Cirrus Perspective GFC700 AFCS
I recently had the opportunity to fly an SR22 equipped with a Garmin Perspective.
I have to say I really enjoy the capabilities of the GFC700 integrated automatic flight control system (AFCS). This is an AHRS based autopilot system that is very precise and quite intuitive in its functions. The Perspective AFCS incorporates a separate autopilot mode controller (Garmin Mode Controller, or GMC) complete with buttons for lateral navigation (HDG, NAV) and vertical navigation (ALT, VS, VNV). There is also an easily identifiable Blue Level Button, marked LVL, which, when pressed, will automatically bring the airplane to a straight and level attitude. This feature can be very useful if the pilot finds himself or herself in a dangerous unusual attitude.
In my 24 years of flying general aviation aircraft, I have not come across many planes equipped with a flight director. After flying with the Cirrus Perspective, I now see what I have been missing. During a recent Instrument Proficiency Check, I became focused on using the flight director during the takeoff and climb out. This produced a rather stabilized climb, and I was feeling proud of myself. My self-congratulation was humbled when the Perspective reminded me via annunciation that the takeoff flaps were still down. I had made the common mistake of giving the flight director far too much attention.
A flight director is only truly functional if the human pilot gives it the correct information to follow. The flight director may command the pilot how to fly the aircraft, but the pilot ultimately has to command the flight director to do what we want it to first. I found this out the hard way during a hastily-assigned ILS approach. I had requested an RNAV approach at my destination based on the winds, but my instructor threw me a curve ball, and although I had time to brief the approach and configure the airplane, I failed to change the desired altitude on the altitude preselect. So instead of being at 2900’ to intercept the glideslope, I remained at 4000’ because that was the last altitude I had selected. The flight director dutifully obeyed my last command, and I dutifully obeyed the flight director. Result: unstabilized approach, too high, too fast, behind the airplane. But a great learning experience.
I should mention that in the scenario above, the actual AFCS wasn’t engaged (the AP button wasn’t depressed). Like other autopilot systems, you can push the FD button and the command bars will tell you where to point the plane in order to fly the desired course, VS, etc. The GFC700 AFCS system is extremely accurate when you do press the AP button and let it fly the plane for you. It gives you, as the pilot, valuable time talk on the radio, brief approach plates, switch tanks, etc.
Let’s take a closer look at some of the functions of the GFC700 AFCS.
On a typical IFR flight this system is truly amazing. After receiving the first assigned altitude, place this in the altitude preselect box using the altitude knob. Program your flight plan and have that ready to go as well. Before takeoff, put the heading bug on the runway heading. After takeoff and at a safe altitude (put those flaps up!), make sure the HDG and FD buttons are pressed (the white lights above them will be on) and then engage the system by pressing the AP button. Select VS and use the Up/Down pitch wheel to select the desired VS (it’s better to go ahead and have this done beforehand). The plane will now fly that heading bug and will level off at the pre-selected altitude. Speaking of the altitude – when you select an altitude, ALTS will be in white in the AFCS Status Box, which shows the pilot what mode the autopilot is in currently (green indications), and what it will be in (white indications – armed). So ALTS will be white, meaning it is armed. If, during the climb, the pilot is given a higher altitude, simply use the altitude knob to select that altitude and the plane will keep climbing. But let’s say that ATC wants you to level off momentarily for traffic. All you need to do is press the ALT button and the plane will level off at that current altitude.
Integrated Airspeed Climbs
Another neat feature with the GFC700 is the ability for you to climb at a pre-selected indicated airspeed (IAS). During the climb with the system not engaged, press the IAS button and select the desired speed with the Up/Down pitch wheel. Each click equals 1 knot of IAS. This is especially useful in the turbo-normalized SR22 when you are climbing on a warm day while using Lean of Peak operation and you are trying to use a higher climb speed. In this case, the manual says to maintain at or above 130 knots IAS for cooling. When you engage the system, it will make the airplane climb precisely at 130 KIAS.
Now you’re at a comfortable, safe altitude, all the engine instruments are in the green, and ATC clears you on course. What I usually do is re-center my GPS course (highlight the desired waypoint on the flight plan and press Enter twice) and then press the NAV button. Now you are navigating via GPS to your waypoint or destination. If I hadn’t re-centered the needle, the plane would turn to intercept that GPS course.
Approaches with Ease
The system truly shines during an approach. On a typical ILS approach, the GFC700 will intercept a localizer and glideslope flawlessly. After receiving vectors at the appropriate altitude, and while you’re on that final vector to intercept the localizer in heading mode, press the APR button. The annunciator will show LOC and GS in white (armed), and then will switch to green (active) when they are intercepted. If you are flying an LPV approach, GP will be shown. The pilot should configure the aircraft properly for landing, monitor the progress of the approach and watch for any annunciations.
Go Around Command
Finally, in the event of a missed approach or even a go around, the system features a Take Off / Go Around button. It is located on the front side of the power lever. When the pilot presses this button on the ground, the flight director command bars go to Take-off mode; in the air, the system will go to Go Around mode. During the Go Around mode, any armed autopilot mode will be canceled except for ALTS. During my IPC I had a “deer” (simulated) run across the runway, and a go around was initiated. I pressed this button and was able to follow the flight director command bars to a safe altitude and re-enter the traffic pattern.
There are several ways to disengage the system. The most efficient way, and the one literally at the pilot’s fingertips, is to press the red disengage button on the sidestick. You can also push the AP button on the GMC, or, if all else fails, pull the circuit breaker associated with any of the AFCS servos.
I think the Perspective system in general, and the GFC700 AFCS in particular, are wonderful tools for today’s complex aircraft.
While not necessarily designed for the fair-weather pilot who likes staying “low and slow” in the local area, there’s no better system for the safety-minded instrument pilot who is traversing large distances for business or pleasure and values reliability.
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Contact: Grant Sutherlin