Airbus A320 & Boeing 737 NG Guide Advice


Sounds like you are getting older like me Chuck :wink: . My little X-Plane adventure in the DC3 has been very enjoyable despite a total lack of targets.


I did a quick summary for the 737 and A320 autopilot. Any advice to improve or clarifications?

I know it’s super-brief, but I figured that it would potentially help knowing what does what without explicitly listing pages and pages of procedures for each mode.

737 Autopilot

Autopilot Parameter Selectors

  • Course Selector: Sets course in COURSE display for related VHF NAV receiver.
  • IAS MACH Selector: Sets speed input to aircraft autopilot.
  • C/O: Change over airspeed unit (IAS (indicated airspeed) vs Mach), usually used above FL260, or 26000 ft
  • Heading Selector: Sets heading input to aircraft autopilot.
  • Altitude Selector: Sets altitude input to aircraft autopilot.
  • Vertical Speed Selector: Sets vertical speed input to aircraft autopilot.

Autopilot, Flight Director & Autothrottle Selectors

  • Auto-throttle (A/T) ARM Switch : Arms A/T for engagement. Auto-throttle engages automatically when LVL CHG, V/S, VNAV, ALT HOLD modes are used.
  • Flight Director (F/D) Switch: Arms flight director
  • CMD A/B: Engages autopilot in selected mode.
  • CWS A/B: Control Wheel Steering. Used as an “attitude hold” (CWS R = Roll Angle Maintained, CWS P = Pitch Angle Maintained)
  • DISENGAGE Bar: Disengages autopilot.

Autoflight – Thrust/Speed Modes

  • N1: Engages auto-throttle in N1 mode maintains thrust at N1 limit selected from FMC (or manually set via the N1 Set knob). Automatically engages in certain conditions.
  • SPD: Engages auto-throttle in SPEED mode (maintains IAS/MACH value in display).

Autoflight – Vertical Modes

  • VNAV: Vertical Navigation mode will follow the vertical components and restrictions of the flight plan entered in the FMC.
  • LVL CHG (Level Change): Aircraft climbs or descends to selected ALTITUDE at selected IAS/MACH
  • SPD INTV: Speed Intervention, aircraft limits its speed to selected IAS/MACH. Used while in VNAV mode. Used for speeds not set in FMC flight plan restrictions.
  • ALT HLD: Aircraft levels off and holds its current altitude.
  • V/S: Sets Vertical Speed to selected VERT SPEED.
  • ALT INTV: Altitude Intervention, aircraft will climb or descend to selected ALTITUDE. Used for altitudes not set in FMC flight plan restrictions.

Autoflight – Lateral Modes

  • LNAV: Lateral Navigation mode will follow the lateral components and restrictions of the flight plan entered in the FMC.
  • HDG SEL: Heading and Bank Angle selector. Aircraft will roll towards the selected HEADING.
  • VOR LOC: Tracks VHF Ominidirectional Range (VOR) localizer. Aircraft will only be controlled laterally.

Autoflight – Vertical + Lateral Mode

  • APP: Tracks localizer and glideslope during approach. Aircraft will be controlled laterally and vertically.

A320 Autopilot

Autopilot Parameter Selectors

Tip: When pulling a knob, it’s YOUR aircraft (selected input will drive autopilot). When pushing a knob, the FMGS takes over (managed aircraft flight plan will drive autopilot).

  • SPD MACH: Change over airspeed unit (IAS (indicated airspeed) vs Mach), usually used above FL260, or 26000 ft
  • METRIC ALT: Toggles altitude unit system (metric vs imperial)
  • SPEED Selector: When pulled, autopilot and auto-throttle will set the aircraft at the selected speed. When pushed, autopilot and auto-throttle will set the aircraft at the managed speed of the FMGS (flight plan).
  • HEADING Selector: When pulled, autopilot and auto-throttle will set the aircraft at the selected heading. When pushed, autopilot and auto-throttle will set the aircraft at the managed heading of the FMGS (flight plan).
  • ALTITUDE Selector: When pulled, autopilot and auto-throttle will set the aircraft at the selected altitude. When pushed, autopilot and auto-throttle will set the aircraft at the managed altitude of the FMGS (flight plan). Note that the autopilot will not go below waypoint altitude restrictions (in magenta on PFD altitude tape) in managed mode, while in selected mode it will ignore such restrictions (i.e. if you get clearance from an Air Traffic Controller).
  • VERTICAL SPEED Selector: When pulled, aircraft will follow vertical speed selected. When pushed, aircraft will level off.

