5
$\begingroup$

I'm currently studying for an IR (US). One of the exam practice questions concerns an IAP having only circling minimums, and references 5-4-20(c) of the AIM, which reads:

Straight-in Minimums are shown on the IAP when the final approach course is within 30 degrees of the runway alignment (15 degrees for GPS IAPs) and a normal descent can be made from the IFR altitude shown on the IAP to the runway surface. When either the normal rate of descent or the runway alignment factor of 30 degrees (15 degrees for GPS IAPs) is exceeded, a straight-in minimum is not published and a circling minimum applies. The fact that a straight-in minimum is not published does not preclude pilots from landing straight-in if they have the active runway in sight and have sufficient time to make a normal approach for landing. Under such conditions and when ATC has cleared them for landing on that runway, pilots are not expected to circle even though only circling minimums are published. If they desire to circle, they should advise ATC.

I'm having trouble understanding the bolded sentence. What does it mean to land straight-in from an approach that is more than 30 degrees from runway alignment?

I've been understanding a circling approach as something like a pattern landing where you start the maneuver once you have passed the FAF and have - and can keep - the runway environment in sight. But this seems to imply something different. What am I missing? What does "a normal approach to landing" mean here?

Improve this question
$\endgroup$

3 Answers 3

Reset to default
6
$\begingroup$

The sentence before the one you bolded, with my bolding applied, says:

When either the normal rate of descent or the runway alignment factor of 30 degrees (15 degrees for GPS IAPs) is exceeded, a straight-in minimum is not published and a circling minimum applies.

So you can have a "circling approach" that is lined up straight in to a runway, but with only circling mins, not straight-in minimums, published. This could be driven by the need for a high FAF altitude, high enough that you can't get from that FAF at that altitude down to the runway, with a descent rate that's within the TERPS criteria. So they build an approach that assumes you maneuver to lose the excess altitude, and give you circling mins so that you can.

However -- and this is what the exception that you bolded in the question is about -- if you're in, let's say a STOL airplane, you may very well be able to lose the excess altitude and be established on a normal visual glidepath to the runway with ample time to make a "normal approach and landing" without any S-turns or other maneuvering required. And in that case you're absolutely allowed to fly the approach straight in. The guy behind you in a Lear Jet may not be able to do the same thing that you did, and the TERPS descent profiles criteria are written to guarantee that if he has straight-in mins, he CAN get from the FAF at its crossing altitude to the runway without having to use what would be, for him, a dangerously high descent rate (angle). But in the STOL aircraft, a steep descent is perfectly normal, so you can go ahead. The Lear shouldn't try to mimic the Maule's descent profile, but that doesn't mean that the Maule has to mimic the Lear's descent profile.

Improve this answer
$\endgroup$
4
  • $\begingroup$ Is this really just about STOL? That seems unusual. There's two cases (plus any combination) that seem to apply. One is a >30 deg heading change from approach to runway. The other is a steep descent. I can see how in a 172 you could do a 1000'/min descent to land no problem. But in the >30 deg case, what does "straight in" actually mean here? Or does it just not apply in that case? $\endgroup$
    – Foster Boondoggle
    Commented Mar 28, 2020 at 4:34
  • 2
    $\begingroup$ It isn't about STOL, but rather 91 vs 135/121 operators. The latter are required to have a stabilized approach by a certain altitude or go missed, whereas the former are limited only by the "careless or reckless" rule and thus have a lot more freedom in how they comply with intentionally vague rules like this. $\endgroup$
    – StephenS
    Commented Apr 5, 2020 at 1:47
  • $\begingroup$ @StephenS, but what count as stabilized approach still depends on whether the aircraft is certified for steep approaches and how steep approaches are permitted, doesn't it? $\endgroup$
    – Jan Hudec
    Commented Jul 3, 2020 at 20:43
  • $\begingroup$ @JanHudec Steep approaches can be stabilized, such as at LCY, but it seems unlikely in the case of circling. $\endgroup$
    – StephenS
    Commented Jul 3, 2020 at 22:12
3
$\begingroup$

If you break out of the clouds with sufficient altitude, you can line up with your desired runway of use before reaching the MAP. You can only do this if you can effect the landing using normal maneuvering procedures. Breaking out of the clouds before the FAF with 10sm or more visibility would be a perfect scenario to deviate from the lateral guidance and line up for the straight-in landing.

You can also request a Contact Approach per AIM 5-4-25.

