Speedbrake Arming

[Hardy Heinlin]

Thanks, Nimsu87 :-) What you and Avi and I have in common is the direct, critical speech we apply without flowery loop ways. It's the fastest method to solve problems. An open word here, an open word there: Bug cleared.


Cheers!

|-|ardy

[nimsu87]

That's a very good point, and I definitely agree. Life is too short to be 'going round the houses'. Which is my favourite phrase/idiom for what you're describing! I'm not sure if you have heard of that phrase? All the best to you both!

[John H Watson]

https://www.youtube.com/watch?v=UrH5LcL4HMI

He knows what he is talking about... but we'll forgive him his slip of the tongue in front of the camera.

[John H Watson]

https://www.youtube.com/watch?v=-_OM6kSCJNU

A quick look inside the RH body gear wheel well.

Note the fire detector wires in the curved section of the roof.
At 0:47 can be seen the outboard trailing edge flap drive motor with the barber pole striped drive shafts.
The coppery coloured pipes behind him at 1:27 are the hot bleed air ducts for cargo heat and air conditioned cargo trim air (where applicable).   

I'm surprised he went up there in a clean uniform. I usually felt like taking a shower after I crawled up there.

[Jeroen Hoppenbrouwers]

He skipped my SATCOM box!
He skipped my SATCOM box!
He skipped my SATCOM box!

<running around in panic>

I completely understand that he references to the two forward MCDUs as "flight management systems" but these terminals really connect to so much more ... ah well ...

Next time I'm in Hong Kong I'll try to get him to pay attention to less known systems!  :-)


Hoppie

[John H Watson]

https://www.youtube.com/watch?v=dSRaUMChRl0

Daytime logo light (and upper antenna) check

He skipped my SATCOM box!
He skipped my SATCOM box!
He skipped my SATCOM box!

I don't see a Satcom antenna, unless they are side mounted on Cathay?

[Jeroen Hoppenbrouwers]

You see it clearly at 0:46!

It sits right of centerline (starboard). The other one you see a bit closer is the GPS antenna. They are close enough together that I need special filters to not step on the GPS L1 at 1575 MHz (I am on 1610-1620.5 MHz).



The off-centerline position required some calculations to figure out the horizon shift as these antennas have their cutoff just a few degrees above their local horizon. The centerline has a stringer that makes it difficult to mount anything there; I bet the GPS was forced there and caused mayhem at the mechanical level. Normally we install on a 747 between the top and the first stringer, where the upper deck roof is at about 3.3 degrees off level. But sometimes we encounter pre-installed Iridium antennas and these tend to be further away from the centerline at about 10.1 degrees off level. That leads to signal issues once in a while. However, the cruise pitch-up level of 3-5 degrees also delivers the same kind of issues and that is unavoidable.
Iridium satellites are so dynamic that you will inevitably encounter brief (seconds) episodes of low signal anyway, so the system can cope with this.



The Iridium antennas we use are so small they are hard to spot. Basically a shoe sole on the crown. Not more than 1.5 cm thick.

[John H Watson]

You see it clearly at 0:46!

I forgot you used a special antenna and not the big Satcom one.

Looks like the ERF has all different locations for antennae compared to the standard ER (because of the shorter upper deck on the ERF). The top hatch is probably around body station 400. Our ER GPS antennae are at station 810/850. Our Upper TCAS antenna is at station 450. I don't even see a TCAS in that video (unless it's below the line of sight)

[Jeroen Hoppenbrouwers]

It's not so much "special" as "not Inmarsat". Geostationary satellites need a heavy duty beam steering antenna with lots of power. Low Earth orbit (781 km) Iridium can get away with 7W peak and a passive omnidirectional antenna.

Of course don't expect internet speeds. Ha. It's all 1980s 2400 bps. Enough for three voice links and ACARS, with my box. On freighters we don't use the third (cabin attendants) phone line. Just two ATS SATVOICE priority lines for the flight deck.

Upcoming Iridium Certus is better but at the expense of a beam steering antenna.

Hoppie

[fsam]

I'm trying to remember what generates the EICAS message SPEEDBRAKE ARMED. I've looked through all the Boeing manuals and there is no clear link between the various speedbrake handle position sensors and microswitches and the EICAS. The speedbrake handle even has an input into the autopilot computers. Perhaps the EICAS gets SPEEDBRAKE ARMED info from the A/P computers?

