Flap Control Units (FCUs)

[emerydc8]

Interesting. So, you ran the flaps down to 30 with hydraulics, then switched to alternate mode and took the pic?

[John H Watson]

Correct.

Here's a shot of the ouboard flap drive unit.

Outboard TE Flap Drive Motor

The angled green rod at the top left hand is the mechanical input from the Flap Input Actuator.  Unlike the last photo, you can clearly see the striped orange/black drive going in both directions to the (outoboard) flaps.

So the signal path is....

Flap Lever >> FCU >> (Electric) Flap Input Actuator >> linkages (to inboard/outboard flap drive units) >> hydraulic valve on drive motor >> hydraulic drive motor >> striped orange black torque tubes >> transmissions (convert rotary motion to linear motion) >> screwjacks (in wing canoes) which push the flaps out.

That light brown goop all over the wheel well is corrosion inhibitor... not oil 

[emerydc8]

Thanks!

That light brown goop all over is corrosion inhibitor oil ... not oil corrosion inhibitor.

[John H Watson]

Perhaps oil from leaky gear shock struts. I can't think any other source of oil on the aircraft centreline. If it were hydraulic fluid, I would expect more paint stripping/bubbling. Probably well overdue for a service and a wash.

[emerydc8]

When you say the alternate display was not available, do you mean that there was the basic scale (outline), just no solid white moving tape...  i.e. yellow "X"s instead?

I checked. He said he remembers the basic scale (outline) was there, but no flap position indication.

[Avi]

So the signal path is....

Flap Lever >> FCU >> (Electric) Flap Input Actuator >> linkages (to inboard/outboard flap drive units) >> hydraulic valve on drive motor >> hydraulic drive motor >> striped orange black torque tubes >> transmissions (convert rotary motion to linear motion) >> screwjacks (in wing canoes) which push the flaps out.

This is not 100% accurate 

The transmission doesn't convert a rotary motion to a linear motion. The transmission only changes the rotary motion direction (from a rotary motion along the width of the aircraft to a rotary motion along the length of the aircraft).
The transmission rotates a ball screw (or screwjack) via a universal. A ball screw nut on the ball screw converts the rotary motion to a linear motion.

Here is the rest of the description:
A gimbal assembly connects the flap carriage to the nut. The flap carriage also rides along the flap track which sets or controls the flaps angular. The (main) flap is connected to the flap carriage. The fore flap and the aft flap are connected to the (main) flap which "controls" their movement and position as it moves back or forth.

Cheers,

[John H Watson]

Correct. Avi must have been a "greaser" (engine/airframe engineer) in one of his previous lives 

I understood the principle... I just simplified things

[Avi]

Correct. Avi must have been a "greaser" (engine/airframe engineer) in one of his previous lives 

I wish...

I understood the principle... I just simplified things

I guessed it 

Here are very close up videos of the flaps in motion on the 747 and the 737. I bring the 737 video (which is soooooo not my aircraft) because you can see the orange-black torque tube rotates. Note the 737 has a different Flaps Power Package than the 747.

Cheers,

[Hardy Heinlin]

Hi experts,

there are multiple subjects in this discussion; I'm trying to make a summary ...


FCU power supplies

In PSX version 10.1 and earlier, the power distribution is modeled like this:

If AC 1L or AC 2L is powered:
• FCU L is powered
• TE outboard R position indication is powered
• TE inboard R position indication is powered

If AC 1R is powered:
• FCU C is powered

If AC 2R is powered:
• FCU R is powered
• TE outboard L position indication is powered
• TE inboard L position indication is powered

I don't think this requires a modification.


EGPWS

In PSX version 10.1 and earlier, the landing flap status in the EGPWS is set by the last sensed flap lever RVDT position being greater than 20, and this signal is provided by all three FCUs. Note: With landing flaps set, mode 2 uses 600 ft instead of 30 ft RA for the envelope minimum, mode 3 is inhibited, and mode 5 can be enabled. So I think not only mode 4 but also mode 5 will be inoperative when the EGPWS gets no landing flap status. -- I'll make two modifications: The actual inboard TE flap >= 25 position will provide the landing flap status to the EGPWS, and for this service FCU L or C must be powered; if both are not powered, the EGPWS receives no landing flap status.


High idle

In PSX version 10.1 and earlier, the landing flap status in the high idle criteria is set by the last sensed flap lever RVDT position being greater than 20. -- I'll modify it like this: The actual inboard TE flap >= 25 position will provide the landing flap status, and for this service FCU L must be powered for engines 1+4, FCU R for 2+3.


Continuous ignition

In PSX version 10.1 and earlier, in the ignition logic of each engine (around the relays R8297 and R7533) the flaps out status is set when any actual flap is out of up and FCU L or R is powered. -- I'm not sure if this requires a modification.


