Since the Asiana crash last month there has been a lot of talk about automation in the cockpit.
There's an old joke that the cockpit of the future will feature a single pilot and a large dog. The pilot's job will be to feed the dog. The dog's job will be to bite the pilot if he tries to mess with anything.
We're not there just yet, and I hope to make it to retirement before we get there.
I've flown many different aircraft over the years. Some, like the T-38, had no autopilot at all. Some, like the KC-135 and B-52 had fairly simplistic autopilots. The 727s I flew were a mixed bag depending on when they were built.
The Airbus 300 and 757 both have pretty sophisticated flight management and auto-flight systems. The big difference being that the plane was designed with the automation in mind, rather than having it "tacked on" as in earlier aircraft.
I don't have any experience with the newer Airbus (A320 and later) or Boeing (777 and later) offerings so I can't talk much about fly by wire. From what I've been told, the automation in the 777 is similar to the 757 but even more capable.
So let's take a look at some of these cool toys and see how they can make our lives easier - or more difficult.
The most basic of autopilots is called a "wing leveler" and it does just what it says and nothing else. These are sometimes found in general aviation. If they were ever used in airliners it would have been way back in the day.
I don't have much experience with general aviation autopilots. They range from the very basic to the very advanced. It just depends on how much money you've got.
From there we start to see more sophistication with the ability to control pitch, roll and sometimes yaw. At that point you've got something that will keep the plane pointed in a certain direction, but will still require some attention to maintain heading and/or altitude.
Add the ability to maintain an exact altitude and heading and we've arrived at early jet era technology. Let's take a look at one of these.
The autopilot is engaged by the two switches (#3) which engage the aileron and elevator servos. Yaw is controlled by the aircraft's yaw dampers, so the autopilot doesn't control the rudder at all.
The large knob (#2) moves up/down/left/right and controls pitch and roll. I always found it hard to make smooth pitch changes with this. It does have altitude hold, which is nice. Once you level off at an altitude, engage switch #4 and it will stay at that altitude.
We have a few lateral modes, controlled by switches #1 and #5. Heading select allows us to dial a heading into the control panel and the aircraft will turn to that heading. That's a pretty nice feature.
Finally, it's able to capture and fly an ILS glideslope. That feature worked pretty well. It couldn't land the plane, so you'd have to kick the autopilot off at minimums and take over manually.
Most autopilots can be disengaged by pressing a button on the yoke. There is usually some type of warning, both visual and audible that you've disconnected the autopilot.
In addition to the autopilot we have something called a "Flight Director". The Flight Director gives us steering commands fly a heading, hold an altitude, follow a course and even fly an ILS approach.
Take a look at this attitude indicator. In the center is an orange trapezoid, which represents the aircraft. The two yellow "fly bars" to either side of it are controlled by the Flight Director. The object is to keep the "aircraft" centered in the yellow needles.
The key to automation, and I can't stress this enough, is to always know what it's trying to do and always know what it's telling you.
To help us do that there is a display with two columns of lights, the left column tells us what the Flight Director is doing and the right column tells us what the autopilot is doing. Green means "engaged" or "captured" and yellow means "armed".
Altitude hold is showing green for both columns. We're in level flight and waiting to intercept the glideslope.
Glideslope is armed (yellow) but not yet captured. Once we capture the glideslope the GS lights will change from yellow to green and the ALT HOLD lights will extinguish.
OK, that's about all this particular autopilot can do. Let's look at something a little better. This is what our newer 727s had.
The lateral modes (VOR LOC, Heading Select) all work about the same. What's improved is the vertical functions. Instead of just holding a given pitch, it can maintain a vertical speed. By using knob #2 we can maintain, say a 1000 feet per minute climb or descent.
Another nice feature is what I call "pitch for speed". By switching knob #1 to IAS Hold, it will climb or descend to hold the current airspeed. Want to climb at your current speed? Select IAS Hold and push the power up. Want to descend? Select IAS Hold and pull the thrust back. Mach Hold does the same thing except it will hold the current mach number.
Even better, it has altitude capture. Let's say we're instructed to descend to 15,000 feet. We select IAS Hold, pull the thrust levers back, and dial 15,000 into the Altitude Alerter window.
Now I haven't mentioned auto-throttles yet, because we didn't have them on our 727s. Some of them did, at one time, but the company removed them to save on maintenance. So whatever we were doing with the autopilot still required using the thrust levers to control airspeed or rate of climb/descent depending on what mode the autopilot was in.
This was a pretty nice autopilot and I used it a lot more than I did the earlier version. Some of them even had auto-land capability. This was pretty good stuff for 1970s technology but it still had that "tacked on" feel to it. The autopilot and Flight Director still had to be controlled separately and the autopilot had limited ability to navigate. It could track a course, but that's about it.
Now let's take a look at something a bit more modern.
Since I'm currently on the 757, I'll use that for most of my examples.