MSG will be generated by 3° Auto Speedbrake Arming SW S217, signal is feeded to MAWEA / Config Warnign Card and further to EIU's to display. Best regards

[John H Watson]

MSG will be generated by 3° Auto Speedbrake Arming SW S217, signal is feeded to MAWEA / Config Warnign Card and further to EIU's to display.

The schematics (27-62-01) show a direct feed from the switch to the EIUs i.e. EIU pin K5. In 27-62-01, the label on pin K5 is "SPEEDBRAKE AUTO", but in chapter 31, pin K5 is labelled AUTO SPDBRK FAULT.

(EDIT: I see the link in the training notes going from S217 into the MAWEA as you describe, but the signal going to the EIUs is labelled Config Warning).

[John H Watson]

In the wiring diagrams, 27-62-11, S217 feeds splice YA2, which goes to EIU pin K5. K5 is labelled "SPEED BRAKE AUTO". The labelling is contradictory (chapter 27 vs 31)

[Jeroen Hoppenbrouwers]

Never trust airplane wiring diagrams or whatever.
Always go to the darned sovereign citizen and question her in person.
We lost soooooooo many months of work because somebody trusted the drawings...


Hoppie

[John H Watson]

Always go to the darned sovereign citizen and question her in person.

I don't have a spare monarch available. And where are you going to find someone willing to break a serviceable aircraft?

To those willing, pull the SPEEDBRAKE AUTO CONT circuit breaker (for safety), pull MAWEA A & B circuit breakers and the FLT CONT CMPTR L/C/R circuit breakers, then ARM the speedbrake to see if the message appears.

If not, reset the FLT CONT CMPTR L/C/R circuit breakers and try again. In PSX, the message appears to be linked to the Flight Control Computers, so this may have been tested and proven before.

[Hardy Heinlin]

Yes, to get the "ARMED" message in PSX, at least one FCC must be operative. And the second condition is the lever angle.

In an earlier alpha version the condition was >2.9° AND <6.0° (which clearly refers to that documented 3° switch position).
In a later alpha version it changed to >4.0° AND <6.0°.

I guess this modification was the result of a discussion 10+ years ago.

[John H Watson]

In an earlier alpha version the condition was >2.9° AND <6.0° (which clearly refers to that documented 3° switch position).
In a later alpha version it changed to >4.0° AND <6.0°.

I guess this modification was the result of a discussion 10+ years ago.

Interesting. Just reading the FIM (Fault Isolation Manual) and it says to adjust the speedbrake arm switch (S217). It also mentions "between down and 7 degrees as normal".

[Jeroen Hoppenbrouwers]

And where are you going to find someone willing to break a serviceable aircraft?

Usually we either poke into existing terminal blocks without disconnecting anything to find data, or we remove an LRU and replace it with a custom breakout LRU that allows access. So no real breaking. But once the breaking has happened and the new wiring is in and does not work ... oh my ...


Hoppie

[John H Watson]

Usually we either poke into existing terminal blocks without disconnecting anything to find data, or we remove an LRU and replace it with a custom breakout LRU that allows access. So no real breaking. But once the breaking has happened and the new wiring is in and does not work ... oh my ...

The wiring is correct. This is a core system. All the diagrams and schematics agree with each other regarding on how it is hooked up. It's the function of the wires that is the issue here, once it enters the EIU and MAWEA.

By breaking, I mean all tasks involve some risk, including the dropping of screws into hard to find places.

Accessing the terminal block for switch S217 probably involves removing the "A" Zone ceiling panels below the cockpit. The wiring which goes "directly to the EIU" goes via CB panel P6 (generally a power-off job if you're messing with that stuff) and then down to the Main Equipment Centre. The wiring then goes via a Wiring Integration Unit which involves the removal of the forward cargo panels.

Pulling and pushing CB's sounds like an easier step, but even that comes with side-effects (broken CBs, difficult to erase fault messages, personnel injury if the aircraft has hydraulic/electric power and someone is in the wrong place at the wrong time,.... 

[Jeroen Hoppenbrouwers]

"The DFDAU produces data for the whole time the power is on."

... build it like that ... use new FPGA that can extract discretes from streaming 717 data ... less wires!

Reality: the DFDAU produces only data if N1 >= 20%.

... need bunch of new wires anyway ...


Hoppie

[John H Watson]

"The DFDAU produces data for the whole time the power is on."

DFDAU?