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• Altitude mode (holding a con- stant altitude)
• Vertical speed mode (holding a con- stant rate of climb or descent)
• Airspeed mode (holding a con- stant indicated airspeed). G1000 systems call this Flight Level Change (FLC), but it is really a con- stant airspeed mode.
• Altitude preselect (holding vertical speed or airspeed mode until reach- ing a preselected altitude, and then automatically switching to Altitude mode to maintain that altitude)
• Approach mode (following a glides- lope or electronic glidepath)
Attitude and Altitude modes are easy. Hit the Altitude button when you’re at your desired altitude—it’s smoother if you manually level off and trim before engaging the autopi- lot. Or turn on the autopilot without hitting the Altitude button and it will hold your current pitch attitude. Most autopilots default to Attitude mode when engaged unless you select one of the other modes.
The possibility of mode confusion exists when you engage one of the oth- er vertical modes. You must make ad- ditional inputs to enter Vertical Speed, Airspeed (FLC), or Approach mode. If you’re delayed inputting all the vari- ables, or if you’re busy and make a mistake doing so, then the airplane may go off in an unexpected vertical direction when you hit the AP (autopi- lot) button. You’ll have another “what is it doing now?” moment.
Lateral autopilot modes include:
• Wings Level or Roll Control mode (maintaining wings-level f light but not a constant heading)
• Heading mode (maintaining the heading under the heading bug)
• Navigation mode (following input from a navigation source such asGPSoraVOR)
• Approach mode (navigation mode with much tighter tolerances for more accurate tracking dur- ing an approach)
• GPS Steering or GPS Roll Con- trol (navigation mode that adds turn anticipation and auto- matic sequencing, for example,
entering and f lying a holding pattern depicted by the GPS)
If you’ve not selected any other lateral mode, most autopilots will default to Wings Level (Roll) mode. Assuming your heading bug is set before you choose Heading mode, it will immediately hold that heading (or turn to it and hold, if the bug is not centered). Navigation and approach modes require additional program- ming of the navigational source, so there’s an added level of complexity and consequently a greater chance of mode confusion.
Simple to complex
Just as I introduce autopilot opera- tion to students, I’ve found it useful in my normal flying to engage the autopilot first in the simple modes. That gets the airplane going in the basic directions (vertically and lat- erally) I want, reducing my f lying workload. I’ll then add complexity. Here’s what I mean:
Autopilot engagement
1. Before engaging the autopilot, es- tablish the attitude and direction manually, and trim the aircraft.
2. If already trimmed in level f light, push the ALT (altitude hold) but- ton on the autopilot mode con- troller. The f light director (if equipped) will engage and indi- cate the level-f light attitude.
3. If in a climb or descent, don’t push any vertical mode buttons. The f light director command bars will match the current pitch attitude.
4. (Since I consistently use the head- ing bug even when hand-f lying the airplane and therefore it should be centered on my cur- rent heading), push the HDG (heading hold) button on the autopilot mode controller. The f light director command bars show a wings-level attitude on the current heading.
5. Then push the AP (autopilot) but- ton. The autopilot engages, hold- ing the horizontal and vertical modes already selected.
Confirm each mode as you select it, and that the airplane is on the
desired vertical and lateral guid- ance, before advancing to a higher state of complexity.
There’s very little chance of mode confusion engaging the autopilot this way. Oh, you might not have the head- ing bug centered and the airplane will turn steeply toward the bug (don’t laugh; I did this on my initial CFI checkride in a Cessna 182RG when the examiner asked me to demonstrate the old Navmatic my instructor had never let me use). But I’m a proponent of always setting the heading bug be- fore a turn even while hand-f lying, and even if you forget then following this engagement technique you’ll see that in the f light director command bars (if equipped) and catch it before you turn the autopilot on.
Now that the airplane is on the attitude and heading you want, you can add automation complex- ity if you wish:
1. Confirm the navigation source is programmed correctly and then hit NAV (navigation mode) or APP (approach mode) as required.
2. If your airplane is equipped with GPSS (“roll steering”), in all but the latest integrated systems the autopilot must be in the HDG (heading) mode for GPSS to work. Starting—and remaining—in the heading mode is precisely what you need to do to use GPSS in many installations, but it also introduces another mode confu- sion possibility if your GPS is not already programmed if your GPSS is on. Leave GPSS off, enter head- ing mode, check the navigation programming, and then turn on the remote GPSS switch.
3. Program the vertical mode: verti- cal speed, airspeed/FLC, and/ or altitude preselect. Then engage the desired vertical mode.
4. Confirm the selected modes are engaged and that the airplane is on the vertical and lateral guidance you want.
By design
This technique works at what is probably the highest workload time, a missed approach. In most
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