Autobrakes disarm immediately on RTO?

[kekstrom 1]

I have a problem: I noticed that my almost every single time I try to perform a RTO the autobrakes disarm almost immediately when closing throttles. This is the sequence: A/T armed, everything set up, RTO selected. I push TO/GA switch, start rolling, after 90 kts I disarm A/T and close throttles ti idle, sometimes autobrakes disarm immediately, sometimes I get a maybe 1 sec of braking action and the the autobrakes disarm. About 2/10 of my attempts end in a succesful braking an rejected takeoff though. My first thought was of course that it is a controller conflict because if I have understood correctly the autobrakes should disarm if throttles are advanced or speedbrake lever is moved. So I tried playing around with the controller setting but nothing helps. Then I even tried the following: I used the FS "disable joystick" button and disabled my controllers completely, used mouse and keyboard to start the takeoff roll, the above 90 kts or so cliked off the A/T and hit F1 to close the throttles and STILL the autobrakes disarm???

 

I've spent hours on trying to get it work but starting to get desperate. If somebody has any ideas please post them here:)

I am using CH throttle quadrant, CH pro pedals and flightsim yoke. Before starting FS I start the CH manager and download the controllers in a "direct mode". Excluding this problem everything works fine with the controllers.

[g_precentralis 191]

Trying to reproduce your problem, but without success.

My configuration at take off:

FDs - on

AT - arm

speedbrake - down

autobrake - RTO (disarm light extinguished)

 

TOGA activated> rolling> HOLD mode activated> 100kts> announcing "REJECT"> slam the throttle levers to idle and speedbrake UP> autobrake active> switching AT to OFF> at 0kts autobrake disarm light illuminated.

 

You can try to disconnect your pedals completely from PC and try RTO again. Do you use FSUIPC? How your pedals deadzone is set?

[Levkov 8]

I don't think you can accidentally disengage autobrakes in rto with brake pedals because, to disengage them, you would have to apply more manual braking then the autobrake is already applying. If you have a spoiler lever asigned, maybe the conflict is there because autobrakes will disarm when you retract the speedbrakes...

[rsvit 16]

To arm RTO mode prior to takeoff the following conditions must exist:

• airplane on the ground
  
• antiskid and autobrake systems are operational
  
• AUTOBRAKE select switch positioned to RTO
  
• wheel speed less than 60 knots
  
• forward thrust levers positioned to IDLE
  

Autobrake disarms when:

• SPEED BRAKE lever moved to the down detend
  
• forward thrust levers advanced
  
• manual braking applied.
  

I don't think you can accidentally disengage autobrakes in rto with brake pedals because, to disengage them, you would have to apply more manual braking then the autobrake is already applying

 

First of all little pressure is enough to disengage autobrakes, secondly pilot cannot push the brakes harder than autobrake RTO.

[richardnobes14 13]

First of all little pressure is enough to disengage autobrakes, secondly pilot cannot push the brakes harder than autobrake RTO.

 

Actually you need to provide an equal or greater amount of braking force before the autobrake will Disarm, this is a safety feature to prevent accidental dis-arming of the autobrake

 

And yes, even when the autobrake is in RTO mode, the pilot could still provide equal braking force, if not more.

[g_precentralis 191]

Its really not clear does pilot need to out-force autobrake to disarm it, or its enough to just apply any amount of force on pedals. I think it could be very hard to out force autbrake system in RTO mode.

 

This is the best I found, but still not clear enough

Transition to Manual Braking

The speed at which the transition from autobrakes to manual braking is made

depends on airplane deceleration rate, runway conditions and stopping

requirements. Normally the speedbrakes remain deployed until taxi speed, but

may be stowed earlier if stopping distance within the remaining runway is assured.

When transitioning to manual braking, use reverse thrust as required until taxi

speed. The use of speedbrakes and reverse thrust is especially important when

nearing the end of the runway where rubber deposits affect stopping ability.

When transitioning from the autobrake system to manual braking, the PF should

notify the PM. Techniques for release of autobrakes can affect passenger comfort

and stopping distance. These techniques are:

• stow the speedbrake handle. When stopping distance within the remaining

runway is assured, this method provides a smooth transition to manual

braking, is effective before or after th rust reversers are stowed, and is less

dependent on manual braking technique

• smoothly apply brake pedal force as in a normal stop, until the autobrake

system disarms. Following disarming of the autobrakes, smoothly release

brake pedal pressure. Disarming the autobrakes before coming out of

reverse thrust provides a smooth transition to manual braking

• manually position the autobrake selector off (normally done by the PM at

the direction of the PF).

FCTM 6.45

[rsvit 16]

Actually you need to provide an equal or greater amount of braking force before the autobrake will Disarm, this is a safety feature to prevent accidental dis-arming of the autobrake

 

No. According to this site, 800psi (ie less than that required for autobrake 1) is enough to disengage autobrake on landing roll. To be honest i don't know what about RTO.

