Static Lines

Model Specific Discussions about the Sling TSi.
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MTJ
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Static Lines

Post by MTJ »

Just curious.

My QB has two static ports and TAF has run both lines to the rear seat area. I have noticed some builders connecting the tubes together in the aft section. A question For you way smart people.... is there any advantage to continue to run both lines to the cockpit or connect them and don't worry about it?

I am using ony 1 G3 and 1 G5 .

Thanks
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PhilipRueker
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Re: Static Lines

Post by PhilipRueker »

Well if you ran both and connected them separately to different inputs they might read differently, so hence you typically want all of your instruments to operate off the same static line to avoid that and use T-splices to connect multiple instruments to the same static line.

My understanding of the rationale for the two static ports and connecting them is to create a more even static reading (but from what I've seen discussed, there seems to be some variability with the static ports proper reading on the sling).
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MTJ
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Re: Static Lines

Post by MTJ »

Yup

I wasn't going to hook them separately to instruments,,, Just wondering were others have spliced them together. I ended up doing it further aft with equal lengths of line to the "Y" from the static ports.

I am also installing an ALT static in the panel as well. If I get bored down the road maybe I'll rig a static cone test for fun.
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hpmicrowave
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Re: Static Lines

Post by hpmicrowave »

Static lines need to be connected together and the single averaged static source then connected to the instruments. But FYI most all the static lines in the Torrance Slings are disconnected behind the panel and the instruments just use the area behind the instrument panel as the static source? I was told the factory didn't trust their static locations (all slings). After some testing of the AOA project system im a part of on both the TSI and some Sling 2's back at Torrance last March I believe the behind the panel static option at slow speeds is worse than the outside static source errors I was told about.

From my limited knowledge of static source ports you don't want a port that is flush against the side of the plane but it should be slightly away from the skin. I'm working on a TSI quick build fuselage and it has the standard Sling flush static ports that I plan on drilling out and replacing with the following raised static ports from aircraft spruce. It will be a while before I can report back my flight test results but maybe we can start collecting some test data from the flying Slings TSi's and what differences there are with factory fuselage static sources vs the behind the instrument panel static source? I also can send anyone who is interested an Excel data collection matrix and flight test procedure that will help calibrate your airspeed indicator.

https://www.aircraftspruce.com/catalog/ ... ports6.php

Cecil
Cecil Jones
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PhilipRueker
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Re: Static Lines

Post by PhilipRueker »

hpmicrowave wrote: Sun Jan 24, 2021 8:39 pm From my limited knowledge of static source ports you don't want a port that is flush against the side of the plane but it should be slightly away from the skin. I'm working on a TSI quick build fuselage and it has the standard Sling flush static ports that I plan on drilling out and replacing with the following raised static ports from aircraft spruce. It will be a while before I can report back my flight test results but maybe we can start collecting some test data from the flying Slings TSi's and what differences there are with factory fuselage static sources vs the behind the instrument panel static source? I also can send anyone who is interested an Excel data collection matrix and flight test procedure that will help calibrate your airspeed indicator.

https://www.aircraftspruce.com/catalog/ ... ports6.php

Cecil
I had a similar thought of if maybe the flush static port is part of the problem versus a Cessna style port like the one you linked.

It will be very interesting to see some test results from people on seeing what might work to produce consistent correct results.
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msejourne
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Re: Static Lines

Post by msejourne »

Hey guys,

Thanks for bringing up this subject! I suspect that the static ports at the back are the most accurate based on most results for most low wing airplanes like the TSI (see https://www.kitplanes.com/static-port-l ... libration/). I also plan to fly the airplane IFR and since Alternate Static Source is also required for Canadian airplanes, I'm curious as to what kind of error using cabin ambient will produce as an Alternate Source. I would think that at slower speeds, the increased angle of attack also created by the canopy will most likely create a lower cabin ambient pressure, thus resulting in a higher indicated airspeed. However, as an ex-fighter pilot I plan to install the AOA system anyway because AOA is unaffected. I'll just keep following and look forward to results anyone gets in the future :) .

Cheers! 8-)
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ibgarrett
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Re: Static Lines

Post by ibgarrett »

Has there been any updates on this thread outside of here? I'm pretty curious as to what evolved as I'll be getting close to this point here soon.
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hpmicrowave
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New TSi Static Port Location

Post by hpmicrowave »

The Sept 21 TSi fuselage Instruction manual page 92 has details on the new factory recommended Static Port locations, just forward of the Fresh Air NACA ports. So I am using that location and my own Aircraft Spruce Sourced Ports (Raised Cessna Style).

The factory has been recommending in the Pilots Manual for several years to leave the static ports just open behind the instrument panel and I know that's the location Torrance has been using. Yes along the sides of the rear fuselage has been the primary location for light aircraft static ports for years, but they have never worked well for the Sling aircraft. Evan did a test last year between using the rear fuselage ports and the inside the plane location. He said his airspeed was about 10kts high on cabin static and about 10kts slow on the external ports. He installed a static port switch so it was easy to change over). He said he just adjusted the airspeed offset in the G3x calibrations. But I wouldn't think the error is constant over the whole speed range.

Anyway after I get my plane flying I'll be doing some serious calibration runs to know for sure.

Cecil
Cecil Jones
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Re: Static Lines

Post by Skepilot »

I don't believe there's any such speed offset calibration in the G3X. If there is, I'd like to know where.

The new forward static port location also requires these circular shields (which Sling Technical will provide), otherwise they're not accurate either.

There was another TSi which had its static ports back in the old aft fuselage location, but used Van's-style hollow rivet static port, and his speeds were dead-on through all phases of flight. Pretty sure that's how Evan is going to be doing all of his builds going forward.
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ibgarrett
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Re: Static Lines

Post by ibgarrett »

Evan just updated his YT channel last night and talked about the static port in - one was so/so in it's positioning, the other one he said was spot-on.

Brian Garrett
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