Tyres/brake temperature simulation

[Hardy Heinlin]

The factors which affect temperature seem to be endless 

It's also known that the tyres get very hot simply by taxying long distances at high weights due to the flexing of the tyre (I don't know how much this affects the tyre pressures, though).

Next we have to programme no wheel well fire indications on really windy days... The flames are blown away from the fuselage and not up into the wheel wells where the overheat detectors are.... assuming there are flames...

https://www.youtube.com/watch?v=qc_v6tXsv6g

Phil, you mean remolded tires? Are they allowed in aviation?

Retreaded tyres are the norm.  In theory, this can be done up to 10 times.

In my youth I often used retreated tires on my car. One day a tire exploded on the highway at 90 knots :-)

[Britjet]

V naughty Hardy! in the UK we have a 60kt limit on the "motorways".
(I always have trouble with the conversion though, as my speedo only does mph.)

Peter

[G-CIVA]

Hi All,

10.0.7 Beta 9

I have noticed over the last couple of flights that the BTMS is now showing very hot brake conditions during taxi before take off & after landing, I'll use my flight today as an illustration as it the parameters were not in the extreme at all:

Taxi at VTBS (BKK) in a GE powered 400F was from the NW Cargo Ramp for RWY01R & 17 mins, the TOW was only approx. 220t & the ambient temp at BKK was 27'C.  On releasing the Park Brake for the taxi after the push she rolled forward ably assisted by a 6kt tailwind that was to be a 6 knot headwind on RWY01R for take off.

The taxi was simple, straight ahead then one 90' left turn, pass the terminal complex to the South then turn right 90' to parallel the departure RWY before a final 90' left turn to line up.

In the taxi I applied no thrust whatsoever, I allowed the speed to increase to 20 kts before applying the toe brakes to reduce back to 10-15 kts.  The 90' turns were made at 5-10kts, braking was used to slow to this speed BEFORE commencing the turn.  With the turns & the increases in speed I used the brakes on seven occasions.

I did not ride the brakes, each application was as smooth as I could make it in one continuous application to the desired speed before releasing the brakes again.

So just to recap, aircraft at 220t, OAT 27'C, seven smooth applications of brakes ...

I was watching the GEAR Page on the Lower EICAS & the BTMS recorded a peak of '4' as I commenced the final application of brake before the final 90' left turn to line up on the RWY.

Arrival into ZSPD (PVG) was on to RWY35L into an headwind of 12 kts at a landing weight of 195.4t with Flap 25 & a VREF of 131kts, the OAT was +5'C & the RWY was wet, I used Autobrake 2 & partial reverse down to 80 kts.

As I passed through 60 kts I observed the BTMS showing '1' & I applied manual braking & gently slowed to 12kts taking the first rapid exit, I made one 270' turn & 1 90' turn onto stand & had to apply braking once to slow the now very light aircraft down as it wanted to accelerate briskly.  Taxi in time was seven minutes.

Approaching the final 90' right turn onto stand I slowed the aircraft to 5 kts & the 'BRAKE TEMP' EICAS Message appeared, the BTMS was recording '6'.

Appreciate I have absolutely no real world experience but does this brake temperature behaviour seem a little overly 'keen' to the initiated?

All the best

Steve

[Hardy Heinlin]

Perhaps the heat generation at taxi speeds should be a bit lower. Landing and RTO seems OK.


|-|ardy

[G-CIVA]

Perhaps the heat generation at taxi speeds should be a bit lower. Landing and RTO seems OK.

Hardy,

I'll just add that prior to any 'tampering' with the brakes during the 10.0.7 Beta process I was seeing the BTMS regularly create brake temperatures during landings & these rarely went above 2-3 unless the runway was short & the aircraft was heavy & the ambient conditions were really hot; I never ever saw the BTMS indicate activity anything like what I am seeing now due to my taxi in/out activities.

Despite what many who have been a passenger in a car/at WorldFlight with me might think I do not 'drive' while wearing lead diving boots! 

I am just a 'desktop PC pilot' with a yoke & pedals running a main & client on the same PC to two different monitors.  Could the lack of BTMS indications discussed earlier up this thread be part of a deeper issue buried inside one of the many additional 'clients' across a multiple PC network required to run a full sized sim? (just thinking out loud).

