The International Cessna^® 170 Association

Need info and suggestions on a new throttle cable.... I drive a 1954 "B" and would like to consider a vernier cable....... Can I change without an STC or will it be one of those, more trouble than it's worth situations???
Nothing really wrong with the original door knob, existing one, just want to update it... Comments/Suggestions welcomed....

Thanks,
fansys
2521C

I wouldn't call a change from the original control to a vernier an "update". I'd call it an alteration. And not a good one. But that's just my opinion.

Engine control changes using aircraft quality cable-controls are minor alterations and do not require an STC, and with your permission, I would offer further comment on your contemplated change to a vernier control.

Vernier controls work very well on fuel injected and/or turbocharged engines where small, incremental power changes are frequently made and accuracy is more important due to installations that work in conjunction with constant speed props. But they are not friendly to normally aspirated engines like ours. Here's why:
1. Power applications are locked into the vernier mode unless the entire knob is captured by the operator's hand and the central knob is held in a compressed state for the entire movement of the throttle. Any inadvertent relaxation of the operator's grip will reengage the vernier function and full power will/may be prevented unless further manipulation is made. In an emergency, such as a go-around, this can be very unfriendly and distracting. (And, even if the knob is captured and full power is requested, full control movement is not accomplished until the operator makes further efforts to "screw-in" the final movement of the vernier..... in other words, full power cannot be assured easily without manipulation.)
2. Power reductions suffer the same problem in that large power changes require special manipulation of the locking knob, and vernier operations do not provide sufficient operational control to quickly set-it-and-forget-it.
3. Vernier controls require greater operator attention to achieve the desired power setting, with resultant distraction from other duties, such as traffic watch, etc. (You'll be watching gauges and fiddling with the knob instead of setting the power and getting on with flying.)
4. Our engines do not require micrometer-like vernier controls and cannot take full advantage of the vernier feature due to the relative crudeness of our induction systems and carb.


I recall many, many flight instruction periods in which I observed students/clients twisting twisting twisting twisting then re-twisting re-twisting re-twisting re-twisting knobs until I just wanted to deliberately fail the engine so they'd stop it!
"Just set the power and leave it alone!", were my frequent thoughts. This sort of behavior never occurs in ordinary friction-throttle cockpits. (Ever notice how "real" high-performance airplanes, like recip-fighters and muti-engine models NEVER have vernier controls?)

Vernier controls were introduced in higher power applications which ordinarily provided larger magnification-order vibration which could cause friction-controls to move from selected positions. They were first offered in Beech airplanes, and the snob-factor quickly led to their adoption into high performance Cessnas. Verniers are for people who wear ascots and use cigarette holders.

But I don't really have any opinion either way....

By the way.... how are you going to attach your threaded-ended vernier control to your throttle-plate lever on your carburetor? (Hint: You are unnecessarily complicating your life.)

Had one of those in my current plane when I bought it. Found out that trying to push on the knob at the same time as pulling it out in a hurry is not good. Got the plane home and took the viernier out and tossed it first thing. Might have something to do with the plane being a minor project when I got it.

Had one on my first 48 170 I didn't like it either. I'm going to need a new one some day where is the best place to get one. The normal one that is.

http://aircraftspruce.com/menus/ap/controls.html

http://store.wagaero.com/index.php?cPath=37_107

http://univairparts.com/shopping_291765 ... Path=25_73

You can also buy the knob only to install on whatever cable assy you choose:
http://store.wagaero.com/product_info.p ... ts_id=2335

gahorn wrote:http://aircraftspruce.com/menus/ap/controls.html

http://store.wagaero.com/index.php?cPath=37_107

http://univairparts.com/shopping_291765 ... Path=25_73

You can also buy the knob only to install on whatever cable assy you choose:
http://store.wagaero.com/product_info.p ... ts_id=2335

I meant the best price. If anyone had bought one lately. I will look at the catalogs too, I know I'm lazy!

and McFarland

Best prices are the ACS brand, you lazy cheapskate!

I have and use a venier cable on the mixture, it allows better fine tuning of the mixture at cruise.

Dean

Me too Dean, I like it on the mixture control. Has big RED button in center on knob and it seems easier to dis-engage than the clip lock. I like my ascots and cigarette holder too.