Hydraulic demand pumps

In PSX version 10.1 and earlier, for the one airline option: The flaps out of up status in flight is set when the last sensed flap lever RVDT position is greater than 0. For the other option: The flap in transit status is set when any actual TE flap is in transit. For both options, and for all engine models, FCU R must be powered for DEM 1, FCU L for DEM 4. -- I'm not sure if this requires a modification. Also I don't see why this should be valid for GE engines only.


Alternate flap position indication

I'll modify it so that it blanks completely when all three FCUs are not powered. It will not blank as long as any FCU is partially operative.


Cheers,

|-|ardy

[John H Watson]

Just a few comments/questions...

EGPWS The actual inboard TE flap >= 25 position will provide the landing flap status to the EGPWS, and for this service FCU L or C must be powered; if both are not powered, the EGPWS receives no landing flap status.

How will the EGPWS react to "no status"? Flaps in landing range or flaps not in landing range? As we've seen before, for a few systems, sometimes internal switches in Boeing wiring schematics are shown as simple switches but othertimes shown as voltage dividing circuits with transistors in them. Both require power to change state, but the no power default state can differ.  Pilot's manuals may partially resolve these contradictions.
My personal (beta) notes suggest that there may only be one FCU involved in the process on older (or perhaps unmodified older aircraft), but let's assume all aircraft are new ones 

High idle

See comments/question above regarding internal switch default state.

Continuous Ignition In PSX version 10.1 and earlier, in the ignition logic of each engine (around the relays R8297 and R7533) the flaps out status is set when any actual flap is out of up and FCU L or R is powered.

See above.

I have 3 variations regarding flap state in my manuals. One wiring schematic simply say "Flaps not retracted". Another wiring schematic suggests that only Group A L/E flaps are involved (27-51-04). I wonder if it's possible to disable only group A on the real aircraft, but have the rest of the flaps extend normally? My training notes offer a 3rd option: "Any time the flaps are out of zero detent (not stowed)" ... which might suggest the lever position (?).

In PSX version 10.1 and earlier, in the ignition logic of each engine (around the relays R8297 and R7533)

Looking at CF6 ignition diagrams (74-31-01/74-31-02/74-31-03/74-31-04), the input from the FCUs to the continuous ignition circuits is independent of the Continuous Ignition Relay R8297 (R8297 is controlled by the CONT IGN switch on P5).

There are actually two FCU-controlled relays. i.e. R7533 and R7532.
R7533 is controlled by the Right FCU. R7532 is controlled by the Left FCU. These two relays are powered by [P6 K25]. Relays R7533 and R7532 control "SINGLE CONT ENG X" and "DUAL CONT ENG X" relays for each of the 4 engines (8 relays altogether). Each relay pair is powered by their respective ENG X IGN 1 or 2 CBs on P6. The output of the single and dual relays goes to the overhead panel SINGLE/BOTH switch and then to the EECs. Do the CF6 manuals say that flap position-triggered continuous ignition can be dual or single (depending on the overhead panel selection)?
Anyway, I can explain this in more detail in private 

Alternate flap position indication

I'll modify it so that it blanks completely when all three FCUs are not powered. It will not blank as long as any FCU is partially operative.

Can you clarify what you mean by blank? In real world tests, when I pulled all the FCE Power Supply CBs (depowering all 3 FCU's), the Alternate Flap Display appeared. Unfortunately, because I pulled all of the FCE Power Supply CBs, the flap display was covered with lots of amber "X"s (all the position transmitters were inop).

Rgds
JHW

[Hardy Heinlin]

When the above systems get no flaps in landing range status, the systems immediately apply the other status which is: Flaps not in landing range status.

Looking at CF6 ignition diagrams (74-31-01/74-31-02/74-31-03/74-31-04), the input from the FCUs to the continuous ignition circuits is independent of the Continuous Ignition Relay R8297 (R8297 is controlled by the CONT IGN switch on P5).

There are actually two FCU-controlled relays. i.e. R7533 and R7532.
R7533 is controlled by the Right FCU. R7532 is controlled by the Left FCU. These two relays are powered by [P6 K25]. Relays R7533 and R7532 control "SINGLE CONT ENG X" and "DUAL CONT ENG X" relays for each of the 4 engines (8 relays altogether). Each relay pair is powered by their respective ENG X IGN 1 or 2 CBs on P6. The output of the single and dual relays goes to the overhead panel SINGLE/BOTH switch and then to the EECs.

