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Yori Smulders

77L autobrake, She stops in a dime!

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HI,

 

I have a question.

 

I have done many flights now with the T7, but one thing that is keeps coming up is that the autobrake on landing is pretty heavy (she stops in a dime). it is almost unrealistic!!

 

I landed flaps 24 VREF 146 (landed VREF +5)

She was only 2tons under MLW. (14t fuel left, full pax, 31190t cargo)

I used Autobrake 2 and idle reverse thrust.

No significant winds. something like 5-6 knots of headwind

 

Still she stopped so insanely fast!!!

 

So how is this done in real life? Cause this gives me the feeling that they use no autobrake at all! just spoilers, reversers and then some manual braking under 60 knots. 

 

I watched some movies on the real T7. watched some real world landings, also witnessed one from the cabin but none stopped so fast as my bird.

 

Anybody have the same idea??

 

 

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This gets brought up every now and then.  I solved my problem using this product http://www.thefsps.com/SPX.html  It can run networked of another PC

 

I also combined it with the friction fix using a reg fsuipc.

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Is this Issue going to be fixed in SP1??? forgive my laziness, its 00.40 am and I didn't look for the thread with all the bugs listed!!! Don't see why I should buy another program to fix this, but again the temptation is there..

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Is this Issue going to be fixed in SP1??? forgive my laziness, its 00.40 am and I didn't look for the thread with all the bugs listed!!! Don't see why I should buy another program to fix this, but again the temptation is there..

 

 

I wouldn't really call it an issue, Just a limitation of FSX. when you start adjusting roll out distance you also change the take off distance. 

 

The PMDG 777 also doesn't care if the runway is wet or contaminated. Programs like SPX and FScaptain correct this, so well worth the money in my opinion.  Am sure the bulk of people don't really care hence why it is not mentioned that much.

 

Regards

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You also need data to know this isn't in fact accurate.  "She stopped so insanely fast!!!" is subjective.  You need a landing distance to compare to performance numbers to know if this was indeed too fast. 

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I wouldn't really call it an issue, Just a limitation of FSX. when you start adjusting roll out distance you also change the take off distance.

I must take your advice then, the program looks so complex only want realistic braking, not all the rest of bells and whistles.

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I must take your advice then, the program looks so complex only want realistic braking, not all the rest of bells and whistles.

 

No it is not complex at all. You simply decide what you want simulated and then the whole thing is fire and forget. When I start my sim it automatically links to SPX, I don' t touch a single thing.

 

It only looks complex because it gives you a graphical display of all the parameters on your aircraft right down to how much ice is building on each surface. 

 

@Eric - As mentioned this has been discussed before. many times. I don't think this is an issue or fault of PMDG, just a sim limitation.  I did RTO's in a 777 sim  way before the PMDG T7 was out.  

 

You can see this in many aspects of desktops sims, it's just limitations we have to live with. They behave very accurate considering the platform and price we pay.

 

Regards

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This was brought up before. The way i managed to test this, was to use a payware scenery and assuming the distances from the runway threshold to a particular taxiway exit was accurate to the real world chart, i compared the stopping distance of a particular approach speed and autobrake setting with the numbers in the flight manual under the autobrake landing distance table, and it APPEARS to be correct. Until we can get a utility that can accurately measure the distance traveled when the brakes are applied im afraid testing it this way is the best i could come up with.

 

EDIT: Im assuming why we are not used to it stopping so fast is because 12 wheels are doing the braking vs the 4 in the 737 (or similar type) or 8 in the 767 that we are used to.

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How about TSR Autobrake to add to the mix?

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How about TSR Autobrake to add to the mix?

Tell me more Imran, never heard of TSR

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Tell me more Imran, never heard of TSR

 

TSR was pretty good back in the day. It's pretty clunky to setup but I would use it with the MD11. These newer products make things a lot easier. More importantly is the fact you can set these products up over a network and forget about it.

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TSR was pretty good back in the day. It's pretty clunky to setup but I would use it with the MD11. These newer products make things a lot easier. More importantly is the fact you can set these products up over a network and forget about it.

Cheers Rob. I might have to blow the dust off FS captain then. I did not realize that FSC can help like SPX.

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TSR Autobrake an addon to fix the FSX limitations of braking... Need a reg copy of FSUIPC for it to work and is no longer sold.

 

Anybody have a copy of the sim1.dll patched file to fix the friction? Email in my profile. Thanks

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So all in all. It seems that the PMDG 777-200LR braking is about right for a real 777-200LR on a dry grooved runway with tyres and asphalt in perfect condition.

 

However it is not accurate in rain, ice, on contaminated or compromised surfaces etc, but an addon which effects ALL of FSX (including default aircraft, other addons by other companies etc) can simulate these other conditions.

 

Its basically like:
Flightsim misconception: The plane is bigger so the brakes won't work as well

Reality: The plane is bigger so they put 12 wheels on it and made the breaks work better to compensate.