The big difference with the newer airliners is that the automation is built in and fully integrated rather than feeling like an add-on.
The 757 has pretty much all the bells and whistles. It has a programmable FMS (Flight Management System) that we can load our entire flight plan into. It has 3 autopilots (redundancy is good) with auto-throttles and full Cat 3b auto-land. That means not only can it land itself, it can track the center of the runway after it lands. It works well - very well.
The heart of the system is the FMS. This is where we basically "program" the flight. The navigational database contains all the airports, departures, arrivals and enroute waypoints we might need. We can build the flight plan and have the autopilot follow it from shortly after takeoff until landing if need be.
Not only can it navigate laterally, called "LNAV", it can navigate vertically in "VNAV". We can tell it to fly certain altitudes at specific waypoints and it will do its best to comply. That's a big help when you're flying some of the LAX arrivals that have umpteen different altitude restrictions along the way.
Here's the main screen we use to program the FMS. In keeping with our tradition of alphabet-soup this is called the Multifunctional Control Display Unit or MCDU or "McDoo" or usually just "the box".
We'd be here a week if I tried to teach you everything this does. Who am I kidding? I probably don't even know everything it does. Each button brings up a different "page" of data. In this case we're looking at "Legs", meaning "Flight Plan". This is the route we want the aircraft to fly. We program this on the ground but we normally have to edit it in flight as directed by Air Traffic Control.
Note the area highlighted in yellow. That's telling us that we've programmed the box to cross the waypoint HAB (that's a VOR) at 290 knots at Flight Level 300. As long as we put the autopilot in the correct mode, it will try to cross that point in space at FL 300 and 290 knots airspeed.
We control the autopilots through a panel on the glareshield called the Mode Control Panel or MCP. The same panel also controls both pilot's flight directors. In fact, both the flight directors and the autopilot share the same data.
If the autopilot is engaged the pilot flying will normally control the MCP. This makes sense when you think about it. Changing something on the MCP will likely change the aircraft's flight path. Therefore the pilot "flying", even if they are just telling the autopilot what to do, should control the MCP.
If, however, the plane is being hand flown, the other pilot will control the MCP. This is to ensure that the pilot flying is being given good steering commands by the flight director. It's rare that we would ever turn off the flight director, so we want to make sure it's not leading us astray.
Let's take a look at the MCP.
1. Lateral navigation
2. Vertical navigation
For lateral navigation we have the choice of several modes:
1. Takeoff - Maintains runway heading. Used only at takeoff.
2. Heading Hold - Defaults to this right after takeoff. Holds whatever heading you had at rotation. Normally used only at takeoff.
3. Heading Select - Holds whatever heading is dialed into the Heading window. This is the most basic steering mode. This is normally what we use if we're being vectored by Air Traffic Control.
4. LNAV - This is the most advanced mode. The plane will fly whatever ground path is programmed into the FMS including holding patterns and GPS approaches.
5. LOC - Used for flying localizer approaches.
We have several vertical modes to choose from:
1. Altitude Hold - Does just what it says. Holds whatever altitude you're at.
2. Vertical Speed - Climbs or descends at a given rate. We use this mode with caution because it can get you into trouble if you don't watch it. For example, you can stall or overspeed the aircraft in this mode.
3. FLCH (Flight Level Change) or "Flich" - This is the "pitch for speed" mode we saw in the older autopilot except it's a little smarter. If we're trying to climb, it will set the thrust to climb power. If we're trying to go down it will use idle. It will hold whatever speed or mach number we dial into the airspeed window by changing pitch. It also has more flight envelope protections built into that than Vertical Speed.
4. VNAV - This is the most advanced mode. It will fly whatever vertical path is programmed into the FMS. It will attempt to meet all intermediate airspeed and altitude restrictions along the way. It's smart enough to slow below 250 knots when passing 10,000 feet. When everything is working the way it should VNAV is pretty slick. It even gives you a virtual "glideslope" to show how well it is following the "path".
5. G/S - Glideslope. Used to fly an ILS approach.
There are some other specialized modes that you would only see during takeoff, go around or an auto-land but I've probably thrown enough at you already.
The auto-throttles have several modes but they all work one of two ways:
1. Maintain a certain thrust setting. Either takeoff/go-around power, climb power or idle (to descend).
2. Maintain a certain indicated airspeed or mach number.
There are also times where the auto-throttles will "de-clutch" and allow manual control. For example, if descending in FLCH the auto-throttles will initially go to idle but will then de-clutch and go into "Thrust Hold" mode. This lets me control my descent rate in FLCH (pitch for speed) without having to go to Vertical Speed. When it's time to level off the throttles will re-engage to hold airspeed.
At any time I can disengage the auto-throttles by pushing a button on the throttle. We'll get a "bleep bleep bleep" and a message telling us that we've done this.
The other component to all this is called the FMA or Flight Mode Annunciator. This information is displayed right on top of my attitude indicator and tells me exactly what the plane is trying to do.
