Course/heading?

[flapsforty]

Was sitting looking at this (http://www.nls0009.com/737cockpit.jpg) today and wondering...
That heading button, 3rd from the left, top, is what you chaps/ladies fiddle with every time ATC tells you to. (and also some times you fiddle a few degrees on your own initiatives)
Now I think this tells the AP what heading to put the aircraft on. OK so far.
But looking on the left, there is a button called "course". It also has a little window above it, and a yellow cross on the button itself. Course and heading sound like yhe same thing to me, but obviously aren't.
Anyone out there kind enough to explain?

Was gonna ask the lads in the cockpit today but we got talking about the reasons some women don't want kids and why most short haul pilots like to work part time so I never did get 'round to those buttons :)

[Genghis the Engineer]

Course = track, that is the direction over the ground being followed.

We take track, wind, and TAS, plug it into the magic flight computer (also known variously as circular sliderule, whizz-wheel, Dalton computer, or just plain guess) and come up with the direction in which we have to point the aeroplane. That is called true heading.

Then we adjust for magnetic variation (typically about 3½°W in England) which is the difference between magnetic and true North. The result is magnetic heading, and is where we point the nose of the aeroplane.

So, for things like quadrantal rule (which defines what height we fly what heading), we apply true track (course), but we fly the aircraft in magnetic heading. Even flying a fastish light aircraft around the UK, 15° difference between the two is fairly normal; for slower aircraft, the considerably greater windspeeds at altitude (even in an airliner), or other parts of the world it can be rather larger.


Having said all that, I'm a little aeroplane man; if the terminology is subtly difference for airliner flying, I apologise and no-doubt somebody will put me right.

G

[timmcat]

Are ones knees always at that peculier angle on the FD?

[chuck yeager]

HEADING is the direction the aeroplane is pointing.

TRACK is the direction the aeroplane is going (after it gets blown around a bit by the wind).

COURSE is the desired track to or from a VOR or ILS radio navigation aid.



Press the HDG SEL button and the aeroplane will point in the direction selected in the HEADING window.

Press the VOR LOC button and the aeroplane will intercept and follow a VOR or ILS localiser signal along the COURSE selected in the COURSE window.

[Notso Fantastic]

Genghis, nobody on the aeroplane cares what variation is in the air. Chuck Yeager's explanation is bang on. Course is simply the magnetic track to or from a Navigation point. That picture is of a 737. Each pilot can select the VOR Course of the VOR radio on his side, and if he wants, couple the aeroplane to fly on it. The aeroplane will then lock onto the beam bar and fly that Course over the ground, adjusting the Heading as needed to allow for the wind effect. As the wind changes, the Heading will change to allow a constant Course to be flown, the aim being the aeroplane should fly a constant Course over the ground, going direct from A to B.

[Genghis the Engineer]

Thanks for that NsF.

As you can probably guess, I've never dealt with anything fitted with an FMS, and very rarely with an autopilot (and then only at the design level, not operating).

This arguably may be a bad thing, but I remember gloating quite loudly as we approached 1/1/00 that I was one engineer who didn't care about the millenium bug beyond my office PC ;)

Probably a bit like asking an airline pilot to make a non-radio overhead join using the signal square. You know it's possible, you know it's there, but never troubled to understand it.

G

Happy being a little aeroplane man.

[flapsforty]

Note to self: All you have to do is ask.

Thank you for explaining gentlemen.

Begging your indulgence...................... :)

Heading; using that to point the AC in the right direction. Is it coupled to the AP? :confused: Does that mean that you can pick different levels of "automation"?? Like if you use the course button, it will adjust the heading accordingly but if you don't use "course" you set the heading yourself? And when the AP gets disconnected and after it has finished hollering and the pilot is flying by hand, do you actually point the AC at the runway yourself, or do you still use the heading select?
And what about those lnav and vnav buttons? Lateral and vertical navigation I think, but where do they come into the picture?

Another one; that wheel next to the speed brake lever. It starts turning furiously for no apparent reason (I always wonder if pilots ever get their fingers hurt by it......ok so I'm a simple soul) Something to do with "trim or pitch" and keeping the Ac at the rigth angle in the air I think. But why does it do that really?

Commuting to work usually on the 737 jump seat, I spend large amounts of time looking at pilots doing stuff I do not understand. You look at the same sequence of events over and over again, you feel like you should understand something, but really I don't have the first clue. So I have a million questions (won't post them all) and you chaps are being very kind.

