A-10C Landing Gear Handle Baulking Pin

[CorporalCarrot]

Hi Guys,

 

I'm going to be making a start on my landing gear and flap control panel soon and I'm thinking about my landing gear selector level design and the A-10C features a baulk to prevent moving the gear from down to up with weight-on-wheels, unless the Downlock Solenoid Override Button has been pressed.  Looking at the DCS Bios documentation, is the downlock baulk or Weight-on-wheels signal accessible?  I can't find anything and would like to make my panel as faithful as possible, and this doesn't seem to have been asked previously on this panel?

 

Any ideas?

 

TIA,

 

Corporal Carrot

[crash test pilot]

Look in the control reference under external aircraft model, there are weight on wheels available.

[CorporalCarrot]

I don't see WoW in the external aircraft model for the A-10C?  All I see are a bunch of lights and the speedbrake positions...

[crash test pilot]

 

Last three points. Its intended for leds, but you can use the signal for whatever you want. It is just a logical high or low signal.

[CorporalCarrot]

Are you sure this is for the A-10C?  This is all that is listed under External Aircraft Model for me;

 

Control Reference: A-10C: External Aircraft Model

 (8/8 displayed)

Formation LightsA-10C/EXT_FORMATION_LIGHTS

Commands:

IntegerBufferServoOutput Integer Output: Formation Lights

void onExtFormationLightsChange(unsigned int newValue) {
    /* your code here */
}
DcsBios::IntegerBuffer extFormationLightsBuffer(0x12ce, 0xffff, 0, onExtFormationLightsChange);

no data yet

Left Position Light (red)A-10C/EXT_POSITION_LIGHT_LEFT

Commands:

LEDIntegerBuffer Integer Output: Left Position Light (red)

DcsBios::LED extPositionLightLeft(0x11bc, 0x0800, PIN);

no data yet

Left Speed BrakeA-10C/EXT_SPEED_BRAKE_LEFT

Commands:

IntegerBufferServoOutput Integer Output: Left Speed Brake

void onExtSpeedBrakeLeftChange(unsigned int newValue) {
    /* your code here */
}
DcsBios::IntegerBuffer extSpeedBrakeLeftBuffer(0x12cc, 0xffff, 0, onExtSpeedBrakeLeftChange);

no data yet

Left Strobe LightA-10C/EXT_STROBE_LEFT

Commands:

LEDIntegerBuffer Integer Output: Left Strobe Light

DcsBios::LED extStrobeLeft(0x11bc, 0x4000, PIN);

no data yet

Right Position Light (green)A-10C/EXT_POSITION_LIGHT_RIGHT

Commands:

LEDIntegerBuffer Integer Output: Right Position Light (green)

DcsBios::LED extPositionLightRight(0x11bc, 0x1000, PIN);

no data yet

Right Speed BrakeA-10C/EXT_SPEED_BRAKE_RIGHT

Commands:

IntegerBufferServoOutput Integer Output: Right Speed Brake

void onExtSpeedBrakeRightChange(unsigned int newValue) {
    /* your code here */
}
DcsBios::IntegerBuffer extSpeedBrakeRightBuffer(0x12ca, 0xffff, 0, onExtSpeedBrakeRightChange);

no data yet

Right Strobe LightA-10C/EXT_STROBE_RIGHT

Commands:

LEDIntegerBuffer Integer Output: Right Strobe Light

DcsBios::LED extStrobeRight(0x11bc, 0x8000, PIN);

no data yet

Tail Strobe LightA-10C/EXT_STROBE_TAIL

Commands:

LEDIntegerBuffer Integer Output: Tail Strobe Light

DcsBios::LED extStrobeTail(0x11bc, 0x2000, PIN);

no data yet

Scratch that.....  I 'updated' DCS-Bios several days ago by re-installing with the latest version of DCS Bios from Github, but I went to check plugins (to download another module) and I noticed that you update the modules from there..... FML

 

I see the WoW sensors now....

Edited February 18, 2021 by CorporalCarrot

[CorporalCarrot]

I was looking at doing something with the code, but I'm using a MEGA on that panel with plenty of spare pins, so I'll just use the LED outputs and a 74HC00 quad NAND gate to control the logic.  I'm planning on using a solenoid to baulk the landing gear handle, if I can find one that reasonably efficient (and not get hot).  I can just use a transistor and a FET to switch the solenoid (if the one I source doesn't have a logic level input).

 

Thanks Crash test pilot.

[DeadMeat]

Back when we came up with adding the WoW parameter to DCS-BIOS based on the gear animation state I used it to control the downlock solenoid on this Tornado landing gear switch. Around page 2 you can see this logic being applied to control the solenoid using a MOSFET.

If you prefer, you can skip the physical nand gate and do the logic in code to check for WoW being 0 for all wheels to trigger the solenoid.

