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Roger Lee

Spring into action on reduced radius hose

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Just an FYI,

 

I have been doing a little experimenting the last few years with springs in hoses to stop a warm hose that has too much bend in it reduce its radius and reduce its flow. The Flight Design uses 2 springs on the top of the engine in the 17mm coolant hoses. I recently experienced high oil temps up at 250F during climb which I never had before on a CTSW. The culprit hose was the oil hose that comes off the top of the right side oil cooler then does a 180 degree turn back under cyl. 1&3 and back into the oil pump housing. This hose when warn has slowly reduced its radius over the last year.

The fix:

I just unscrewed the clamp on the hose fitting on top of the oil cooler and slid a 1/2" O.D. spring into place at the bend. I also opened the air intake in front of the radiator on the bottom lip by about 1". The test flight was performed at 90F OAT. A hard slow climb was then performed for 5K'. The oil temp never got over 230F. This was a 20F reduction at a max temp and the cruise temp was only 215F-218F on a nice hot day. These two minor mods made tremendous difference.

There is one more place that the oil hose on some LS and SW models may get a reduced radius oil hose. That is the hose that comes off the bottom of the engine and "S" turns back up and into the oil tank. This hose can be too short making the turns too sharp and over time they may reduce down. A spring add in this location can be a big help too.

 

See video.

 

p.s.

The fuel hose on the CTLS up at the fuel sight gauge comes out of the wing and makes a very hard 90 degree turn to its fitting in the "A" post. I have found several CTLS hoses at this location crimped almost off. You can insert a 3/8" spring in the hose at the bend and it will maintain its full radius and good fuel flow.

 

Hope this helps..

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p.s.

The fuel hose on the CTLS up at the fuel sight gauge comes out of the wing and makes a very hard 90 degree turn to its fitting in the "A" post. I have found several CTLS hoses at this location crimped almost off. You can insert a 3/8" spring in the hose at the bend and it will maintain its full radius and good fuel flow.

 

Hope this helps..

 

You can also take a dremel to this area and bore out the spar tunnel a little bit more. The spar tunnel is purely decorative, so it's safe to chip away at some of the material so that the hose has a more gradual turn.

 

As for the outside edge of the hole, that too can be slightly bored out to accommodate things like hose or fuel injector clamps, but caution must be used to keep gentle sloping radiuses. This area isn't critically structural, but you don't want cracks starting from stress risers.

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I have Dremeled all the LS fuel hose holes much larger, but the hose insert has to turn a little too sharp on the left side. Sometimes it works okay and sometimes not. The spring makes all your worries non existent and it won't collapse later like this one I have now did.

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Hi Doug,

 

The hole for the fuel hose is already there. Just use a Dremel with a sanding disc and enlarge it by about 1.5 times more and this will allow the hose clamp to easily fit back in place when pushing the wing back in place.

As far as a pic you'll have to wait until another LS comes in that needs a wing pull.

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What does FD or Rotax say about the addition of the spring? Is there a call-out on the spring specs, such as length? Can they move in the hose, especially if they are somewhat undersized and can slide readily, or will the hose bend always keep them exactly in place? Are these hoses inch per your video commentary or are they metric? Any approval needed to modify the spar tunnel or just cut away?

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FD already uses springs in the 17mm coolant hose. No special length, just enough to cover the affected bend area. Springs can be cut down if need be. Length isn't a huge problem and if it is a little longer no big deal. It just needs to be long enough to keep the area of reduced radius at bay. When hoses get changed they are not the exact same hose and some hose will be stiffer and keep its shape better than another hose MFG. FD had some reduced radius issues in the SW's on the oil return line and back a long time ago advised some to check this hose when temps increased. Your only options would be to repolace and reroute the hose or add a spring. Hoses on the FD and other aircraft are usually a mix of metric and American standard. The springs are a fairly close fit  and a bend will hold them in place and they will not move. The oil hose is 13mm or 1/2". 1/2" spring is a snug fit. FD doesn't use springs in the fuel or oil lines from the MFG. This is done on your own, but not using them in certain specific applications when needed may not leave you any alternative especially in the oil line in the video. 