Thanks for looking into it.

Steve

[Phil Bunch]

Phil, you mean remolded tires? Are they allowed in aviation?

Retreaded tyres are the norm.  In theory, this can be done up to 10 times.

Some years ago, my brother took me on an informal walking tour of the primary jet base for the major US airline he worked for.  We walked past a large hangar where a large number of failed tires were stacked, waiting to be rebuilt.  We noted that most of them appeared to be retreads, and my brother said that most airliner tires are now rebuilt (aka retreads).  I guess it's not too important since they usually blow up one at a time and that must not be too much of a risk.   Good thing airliners have lots of tires!  Still, I suspect most passengers would prefer that only new tires be used!

[Hardy Heinlin]

Steve, there is no fault. I'm just tuning the brake heat (in the betas), to get similar results like in Peter's BA sim.


|-|ardy

[Avi]

Well,
If we want to increase realism here is another thing to think about.
I noticed that when all wheels on one side are deflated, the PFD still shows 0 roll degrees. Also, when all wheels are deflated, maybe we should also see some pitch up.

Cheers,

[Hardy Heinlin]

By how much? I think the gear strut compression will compensate a fraction of the height that is lost on the affected side.

That is a lot of work -- for the brain and for the programmer's typing hand, while the effect is rather microscopic and rare ... :-)


Cheers,

|-|ardy

[Will]

Also, this isn't a big deal, but accelerating to VR and taking off with all the tires blown is fairly easy. Acceleration is brisk, etc. Any ideas if the real aircraft would perform equally well on the takeoff roll with disintegrated tires?

[Hardy Heinlin]

After V1 all rubber will have disappeared probably.

[emerydc8]

After V1 all rubber will have disappeared probably.

Maybe some even decides to ride in the wing from Incheon to Anchorage.

https://drive.google.com/file/d/0B-WRh0Hf7VdZVWFkQzRQV2NfODg/view?usp=sharing

https://drive.google.com/file/d/0B-WRh0Hf7VdZNVlieUtiNFExTzg/view?usp=sharing

https://drive.google.com/file/d/0B-WRh0Hf7VdZYlN3d3ZlakRRZk0/view?usp=sharing

https://drive.google.com/file/d/0B-WRh0Hf7VdZVlkxcTdhS2RJc2M/view?usp=sharing

[Hardy Heinlin]

Braking at taxi speeds now generates less heat in version 10.0.7-beta10:

http://aerowinx.com/board/index.php?topic=3388.msg34312#msg34312

[John H Watson]

I noticed that when all wheels on one side are deflated, the PFD still shows 0 roll degrees.

It's certainly an interesting mental exercise computing the tilt. I estimate you would lose about 11 inches of hight on the bogeys with tyres completely shredded and the wheel rims sitting on the tarmac (not just deflated tyres). From outer bogey strut to outer strut, the distance is 36 feet 1 inches, but the pivot point may not be the outer strut, but a point between the two good struts. Also, the computations involve 3 dimensions because the pivot line involves the nose wheel.

Wild guess... 1.5~2 degrees tilt on the PFD 

[Hardy Heinlin]

What about the strut compression in your formula? A part of the opposite weight sits on the nose wheel, relieving a bit on the low side, so that strut expansion on the low side has less work to do to keep the low wing up.

[Britjet]

I'm not sure if I can fail all the tyres on one side in the sim but I can have a go this weekend..
Peter

[cagarini]

I'm not sure if I can fail all the tyres on one side in the sim but I can have a go this weekend..
Peter

You certainly have GREAT weekends Peter.... :-)

Now, we've always been great friends, since the old times, remember Peter ?

Can I go with you ?

[Britjet]

It's a dirty job, José, but somebody has to do it..;-)
Peter

[cagarini]

It would be great to have (not me... I don't even know how to properly start the 744 yet.... ) check-rides through the Net with you Peter.

I believe the "Instructor Station" can be remotely controlled, so, one could imagine a scenario where the aircraft starts from a given SITU and some check pilot operates the "Malfunctions" and "Weather" pages to create nice surprises for the PSX crew :-)

[Britjet]

An interesting thought, José..
I might experiment on my "minions"...
Peter