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Broken Throttle Springs

alexe

Well Known Member
Hi,

I have experienced three broken throttle springs now in 80hrs of flight. They are the new springs (Vans part SPRING-00002, McFarlane part 6822) made by McFarlane for the vernier throttle. See service bulletin 14-12-16.

The springss were installed by hand, so it could not be nicks caused by pliers.

Ken at Van's support was not aware of any issues with the new springs. I also have an inquiry in to McFarlane.

Anybody else out there having problems with the new springs breaking?

Thanks,
Alex
 
A few questions.....

Care to share where the breaks occur? Photos? Wear-through or fracture? Have you filed incident reports with Van's all three times?
 
BigJohn,
I would love to share, but unfortunately the springs departed the plane through the bottom of the lower cowling. I have no idea where/how they actually broke. I did not report the first one since I figured it was just an isolated incident. After losing two more, I'm a bit concerned. As I said, the latest incident (with both springs departing) was reported to Van's.
Alex
 
I had the the right side spring disappear and blame it on improper installation on my part. The lower grommet was also gone.
 
I broke two nonstandard springs (.ie. Harbor Freight) early on at about 40 hours. I think it was due to over stressing when I shortened them and formed a new end hook. Since then I have 370 hours on some I got from Home Depot with no issues.

BTW did you notice any difference in throttle response when they broke. I didn't. I picked it up on preflight.
 
RFSchaller, I did not notice any throttle response changes with the springs missing.
Alex
 
Ten more hours on the plane and another broken throttle spring. That's four (Spring-00002) springs broken since the new ones came out. Am I the only one suffering from this?
Thanks,
Alex
 
Alexe - we had the same problem on our ELSA RV12 that we built ourselves. We did put the new springs on as they came with the Rotax kit. Here's the history and what we did: (all during first 80 hours)

One spring broke - passenger side. It was still hanging on. Ordered 2 new ones from Vans and replaced the broken one

In a short time - spring missing on passenger side - replaced it again

In another short while - spring again missing on passenger side - ordered 2 more from Vans.

This time - we safety wired the bottom of the spring, and bent the top a little more to keep it on

Our conclusion - other than the first one - we think they were just falling off and not breaking. The last one we put on with the safety wire has not fallen off and seems to be working great.

Never had a problem with the pilots side spring.

Called McFarlane and they said it is probably due to vibration and we should balance our prop. We plan to do that soon.

Hope this helps.

Bob
 
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Broken throttle spring (again)

Ten more hours on the plane and another broken throttle spring. That's four (Spring-00002) springs broken since the new ones came out. Am I the only one suffering from this?
Thanks,
Alex

No, it doesn't seem that you're alone. A buddy of mine had the passenger side spring (McFarlane 6822 or Van's 00002 spring) break last week and mine broke yesterday (McFarlane 6822 or Van's 00002 spring). Again, the passenger side. You'll notice that I posted on this thread back in December with a missing spring and missing grommet, again, on the passenger side. I attributed it to improper installation at that time, but now I'm not so sure. I'll notify Van's using their reporting mechanism.
 
If you have difficulties such as the issue reported in this thread remember to use the standard (official) process detailed on page 17-1 in the current maintenance manual. The data is valuable in determining if changes need to be made.

The preferred method of reporting Pasted below

Include your name and builder/serial #, flight hrs at the time of the problem was discovered, which spring(s) broke and where the break occurred (if any portion of the spring was still attached to the carb.), and any other details that you think might be relevant. Also please include details regarding the following to better help with the investigation.

1. Report whether checks have been made to confirm there is no more than .1 degree difference in pitch between the two propeller blades.

2. Report whether a dynamic propeller balance has been done.

3. Confirm that the carb. sync procedure has been properly completed within the previous 100 hrs using vacuum gauges.

4. Report whether the airplane is operated for extended periods in a rough rpm band. (Many 912s seem to run rough in the 2500-3500 range, sometimes to the extent of shaking the carbs enough to even vary the mixture and compounding the problem.)

5. Report whether the engine is idled below 1800 RPM (other than for a few moments during startup and shut down) for extended periods.



FEEDBACK
To maintain the highest level of safety the FAA requires and Van?s Aircraft Inc. requests notification of any safety of flight issue, service or maintenance difficulty that could compromise airworthiness of the RV-12 aircraft. A feedback form is provided in the Supplement section of this manual.
(It is also available

A valuable description will include:
? Specific flight condition if applicable.
? List of the parts identified as affected by the anomaly.
? Description of the apparent condition of the parts prior to the anomaly (de-burred,
primed, modified, etc.)
? Statement as to whether the aircraft has remained within the operating limitations defined in the POH.
? Brief description of the type and frequency of aircraft use (may include; runway conditions, flying conditions, storage methods, etc.)

REPORTING METHODS
Mail to:
ATTN: RV-12 Safety Alert
Van's Aircraft, Inc.
14401 Keil Road, NE
Aurora, OR 97002 USA

Fax to:
'RV-12 Safety Alert' (on cover page)
503.678.6560
Hours: 24 hours per day

E-mail to:
'RV-12 Safety Alert' (in subject line)
[email protected]
 
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Throttle spring break

Per Scott's note on this thread, I'll be putting in a report to Van's on this but thought I'd mention it here.