This is extremely important information. Regardless of what's dialed into the MCP or programmed into the FMS, the annunciator is telling me what's really going on. If the MCP is rumor the FMA is truth.
Since I'm not training you to be 757 pilots, I'll just give you a quick example of how this works.
1. CMD is displayed - the autopilot(s) are engaged.
2. A/T is displayed - the auto-throttles are engaged.
3. SPD - The auto-throttles are controlling our speed.
4. HDG SEL - We're in Heading Select mode. We're steering the plane with the Heading knob.
5. ALT HOLD - We're level at our selected altitude.
6. LOC - Localizer mode is armed (it's in white). When we intercept the localizer it will turn green and replace HDG SEL at the top.
7. G/S - Glideslope is armed. When we intercept the ILS glideslope it will turn green and replace ALT HOLD at the top.
Automation in my opinion is a two-edged sword. Used properly it can make your life a whole lot easier. It can reduce fatigue and it can free you up to look at the "big picture" rather than having to micro-manage your airspeed. It's almost scary how well some of these planes can fly an ILS approach.
It can also get you into a lot of trouble. You have to always keep in mind that it's just another computer. Garbage-in/Garbage-out still applies. It does what you tell it to do, not necessarily what you wanted it to do.
The automation can get "confused" if you start changing too many things too quickly. This is occasionally a problem with the 757 but it was a regular occurrence in the Airbus 300 with its Commodore 64 vintage processor. On more than one occasion I had the A300 "go stupid" on me when trying to program a route change.
Auto-throttles sometimes can get confused when the winds are gusting. This is because they only react, they don't anticipate like a human can. When flying an approach in gusty conditions it's sometimes better to switch them off.
This is my personal philosophy when it comes to autopilots. Your mileage may vary, but I think these are pretty good rules.
Treat the autopilot like another pilot.
I keep an eye on it just like I would if the other pilot was flying. I will try to know its strengths and weaknesses. I assume it will make mistakes just like the rest of us do.
I would never hand another pilot an untrimmed aircraft.
Before I switch on the autopilot I make sure the plane is stable and properly trimmed. That way I don't have to watch it flail.
Make sure the other pilot knows when I engage or disengage the autopilot or auto-throttles.
This is just good common sense crew resource management.
Try not to have both pilots heads-down at the same time.
If one pilot is programming the box, make sure someone else is looking out the window.
It's a very easy trap to fall into. The other person will say "Hey! Do you remember how to make this thing do __ ?" Next thing you know I'll have my head down there in the FMS trying to figure it out.
Not such a big deal at cruise altitude but potentially devastating in the low altitude environment.
Use the appropriate level of automation for the situation.
If we're going into LAX at a busy time of day, that's probably not the best time for me to practice my hand-flown, auto-throttle off, flight-director off approach skills. I'll likely cause the other pilot to get task-saturated trying to keep up with running the MCP, talking on the radio, looking for traffic plus watching me flail around the sky.
If we're the only plane departing Casper Wyoming on a nice day, then by all means I'm going to hand fly the departure to keep my skills sharp.
Know how the automation will react to certain situations.
This comes from keeping up with your systems knowledge and also from experience. The new guy says "Hey what's it doing?". The experienced guy says "There it goes again!".
Garbage In/Garbage Out
The FMS is only as good as the data you feed it. If I don't set it up properly it's not the box's fault if it can't keep up.
If the automation is getting confused or I'm getting confused, it's time to switch to a simpler mode.
If LNAV is taking me the wrong way I'll switch to HDG SEL. If VNAV is screwing up I'll go to FLCH or even Vertical Speed. Once we get things sorted out we can go back to the more advanced mode(s).
If it's still not doing what you want turn the thing off and hand fly.
The pilot is ultimately responsible for the plane going where it's supposed to go. Fly the plane, don't let the plane fly you. This is easier said than done and I find I have to remind myself of this on occasion.
I'm speaking from experience here. If there's a way to screw up the automation I've probably done it or at least tried to do it.
The automation is great as long as you know its limitations. Use it when you need it but don't be afraid to turn it off.
We still don't know exactly what happened with Asiana.
We'll know more when as the investigation progresses.
I'm speculating here, but I suspect the contributing factors were fatigue, training issues, communications issue, crew resource management and use of cockpit automation. These factors were probably aggravated by some of the airport navigational facilities being out of service. There's seldom one cause for an accident and I suspect that was the case here.
There's an email going around from someone who claims to have been a former UAL captain who also worked as a simulator instructor for Asiana. I can't confirm anything in the email or find a link to the original so I'm to going to post it here. If this guy is legit, what he says is pretty damning.
To the best of my knowledge a perfectly good aircraft. They had a localizer for lateral guidance and a PAPI for visual glideslope. There were three experienced pilots in the cockpit. If you can't fly a visual approach on a nice sunny day then something is very wrong.