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Dennis Johnson
Joined: 10 Jan 2006
Posts: 89
Location: N. Calif.
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 Posted: Sat Jan 11, 2014 8:18 am Post subject: How to Toggle Speed Brakes with Momentary On Switch? |
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Hi Valin,
If your Precise Flight speedbrakes are the same as mine, which I think they are, you need the function of an ON-On switch. That's because connecting ship's power to pin #6 extends the speedbrakes and keeps them extended; connecting ship's power to pin #7 retracts the speedbrakes. You can see this on the attached wiring diagram from my wiring book. (I drew it in AutoCAD and converting it to PDF screwed it up a little, but it's still readable.)
I've seen at least one Legacy wired with an ON-OFF switch. It sort of works because the speedbrakes controller automatically snaps the speedbrakes closed if all power is removed. But instead of a smooth powering closed, they snap closed fast and hard from a strong spring inside them.
To answer one of your questions, power is continuously connected either to pin #6 or pin #7 at all times. Disconnecting power will automatically (and almost violently) retract the speedbrakes. It sounds like an ON-ON latching relay will work fine.
Contact me directly if you want more info on this.
Thanks to Bob N. for his advice to create a Wire Book with one page per component. I've referred to mine many, many times.
Best,
Dennis
Legacy, 680 hours
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Valin
Joined: 13 Apr 2010
Posts: 31
Location: Colorado
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| Posted: Sun Jan 12, 2014 8:21 am Post subject: How to Toggle Speed Brakes with Momentary On Switch? |
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Yes, in the version used in the Legacy they scissor up from the wings – see image below...
[img]cid:image001.png(at)01CF0F77.7D4F2F20[/img]
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edpav8r(at)yahoo.com
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| Posted: Mon Jan 13, 2014 9:18 pm Post subject: How to Toggle Speed Brakes with Momentary On Switch? |
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On Jan 13, 2014, at 5:48 PM, "Eric M. Jones" <emjones(at)charter.net> wrote:
| Quote: | Switch Design 101:
Each switch is to be labled describing its function. The condition of the switch must be apparent from its mechanical position, whether or not power is applied.
Airplanes have no momentary bi-stable switches.
Eric M. Jones
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The overhead panel of the airplane I fly at work is littered with both momentary contact and bi-stable latching switchlights. These devices have legends that are illuminated from behind, and which present a flat black face when not illuminated. Unless the illumination is on, the position of these switches is not immediately apparent (even the latching variety, as their "on" state is only ~1/8 inch different than "off" and they don't all stick out the same amount).
For some of them, even legend illumination doesn't necessarily match switch position, as some aircraft systems activate and deactivate automatically (i.e. fuel boost pumps).
When the aircraft is running, all switchlights dark is considered normal operation. Abnormal conditions illuminate switch legends. If the aircraft were powered down, you would have to examine each switchlight closely to be sure of its position, at least one of them would be impossible, and several would require lifting a plastic guard to see clearly.
This type of switchlight is common to every large turbine aircraft with which I'm familiar.
Eric
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fly4grins(at)gmail.com
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| Posted: Tue Jan 14, 2014 1:59 am Post subject: How to Toggle Speed Brakes with Momentary On Switch? |
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****SNIP****From: Eric Page <edpav8r(at)yahoo.com (edpav8r(at)yahoo.com)> ..... Airplanes have no momentary bi-stable switches. >> Eric M. Jones The overhead panel of the airplane I fly at work is littered with both momentary contact and bi-stable latching switchlights. ...
****SNIP****
Same for me and several A/C types I've flown.
[quote][b]
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Eric M. Jones
Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts
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| Posted: Tue Jan 14, 2014 5:51 am Post subject: Re: How to Toggle Speed Brakes with Momentary On Switch? |
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Bi-stable switches?
That isn't to say it's a good design. I suppose some allowances can be made, but the basic principle applies:
Switch Design 101:
"Each switch is to be labled describing its function. The condition of the switch must be apparent from its mechanical position, whether or not power is applied."
One could allow ignoring this principle for switches that:
a) Don't matter if the power is out and then present no surprises if the power is turned on.
b) Don't affect safety.
c) Etc.
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_________________
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net |
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Eric M. Jones
Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts
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| Posted: Tue Jan 14, 2014 8:14 am Post subject: Re: How to Toggle Speed Brakes with Momentary On Switch? |
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A good example of where you can use a bi-stable switch is on NAV COM frequency flip-flops.
Logic: If power is out to the radio, then the switch doesn't matter. If power is restored, then no hazard occurs.
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_________________
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net |
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