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I don’t have a switch. The pump is powered directly from a VP200 circuit that is only set to be on during takeoff mode, which lasts 2 minutes. When I go back to full power on a go-around, the VP switches to takeoff mode and turns the pump back on for 2 minutes. If I didn’t have a VP 200 and I wanted to be fancy, I would buy a relay with an integral 2 minute timer, and add a button to my takeoff checklist that would only require a single push. The timed relay would turn off the pump 2 minutes later. Worst-case, if you forgot to press the button on a go around, you would have the same ear pop that you had before you installed the pump. Besides, how many go arounds are you doing? If it is a high number, then you probably have other bigger issues to deal with J. From: vtailjeff@aol.com [mailto:vtailjeff@aol.com]
Sent: Thursday, March 14, 2013 4:59 PM
To: Lancair Mailing List
Subject: Re: [LML] Re: Pressurization Pete, no disrespect but what about a go around, touch and go, etc.? Do you have to reset the switch? It sounds like from your description you have to manually set the system for every takeoff event. Setting a switch to depressurize when on the deck is not needed, as there is no way the engine will generate enough pressure when idling around to even remotely pressurize the cabin. You will lose all of your pressure when you pull back your power on the approach. There is no check valve in our mixer boxes, so any residual pressure will get sucked into the engine due to the low manifold pressure of approach/landing/taxi. Here is the $15 pump I use to pull a vacuum on the Dukes during takeoff: https://solarbotics.com/product/45050/ I have a VP200, so I just set it so that the pump is on during takeoff mode, and turns off 2 minutes later when the system switches to cruise mode. It completely eliminates the takeoff pop. Unless I am flying really high, I set the Dukes to 2500 feet above my destination elevation. This way, when I power off on the approach, the cabin pressure will already be equalized for my altitude. A properly calibrated Dukes will set the cabin altitude to about 700 feet above what you set the destination altitude. I just use standard automotive vacuum hose to connect the pump to the dukes. It doesn’t need much vacuum to open the bellows (you can suck them open with your mouth if you try), so any semi rigid hose will work fine. The system should be set so that the aircraft is unpressurized on deck-- usually through a gear down (ivp) or weight on wheels switch (Evo). This is to protect the pressure vessel. Yes this I do not understand, my AC and pressurization is on after I start the plane and stops when I stop the engine, and my cabin is cool and fine like this.
Ronald Stevens I don't pressurize until I get up to 6-8,000 ft. This keeps my cabin a bit cooler and comfortable at low altitude and doesn't steal power when it's needed most ie on takeoff and early climb out. Do others do it differently? N750DW Propjet On take off the other day I was up to 2 Psid by the time I went wheels up. That was with the gold box 95% closed. Does anyone happen to have a dukes manual?
Typing and grammar errors courtesy of Siri and the iPhone.
On Mar 13, 2013, at 14:14, Colyn Case <colyncase@earthlink.net> wrote:
> If you have a vacuum system, you can hook that up.
> If you don't, you can buy a small pump and hook that up. I haven't done the latter but I've heard the door seal pump works okay for this application.
>
> Using that main vac pump almost completely eliminates the cabin pressure increase at takeoff.
>
> On Mar 13, 2013, at 1:21 PM, Todd Long wrote:
>
> How do most of you operate the pressurization system to avoid the major bumps at takeoff? My vacuum line was capped.
>
> Typing and grammar errors courtesy of Siri and the iPhone.
>
> On Mar 13, 2013, at 10:56, Paul Miller <pjdmiller@gmail.com> wrote:
>
>> Autozone, lots of smaller sizes for vacuum hose by the foot.
>> On 2013-03-13, at 10:51 AM, Colyn Case <colyncase@earthlink.net> wrote:
>>
>>> I'm looking for a minimum thickness vacuum hose just to hold the dukes pressurization valve open on takeoff. Right now I have a 1/4" i.d. .64" o.d. big fat rubber line. I don't see anything on McMaster Carr that is thinner wall. But given it probably needs to handle maybe 10 psi of vacuum, the big fat rubber hoses seem like overkill.
>>
>>
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