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Ultralights

Savannah 1000hr inspection notes.

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Gday, i am about half way into a 1000 hrly inspection of my Savannah VG, it was built in 2007.

 

The engine, a 912 ULS had its service according to the manual, a 200hrly. plus a rotax 5 yearly rubber replacement, i decided on the rubber replacement early, as the rubber fuel lines within the airframe were showing signs of cracking, and during the engine inspection, a few small cracks were found on the fuel lines and coolant lines. in addition to the rotax rubbers, i replaced ALL fuel lines within the airframe also. some lines after removing proved to be severely cracked in some places. in removing all fuel lines, i removed the underwing panels below the fuel tanks, ill get to these later.

 

With the engine worl completed its time to get to the airframe, looking over it with a bright light, i have found lots, and i mean lots of minor corrosion spots externally, fortunately, almost all of it is minor, and was removed with a little light blending, then treated with Alodine 1200, and a zinc chromate primer.

 

With the lower wing panels removed to change the fuel lines, i got a boroscope and inspected the wing internally, fortunately, no corrosion internally on the skins, Spar, rear spar and ribs. but what i did find was severe corrosion on the tank support brackets, it could only be seen using a mirror and torch, as the corrosion was on the vertical sides of the brackets. i have since remade these damaged brackets,

 

continuing with the wing inspection, bad corrosion was found on all flaperon brackets, requiring all to be remade, parts im in the process of making now.

 

The last areas with heavy corrosion was the lift struts, a few small areas of surface corrosion, easily treated and removed, but bad corrosion under the Jury strut bracket, and heavy corrosion inside the jury strut itself. i am sure this is caused by dissimilar metals, as the backet around the lift strut is steel resting on aluminium, as are the rivnuts, which lead to corroded fasteners and the damage within the jury strut. it was also noted, the rivnuts around the lift strut/spar join access panel were also corroded.

 

The last are of corrosion concern was the plate joining the spar to the lift strut, these were found to be heavily corroded where they join the lift strut, requiring the spar plates to be remade.

 

On inspection of the undercarriage, i have found corrosion on the undercarriage itself around the mounting brackets, in a thin line near the forward and aft edges, looking like stress induced corrosion, and also, all the rubbers under the undercarriage where it rests in the channel in the aircraft floor were missing.

 

The nose wheel Bungee chord made it to 1000 hrs use, and was a little worse for wear, replaced.

 

All flight control bushing replaced, as they were a little worn, about 1/4 worn through the entire thickness.

 

This is where im up to with the 1000 hrly inspections and maintenance, other works have been Modifications..

 

Modifications so far include, installing access panels in the lower wing skins below to fuel tanks to allow access to the fuel line joins in the tanks.

 

New panel for 2 Ipads, powered by 2 independent AHARS (Attitude, Heading Altitude reference system)units using both pitot and static air system to derive speed, altitude and vertical speed data. magnetic compass's , Dual band GPS receivers, and ADSB in capability.

 

Engine data provided by MGL Engine monitoring system, with installation of remote fuel pressure sender, 4 new EGT probes.

 

New VG vanes, more flexible, to replace all the VG's as some are damaged or broken off completely.

 

Reshaped engine top cowling to suite the new Bolly Spinner.

 

Other planned mods include removing the landing light from uder the wing and installing it inside the wingtip leading edge behind a clear panel.

 

Adding 1 inch diam holes to lower wing skin between ribs for thurther corrosion and boroscope access into internals of the wing.

 

reinforcing the outer wing ribs with bolt fittings in the lower wing for hard camera mounts.

 

Solid throttle rods, to eliminate vibration associated with vastly differing throttle cable lengths moving throttle through certain RPM ranges.

 

and finally, a Repaint! scheme to be decided!

 

All in all, apart from the corrosion issues, the Savannah has held up to its first 1ooo hours quite well, considering with no major repairs required, apart from the usual wear items like brake pads, bungee chords, rubber replacements etc.

 

 

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This seems like a lot of work!!

 

 

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Started work in Feb this year, only about half way through at this point. Hoping to have it airborne by spring, but sadly i am only working on it on weekends.

 

 

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The dash is still in its flat uncut phase, still planning locations for warning lights and switches and will be laser cut when done, in a few weeks.

 

 

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Started work in Feb this year, only about half way through at this point. Hoping to have it airborne by spring, but sadly i am only working on it on weekends.

Hi Rob, Thanks for the update on the 1000 hour check.

 

I can understand that you would like a new colour scheme but I also have to say that I'm sorry to see the old colour scheme go: I really like it.

