A fellow on the Internet who is over in the UK and is hoping to eventually start his training to be a pilot has written to me with some questions. Usually they are fairly specific, the replies are short, and I just shoot them back in an email. Even when they are things that can be answered with an Internet search (“How much fuel does your plane carry?”), but particularly when they are ones that are pretty hard to find out there (“What do you carry on a long trip?”).

He wrote recently to ask some questions about instrument flight. I thought back to when I was first training for my IFR ticket and the realization that some of the questions I had at the time would have been answered easily with a little history lesson. I’m going to ignore the fact that these questions come from across the pond. There are regulation variations from country to country (you can’t fly VFR at night in Mexico, you have to be on an instrument flight plan). I’m just to answer with what I remember from my training and my current flying. I’ll probably make some mistakes and perhaps my readers will chime in with some corrections in the comments.

What limitations does VFR and IFR set, and what are they?

All planes started out VFR. Visual Flight Regulations. You get in, start up the tiny engine, rumble down the strip of grass that was probably a farmer’s field last week, and head up into the sky. You go where you can see to go. 

Really early on there were few regulations because the violations of things that would become regulations just killed the pilots. When I was training the regulation was that you never head to a destination unless you had enough fuel to make it there plus thirty minutes extra. So early pilots probably flew in “violation” of that regulation regularly and I imagine a bunch wound up paying for it with their convenience (having to land for fuel), airplane (unable to find a good place to land, bent the airplane trying), or life. The instructors always say that all the regulations are “written in blood,” and I imagine that is essentially true, even if there isn’t a particular death for each regulation

By the time I was training the visual flight regulations were clear. You had to have three miles of visibility and clearance from clouds. How much clearance? Well, it depends on what sort of airspace you are in. “In general, when in Class E, D or C, you must remain 500 feet below, 2,000 feet laterally or 1,000 feet above any clouds.” This isn’t really of interest to me. I can’t measure from a point on my aircraft to the edge of a cloud. Five hundred feet above me is really close. When I am that close to the ground I have just taken off or I am about to land. I’ve never felt that close to a cloud when I was flying VFR. What I’m saying is, if you are not intending to fly through the clouds you probably would remain far enough from any clouds that you would be within regulations.

If you need to fly and the visibility or weather conditions are not legal for VFR then you need to fly under Instrument Flight Regulations. At that point, there aren’t really any limitations, just a lot of regulations and a lot of collected wisdom. There are, for instance, minimums for trying to land at an airport. They vary from airport to airport and can also depend on the runway you are approaching to land at, and which instrument technology you are using to land there. And ILS (Instrument Landing System) will usually get you within two hundred feet of the ground. A less precise system, using just a VOR (Very high frequency, Omni-directional Range) navigation transmitter might only get you within five or six hundred feet of the ground. 

Much more important than those limitations are your personal minimums. So when I first started making IFR flights I wouldn’t plan a flight to an airport that had a ceiling lower than a thousand feet. I was definitely not going to fly through any thunderstorms, or into any conditions that might create ice. And I stayed away from what I considered “hard IFR,” where I was doing very much of the cruise portion inside a cloud. I have, since those first years, changed my personal minimums. I’ve made an approach to minimums at an airport (and was unable to land, in one case). I have flown into icing conditions (once I had a plane that was capable of discouraging the accumulation of ice on the airframe). And I have spent over an hour and a half “inside the ping pong ball.” (I don’t like it.) When I was first flying on instruments I would not do a circling approach, but now, in very particular circumstances, I am comfortable enough to do so.

So the limitations for instrument flight should really be your own personal minimums, which will be more restrictive than the FAA regulations. (Unbelievably, the FAA believes it would be okay for me to take off even if the forward visibility was zero and the clouds were sitting on the runway. Such a zero-zero takeoff is permitted under IFR for Part 91 flights. I cannot imagine the conditions when I would think that was okay to do.)

My understanding is that a pilot is flying VFR if they don’t file an IFR plan and that all pilots are VFR only unless they are instrument rated.