 

And yes, even when the autobrake is in RTO mode, the pilot could still provide equal braking force, if not more.

 

Equal - yes, but not more.

[rocketfs 2]

Do you also have this problem (autobrake disengage) after landing?

If yes, you might have pots in the CH pedals that are spiking, or even a wire with a bad contact. I have the same ones, you know....

 

Bert Van Bulck

[ajacied551 1]

I have a problem: I noticed that my almost every single time I try to perform a RTO the autobrakes disarm almost immediately when closing throttles. This is the sequence: A/T armed, everything set up, RTO selected. I push TO/GA switch, start rolling, after 90 kts I disarm A/T and close throttles ti idle, sometimes autobrakes disarm immediately, sometimes I get a maybe 1 sec of braking action and the the autobrakes disarm. About 2/10 of my attempts end in a succesful braking an rejected takeoff though. My first thought was of course that it is a controller conflict because if I have understood correctly the autobrakes should disarm if throttles are advanced or speedbrake lever is moved. So I tried playing around with the controller setting but nothing helps. Then I even tried the following: I used the FS "disable joystick" button and disabled my controllers completely, used mouse and keyboard to start the takeoff roll, the above 90 kts or so cliked off the A/T and hit F1 to close the throttles and STILL the autobrakes disarm???

 

I've spent hours on trying to get it work but starting to get desperate. If somebody has any ideas please post them here:)

I am using CH throttle quadrant, CH pro pedals and flightsim yoke. Before starting FS I start the CH manager and download the controllers in a "direct mode". Excluding this problem everything works fine with the controllers.

I have the same problem here and it only happens when performing a RTO, First time when FSX is started making a RTO all works fine but after that I can not make a RTO again the AUTOBRAKE disarm light illuminates But when landing and the autobrake is selected to 1, 2, 3 or MAX the system operates correctly. I can not figure out what is causing the RTO to fail. Same one have any idea ???!!!.

[kekstrom 1]

This is annoying as hell. I even experimented yesterday by unplugging all my controllers (flightsim yoke, ch thr quadrant and pro pedals) from my computer. Still, after 90kts, A/T off --> F1 for IDLE thrust, I get a swcond or two of braking action then autobrakes disarm. Any ideas anyone??

 

My addons: EZDOC, SQWKBOX 4, Activesky 2012, Aivlasoft EFB (on anoteher computer linked to main computer).

[g_precentralis 191]

You should open a ticket at pmdg support.

[kekstrom 1]

I think I FINALLY (after total 15h+ axperimenting) solved the problem. I can do RTO:s how many times I want as long as I do NOT engage reverse thrust during the deceleration. Immediately after I engage reverse, the next time I roll down the runway and execute RTO the autobreak disarm problems begins. Every time. And after that only solution is to restart FS. I can reproduce the problem every times like this.

 

If anyone would have the time tot try this out to see if it is a general bug or only a problem on my rig I would appreciate it very very much! So: First a few rejected takeoffs in one session with no engagement of reversers and then one with the engagement of reverser. On the next rejected takeoff after that I would expext the autobrakes to disarm immediately on idling the throttles. Please report here if you find similar results!

Thanks!

[ajacied551 1]

I think I FINALLY (after total 15h+ axperimenting) solved the problem. I can do RTO:s how many times I want as long as I do NOT engage reverse thrust during the deceleration. Immediately after I engage reverse, the next time I roll down the runway and execute RTO the autobreak disarm problems begins. Every time. And after that only solution is to restart FS. I can reproduce the problem every times like this.

 

If anyone would have the time tot try this out to see if it is a general bug or only a problem on my rig I would appreciate it very very much! So: First a few rejected takeoffs in one session with no engagement of reversers and then one with the engagement of reverser. On the next rejected takeoff after that I would expext the autobrakes to disarm immediately on idling the throttles. Please report here if you find similar results!

Thanks!

 

You cracked it !!! I performed the RTO several times without using the thrust reverser, every time the RTO kicks in.

As soon you use the thrust reversers during RTO. The next time the RTO fails.

[QF 737 2]

Well hello everyone. Happy New Year and all that.

 

I am having this issue right now. 5 RTO attempts, all successful, however, none of those were achieved using autobrakes. Was there a solution found to this issue?

 

Mike McKenna.

[fairchildbrad 0]

I was having the same issue but my cause was a little different, more procedural than a bug.

 

I was advancing the thrust levers manually to 40% then enadling TOGA mode but was leaving the throttle quadrent alone (still cracked open).  At RTO, I was using the F1 key but with the throttle quadrent still cracked open, the autobrakes were disabiling (like they should).

 

My T/O procedure now is N1 to 40%, TOGA mode enable, throttle quadrent IDLE.  RTO works like a charm now, except for the reverse thrust bug previously mentioned.