 

 

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Thanks for the thorough report Ultralights- my landing gear and a fair few other items similar to yours were done at 700 hrs at about 2 1/2 years from new, 2000 plus landings with students means more vigilant maintenance, ACF50 anti corrosion every 12 months and regular washing with Taipan aircraft wash helps with the corrosion. A corrosion repair was also undertaken at around 500 hrs which really was more a paint issue ex factory but presented like filoform from surface inspections. but with my 1000 coming up in the near future I value your findings.

 

The elevator trim hinges were replaced recently, aileron bushes and approved repairs to the upper firewall bracket supports due to cracking and the nose leg lower guide bracket (common) were also done.

 

Overall I too am very happy with my Sav S

 

 

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Hi Ultralights

 

It is good to see that you are doing such a thorough job on your Savannah VG inspection. The corrosion on your aircraft is typical of what one might find on an aircraft poorly protected against a highly corrosive environment. A pity this was not done prior to assembly. We always advocate properly prepping and priming with strontium or zinc chromate prior to assembly for any aircraft to be used in a coastal area. We have a flying school in our coastal area and they end up having to refurbish aluminium components on Cessnas for the same reason. Always keep well out of that salty air zone along the break line when flying coastal. It is fun but very very costly in maintenance. The gear corrosion is common and occurs because the alloy is stressed at manufacture. It is precisely at the stressed bends that corrosion sets in. It penetrates very quickly to the interior where molecular changes take place that are not visible to the eye. To retard this process the same protection needs to be applied to the exterior from the start. Prep, prime and Finnish with 2K.

 

Replacement of rubber hoses as you say is mandatory at 5 yrs for the Rotax parts and 6 yrs on the rest of the airframe. I will always recommend 5 yrs for all. In fact the Rotax supplied rubber parts are of better quality than those supplied with the kit. We find the Goodyear J30R7 spec fuel hose better quality. PM me for the latest Savannah Maint manual with your email address.

 

Things like missing rubber gear mounts should have been picked up way sooner at pre-flight and earlier inspections. Spruce have a better quality bungie Mill spec fresh stock P/N 06-01132.

 

Also have a few mods you might be interested in.

 

John

 

 

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gday, the rubber mounts on the undercarriage are just the flat pieces that sit above the flat part of the undercarriage piece, the round larger ones on the outside edges are fine and have never moved.

 

I am treating all the corroded areas with Alodine 1200 before priming with a 2 part polyaramid resin strontium chromate primer. A few smaller corrosion repairs done about 2 years ago still show no sign of the corrosion returning.

 

 

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gday, the rubber mounts on the undercarriage are just the flat pieces that sit above the flat part of the undercarriage piece, the round larger ones on the outside edges are fine and have never moved.

I am treating all the corroded areas with Alodine 1200 before priming with a 2 part polyaramid resin strontium chromate primer. A few smaller corrosion repairs done about 2 years ago still show no sign of the corrosion returning.

It seems you have a lot of corrosion. Are you close to the sea Ultralights?

 

 

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It seems you have a lot of corrosion. Are you close to the sea Ultralights?

corrosion wise, Unfortunately yes. not to mention a lot of low level coastal flights, including the V1 at 500ft off the coast of Sydney. and i have been know to fly long coastal trips, from Sydney to Kempsey, and just as far down the south coast. at 500 to 1000ft.

 

 

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about time for an update, the 1000Hr inspections, overhaul and upgrades continue, fortunately, or unfortunately, we have had a great ski season, and i have spent to many weekends at the snow and not working on the aircraft.

 

Some time ago, i removed the lift strut attache plates due to suspected corrosion, and sure enough, after removing them, i have found some corrosion, noting to deep, but enough to warrant repair, due to the critical nature of these components to flight safety.

 

FullSizeRender%20%284%29-L.jpg

 

FullSizeRender%20%286%29-L.jpg

 

these are both sides of the upper and lower lift strut plates, on the right hand wing. the Upper piece, with the bevelled edge, also has a nice deep gouge across its width, im not sure how it got there, as i could not see anywhere it was resting on anything..

 

the material is 2024-T3 according to a rockwell hardness test and 0.110 inch thick.

 

new parts have been manufactured using 7075-T6 material of 0.125 inch thick, as there was nothing limiting its thickness, and 7075-T6 while more brittle is significantly stronger than 2024-T3

 

the lower plate was remade of 2024_T3 of 0.125 thick, but machined down to 0.110 where it nests between the plates of the lift strut itself. so at its thinest point, the total thickness is 0.015 thicker, and a mix of 70705-T6 and 2024-T3 material.