[ETOPS]

flapsforty

Ref your question about the wheel next to the speedbrake lever. That's the trim wheel. Used to alter the incidence of the horizontal part of the tail - stabiliser in Amerispeak. You can move it by hand for fine adjustments or make it spin really fast using a switch on the control yoke. As an ex-737 driver I still have a dent in my right knee where regular severe contact was made with the whizzing wheel.

Ps Love the way you always post in colour...........

[Genghis the Engineer]

I shall duck out of further heading .v. course discussion before I get a nosebleed, let alone INav - I know how it works, but not the foggiest about how you operate it. However:-


Trim

Trim is the term for the "left well alone" condition at which the aeroplane flies. This defines a speed, bank angle and rate of climb or descent (being zero in a level cruise). As conditions change, the aircraft tries to climb / descend / turn / go faster / go slower. The biggest player in this context is "pitch".

Pitch is about how nose-up or nose-down the aeroplane is. But also ties to speed (more nose-down, goes faster / more nose-up, goes slower).

Changes to power, or any planned change in speed require a change in pitch trim to keep the aircraft on the desired flight path. That is what that wheel is for.

If flying entirely manually, the crew will turn the wheel to make adjustments. If the autopilot is doing the work (may as well let it, it's paid less than the FO so it keeps the costs down) then it will do exactly the same.

Depending upon aeroplane (I don't know which on the 737) the wheel may variously be altering the angle of the whole tailplane, adjusting springs in the elevator (main pitch control, the moveable bit in the horizontal tailplane), or moving a tab attached to the back of the elevator.


So, let's say that the aircraft is doing 250 knots and needs to slow to 180 whilst maintaining level flight. The (auto)pilot will retard the throttles to the power setting that is associated with level flight at that speed/weight whilst pulling back on the yoke to keep the aircraft level. Then he/she/it will rotate the pitch trim wheel backwards until there is no more need to hold a force on the yoke. Possibly some smaller adjustments might be made as well on the rudder and aileron trims to keep it from trying to turn (but probably not on a 737, that tends to be a characteristic of things with propellers). Then the aircraft is said to be "trimmed" in that it will fly at the desired height / speed / rate of climb/descent "hands-off".

It's never, mind you, quite right first time and a few tweaks get made then to make it spot on.

G

[OzExpat]

Go on Flappy, ask all the other questions that you've got stored up, we don't mind at all. :ok: You obviously don't get the opportunity when yer jump-seating. At the end of it all, you'll be able to tell the pilots what to do! :E

[chuck yeager]

Flaps – I hope you’re on my jumpseat the day both pilots succumb to the crew food...



On a 737-300 there are various levels of automation.

[1] Hand Flying : The pilot uses manual inputs to the control column and control wheel to control airplane attitude and manual inputs to the thrust levers to control thrust.

When hand flying the airplane will not automatically turn in response to movement of the HDG SEL knob - the only function of the HDG SEL knob is to move the magenta (pink) heading bug on each pilot’s EHSI (lower TV screen).

With this level of automation you will see :

no light in the CMD A (command autopilot A) and CMD B (command autopilot B) switches on the mode control panel; and,

no annunciation in the top right corner of each pilot’s EADI (top TV screen); and,

both F/D (flight director) switches (located just below the COURSE knobs) in the OFF (down) position and no green light above either switch; and,

the A/T ARM (auto-throttle arm) switch (next to captain’s course selector) in the OFF (down) position and no green light above the switch.




[2] Hand Flying with Flight Director : As above, but the airplane attitude required to comply with the selected mode (eg HDG SEL) is displayed on the attitude indicator as a prompt to the pilot. The pilot still has to move the controls.

With this level of automation you will see :

both of the F/D (flight director) switches (located just below the COURSE knobs) in the ON (up) position with a green light above one of the switches; and,

a green FD (flight director) annunciation in the top right corner of each pilot’s EADI (top TV screen); and,

a magenta (pink) flight director “command bar” above the white inverted V airplane symbol, like this :
http://homepage1.nifty.com/to-ga/767picpanel/eadi_pegasus_one.jpg




[3] Autopilot Engaged (CMD) / Auto-throttle Engaged : As above, but the autopilot will move the control wheel and control column to follow the flight director “command bar” and the auto-throttle will move the thrust levers.

