Welcome, Guest. Please login or register.
Did you miss your activation email?

News: Precision Simulator update 10.91 (14 October 2019) is now available

Author Topic: Park Brake Set - Upper EICAS Annunciation  (Read 432 times)

Roddez

  • Join date: Jul 2009
  • Location: Sydney
  • Posts: 96
    • http://www.simulatorsolutions.com.au
Park Brake Set - Upper EICAS Annunciation
« on: Sat, 21 Sep 2019 20:42 »
A couple of days ago I was crawling around under the cockpit floor, looking for the Park Brake Set micro switch.  Eventually I found the little sucker, but it's behaviour was a little different to what I have come to expect from PSX.

When the brakes are off and the parking brake handle is down, the normally open contacts of the switch are indeed open.  The picture below shows the micro switch and you can see that the roller is not in contact with the cam that is attached to the parking brake lever.



When lifting the handle up, but NOT depressing the toe brakes, you will see that the cam rotates and the switch roller is in contact with the cam.  However this does not trigger the micro switch which means there will be no upper EICAS Park Brake Set message.



When you depress the toe brakes and lift the Park Brake handle, the cam rotates further and the micro switch does engage.



So, my question is simple:
1.  Is this switch out of alignment?
2.  Is the switch correctly aligned and the Park Brake Set annunciation will not trigger simply by just raising the handle.
3.  It's an airline option and anything goes... ;)

I have not had a chance to look at the AMM to see what it says, but then again if it's airline specific then two different manuals will likely contain two different answers. ;)

Cheers,

Rod.

John H Watson

  • Join date: May 2010
  • Location: On a pedestal
  • Posts: 2006
Re: Park Brake Set - Upper EICAS Annunciation
« Reply #1 on: Sun, 22 Sep 2019 03:17 »
Quote
When you depress the toe brakes and lift the Park Brake handle, the cam rotates further and the micro switch does engage.

Interesting. This mechanism was studied during beta testing. I don't know if it was an adjustment issue, but I recall trying it on a couple of real world 744s and the message appeared (without the pedals depressed). I think someone on the forum found the opposite to be the case post-PSX release (not sure if it was in a big sim or on the real aircraft).

The switch adjustment is done with the brake pedals fully depressed, but with a (temporary) 1/4 inch shim between the pawl and the bellcrank. I don't know if the shim compensates for wear and tear over the years. Rig pins are involved in the adjustment.

Anyway, depending on what version of the AMM you have, there are lots of pictures on how to do the adjustment. Hopefully this agrees with PSX. I very much doubt that there are airline options for this.


Hardy Heinlin

  • Moderator
  • Join date: May 2009
  • Posts: 10830
    • Aerowinx
Re: Park Brake Set - Upper EICAS Annunciation
« Reply #2 on: Fri, 11 Oct 2019 12:40 »
I just learned that an engineer at Virgin Atlantic just confirmed that the message will not appear just by pulling the lever while the pedals are released.

Maybe the reference that was used for PSX is or was a company modification indeed?


|-|

Gary Oliver

  • Join date: May 2012
  • Location: Farnborough, UK
  • Posts: 649
    • http://www.simfest.co.uk
Re: Park Brake Set - Upper EICAS Annunciation
« Reply #3 on: Fri, 11 Oct 2019 12:56 »
Hardy,

Although not at all the same as the real aircraft we have run into several people thinking they had set the parking brake in our sim, seeing the EICAS message and the plane rolling forward.

Our Parking brake handle is effectively a microswitch with a solonoid on it to pull it down.

What happens is someone doesn't depress the pedals fully, they lift up the handle which sets ParkingBrakeHandle to 1 in PSX, and then they release the pedals which unlike the real aircraft to not latch down and the plane starts rolling.

The added benefit of changing PSX to not display the message unless the brakes are really set in PSX should stop this happening.

Cheers
G

the mad hatter

  • Join date: Jun 2011
  • Location: TX
  • Posts: 401
Re: Park Brake Set - Upper EICAS Annunciation
« Reply #4 on: Fri, 11 Oct 2019 16:10 »
I had the same issue with the park brake and setting it, i.e  it would be set (via the aircraft micro switch) and the aircraft would roll fwd, we took a different approach for conflict resolution and wired to the arinic cards as these are more stable.. now everything is tickety boo  mostly  ... at times when the sim is first started and at the gate with park brake set the the aircraft will roll forward with no way of stopping it other than a complete reset.

John H Watson

  • Join date: May 2010
  • Location: On a pedestal
  • Posts: 2006
Re: Park Brake Set - Upper EICAS Annunciation
« Reply #5 on: Sat, 12 Oct 2019 07:17 »
Quote
What happens is someone doesn't depress the pedals fully, they lift up the handle which sets ParkingBrakeHandle to 1 in PSX, and then they release the pedals which unlike the real aircraft to not latch down and the plane starts rolling.

