Spring's Shming's

mrpibb · Post by **mrpibb** » Mon Jun 28, 2004 4:52 pm

Okay, just like everybody else I had to find out for myself the advantages/ disadvantages of compression verses tension steering springs. As I was getting my tail wheel endorsement I was concerned about the ground steering of my airplane, I asked my instructor who is a very experienced tail wheel person what is one to do? He said I could try compression springs which would give me more positive steering " BUT" he cautioned me the due to the 170 steering geometry and tail weight I may start bending steering arms. Me feeling neigh invulnerable went and bought a set of compression springs, installed them and noticed that yes, more responsive steering BUT wasn't keen on the amount of tourqing evident on the rudder horn. I just figured I'll be careful not to apply full rudder when not rolling, well while good in theory wasn't the case in actuality, I started to notice my steering arms bending at the end of every flying day, HUM?? Okay I know what I will do, I'll just go and order the heavy duty arm that Scott has and everything will be fine, right??
Well the new arm shows up, hey it looks BEEFY great!! so out to the airport I go,during the installation the instructor who gave me my checkout came over to visit, he sez oh your putting on the heavy duty arm, hum, yea it will help on the geometry thing with the bent up tabs but what will happen is that instead of bending it may start twisting on you.
I said " naw look how BEEFY it is" so now everything's together but to late to do any flying so I'll wait till the weekend t check it out. Sunday rolls around and it seems nice to do some flying, get to the airport to find that the rest of the world is nice but that darn west wind at Aeroflex. Well typically at Aeroflex the winds die down about late afternoon so I figure ( Don't worry I am going somewhere with this

) I'll cut the grass around my tie down. I get the community push mower roll it over to my spot, figure I'll untie the plane and just push it off to the side to make it a little easier to cut. I cut my little square of rented airport real estate, roll the mower back to the hanger (the mower gets a hanger but I cant!!) and go push the airplane back, HEY what's up with my tail wheel something's not right? wouldn't you know it just from pushing the airplane back and to the side 20 feet was enough to TWIST my HEAVY DUTY steering arms like pretzels!! Well after about ten mins of saying non Christian things the tail went up on a step ladder and got reacquainted with it's tension springs and the compression springs I placed on the fbo counter next to the doughnuts, the doughnuts are gone but the springs are still there, go figure

This is my story, and I'm sticking with it!!

Post by **Bruce Fenstermacher** » Mon Jun 28, 2004 5:28 pm

Hey Vic
I passed through Aeroflex about 11:00 Sunday morning also stopped at Trianca and Hackettstown on the way back to Quakertown from Sussex where we had breakfast. Winds weren't that bad. Almost down the runway. Had a friend of mine make his first 170 landing from the right seat at Aeroflex. He does have Cub and Belanca time so he's not a total newbe to the tail wheel.

mrpibb · Post by **mrpibb** » Tue Jun 29, 2004 3:14 am

Bruce, sorry I missed you, I didnt get to the airport untill 2 pm, I guess you didn't see the Ragwing parked on the back row (with all the birds on it). The morning I was told was nice there, like you said down the runway, I always seem to bring the wind with me. Howdoya like those three hops at Trinca? the third usually gives me a good enough hop to stay in the air. Trinca is kinda the official tailwheel check out field for Andover Flight, you probibaly saw the super cub, L4 or the Husky zipping between the two airports. I usally go to trinca to warm up on landings, then on to points north. I also made it to Hackettstown, but not untill 8pm, remember I was fussing with the tailwheel all afternoon. Maybee I'll make it out to check out Quakerstown next week, this week was Kutzstown, VanSant and Alexandria.

zero.one.victor · Post by **zero.one.victor** » Tue Jun 29, 2004 3:45 am

Regardless of whether you're using tension or compression springs, I would check steering chain tension both with the tailwheel on the ground & up off it. At least with mine, the chains are a lot tighter with the wheel off the ground,due to the tailspring relaxing. I set my chain tesion to be a little loose in the three point postion,otherwise it's too tight with the t/w off the ground. By the way, I use compression springs & have had no problems with them.

