Circling missed approach

[mxalix258]

When circling to land, does the published missed (which assumes you are doing a straight in approach - doesn't it?) still apply and give you appropriate terrain/obstacle clearance?

Say for example the missed approach is a climbing left turn direct to a VOR, but if you circle, and are on final and end up back in a cloud and lose visual with the airport, would you execute a missed approach with a climbing right hand turn direct to the VOR?

 

[Headspace]

It applies provided you're on course. It doesn't apply if you're outside of that. There's a certain number of feet beyond which it does not apply that I cannot recall off the top of my head--it's probably in the TERPS somewhere.

The procedure outlined in the AIM for this is as follows: You need to orient yourself with course by turning in a climb toward the runway of intended landing and thence onto the course toward your MAP as specified on the plate.

 

[poadeleted20]

You can start by reading what the AIM has to say about it.

c. If visual reference is lost while circling-to-land from an instrument approach, the missed approach specified for that particular procedure must be followed (unless an alternate missed approach procedure is specified by ATC). To become established on the prescribed missed approach course, the pilot should make an initial climbing turn toward the landing runway and continue the turn until established on the missed approach course. Inasmuch as the circling maneuver may be accomplished in more than one direction, different patterns will be required to become established on the prescribed missed approach course, depending on the aircraft position at the time visual reference is lost. Adherence to the procedure will help assure that an aircraft will remain laterally within the circling and missed approach obstruction clearance areas. Refer to paragraph h concerning vertical obstruction clearance when starting a missed approach at other than the MAP. (See FIG 5-4-28.)

Basically, the published missed guarantees obstruction clearance only if executed from the missed approach point on the final approach course. If you've commenced your circling maneuver, you are on your own to get back to that position before heading out on the missed approach procedure. Of course, as long as you're within the circling approach area:

...and above MDA, you are guaranteed obstruction clearance while you maneuver back like that, but once below the MDA, you are no longer guaranteed that until you are back above MDA. For that reason, it is unwise to descend below MDA on a circling approach until you can see everything on the path from where you are to the runway -- hence, the reluctance of many (and the prohibition by many airlines) to execute circling approaches at night.

 

[aterpster]

...and above MDA, you are guaranteed obstruction clearance while you maneuver back like that, but once below the MDA, you are no longer guaranteed that until you are back above MDA. For that reason, it is unwise to descend below MDA on a circling approach until you can see everything on the path from where you are to the runway -- hence, the reluctance of many (and the prohibition by many airlines) to execute circling approaches at night.

Then, there are IAPs where the MAP is well prior to the airport.

http://aeronav.faa.gov/d-tpp/1304/05416LDAD1_18.PDF

 

[RussR]

Yes, if you're circling and need to go missed, you're pretty much on your own. It can be a pretty seriously dangerous situation, as you're not guaranteed any kind of terrain clearance, see Wally's TVL example.

 

[SbestCFII]

You should be OK as long as you are circling inside of the minimum visibility requirement distance of the airport, but if you lose visual contact witht he airport, then you should make a climbing turn in the (last known) direction of the runway and then execute the missed approach. be sure to check both the IAP and NOTAMs for that airport to get restrictions on circling.

 

[poadeleted20]

You should be OK as long as you are circling inside of the minimum visibility requirement distance of the airport, but if you lose visual contact witht he airport, then you should make a climbing turn in the (last known) direction of the runway and then execute the missed approach. be sure to check both the IAP and NOTAMs for that airport to get restrictions on circling.

While this is true, sometimes the visibility requirement is a lot less than the allowable distance for circling per the AIM (see figures above). In many cases, the turn radius of the aircraft at a good speed for maneuvering won't allow staying that close. That's an important point to discuss when training folks for circling to land -- often, the published minimum vis isn't enough to execute the maneuver safely. Also, per the AIM, you want to be familiar with any ODP's for that airport, as they may provide important guidance if you have to go missed from below MDA, which can happen when you're dealing with a high circling MDA, like with a HAAof 1000 or above.

 

[gismo]

While this is true, sometimes the visibility requirement is a lot less than the allowable distance for circling per the AIM (see figures above). In many cases, the turn radius of the aircraft at a good speed for maneuvering won't allow staying that close. That's an important point to discuss when training folks for circling to land -- often, the published minimum vis isn't enough to execute the maneuver safely. Also, per the AIM, you want to be familiar with any ODP's for that airport, as they may provide important guidance if you have to go missed from below MDA, which can happen when you're dealing with a high circling MDA, like with a HAAof 1000 or above.

For a fairly good approximation of the diameter of a turn (distance from downwind to runway for a 180° turn to final) divide TAS by 10, square that and multiply by 3. At 100 KTAS that's about 3000 ft, at 80 it's close to 2000, and at 120 KTAS, nearly 4500 ft.

 

[poadeleted20]

For a fairly good approximation of the diameter of a turn (distance from downwind to runway for a 180° turn to final) divide TAS by 10, square that and multiply by 3. At 100 KTAS that's about 3000 ft, at 80 it's close to 2000, and at 120 KTAS, nearly 4500 ft.

I think that's turn radius, not diameter. And that's at standard rate (3 degrees/second). You also have to allow enough distance to get lined up on final at a reasonable distance from the runway, and also to allow for both the turn off the final approach course to parallel the landing runway and then a full diameter back to final for that runway, so you may need to be starting the circling maneuver at least three radii (and probably more to all for some looking/reaction time) from the landing runway.

 

[gismo]

I think that's turn radius, not diameter. And that's at standard rate (3 degrees/second). You also have to allow enough distance to get lined up on final at a reasonable distance from the runway, and also to allow for both the turn off the final approach course to parallel the landing runway and then a full diameter back to final for that runway, so you may need to be starting the circling maneuver at least three radii (and probably more to all for some looking/reaction time) from the landing runway.

Nope, the formula and examples were for turn diameter in a 30° bank which is what I use for circling approaches. Using a standard rate turn the relationship between KTAS and radius becomes linear and the ratio is about 32. E.G. at 100 KT the radius would be 3200 ft and the diameter would be 6400 ft.

 

[poadeleted20]

Nope, the formula and examples were for turn diameter in a 30° bank which is what I use for circling approaches. Using a standard rate turn the relationship between KTAS and radius becomes linear and the ratio is about 32. E.G. at 100 KT the radius would be 3200 ft and the diameter would be 6400 ft.

OK, that works for 30 bank, but since you don't ever want to go over 30 bank during a low-vis circling maneuver, that's a bad target for which to aim -- better to leave yourself a little slop, say by aiming for 25 bank. If you aim for 30 and miss a little steep, you can find yourself in a serious sinkhole in a big hurry -- I see that all the time during IR training.

 

[RussR]

For a fairly good approximation of the diameter of a turn (distance from downwind to runway for a 180° turn to final) divide TAS by 10, square that and multiply by 3. At 100 KTAS that's about 3000 ft, at 80 it's close to 2000, and at 120 KTAS, nearly 4500 ft.

Am I missing something?

100/10 = 10
10 squared = 100
3x100 = 300

Do you mean multiply by 30?

 

[Dave Siciliano]

Yep. We did dozens of those at SIMCOM last week after we finished the required schedule. One can really get turned around. The entire time, you need to keep oriented to the runway your missed was on and figure how to get back on it if need be. Not as difficult with a GPS, but one has to realize where the published missed is. Easiest manner in general is get back over the airport environment (as has been said) turn to original runway heading and get on the published missed (exceptions should be noted if there.) For instance, in some places one can't circle over certain parts of the runway.

Best,

Dave