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74X Autobrakes 1,2,3,4???

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Hi there,For some reason, the 74X autobrake setting makes absolutely no difference to the rate of deceleration.Autobrake 1 gives me the same rate of deceleration as Autobrake 4. The aircraft comes to a very abrupt halt!Anyone else have this problem???Martin Neep

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Can anyone help with this issue? It's very frustrating and ultimately deems the autobrakes useless. How can I fix this?Martin Neep

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You know I have the same problem so you're not alone. Its so bad I've just stopped using the auto brakes except for RTO.

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Have any of guys tried the autobrakes without your brake pedals connected? Either physically disconnect them before landing or use the default FS key assignment CTRL+K and try. It might be a controller issue. I have not seen anything like this reported here on the forum or by the beta testers.Hope it helps,

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I don't have rudder pedals, I just use the basic "period" key to operate the brakes manually. Just as a test, I unplugged my CH yoke while on approach and allowed the A/P to perform the landing. With the autobake set to 1, The same thing happened. A second or two after the main wheels touch down, the "BRAKES" message is shown in the bottowm left of the screen. Then the nose wheel slams onto the runway and the airspeed trend vector plummets! The aircraft halts within a few hundred metres???

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Hello all.I'm not sure about what I am going to say but I hope it might help you.I think the difference between Autobrake 1, 2, 3, .... is not the power of braking but the moment when the plane becomes braking.When you set AutoBrake 1, the brakes become working later than if you set A.B.4 (in this case the brakes works immediatly after touchdown, while with A.B.1 the brakes become working maybe 4 seconds after touchdown).It's the case with Airbus for example. If I remember the autobrake in LOW position works 3 seconds later than the autobrake in MEDIUM position.I hope this would help you.I am sorry if I'm mistaken.Bye.Thomas.

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Braking in the B744 is designed to give a constant rate of deceleration, whether provided by the wheel brakes or, in addition, the spoilers. In other words, the more spoiler used, the less the wheel brakes have to take the deceleration responsibility.Cheers, Richard

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QUOTE: "Braking in the B744 is designed to give a constant rate of deceleration, whether provided by the wheel brakes or, in addition, the spoilers. In other words, the more spoiler used, the less the wheel brakes have to take the deceleration responsibility."Yes, I agree. But... the autobrake setting should still have an affect on the rate of deceleration. In a simulator, you do not know which component is actually having the braking effect:QUOTE: 747-400 Autobrake Selector:"1,2,3,4,MAX-Engages autobrakes upon touchdown.-May be disengaged by moving the speed-brakes to the DN detent, or by advancing any thrust lever, or by manually braking.-DECELERATION RATES ARE INCREASED FROM 4ft/sec2 AT POSITION 1 UP TO 11 ft/sec2 AT POSITION MAX." Regards,Martin Neep

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Martin,I think the poster you respond to was correcting the previous poster who implied the different settings might have an impact on a delay.You are correct. And your problem is a strange one. Care to take a screenshot during the braking segment? We can check the trend vector on the speed tape and derive a deceleration rate. Also what is the time from wheels on ground to wheel stop?Hope it helps,

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Totally misread that post, sorry!I'll take a look.

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These two were taken in identical conditions. One is set at A/B 1 and the other, A/B MAX. As you can see the trend vectors are the same length.The caution message in the second clip was "hot brakes".

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"I think the poster you respond to was correcting the previous poster who implied the different settings might have an impact on a delay."On the 744 there is a pressure ramping system. Variations may occur depending on Brake System Control Unit model numbers, but I have the following values:An initial pressure spike of 1650 (to let the pilots know the A/B's are working).This is followed by a pressure increase of 150psi for 2 seconds, followed by a 450psi/sec increase to the autobrake selected pressure or deceleration rate pressure.Max Brake PressuresA/B position 1: 1,300psiA/B position 2: 1,500psiA/B position 3: 1,750psiA/B position 4: 2,050psiA/B position MAX: 3,000psiA/B position RTO: 3,000psiThere is a small 0.1 second delay, but nothing like Airbus delay valuesCheers.Q> Ян

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Well, does anybody have any idea what could be causing this problem? From what's been said, it doesn't look like anybody else is experiencing it, so where am I going wrong?

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Have you tried shooting PMDG support an email? I think you're right, no one is, or has, experienced this. I know I'm stumped.Cheers,

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I must admit, I've never really noticed much difference in rate of braking with different autobrake settings.. I might look into this in more detail tonight when I get time.. see what it looks like..CheersCraig

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