Differences between the AAX and PMDG737NGX

[SquadronLeader52 12]

Two beautiful planes, both well crafted and providing many hours of enjoyment.

I follow procedures and in most cases have enjoyable and successful flights in both planes. I am not sure that I could articulate in detail, to a 'non flight' person the differences in how the two planes are driven.

As I was thinking about it, I thought it might be interesting to ask the community as to how they would describe the differences.

Would welcome all thoughts. Thanks in advance if you respond.

[Cheyenne Chief Pilot 829]

A Boeing is flown by the pilot.

An Airbus pilot is flown by a bunch of computers.

(This should sum it up, somehow ...)

[Emi 5161]

In my opinion the biggest difference definatly is automation in the Airbus.

Flying in normal operations you might not notice any too big differences, but as soon as you "mistread" the plane as the pilot you'll notice it as the Airbus will mostly recover itself.
Also in the Airbus you have to care about much less systems. Usually you can say that if you're in a dark cockpit environment everything is going well.

So the biggest difference is (as Oliver said already) the philosophy behind the two systems. While you as the pilot have all the control in the Boeing this is simply not the case in the Airbus.

A very good example for this is the comparison between Autothrust and the Autothrottle. While you hardly ever move the throttles in the Airbus they will constantly move in the Boeing. This is because in the Airbus the throttles only command a mode to the autothrust system, while in the Boeing they actually command the thrust. In the 'Bus the thrust commanded has nothing to do with the throttle position in the first place. You can get TOGA thrust with the throttles almost in IDLE if needed.

Another good example are the flight control sytems:

In the Boeing you have the CWS mode of the autopilot which is pretty almost what the Airbus does if you do everything correct, but the Airbus goes further. The Airbus actually protects itself against "bad" behaviour from the pilot. It will not allow you to bank further than a certain angle or pitch. Also it'll override the pilots commands if they are seen as dangerous by the system. The Boeing does not have anything like this.

The greatest difference in the philosophies can be seen in the controls itself. While you have a really big yoke which needs much force by the pilot to be moved in the 737 you have a tiny joystick in the A320 which does not need any force at all to be moved.

[--- 170]

1. While you as the pilot have all the control in the Boeing this is simply not the case in the Airbus.

2. This is because in the Airbus the throttles only command a mode to the autothrust system, while in the Boeing they actually command the thrust. In the 'Bus the thrust commanded has nothing to do with the throttle position in the first place.

3. While you have a really big yoke which needs much force by the pilot to be moved in the 737 you have a tiny joystick in the A320 which does not need any force at all to be moved.

1. Not the case. You have full control as in any Boeing.

2. The problem is that in a Boeing the thrustlever position is not an indication of thrust. There have been numerous accidents where the pilots just tried to establish the correct thrust by checking the approximate thrustlever position and thereby failed to notice that the engine isn't working at all. That's the beauty of the Airbus. You have to check N1. No way to misjudge the thrustsetting like on a 'conventional' plane.

3. Flight controls on a Boeing are hydraulically powered so theoretically there wouldn't be the need for high force to move the controls. The main reason is only to add stability in gusty weather to avoid unintentional control deflection.

That danger doesn't exists to a much lesser degree with a sidestick, hence you don't need too much force. Nevertheless to move the sidestick to its limit does need considerable force IRL.

[--- 170]

A Boeing is flown by the pilot.

An Airbus pilot is flown by a bunch of computers.

But the computers make the Airbus a dream to handfly.

[Adrijan 193]

1. Not the case. You have full control as in any Boeing.

But how can you have full control when, let's say, you want to pitch up to 60°. You can do that in the Boeing, but how can you do that in an Airbus?

[Cheyenne Chief Pilot 829]

But the computers make the Airbus a dream to handfly.

That's where the "cheats" of a RW Airbus equal the cheats in desktop flight simulation ...

[Cheyenne Chief Pilot 829]

But how can you have full control when, let's say, you want to pitch up to 60°. You can do that in the Boeing, but how can you do that in an Airbus?

Direct law ...

[Adrijan 193]

And how can I exactly switch to it in the Airbus X A320/321?

[Cheyenne Chief Pilot 829]

The ELAC, SEC and FAC switches are all clickable ...

[Adrijan 193]

Of course, but that's not gonna switch into direct law, is it?