Eric

Post by **GAHorn** » Wed Jun 30, 2004 11:49 pm

(not a criticism to Eric, just an out-loud comment) ... Do whatever you wish with your own, but there's a reason Cessna used tension springs. (By the way, where's the approval for the compression springs?)
FYI for all, ...The rigging instructions specify light tension while the aircraft is on the ground with the weight at 2,000 lbs.

mrpibb · Post by **mrpibb** » Fri Jul 02, 2004 6:55 pm

Well, shot about 15 landings at Trinca and 10 at Aeroflex and got reaquainted with my tension springs, steerings like jello but everythings mello

.
Everybody have a Happy 4th, especially you convention folks!! I'll be flying up to N.H. for the weekend to help a friend get his 56 172 back together.

rudymantel · Post by **rudymantel** » Sat Jul 03, 2004 10:02 pm

Vic, I had the same problem- not enough tailwheel steering authority when taxiing in a crosswind. The problem is not enough brakes ! The tailwheel alone will not allow you to taxi in a significant crosswind. It isn't meant to ! I have tension springs, with medium tension. I solved the problem by installing double-puck Cleveland brakes, was fortunate enough to get FAA field approval. I'll be glad to send you my paper work if you want it-
Rudy

N170CT · Post by **N170CT** » Tue Jul 06, 2004 5:45 pm

Eric,

Which model 170 do you drive and which model Scott tailwheel is mounted on your aircraft. This is not the first time I have heard your description......, but on my 170B with the up-turned steering arm, the chains are tighter in the three point position than in-flight.
Relaxation of the load on the tail wheel spring allows the wheel itself to drop lower and slightly forward relieving some of the tension. Is yours different

Just curious

zero.one.victor · Post by **zero.one.victor** » Wed Jul 07, 2004 4:51 am

I have a ragwing with the 3200 on it. I installed the turned-up steering arm (p/n 3214T) also. The chains on mine are definitely tighter with the tailwheel up off the ground. Maybe our tailsprings are arched differently?
I guess it doesn't matter which position has the chains tighter--the point is just to check the tension both ways,and be aware that it may be different,and must be allowed for when adjusting chain length.

Eric

mvivion · Post by **mvivion** » Wed Aug 04, 2004 3:38 am

Well, guess I'm lucky. I didn't like the (non) steering of the 170 when I first bought it many years ago. I changed to compression springs, which I've had good luck with on other airplanes. Still marginal steering. My tailwheel springs were basically shot, so we replaced the main spring leaf with an L-19 main leaf, which is MUCH stronger, and keeps the tailwheel geometry in line much better, and replaced the steering arm on the tailwheel with a 3214 T steering arm. We then moved the steering chains out to the ends of the steering arm for the floats, and I have almost too much steering authority now. That said, I have never, in many years, bent anything, certainly not by just moving the airplane by hand (!!). There's something bad wrong with the installation if you can bend the 3214 T arms just by pushing the airplane around on the ground.

All the stuff noted above was done via 337 several years ago. Probably couldn't do it again for love nor money.

That said, the compression springs are approved springs, the 3214 T steering arm is an approved part for the Scott tailwheel, and you may be able to get a courageous mechanic to sign it off as a minor alteration. Maybe.

It did improve my steering considerably, and I've not had any problems in several hundred hours of flight, including off airport operations.

Mike

Post by **GAHorn** » Fri Aug 06, 2004 2:13 pm

mvivion wrote: That said, the compression springs are approved springs, the 3214 T steering arm is an approved part for the Scott tailwheel, and you may be able to get a courageous mechanic to sign it off as a minor alteration. Maybe.

