Tyres/brake temperature simulation

[Blake H]

Hi Hardy,

Just enquiring about implementing tyre/brake temperature simulation into PSX

Would be nice to experience tyres blowing their thermal plug, if too hot.
Or if you ride the brakes the potential braking energy is reduced. Or from a rejected takes-off and heavy use of brakes after landing.

In addition a blown tire list added in malfunctions, failures.


Any chance for implementation?


Blake Hauswirth

[Hardy Heinlin]

Hi Blake,

that's already implemented.

Available in PS since 1997.


Cheers,

|-|ardy

[Will]

Hello Blake,

Load the aircraft up nice and heavy, start a takeoff roll, and then abort just prior to V1. Come to a stop with max braking.

After you stop, choose the "Gear" synoptic on the lower EICAS and watch the fireworks. Note that it takes a while for heat to make it from the brake disks to the sensors, so there's a bit of a lag.

[Blake H]

Does the brake temperature indicator increase on the synophic after a RTO.

[Hardy Heinlin]

Of course.

[Gary Oliver]

Hardy,

I haven't ever seen the Brake Temp show anything other than zero in our Sim.

Could there be an issue with either externally injected brakes or network client displays at all?  I will have a look to see if they show up on the server next time I am out there.

Cheers
Gary

[Hardy Heinlin]

You need to wait for several minutes. You can use time acceleration.

Note that this is an exponential function. A few knots more for a few seconds more can make a big difference.

Land at 150 kt groundspeed and set max brakes. After the full stop turn around and start a take-off roll. Reject at 130 kt with max brakes. This should raise your temps to 8 or 9 after some minutes. At 9 your tires will burst.

The heat distribution to the sensors is really slow. That's intentional.


Cheers,

|-|ardy


Here's some more technical background:

http://aerowinx.com/board/index.php?topic=1763.0

[Britjet]

I did a bit of testing on this.
To be honest, from what I saw it is too conservative.
One of my tests was a 396T takeoff from Johannesburg at ISA +25 with RTO at 156kts (GS 178) and no reverse.
The Brake Cooling schedule in the QRH gives an expected brake index of about 75 Million Foot Pounds. (It doesn't get worse than that..)
This gives a BTMS reading of 7 or above in the schedule - well into the fuse plug melt zone.
I tested this on PSX and could not achieve higher than 4 BTMS, even waiting for 15 minutes. It peaked at abot 9 minutes.
As things stand in PSX there will never be an instance where one RTO or MAX braking landing will give a BRAKE TEMP indication, which rather negates any training value that could come of it. It does happen!

I have seen BTMS readings of 4 at the gate following just one landing after a long (cooling) flight. It would also be quite normal to see a reading or at least 1 while taxying in after a normal landing, and if the pilot was heavy or asymmetric on the brakes, even at moderate landing weights,  a 2, or a 3 by the time we got to the ramp was quite common.

The BTMS should also start to register into the 1's and 2's a but sooner, I think?

I am in the sim for several hours at the weekend and I will make it a point to do some RTOs!

HTH

Peter
PS - just an anecdote, but I remember when we did some "return to departure" airfield training at Mexico City in the sim a while back - the Capt concerned decided to return overweight after takeoff at about 320T (cold brakes) and then took it upon himself to try and make a turnoff rather than the full length. We went off for a cup of tea during which time he ruefully admitted he "probably shouldn't have tried the turnoff, but it turned out OK".
When we got back to the sim all the tires were flat!

[Hardy Heinlin]

Hi Peter,

so you think the time until the temp peak, that is, ca. 10 minutes, is OK?

Just the temp peak is too low?

The fine-tuning of this stuff is highly critical due to multiple, exponential interdependencies; your anecdote shows it: In your sim, after a 320T RTO, you got the 9 (tire burst) after a tea break (10+ minutes?) -- whereas in your 396T Johannesburg test you expect 7 as per the QRH, i.e. a higher weight, higher energy, but lower temps.


Cheers,

|-|ardy

[Britjet]

Yes, I know - the anecdote and the JNB don't quite agree, do they? It was quite funny though!

Basically I think that to mimic data that is in the Brake Cooling schedule is the way to go - for training purposes it would then mirror the trainees expectations. I think it warms up in significantly less than the 15 minutes that are mentioned in the schedule, however.

To answer your question, I think the time for the increase should be less, and the temp peak should be higher.
But I have a look at it hopefully tomorrow..

Peter

[Hardy Heinlin]

So I leave the timing as is. It's less than 15 minutes.

I'll just increase the peak temp coefficient.