Installed Vernier Assist Throttle Control 3/2015 obtained from Van's with the new springs provided. At 107 hours, the right spring failed (noticed it after flying for several hours just before last flight of the day during a quick peak in oil door). Don't specifically remember looking at it at beginning of the day but I generally take a good look through door before the first flight of the day and obviously didn't notice anything. Throttle moves back and forth just fine without it so I wasn't even noticing an issue flying. If it had failed on left side, I might not have detected it until next oil change. Left side spring looks fine BTW.

Appears to be a relatively clean break just at the bottom of the coils. I'll hang onto it in case Van's wants to inspect it themselves.

15p6a09.jpg
 
Make that two

Found my right hand one broken over the weekend. Identical to the photo posted by Brent - snapped in exactly the same location. About 60 hours in service. Discovered recently that the prop had been installed without careful attention to equalising pitch. There was almost 1? difference! Now fixed but that may have been a contributing factor. Carbs have been well balanced from beginning (115 hours TT). Seems that more breakages are occurring on the right-hand side. If so, there has to be an explanation, but hard to imagine what it could be.

Like others I found that the aircraft still performed satisfactorily broken spring. Quite smooth at idle and above 5000 but noticeably rougher in the mid-rev range.

Jack
 
I called and talked to McFarlane. They told me it is usually the passenger side spring that breaks or falls off. They also said it could be due to propeller or engine vibration.

We had our propeller balanced, and have not had a broken spring in quite awhile. We also safety wired the bottom of the spring, and bent the top of the spring a little extra.

Bob
 
I put in weak springs from Home Depot Four years ago after my frustration with throttle creep on the originals and one pair of HF springs that broke. They give vey smooth throttle action and no creep. I had to cut them to size. As I recall they are 0.375" coil and0.035 wire diameter.
 
I purchased Century Spring part number 5553. Coil Diameter: 0.375, wire diameter: 0.034, length: 3.63 inches, with extended hooks on both ends. I cut the springs shorter and formed hooks on the cut ends. My new springs have a fraction of the tension of the original springs. With the friction knob completely loosened, the throttle does not move unless the engine is running. Then the throttle opens with the help of vibration. These are the 4th Century part that I have tried and have finally found a winner. Century Spring has a $50 minimum order, so I had to buy many more springs than I will ever use.
At first I was apprehensive about experimenting, concerned about a spring breaking. But with all of the reports broken springs with no noticeable affect, not to worry.
 
I bought new springs from the local hardware store. Springs are full coils for entire length of spring. Wire diameter and OD are very similar to original springs. I had to shorten overall length and bend a new loop end being careful not to make sharp 90 degree angle to reduce stress riser. Spring wire can be bent cold without addition of heat for tempering.
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2u4o604.png
 
I didn't see anyone here mention that the throttle springs have to be installed in accordance with the instructions that come with them -- i.e.. the hook has to be put into the eyes at each end as shown in the pictures or instructions.

EBB
 
Bruce,

I'm not sure Iget what you're point is with regard to spring orientation. Is there something critical I'm missing?

Rich
 
The McFarlane springs come with an instruction....and a picture I think...that requires they be installed with the open end IN at both top and bottom. But I am not at the airplane now so I may be mistaken about the orientation....so just look at the picture or read the McFarlane instructions.

EBB
 
Old springs with vernier assist throttle

Here's something interesting. Had a flight I needed to do after spring broke. Remembered I still had the old springs from original throttle. Wondered how they might work with new vernier assist throttle. Installed them and did a ground run - worked fine. No creeping or need to constantly tighten friction nut. Went flying and very happy with result. I did tighten the friction nut a whisker but not sure it was necessary. Operation was virtually identical to that with new McFarlane springs. Easy to use and stayed exactly where it was set. I plan to leave old springs in place. They are robust and unlikely to break and I still have the advantages of ther new throttle.

Jack
 
Per Scott's note on this thread, I'll be putting in a report to Van's on this but thought I'd mention it here.

Installed Vernier Assist Throttle Control 3/2015 obtained from Van's with the new springs provided. At 107 hours, the right spring failed (noticed it after flying for several hours just before last flight of the day during a quick peak in oil door). Don't specifically remember looking at it at beginning of the day but I generally take a good look through door before the first flight of the day and obviously didn't notice anything. Throttle moves back and forth just fine without it so I wasn't even noticing an issue flying. If it had failed on left side, I might not have detected it until next oil change. Left side spring looks fine BTW.

Appears to be a relatively clean break just at the bottom of the coils. I'll hang onto it in case Van's wants to inspect it themselves.

Discovered that the left throttle spring has now failed as well. That is both R & L failing in about 100 TACH hours of use. Posted a followup report to Van's engineering

 
Springs typically break from excessive vibration and or the spring metal hardness is too hard which makes them brittle or they are being over extended. If McFarland springs show a break pattern then a call to them from everyone would be warranted to let them know. It can't get fixed if no one knows. The Rotax springs can break, but isn't common. Maybe McFarland needs a different alloy metal spring.
 
With all of that tension on them, no wonder they break. I love my modified (shortened) Century Spring part number 5553, no throttle creep.
 
Just had annual on RV-12
Total 101.5.
Left spring broken.
Replaced with McFarlane 6822 springs, as only ones we had available here.

John
 
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