An actual instrument approach to minimums

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During your instrument training, and likely as part of ongoing currency or an instrument proficiency check (IPC), you routinely fly instrument approach procedures to “minimums” under simulated conditions. In the case of a precision approach, this would be to the decision altitude (DA). On a non-precision approach, this would be at the minimum descent altitude (MDA) and the designated missed approach point.

As part of the training routine, at the missed approach point the instructor or safety pilot would typically either call the runway in sight at which point you would transition to landing or call for a missed approach to be flown. This is good practice because a) it is rarely done during your everyday flying b) it is the ultimate test of your basic attitude instrument flying and procedures and c) it demonstrates your capability in handling a stressful, task-heavy scenario in close proximity to the ground.

The more likely scenario when flying under instrument flight rules (IFR) is the option to complete the flight under visual flight rules (VFR), flying a visual approach procedure, or flying an instrument procedure in which you acquire the runway visually well above the charted “minimums.”

Needless to say, I was surprised to be faced with a scenario in which the weather was forecast to be at or below approach minimums on a recent leg from Florida to Cincinnati (KLUK – Cincinnati Lunken Airport). A stationary front with a lot of moisture resulted in a temperature and dew point at an identical 11°C and low IFR conditions. In plain language, it was a soupy mess throughout the Ohio valley in which the morning fog was replaced by mist and low-level clouds.

The fact that low IFR conditions existed throughout the region also made identifying a legal and practical alternate airport a challenge. As a refresher, § 91.169 (IFR flight plan: Information required) requires an alternate airport be filed if, from one after before to one hour after the estimated time of arrival, the ceiling (lowest broken or overcast layer) will be below 2,000’ or the visibility less than 3 statute miles. To be eligible as an alternate airport, if the airport has a precision approach, the ceiling must be at least 600’ and visibility at least 2 statute miles at the estimated time of arrival to the alternate.

In our case, the Lexington Blue Grass Airport (KLEX) met the alternate approach criteria. But to comply with § 91.167 (Fuel requirements for flight in IFR conditions), we had to plan for enough fuel to fly to our intended destination and then fly to the planned alternate airport plus an additional 45 minutes. And we also planned for enough fuel to execute an approach procedure at each airport and considered additional time for vectors and even a potential delay as low IFR conditions can create congestion in busy terminal airspace such as Cincinnati. As you can imagine, this resulted in a substantial increase in fuel required for the flight which we were thankfully able to accommodate.

With our planning complete and passengers aboard, we departed the clear skies and warmth of Florida for the cool cloudiness of the Midwest. Monitoring the destination enroute courtesy of ADS-B, the ceiling and visibility was maintaining just above minimums as forecast. However, after briefing the RNAV (GPS) Rwy 21L approach and beginning our initial descent for Cincinnati, the latest METAR indicated a ceiling and visibility just at landing minimums.

 

KLUK 062002Z 00000KT 3/4SM R21L/5500VP6000FT BR OVC003 11/11 A2998 RMK AO2 T01110111

 

While the procedure for the RNAV (GPS) RWY 21L indicates a DA of 756’ (281’ above the airport), a FDC NOTAM raises the DA to 797’ (322’ above the airport) – always check NOTAMS!

 

FDC 1/3864 LUK IAP CINCINNATI MUNI/LUNKEN FLD, CINCINNATI, OH.

RNAV (GPS) RWY 21L, AMDT 1D…

LPV DA 797/HAT 322 ALL CATS.

We were able to learn through ATC that aircraft were still landing at Lunken airport in spite of the most recent METAR with multiple pilot reports that the weather conditions were “right at minimums.” Given this information, and plenty of reserve fuel, we opted to continue to our planned destination as opposed to diverting to our alternate.

After a magnificent vector from the controller (thank you CVG TRACON), and a stable autopilot-coupled approach, we were approaching our DA. Given a two-pilot crew, the pilot monitoring was able to focus attention on monitoring DA as well as acquiring the required visual contact for landing. Given the conditions, I anticipated being able to see the approach lighting system before the runway and included that information in the approach briefing. In the case of the Rwy 21L, the chart indicates a medium intensity lighting system (MALSR) with sequenced flashing lights – a big help in these low visibility conditions.

At the DA, I was able to see the approach lighting system. Are we allowed to continue?

Yes, 91.175(c) (Takeoff and landing under IFR) allows for flight below the published DA if the approach light system is visible, but only down to 100’ above the touchdown zone elevation unless the red terminating bars or red side row bars are “distinctly visible and identifiable” or the runway environment is in sight which includes:

  • The threshold.
  • The threshold markings.
  • The threshold lights.
  • The runway end identifier lights.
  • The visual glideslope indicator.
  • The touchdown zone or touchdown zone markings.
  • The touchdown zone lights.
  • The runway or runway markings.
  • The runway lights.

Within seconds of identifying the approach lights, the runway threshold came into view and we landed in calm winds; however, the advanced planning included having our missed approach altitude set and procedure committed to memory along with rehearsing the action items upon executing the missed which is universal:

  • Go-Around Power
  • Go-Around Pitch
  • Flaps (appropriate setting)
  • Positive rate/gear up
  • Navigate
  • Communicate

And we leave the hangar with the satisfaction of having completed a safe, disciplined flight with the entire system working together from meteorologists, to air traffic controllers to the other pilots in the system willing to share up-to-date vital information via pilot reports. It was a good day on the flight deck!

Eric Radtke
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