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docjell

Topping up brake fluid in Sportstar Plus

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Brakes in my Sporstar were getting spongey so attempted to top up and bleed system - maintenance manual helpfully says "use a syringe" to top up the individual pedal cylinders. Inspection (whilst virtually standing on my head in the cockpit) revealed a small threaded hole in the cylinder top - probing it felt blind - about 3 mm - whats on? Is it a valve? Why threaded?

 

As an anaesthetist I'm very comfortable with syringes but thought I'd seek advice before flooding the carpet with brake fluid! I gather the latest Sportstar (sensibly) has a single brake fluid resevoir so my confusion is probably not unique to me.

 

Advice from someone who has mastered this gratefully received!

 

 

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Normally aircraft brakes are bled from the wheel back to the master cylinder. The threaded hole in the master cylinder top is for a piece of pipe that is inserted down into the cylinder to the max level of the fluid. This pipe/tube is conected to a flexible hose that goes into a bottle to collect the overfill. Fit this pipe to the cylinder top, fit the hose into the collector botttle then fit the connector onto the bleed valve on the wheel cylinder. Make sure there is no air in this line fully charge it with fluid before connecting. Open valve and pump fluid into the system, have someone watch the fluid returning to the bottle, when the required amount is pumped into the collecting bottle lock off valve. it should be ok now.

 

Important. Does your aircraft use brake fluid or hydralic fluid? if you have inadvertantly added brake fluid instead of hydralic fluid you will have to change the o'rings and check for corrosion in the master cylinder and wheel cylinders.

 

ozzie

 

 

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Thanks very much for your input Ozzie. Shortly after posting I got a call from the importer Peter Harlow, who was as usual very helpful. The maintenance manual should probably read "top up with a syringe after removing the (invisible ) hex head plug" located at the bottom of the aforementioned threaded hole. So - no valves, no trickery, just a manual that is light on details!

 

Peter told me that the system is effectively 'automotive' ie. use Dot 4 fluid (not aviation hydraulic fluid) and bleed in the conventional way ( master to slave). Knowledge is power!

 

Thanks again

 

Chris

 

 

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Chris,

 

You have to be a bit of a contortionist plus have an inspection mirror and light. You can use a standard hex key to remove the filler grub screw, but it's fiddley owing to its proximity to the piston shaft. A long tee handled hex key would have been easier.

 

Be very careful that you don't drop the grub screw as it falls straight in between the pedal bracket and floor matting. (ranting.gif.5470ae857812d977cdbca23fadaf1614.gif)

 

Fill the cylinder slowly with the syringe and be prepared for it to spill over when full. When it does, draw a few ml back into the syringe to make some space for the grub screw, replace the grub screw and then clean the top of the master cylinder thoroughly.

 

Cheers!

 

 

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Ahlocks- thanks! Contortionism indeed. Mirror and light worked well but 20 years off my personal airframe would have helped in the flexibility department! Will employ a short teenage gymnast next time happy to stand on his/her head!!

 

 

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Another option is to remove the cover where the bang chute goes and attack from overhead rather than trying to be athletic. Downside is that it's time consuming removing it, but at least you can work standing on your feet. It gives good access to the pedal hardware and back of the avionics panel. I'm planning to do the the next brake fluid change while the cover is off for the transponder calibration check. (or if the new Tojo's premium brand altimeter goes tits up like the original)

 

Was it your beastie that tried to spit its canopy? If yes, was it just the latch detent spring that failed? 038_sweat.gif.5ddb17f3860bd9c6d8a993bf4039f100.gif

 

Cheers!

 

 

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Yes! Correct on both counts! Spring has now been replaced and all seems well - though if it didn't happen again I'd be delighted! Peter Harlow assured me that he was required to fly the aircraft with canopy open by Evektor as part of his prospective importers "accreditation" - and it was quite stable and controllable. Cheers

 

 

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Thanks Chris.

 

Might make checking the spring part of the pre flight me thinks...040_nerd.gif.a6a4f823734c8b20ed33654968aaa347.gif

 

 

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I did - it was there at the "harness & hatches " stage but was later found on the floor! However - triple checking from now on. Could make me quite neurotic!

 

 

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Doc,

 

I'm thinking more of checking the spring for fatigue cracks as part of the pre flight inspection. 022_wink.gif.2137519eeebfc3acb3315da062b6b1c1.gif I'm already a bit compulsive with the hatches harness bit...076_joystick.gif.1d2ed07889352a966338f6390696faff.gif

 

Cheers!

 

 

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Good thought -on board - I'm going to get more anal by the day! Did cross my mind to suggest that Evektor should include 'canopy opening in flight' in their "things to do when its going pear-shaped" list - I'd have felt a whole lot better if I knew that we weren't about to auger in!

 

cheers and thanks for the input!

 

 

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