A Plan For Your Scan….
You’ll hear this constantly, that “the scan” is the most important part of instrument flying, “The secret to instrument flying is having a good scan”, and you need to “keep your scan going”. Well cool, but I hate it when you hear all these “important sayings”, yet no one ever tells you HOW to achieve the very important thing they are talking about, which in this case is “the scan”. We’ll make learning how to properly scan the instruments as simple as possible for you, because quite frankly this is a very important part of instrument flying, and also, you’re not going to have any brain power to allocate to complicated procedures when trying to scan your instruments (flying and interpreting the instruments will be using all of your brain power).
The Parts of the Scan
We’ll break the instrument scan into three parts:
- Cross Check
Now working backward here, you should be able to “control” the airplane at this point in your flying career (assuming you have a Private Pilot Certificate or higher now, you already know how to fly). Once you interpret the instruments, you can CONTROL the airplane. However before you can INTERPRET what the instruments are telling you about the aircraft’s attitude, you must CROSS CHECK.
So what do you really need to do here?
Well, congratulations. At this point in your flying career, you can most likely already handle steps 2 and 3 very easily. So all we really need you to learn here is step 1, how to CROSS CHECK the instruments.
The Cross Check
So When Do We Look at the Lonely Tachometer?
Let’s get one thing out of the way here: You don’t have to look at the “tach” much. You can HEAR the power from the engine. That will tell you about changes in RPM in a fixed pitch propeller airplane. The only time you really care about what your power setting (or making an adjustment to it) is when you detect something is “off” when scanning your regular “six pack” (or PFD). If you see speed is steady, but you are slowly descending at 100fpm when you want to be level, then add a small bump of power and quickly reference the TACH in your scan.
How the “SCAN” works
As you can tell from the two diagrams above, the ATTITUDE INDICATOR is really our best friend here, and what we will constantly be cross-checking all of the other instruments against. Whether it is a “6 pack” airplane, or Glass Cockpit, the attitude indicator is at the center of our focus. We’ll focus on talking about the instrument scan in a “6 Pack” airplane first.
Six Pack Scan
So by looking at the diagram above you can see the Scan starts at the ATTITUDE INDICATOR, and goes out to each instrument, then back to the AI, then to the next instrument, then back to the AI, and so on. We call this a “radial scan” since you’re going back and forth in that kinda sorta round-ish pattern. This is really the only scan I advocate for, with just slight modifications to it for different phases of flight. Using this technique of keeping your head still, and quickly darting your eyes around to each instrument (while always coming back to the AI) is great for phases of flight where you have to be extra precise (like takeoff into IMC or Approach through IMC). It is tiring however, so we do have modified versions you can use for less busy phases of flight.
Modified Six Pack Scan
Straight and Level Flight. In straight and level flight, we can cut back on our scan to save our eyes a little bit of movement and reduce fatigue that builds over time of forcing your eyes to dart around in this crazy way non-stop. The diagram below shows us how the instrument scan might look in a straight and level airplane in IMC.
Your center of focus is still the AI, however as you dart your eyes back and forth between instruments, you are no longer bringing your eyes back to the AI every single time. For example, your order of scanning might be:
In level flight you can drop the VSI as it is not going to tell you anything new that the altimeter, attitude indicator, and Airspeed are not already making obvious to you.
The idea here is that you can move your eyes a little slower, spend maybe a half second more on each instrument to give your eye muscles a break, and that you are still able to cross check each instrument against the AI. Notice that you might look at two instruments, but the AI always “touches” each instrument, or in other words, you can compare the AI to each instrument either before or after you look at it.
Here’s what your scan should look like in level flight:
Scanning in other Phases of Flight
Now many instrument courses and books will tell you about how there are 10+ different ways to scan depending on whether you’re in a constant airspeed climb, constant rate descent, flying in a level turn, and so on. For me, that’s way too many different types of scans to remember when I’m getting bounced around in the clouds, talking to ATC, and trying to fly the airplane too. So let me offer a simpler way to scan the instruments successfully.
Let’s say now you want to perfect your instrument scan for something like a constant airspeed climb. What instruments make absolutely no difference to us?
- Tachometer, VSI, Turn Coordinator, and Altimeter really mean nothing to us here right?
The power will be set to full when you are climbing, end of story. The rate of climb you get will be what you get, you are flying a constant airspeed climb, so you can’t vary the airspeed at all, and power is already full, whatever the VSI says is pretty irrelevant. Your information for bank during this climb will come from your DG first, and your AI second, the turn coordinator is just there for you to check if you suspect one of those other instruments has failed. The altimeter is pointless now too up until the point where you get close to the altitude you want to level off at, so why include it in your regular scan?
Here’s the point:
If you are flying the airplane in a particular phase of flight and wondering what instruments you should look at, only look at the ones that would make you change what you are doing based on what you see.
i.e. if you notice the VSI says 400fpm and you are trying to maintain a 90-knot climb, you wouldn’t change anything in terms of pitch or airspeed if you noticed the VSI suddenly read 500fpm, so why bother to look at it in the first place.
Now of course you may occasionally want to glance at other instruments to make sure things are working as they should, but don’t let yourself get consumed with it (sure check the TACH every so often to make sure RPM is where you expect it to be and you’re not picking up carb ice, but don’t stare at it or be glancing at it every 5 seconds, focus more on what counts in that moment).
Conclusion of the Six Pack
- Stick to the “basic everything scan” during busy phases of flight.
- Rest your eyes, slow your scan slightly, and drop out the unimportant instruments when you’re in not so busy phases of flight (like level in cruise).
- For all other phases of flight, look at the instruments that will affect your interpretation of how TO FLY the plane. If the information its giving you won’t change the way you’re flying, then skip it until later.
Yes, believe it or not your eyes have muscles, and just like you get sick of reading and studying ground school books and courses, your eyes will get tired and bored with vigorously scanning instruments. Due to this human factor limit, you will not catch me flying single pilot IFR without an autopilot in actual IMC conditions for any more than 15-20 minutes before I am sure to find my way back to VMC or land. An autopilot can certainly help reduce the workload and fatigue on you flying, but you still won’t find me flying in actual IMC even with an autopilot for more than an hour or so in General Aviation aircraft.
This “fatigue” factor holds true for your flight training too. There is absolutely no way you should be hand-flying an airplane single pilot in actual IMC for any length of time. Thus, there is no way you should be flying “under the hood” for 1.5 hours straight during your flight lesson training for IFR. Try to spend no more than 30 minutes of constant “hood time” before taking a 2-3 minute break and flying VFR (or better yet, make the CFII fly the airplane for 2-3 minutes while you grab a drink of water and have them talk to you, this way you can focus on what they are saying and how they are flying rather than having to use mental power to fly the airplane and try to learn at the same time).
Scanning the Glass
So for those of you lucky or unlucky enough to be training in a partial or full Glass Cockpit airplane let’s take a look at how your scan will look. Let’s take a look at a G1000 (the standard of all glass cockpit airplanes out there) and where you’ll be looking to find your “six pack” information on the computer screen!