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As I recently contemplated 14 CFR 135.223 and its implications, I began wondering about airports with exceptionally low circling minima.

For a little context and background, the part of §135.223 that sparked my imagination is the following exemption clause:

(1) The ceiling will be at least 1,500 feet above the lowest circling approach MDA

This got me thinking along these lines: "How often might one encounter both a circling MDH sufficiently low as to allow exemption from the fuel requirements of §135.223(a) and a ceiling high enough that the requirement of §91.169 to file an alternate airport remained in effect? Such a scenario would require a reported or forecast ceiling of 1900 ft and a circling MDH of 400 ft or less.

I know that there are at least a few airports with MDH of 400 ft or lower (which seems altogether too low). Thus, my question is:

Which airport in the United States has the lowest published circling Minimum Descent Height (MDH) for an instrument approach?

I initially wanted to apply this question equally to any airport worldwide. However, I have chosen to limit the scope of this question for two reasons.

Firstly, ICAO standards are more strict in this area than the TERPS standards that the US, Canada, and a few other parts of the world adhere to. Specifically, the TERPS standards for Cat A prescribe a minimum MDH of 350 ft, while ICAO prescribes a higher minimum of 394 ft.

Secondly, I recognize that discovering an ultimate answer to this question (i.e., "ABCD airport definitively has the lowest circling MDH") is difficult, especially if the question's scope included airports from multiple nations. For this reason, I have chosen to limit the scope of the question to the United States of America, where available databases should provide an opportunity for a definitive answer.

For example, the lowest MDH that I know of is Point Hope (PHO/PAPO) with a circling MDH of 361 ft for both the RNAV RWY 1 and RNAV RWY 19.

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While this might be the lowest published MDH, I don't know whether or not it is.

I am looking for any answer that can factually establish which airport has the lowest published circling MDH, whether that might be Point Hope or some other airport.

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  • $\begingroup$ If your only approach was a circling approach with a 1200' MDA, would 2000/3 get you out of needing an alternate, or in that case would you need an alternate with anything below a 2700' ceiling? $\endgroup$
    – Ralph J ♦
    Feb 3, 2017 at 20:31
  • $\begingroup$ @RalphJ I.a.w. §91.169, given an IAP at the first airport of intended landing, and given a forecast of 2000/3 or greater, no alternate need be filed, regardless of IAP minima. I.a.w. §135.223, given a circling MDH of 1200, and given weather of 2000/3, sufficient fuel to fly to the alternate must be carried. That's what the regs say. I know, it doesn't make sense. $\endgroup$
    – J W
    Feb 3, 2017 at 22:29
  • $\begingroup$ Part 135 operation is not part 91 operation. If you are a pilot in the USA you should know that basic difference. A 135 operator would need 2700' ceiling to avoid planning an alternate if he CMDA is 1200. $\endgroup$
    – Max Power
    Sep 16, 2020 at 23:53
  • $\begingroup$ Part of the problem is that most new approaches use an "assumed adverse obstacle" of 200feet above all terrain, because towers of 199ft do not need to be registered and there are many new cell towers erected each year.(also they don't need to survey every tree) The required obstacle clearance for circling is 300feet, plus the 200ft AAO = 500ft minimum unless some other factor comes in like land that is easy to visually survey for new towers and low potential for new trees, oil derricks or wind turbines in surrounding waters or land. Cat D and E min circling HAA is 550ft $\endgroup$
    – Max Power
    Sep 17, 2020 at 0:21
  • $\begingroup$ @max §135 operations are still subject to §91 regulations in addition to the §135 regulations. §135 itself does not explicitly stated when an alternate need be filed. $\endgroup$
    – J W
    Sep 17, 2020 at 16:29

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I'm going to partially answer this question. According to TERPS Section 2-7-1(b),

the minimum ROC in the circling approach OEA is 300 feet. Adjustments must be applied as specified in paragraph 3-2-2.c.

OEA means Obstacle Evaluation Area, and ROC means Required Obstacle Clearance.

However, according to TERPS table 3-2-1 the minimum HAA (Height Above Airport) is 350 feet for CAT A aircraft.

If you look at the example given in TERPS Section 2-7 -1(c), it shows that the higher of the CMDA is published. Either 300 ft above the an obstacle located within the OEA, OR 350 ft above the airport. The 623 + 300 = 923 which rounds to 940. However, the 600 airport elevation + 350 = 950, but according to TERPS that rounds to 960. So 960 is published. The 960 is equal to a height of 360 ft AGL.

The way that I interpret this is that the lowest possible circling minimum descent altitude would be 360 ft above the airport assuming there are no obstacles in the OEA. However, the lowest circling height I've ever seen is around 440 AGL somewhere in New Mexico. The obstacles are almost always going to dictate the minimum height unless there is an airport on a an elevation with no buildings or antennas nearby.

So, if you find an airport with a circling minimum height of 360 AGL, that is likely the airport with the lowest (or tied for the lowest) circling minimum in the US. The airport you found (Point Hope) at 361AGL is likely one of the lowest if not the lowest in the US.

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  • $\begingroup$ This is a great way to answer the question on how low it can actually be. $\endgroup$
    – wbeard52
    Feb 2 at 21:11

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