L HYD PRESS

[chaos]

Maybe I'm missing something here... I land on speed and in the touchdown zone on a long runway. I press the "W" key to apply (max) brakes. After a few seconds L HYD PRESS caution light comes on (without a Master Caution I might add). Is this normal system behaviour? I doubt it. Hence I end up in the grass at the other end :-)

 

I should be able to apply max. braking under normal conditions.

Edited October 13, 2010 by chaos

[power5]

I usually land around 170ias with full Speed brakes not too far past zone. Or at least I think I do. Maybe I am going faster than I think. Will have to watch closer I guess.

[159th_Viper]

I usually land around 170ias with full Speed brakes not too far past zone. Or at least I think I do. Maybe I am going faster than I think. Will have to watch closer I guess.

 

Waaaayyy too fast :)

[Steve Davies]

I usually land around 170ias with full Speed brakes not too far past zone. Or at least I think I do. Maybe I am going faster than I think. Will have to watch closer I guess.

 

You should try using AoA to land (reference the indexer on the left of the HUD).

 

With the blue/ green AoA indexer doughnut lit, I am usually showing about 119 KIAS over the threshold when clean (no external stores) and c.2,000 lbs of gas remaining.

 

The manual recommends 135 KIAS over the threshold, but I don't believe it indicates AUW for that airspeed, and that seems a bit fast to me.

 

Whatever, 170 KIAS is way too fast!

[Steve Davies]

Sorry, Viper, I know it looks like I am following you around on the boards today, but I promise it's not deliberate!

[159th_Viper]

Sorry, Viper, I know it looks like I am following you around on the boards today, but I promise it's not deliberate!

 

Lol no bother - your expertise is more than welcomed :)

[chaos]

I started on the runway, engines idle. Applied max. brakes and pressure remains steady. Took off and returned to land. During the roll-out phase I get a Master Caution (disregard my previous comment) upon applying maximum braking (W key). L HYD gauge shows 0.

 

According the A-10A manual; If L HYD fails, the R HYD system should take over and provide hydraulic pressure for braking (albeit without anti-skid). If that fails, there's enough pressure in the accumulator to bring the A/C to a full stop.

 

I can only assume this is a beta-software issue....

[sobek]

According the A-10A manual; If L HYD fails, the R HYD system should take over and provide hydraulic pressure for braking (albeit without anti-skid). If that fails, there's enough pressure in the accumulator to bring the A/C to a full stop.

 

I can only assume this is a beta-software issue....

 

Yes and no...

 

The anti skid seems to work like a regulated bypass that takes pressure off the brakes so you don't skid (if i understood correctly). If you apply max brakes, this bypass reroutes a lot of hydraulic fluid so the pressure doesn't build up on the brakes too much, it seems it can reroute more fluid than the left pump alone supplies to keep the pressure up.

 

So you see, the system is perfectly modelled, if you use the keyboard you just lack the ability to control the brakes properly. Will have to be looked into.

[MrYenko]

If I had to guess I'd say that at idle the engine isn't providing enough energy to run the hydraulic pump hard enough to counteract the hydraulic load of the brakes in use.

 

Engine driven hydraulic pumps are sized to provide full rated flow and pressure at or below engine idle RPM, for example, the most hydraulics-intensive phase of flight is approach, IE: you have all the primary flight controls moving about, flap extension, gear extension, etc, etc, all while the engines are at or only slightly above flight idle.

 

Also, brakes use a very small amount of fluid to do their work. Essentially, the brake is already filled with hydraulic fluid, it simply needs to be exposed to pressure in order to clamp the brake disc. On most systems, the brakes aren't eve exposed to full system pressure, but are exposed to a reduced pressure supplied from a pressure-check valve.

 

This doesn't answer the question about he simulation, merely provides some background.

 

Also, anti-skid does NOT equal automotive anti-lock. As mentioned, aviation anti-skid is light years more advanced than ABS. Correct use of either system, however, is to use the amount of brake pressure desired, with no brake pumping. ABS is pumping far faster and more accurately than any human ever could, and anti-skid systems work best with smooth, even control inputs.

[Scabbers]

sobek is the caution modeled to show in different colors?

[nscode]

It all depends on the aircraft. Pump them on the MiG-29 during a no chute landing, and you get fire! (there were some pictures of the results here a long time ago..)

[Steve Davies]

sobek is the caution modeled to show in different colors?

 

Scabbers

 

The caution panel is NVG compatible, so all the captions are now a greeny blue and there is no provision for colours to denote caution/warning severity.

[mvsgas]

This is not taken from any technical manual, only study material. Also this may not represent the actual anti skid operation of the A-10C or the DCS A-10C. I just taught it explain some things.

MLG brakes is held in place by the axle nut when wheel is installed. The multiple-disc, self adjusting type brake consist of the housing, steel rotor and stators disk, pressure plate, torque tube, back plate, hydraulic pistons, self- adjusting return spring and bleed valves. The brake system is bolted together. The housing incorporates 7 hydraulic pistons assemblies.

