The Autopilot’s Aerial Tour Mode

The Autopilot’s Aerial Tour Mode

The Autopilot’s Aerial Tour Mode

Just yesterday (I am writing this in mid-February 2020), I had the great pleasure of flying a “Flightseeing” tour of northern Arizona in Ron McAlister’s lovely 1984 B200 King Air. I have done this numerous times over the years in a multitude of airplanes, giving out-of-state visitors an aerial tour of our beautiful state, and the scenic wonders it encompasses. The Mogollon Rim above the town of Payson, Meteor Crater southwest of Winslow, Monument Valley on the Navajo Indian Reservation, Lake Powell and its Rainbow Bridge, the city of Page with its Navajo Bridge and Glen Canyon Dam, the Dragon corridor through the Grand Canyon’s Special Flight Rules area, then a landing at Grand Canyon airport. We took a taxi-van into the park and had a delicious lunch in the historic dining room of the El Tovar lodge on the south rim of the canyon. The return flight back to Phoenix’s Deer Valley Airport (KDVT) included a tour of Sedona’s red rock majesty. Wow!

The weather was perfect, no TFRs existed and Ron, his wife Donna, and our passengers were exemplary guests. What a delightful, fun day!

What made it especially easy for me and comfortable for the passengers was my use of  the autopilot in modes that are very rarely utilized. In this particular King Air, the autopilot is the Sperry SPZ-4000, the digital version of the very popular SPZ-200A system. If you are flying one of these systems, a King KFC-300 or KFC-400, a Collins AP-105, 106 or 107, an APS-80 or some version of the APS-65, then most or all that I write here will apply to your system, too. If you have a Century IV or a King KFC-250, then, sorry, but these techniques will not work as well for you.

In days of yore – say, 50 or more years ago in the 1960s and early 1970s – it was rare to see a flight director (FD) and an autopilot (AP) combined into one unit … an integrated system. Instead, the autopilot – that almost all King Airs had – operated to control pitch, pitch trim, bank, and yaw via its four servos and its own control panel. The relatively few King Airs that also included a flight director – that could direct a pilot how much pitch and bank were needed to satisfy a particular flight condition by the movement of indicators displayed on the attitude indicator while hand-flying – had a separate control panel to program the desired parameters … heading hold, altitude hold, Nav tracking, glideslope tracking, etc.

Today it is exceedingly rare to find a King Air without an integrated AP/FD system. One control panel selects the modes for both systems. Unlike in the earlier, separate, non-integrated systems, we can never have the autopilot tracking a Nav course while the flight director is providing heading information. Weird? A poor choice of modes? Sure! But is it possible in the non-integrated systems? Yes.

Most of us will have the flight director in Go Around (GA) mode, Heading mode and, probably, the Altitude Select mode activated before takeoff and displayed on the Attitude Director Indicator (ADI). When the integrated AP is turned on in the climb after 400 feet above liftoff, it takes over control of pitch and roll to satisfy the FD commands. Very rarely, if ever, do we engage the AP without it immediately following the existing FD commands. But do you realize that it can work without following the FD? Yes, it can!

Try this little experiment on a clear, visual, day. Do not select any FD mode before takeoff. The ADI should be blank – no command bars showing. As you depart the pattern – say, with a 10-degree nose up and 20-degree left bank attitude – turn on the autopilot. In some systems, you will find that the airplane maintains the existing attitude perfectly, both bank and pitch. In others, the system may hold the pitch attitude but roll wings level. Try it and see what your system does.

How can we now change pitch and bank while still leaving the FD off? Two ways: First, use the pitch wheel or rocker switch on the AP controller to modify the pitch attitude and use the turn knob on the controller to modify the bank angle. Second, for almost all of you, hold the TCS (Touch Control Steering – the Sperry name) or CWS (Control Wheel Steering, the abbreviation for the King and Collins nomenclature) button and manually maneuver the airplane to the pitch and roll attitude that you desire, then release the button. Voila, look there! The AP starts holding the new attitude. It’s almost like having an invisible co-pilot that you direct, “Here, take the airplane and hold it for me, will you?”

