Brakes, First time off the runway in years.... Options

[BDoney]

Second time in a row now to boot, under identical conditions (Saved AS weather)

Not exactly sure what the problem was, just landed KMKE rwy 01L under the following:

KMKE 160352Z 02006KT 10SM SCT022 M02/M05 A3031 RMK AO2 SLP273 T10171050

I share the wx because I can only assume this has something to do with the reduced braking action simulation you've introduced.

Here is what I saw:

Flaps 28, ENG HYD pumps HI, AUX and TRANS PUMPS on, anti-skid armed.

Normal touchdown, right on target, speedbrakes deployed normally, and I went into reverse thrust as the nose wheel settled. At 80kts, engines to idle, slowing through 60kts, manual braking....but there was no braking action at all.

As I applied the brakes, I saw the brake accumulator gauge briefly reduce as it should, but then immediately return to full. "Pumping" the brakes, I could get the gauge to "bounce" a bit, but braking would only last a split second, then nothing again.

NOTE: Brakes worked just fine on departure, so I'm relatively certain this isn't a hardware/assignment issue.

Any ideas ?

[kack911]

Hi Brian,

The next time it occurs, check your brake temps from the F/O's panel.

Perhaps you're braking too early, and getting them hot. Braking efficiency (effectiveness) is greatly reduced at high brake temps.

Also, are you using pedals? If you're using a joystick button that is essentially binary - either no brakes or max brakes with nothin in between - its even easier to over-temp the brakes.

Its the only thing I can think of...

Nick

[BDoney]

Nick,

Good idea, forgot to add that information as I did check the temps, after I'd coasted to a stop , and they read ~300 degrees.

I didn't start on the brakes until coming out of reverse, I'd say 70kts at the most.

[kack911]

The only other thing that I can think of is that the "M02" in the METAR you attached is erroneously causing NIL Braking Action without any runway contamination.

Was there any precip just prior to you landing, that might not have been reflected in the METAR?

I had a few occasions during testing where I noticed a reduction of braking action on a wet or contaminated runway with precip falling, but never on a bare/dry runway. (Excluding the time I cooked the brakes during a high-speed RTO...)

Perhaps Davide will have a better idea of whats going on...

Nick

[BDoney]

Nick,

I just loaded the sim to check again. Loaded up at the arrival airfield, again using the same AS wx, and sure enough, NIL braking.

There is some low(er) cloud cover, but no other visible precip in the area, not in the metar or the TAF in Activesky either.

This post has been edited by BDoney: 17/03/2007, 8:01

[BDoney]

Have done some more testing...

Went to KMKE, using the Clear weather theme, no 3rd party weather at all.

I then lowered the temps from 13C towards 0C, and sure enough, even with everything else still clear, and only changing temp, reaching 0C results in very poor to NIL braking action.

[Davide]

The reduced brake action is not related to temperature, but only to the surface condition which FS gives... if there is poor action it means that FS consider the runway covered with ice...

[BDoney]

Davide, I used the Clear weather theme in FS for my last tests.

No precipitation, no ice, just temps at 0C.

[Davide]

And brake temperature?

[BDoney]

Just started engines, so ambient temperature.

For the last testing, I just loaded it on the runway, started up, applied power to about 40kts, and tried the brakes.

I repeated this in 2 degree steps of temperature, from 13C until 0C(actually did it in degrees F, so 59F to 32F), from ~2C to 0C braking went from normal to nothing.

This post has been edited by BDoney: 17/03/2007, 11:13

[Davide]

Than it is possible that FS gives 'ice condition' just based on the temperature. If the brake reduction is annoying I will reduce the effect or make it optional from the LM.

[BDoney]

Well, it's not so much that it's annoying, Davide.

I mean, I went off the end of a 9700ft runway, twice, in dry, but cold, conditions.

I think the idea is absolutely brilliant, I just don't wanna go riding through the village so soon after landing.

I'll just fly in warmer weather for now, but I would think that forcing it to be tied to temperature AND a certain level of precipitation would be necessary to make it predictable....otherwise there's just no way to know, no precautions one can take...

[jack c]

I am having problems with the brakes to.The "BRAKES" text message on th elower left of the panel flight rapidly from
differential brakes" to "brakes" and so on BUT the braking is so ineffective. off the runway every time.

[Davide]

Be sure not to overheat the brakes...

[julien]

Hi pilots,

The only way I found to solve this problem is to switch off one engine after landing, it works fine you can use brakes normaly after that.
You have less thrust action on your brakes so the a/c is easier to slow down.
For sure this is an issue that Maddog should fix up.

Regards

Julien

This post has been edited by julien: 03/03/2010, 16:10

[Jared]

Single engine taxi in or out, just like powerbacks, are allowed, though, unless Dave can do some tuning up, FS will want to turn the airplane opposite to the operating engine as in if you taxi on 1 the airplane will turn right, if on 2 to the left, without correcting with the rudder. I've flown on Delta's MD-88s, RW, and in the flight manual I have both show me that MD08 could respond a bit better, my experience is you can't tell your on one engine as in the airplane will not turn with power increases and manual says that the airplane can taxi on idle thrust either single or twin engine taxi, so you ideally should be able to increase power till the airplane starts to move then back to idle and the plane will not speed up or down without another power application or brake applications.


I've also noticed that the power output, based on the manual which is valid for the -217A engine, in MD08 is low.

Manual:


"Do not apply more than 1.3 EPR during powerback. (Thrust
values in excess of 1.2 EPR should be limited to a momentary
power application to initiate powerback.)"


MD08 requires a min of 1.4 EPR to start rolling back

"Airplane response to thrust change is slow, particularly at high gross weights.
Idle thrust is adequate for taxiing under most conditions. A slightly higher
thrust setting is required to start taxiing. Allow time for aircraft response to
each thrust change.
To initiate taxi, release brakes, smoothly increase thrust to minimum required
for the airplane to roll forward (normally a maximum of 1.2 EPR) and reduce
thrust to idle. Do not start a turn until sufficient forward speed has been
attained to carry the airplane through the turn at idle thrust."

This post has been edited by Jared: 14/03/2010, 1:37

[julien]

Of course it works.
I often swith off one engine after landing as pilots do in real life. I agree with you regarding the fs limitation about that. But the maddog is quite better than the others adds ons for this fs issue. I cannot do the same with others A/C.
But with a heavy weight it's getting difficult with one engine to taxi on. Of course after landing your A/c weight is around 58967kg or lower, isn't it ?
So you can taxi with one engine, just be careful in the turns you need to anticipate the thrust action.

Julien

This post has been edited by julien: 26/03/2010, 9:26

[VulcanB2]

Hi,

The MD-82 has to be the best all-round on one engine. Rudder is not rediculously sensitive in flight, and taxis well on the ground.

It is easier to taxi light than heavy on one engine, but unless the two engines are placed on the centerline, there is no way to fix this. Of course, that then affects engine-out performance in flight.

Best regards,
Robin.