What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

New Springs Recall? 2nd Skyview? Throttle?

cactusman

Well Known Member
So I got this cryptic call that some springs broke on the RV-12 going back to OSH and not to use the new ones that were sent to me...not sure why new ones were sent to me, but I did get the new multi-colored springs in the mail a day or two later....SPRING-00002.

Now I have the factory springs still so I am not yet at the stage where this is a big deal, but I have been waiting to see a newer revised bulletin or something about the newer replacement of the replacement springs, but see nothing?

What am I missing?

Also - speaking of this spring issue - has that set back the vernier throttle rollout thru Vans?

Also also - anyone hear anything about the dual Skyview plans, kits or retrofit?
 
So I got this cryptic call that some springs broke on the RV-12 going back to OSH and not to use the new ones that were sent to me...not sure why new ones were sent to me, but I did get the new multi-colored springs in the mail a day or two later....SPRING-00002.

Now I have the factory springs still so I am not yet at the stage where this is a big deal, but I have been waiting to see a newer revised bulletin or something about the newer replacement of the replacement springs, but see nothing?

What am I missing?

Nothing

The springs and Throttle controls are supplied by McFarlane. They are the ones working on the problem, so you would have to direct that question to them.

Also - speaking of this spring issue - has that set back the vernier throttle rollout thru Vans?
No
The vernier throttle has been shipping with kits for use with standard springs until McFarlane releases an exceptable replacement.

Also also - anyone hear anything about the dual Skyview plans, kits or retrofit?

As reported previously, it is being worked on.
An announcement will likely be made when it is available as a kit option.
 
You can order it from Vans for 215....

I cannot find it on their website, but the phone person found it - ends with a "12V" and should be described as a Vernier Throttle.
 
You might want to confer with Governor Dave Valcik, I think he can give you the part number from McFarland so you can order it direct. I don't think it costs that much. I have used this control before and it is a good upgrade, although I never really had a problem with the old one. (one of the few)
 
There has been some discussion regarding spring failure. I used some Harbor Freight springs that I had to cut down. The work hardening associated with forming the new hooks caused them to break. Interestingly enough I did not notice any throttle control issues as some have warned about. I found the failures on preflight. About a year ago I put in some springs from Home Depot that did not require cutting down. I have been very happy with them, and they eliminated throttle creep.
 
There has been some discussion regarding spring failure. I used some Harbor Freight springs that I had to cut down. The work hardening associated with forming the new hooks caused them to break. Interestingly enough I did not notice any throttle control issues as some have warned about. I found the failures on preflight. About a year ago I put in some springs from Home Depot that did not require cutting down. I have been very happy with them, and they eliminated throttle creep.

What was the HD-(Spring ###){aircraft}Dept Suppy Center nomenclature you purchased??

This is a "must share" with McFarland (sp) to solve their problem. I'm somewhat mystified why getting functioning spring is such a problem?????
 
Just as a follow-up I did call and tried to order just the 12Vernier throttle from Vans and was told that everything is on hold because of the springs problem. Not sure if you can order it still from McFarlane and use the original Rotax factory springs.

Also, the center panel with the cut-outs already done for the AP-Knob kit is also on hold. (i was going to simply buy that with the AP knob kit since I had to pull the throttle anyway.....)

FYI FWIW.
 
Ric,

I honestly don't remember the spring part number. I just bought a few and tried them for the best fit. After 30 years and 4 home builts I have become used to experimentation.

Rich
 
The McFarlane is not a true "vernier" as commonly seen in airplanes. It still goes in and out based on how much friction you set with the friction knob. If the springs are too strong it could still creep, if not strong enough the vernier action may not be satisfactory. I would not use any springs except those furnished by the throttle maker or Van's if you want the best operation of this throttle.

I have the unit and it works well enough, and it is better than the original throttle, but is not perfect.

If you already have a McFarlane, then SB 14-07-23 gives all the information needed to determine if your springs are good or bad.
 
What next?

