While I don't pretend to be a human factors expert, I've both witnessed and been on the receiving end of automation surprise on several occasions. Most of the surprises I've seen in GA aircraft resulted from the pilot making mode errors - not fully understanding the consequences of their knob twisting and button pushing. Yet I have also seen deviations result from equipment failures and even from shortcomings in the design of an instrument procedure. There can be a seemingly endless number of ways for things to go wrong in a complex, automated environment and while we may want to never make any errors, mistakes are going to happen. I'll provide just a few examples of how things can get out of hand when technology is busy making the pilot's job easier and what you can do when the magic turns evil.
Operator Error
Here's a mistake I've witnessed many pilots make with the two-axis KAP-140. ATC instructs "... climb and maintain 7000." You decide it's time for George to do some flying. So you press and hold AP for 1.5 seconds, then press HDG, then select 7000 feet, then press ALT, and are subsequently confused as to why the KAP-140 won't allow you to use the UP button to select a vertical climb rate.
The key is understanding that the KAP-140 goes into VS (vertical speed) mode by default when your press the AP button. The mistake was pressing ALT, which engages altitude hold mode irrespective of the altitude you just dialed in - an odd design, to say the least! Pressing ALT a second time restores VS mode and allows you to enter a vertical climb rate. The problem is that the second time you press ALT to enter vertical speed mode, the altitude you selected is not armed. That means you'll climb, but the KAP-140 will not capture the selected altitude and if you're not paying attention, you'll bust your clearance. Blast!
Having your own SOP (Standard Operating Procedure) for autopilot use, combined with actually looking at the modes being displayed, can help circumvent this problem. A better knobology sequence would be: Dial in 7000 feet, pitch up for the desired climb rate, press and hold AP for 1.5 seconds, then press HDG, then press ARM. This results in the following KAP-140 display: HDG [AP] VS 7000 ALT Armed. The KAP-140 will climb at 500 feet per minute, fly the bugged heading, and level off at 7000 feet.
Unexpected Mode Changes
In an effort to make the pilot's job easier, Garmin's G1000 will automatically switch the navigation source from GPS to a localizer on an ILS, LOC or LDA approach. Interestingly, the G1000 won't automatically switch back to GPS for the missed approach procedure - you must manually switch the navigation source back to GPS. While this may sound like a good feature, it actually creates unintended consequences in aircraft equipped with a Bendix/King KAP-140 autopilot. Here's the setup.
You're flying the Concord LDA RWY 19R approach, approaching from the South, you've requested pilot navigation, Travis Approach has approved, and you're cleared to "cross KANAN at or above 4000' cleared LDA 19 right approach." You've selected and activated the approach on the G1000 with KANAN as the IAF. Your KAP-140 autopilot is engaged in NAV and ALT modes and it is flawlessly tracking a direct course to KANAN.
Crossing KANAN, the GPS sequences to fly the procedure turn and the KAP-140 continues to do a great job. You select 2500 feet, press ALT to enter VS mode, press DN a few times to command a 400'/min descent, and remove some power to keep the airspeed under control. The GPS and the KAP-140 turn the airplane to the outbound procedure turn, then after a minute, they turn the airplane inbound to intercept the approach course.
Reaching 2500 feet, you restore some power and the G1000 then automatically switches the navigation source to the localizer. If you're not observant, you will miss this mode change. The HSI needle changes color from magenta (for GPS) to green (for the localizer) and the switch in navigation source causes the KAP-140 to silently enter ROL mode. That's right, there's no aural alarm to alert you that this mode change has happened, just ROL flashing on the KAP-140 display - which is out of your primary field of view. If you don't realize the KAP-140 is in ROL mode, the airplane will fly right through the localizer. Ooops!
One SOP you could use to prevent this is to always change the KAP-140 to HDG, manually change the navigation source to the localizer, and follow the GPS prompts to manually command the procedure turn using the heading bug. Once you've turned inbound to intercept the localizer, press NAV and the KAP-140 will capture the localizer course.
Missing the Missed Approach
The Garmin G1000, as well as the 430/530 GPS receivers, can help you fly the missed approach using GPS navigation as long as everything goes as planned. For an ILS approach, the GPS must handle two possible cases: The full ILS and a localizer-only approach. The GPS considers the MAP to be at the runway threshold, even though the MAP on an ILS is technically at decision height, on glide slope, and on the localizer course.
One SOP you could use to prevent this is to always change the KAP-140 to HDG, manually change the navigation source to the localizer, and follow the GPS prompts to manually command the procedure turn using the heading bug. Once you've turned inbound to intercept the localizer, press NAV and the KAP-140 will capture the localizer course.
Missing the Missed Approach
The Garmin G1000, as well as the 430/530 GPS receivers, can help you fly the missed approach using GPS navigation as long as everything goes as planned. For an ILS approach, the GPS must handle two possible cases: The full ILS and a localizer-only approach. The GPS considers the MAP to be at the runway threshold, even though the MAP on an ILS is technically at decision height, on glide slope, and on the localizer course.
For these GPS receivers to suspend waypoint sequencing, you need to fly over the MAP at the runway threshold. Only then can you press the OBS key (or softkey) to re-enable waypoint sequencing, switch the navigation source back to GPS, and fly the missed approach using the GPS. If you don't fly over the MAP, waypoint sequencing won't be suspended and you'll need to do some more work to activate the missed approach. If you don't understand this GPS behavior, you could find yourself very confused at a high workload moment. Do'h!
