2003 4:01 pm

Circle to Land approaches like the ones Ralgha mentioned above are denoted with a letter designation(such as VOR-A,B,C) rather than a specific runway (VOR-30L). Usually these are given when the approach path is more than 30 degrees from a runway heading. On precision approaches the minimums are higher. These are handy when an airport might have only 1 ILS and the winds favor landing in the other direction, or to save some time and approach a non-active runway if permitted rather than get vectored out and around to the other side of an airport. Many airports that have multiple approaches or terrain issues will denote this with "circle to land not authorized" on the approach plate.

Just to give you a little insight into this, I happen to have my approach plates handy. The airport I fly out of, St. Louis Downtown (CPS) has three approaches but they all are for rwy 30L. The ILS straight-in decision height is 612ft and 1/2mile visibility. To circle to 12R or L, 4-22 etc, the Minimum Decent Altitude(MDA) goes up to 940 and you must have 1 mile vis for category A & B. Category C increases these to 1000ft and 1 1/2 miles, D 1080ft and 2 miles respectively. You may say that 300 feet isn't much, but when it's getting foggy like it is right now that extra altitude is all the difference in the world. Most ILS approaches will get you to 200 feet AGL before the DH. Circling approaches keep you around 600 feet AGL because they are considered to be a non-precision approach. They have no glide slope reference once you begin the circle.

Why would you risk the circling approach and not just do the straight in? It's very handy when your ground speed in that 172 is 140kts because of a raging tail wind. More often than not the extra altitude isn't critical for clouds around here. I would rather take a runway that assures the safest possible touchdown. One more thing to consider is that the circling altitude is usually MUCH lower than pattern altitude. CPS has a pattern at 1200MSL(800AGL), yet cirlcing minimums allow you to go as low as 940MSL (500AGL). That's 300 feet closer to the roofs of surrounding homes and trees. Keep it tight and get on the ground when doing a circle to land.
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RE: Circle To Land

Tue Nov 18, 2003 11:02 am

We do circling approaches into Fukuoka, Japan, where there are mountains all around, on two sides of the airport. We do the ILS and break off to the right for a circling approach. Sometimes you have no choice and cannot land from the other direction, so a circle to land is the only option.

Different countries have different circling areas, and each airport will have different minima. Our company also has it's own minima which we must always stick to. In my airline, it's 1000ft AAL, with a viz of 4600M or more. We must adhere to the higher of either the company minima or the Jepps minima.

Circling areas are bound according to the rules they use in a particular country. PANSOPS is used in Australia, Bahrain, China, France, Germany, India, Indonesia, Italy, Malaysia, Netherlands, New Zealand, Pakistan, Philippines, Saudi Arabia, Singapore, Switzerland, Thailand, USE, UK and Vietnam, on our routes, and for an airport at sea level, the radius is 5.02NM from both ends of the runway, and 394ft above the highest obstacle.
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RE: Circle To Land

Tue Nov 18, 2003 11:02 am

Usually these are given when the approach path is more than 30 degrees from a runway heading.

This is true, but it is not the only time that a circling approach is warranted. Another situation is when "normal" descent rates cannot be used to reach the runway from the MDA. The VOR DME-A into Roanoke, VA is a great example of this. This final approach course is 233 degrees, only 4 degrees from the runway heading of runway 23. However, due to the terrain, you must maintain about 1500 feet AGL (1464 to be exact!) until only 1.9 miles from the missed approach point, which is at the runway threshold. In order to be on a 3 degree glidepath, you would have to be at about 500 feet AGL at that 1.9 mile point. Obviously, a straight in to runway 23 would not be advisable.

I made the mistake of forgetting this one night in my trusty Dash 8... It was late, raining and the ILS to 33 was out of service. I forgot this was an "Alpha" approach and attempted to land straight in on from the VOR DME-A approach... I ended up going missed. Had I remembered that this was meant to be a circling approach I could have planned better and avoided the embarrassment. Oh well...
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RE: Circle To Land

Tue Nov 18, 2003 11:05 am

Canada, Korea, Taiwan and the USA follow FAA TERPS, which is a radius of 2.3nm from both ends of the runway, and 300ft above the highest obstacle. This makes for quite a small, tight circling area.

Japan has it's own rules, JAPAN TERPS, this is 2.5nm from the end of both runways and 300ft above the highest obstacle.

I also forgot, that with PANSOPS, an airfield above 2000ft from sea level, the circling area is 5.28nm from the end of both runways.

RE: Circle To Land

Tue Nov 18, 2003 11:11 am

When it comes to night circling approaches, to minimums, in a jet...
Well let's just say that it would take more cajones than I have and I'm fearless. We train for them, but we NEVER do them at night. For us, it's a daylight operation only.

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RE: Circle To Land

Tue Nov 18, 2003 11:21 am

Doing the circling approach into Fukuoka on a dark stormy night with 400 people on board, and big mountains all around you onto a short runway is not that pleasant, but fortunately I don't seem to get the FUK trips much!
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RE: Circle To Land

Tue Nov 18, 2003 1:49 pm

Wasnt that the cause or a factor in the G-III crash at ASE a few years back?

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RE: Circle To Land

Tue Nov 18, 2003 4:13 pm

They performed the approach at night and it's not authorized then. I can understand why. The airport elevation is 7800msl and you have 10-14,000ft peaks all around. No thanks.

"The Board's full report is available at http://www.ntsb.gov/Publictn/publictn.htm .

On March 29, 2001, about 1901:57 mountain standard time, a Gulfstream III, N303GA, owned by Airbourne Charter, Inc., and operated by Avjet Corporation of Burbank, California, crashed while on final approach to runway 15 at Aspen-Pitkin County Airport (ASE), Aspen, Colorado. The charter flight had departed Los Angeles International Airport (LAX) about 1711 with 2 pilots, 1 flight attendant, and 15 passengers. The airplane crashed into sloping terrain about 2,400 feet short of the runway threshold. All of the passengers and crewmembers were killed, and the airplane was destroyed. The flight was being operated on an instrument flight rules (IFR) flight plan under 14 Code of Federal Regulations (CFR) Part 135.

The National Transportation Safety Board determines the probable cause(s) of this accident as follows:

the flight crew's operation of the airplane below the minimum descent altitude without an appropriate visual reference for the runway.

Contributing to the cause of the accident were the Federal Aviation Administration's (FAA) unclear wording of the March 27, 2001, Notice to Airmen regarding the nighttime restriction for the VOR/DME-C approach to the airport and the FAA's failure to communicate this restriction to the Aspen tower; the inability of the flight crew to adequately see the mountainous terrain because of the darkness and the weather conditions; and the pressure on the captain to land from the charter customer and because of the airplane's delayed departure and the airport's nighttime landing restriction."

The approach procedure now reads that it is not authorized at night. I can't get the link, but AOPA has a copy of the IAP in PDF format if you wish to look at it. It only works for members. Hope that helps. Gotta love search engines  Smile

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