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Hi, Last Monday, I had to fly about 5.5h and it was quite hot in Spain, comming home, ground temp was 36 or 38º, oil temp whent up quickly and I had to low revs to 4600, flaps to 0º and change pitch to keep the engine run with less load, climbing really slow (200feet/m) until 6000 feet, OAT 22º, then I could go faster. Anyway outside temp was lower, I was always in the green to yellow limit, sometimes, yellow alarm came.

 

Reading in the forum i found different ideas to improve engine cooling and I am applying them.

 

1. Clean radiators (outside and cells) they have some dust.

2. repair some ratiator cells that are bent due to some chips.

3. Align radiator, they where (both are welded toguether) with a bigger angle than should be.

4. Cut with a dremel the low cowl lip to allow more air flow.

5 I wanted to put springs in the oil tubes my after checking my tubes, there is no hard curve ( I will post a picture)

6 I saw a post with some fiber spoilers near the exhaust and they said it worked great, (anyone has more info?)

 

What do you think about my ideas to improve cooling? Any other suggestion?

 

Thanks

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I didn't like the sharp 180+ degree bend in the oil line from the oil cooler to the oil pump when I did my rubber change back in 2011 but my temps are OK so I didn't add springs here. Springs were added to the coolant hoses.  Ever since doing this, I've thought about using external springs on hoses.  Haven't researched this but imagine external might be a little less effective for reducing kinking as internal.  No restriction to flow if done external.

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I have not had any problems that required springs to correct, but I wouldn't hesitate to do it if needed, since Roger's already done all the testing!   :D

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Hi CTSpain,

 

You're on the right path doing the things you have listed. I do see you have different oil hoses and they aren't in fire sleeve so checking for a reduced radius hose should be easy.

I don't see the hose that comes off the top right side oil cooler that goes into the oil pump? I may be going blind or is your hose set up different?

 

Prop pitch will cause high oil temps quickly. You should be able to see approximately 5600-5650 rpm at WOT if you have a ground adjustable prop and it looks like you do. If you get less than 5500 this is contributing to the higher oil temps.

 

 

 

 

p.s.

I do find the hose that comes off the oil cooler on the right side that does a 180 degree sweep and then into the oil pump is most often an offender for high oil temps on the US planes. I have added springs to 6 planes oil hose here and everyone's temps went down. The hose by itself doesn't crimp off, but when hot flexes to a reduced radius which slows the oil flow. Any time you slow out oil flow the oil temps increase.

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Thanks by your advices.

 

I already finished steps 1 to 4, this is the cowling after cutting (https://www.facebook.com/photo.php?fbid=866124903425116&set=pb.100000828428662.-2207520000.1436255597.&type=3&theater)

 

Roger, my prop. is adjustable in flight (Kaspar) that's why I reduced the pitch when climbing to avoid oil go hot. In the minimum possition I can reach about 5700 rpm WOT.

 

About oil hose, that you suggest to modify, as tomorrow my rotax mecanic has to come to the hangar, I will talk to him about how to improve it.

 

Thanks again.

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Did cutting the cowl actually help?  I'd think you'd get more effect from just making sure the rubber skirt under the opening is folded upward instead of downward.  That made a difference for me.

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I have made my opening larger too. Sometimes, but not every time a few small tweaks make an improvement over just a single tweak. The other day I flew from 1700' to 7500' on an OAT day of 90F+ and never saw over 230F on oil. That was zero flaps at 500-800 ft/pm and WOT. Once level at 7500' oil temp dropped to 218F.

 

Both CTSW's in that flight ran approximately the same temps.

 

The single biggest drop in temps I have seen is keeping the oil lines fully open. When I added my springs in the oil line that comes off the top right side of the cooler and back into the oil pump housing (180 degree bend) dropped my temps 20F.