These little springs do work. They are designed to take you to full throttle if your linkage fails. If you are 200 feet off the ground and climbing, you will never notice...a good thing for sure. However, once you reach altitude and level off, RPM's will red line. Couple of choices now: climb some more or cut the fuel and glide. Though I have yet to read any emergency procedures for this event it will become one very quickly. You cannot remain in level flight at full throttle...nor can you descend.

Best as I can figure, the plan was to allow you to climb and climb while maneuvering over an airfield of choice. At that point, kill the fuel and dead stick it home.

Obviously, this scenario has taken place or the springs would not exist. Why are there no emergency procedures to follow AFTER? Not something you can practice, but then neither is an engine fire but it's nice to read about ahead of time.
 
My first homebuilt used a Continental O-200A. I put a spring on the throttle and the linkage failed on the ground during taxi. I used the mixture for power control to limp back to my hangar. Since the ROTAX has auto mixture this wouldn't be an option.
 
What if you are at full open throttle with the broken cable scenario but then also open the starting carb ("choke")? Would that make the mixture so rich it would reduce power?
 
These little springs do work. They are designed to take you to full throttle if your linkage fails. ..snip..

Obviously, this scenario has taken place or the springs would not exist. Why are there no emergency procedures to follow AFTER? Not something you can practice, but then neither is an engine fire but it's nice to read about ahead of time.


I for one, would like to know what Van's Aircraft suggests for the situation you describe (the spring taking one or both carbs to full throttle).


With one carb at full throttle, (if noticeable), I would think you would want to take the controllable carb to full throttle, climb to maintain the engine RPM below 5500, find the nearest airport, and then kill the fuel or kill both ignitions. Then deadstick it in.

Anyone have an opinion on the correct procedure to follow? Anyone have an opinion if killing the ignitions is detrimental to the ignition modules?
 
One side of the engine at full throttle and one at much less will probably make for a high vibration situation. So likely full forward on the working cable/carb for the climb. ROTAX recommends as a normal practice shutting down at low rpm, but this would only be "once" and is probably the least of one's worries at that time! I still wonder about use of the choke in that situation to go over-rich.
 
I still wonder about use of the choke in that situation

Bill!. Climb to altitude, go full power and pull the choke handle. Please advise! Thanks! You are my hero...lol

Pete
 
The plugs would probably be OK for the short period of use to get on the ground safely. Any way you look at it it would not be good.
 
I wonder if using the choke might dilute the oil, wash the lube off if the cylinder walls, and wind up causing more trouble than it is worth. What might be great is a set of springs that would deliver half throttle with cable failure. Something around 4000 rpm. You could still cruise to a landing strip, where you could cut the ignition when you knew that you had the field made. I think that it could be built with proper springs and maybe adding a link. The carb balance may not be perfect, but it would sure beat wide open, or fully closed. Just a thought!!

Tom
 
I actually think wide-open is the way to go simply because of the take-off scenario. I am just surprised that none of the manufacturers that use this particular engine have incorporated such an event into their emergency procedures. It's not a fire, but it is enough of an eye-opener that one would prefer not to be inventing and resolving at the same time. Let's see...should I pull the choke? pull the ignition? pull the fuel handle? ****, I'm redline.

Runaway Trim merits an emergency procedure. Runaway Throttle deserves no less.
 

I for one, would like to know what Van's Aircraft suggests for the situation you describe (the spring taking one or both carbs to full throttle).

This is probably a question for Rotax rather than Vans, but it would certainly be useful to have the recommended actions included in the POH.
 
Why Is The Spring a Single Point Failure Element?

If a broken spring is a safety of flight item why is there not some redundancy in this area?

It sounds like the rigging should be modified to incorporate a second spring or some other means of maintaining throttle control in the event the spring breaks.
 
Last edited:
throttle linkage break/spring break

If a broken spring is a safety of flight item why is there not some redundancy in this area?

It sounds like the rigging should be modified to incorporate a second spring or some other means of maintaining throttle control in the event the spring breaks.

When the throttle linkage (i.e. cable) breaks, no getting around it, you go wide open on the broken side and your only option would be to go wide open to balance things out, or shut the engine down.

When the spring breaks, it might be a bit different, depending on how well the cable could push the throttle without the springs help--if not capable of pushing all the way, it may still get it part of the way to allow limping home, and you could still pull back to idle.

