Brakes overheating to easily?

[Ephedrin 418]

I‘ve never ever had issues with my brakes in the 747 and 777, even if I used them to slow down before turns on the taxiways. I really begin to wonder if there might be an issue with the assignment method of the brakes. I had the Saitek rudder pedals and now I use the MFG pedals. I‘ve assigned them via FSUIPC and calibrated them from around 16000 (instead of 16384) to  -16000. absolutely no issues. If I tap them down for an „emergency braking action“ I kill my tires, so the PMDG wreck-your-plane-system works. But beside this there‘s nothing wrong using my brakes slightly. I notice my temperature increase on the lower DU but not that much that I would even become worried. 

Except missing null zones, could there be an issue with the FSX/P3D assignments when using PMDG aircraft?

[MarkJHarris 128]

I'll elaborate then. 

Once you unstick after start, idle thrust on a high bypass turbofan should mean the aircraft will gradually pick up speed on level surfaces. (I have found it does so more in hot environments on the 737?). Thus to taxi, you should need a little lift ( no more than 40%N1 on a 737-800 at max take off weight) and then back to idle once it starts moving. 

Trainers often have to remind crews initially not to ride brakes but to brake when speed picks up too much, slow to walking pace then let it roll on. 

With Steel brakes, you just add temperature if you make smaller regular inputs, but Carbon Brakes wear differently. Essentially they wear out per application. Tapping away every few seconds, even gently, will rapidly wear down carbon/carbon brake systems and cost a fortune. Use them when you need to, then get off them until you need them again. 

I used to find landing at LTAC that a single application on landing, until I reached walking pace at the end of the high speed turn off, meant that once turned, it would roll to the ramp entrance and only need one more gentle application. Then we shut one down and I could roll to the gate and only use the brake once more as we slowed to the stop position. That's how you save carbon brake costs.

 

It's accepted good practice not to keep speed back with regular light brakes, but to slow right down and release. Rolling along like this will minimise temperature rise and allow cooling between applications to take place.

I hope that helps.

[KLM57 0]

I really don´t know how to overcome the problem with overheated breaks and exploding tires as long as PMDG keeps telling us, that we are doing something wrong and not admitting, that for simming purposes the 747-8 is bit too real in this respect...

[downscc 1,327]

18 minutes ago, KLM57 said:

I really don´t know how to overcome the problem with overheated breaks and exploding tires as long as PMDG keeps telling us, that we are doing something wrong and not admitting, that for simming purposes the 747-8 is bit too real in this respect...

 

Practice.  Put the GEAR synoptic on the MFD and watch the temperatures when you brake.  Learn how to taxi without braking, it is possible to get up to 20 kts on a long straight stretch and then slow to 10 kts for a 90 deg turn with minimal or no use of brakes.  If you are limited to a button or key for braking then this is going to be a challenge because the only time you should use 100% braking is in an emergency.

[MELKOR 5]

I'm hardly a newbie at this. The behavior I'm seeing with the 747 brakes is new. I haven't been able to consistently reproduce this, but there are times when just briefly touching the brakes causes a +1 increase in the temps; How can that be right or normal, in any circumstance??

I will continue to try to find a repro case and will post a video when I figure it out.

Thanks.

 

[Meekg 86]

3 hours ago, MELKOR said:

The behavior I'm seeing with the 747 brakes is new.

I agree it has changed. How about maybe it has been improved?

I always thought brakes were hardly heating previously so I'm actually glad to see that changed. I think it's just a matter of tweaking the hardware and getting used to braking technique.
Just for info, I use FSUIPC with type specific custom slopes for nearly all my addons.

 

Edited October 30, 2018 by Meekg

[Richardnunez 5]

12 hours ago, KLM57 said:

I really don´t know how to overcome the problem with overheated breaks and exploding tires as long as PMDG keeps telling us, that we are doing something wrong and not admitting, that for simming purposes the 747-8 is bit too real in this respect...

 

There is nothing wrong with it you just need to get used to it use the auto brake until 40 knots and then just be sensible with the throttle and the breaks  that’s the all point of it to be as real as possible 

richard Nunez 

[Richardnunez 5]

59 minutes ago, Meekg said:

I agree it has changed. How about maybe it has been improved?

I always thought brakes were hardly heating previously so I'm actually glad to see that changed. I think it's just a matter of tweaking the hardware and getting used to braking technique.
Just for info, I use FSUIPC with type specific custom slopes for nearly all my addons.

 

They already mentioned before they are using new braking system on the 800 that’s why the behaviour is different 👍👍

[downscc 1,327]

The trick I use is to watch the GS indication on the ND when I brake.  I slowly apply toe braking until the GS numbers start to drop... one.., two..., three kts.  If it is a slow decrease in GS then you are doing it right and the brake temps will not shoot up. Slow steady pressure, the hard part is learning how little or how much pressure and that depends on your hardware and settings.  I am using Saitek pedals, calibrated in P3D, nothing fancy.

[jon b 2,047]

I have to admit I too was of the opinion the brakes on the 744 overheated way too much on taxi ,HOWEVER........