Note: These speed, heading, altitude and vertical speed autopilot commands can be combined together. It is very important to know whether you set them in “managed” (the FMGS flight plan restrictions drive the autopilot) or “selected” (your selected value drives the autopilot) mode.

Autopilot, Flight Director & Autothrottle Selectors

  • Autothrottle (A/THR) ARM Switch : Arms A/T for engagement. Autothrottle engages automatically.
  • Flight Director (FD) Switch: Arms flight director
  • AP 1/2: Engages autopilot in selected mode.

Autoflight – Vertical Modes

  • EXPED: Engages EXPED mode to reach the altitude window with maximum vertical gradient.

Autoflight – Lateral Modes

  • LOC: Tracks VHF Ominidirectional Range (VOR) localizer. Aircraft will only be controlled laterally. Used in case the ILS system is unserviceable.
  • NOTE: LS is not an autopilot mode. Pressing this button displays ILS (Instrumented Landing System) information on the PFD.

Autoflight – Vertical + Lateral Mode

  • APPR: Tracks localizer and glideslope during approach. Aircraft will be controlled laterally and vertically.


“Bank angle! Bank angle!”


I know the feeling! It’s fantastic managing systems and seeing how they all interact, although I personally have a soft spot for proper engine management and realistic operating dials. I suppose that’s why I love the first and second gen of jets so much!



In this video at 12:47

Can someone explain to me what happened exactly? The guy created his descent profile in the FMC. However, he had a conflict message on the FMC “UNABLE 250 KTS AT D095L” and “DRAG REQUIRED”. He first armed his speedbrake, then decided not to… then he replaced the descent profile’s speed restriction (240 kts) at FL100 with the speed restriction of the conflicting waypoint’s speed restriction (250 kts) at FL078.

Does anybody know what the guy in the video did and why? I’m really mixed up…


Okay from what I saw. Airbus pilot so I don’t know the logic of the Boeing FMC

Speed restictions set on FMC

first) Waypoint D095L was 250
Second ) Waypoint BIG and Waypoint CI27L was set to 240

Even though he was Before WP (Wapypoint) D095L where the speed limit was coded as 250 you can see that on the PFD the aircraft was trying to peg 240 knots.

The pilot then Deploys speed brakes to remove energy from the aircraft and you can see on the PFD that the speed reduces to the target speed of 240 knots with about 1200 FT per minute rate of descent.

With speed brakes still deployed, he then corrects the error in the FMC allowing 250 knots unit WP CI27L. Now you see the speed bug on the PFD jump to 250 knots and the rate of descent increases to over 2000 fpm. Pilot then retracts the speed brakes and the rate of descent settles to about 1600 feet per minute.

So i can see from this the pilot allowed the automatics of the aircraft to increase speed in order to achieve a greater rate of decent.

He also has 2000ft set as final on the (airbus term) FCU and it looks like the predicted descent profile corresponds to WP CI27L. But this waypoint was coded at 3000. Maybe its using a managed profile to level at 3000 at WPCI27L then further to 2000 After this point. I am not sure how draggy the aircraft is but looks more than do-able.


Great description Bogus. I read what you wrote before viewing the video and had a very clear idea of what was happening. You see it every day…Boeing or Airbus (or just about any other modern jet)–doesn’t matter. The box makes big energy management mistakes and pilots often compound those mistakes by bad programming. One of my unspoken pet peeves is watching a pilot try to trick-fornicate the FMC by changing the descent speed in the middle of the descent. Sometimes it works but more often it just confuses airplane and passengers both.


It’s really the pilots fighting their own decisions they’ve made earlier that are now being followed by the FMC. Sounds like you could easily get lost in the computer and forget about flying the aircraft in that regard.

I kinda have it easy in maintenance in that regard, we don’t have to fight physics(well time…) so much :wink:


Interessting stuff.

We mil oriented pilots often take shortcuts when it comes to flight plans and following a flight plan. In the best case we fly over some waypoints on the map. No descent / climb profiles. No altitude or speed restrictions.

I’m looking forward to Chucks nicely condensed (well, I guess this one will be a bit longer than usual) guide.

Must be a PITA to retrieve the information from all the sources and watch hours of youtube (good, bad and ugly) videos.