I suspect someone could test the behavior by disconnecting the spring and observing how things behave with and without the engine running.
 
My understanding from MUCH discussion

earlier on this subject is that if a CABLE breaks, the spring pulls the throttle to full power. If the SPRING breaks, the cable can, more or less, maintain the desired setting though it may not provide 100% power. Not, IMHO, a big deal.
In the event that the cable breaks. and one carb goes to full power, you've got to go full throttle to keep the carbs balanced. In that case. you shut off the mags, keep the prop windmilling, and turn the mags on whenever a burst or power. Much like WWI rotary engines with the coupe button to kill power.

Wayne 120241/143WM
 
Spring failure

I recently (not intentionally) found out what happens when the spring brakes on one carb. This is 912 engine (not ULS) in a Murphy biplane (not RV12). I started a take off roll but the engine was rough and would not develop take off power. Only had 4400 RPM. So if one brakes on the ground you can not take off. If it brakes on landing you can't go around. I haven't tried it in the air but it would be very rough, probably bad on the engine, not able to make much speed. I really don't want to try it in the air.

Rich
120002
 
Haven't had a chance to see what the throttle setup is on the Rotex yet but all I've encountered on certificated aircraft have no problem moving the throttle around. The spring is only there to go WOT incase the cable breaks. Wouldn't notice the spring on my Cessna if it broke. The 12 I flew had WAY to much spring in it for me.
 
I have heard several accounts where the engine could not attain full power due to a broken spring. I had TWO broken springs in my RV-12 and did not notice any degradation in power. The throttle cables were stiff enough to operate the linkages.

The Piper and Cessna aircraft I've owned did not have springs, so I wonder if this is an example of an idea that looks good on paper, but does not live up to the promise in the field at least for the configuration of the RV-12 throttle.

The throttle arms on my carburetors move easily so I am satisfied the throttle cables are stiff enough to operate them without springs. Experience has born that out in my plane, but I agree the tension keeps the carbs synced at low power.

I continue to use "weak" springs to eliminate throttle creep and maintain synch.
 
It is my understanding that the primary purpose of the carb springs on the RV-12 / ROTAX 912 ULS installation is to provide a consistent operating tension on the somewhat flexible throttle cables. That the springs also cause the carbs to go to full-throttle in the event that the cable breaks or becomes detached from the throttle arm is a secondary benefit.
 
Right. The 912ULS does NOT NOT NOT need the springs to go to full throttle!!! !!! Throttle adjustment for full travel is part of the installation instructions.
 
Still looking and wanting the recommended emergency procedure from Van's. Hoping Scott will pass this issue to the team. Scott?
 
Still looking and wanting the recommended emergency procedure from Van's. Hoping Scott will pass this issue to the team. Scott?

Marty,
It is being looked at.

I don't mean to be condescending with the following (and I know I come across that way at times when looking at issues from an engineering perspective)...

I am not sure what an entry in the POH is going to do for a competent / qualified pilot beyond what their own pilot problem solving skills should be capable of.

It is fully excepted that if a cable fails, a pilot will have to fully open the throttle to obtain smooth engine operation.
What you do from there will depend on the specific circumstances at the time. No POH entry can cover all of the possible scenarios.

Since I consider my self somewhat competent and qualified in the RV-12, I have already thought through the issue and have come up with a number of different ideas to use depending on the situation, but I have not personally experienced this issue (which I would consider extremely rare based on what I have heard).
I will hold off sharing my ideas until a decision is made whether to officially incorporate a recommendation into the POH.
 
The POH doesn't need to explain how to get the plane back on the ground in various possible scenarios, but it would be good to have something in there about cable failure so that it's clear what the best procedure is to avoid damaging an expensive engine. Most people would probably instinctively go to full throttle, assuming they realised that a cable had failed, but BillH also mentioned maybe using the choke. Does that have any merit? I don't know.
 
Sounds like most guys cruise at about 5300. RPM. Since that's high cruise I wonder if one carb at full throttle would push the RPM much past redline. I guess we'll have to wait for the first unlucky guy who breaks a cable to report back.
 
Back
Top