With this level of automation you will see :

a light in one or both of the CMD A (command autopilot A) and CMD B (command autopilot B) switches on the mode control panel; and,

a green CMD (command) annunciation in the top right corner of each pilot’s EADI (top TV screen); and,

both the F/D (flight director) switches (located just below the COURSE knobs) in the ON (up) position with a green light above one of the switches; and,

a magenta (pink) flight director “command bar” above the white inverted V airplane symbol; and,

the A/T ARM (auto-throttle arm) switch (next to captain’s course selector) in the ARM (up) position and a green light above the switch.




In [2] and [3] above there are various autopilot/flight director modes that can be selected on the MCP (mode control panel – the panel with the COURSE selector at each end).


Roll Modes :

HDG SEL (heading select) : The autopilot/flight director will turn to and maintain the heading selected in the HEADING window.

VOR/LOC (VOR / localiser) : The autopilot/flight director will intercept and follow the selected COURSE to or from the tuned radio navigation aid.

LNAV (lateral navigation) : The autopilot/flight director will follow the lateral component of the flight plan programmed into the flight management computer.


Pitch Modes :

ALT HLD (altitude hold) : The autopilot/flight director will maintain current altitude.

SPEED (airspeed) : The autopilot/flight director will achieve and maintain the indicated airspeed or mach number selected in the IAS/MACH window.

V/S (vertical speed) : The autopilot/flight director will achieve and maintain the vertical speed (feet per minute) selected in the VERT SPEED window.

LVL CHG (level change) : The autopilot/flight director will climb or descend to the altitude selected in the ALTITUDE window at the speed selected in the IAS/MACH window.

VNAV (vertical navigation) : The autopilot/flight director will follow the vertical component of the flight plan programmed into the flight management computer.


Combined Pitch and Roll Mode :

APP (approach) : The autopilot/flight director will intercept and follow the ILS localiser and ILS glideslope signals to the tuned ILS radio navigation aid.



The black wheels that move furiously are the stabilizer trim wheels. There are two of them – one next to the captain’s right knee and one next to the co-pilot’s left knee. They are connected and both move at the same time. The stabilizer trim wheels are connected by a cable to the stabilizer at the rear of the aircraft. Take a look at the stabilizer trim index mark and the stabilizer upper and lower limit marks on the side of the fuselage next time you board through door 2L. The leading edge of the stabilizer should be more or less aligned with the index mark.

The leading edge of the stabilizer moves up and down to allow for pitch trimming throughout a wide range of speeds, thrust settings, and aircraft loadings. An airplane that is “in trim” will maintain more or less its present attitude even if the pilot takes his hands off the controls.

The stabiliser and stabiliser trim wheels move due to any one of a number of reasons :

[1] When hand flying (with or without the flight director) the pilot can adjust the stabiliser with his thumb using a stabilizer trim switch located on the outboard horn of each control wheel.

[2] When hand flying (with or without the flight director) at high thrust settings with the flaps extended a speed trim system will automatically adjust the stabilizer trim as required to keep the aeroplane more or less in trim.

[3] When flying with the autopilot engaged the autopilot will automatically adjust the stabilizer trim as required to keep the aeroplane more or less in trim.

[4] In extremely rare cases it may be necessary to adjust the stabilizer trim manually using the trim wheels - eg if the electric motor that moves the stabilizer fails. Before trimming manually it is important to switch off the stabilizer trim cutout switches (just below the FLAPS 40 position) so that the trim wheel cannot be moved unexpectedly by the electric trim motor.

There is a stabilizer trim wheel handle stowed within each of the stabilizer trim wheels. It can be rotated out from one or both stabilizer trim wheels and used to crank the trim wheel by hand. It’s very important to remember to stow the stabilizer trim wheel handle after using it because if you leave the handle out and then use the electric stabilizer trim it is very easy to get very hurt very quickly.

[flapsforty]

This is F U N. :ok:
After all these years in a very irritating fog (gorillas in the mist?) this is like bright sunshine. :)
Amazed you chaps can be bothered to take the time to write, format and present all this stuff in such a way that I can understand it; much appreciated. CY you are one hell of a teacher!

