PMDG737NGX Autobrake problem

[Captain Sam 0]

Hello,

When ever I use the autobrake on landing, I found that autobrake 1, 2, 3, and MAX all use max braking. How can I fix this? Thank You.

 

Sam

[downscc 1,327]

Sam, full names in the PMDG forums please.

 

How have you tested this hypothesis?  I experience distinct differences between autobrake 1 and MAX.  Remember, landing speed is a factor because the brake effort is a specific rate of deceleration, the faster you land the much further it requires to slow to taxi speed for example. Normal landings are with reverse thrust, which masks the autobrake effects to some degree.

[Captain Sam 0]

I accelerated down a runway and then idled the engine. I set the autobrake to 1. I did the same thing again and set the autobrake to MAX. I recorded both trials, and found the change in speed person 3 seconds. They both were the same.

 

Samuel Saminston

[dave_paige 11]

I believe if you test it the way you did, as if it is a rejected takeoff (RTO) then the system, in that particular case, always uses max braking. The assumption is that you have minimum runway left on which to stop. I suggest trying the test again using normal landings.

 

Dave

[downscc 1,327]

Dave is right on, the RTO braking effort is going to be MAX (FCOM 14.20.4).  At MTOW, it's actually the most dangerous maneuver done in a flight certification test package LOL

[Captain Sam 0]

Okay. So after hours of recording, I have been able to test autobrake with real landings. I have noticed that autobrake 1 still uses MAX braking. I wonder if this has to do with the fact that my brakes are a button, not an axis since i use a joystick.

[downscc 1,327]

Sam, do yourself a favor and set up a signature block to make adding name to post automatic. See your Profile in upper right corner of this page.

 

 

 

I wonder if this has to do with the fact that my brakes are a button, not an axis since i use a joystick.

 

Not at all, but remember as soon as you touch the brake button, in your case, you have cancelled automatic braking.

[Ebs 114]

I have noticed that autobrake 1 still uses MAX braking. I wonder if this has to do with the fact that my brakes are a button, not an axis since i use a joystick.

 

Hi Sam,

 

I think you've just explained what went wrong, it sounds like that when you touch down, you're manually activating the brakes with your joystick button. Do not do this until later in the roll out.

 

Autobrake applies the brakes automatically (hence the name!) if you try this with the different autobrake settings, I'm sure you'll see the difference.

[Captain Sam 0]

I disabled the joystick brake button to make sure i wouldn't accidentally press it. I ran the test once again, and it seems like I am still getting full autobrake.

 

Samuel Saminston

[Ebs 114]

 

seems like I am still getting full autobrake.

 

Sam, run the test again and see if you can get a screenshot of the PFD (and the autobrake knob in the picture) and post that here.

Maybe someone here can spot something wrong?

[Captain Sam 0]

Because I'm a total noob and can't find out how to attach images: http://postimg.org/gallery/13r1sajl2/6223033d/

 

Notice the speed trend stays the same on all autobrake settings. (except for autobrake 1 and that's because the engine wasn't idled.