Improve this answer
$\endgroup$
7
  • $\begingroup$ Aside from the contact approach option, which rumor has it no one ever actually asks for, would you have to request a visual approach instead or cancel IFR? My understanding has been that you're not supposed to deviate from the approach course until the MAP. $\endgroup$
    – Foster Boondoggle
    Commented Mar 28, 2020 at 21:34
  • $\begingroup$ @FosterBoondoggle - Once you are on the approach, you are communicating directly with the tower. You could request anything you want. They are there to help you. Just make sure you stipulate that you are in VMC. That way they do not mistake your intentions for flying a Charted Visual Flight Procedure. See faa.gov/other_visit/aviation_industry/airline_operators/… $\endgroup$
    – Dean F.
    Commented Mar 29, 2020 at 0:38
  • $\begingroup$ @FosterBoondoggle - According to the Aeronautical Information Manual (AIM), a Visual Approach authorizes a pilot flying under Instrument Flight Rules (IFR) to proceed visually to the airport while remaining “clear of clouds.” Clearance for the approach is predicated upon the pilot having either the airport or the preceding identified aircraft in sight and the airport reporting a ceiling at or above 1,000 feet and a visibility of 3 miles or greater. $\endgroup$
    – Dean F.
    Commented Mar 29, 2020 at 0:39
  • 1
    $\begingroup$ @FosterBoondoggle - Is it a separate clearance? In some cases, yes. And, in others, no. We have an IAP at my local airport that has the MAP right at the beginning of the downwind leg of RWY36. This IAP has only circling minima. Albeit, 230 feet lower than the traffic pattern altitude. If I break out of the clouds before reaching TPA, I am not going any lower than TPA until I am abeam my touchdown point. This will not require another clearance besides clear to land if it has not already been given. $\endgroup$
    – Dean F.
    Commented Mar 29, 2020 at 1:12
  • 1
    $\begingroup$ @FosterBoondoggle - if on the other hand, I am cleared to land on RWY18, I could effectively side step to the right (RWY 36 is RP) as long as I break out of the clouds at least 2 miles before the MAP. My instructor would do it in less than 1 mile. Then again, it’s a 7000 foot runway in a C172. Just as long as I remain above the decision height until I can stay out of any clouds and retain suitable visibility. Typically, if the clearance is for 36, ATC will give the instruction to circle East of the field. If for 18, they will instruct to keep the circle North of the field. No further clearance $\endgroup$
    – Dean F.
    Commented Mar 29, 2020 at 1:45
1
$\begingroup$

I think there is some term jumbling here that can likely be cleared up with the statement:

Circling minimums do not necessarily imply you are going to execute a "circle-to-land" maneuver

A circle-to-land maneuver is a low altitude, close to the field, turning maneuver that allows you to use an approach set up for a given runway but ultimately land on another runway.

Circling minimums are added to an approach when the design and topography of the area can guarantee/meet the requirements for a pilot to execute a "circle-to-land" maneuver. This is covered in the FAA's approach handbook:

The circling approach area is the obstacle clearance area for aircraft maneuvering to land on a runway that does not meet the criteria for a straight- in approach. The size of the circling area varies with the approach category of the aircraft... ...A minimum of 300 feet of obstacle clearance is provided in the circling segment. Pilots should remain at or above the circling altitude until the aircraft is continuously in a position from which a descent to a landing on the intended runway can be made at a normal rate of descent and using normal maneuvers. Since an approach category can make a difference in the approach and weather minimums and, in some cases, prohibit flight crews from initiating an approach, the approach speed should be calculated and the effects on the approach determined and briefed in the preflight planning phase, as well as reviewed prior to commencing an approach.

This does not mean that you need to execute a Circle-To-Land maneuver to land, it simply means that you can if you apply the appropriate minimums and it is the maneuver that will get you to the favored runway.

Lets look at a real world example. C66/Monmouth Municipal Airport has a single VOR/GPS-A approach with only circling minimums.

enter image description here

(source)

Now let's say the wind is favoring a landing on runway 21. The Approach does not meet the less than 30 degree offset requirement so straight in minimums can not be added to the design. The circling decision altitude is 1360 which you are likely to cross well outside of 2 miles from the runway. If you cross this altitude and have the runway environment in sight there is nothing precluding you from effectively joining what would be a final approach and flying a straight in approach. which you will have plenty of time and distance for (lets say your flying a 172 coming in at 75 Kts).

Note: Historically the high cost of physically installing a VOR/NDB etc meant that not all of them could align nicely with runways and off-set approaches were more common, leading to the need for circling. With the advent of GPS and the lower cost to have two straight in approaches to a field this has be come less common.

Improve this answer
$\endgroup$
1
  • $\begingroup$ What does "straight in approach" mean in a context like this where you'd basically fly a modified left base, or even a downwind & base (in your rwy 21 example) at 700AGL about 2 miles from the threshold (for a 3deg glideslope) before turning final? This really highlights the terminology puzzle I started with. Does one call a landing pattern involving a base leg close to the field "straight in"? I assume almost everyone is flying their short final "straight in". $\endgroup$
    – Foster Boondoggle
    Commented Aug 19, 2020 at 16:38

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .