APU, Hydraulics, Elevator & Rudder

[Chief Instructor]

Hi,

 

I have a question, or three questions in fact...

 

Firstly, the flight manual states that the APU not only has its electrical generators but it also has a hydraulics pump. However, when the apu is running, (regardless of whether or not the APU electrical generator is engaged) the is no indication of hydraulic pressure in either of the two main systems. Is this correct and if so, is the APU Hyd system modelled? If it is, how do you utilise the Hyd output?

 

Secondly, with a cold start and no systems active (not even battery turned on) the rudders and elevators still move in response to stick and pedal movements. Without any form of hydraulic power, is this possible or correct? I understand from the manual that the rudders will revert to direct cable actuation in the event of a complete actuator failure, so that could explain the rudder movement. But... There is no mention that I can see of a similar reversion for the elevators. I guess there may be a direct cable linkage to the control column, but it is not mentioned and it seems less likely to me. Does anyone know the answer, or is it simply a bug in the systems modelling?

 

One last thing... Why am I able to fire my cannon on the ground even though the MFCD states that it is 'ground safe'? Is this another BETA issue?

 

Whatever though, this has go to be the most trully accomplished flight simulator ever produced, even at this stage in the development. Certainly outside of the commercial simulator world. :thumbup:

 

Best wishes to all!

 

Luke

Edited December 10, 2010 by Chief Instructor

[Headspace]

This probably doesn't answer your question with regard to what happens when the entire system is powered down, but for the record, Manual Reversion gives you direct elevator and rudder control (through the linkages). Aileron control reverts to the trim tabs on those.

[Snoopy]

Tha APU can provide hydraulic power but only to one system at a time and has to br manually selected by the crew chief (or whoever is doing maintenance).

[Weaponz248]

Remember the A-10 can fly without hydro, so the flight controls can move without hydro. As for the Gun I would need to know more or even see a track to see what config you had the pit switches in. It is possible to make the gun fire on the ground if you know what to do.

[Snoopy]

There is a way but I don't recall the exact procedures....

Edited December 11, 2010 by Snoopy

[Cali]

Tha APU can provide hydraulic power but only to one system at a time and has to br manually selected by the crew chief (or whoever is doing maintenance).

 

It's been a long time since I worked the A-10, but the lever is under F45 or somewhere close to that panel right? I know it's near the APU exhaust on the underside of the tail.

[Snoopy]

It's been a long time since I worked the A-10, but the lever is under F45 or somewhere close to that panel right? I know it's near the APU exhaust on the underside of the tail.

 

Yup...don't remember the exact pnl number but that's close...

[BlueRidgeDx]

DCS probably modeled the APU manual transfer valve in the STOWED/FLT position, which means its not powering either hydraulic system.

[Snoopy]

DCS probably modeled the APU manual transfer valve in the STOWED/FLT position, which means its not powering either hydraulic system.

 

 

I would hope so otherwise we'd be flying with the pnl open since you can't close it with the handle in any other position:thumbup:

[Cali]

Yup...don't remember the exact pnl number but that's close...

 

Old age is catching up to me....has been for years.

Edited December 11, 2010 by Cali

[BlueRidgeDx]

I would hope so otherwise we'd be flying with the pnl open since you can't close it with the handle in any other position:thumbup:

 

Bah! In the civvy world, I've sent lots of jets flying fly with stuff open/missing courtesy of the CDL! Speed tape and/or fuel burn penalties will fix anything! :doh:

 

But seriously, I didn't see an answer to the hyd part of the OP's question, hence my comment. I didn't know you couldn't close the panel.

[robmlufc]

Rigger tool kit - Speed tape, hammer, GS

[Scabbers]

fyi the hydraulic system provides pressure to drive the actuators. not power ;)

[Scabbers]

Bah! In the civvy world, I've sent lots of jets flying fly with stuff open/missing courtesy of the CDL! Speed tape and/or fuel burn penalties will fix anything! :doh:

 

But seriously, I didn't see an answer to the hyd part of the OP's question, hence my comment. I didn't know you couldn't close the panel.

 

The A-10 flight controls are hydraulic assist. Meaning the controls will function with no hydraulics through the mechanical linkages as posted earlier. :smilewink:

[BlueRidgeDx]

1) FYI, that's not what the OP asked. The question was:

 

...the flight manual states that the APU...has a hydraulics pump. However, when the apu is running...the[re] is no indication of hydraulic pressure in either of the two main systems. Is this correct and if so, is the APU Hyd system modelled? If it is, how do you utilise the Hyd output?

 

That question was not directly answered, so I addressed it:

 

DCS presumably models the APU hydraulic system with the Manual Transfer Valve control handle in the STOWED/FLT position, resulting in no hydraulic "power" to either (L/R) system.

 

2) The word "power" is appropriate when speaking about hydraulic systems. Have a gander in any maintenance manual or Dash-1; the A-10 is no exception.

 

3) You're only 2/3 correct. Given the stated conditions - an A-10 on the ground without hyd power - the ailerons will not operate, and the stick will be locked in roll.

 

You must manually select MAN REVERSION in order to free the stick in roll, and upon doing so, you only control the aileron tab. The aileron itself will not move unless there is enough airflow over the tab in order to "fly" the aileron to the commanded position.

Edited December 12, 2010 by BlueRidgeDx

[Yskonyn]

Interesting, this!

If I understand correctly we have only talked about maintenance actions on the ground so far, but what happens if you loose both hydraulic systems in the air? I'm sure it cant be possible that the control stick stays locked in roll, can it?

How would the pilot save his butt then, ejecting? Is there no backup ie redundancy like on passenger jets?

[Frederf]

No, that's MRFCS for you. You fly the airplane by cable linkages connected to the trim tabs. Elevator is electric instead of cables. This is as hydraulic pressure drops below a threshold.

[sobek]

fyi the hydraulic system provides pressure to drive the actuators. not power ;)

 

Sure it does. Power is pressure times displaced volume over time.

[BlueRidgeDx]

Interesting, this!

If I understand correctly we have only talked about maintenance actions on the ground so far, but what happens if you loose both hydraulic systems in the air? I'm sure it cant be possible that the control stick stays locked in roll, can it?

How would the pilot save his butt then, ejecting? Is there no backup ie redundancy like on passenger jets?

 

When you lose all hydraulics, the transition to pitch and yaw MRFCS is automatic and immediate. However, in order to enter roll MRFCS, you must manually select MAN REVERSION, and wait several seconds for the tab shifters to work, and for the ailerons to float.

 

Until MAN REVERSION is selected, the stick will be essentially non-movable in roll, since the pushrods/pulleys will be acting directly upon the actuators which have no hydraulic power.

[Yskonyn]

Right, I misunderstood then. I thought the MAN REVERSION switch was only a maintenance operable switch e.g. while on the ground. Sounded a bit weird there and then already, so I am glad I asked. ;)

 

Thanks!

[Snoopy]

No, that's MRFCS for you. You fly the airplane by cable linkages connected to the trim tabs. Elevator is electric instead of cables. This is as hydraulic pressure drops below a threshold.

 

That's not completely correct. The elevators have cables that run from the white area to the electromechanical actuators (two, one for each elevator). if one actuator fails their is a torque shaft that connects both so one actuator can control them. The torque shaft is also if one elevator binds the shaft will break so you still have total control of at least one elevator.