I've just taken the 744 out for a ride using my new Thrustmaster TPR rudders for the first time with this aircraft, and also used the TM warthog for  fine throttle control. As well as using the new hardware I made a real effort to taxi the 74 in a realistic manner. That means 10kts max around turns , about 15-20 max on the straight, slowing up I gently squeezed the brakes just a couple of mm as I would in real life and as Dan mentions above paid particular attention to the GS display to obtain a realistic deceleration rate, as you cant feel the deceleration as you would on the real jet. And you know what, the brake temps were spot on. Autobrake 3, manual brakes from 50kts on landing at a rather heavy 270T gave me mainly 2s and the odd 3, I did a long taxi in and didn't heat up the brakes any more. I cooled the brakes from the menu on the turnaround took a long taxi out deliberately going up to 20kts then slowing to 10kts take a few 90 degree turns using the correct techniques again just to experiment, and I got to the runway showing zeros all round.

I think my previous issue was 10kts just looks so slow in the sim in this bird so was probably taxing way too fast, plus applying way too much brake and slowing down way too fast. The TPR is definitely a big improvement and taxing is now a pleasure but I think the biggest thing is as Dan says , watching that GS readout for a realistic rate of deceleration, it only needs a slight pressure on the pedals to slow up from 20kts not a big squeeze as I've been guilty of before. Must try harder !

Cheers

 

Jon Bunting 

[Captain Kevin 586]

On 10/27/2018 at 2:15 PM, MELKOR said:

During VATSIM's hugely popular "Cross the Pond" event today, there was a very long wait from pushback to takeoff (I was number 30 or so in the conga line at KJFK!)

Twice during this extended taxi process in my 747-400, I had multiple tires blow out due to severely overheated brakes, and had to use the maintenance page to repair the tires and cool the brakes.

I certainly wasn't doing anything unusual w.r.t. braking. Nothing I haven't done hundreds of times in the part.

Took me 38 minutes from the time I pushed back to the time I got to runway 4L, but I didn't have any issues with brake temperatures when I did this in the 747-400.

[adl320 3]

On 9/28/2018 at 3:13 PM, xkoote said:

Had the same issue just now for the first time. Just bear in mind that braking a 747 from 60 or 70 knots to 0 should not cause brake temperature problems given decent starting brake temperatures (e.g. coming in from a long haul) Whether you stand on the brakes or slowly bring it to a stop, it's the same amount of kinetic energy. Now if the anti skid can't cope and you skid and rupture tires is another story. In principle, having FSUIPC set to super sensitive or not shouldn't make a difference. However, I'll try these settings and hope it helps...

 

Xander

I had the same issue with overheating brakes simply taxiing from the stand to the runway in ANC. And no, I wasn't "abusing" the brakes or using them other than to slow slightly for the 4 turns I had to make to get to the departure end. The only two flights I've flown I've landed with brake temp issues and had to call up the maintenance screen to replace the brakes and tires.

If FSUIPC is a contributing factor and we all need to adjust "slope" how about PMDG issue an AD on this so that all customers who may be experiencing the issue can rectify? To me it seems as if FSUIPC is being used to compensate for aggressive brake sensitivity in general.

Aaron

[downscc 1,327]

17 hours ago, adl320 said:

And no, I wasn't "abusing" the brakes or using them other than to slow slightly for the 4 turns I had to make to get to the departure end.

How do you know... as Jon pointed out you cannot feel the deceleration rate in a simulator.  I don't use FSUIPC for any axis so I cannot speak to the use of response curves... I'm happy with the straight line.  Just keep an eye on GS when braking.  If the numbers decrease slowly then you are doing it correctly.

[skelsey 765]

18 hours ago, adl320 said:

I had the same issue with overheating brakes simply taxiing from the stand to the runway in ANC. And no, I wasn't "abusing" the brakes or using them other than to slow slightly for the 4 turns I had to make to get to the departure end. The only two flights I've flown I've landed with brake temp issues and had to call up the maintenance screen to replace the brakes and tires.

Out of curiosity, not being familiar with Anchorage, how far was your taxi and how fast were you going?

I only ask as I know that there is a note in the B747 FCTM about how long taxi distances at high gross weights (without mention of brake application) can lead to tyre sidewall heating to an unacceptable level and to avoid taxiing at >20kt for long distances at high weights.

My only other thought is -- are you sure your brakes are not dragging? If you disconnect your rudder pedals, do you still get brake heating problems? I only say this as my experience of flying with a variety of people in shared cockpit (not in the 747, obviously!) is that a remarkably high proportion of those with hardware rudder pedals have had one or more draggy brakes.

[Budbud 227]

Hi,

I don't have any overheating issue with either the 744 or the 748 during taxi.

So I don't think it comes from the addons themselves. My though would rather go to either sticky brakes, brake axis sensitivity setting or nullzone or maybe fsuipc.

I usually taxi at around 25kt on long straight taxiways, 10 knot or less on sharp turns and decelerate at a rate of 1 or 2 knots per seconds max with the brakes (which seems to me way sufficient when anticipating correctly).

On landing, I had one case of overheating when I started to manually brake at 70kts (and only on one side) which means than I brakes non symmatrically and too strong on one side.

Not feeling the acceleration forces makes it quite difficult to apply correct amount of brakes, so the only clue we have is the speed decay rate.

I believe that most of the overheating issues may come from riding the brakes too hard or brakes axis setting not correctly set.