It's really a sensitive model because the temp range is so large, and because the heat distribution is so slow, while the energy generation, however, just takes some seconds.

Imagine, when you apply max brake power at high weights ...

It just takes ca. 15 seconds from 100 kt to 0 kt.

It takes ca. 17 seconds from 110 kt to 0 kt.

Just two seconds more and the target temp may be 20% higher. -- Every second has a massive influence on the target temperature.

And while the sensed temp rises to the target temp in ca. 10 minutes, there is another parameter that influences the model: When the aircraft has stopped, the target temp decreases. During the braking it may have been at 9 or higher. But before the sensed temp reaches 9, the target temp may have decreased below 9 again, and so the sensed temp will never reach the original target peak. This makes the model even more sensitive to small changes on the time axis. (The target temp drops much faster when the aircraft is in flight with the gear down.)


|-|ardy

[Britjet]

Fine. Let me try to get some example figures tomorrow :-)
We will be doing a lot of landings so that should also give an idea of build-up..

Peter

[Hardy Heinlin]

I forgot to mention the third influence that makes the model ultra sensitive: It's not just the time nuances, not just the speed nuances, but also the nuances in the brake pressure. You have 5 autobrake settings. In a certain test scenario, when the autobrakes are set to MAX, you want to see temperatures above 7. But when the autobrakes are set to 4 or 3, you want to see temperatures below 5. A small step for the brake pressure, a giant leap for the temperature.

So, just a bit more brake pressure, and the temp is supposed to "jump" from 4 to 7+

I'm sure in the next PSX update some people will complain about too high a brake temp at normal brake settings, and complain about too low a brake temp at high brake settings ... :-)


|-|ardy

[Britjet]

Yes, it is complicated..1/2 MV squared etc..

I think that one underlying thing is that it should (make that might ) be possible to emulate the brake schedule chart.
That does give figures for the different brake settings on landing.

I assume that we still deal severely with any complainers? :-)

Peter

[Frans Spruit]

Hi Peter,

I have lots of "friends" at the Royal Military Academy not far from you 

Cheers,

Frans Spruit

[Hardy Heinlin]

I think that one underlying thing is that it should (make that might ) be possible to emulate the brake schedule chart.

It sounds so easy ... :-)

It's easy to draw a chart!

But a chart is not the same as a simulator that calculates the results shown on that chart :-)

Especially if the simulator has countless dynamic variables running in a frame rate driven real-time system ...


|-|ardy

[Hardy Heinlin]

Wheel brake temperature maximum peak coefficient is now increased in PSX 10.0.7-beta6:

http://aerowinx.com/board/index.php?topic=3388.0

[Britjet]

Hi Frans,

I think I may have met some of them on manoeuvres in the nearby forest!

Peter

[emerydc8]

Hi Hardy,

[Nevermind -- I was still using Beta 3 on this one. Will try Beta 6 now and compare].

I test drove Beta 6 with a landing at 391T. I used max autobrakes and max reverse. The flaps 25 ref was 190. OAT 27C. This was the ER freighter (VQBGY). I let it autoland and stop on the runway without touching the brakes, so the brakes were applied while I observed the following brake temp. The times are from when the airraft came to a complete stop:

2 min.   -1
4 min.   -2
6 min.   -3
10 min  -2
20 min. -1
30 min  -0

If this was a classic, the airplane would have burnt to the ground in 30 minutes.

[ADDENDUM]: Tried the same scenario with Beta 6 (correctly) installed:

1 min. 30 sec.  - 1
3 min. 20 sec.   -2
5 min. 20 sec.   -3
7 min. 40 sec.   -4
9 min. 20 sec.   -5
11 min.             -6
12 min. 40 sec. -7
22 min. 50 sec. -6
Stayed at 6 at least 30 minutes after stopping aircraft.

[Hardy Heinlin]

Hi, thanks for the test. You mean the peak of 7 is too high for this scenario and the classic would catch fire at 7?



A note for everyone:

I just increased the peak temp maximum. I have not adjusted the cooling time for this modification yet. This modification in beta 6 is supposed to correctly model the energy generation during braking (involves braking time, brake pressure, groundspeed) and the maximum peak after ca. 10 minutes (+/- 3 minutes).



A question for everyone:

Does anybody know the tire pressure maximum that would lead to an explosion? Or is the fuse plug melt system always faster and reliable enough to prevent a tire explosion? (Temp dependent tire pressure modulation is not modeled yet; the pressure remains static as long as there is no hole in there.)

In the existing PS versions a tire deflates when the temp is in the 9 zone. I could add some more randomness and lower the "zone of risk" to 7.



Regards,

|-|ardy