 

FullSizeRender%20%285%29-L.jpg

 

FullSizeRender%20%282%29-L.jpg

 

hopefully a good alodine treatment and chromate primer will keep new corrosion at bay, i think its caused by moisture trapped between the plates of the wing and lift strut joins.

 

 

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Now its time for the tail feather work, just basically replacing flight control bushes, rewire the electric trip tab with lighter and shielded specific aircraft wire, and rerouting the wire to avoid it resting on sharp edges.

 

once removing the elevator to get to the central hinge bolt and bushing, i found serious wear of the bushing and bolt, the bushing itself was worn completely through in 2 places, and then wear is also significant on the bolt in the same areas.

 

bolt is in this area.

 

FullSizeRender-L.jpg

 

also i found evidence of movement between the hinge bracket and rear spar of the horizontal stabiliser. this will be fixed by replacing the pop rivets with substantially stronger Cherry max type rivets.

 

 

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Hi Ultralights

 

The bushing wear you describe sounds familiar. I've just had finished the yearly permit to fly inspection, found significant wear on the rudder bushings. Holes were OK, reamed them out slightly oversize, new bushings machined. 325hrs TT.

 

 

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One place I am interested in is the pulleys on the rudder cables under the seat. The bush seems to turn on the bolt after deburring and iniitial installation, but strangely there is nothing to stop the bush binding slightly and turning the bolt in the mount holes instead. Rob, have you inpected these holes for wear?

 

 

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no, i havnt inspected the rudder pulleys, but i will when i get around to working on the lower fuselage in the next week or so. fortunately the rudder bushings on my aircraft we in pretty good condition.

 

actually, tomorrow ill be heading back to the hangar, so ill have a quick look at the rudder cable pulleys..

 

oh, and one last thing, i found the horizontal stabiliser foam spar has become the home to a few mud wasp nests.. so a small mod will be to add some fly screen to cover the lightning holes on the rear aluminium spar.

 

 

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no, i havnt inspected the rudder pulleys, but i will when i get around to working on the lower fuselage in the next week or so. fortunately the rudder bushings on my aircraft we in pretty good condition.

actually, tomorrow ill be heading back to the hangar, so ill have a quick look at the rudder cable pulleys..

 

oh, and one last thing, i found the horizontal stabiliser foam spar has become the home to a few mud wasp nests.. so a small mod will be to add some fly screen to cover the lightning holes on the rear aluminium spar.

With my build we put some left over decal sticker over those holes to seal it up, very easy as it has it's own adhesive so basically all that was needed was to trim to size.

 

 

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better give an update on the rudder cable pulleys, both were fine, bushing are ok, very little sign of wear, both spun freely and had even wear marks, well, where the cable runs, evenly around the entire pulley.

 

On the Elevator, i found the hinge pin bolt on the right hand side is showing signs of wear, once the bushing had work through, the wear continued into the bolt itself, so i am going to change this plate/bolt assembly. has anyone done this before?

 

image-L.jpg

 

image-L.jpg

 

i am thinking of a way to modify the end plastic fairing to allow access to this bolt more easily and allow replacement of the bushings at say, every 600 hrs, to prevent the wear into the bolt itself.

 

 

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Rob, I had my head in a CH 701 belly the other day and I noticed two alum straps abut 1.5" wide that run back ino the tail directly from the seatbelt shoulder strap attach points.

 

This simple mod may be worth considering as I noticed on a crashed Savannah Bingo that these belt attach points had been severely stressed.

 

Obviously they had done their job ( both occupants survived the high impact nose down crash) however any Xtra strength here could be a good idea........

 

And on the subject of the solid rod throttle linkages....in this same crash which had severe frontal crushing, the throttle rods were pushed back into the occupants chests breaking ribs in both. The large circular knob on the throttles should always be used as otherwise chest puncture wounds could have been the result..................Maj.....

 

 

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I am always suspect of modifications that reduce stress load on the aircraft and transfer that load onto the occupants! "Obviously they did their job", especially not killing the occupants.

 

 

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I am always suspect of modifications that reduce stress load on the aircraft and transfer that load onto the occupants! "Obviously they did their job", especially not killing the occupants.

Good point Rank...however had the impact been just that more severe the attach points could well have failed with bad results....they were very close to doing that...no harm in making them stronger by taking the loads back into the tail as the 701 has done. I don't see that seatbelt attaches should fail in any circumstances.........Maj...

 

 

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