[Cheyenne Chief Pilot 829]

With both FACs switched off, you should be in direct law - not sure, though, whether that's simulated in the AAX ...

[Adrijan 193]

Oh right, thanks. Thought it could only be activated in certain system failures.
And yeah, it's not simulated in Airbus X

[Cheyenne Chief Pilot 829]

But I faintly remember a cheat to turn off the fly-by-wire-system completely - would be the next best thing ...

[Emi 5161]

But I faintly remember a cheat to turn off the fly-by-wire-system completely - would be the next best thing ...

Shouldn't be there in the AAX anylonger. In the old Airbus X there really was that one

1. Not the case. You have full control as in any Boeing.

2. The problem is that in a Boeing the thrustlever position is not an indication of thrust. There have been numerous accidents where the pilots just tried to establish the correct thrust by checking the approximate thrustlever position and thereby failed to notice that the engine isn't working at all. That's the beauty of the Airbus. You have to check N1. No way to misjudge the thrustsetting like on a 'conventional' plane.

3. Flight controls on a Boeing are hydraulically powered so theoretically there wouldn't be the need for high force to move the controls. The main reason is only to add stability in gusty weather to avoid unintentional control deflection.

That danger doesn't exists to a much lesser degree with a sidestick, hence you don't need too much force. Nevertheless to move the sidestick to its limit does need considerable force IRL.

1) Even though I know the first golden rule from the FCTM is "The aircract can be flown like any other aircraft", you know exactly what will happen if you want to do something stupid.

2) There may have been accidents because of this, but honestly, it was the pilots fault in this case, not the fault of the philosophy. Even Boeing says that you should only look at the displays and not at the Throttles position.

3) I know the Force-Feedback on the 737s yoke must not be there, but if you compare the force needed to move a sidestick to the full position and the force needed to move a yoke to the full position you have a great difference. So would you still say that this is one of the differences comparing those two? I say definatly yes.

[Adrijan 193]

Hold on, what cheat are you talking about ? The invisible button on right MCDU?

Sent from my Nexus 4 using Tapatalk 2

[Cheyenne Chief Pilot 829]

The AAX is not a failure simulator. Just forget about those simulated FACs.

Switch the FACs off IRL - that way you lose your protections and can pitch up 60 degrees ... if you really want to!

[Adrijan 193]

I know pretty good that Airbus X A320/321 is not a failure simulator, but how can a simple action of switching off flight augmentation computers (FACs) be considered a failure?

Nonetheless, I understand that this isn't simulated to keep the product in the mid price range.

Sent from my Nexus 4 using Tapatalk 2

[Joshua Che. 1601]

I know pretty good that Airbus X A320/321 is not a failure simulator, but how can a simple action of switching off flight augmentation computers (FACs) be considered a failure?

Nonetheless, I understand that this isn't simulated to keep the product in the mid price range.

Sent from my Nexus 4 using Tapatalk 2

This airbus is a "SOP**" simulator. Most of the daily to daily things are simulated. You dont switch a FAC off in real life on a commercial flight.

** my definition, and that means our definition can vary.

[Adrijan 193]

Of course, completely understandable. I didn't complain about that :-)

Sent from my Nexus 4 using Tapatalk 2

[--- 170]

This airbus is a "SOP**" simulator. Most of the daily to daily things are simulated. You dont switch a FAC off in real life on a commercial flight.

** my definition, and that means our definition can vary.

And you don't pitch up a 737 to 60deg either.....Furthermore switching the FACs off isn't the valid QRH procedure anymore for the A320 series to get into direct law.

BTW, to perform aerobatics you don't have to be in direct law (and you can perform a very nice aerobatic maneuver in normal as well )

[Cheyenne Chief Pilot 829]

This airbus is a "SOP**" simulator. Most of the daily to daily things are simulated. You dont switch a FAC off in real life on a commercial flight.

** my definition, and that means our definition can vary.

So there will be wind forecast entries and valid fuel predictions ... one day?!?

[dmncnpilot 19]

In basic privare pilot training it's tought to look at you engine indications, be it a single engine cessna, turboprops or a jetliner. I have never been tought to rely on thrust lever positions, you always look at your displays for an indication and you adjust from there. Yes, thrust lever positions give you a rough estimate, if they're rigged correctly but a pilot should never rely on it, hence including your engine displays into your scan.