Yes, that's all included already. PSX models the entire circuit diagrams, with all the relays ... R8297, R8331, R7533, R7532, R7634 etc., involving FCU L and R, and the CBs K25 etc. pp., and after this engine-model-independent part the branches of the logic tree get into the model specific circuit diagrams with all the model specific relays, CBs, selectors etc.

I just mentioned some sample relays to indicate on which page I am :-)

Can you clarify what you mean by blank? In real world tests, when I pulled all the FCE Power Supply CBs (depowering all 3 FCU's), the Alternate Flap Display appeared. Unfortunately, because I pulled all of the FCE Power Supply CBs, the flap display was covered with lots of amber "X"s (all the position transmitters were inop).

Actually, by "blank" I meant "completely blank". But if those QRH texts mean "blank with amber Xs" if the text reads "not available" or something like that, then I'll just insert those amber Xs.


Cheers,

|-|ardy

[John H Watson]

When the above systems get no flaps in landing range status, the systems immediately apply the other status which is: Flaps not in landing range status.

This seems to be the way the majority of diagrams depict the behaviour. My diagrams and Jon's manuals suggest that inboard TE flap position is used for flaps in landing range.

Also shown in the FCU internal diagram are the following data titles:
Flaps in Land (diagrams also suggest this is based on inboard TE flap position transmitters)
Flaps in Takeoff (ditto)
Flaps Extension Required (?) (ditto)
Inboard Flaps Retracted (ditto)
Flap Motion Required (ditto)
LE Group A Retracted/not retracted (based on Group LE flap position)

These signals are further processed to produce discrete outputs to other computers (No TE outboard flaps or other group LE flaps are mentioned).

Re "flaps in motion": this only needs to be based on inboard TE flap position. This FCU signal outputs to the #1 Hydim for #1 System Hydraulic Demand pump operation (The #1 Hyd Demand Pump supplements the hydraulics which power the inboard TE flaps).

The "flaps out of up" output signal processing seems to be a little harder to tie down (Does it use both the FCU "Inboard Flaps Retracted" signal and the "LE Group A Retracted" signal... and what happens when one is not available).

I can't remember what is modelled in PSX. For example, does the #1 Hydraulic Demand Pump run if (due to a failure) only the outboard TE flaps are capable of moving?

Cheers
JHW

[John H Watson]

If the inboard trailing edge flaps are affected:
CONTINUOUS IGNITION SWITCH. . . . . . . . . . . . . . . .ON
[Automatic continuous ignition may may be inoperative. Provides automatic approach idle.]

CF6 Ignition diagrams show FCUs L/R output "Flaps Not Retracted" (pin F6). My AOMs state TE flaps, but the QRH suggests inboard TE flaps (as do the wiring schematics). Approach idle is based on flaps in landing range (FCU pin D6), but also by the manual selection of continuous ignition. The QRH suggests that both continuous ignition and approach idle are referenced to the inboard trailing edge flaps.

Sorry if I've asked this before, but does PSX use inboard TE flap position for these two systems?

Thanks
Cheers
JHW

[Hardy Heinlin]

I can't remember what is modelled in PSX. For example, does the #1 Hydraulic Demand Pump run if (due to a failure) only the outboard TE flaps are capable of moving?

The flap related DEM-pump-run command fails when the FCU fails (FCU R commands DEM 1, FCU L commands DEM 4). Mechanical flap failures have no influence. Of course, there are further failures that can stop the DEM pump (EDP failure, HYDIM failure, low pressure, fuel cutoff), but they are not flap related.

The QRH suggests that both continuous ignition and approach idle are referenced to the inboard trailing edge flaps.

Sorry if I've asked this before, but does PSX use inboard TE flap position for these two systems?

In PSX version 10.1 and earlier, in the ignition logic of each engine the flaps-out status is set when any actual TE or LE flap is out of up and FCU L or R is powered.


Cheers,

|-|ardy

[John H Watson]

In PSX version 10.1 and earlier, in the ignition logic of each engine the flaps-out status is set when any actual TE or LE flap is out of up and FCU L or R is powered.

I'm trying to figure out what happens if the "flaps out" status is linked only to Group A LE Flaps and/or Inboard TE Flaps (as suggested by SSM 27-51-04 and Jon's QRH). For example, it is possible to inhibit the extension of the Group A LE flaps by pulling all 5 Group A LE Flap Control CBs on P6. In this case...
Would this, say, not turn off the Wing Anti-Ice with the flaps extended (where this option is enabled)? I can't see a reason why this feature would be linked to TE flaps.
This would stop the Outboard Ailerons from unlocking (with flap extension) because aileron lockout is specifically linked to Group "A" LE flaps (according to my training manuals).