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I have made my opening larger too. Sometimes, but not every time a few small tweaks make an improvement over just a single tweak. The other day I flew from 1700' to 7500' on an OAT day of 90F+ and never saw over 230F on oil. That was zero flaps at 500-800 ft/pm and WOT. Once level at 7500' oil temp dropped to 218F.

 

Both CTSW's in that flight ran approximately the same temps.

 

Where and how did you reshape things, and how much material did you remove?  I don't really need this, I'm just curious.

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Most of mine came off the bottom lip, but a little all around. You can also loosen the radiator mounts and move the cooler a little left or right to be better centered also.

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I cutted all from bottom lip, about 2cm that I think where blocking air but being sure there is still enough fiber around to keep that part stiff.

 

I cutted at home just using a dremel, before cutting, I used a 3m tape to mark the correct line to follow.

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Changes tested Yesterday, OAT 22ºC (not hot) and not big differences, climbing 150Km/h, oil went to 105ºC and yellow alarm. All the other time, was fine.

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Hi Ctspain,

 

105c is only 221F and that isn't hot. That's a really good climb temp. Many would wish they had that climb temp. The yellow oil temp alarm should be coming on around 230F (110c) and I wouldn't worry up to 245F (118c) so long as it came down in level flight. I would think the average user is between 210F-240F in a climb at take-off.

 

 

 

Quote:

"Hi, Last Monday, I had to fly about 5.5h and it was quite hot in Spain, coming home, ground temp was 36 or 38º, oil temp went up quickly and I had to low revs to 4600"

 

37C (99F) is fairly hot and you may easily see 230F-235F in a take-off climb depending on factors like aircraft weight, prop pitch, flap settings and speed and OAT.

 

 

 

p.s.

The Rotax engine runs leaner  around 4500-4800 rpm than when over 5000+ rpm. The higher rpms especially WOT is a richer setup. Rotax made sure at WOT that it was richer to help reduce the chance of detonation in some circumstances.

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Thanks Roger, I will change the yellow alarm to avoid worrying so early :)

 

Dynon has that, you see alarms and lights and think you're going to crash, analog instruments, sometimes you even dont realize about it.

 

 

I was testing the engine because today I wanted to fly to Mallorca, and Island 2h+2h over the sea and I wanted to be sure engine was perfect. I felt some strange vibrations in rudder peddals and I cancelled the flight, I think it is nothing, mechanic checked engine last week and was fine, and I asked copilot if he could feel but said no. Maybe it is an aerodinamic thing, not sure. I need to check everyting again. 

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CTSpain, during what conditions did you notice the rudder pedal vibrations?  What was power setting for engine - was this full throttle?  What was air speed when vibration occurred?

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CTSpain, during what conditions did you notice the rudder pedal vibrations?  What was power setting for engine - was this full throttle?  What was air speed when vibration occurred?

 

I noticed that in last 2 flights, after about 1h flying, 1st time 5000RPM, about 6000 feet, 200 Km/h air speed. 2nd time, also about 1h flying, 160Km/h, about 3000 feet. soft clyimbing, about 250feet/m

 

It was not a significant vibration, I just could feel it on peddals, even I gave control to copilot, relaxed and took out feet from pedals and I didnt feel it.

 

 

That comes from about 1 month ago, OAT was 7ºC, raining, cloudy, we put carb heat late and I think we had carb ice, no power problems but strong 1second power loss happened about 4 or 5 times in 30m and we landed to check, after talking many people, we checked float bowls and we found an small water drop there. Mecanic said probably more water was there and each time we had that power loose, engine was taking some of that water trough jets. We cleaned it and everything seems was fine. I flow about 7h after that but sometimes felt that vibration (really small).

I have 2 Rotax mecanics, 1 is English and the other one Spanish, English say maybe I have water in fuel tanks (I checked tanks and gascolator and cant find anything) The other said water came from icing.

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