That’s pretty much correct. Unless your plane is IFR equipped (there’s some instrumentation you need that is not required for VFR flight), and your pilot is instrument rated, you cannot file an instrument flight plan. If you are not on an instrument flight plan than you cannot fly in instrument meteorological conditions (IMC). If it is foggy at your airport and you can’t see three miles? You can’t take off. If there is a layer of clouds covering your destination airport and you flew VFR to get there, eventually flying over a layer of clouds, then you can’t land. You are going to have to divert to a different airport. One of our first flights as a family we were flying to Monterey and it was projected to be clear of clouds. It turned out to be fogged in just before we got there. We landed at our second alternate (Hollister) because our first alternate (Salinas) was also fogged in. After looking around for a hotel for the night (this is before iPhones and Lyft) we gave up and took off to head home. The controller asked if we were the plane that was trying to get to Monterey earlier and when we confirmed we were he said, “The fog just blew out to sea, if you want to go there instead.” So if you are VFR only it is a constant limitation.

If the cloud base is too low, you cant really fly VFR, which might make it a no fly day, without an instrument rating, right?

Yes, as discussed above, and this is what motivates a lot of pilots to get their instrument rating. That and anyone that wants to make money as a pilot. Most paid positions require an instrument rating. Certainly being an airline transport pilot (ATP) requires an instrument rating. A few weeks after you get your private pilot rating you will have a trip that is canceled because you cannot make the flight VFR. The utility of your certificate suddenly feels diminished by a bit of weather. The day after I got my certificate it was cloudy for the following six days. My instructor said that was always the way. He predicted that the week after I got my instrument rating it would be sunny the entire time. He was correct. I don’t know how the weather is arranged to do that for every student, but apparently it is how it happens.

If you have filed an IFR plan, do you have to stick to that plan? Are you allowed to fly around in circles enjoying the aircraft, after filing a flight plan, or do you need to stick to the heading ATC gave you when you filed a flight plan?

That’s the most important part of the instrument flight plan. It is that your aircraft is under positive control by air traffic control at all times, implicitly or explicitly. Pilots talk about being “in the system,” and you are really a moving part in a complex, well-designed, system for transportation. You are given a clearance before you take off. If you lose radio contact with the controllers along your route it is assumed that you will continue to fly your clearance until you land (or until the limit of your clearance, which is not always a landing point). There are all sorts of discussions about what you should or shouldn’t do in the event that you lose communications, but in my experience it just doesn’t happen, so I don’t worry a lot about that.


I couldn’t find a good reference for the history of the IFR system. I do know that the 1956 mid-air collision over the Grand Canyon had a huge effect on it and it lead to the current era where you cannot do anything other than fly the clearance you were given. In fact, if you leave the flight path it is called “a deviation” and can be the grounds for an enforcement action against the pilot.

When Charles Lindbergh flew airmail routes it was often at night. I cannot find information about what sort of instrumentation he had in his planes, although it seems unlikely that he had an artificial horizon, the key instrument for remaining nightside up while in the clouds. Accordingly, pilots who got lost in the clouds, disoriented, particularly at night, bailed out of their plane and deployed their parachute. If you did this you were then a member of the Caterpillar Club. Lindbergh was a member three times over before he made his flight across the Atlantic. 


Elrey Jeppesen was another airmail pilot. He loved flying and was determined to get better and better at the airmail routes. There was little information at the time, so he started compiling what he knew and the wisdom he gathered, in a little black book. It contained a lot of critical data, like how high the hills were around an airport. Other pilots eventually started asking him for copies of his little black book and today I fly with Jeppesen approach charts on my iPad. They are provided by Boeing, which bought up the Jeppesen company.

So the pieces of our current system came together over time, but as it existed when I started training, it was a complete, closed system for getting you from one airport to another, with strict control of your aircraft the entire time.

About Colin Summers

I am an architect, programmer, private pilot, husband and father. A couple of those I am good at.
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