Throttle box Stops #60

Throttle box Stop plates were cut from sheet Ali & tie wrapped on, necessary to prevent fully backed off levers from reverse kinking the cables.

Windscreen Lexan Replacing #59

Windscreen Lexan Replacing 
Fitting a new windscreen The old one was sprung out easily, following the Rans build 'book' method. It was used as a reference for drilling the new one to 3/4" and 7/8" inset for the 'Z' Ali edge strips. Now pop riveted on exactly according to the descriptive paragraph in the manual. Ignoring my 1990 assembly book's conflicting sketch on the next page which showing everyhing at 1" offset.
The new Lexan screen with 'Z' strips fully pop riveted on was carefully taken to the hangar. It clipped in easily exactly as per 'book', the pix below show without & with. The plastic protective film was left in place as recommended by Rans till ready to fly. I did check pull off a section to find out if some 'scratch marks' came off too - relief they were only on the protective film, so that was all O.K. too.

Tailplane incidence change improves control #58 59 61

Tailplane incidence change improves control.
Compared with the early brackets, newer Rans part KPHS0026 has two new positions for the ‘hinge bracket’ bolt. You need a pair, one each side. See current build diagram item 25. I bought them ($20).
The top hole already reduces tail upforce & the second lowers it still more. It’s a factory originated mod to mitigate that heavy nose down when the elastic trim is off.
The old removed lugs are shown, with the later type Rans S4 ones already installed using the top of two available holes for the tailplane 'hinge' bolt, which is ~1/4" lower than the original.
They fitted straight onto the original through fuselage bolt on my 1990 S4.

The elastic trim cord under the seat was subsequently reset by trial & error to a considerably reduced tension.  

Exhaust Securing Springs wear/repair #58 59

Exhaust Securing Springs wear/repair.
A problem with all aircraft engines that use springs for silencer/muffler retention. Easy solution, fill the springs with some RTV Silicone ‘rubber’ and the problem virtually went away. This dampens the vibrations quite a bit and stops a lot of the wear on both springs, mounting points & springs breaking. After the silicone was applied they never broke.
Where the 3 silencer retaining springs hook on and it’s already wearing deep grooves through the lugs at the exhaust connection. To avoid removing for weld repair, change the attachment of the springs. Put a bolt through the hole in which the springs normally are & hook the spring to the bolt with a stiff nut to keep it there. That way the spring is pulling on a round piece and not on a sharp edge.

Revised seat suspension. #57

Revised seat suspension.

A U.K investigation into a death following loss of control of an S4 aircraft noted the aileron torque tube close underneath can be jammed by the pilots seat. It is mandatory in the U.K to replac the webbing which suspends the pilots seat with steel cables and steel height settable tabbed ends.
See PFA Airworthiness Information MOD/193/005.

Bing Carburetter 'choke' operation. #57 64

The several Rans I've seen have three levers on a common shaft with single friction tightening bolt, mounted on the forward left side of the seat. From the outside 'choke', throttle & trim.
The choke is a simple enricher fuel feed jet opened & closed by a lever to a second fuel source, via a pad in the Bing carb in a side chamber. It increases fuel flow through a separate jet to richen the mixture for a cold engine but the throttle needs to be closed for full suck effect on it. It's an on/off device & does not prime the engine, nor offer much partial 'strangling' (unlike a butterfly choke). Once the engine warms up, it should be shut off.

Fuel 'Primer' #56,58,65

Fuel 'Primer', a Rotax 447 question

Connect your plunge primer fuel supply direct to its own dedicated pipe from the tank, not the main feed line, because if/when its own valves inevitably start to dribble it won't compromise the engine's suction feed.

My 1990 S4 was fitted with a plunger type carb. enricher fed via a Tee'd plastic pipe off the main fuel delivery line. Never constant it also bled fuel forward when squeezing the delivery primer bulb. I removed it completely to reduce the risk from its thin pipe for leaks. You also lose a few ounces weight. Full choke & closed throttle with prop hand turned 20 times is my method. Vince 'primes' the carb by blowing down the float chamber equalising pipe at its brass centre connection to atmosphere. I do it too as it's a magic method when cold.

Fuel feed failure risk. The squeeze bulb fuel pump 'prime' internal non return valve can also risk in flight feed blocking. Fitting a by-pass fuel tube is said (see below) to be a solution To feed fuel before starting, simply pinch the tube whilst squeezing the bulb.
The squeeze bulb is a primary and essential part of fuel delivery system. Black and gooey stuff from the pipes is not. I found my bulbs would do this and also crack on the outside and the ends would pop off on one of them, not to mention the valves malfunctioning as well.
After discarding it there was no more gunk in the filter and all the fuel lines stay the same colour without the blackening they used to get.
Another sign of the black rubber disintegrating is the change in colour of the fuel lines. Seems the premixed fuel might eat the rubber stuff up. Some bulbs are made out of oil resistant materials but they don't have labels on them. I now use oil injection and put a Facet electric pump in place of the bulb and the problem is now gone. I switch on the pump while starting then turn it off. Can always be used a emergency pump if the Mikuni gives up."