EggSplat, telling pilots what to do? :ooh:
I might be dumb, but I'm not that dumb mate. :p
As for not getting the chance to ask while jumpseating; kind of true that. The €80 I pay for my staff ticket definitely does not entitle me to the jumpseat. So when the pilots invite me there, either because all other seats are taken and they know I'm trying to get home or because they know that as a Purser I never otherwise have the chance to sit there anymore, I consider it a big favour. 737 cockpit small enough without an extra body, I'm in the way when they want to go to the loo, and a distraction to boot. So I try and shut up unless spoken to, and whenever spoken to, listen out for our call sign so I don't blab through anything and always try to talk about whatever subject under the sun they bring up.
Since this is hardly ever the instrument panel :) I ask my questions here instead.
Looking frwrd to my next flight; new understanding has descended. :D

[BOAC]

You can move it by hand for fine adjustments or make it spin really fast using a switch on the control yoke

Damn! I always thought THAT was for sharpening navigation pencils.

Flaps - there SHOULD be opportunity for you to grab a few minutes in a simulator - ask one of your company training captains - then you can fiddle with the knobs yourself:D

[McD]

And when the AP gets disconnected and after it has finished hollering and the pilot is flying by hand, do you actually point the AC at the runway yourself, or do you still use the heading select?
Once the AP is off, we're handflying -- physically moving the yoke in order to point at the runway (or wherever the aircraft needs to be).

Like CY said, the heading bug doesn't control the aircraft when you're hand flying. But, like Mike Jenvey said, it can be used as a good backup, such as a crosscheck reference, i.e., helping to visualize crosswind components, changes, etc.

One thing that CY said which is very important (which I think deserves extra emphasis) is that ".. there are various levels of automation." For instance, you might see someone hand-flying, but using autothrottles. Or you might see them using the Flight Director but still hand-flying and using manual throttles. Or, using the CWS mode (the buttons below the CMD A or CMD B buttons). The point is, there are times and places where varying levels of automation are completely appropriate, so you'll see lots of different tools used. And after all, that's what they (the FD, AP, and A/T) are .. just tools.

BTW, this is FUN for us too -- most of us here like talking about things like this. Of course, with some of us, once you get us started, you can't shut us up! ;)

[PPRuNe Pop]

McD...........I just noticed that!!! :D :D :D ;)

[airing cupboard]

In a B737, what's the difference between VNav Path and VNav Speed in descent? And why, if you are on a HDG and in VNav Path is the speed uncontrolled?
Thanks!

[chuck yeager]

In a B737, what's the difference between VNav Path and VNav Speed in descent?


[the following relates to B737NG FMCs with update 10.4 or 10.5]

Descent

VNAV can perform a descent in either of two modes – path descent or speed descent. During a path descent, the FMC uses idle thrust and pitch control to maintain a vertical path, similar to a glideslope in three dimensions. During a speed descent, the FMC uses idle thrust and pitch control to maintain a target descent speed, similar to a level change descent.


VNAV Path Descent

An E/D [end of descent] point must be defined in order to accomplish a path descent. It may be defined manually or by the selection of an arrival procedure.

The FMC defaults to the path descent for planning purposes. If the necessary information for a path descent is not available by the time the airplane reaches the T/D [top of descent] point, the FMC will revert to the speed descent mode.

At the T/D, the FMC commands idle thrust and pitch to follow the descent path.

Note : A path descent uses the target speed for planning purposes only. There is no attempt to maintain the target speed.

A path descent will automatically revert to a speed descent, or VNAV will disengage, if all required parameters are not maintained during descent.

A path descent must be initiated while within the allowable cross-track error for LNAV, however LNAV may be disengaged during descent while remaining in the path mode. To maintain a path descent under these conditions, the airplane must remain within a distance equal to twice the RNP from the LNAV course. VNAV will remain in path regardless of cross-track.


VNAV Speed Descent

A speed descent may be selected manually by selecting the SPEED prompt on the PATH DES page.

At the T/D, the FMC commands pitch to maintain target descent speed. LNAV does not have to be engaged in order to fly a VNAV speed descent.

[the above relates to B737NG FMCs with update 10.4 or 10.5]




And why, if you are on a HDG and in VNav Path is the speed uncontrolled?
Thanks!


Update 5 FMC : To initiate a path descent LNAV must be engaged. If LNAV is disengaged during a path descent, VNAV will change to a speed descent.

Update 7 FMC : A path descent must be initiated while within the allowable cross-track error for LNAV, however LNAV may be disengaged during descent while remaining in path mode. To maintain a path descent under these conditions, the airplane must remain within a distance equal to the RNP from the LNAV course. If this distance is exceeded, VNAV will change to a speed descent if no vertical angle is specified for the current leg. VNAV will disengage if there is a vertical angle specified.

