Aug 16, 2021     Fuel Mod Complete - (11 hours)       Category: Fuel System

After mounting the w new fuel pumps in the wing roots I then had to wire the the pump switch. This is an ON-OFF-ON. I want to have a microswitch in the fuel selector valve that would automatically switch pumps with the valve position, but the area was just to limited in space and I needed a more secure location for any movement.

The switch obtains power from either main fuel pump A/B switch. I opted for an OFF position in case of any problem with the wing pumps. The switch contains lights that show power to the pumps when selected.

  Jun 26, 2021     Fuel system redesign - Part 2, preliminary work - (11 hours)       Category: Fuel System

06/26/2021

Back to work full time so the Sling build really slows down.

Finished the install of the 2 wing root fuel pumps. The plumbing is finished for the fuels systems and should add robust safety with pressure supplied form each tank to the selector then to the Rotax pumps.

I will put the wiring/switch work under electrical when that taks is completed.


06/15/2021

After replacing most (but not all) of the rubber hose fuel lines in the forward firewall I began to re-think the fuel delivery from the tank to the firewall. I have never been happy with the TAF fuel pump added just down stream of the Fuel Select Valve for the following reasons....

1) It is one pump (with a bypass) for both tanks. The reasoning is for the vapor pressure of the fuel. This is a valid reason as my airport is 6000' MSL and I routinely fly at 12, 000+ MSL. However, still not happy with just one pump.

2) The pump is located in the cabin. Multiple leaks points after the Selector Valve with the pump, bypass, and other connections

3) Noise and safety. Fuel pump instructions (on most pumps) ask that the pumps be installed near the fuel tanks and at the same level of the tank. While many pumps have a stated "Lift" height and should suction from the tank the best application in nearest the tank. I did a test on the suction Lift of the pump and was not impressed. For these reasons I would prefer the pump to be in the wing roots.

I decided to purchase 2 Facet electronic pumps that will reside in the wing roots. The power to the pumps will be supplied to each individual pump at any one time via an SPDT NC-NO micro switch. This switch will be located on the bottom side of the selector plate just in front of the valve assembly and the fuel selector arm will activate the respective pump with the selector lever position. All power for these pumps will come from the A or B pumps switches on the main panel.

Anytime the A or B Rotax pumps are selected, power will be supplied to either wing root pump based upon the fuel selector position.

First, I removed the installed TAF pump and bypass. The supply line then was connected directly to the firewall ( as in older designs!). I then had to decide how to mount the pumps in the wing root. Using the existing rib required additional support and stiffening. I fabricated additional support plate and shaped it with a metal brake to add stiffness. These will be riveted to the rib.

  Jun 08, 2021     Revising the fuel lines - (21 hours)       Category: Fuel System

6/8/2021

Finishing up the firewall forward metal fuel lines. The lines have heat shield wrap and I also wrapped the fuel filter bypass. I am still not very happy with the rubber supply line to the engine so I may redo to reposition the line with the jet "T"

5/9/2021

I have decided to redo the firewall forward fuel lines. I want to install metal lines as much as possible. I will leave the fuel hoses that attach to the engine for vibration purposes. The fuel pressure sensor should be located as close to the pressure source as possible so I fabricated a mount for the sensor above the gascolator.

More work to do but here is the initial work on the fuel lines

  Feb 11, 2021     Run Fuel lines and boost pump - (10 hours)       Category: Fuel System

The have been many changes to the fuel system of the TSi since the kit was delivered.

1) There used to be 2 inline fuel filters that have been replaced by a single large filter on the fire wall (I think that's good)
2) After the fuel selector valve the is now a single extra boost pump that feeds the the ROTAX pumps and is used mainly for takeoff and high altitudes when using Mogas.
3) the addition of a Fire Wall mounted fuel filter
4) the Addition of a gascolator.
5) The routing of the fuel lines through the firewall is different.

The addition to the center channel of the boost pump interferes with foot warmer because of the needed bypass check valve. So a slight reroute from the pump to the firewall had to be planned out.

I have to plan differently as the firewall is getting crowded and the running of the fuel lines (with fire covering) has become a Gordian knot of a problem. This is also the general area of the inter-cooler.

I may relocate the galscolator as well add AN6 90 degree fuel fittings in different spots to accommodate the fuel lines.

I was having trouble reconciling the fittings with how the instructions are depicted so I sent an email to TAF. The factory sent a photo of the new way the fuel lines go through the fire wall and the now use fittings that attach to the firewall vs. the old way of running the hoses through rubber grommets. Instead of drilling new holes in the firewall I have decided to use the existing holes with different grommets. I am happy with the result, a firm attachment point and grommet protection.

  Jan 30, 2021     Assemble Selector valve - (12 hours)       Category: Fuel System

The fuel selector valve is pretty straight forward. LEFT/RIGHT/OFF. a pull knob to get to the off position with return lines. Fitting the valve is another story. The valve sits at a slight angle with respect to the panel an transitions to the center console. It is required to dismantle the valve to fit the barbed fitting at a certain angle both on the left and right and on the top.

Once this was done a test fitting was done with the composite housing that makes up the dash.... it did not fit.

Ideas were tossed about like tapping the fitting so they would seat lower (tried it, minimal help). Heating the composite to make room for protruding fittings. (did it, but I did tnot ake it too far so as to not distort the composite). Finally, an email to Sling (TAF) to see what the deal was. They admitted it won't fit as is and said they grind down the corners of each brass fitting and sand the composite away.

So I ground the corners of the brass fittings and used my own heat method on the composite because I was not comfortable sanding the material away

  Oct 16, 2020     Remove Right wing tank for Leak check - (6 hours)       Category: Fuel System

10/16/2020

Did a soap bubble check after pressurizing the tank to 1 psi. I noted the temperature and used the ideal gas law as a reference (PV=nRT simplified to PV=T) and monitored (time lapse) for a day. Pressure held.

10/5/2020

Moving on to removing the leading edge tanks for pressure/leak check. After a successful check I will rivet to to wings. The only problem is that it seems some one at the factory was a bit careless with some adhesive and glued the tanks to the wing!

After consultation with a mechanic he suggested working some solvent in the seam with some really thin aluminum sheet acting to cut through the errant adhesive. After about 4 hours the tanks were successfully freed from the wings and the setup for the tank test was started.