I tell new F/Os that my two favorite sounds in the cockpit are “click click” and “click click”. Those are the sounds of a pilot disconnecting the autopilot and autothrust. When there is a bug in the human/plane interface, nothing solves it faster or more smoothly. But if that seems drastic 25 minutes from touchdown, V/S and LVL CHG are always there to bring us back to K.I.S.S.


First draft… thoughts?

Airbus A320

Boeing 737-800 NG


Resources: On my Mac’s “Preview” app the right column is garbage. (Between “Lewis Morrison…” and “…called FSUIPC” is OK
Part 1. You state that the plane “suffers” systems wise. I think that is unfair. The plane is simple. One could make the counter argument that this simplicity is more feature than bug.

Part 1. What your sources call the “System Annunciator Panel” is called by us the “Master Recall” (or commonly: “the six pack”). There is a distinction. The annunciators are mostly adjacent to their respective switches. There are several jobs that the Recall has: 1. To point out where to look for the problem and 2. to check for dual channal or secondary channel faults.

Part 1. Your tag pointing to VOR/LOC is labeled “Autopilot Level Change Switch”. (And to be precise, that is a pushbutton (PB), not a switch)

Part 1. What you label “Heading Indicator” on the ND is “Track” at most airlines. The little inverted triangle IS heading but the bigger block with the numbers “63” are likely what your readers will think you are pointing to. To see heading you either scan the arc below the ADI or put the heading bug on that little triangle. “Put the brick on the boat”. (You partially point this out later in the Climb section.)

Part 2. Excellent primer on flight planning!

Part 3. “27” points to the “Master Caution” not “Master Warning”.

Part 4. Holding the APU switch to “Start” for 2-3 seconds is not necessary. The signal to start is instant.

Part 4. “13”. This may be correct but I have not seen the Ignition used this way. We alternate between “IGN L” and “IGN R” durning each preflight so that the operation of the igniters are checked each day (if the engine doesn’t start, the selected igniter is INOP. We almost never switch to BOTH.

Part 4. “31”. Again maybe correct. Running ignition during taxi (unless Engine A/I is being used) is just wearing down the ignitors. Select “CONT” just prior to takeoff.

Part 4. “34”. Yaw Damp is selected on during the Captain’s preflight flow. You could wait until after start, but why? It is pretty important and harms nothing to turn it on in a low workload period like the initial preflight.

Part 4. The only lights that should be on before and after the start are the Nav and Beacon. When you are ready to move, switch on the Taxi light. If you turn on all of those lights after start you will get heaped with scorn and loathing by your fellow pilots.

Part 5. Inversely, keep all of those lights on until high altitude. The becon is REQUIRED to be on any time the plane is in movement.

Part 6. Hitting TOGA at 40% is a little early IMO. At that RPM there is still no guarantee that they will spool together. Best to advance a little further (say 70%) to avoid directional control issues.

Part 7. Yes the AP has two channels (aileron and elevator). And, yes, there are two autopilots (L and R) guided by two FMCs (L and R) but there is no way to put the two in conflict with each other. Whatever is done to one FMC is done to both so conflicts are not possible. The only time the 2 APs will even engauge simultaneously is at G/S intercept (although they can both ARM prior in APP mode) during a CAT 2 or CAT 3 approach with AUTOLAND. Then the G/S signals are separated electrically via the TR3 disconnect. The rest of the time, there is only one side controlling. Also, you describe the autopilot as an entity that makes performance decisions. It is more clear and more accurate to say that these values come from the FMC. The AP just does blindly does what it is told.

Every airline is different and I only know how mine does things. Where my knowledge conflicts with yours but others have told you differently then go with what you have been told–especially if the source is Boeing itself. Excellent stuff Chuck! Truly.


737 Part 2 Cockpit Layout (Pg 23): N1 speed usually refers to the fan, although the LPC/Booster unit is directly behind it in the CFM-56-7B/5B engine. Also I suppose the %RPM comment doesn’t make too much sense if people don’t know how engines communicate their current power setting to the user/pilot.

@smokinhole I do agree with chuck on the systems, especially when you look at different shorter lived generations of Boeing planes, their cockpits have a more coherent design and the 737 really stands out as a bit of a mishmash of design influences. And it certainly isn’t a simple cockpit to work, unfortunately.

The APU IRL is indeed a switch and go thing as smokinghole says. The APU is a tiny self-controlled gasturbine engine that can’t be controlled by the pilots short of turning it on or off. To keep it running you also need one of your fuel pumps on to keep the fuel lines pressured. the APU can’t draw in enough on it’s own, or at least that’s in our SOP.

