When is a ceiling really sealing?

We have all been told old wives tales. Their problem is that they can take on a life of their own. Are the old wives right, is there a bit of truth to them, or are they just plain wrong? When it comes to ceilings as part of landing minimums the answer is a bit complicated. It begs the question, are ceilings sealing for Instrument Pilots or not?

Pilots setting out to get an instrument rating are attracted by the utility of flying in more varied (but not all) weather. The instrument rating promises flexibility and removes many obstacles to getting from point A to point B. However, once the training begins, prospective instrument pilots soon learn that to gain this flexibility they face even more restrictions and regulations than when they flew visual. Rather than the burden lightening, it seems to increase.

Instrument ground school consists of learning a myriad of regulations and restrictions. Students are taught the necessity of instrument checks (remember that VOR check lately?), the currency requirements of six approaches, tracking courses and holding, as well as well as proper and current charts. Additionally, there is complicated airspace (in this case the load becomes a bit lighter) as well as the all-important minimums found on each approach chart regarding visibility and ceiling. Wait a minute…ceiling?

When I trained for the Instrument Rating the word ceiling came up many times in the ground training. I learned to pay attention to the ceiling and visibility as presented in the preflight weather briefing as well as the approach chart. Over the past 21 years of flying in the clag I studiously studied the charts and made decisions about attempting my destination long before I launched on a trip or en route to the planned destination.

A few years back went through aircraft dispatch training a major (and in my opinion best) aircraft dispatch school in the country. It’s the Sheffield School of Aeronautics located down in Ft. Lauderdale FL. While the training was geared towards part 121 operations (airline) I carefully filed away inside my head how this training would benefit my part 91 flying.

After extensive coverage of weather and weather products, the instructor took the class through the AIM and approach plates. As we read the numbers for the minimums we were told to look at the visibility and to NOT assume that DH/MDH were also considered the ceiling requirements for the approach. This seemed to run against everything I had known over the previous years. Ceiling is not a requirement for flying in the U.S. under Part 121 (scheduled airline ops). Furthermore, this has been the case in part 121 flying since the 1960s. It’s only for filing an alternate airport that one must consider both ceiling and visibility. How could this be? Were all those instructors from the past wrong?

The story on ceilings begins back in the 1958 with the introduction of the turbojet in commercial operations. When turbo jets came into use the FAA set operating minima consisting of ceiling and visibility. This was due to the fact that there were limits in the equipment that measured ceiling and visibility. Furthermore the measurements sometimes were taken several miles away from the airport. After 1958, the minima began to change and were set at ceiling 300’ AGL and meteorological visibility of ¾ statute miles as weather technology began to improve. By 1961 the requirements were lowered so air carriers could use a ceiling of 200’ AGL and 3/4 statute miles. During this period navigation aids improved and a further reduction took place eliminating the ceiling concept completely in 1966. The final result was a DH of 200’ AGL and a visibility of 3/4 statute miles or RVR 4000’. The final ruling is spelled out in the 32 Federal Registry 13909 in October 1967.

Referencing the FAA Air Transportation Operations Inspector’s Handbook in FAA Order 8900.1. Volume 4 Chapter 2, it states: B.    Specifying the Operating Minimums. A major change in the method of specifying the operating minimums for approaches with vertical guidance evolved with the introduction of the DH and RVR concepts. These changes were finalized by the publication of U.S. TERPS criteria in 1966. This conceptual change eliminated the ceiling requirement by introducing a DH.   Likewise it states the same thing regarding MDHs on non-precision approaches in the following section. Also, 14 CFR Part 91.175(c) (2) states: No pilot may operate an aircraft…below the MDA or continue an approach below the authorized DA unless – The flight visibility is not less than the visibility prescribed in the standard instrument approach being used. No mention is made of ceiling. These are the minima specified for scheduled air carrier service as well as 14 CFR Part 91 operations as stated by the regulations. How does this play out?

Imagine you see the following TAF for your 1900z flight to KSGR

(Sugarland Texas):

TAF HOUSTON/SUGAR LA, TX

KSGR 161745Z 1618/1718 19012G22KT P6SM VCSH BKN 002

FM162000 17012KT P6SM SCT040
FM170700 16005KT P6SM SCT020
FM171400 16010KT P6SM VCSH SCT020
TEMPO 1714/1717 BKN022
FM171700 16012KT P6SM SCT035=

Compare this to the RNAV 17 approach at KSGR (below). The LPV minimums state a LPV DA of 398 MSL (400’ AGL). Is it legal to shoot this approach? Sure! Not only for you, but for that scheduled 737 10 miles behind you on the approach. There is no legal regulation stopping you from shooting the approach (and the airline can continue as long as the reported visibility remains good). One might say that the forecast ceiling won’t allow you to see the runway when you get to the DH, and then what if the TAF is confirmed by the METAR when you arrive?

RNAV - 17 Approach Plate

RNAV – 17 Approach Plate

What must be considered is that the ASOS ceilometer is at one fixed point on or near the airport. Since its measurements are directly vertical above the unit, the ceiling in the rest of the vicinity may well be above the 200’ showing on the METAR. The forecast ceiling is not controlling in the planning phase and the ASOS ceiling won’t be controlling on the actual approach. Like the famous aviation author Dick Collins would often say on his weather videos and in his books, “What you see is what you get”!

Let’s change the scenario for the airliner on approach behind you. Let’s say that the first line of the TAF read:

KSGR 161745Z 1618/1718 19012G22KT 1/2SM VCSH BKN 002

What would happen for the airliner? Based upon the TAF, and the visibility requirement on the RNAV approach of 1SM, he wouldn’t be able to begin the approach (for that matter he wouldn’t be able to be dispatched to that airport). However what if the airliner had P6SM in the TAF and then the METAR began to show a downward trend while he was en route? He would be able to continue the approach all the way to the FAF if the visibility remained above 1 SM but if it fell below prior to the FAF then he would have to break off the approach (if he were inside the FAF he would be allowed to continue). For us Part 91 people, we would be able to shoot the approach (regardless of the visibility). However, the result of a Missed Approach would probably be certain.

Since I bought into the myth of forecast and reported ceiling controlling flights, I often wonder how far this wives tale has spread. It didn’t take long for me to see.

Recently I was at the local FSDO getting a rating added to my certificate. In the course of conversation with the inspector I asked one of those ‘what about’ questions regarding ceiling requirements while he was completing my paperwork.. I told him that my understanding was there isn’t a ceiling requirement for Part 91 and Part 121 IFR ops. He informed me that there was a requirement for both ceiling and visibility. He said it’s in the regulations. He didn’t specify where it was located though. In the interest of getting out as soon as possible with my rating, I let the subject drop, fighting the urge to pursue the matter further.

Of course I’m not advocating blindly flying into impossible or dangerous situations. However, when it comes to dispatching flights (which we either do ourselves or someone does for us if we fly professionally) we need to legally look only at the visibility. The ceiling will definitely be of interest to us to gauge our chances of breaking out, but shouldn’t be the final rule if the flight is to take place. The filing of an alternate airport is of course another matter. The rules want us to have a definite way out if the destination becomes impractical. That is the reason “alternate filing” minimums require both the respective ceiling and visibility requirements of 600’-2 sm for precision approaches and 800’-2 sm for non-precision approaches.

You can’t always take everything you hear at face value. Sometimes the truth is a bit more elusive. Maybe the old wives weren’t quite so true this time! Perhaps ceilings have sealed us more than they should be!

Howard Drabek, ADX AGI IGI

 

 

 

 

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