Try the ACS 740 series with RATCHET action. They come in red. It does not require a locking clip, holds well to any position, and is incrementally adjustable. http://www.aircraftspruce.com/catalog/a ... ntrols.php
(I still don't like verniers, even on mixtures, although I admit they are not offensive in that position. It's like using a micrometer to adjust a grease pencil, with the lack of precision of our carb/induction systems. Just my opinion.)

Nothing really wrong with the original door knob, existing one, just want to update it... Comments/Suggestions welcomed....

I like my "original door knob" throttle. Has cool factor

I do have a venier on the mixture, but you asked about the throttle.

If its not broke, don't fix it.

Bill

I'll echo the suggestion not to try to repair a damaged or worn out throttle cable. Mine had gotten to where sometimes it was a bit difficult to operate & several airport folks suggested pulling the cable out and lubercating it. While pulling it out I saw a couple of places where the protective covering (rubber like coating) was damaged. I could not stand outside the cabin & reach in and push the throttle in I replaced it with a new one, and as often the case, wondered why I had put up with the old one for as long as I had. The new one works so well.

Ascot and cigarette holder indeed!
I laughed so hard my monocle popped off!

Just to give a different point of view, I have a vernier throttle on my C-170. My C-180 came from the factory with a vernier, some Bonanzas and Maules do too. I like them. It was on the 170 when I bought it in 1973 and I didn't know any better, having a grand total of about 200 hours at the time. I found it very easy to get used to and never had any panic moments where the throttle "stuck" because I didn't push the button before trying to change the throttle. I make it a habit to make throttle adjustments with two fingers behind the knob and thumb on the push button. And if for some reason you get excited and need full throttle RIGHT NOW, It will always increase if you push on it and with no throttle lock to impede the action there is no delay. Or if you choose to make fine adjustments, just turn it with two fingers.

I find it especially handy now that the plane has a digital tach and I want to make small adjustments in cruise or on approach. Sometimes a quarter of a twist is all that is needed. It is much more precise than pushing or pulling which is often accompanied by over/undershooting the desired rpm several times. And there is no lock that has to be un-locked then re-locked to change throttle position.

I use it frequently during cruise to tweak the rpm. With the digital tach you're not, as George puts it, trying to measure precisely with a grease pencil anymore. I know, it doesn't matter that much if the rpm is off a little but there is usually not much else to keep me amused in cruise and the digital tach is exact. So why not use it?

On approach it is especially handy, allowing very small precise changes to rpm in order to maintain glideslope. You don't have to distract your scan to any other guages to make the desired changes and much more desirable than trying to unlock, re-set, then re-lock a standard throttle. Its one more thing to reduce workload in actual IFR situations.

I use the ACS 740 series rachet-stop mixture control that George refers to above and it works very well.

hilltop170 wrote:.... And if for some reason you get excited and need full throttle RIGHT NOW, It will always increase if you push on it and with no throttle lock to impede the action there is no delay. Or if you choose to make fine adjustments, just turn it with two fingers.....

But if you have to suddenly RIGHT NOW reduce throttle (because a brake hanged up or a tire went flat etc. on takeoff) to avoid a ground loop.... you'd better remember to mash that center button or it's gonna take a little time to reduce to idle.

Here's a fatality partially blamed on vernier:
http://aviation-safety.net/wikibase/wiki.php?id=10052

Here's another accident:
http://www.ntsb.gov/ntsb/brief.asp?ev_id=68520&key=0
REMARKS- VERNIER TYPE THROTTLE DID NOT REDUCE THROTTLE FULLY LNDD WITH PWR ON.CUT SWITCH.ROLLED INTO BUSHES

From the formation-flying instructor at the RV-6 club :
"The 'STANDARD' is NO vernier throttle in formation training aircraft. NO EXCEPTION.
Vernier throttle is too difficult to make changes FAST. PUSH Button then pull or push throttle in. It the amount of time that it takes the pilot to do that, he just flew into another airplane or is so far out of position that it takes a lot of work to get back in. We are flying 140 to 150 mph close to another airplane. At 150 mph, you are moving 220 feet per second. That extra second needed to change the vernier throttle takes away from your concentration is DANGEROUS!
NO VERNIER throttles for newbie in any of my formation flights. NO Vernier throttle in formation training aircraft. NO exception."

Ok. I'll quit for now.