I can’t really comment on most of the other things since I have no applicable experience with those. Looks like an excellent manual to me! A lot of what I said also comes down to someone’s opinion and not necessarily GE/Boeing’s factual ways/names of doing things.


I don’t disagree with the mishmash part but maybe take exception that this is a negative. For instance, I was once in Regina Canada in an A320 where it was so cold that one of the cargo doors froze open. The doors are hydraulically actuated. The 737 is just a simple hinge and otherwise human powered. Iv’e never had it freeze. The 737 is simple and old fashioned but it works every bit as well. It is as fast as the A320; a tiny bit faster even. It is a tad more efficient than the A320 (non-neo). And, at least for us, it is more reliable than the A320. I was a check airman on the 320 and cherish my (edit) 2000 hours in it. Both are great machines. Pilots suffer from a predjudice for whatever they fly currently. I am certainly guilty of that. And I also conceed that, unlike you Almighty, I haven’t a clue what’s under the hood. From a technical perspective the 737 may well be a basket case. I only know what’s on my side of the curtain.

The APU will start and run just fine without head pressure from a pump. But Boeing says turn in a pump so that’s what we do.


Part 8. In your description called “Securing Approach” you engage the 2nd autopilot for a possible handflown landing. If you plan a manual touchdown you DO NOT arm the 2nd autopilot. Two autopilots sets the airplane up for an autoland including trimming for the flare and go around. If you attempt a manual landing the plane will be very mistrimmed. In that configuration if there are any issues, you go around, not land. You also mention later to follow the flight directors for the landing. With a HUD, maybe. But in the 737 the flight directors are not designed to provide accurate guidance past DH. Once the runway is in sight, the 737 becomes a C-172.

Part 8. “Rollout” mode. If that is an option on some 737s, I was not aware. At UAL, all of our 737s are 2 channel autopilots, meaning aileron and elevator. The rudder is not part of the AP system. That’s why the 737 has slightly higher CAT III RVR requirements than airplanes with more sophisticated autoflight systems (basically everything currently flying that is not a 737). And, yes, this is where I will concede that it is inferior to other types. But in 20 years I have never had to go around from a CAT III so it’s not a huge deficiency–in the US at least.


Ah fair enough, perhaps it isn’t indeed. Can’t say I’ve ever functionally used in the air so I’ll defer to your experience in that!

It is, but then again almost every aircraft has basket case bits here and there that make you think “LSD was involved”. The 737 just had a chance to get 50 years of basket case design put on :wink: Which IMHO is a testament to how solid it is as an aircraft.

My comments should also be viewed as something from the MX perspective, I’ve never had the joy to fly these machines up in the sky and since in a sim we do everything from the operators perspective, so perhaps that is slightly more important for the manual!


Wow, thanks a lot for the rectifications, @smokinhole !

That one slipped through, it was mostly personal “post-its” I scattered throughout the guide, I forgot to remove that one.

I think I just phrased what I meant wrong. It wasn’t nearly as negative as I intended it to be. I simply meant that "Systems wise, the 737 has a lot of parts that were certified in the 1960/70’ and had no inherent reason to change over time. Hence this is why you will find a mix of technology throughout the aircraft. The aerospace industry has the saying “if it isn’t broken, don’t fix it”.


Oh I get it. And I know I sound defensive. I shouldn’t. I didn’t build it so what do I care? But your reader uses your guides because they are serious about learning a particular machine. They must like that machine. I know this because I am one of them. And I see a bit of genius in how Boeing has stretched the 737 line (both literally and chronologically). Another example is the light grey Electrical panel on the overhead. You will notice two unused curves cut into the grey plate. Those were there to accommodate the round ammeter and voltmeter gauges in the jets built 50 years ago. To update the plate without the niches would look better but cost x dollars. Boeing said, “screw it. nobody will care!”


And at risk of being a troll I have emitted a bunch of white noise over the most important message of this thread: Chuck has made two simple and highly useful guides that will be invaluable to thousands of virtual pilots as well as no small quantity of real ones. Thank you!


You’re too kind, @smokinhole. :slight_smile:

I was thinking of creating new forum topics for the actual individual guides… would that be ok? @BeachAV8R @EinsteinEP @fearlessfrog

Including it on the Mudspike tutorial section of the website could be a cool addition too.