 

Normal brake system pressure, when full left and right brake/rudder pedals are applied, is 2600 psi minimum supplied by the left hydraulic system; the maximum differential pressure between brakes is 200 psi. The brake system incorporates anti-spin braking, which stops the main wheels rotation during retraction before the wheel contact the anti-rotation snubbers. A skid control feature is provided in the normal brake system to prevent wheel skids due to excessive braking. The brake system consist of normal brake system, emergency and antiskid system.

 

Anti skid

The anti skid system is a modular wheel skid control system that proportionately reduces the amount of the left hydraulic system pressure suplied to both MLG brakes when eather main wheel begins to skid.

The system is power by 28 volts direct current (VDC) from the auxiliary essential bus. An anti skid wheel speed transducer (mounted in axle of each main shock strut) and a drive cap( mounted on each main wheel) operate together to detect skids. When either wheel decelerates at a rate above 25 feet per second, the anti-skid control unit sends a brake pressure dump command signal to the anti-skid control valve, and the level of hydraulic pressure applied to both brakes is reduced in equal proportion. This allows the speed of the slower wheel to increase.

 

The skid control circuit in the anti-skid system are operational at aircraft speeds from 144 knots down to 10 knots. With the landing gear down, the skid control circuits are inoperative if the anti-skid system is not manually engage, a system fail-safe malfunction occurs, aircraft weight is not on the wheels, or the aircraft speed is less than 10 knots. The ANTI-SKID caution indicator light on the caution annunciator panel comes on green to indicate when the system is disengaged.

[Scabbers]

it wouldnt show on the master caution as that would be nvg coded. but on the cdu it would show on the acaws history if that software is enabled. I do not know if it is ported to the A-10. I know there are other aircraft using this.

[mvsgas]

Normal braking

The normal brake system incorporates manual differential braking in which the amount of hydraulic pressure applied to each MLG brake is determined by angular movement of the respective pedal and applied pedal force. Each brake pedal is mechanically connected to a dual-power brake valve by means of cranks, push rods, ans cable assemblies to actuate the dual-power brake valve, which then ports metered hydraulic pressure from the landing gera down line to the anti-skid control valve. The pressure is directed through brake shuttle valve to the brake. In the event of loss of left hydraulic system or alternating current power, or if the LAND GEAR circuit breaker on the essential circuit breaker panel opens, normal manual braking cannot be accomplished. The normal brake system also incorporates anti-spin braking, which prevents spinning of the main wheel during retraction. During takeoff, with the landing gear handle in the up position, the dual power brakes valve meters 300 to 1300 psi landing gear up pressure to the brakes to stop the main wheels from spinning before they contact the anti-rotation snubbers

 

Emergency

The emergency brake system is provided in the event the normal brake system fails. The emergency brake systems is activated by first pulling the EMER BRAKE handle fully aft, and then depressing the rudder/brake pedals. The right hydraulic system supplies the emergency brake system, which has the same capabilities as the normal brake system, except anti-skid protection. The emergency brake system is fully independent of the normal brake system, except for the dual power brake valve, shuttle valve and brake assembly. If left hydraulic system pressure become available while emergency braking is selected, the emergency brake system still retains control of the brakes. Should the left and right hydraulic system fail, pressure is provided by the emergency brake accumulator. Actuation of the EMER BRAKE handle, which is directly connected to the emergency brake control valve by means of flexible push-pull cable, ports right hydraulic system pressure to the emergency brake system.

[Deadman]

Thanks Mvgas:thumbup:

[mvsgas]

Your welcome

[Ells228]

If you stand on the brakes (or keep finger on W) you can hear the tyres locking up and screech

[nightlynx]

Wow a lot more posts than I expected! I was coming in fast and until I posted this initial thread I didn't even know what the speed brake key was and I've still not tried landing with the speed brakes deployed. I am using a keyboard and it feels, to me, like the plane does not want to stop. It's like I'm skidding without any noise even though I'm not and I have anti-skid enabled I've thought several times that I would run off the end of the runway.

[Echonomix]

if you guys are having a hard time stopping the plane during landing it is most likely a combination of things:

 

1. What speed are you landing at, what is your approach speed?

*most of the time you fly the approach and land at just above stall speed, which is generally 110-130 knots in the warthog (correct me if I'm wrong please)

 

2. Are you using any air brake on final and after touch down + flaps?

*I've heard some say that 30-40% is about right on final and of course full air brake after touch down

 

3. Are you holding the nose up on the roll out to allow the plane's wings/flaps to also act as air brakes?

*I'm not sure if this is a correct thing to do in the a-10, but the thunderbird pilots do this on landing in the f-16. Generally you want as much drag as possible once the main landing gear have touched the ground.

 

4. And last, use the wheel brake as discussed so far.

 

Speed and weight are a huge factor on how much runway is required. If any of that info I listed is wrong, please correct. I don't want to be giving out bad info :)