 

Remember also: 737-800 typical V-REF is around 139 flap 30. 777-200LR typical VREF is around 137 flap 30. The bigger wings/flaps make more lift so the approach speed is lower, even with the larger/weightier plane.

 

Several ATC guys I know have mentioned that the A380 has a lower approach speed than most 737-800's. (but takes longer to stop, in no small part due to the fact that only 2 out of it's 4 engines can go into reverse thrust!)

 

Nevertheless, without this thread I wouldn't have heard of SPX, so... good thread  B)

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I just tried SPX, while it does make landing and taking off in adverse weather conditions more interesting, one thing i noticed when i tried an aborted takeoff in heavy rainfall (SPX indicated that the friction was very poor). The brake temperature indication on the GEAR synoptic is much lower with SPX ON than with it OFF. Aborting takeoff with a GW of 689,000lbs at HKJK at a speed of 145kts peaked the indications at 4.8, while with SPX OFF the indications got up to 6.7 before the aircraft came to a complete stop (somewhere below 40kts). So when the developers say that using things like friction modifiers can produce non-normal behaviours, this is an example of what they meant. One could probably argue that the less effective braking in heavy rainfall/standing water would automatically produce lower brake temperatures, but i will leave that to the Physicists and engineers to decifer.

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No point trying to compare the two with any kind of rain or snow. The PMDG 777 behavior is completely unrealistic, as you say the T7 still behaves like it is on a perfect bone dry runway.

 

Also make sure you have Anti skid turned off in SPX, the PMDG A/B already has this built in.  As usual it is all in the documentation that comes with SPX.

 

Regards


 

 


(but takes longer to stop, in no small part due to the fact that only 2 out of it's 4 engines can go into reverse thrust!)

 

This doesn't really make any sense, at least on a non contaminated runway, autobrakes modulate and reverse thrust is not factored into stopping distance. Also the A380 has brake to vacate as standard.

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Its basically like:

Flightsim misconception: The plane is bigger so the brakes won't work as well

Reality: The plane is bigger so they put 12 wheels on it and made the breaks work better to compensate.

Unless my memory is off, I thought I read that they put twelve wheels on the main gear for weight reduction since the other option would have been to go the way of the DC-10-30 by adding the center landing gear.

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Unless my memory is off, I thought I read that they put twelve wheels on the main gear for weight reduction since the other option would have been to go the way of the DC-10-30 by adding the center landing gear.
Pretty much.

 

 

 


Its basically like:
Flightsim misconception: The plane is bigger so the brakes won't work as well
Reality: The plane is bigger so they put 12 wheels on it and made the breaks work better to compensate.
Interesting calculation (and quick n dirty): 737 landing at 60tons = each brake unit has to absorb the energy of 15tons traveling at say 130kt. Now lets take a 77L landing at 215tons, that's 17.9tons per brake travelling at 140kt. Scale that up to a rejected takeoff; 737 - about 18tons per brake. 77W - 29.25tons per brake. So yeah, better brakes with more discs on the bigger planes. RE A380, I believe it only has brakes on 16 of the 20 main gear, that coupled with half reverse thrust accounts for looong rollouts.

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RE A380, I believe it only has brakes on 16 of the 20 main gear, that coupled with half reverse thrust accounts for looong rollouts

 

Read the whole thread, reverse thrust does 'not' affect roll out distance. Autobrakes modulate on every setting except MAX/RTO

 

Once again, the A380 uses brake to vacate (BVT) it aims to vacate you at whatever turn off you have selected.

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FLEX1978, on 04 Jul 2014 - 12:03 AM, said:

Read the whole thread, reverse thrust does 'not' affect roll out distance. Autobrakes modulate on every setting except MAX/RTO

 

Once again, the A380 uses brake to vacate (BVT) it aims to vacate you at whatever turn off you have selected.

You are correct. 

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Read the whole thread, reverse thrust does 'not' affect roll out distance. Autobrakes modulate on every setting except MAX/RTO

 

Once again, the A380 uses brake to vacate (BVT) it aims to vacate you at whatever turn off you have selected.

 

That is a pretty neat feature indeed!

 

The shortest stopping-distance is archieved by max. MANUAL braking combined with reverse thrust. 

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I've taken Rob's advice and purchased Sim Physics X - at the PC Aviator Sale...to fix the Limitation of braking.

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I've taken Rob's advice and purchased Sim Physics X - at the PC Aviator Sale...to fix the Limitation of braking.

 

A cool little extra thing I noticed through SPX -The PMDG 777 Anti ice switches work perfectly with this addon (Auto and manual use)  But make sure you switch off Elevator & rudder icing, I think that was designed for light aircraft. 

 

Am very pleased with what FSPS have been releasing over the last year or so. A very smart bunch of developers, just be sure to read the docs that come with the products! :)

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