Procedure Problems
Though rare, automation surprise may occur due to the way an instrument procedure was designed. This is exactly what happened to a pilot I was flying with recently on an approach I had flown many, many times before. The thing is, it had been quite a while since I flew this approach and the procedure had changed. Here's what happened.
The pilot requested the Sacramento Executive ILS RWY 2 practice approach with the published missed approach. Approach responded "... cross COUPS at or above 3000, cleared ILS 2 practice approach." The pilot selected the approach and activated it with COUPS as the initial approach fix. The autopilot was engaged in NAV mode and flew us to COUPS. What happened next was both dramatic and unexpected.
I'd like to be able to tell you that the average pilot can fly a G1000-equipped aircraft once a month and maintain instrument proficiency. Sadly, this is usually not the case. Unless you are practicing regularly with a G1000 PC Trainer or other simulator, you'll get rusty - fast! Part of this erosion of skill is due to the vast number of features the G1000 offers, but much of the problem lies in the user interface's annoying design that requires you to recognize subtle changes in operational modes. I don't want to mince words here: The G1000 and other GA GPS receivers are not easy to use. They require regular use and practice for pilots to maintain proficiency.
Procedure Problems
Though rare, automation surprise may occur due to the way an instrument procedure was designed. This is exactly what happened to a pilot I was flying with recently on an approach I had flown many, many times before. The thing is, it had been quite a while since I flew this approach and the procedure had changed. Here's what happened.
The pilot requested the Sacramento Executive ILS RWY 2 practice approach with the published missed approach. Approach responded "... cross COUPS at or above 3000, cleared ILS 2 practice approach." The pilot selected the approach and activated it with COUPS as the initial approach fix. The autopilot was engaged in NAV mode and flew us to COUPS. What happened next was both dramatic and unexpected.
Reaching COUPS, the GPS commanded a 41 degree heading change to the left from a 015 track to a 334 track to navigate to the newly added Computer Navigation Fix (CNF) UBIYI: A 41 degree heading change for a leg that is only 0.2 miles long! The groundspeed was only 110 knots, but there was no time for GPS turn anticipation to smooth this out. As soon as the GPS commanded a turn to the left, it commanded a turn back to the right as the airplane blew through the approach course. It happened so fast that we both wondered what was wrong. Was this a GPS error or an autopilot error?
No sooner had we begun to doubt the automation, the plane was headed back to intercept the localizer. You have to look really closely at the chart to see that the GPS and the KAP-140 were just trying to fly the approach as it is coded. I emailed the FAA to suggest they take another look at the unintended consequences of the change that was made. Good idea!
Ounce of Prevention
The primary ways a pilot can prevent automation surprise are both simple and straightforward:
Ounce of Prevention
The primary ways a pilot can prevent automation surprise are both simple and straightforward:
- Know your own limits with regard to currency/proficiency
- Know thy aircraft's equipment
- Monitor what the automated systems are doing
- Stay ahead of (or at least be in synch with) ATC's game plan
- Maintain situational awareness
- Develop and use SOPs (standard operating procedures)
- And be prepared to catch and correct errors.
I'd like to be able to tell you that the average pilot can fly a G1000-equipped aircraft once a month and maintain instrument proficiency. Sadly, this is usually not the case. Unless you are practicing regularly with a G1000 PC Trainer or other simulator, you'll get rusty - fast! Part of this erosion of skill is due to the vast number of features the G1000 offers, but much of the problem lies in the user interface's annoying design that requires you to recognize subtle changes in operational modes. I don't want to mince words here: The G1000 and other GA GPS receivers are not easy to use. They require regular use and practice for pilots to maintain proficiency.
PC-based simulators can be an effective and inexpensive way to maintain your instrument chops, but you need to have a plan. Sitting down and just screwing around is not going to serve you well. As they say in the music world: "If you play when you practice, you'll practice when you play."
A suggestion I've made before is to treat your autopilot and GPS like you would a low-time private pilot. It's okay to trust the systems, but monitor them to ensure they are doing what you intended. This is particularly important during transitions to climbs, descents, level-offs, turns to a heading, and intercepting and tracking a navigational course. So periodically interrupt whatever you were doing to ensure George is still flying the plane the way you intended. Did it capture the altitude you programmed? Has it intercepted the navigational course you intended? Is the autopilot still operating in the mode(s) you intended? If not, promptly drop what you are doing, intervene, fly the plane, and then try to determine why or George will trim you into a stall, flying you into the ground, or take you off course.
A suggestion I've made before is to treat your autopilot and GPS like you would a low-time private pilot. It's okay to trust the systems, but monitor them to ensure they are doing what you intended. This is particularly important during transitions to climbs, descents, level-offs, turns to a heading, and intercepting and tracking a navigational course. So periodically interrupt whatever you were doing to ensure George is still flying the plane the way you intended. Did it capture the altitude you programmed? Has it intercepted the navigational course you intended? Is the autopilot still operating in the mode(s) you intended? If not, promptly drop what you are doing, intervene, fly the plane, and then try to determine why or George will trim you into a stall, flying you into the ground, or take you off course.
Remember that you are the last line of defense when automation goes bad. Never, ever forget that fact.
