Is a Ceiling Sealing?

Instrument approaches list visibility and ceiling minimums needed for the approach. What do you really need in order to start the approach and to land?


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?

What Were You Taught?
Pilots setting out to get an instrument rating are attracted by the utility of flying in a wider variety of weather. Hopefully, by the time they visit the examiner, their instructor has disabused them of the notion of flying in all weather. The instrument rating promises flexibility and removes many obstacles that get in our way between point A and 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 visually. Rather than the burden decreasing, it seems to increase.

Instrument ground school consists of learning a myriad of regulations and restrictions. Students are taught the necessity of instrument checks (Done that VOR check lately?), the currency requirements of six approaches, tracking courses and holding, plus the need for 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?

Uhhh, 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 reviewed the charts and made decisions about attempting my destination long before I launched on a trip to the planned destination.

A few years back I went through aircraft dispatch training at the Sheffield School of Aeronautics located in Ft. Lauderdale, Florida. It’s a major aircraft dispatch school and my experience suggested that it is one of the best of its kind. While the training was geared towards Part 121 operations (airline) I carefully filed away 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 ignore the ceiling requirements for the approach. This seemed to run against everything I thought I knew. Ceiling is simply not controlling and isn’t even a consideration for flying in the U.S. under Part 121. Furthermore, this has been the case in Part 121 flying since the 1960s. It’s only meaningful when determining a suitable alternate airport in that one must consider both ceiling and visibility. How could this be? Were all those instructors from the past wrong?

History Lesson
The story on ceilings begins back in 1958 with the introduction of the turbojet into commercial operations. When turbojets came into use the FAA set operating minimums of ceiling and visibility. This was primarily due to the limitations in the equipment that measured ceiling and visibility at that time.

Furthermore the measurements sometimes were taken several miles away from the airport. After 1958, the minimums began to change and were set at ceiling of 300 feet AGL and meteorological visibility of 3/4 statute miles as weather technology began to improve. By 1961 the requirements were lowered so air carriers could use a ceiling of 200 feet AGL and the same 3/4 statute-mile visibility.

During this period the technology of navigation aids improved enabling greater precision and a further reduction took place eliminating the ceiling concept completely in 1966. The final result was a DH of 200 feet AGL and a visibility of 3/4 statute miles or RVR 4000 feet. The final ruling is spelled out in the Federal Register in October 1967.

The Regulations
FAA Order 8900.1 Volume 4, Chapter 2, Section 1 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 the ceiling. These are the minimums 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 TAF depicted above for your 1900z flight to KSGR (Sugarland Texas).

Compare this to the RNAV 17 approach at KSGR. The minimums section shows an LPV DA of 398 feet MSL (316 feet AGL). Is it legal to shoot this approach? Yes, it is. Not only is it legal for you, but for that Part 121 aircraft 10 miles behind you on the approach. There is no legal regulation stopping you from shooting the approach (and the airliner can continue as long as the reported visibility remains above minimums).

One might say that the forecast ceiling won’t allow you to see the runway when you get to the DA. Indeed it might not. Or, you might be concerned about the requirements if the ceiling is confirmed by the METAR when you arrive. Of course, this is also possible. But, the bottom line is that ceiling is simply not controlling and neither of these hypotheticals matter.

What must be considered is that the ASOS ceilingometer 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 feet 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 aviation author Dick Collins would often say on his weather videos and in his books, “What you see is what you get.”

Airline Operations
Airline operations are held to a tighter standard. While an aircraft operating under Part 91 can attempt any approach in any conditions, Part 121 operations must have the controlling visibility to begin an approach. They still don’t need the ceiling, as discussed, but the visibility is controlling even to launch for the destination.

So, let’s change the scenario just a bit for the airliner on approach behind you. Say that the first line of the TAF is now as depicted to the top-right. 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. In fact, He couldn’t even 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 enroute? He would be able to launch and begin the approach all the way up to the FAF if the visibility remained above 1 SM. But if the visibility fell below minimums before he got to the FAF—and he knew it—then he would have to break off the approach. (If he were inside the FAF when he discovers the visibility dropped, he is allowed to continue.)

There’s a subtle trap lurking in this capability for Part 91 flights. Since there is no legal restriction about planning or even flying an approach with visibility well below minimums, it’s tempting to try and complete the approach, possibly sneaking “just a bit lower to take a look.” There’s no relaxing the requirements of what you must see from 91.175. Visibility is controlling for an actual landing for all operators.

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.

Meanwhile, Back at the FSDO
Recently I was at the local FSDO getting a rating added to my certificate.

While talking with the inspector I turned the discussion to 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.

Alternate requirements and alternate selection are, of course, another matter. The rules want us to have a definite way out if the destination becomes impractical. That’s the reason for both the visibility and ceiling requirements of 600-2 for a precision approach and 800-2 for non-precision.

You can’t always take everything you hear at face value, even at the FSDO. Sometimes the truth is a bit more elusive. Maybe the old wives got it wrong this time. Perhaps ceilings have sealed us more than we should let them.

Howard Drabek, a Catholic priest in League City, Texas, holds commercial, instrument and multi-engine certificates and is a dispatcher and advanced ground instructor.


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