The real aircraft would roll if you didn't depress the pedals fully. If you don't depress the pedals fully, the pawl (on which the microswitch arm roller runs) won't mechanically latch on the pedal mechanism and the pedals would spring back up. When this happens, hydraulic pressure from System 4 or from the emergency accumulators can't get to the brakes.

Pulling on the park brake handle activates the park brake microswitch. The park brake microswitch closes the park brake valve which is a device to stop hydraulic pressure (applied by having the pedals depressed) from bleeding out through the antiskid valves. The different test results are most likely due to wear and tear, not because of some pointless airline modification.

Roddez

  • Join date: Jul 2009
  • Location: Sydney
  • Posts: 96
    • http://www.simulatorsolutions.com.au
Re: Park Brake Set - Upper EICAS Annunciation
« Reply #6 on: Sat, 12 Oct 2019 07:25 »
Hi Hardy,

According to one AMM:
Quote
When the parking brake lever is pulled, the movement of the linkage sets a micro switch. This passes power from the PARK BRAKE circuit breaker on the P6 panel to the close fields of the electric motor on the parking brake module. When the electric motor has cycled to the closed position, power and ground are provided to turn on the Parking-Brake-Valve-Closed Relay.

When the relay switches it establishes a path from the electrical interface units (EIUs) to ground, and
this permits the PARKING BRAKE SET indication to appear on EICAS.

Further in the manual, there is information about testing the operation of the parking brake.  Whilst this next section doesn't specifically reference the upper EICAS message, I read this to suggest that the parking brake message won't display because the parking brake is not engaged.

Quote
(a) Push on the captain’s left brake pedal and pull the parking brake lever on the control stand.
1) Make sure the parking brake will not engage.
(b) Push on the captain’s right brake pedal and pull the parking brake lever on the control
stand.
1) Make sure the parking brake will not engage.
(c) Push on the first officer’s left pedal and pull the parking brake lever.
1) Make sure the parking brake will not engage.
(d) Push on the first officer’s right pedal, and pull the parking brake lever.
1) Make sure the parking brake will not engage.

To provide a definitive answer, I will try and follow the instructions in the AMM and use rigging pins and shims to calibrate the parking brake micro switch in a cockpit here in Sydney.  This might make a good exercise for some of us during WorldFlight.

Avi

  • Join date: May 2009
  • Location: LLBG
  • Posts: 775
Re: Park Brake Set - Upper EICAS Annunciation
« Reply #7 on: Sat, 12 Oct 2019 13:27 »
We can ask Gilad to make a test (and if he isn't a pilot - and I think he is, he knows one)  :)
Avi Adin
LLBG

Hardy Heinlin

  • Moderator
  • Join date: May 2009
  • Posts: 10830
    • Aerowinx
Re: Park Brake Set - Upper EICAS Annunciation
« Reply #8 on: Sat, 12 Oct 2019 15:25 »
Gilad is 100% a 744 pilot :-)

We've got confirmation now from various airlines that the pedals need to be depressed for the message. I'll modify PSX accordingly and I won't make it a company option.


|-|ardy

the mad hatter

  • Join date: Jun 2011
  • Location: TX
  • Posts: 401
Re: Park Brake Set - Upper EICAS Annunciation
« Reply #9 on: Sat, 12 Oct 2019 15:57 »
Hang about we must be doing something either right or wrong, we use the aircraft components including P6 circuit brker, which functions, this in turn is wired to the aircarft nose gear landing light ( real ) when the parkbrake is on (depressed) pedals down parkbrake lever up, we get the red light on the nose gear box and the message in the flightdeck stating it is on when the parkbrake is released both the light and the message disappear (the rolling is related to a card issue) not PSX

I kinda think because I have a Frankin sim that because there is no Hydraulics the actual aircraft components is not seeing them ? and therefore PSX does not see them when the sim is first started and a reset is required, when the sim is restarted I am guessing the hydraulics system is pressurized in PSX and the aircraft see them thus the rolling stops.. but this is just a wild **** guess 
« Last edit: Sat, 12 Oct 2019 16:16 by the mad hatter »

Hardy Heinlin

  • Moderator
  • Join date: May 2009
  • Posts: 10830
    • Aerowinx
Re: Park Brake Set - Upper EICAS Annunciation
« Reply #10 on: Tue, 15 Oct 2019 00:09 »
Modification of "PARK BRAKE SET" message logic is now available in PSX version 10.91:

http://aerowinx.com/board/index.php?topic=4191.0


|-|ardy