Update 10 FMC : A path descent must be initiated while within the allowable cross-track error for LNAV, however LNAV may be disengaged during descent while remaining in the path mode. To maintain a path descent under these conditions, the airplane must remain within a distance equal to twice the RNP from the LNAV course. If this distance is exceeded, VNAV will change to speed descent if no vertical angle is specified for the current leg. VNAV will disengage if there is a vertical angle specified and LNAV is not engaged.

[BigHitDH]

I have some questions too, I hope you chaps don't mind!

When you enter your flightplan into the FMC, I understand you are prompted to enter the expected cruising altitude wind speed and direction and air temperature. What do you do, if when you get to your cruising alt, you find the weather to be quite different to what was reported/entered in? Does this not mess up your entire flight plan in terms of reserve/alternate/holding fuel? If so, how do you compensate for it?

I also know you are prompted to enter the weather at the destination airport. At what point in the flight do you enter this info? Do you enter the reported weather at departure, and update it when in ATIS range, or do you just leave it until you are in ATIS range?

I'm also interested in the whole route planning process. When you enter you flight plan into the FMC, do you enter the departure runway, SID, transition then put all your airways/fixes in, then your STAR and landing runway? What do you do if ATC changes your departure runway or SID? Do you have to quickly "edit" the route, or do you program several "expected" departures? Do you continually updatde your "alternate" airport en-route, or do you elect an alternate in the pre-flight breifing?

Sorry for the long list of questions, and sorry if I've got any of the terminology wrong!

[McD]

BigHitDH - Keeping in mind that the FMC is just one of your many tools to help you make calculations (and NOT to actually THINK for you), here's my personal techniques on some of your questions (I call them "my" techniques, but I think they're probably fairly standard in the industry) :

1) It's not uncommon to find that actual winds vary from forecast or projected winds at altitude, and it's really not a big deal. Most flight plans allow for such differences, as well as small deviations around bad weather, etc. And anyway, the FMC fuel computations will often differ slightly from the actual fuel state, so being good pilots, we're well accustomed to cross-checking actual fuel burn and quanity with what the FMC shows. When we note a significant difference, we have the option of updating the winds (either by data-link, or manually, since we're able to determine the actual winds once we're at altitude). The main thing, though, is that we keep a real-time fuel log (separate from the FMC) of actual fuel quantity for each portion of the flight, so that we can see what effect the change in conditions is actually having on our flight. This will help us determine any necessary change of action on our part.

Here's an example: Let's say that we planned a flight expecting to get a 40 knot headwind component at altitude. We get up to altitude and find that there is now a 77 knot HW component. Knowing that it will take longer (and burn more fuel), we can look at the effect it will have on the overall fuel state (do we need to change anything right away?), and we can look at other altitudes (winds less strong? better fuel burn if we climb? better TAS with lower winds if we descend?). Those are just some of our options.

2) Normally, I enter the weather about an hour before landing, but I'll update it, workload-permitting, with my last weather report prior to commencing the arrival. Again, these entries aren't critical -- one could fly the whole decent and approach just fine without making any FMC weather entries -- but it often helps for a more constant, fuel-efficient arrival.

3) I normally enter the flight plan as filed. (That includes the expected departure runway, SID, airways/fixes, and possibly the arrival procedure if that's on the plan. Then, when I get my pre-departure clearance (about 20 mins before gate departure) I'll update the runway, SID, or anything else that may be necessary. (Sometimes you get a runway or departure change just prior to takeoff - not a big deal if you're prepared.) I don't usually put in the landing runway until I have a good idea which runway(s) the arrival airport is using.

If an alternate is required, it will normally be designated on the flight plan, prior to the flight. However, we will use good judgment to update and change, if necessary, not only our arrival alternate, but also any en-route alternates.

As far as changes to the FMC -- they're not a big deal and can be usually be done very quickly, so editing the FMC is truly a non-issue 99% of the time. However, we prioritize the use of the FMC with the remaining workload of the cockpit. Since the FMC is only a tool, we don't necessarily need all its features to fly an approach and landing. So, as an example, if we get a short-notice runway change, and we're in the arrival pattern, and it's a VFR day, we may not change the FMC at all. Rather we'll exercise good pilot judgement by not going "heads-down" (to the FMC), and instead will fly a visual approach to the new runway"heads-up" (clearing, and other good old-fashioned "pilot-stuff"), perhaps using the ILS raw data (to the new runway) as a backup, as necessary.

