Primary v. Supporting Method

What Matters Most…

So what matters most in life instrument flying?  Well, that kind of depends on what phase of flight you are in of course…

CFIIs love talking about Primary and Supporting instruments, and what instruments are “primary” for a certain maneuver (like a constant airspeed climb).  While you may find that when actually flying under IFR, your brain power will be better put to use on other tasks besides wondering which instrument is primary or supporting at that particular time.  Knowing what instruments are primary for certain phases of flight will help you with your initial instrument training in knowing where to look for starters, and this is also something you’ll need to know for the written exam.

We’ll go ahead and give you several scenarios here and explain what instruments would be primary and supporting.  However before we do that, we’ll go ahead and categorize our instruments into three groups and explain them to you.  The three groups are:

  • Pitch Instruments
  • Bank Instruments
  • Power Instruments

Primary and Supporting Instruments

Power Information Instruments are:

  • Airspeed
  • MP (if installed)
  • Tachometer

Pitch Information Instruments are:

  • Airspeed
  • AI
  • Altimeter
  • VSI

Bank Information Instruments are:

  • AI
  • Turn Coordinator
  • Directional Gyro

Let’s look at what instruments will be primary for what in different scenarios now!

Straight Constant Airspeed Climb

straight and level constant airspeed climb

  1. Use AI as primary for PITCH and DG as primary for BANK
  2. Establish Climb PITCH with AI, keep the wings level with DG primarily and AI supporting for BANK
  3. Once established, AIRSPEED is primary for PITCH, DG is primary for BANK
  4. At this point, supporting instruments are AI and VSI for PITCH, AI and Turn Coordinator for BANK
  5. When you want to level off, use KNOWN values: Set the nose to level with the horizon using the AI, set the POWER to cruise RPM and MP (if applicable), use the DG as primary for BANK
  6. Once flying level and airspeed stabilizes, TRIM to relieve control pressure, DO NOT trim to make pitch changes, set the pitch with the yoke or stick and hold it there, then TRIM to relieve the pressure you are applying.

Rolling in or Out of a Level Turn

  1. Primary for BANK and PITCH is AI
  2. Once established in a turn, primary for BANK is TC, primary for PITCH is Altimeter
  3. To establish a turn, roll to desired bank angle you think will get you close to “standard rate” and then use TC to adjust bank angle with AI supporting
  4. Typically at the speeds our airplanes fly a “standard rate turn” is around 14-17 degrees.  (REMEMBER, the higher your speed, the steeper bank you need to establish a standard rate (2 min) turn).

Constant Rate and Constant Speed Descent (like on an approach!)

  1. Establish a known pitch and power attitude (AI primary for PITCH, DG primary for BANK, POWER primary for descent rate)
  2. Once known values are set, VSI is primary for POWER, DG primary for BANK, Airspeed is primary for PITCH
  3. Typically you will be doing this on approach, when you are flying level, with the airplane fully configured before you start your descent.  The easiest way to fly an approach and begin a stable descent is to have the airplane flying at final approach speed with flaps out 2 miles before the FAF (final approach fix, we’ll talk more about this later).  If you are flying level at your desired airspeed and want to start a constant rate descent, all you have to do is reduce power, and not touch the yoke at all, the AI will show a slight decrease in PITCH, and the VSI will respond to POWER changes, with Airspeed staying pretty much right where it all was before as long as you are not messing with trim or pushing or pulling on the yoke/stick.

Power + Attitude = Performance

You’ll hear this saying throughout your instrument training, and it does have a lot of validity.  If you set full power, pitch the nose up to 3 degrees, you can expect a certain airspeed and climb rate from your airplane for given conditions (like weight, density altitude, etc.),  As you get to know your airplane more, this is especially helpful in being able to quickly recognize when something is not quite right.  If you set full power, pitch the nose to 3 degrees up and you are used to seeing a 500fpm climb, but suddenly you see VSI is at zero and Airspeed decreasing rather than holding the same old steady speed you’ve come to expect from your airplane in that attitude, then you immediately know something is wrong, and now you can use your scanning skills to tell you what exactly has failed, or if the airplane has picked up icing, or something else that is abnormal.

In aviation constants and doing the same thing over and over again and getting the same result is what keeps us safe.  When sticking to a standard way of doing things, (using the same inputs always) and you suddenly get a different result or output, then you’ll quickly be able to recognize something is wrong with the situation.

Wrap Up

So through those scenarios above you should start to see the logic here in what instruments matter most.  In reality, we will never spend exactly 0.5 seconds looking equally at each instrument, we will prioritize some over others sub-consciously, and that is totally okay (it’s part of being a PILOT and not a robot).  You decide what really matters to you!  The one thing that WILL always hold true, is your eyes MUST be constantly moving, and looking at any instrument for more than just a few seconds is a surefire way to get yourself into an undesired attitude as you miss the airplane wandering off course or airspeed decaying while focusing too much on some other instrument.  KEEP THOSE EYES MOVING!