As a side note, most of these systems will hold a bank angle between 30 and 60 degrees. But if 5 degrees or less is requested, the system rolls wings level, reads the heading from the HSI and holds that heading … even though the heading bug may be nowhere near that heading. That means that there is no rush to get the heading bug under the lubber line and select the FD’s HDG mode. Even with the rudder and ailerons not perfectly trimmed, the existing heading will be maintained perfectly.

Don’t misunderstand what I am writing: My use of the AP alone without being coupled to the FD is quite rare indeed! There may be only one flight in a typical year on which this occurs. For giving lower-altitude aerial tours, however, how fine it is! Let me explain.

I had used the normal AP/FD combination to climb, level off, track to our next waypoint – the Meteor Crater southwest of Winslow (the INW VOR) – and descend as we neared this site. I muted/disabled the TAWS (Terrain Awareness and Warning System) so that it would not be yelling at us incessantly as we flew near the ground. (If you don’t know how to do this in your airplane, please learn the procedure ASAP!) I leveled off about 1,000 feet AGL. We were now in HDG and ALT mode with the flight director bars in view, being followed by the AP. As we flew abeam the crater, I wanted to make a clockwise turn around it. Instead of moving the heading bug – and doing it again and again and again as the turn progressed – I merely reached down to the pedestal and rotated the turn knob clockwise out of its center detent. Doing this turned off the HDG mode automatically. With no lateral mode to follow, the FD command bars retracted out of view. Now we were in the “uncoupled” lateral mode of AP operation: The AP was still flying (and even holding our altitude in the vertical mode) but no longer following any FD bank commands. By regulating how far I rotated the turn knob on the pedestal, I could easily control bank angle and thereby the radius of the turn. Also, keep in mind that speed plays a role in turn radius so by setting power appropriately that was another tool I used to create a proper circle around the crater.

Monument Valley located on the Navajo Indian Reservation showcases sandstone pinnacles that reach 400 to 1,000 feet. (photo credit: Dee Willis)

When we had finished oohing and aahing our way around the crater, I then set the GPS for the town of Kayenta (07V) at the south end of Monument Valley and returned to NAV mode to track there. The engagement of NAV brought the FD bars back into view. I pitched up using the rotary pitch wheel on the AP controller, selected ALT SEL for the eventual level-off, and off we went for our next sightseeing. As before, we made a normal AP/FD-controlled descent to get near the surface, then started using the turn knob for our banking left and right around the spectacular monuments. Many John Wayne westerns were filmed here! Now, without FD coupling – which went away as soon as the turn knob was rotated out of its center detent – again the command bars disappeared. However, the ALT mode was still operative. I sometimes call this the “half-coupled” mode, since the AP was still adjusting pitch attitude for altitude control but allowing me – via the turn knob – to select the bank angle I desired. There were times I wanted to go a little lower or a little higher. Rotation of the pitch command wheel on the AP control panel turned off the ALT mode and left us in a completely uncoupled mode of AP operation.

Certainly, I could have done all of this with hand flying. I could have just tapped the electric trim switches on my control wheel – to disconnect the AP but leave the yaw damper on for ride comfort, my preferred method of AP disengagement – and started maneuvering using the pilot’s control wheel myself. Sometimes I do exactly that. Call me lazy or maybe just variety-seeking, but today I let the AP keep flying in this cool and rather unusual uncoupled mode. By the way, one of my pet peeves is a pilot who hand-flies while ignoring the FD commands – definitely a bad habit pattern to form. So, when I disconnect the AP to start flying by hand, I always remove the command bars from view. There’s more than one way to do this, but a simple one is to merely tap the mode button for the existing roll command, HDG, NAV or APPR.

What a fun time we had! The weather was clear and calm with very little low altitude turbulence. The Arizona scenery was awe-inspiring and the passengers were friendly and appreciative. The lunch in the more-than-a-century-old classic dining room was delicious and came with fabulous service. I thank God for letting me still enjoy experiences like this!

The next time you treat your passengers to a low altitude visual tour of your favorite area or one of our nation’s scenic wonders, give these AP modes a try. You’ll like them!

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