[CorporalCarrot]

I'm also planning to use the downlock override button as part of the logic circuit.  Whilst the downlock override button will be connected to a pin on the arduino, to send the signal to the game via DCS BIOS, I'll also use signal to override the WoW logic and remove the baulk pin.  As the Arduino works by pulling the digital pin upto 5V and grounding it via the button, this logic is inverted if I take the 5V digital pin to the logic circuit (So 1 is 0V and 0 is 5V, if that makes sense).  This is the truth table;

 

The above table has 1 on the downlock overide being ACTIVE (i.e. pushed), where the actual d-lock signal is LOW. Working through the Karnaugh map, this results in a Boolean formula of OP = (RMLG x DLock') + (LMLG x DLock') + (NLG x Dlock')   - where the apostrophe indicates the inverse signal.  As previously mentioned, the d-lock signal is already inverted as a result of how the arduino pin works (grounding 5V makes it active), so we don't need to invert this signal after all!

 

As a logic circuit, using one 74HC00 quad NAND chip and one 74HC02 quad NOR chip (which I have kicking around) looks like this;

 

Clear as mud?!  I could dick around and do some of it in code, but I'd need to use two chips any way.

Edited February 19, 2021 by CorporalCarrot

[Nikolas_A]

You might want to check the manual before you over-complicate things. IIRC in the F-16 only one WOW switch is checked, might be the same in the A-10

[DeadMeat]

Yeah, pretty clear I guess. If you do it in code you can get by with just the MOSFET for controlling power to the solenoid like I described in the other thread.

Your Arduino can check for high/low state of a downlock override button directly on a digital pin and in code you just need to check that all WoW outputs from DCS-BIOS are 0.. But no matter - I think it'd be fun to see your solution with chips instead

 

Regarding which wheels to check WoW, "I'm told" that the A10 dash 1 mentions that WoW has to be off the "wheels" in plural to be able to move the landing gear handle up, so I guess it would be correct to check all wheels. The downlock override is mentioned to be electrically actuated - and there is no uplock on the handle other than having to pull it backwards first.

 

For the F16, again "I'm told" that the dash 1 states that WoW is only checked for left MLG for the gear handle downlock. The override is fully mechanical however. In addition the F16 has a solenoid held handle uplock - controlled by the down permission button on the handle. It is unclear however if the uplock can be overridden - might be that the downlock override does it.

 

On the Tornado lever I used, the downlock is defeated by solenoid or a fully mechanical override button above the handle. There is also a mechanical uplock unlocked by a small lever on the switch handle. Later versions of the lever may function differently.

[CorporalCarrot]

I work in the aviation industry as a Systems engineer, and have specialised in Civil Aviation Landing Gear for the last 15 years, but have done military aircraft too.  Most of the designs in 80's and 90's used 'black box' controllers for the different systems, and the landing gear extension and retraction system (LGERS) control units typically received signals from multiple proximity sensors to determine WoW, locked down, locked up etc.  The LGERS control unit would do all the logic, decide the position of the landing gear and control the hydraulic valves based on the position of the landing gear handle, with supplementary inputs from other systems (such as airspeed - to prevent landing gear extension in high speed).

 

I've never worked on the F-16, but I'm surprised to hear that the landing gear baulk only works from one gear, and that the baulk is mechanical!  I guess it would probably work with a combination of bellcranks and levers on the landing gear, and then use sleeved cable to the cockpit.  It'd be unlikely to use a sleeved cable on the landing gear itself, as it would be susceptible to damage (bird strike for example), although could be run on the aft side of the leg, but also would then need to flex on landing gear extension/retraction, which would then be probe to cyclic damage.  Overall, a mechanical link seems to be very bad design choice, as the weight involved with mechanical linkages etc. would be relatively large, compared with proximity sensors and electrical cables etc.  The F-16 was designed in the 70's and inductive proximity switches were available then, so I'm not sure why they weren't used?  I guess General Dynamics had their reasons!

 

Maybe my industrial design principles are bleeding though, but I like my design as the downlock overide is independent of the arduino, in case DCS bios crashes or something!  I guess it doesn't really matter!  

[Nikolas_A]

No, the lever is mechanically locked but electrically unlocked. When the LG is unweighted, a solenoid pulls the lock off and the lever can be moved up, raising the gear. The lever is locked again so the LG is not inadvertently deployed from high-G maneuvers. To lower it, the same solenoid is energized by a switch on the lever to unlock, or a mechanical plunger can unlock it if the solenoid fails.

[DeadMeat]

Agree Nikolas - that's more clear way to put it  Didn't mean to imply that there's a mechanical connection from the gear - I agree with carrot that would be a bad solution.

 

Also to be fair there's WoW sensors on all 3 F16 landing gear, but they're connected to different things. For example the right MLG sensor is among other things tied to the FCR, so a fault in that sensor could cause the FCR to transmit on the ground cooking the crew chief or inhibit it from transmitting in the air blinding you if the fault went the other way.

 

Not sure where the physical sensors sit, dash 1 just states that they are somehow connected to the strut compression (or so I'm told)

Edited February 19, 2021 by DeadMeat