Note to PPRuNe Pop -- looks like I just did it again! :O

[BigHitDH]

McD,

Thanks for the detailed reply, I appreciate you taking the time out to shed a little light on your lives up front.

Regards.

[NineEighteen]

This is an interesting thread. The AP is an area I never fully understood from my ATPL studies

Would somebody mind explaining the CWS (Control Wheel Steering?) function? Is it to allow hand flying whilst the AP takes care of trim and rudder movements etc.?

Thanks
0918

[BigHitDH]

From my limited understanding of the 737NG autopilot system, CWS mode seems to be quite fly-by-wire in it operation.

There are two modes, CWSp (Control wheel steering PITCH) and CWSr (Control wheel steering ROLL).

By having the autopilot in the normal CMDa or CMDb setting and pitiching the aircraft up (or down) with the yoke, the autopilot will automatically switch to CWSp pmodel allowing you to pass pitch commands direct to the autopilot via the yoke, while the autopilot maintains the selected heading/course/speed. It auto stabilises the aircraft for thrust induced pitch.

The same applies to CWSp if you manually roll the aircraft.

As far as I am aware it's much like the Airbus system in that you command an attitude, and when you release the yoke, the autopilot (in CWS mode) will do it's best to maintain that attitude/rate of turn.

[chuck yeager]

“Would somebody mind explaining the CWS (Control Wheel Steering?) function? Is it to allow hand flying whilst the AP takes care of trim and rudder movements etc.?”

Dealing with the last bit first....

The rudder pedals in the 737 are used for :

Tracking the runway centreline during take-off and landing; and,
Crosswind landings; and,
Flight with one engine inoperative; and,
To “lead” turns during manual reversion (loss of hydraulic systems A and B).

Other than that the rudder pedals are rarely used because there is no need. The yaw damper takes care of everything else :

Either yaw damper is capable of providing dutch roll prevention, gust damping and turn coordination. Yaw damper operation does not result in rudder pedal movement.

[this text relates specifically to B737NG ie 600/700/800/900/BBJ – the yaw damper in the 300/400/500s is similar but not identical]CWS has no input to the rudder.



Moving right along to CWS (control wheel steering)....

With CWS engaged, the autopilot maneuvers the airplane in response to control pressures applied by either pilot. The control pressure is similar to that required for manual flight. When control pressure is released, the autopilot holds existing attitude.

If aileron pressure is released with 6 degrees or less bank, the autopilot rolls the wings level and holds existing heading.You might wonder why you would want to use CWS. I wonder that too!

CWS might be useful if you wanted the airplane to hold an attitude, for example during a turbulence encounter.

There are several ways to get into CWS mode :

Press CWS A or CWS B button on the mode control panel.
Press CMD A or CMD B button on the mode control panel with no pitch mode or no roll mode selected.
Deselect the selected mode (eg press HDG button while in HDG SEL mode will deselect HDG SEL mode and result in CWS roll if you were previously in CMD mode).
Applying pressure to the control column will result in CWS pitch (if in CMD mode).
Applying pressure to the control wheel will result in CWS roll (if in CMD mode).

There are several ways to get out of CWS mode :

Select a valid mode (eg press HDG button will change the autopilot roll mode from CWS roll to HDG SEL).
Disconnect the autopilot completely to fly the airplane manually.

In CWS pitch mode the autopilot will adjust the stabiliser trim as required. If you use the control wheel thumb switch to trim the stabiliser whilst in CWS mode the autopilot will disengage and you will no longer be in CWS mode.

Please note that if you are in CWS roll mode with an angle of bank greater than 6 degrees the autopilot will maintain attitude (eg 10 degrees left wing down) but will not maintain any particular rate of turn (eg 3 degrees a second / rate 1).



If you’re having trouble trying to make sense of this stuff and wondering why anyone would design an airplane this way don’t be too put off.

The 737 is in many respects a very old airplane. Even on the latest NG versions much of the systems design work was done by drug-smoking hippies in the early to mid 1960s.

The 737NG was not so much “designed”, rather, it “evolved”.

Gordon Bethune did a fabulous job of managing the B737X project but freely admits (even boasts) that his famous “row 5 test” put the kybosh on lots of potential niceties.

An airplane designed fresh from a clean sheet of paper would look very different. Have you ever heard of a 777....