If there are systems influenced by both Inboard TE and Group A LE flap position, if Group A LE flaps were stopped from extending (by pulling CBs) and the Inboard TE flaps were stopped from extending (by some means*), these systems would not be activated (even though all the other flap groups were extended).

*I haven't figured out a way of doing this yet.

Hope this makes sense.
Cheers
JHW

[Hardy Heinlin]

I have 3 variations regarding flap state in my manuals. One wiring schematic simply say "Flaps not retracted". Another wiring schematic suggests that only Group A L/E flaps are involved (27-51-04). I wonder if it's possible to disable only group A on the real aircraft, but have the rest of the flaps extend normally? My training notes offer a 3rd option: "Any time the flaps are out of zero detent (not stowed)" ... which might suggest the lever position (?).

To me, "stowed" doesn't sound like the lever position. It rather sounds like a flap stowed inside a wing body. Something is stowed in a closed box. The flap lever is never stowed somewhere; it always sticks out of the box :-)

I'll leave the ignition stuff as is (any flap out and FCU L or R powered) until it's proven wrong.


Cheers,

|-|ardy

[Hardy Heinlin]

Those FCU data links are now modified in PSX 10.1.1-beta2:

http://aerowinx.com/board/index.php?topic=4020.0


Cheers,

|-|ardy

[Avi]

Hi,

When I active Severe Flap control failure I get 'X' on all TE bars but not on the 6 LE boxes. Why not?
[edit]
There are 2 options here:
1. I should get it for all the LE boxes too.
2. I shouldn't get any 'X' at all because:
    A.   The Power Supply Modules (PSMs) are operational and supply electrical power to the TE RVDTs and to the LE position sensors units so their positions are known.
    B.   Since all FCUs failed, they can't give me any position data (right or wrong).

If we say that in this malfunction only the control functionality of the FCUs failed and not the display functionality then it is the A case.
[/edit]

When I active the non severe failure I get 'X' on the right TE bars. Why?
PSMs 1L and 2L are operational (so the right RVDTs are getting electrical power) and FCU R is operational so what is the problem?

Cheers,

[Hardy Heinlin]

Hi,

on the Malfunctions menu, FCU failures are not failures of the flight control power supplies; the flight control power supplies remain operative.

If you pull the CBs of the flight control power supplies, more systems will fail.

Non-severe: FCU L and C fails. -- Like in previous versions, FCU L provides the power to the right TE flap RVDT.

LE data is lost when all four AC power supplies 1L, 1R, 2L, 2R are unpowered.

You may interprete the new malfunction model like this: Power goes into the FCU, from there to the TE flap RVDT; position data goes from the TE flap RVDT to the EIU. Now, when the FCU malfunction is activated, the electric link from the RVDT to the EIU is still intact, but the totally internally failed FCU will no longer provide power to the RVDT.

Anyway, I think the signals from the TE RVDT are processed in the FCU as well. So no matter whether the link between the RVDT and the FCU goes the one way or the other, the totally failed FCU will fail the respective RVDT system in any case.


Cheers,

|-|ardy

[John H Watson]

You may interprete the new malfunction model like this: Power goes into the FCU, from there to the TE flap RVDT;

Behaviour may only be resolved by pulling FCUs from the racks in the MEC

The simplified schematics and the more detailed schematics show power going directly from the FCE Power Supplies to the flap position RVDTs. All FCUs, however, are sent a sample of this 26Vac (from all FCEs). I don't know what the FCUs do with this monitored voltage. Is it used as a reference voltage (to help generate position information)? My RVDT theory is a little rusty. Or is it simply used as a signal to tell the FCU to ignore flap position information if the voltage is not within tolerance?

https://en.wikipedia.org/wiki/Rotary_variable_differential_transformer

All TE flap RVDTs send position data to all 3 FCUs. There are links in the Wiring Integration Units in the MEC to distribute the data.

If an FCU fails, the other FCUs still have that monitor (or reference?) voltage (if required) from the FCEs and they still have position information from the RVDTs.

position data goes from the TE flap RVDT to the EIU.

Yes, via the FCUs (See long confusing message board debate on whether certain parts of the FCU can still operate with FCU internal failures and when Alt Flap is selected)

Anyway, I think the signals from the TE RVDT are processed in the FCU as well. So no matter whether the link between the RVDT and the FCU goes the one way or the other, the totally failed FCU will fail the respective RVDT system in any case.

I can't see how this can happen. Only an FCE Power Supply failure will stop an RVDT producing a position signal. An FCE Power Supply failure removes the power to the RVDT directly and it removes that reference/monitor signal going to all 3 FCUs (from the FCEs). 

I believe single or double FCU failures will still produce complete flap position information.

I'm not sure if this agrees with Avi's theory.

Rgds
JHW