When Higher Approach Minimums > Lower Approach Minimums: A masterclass in Meteorology, Technological Limitations, Crew Resource Management (CRM), and Threat and Error Management (TEM), specifically highlighting how a crew can pivot from a repetitive threat to a creative analytical solution.
Preflight and Weather: In the flight deck, the line between persistence and “get-there-itis” is often blurred by the comfort of a familiar approach and strategy. The deteriorating weather conditions at Tweed-New Haven Regional Airport (KHVN) was a known threat to both the pilots and dispatcher, who had diligently planned and dutifully filed a destination alternate. Sufficient uplift fuel was added to account for the alternate, required reserve with a generous amount for holding. The latest weather report prior to landing showed winds at 220° at 06 knots, 2sm visibility, mist, broken cloud later at 300 ft., and a temperature and dewpoint of 08°C.
The Three Approaches and Finally a Landing: The ILS approach for RWY 2 was selected despite the 6-knot tailwind since this approach offered a Decision Altitude (DA) of 294 feet. Unfortunately, after two consecutive missed approaches on the ILS RWY 2, the crew found themselves in a holding pattern. The captain who was pilot monitoring (PM), proposed a third attempt at the same approach and elaborated that if the third attempt is unsuccessful, we shall proceed to our filed Alternate Airport. The first officer shared some concerns and offered his suggestion. Since the field conditions remained unchanged, the first officer shared that a third attempt at the same ILS approach will once again result in a missed approach given the static weather conditions. The first officer added that the lower amounts of mist and cloud density north of the airport, and approach path over land makes it favorable for the RNAV (GPS) RWY 20 approach with an LNAV/VNAV DA of 522 feet (Despite the DA being 228 feet higher than the ILS RWY 2 approach). After some debate, the captain agreed with this assessment and the pilots set-up and briefed the RNAV (GPS) RWY 20. Approximately 3.5NM from the runway, the pilots were pleased to break-out and witness 2-white and 2-red on the precision approach path indicator (PAPI) along with the runway edge lights. A normal approach to landing followed with the passengers overjoyed to deplane at their destination airport and not an alternate.
The Meteorology: The approach path for the ILS RWY 2 took the aircraft over the Long Island Sound which makes conditions ripe for both advection fog (humid air parcel over cold water body) or steam fog (cold air over warm water body). This localized micrometeorological phenomenon was hindering the aircraft from making a successful approach and landing. Surface friction over land creates turbulence that can help break up low-level stratus/fog, whereas the smooth, cool surface of the Long Island Sound stabilizes the air and thus keeps the fog intact.
ASOS Instrument Errors and Limitations: The Automated Surface Observing System (ASOS) Laser Beam Ceilometer (LBC) determines cloud height and coverage by measuring the return time of a vertically aimed laser, yet it possesses several critical limitations that pilots and meteorologists must consider. Because the sensor only looks directly overhead and relies on a 30-minute weighted average to estimate total sky cover, it can produce “false” reports if a single cloud lingers over the sensor or if rapidly moving convective weather causes a lag in reporting. The primary technical constraints include a narrow field of vision that cannot detect nearby hazards like cumulonimbus or funnel clouds, and an inability to identify the nature of the clouds (e.g., distinguishing between fair-weather cumulus and thunderstorms. Furthermore, LBCs are prone to erroneous readings during precipitation (where rain or snow may trigger lower-than-actual cloud heights), and the physical lens is susceptible to environmental contamination (e.g., dust or bird droppings) that can result in “sky condition missing” reports (AOPA Air Safety Foundation, 2001).
The ceilometer has a significant blind spot, i.e., it only sees what is directly above the location site and is limited by temporal averaging and spatial gaps. The LBC transmits a vertical laser pulse and measures the time it takes for the light to reflect off cloud bases back to the receiver. The METAR for the event (KHVN 081559Z) reported BKN003 (Broken clouds at 300 feet). While technically accurate for the sensor's location, this highlights a critical limitation of the ASOS that every pilot should remember. In this case, if a localized fog bank sits over the approach end of a runway (especially one near water), the ceilometer located mid-field may report a much higher ceiling than what the pilot encounter at the Decision Altitude (DA). The image below highlights this limitation:
In this image, while the ASOS reports broken clouds at 300ft. over Francis S. Gabreski Airport (KFOK), an approach for Runway 24 may proceed visually with unrestricted visibility and no ceilings over the north-half of the airport. However, both the TACAN RWY 6 or RNAV (GPS) RWY 6 will most likely lead to a missed approach outcome.
The Strategic Pivot—Land vs. Water: The first officer recognized and voiced his concern—the weather conditions were static. This decision-making skill was rooted in a sophisticated understanding of local meteorology. While the ILS offered lower minima, its path over water (a known source of moisture and low-level advection fog) was the primary threat. By opting for the RNAV approach over land, the crew exploited better visibility and higher ceilings caused by surface heating and terrain friction, eventually catching the PAPI lights 3.5nm out. This is a prime example of TEM—Threat: low ceilings/fog over water, Error: repeating a failed strategy, and Management/Mitigation: tactical switch to an over-land approach path. By switching to the RNAV RWY 20 approach, the crew not only avoided the fog but also traded a 6-knot tailwind for a 6-knot headwind, providing an added safety buffer especially when landing a Boeing 737-800 on a 5,600-foot-long wet runway.
Crew Resource Management (CRM): Instead of passive compliance, the first officer utilized inquiry and advocacy. By suggesting the RNAV approach to the opposite runway, the first officer effectively mitigated the threat of a third missed approach, which would have further depleted fuel reserves and increased crew fatigue.
Of course, success of this flight hinged on the captain’s commitment to a shallow power gradient, and transforming the cockpit from a hierarchy into a highly functioning team. By fostering a safety attitude long before the landing gear was pinned, the captain ensured that the first officer felt not just permitted but professionally obligated to challenge the “try-again” bias. When the first officer advocated for the RNAV approach, the captain’s professionalism was evidenced by an obvious lack of ego, prioritizing flight safety over personal persistence, and actively listening to the technical merits of the land-vs.-water observation. This culture of mutual respect allowed the crew to break the cycle of repetitive errors, proving that a leader’s greatest tool is the ability to listen when the environment demands a change in strategy.
Lessons Learned: This successful landing wasn't just about stick-and-rudder skills, it was about situational awareness. The crew recognized that the ASOS data was a localized “snapshot” that didn't account for the land/water dichotomy. When faced with conflicting information, i.e., ASOS vs. reality outside your windscreen, use CRM to advocate for a change in strategy before you’re forced to head to your alternate.
This scenario highlights the importance of knowledge, critical thinking, problem solving, and decision making in aviation. Command Authority is not about being right, but about ensuring the best information is used to make the right decision. When the destination airport is reporting low IFR (LIFR) weather conditions, conventional wisdom suggests that pilots choose an instrument approach with the lowest minimums. While this makes sense in most scenarios, there are exceptions and this article highlights one such exemption, meteorology, instrument errors and limitations, Crew Resource Management (CRM) and Threat and Error Management (TEM), and overall safe outcome of a flight.
Aside from land/water temperature differences, what other geographical features at your frequent destinations have you noticed consistently “trick” the automated weather reporting?
References: Air Safety Foundation, 2001: ASOS Automated Surface Observing System (Safety Advisor Technology No. 2). Aircraft Owners and Pilots Association (AOPA) www.aopa.org/-/media/Files/AOPA/Home/News/All-News/2001/2000-Annual-Report-of-the-Aircraft-Owners-and-Pilots-Association/sa09.pdf