Mike

In conversation with Mike, it became evident that his opinion that compression springs are "approved" was based upon those springs installations in aircraft other than 170s.
One might wish to keep in mind that parts approved for other aircraft types do not automatically confer approval upon all types.
There is no approval basis for compression springs on 170s that I've been able to find. Anyone having knowlege of approval, please contact me with the info. Thanks.

mvivion · Post by **mvivion** » Sat Aug 07, 2004 2:22 pm

Actually, what I thought I said was that, since the springs are pma'd, they are an "approved" part. That was the answer to your specific question.

I also noted that we installed them on my airplane with a logbook entry (with the knowledge and approval of a FSDO type) as "equal to or better than".

They do not require to be specifically approved for a make and model of airplane, for example: Does your King KX 170B have a specific approval for the C-170? I'm sure some do, for the installation, but the point is, it's an approved part. Now, to install it, you either need an STC, a field approval, or a logbook entry, if it's determined to be a "minor alteration".

One of the problems with the field approval system right now is that the FAA trained mechanics that they should request a field approval on EVERYTHING, when in fact, the regs DO NOT require such. Mechanics got used to having the FAA take responsibility for all mods, and now are reluctant to do logbook entrys on minor alterations.

We have at least one cooperative FSDO person, who's trying to shift this back to where it's supposed to be. I spoke to him the other day about lightweight batteries in the airplane. His comment was that as long as it's an "approved" battery (ie: pma'd) and its located in the same place, do a logbook entry as a minor alteration. He passed that along to the mechanics for me, and there we are.

If you take the "old" strictest FAA approach, NOTHING is approved for a 170 except that which was listed on the TC, including your new interior, radios, etc. That clearly is not the intent of the FAA now, at least based on national guidance.

So, my springs are "approved", and legal, I might add.

How about yours?

Mike Vivion

Post by **GAHorn** » Mon Aug 09, 2004 3:31 pm

Mike, we did not discuss PMA at all. My question to you in private was to ask what you meant by "approved".
Your response to me in part was:

"It gets back to the "minor alteration" issue, versus a field approval. Compression springs are an approved part. They don't appear on the C-170 TC, but neither does an R-985 Pratt and Whitney engine. Doesn't mean the 985 isn't approved, right?
So, if its an airplane part, and "approved", then can I put it on an
airplane whose TC data sheet doesn't spell it out for?we did apparently we agree that the installation requires some basis of approval. I.e. either STC, Field approval, or approval as a minor alteration...if that's appropriate. ..."

I would hope the above scenario is self-evident to most.
PMA is not approval for installation upon a particular type aircraft. It is merely approval for a manufacturer to produce a replacement part that is for installation upon an aircraft (or appliance, engine, etc.) for which it is ALREADY approved by type certificate. (Read the PMA statement of the manufacturer to determine which aircraft the part is actually PMA'd for.) The compression springs are not (to my knowlege) ALREADY approved for installation on a 170. One may not install them without a subesquent basis of approval and remain in compliance with the rule.
In your case, your mechanic has "covered you" by signing it off as a "minor" alteration. Whether his assessment will stand up to scrutiny by a FAA inspector is an entirely different issue, but at least it should offer a defense to you as the owner/operator should it overstress the cables or rudder bellcrank and cause an incident or accident.

ANY radio installation requires appropriate approval evidenced by sign off by a licensed installer/repairman. It doesn't have to be "FAA approved", or FCC accepted even. It just has to follow the rule requiring that it not adversely affect the aircraft. (You can install an automotive CD player if you want to, and it does NOT have to be TSO'd. It just must meet the requirements of FAR 43 and not interfere with other approved equipment...which is where a TSO can help by reducing the proving requirements.)
Bizarre question: Jet fuel is also "FAA approved". Can we pour it in our 170s?

I'm not trying to get us all wrapped around the axle over whether or not compression springs have merit or not on a 170. I've expressed my opinon on that (as has Cessna and the compression spring manufacturer themselves through their PMA certificate) and it can be either taken or left. The discussion I'm attempting to address is the merits of legality...for those interested in such things. As the old '40s tune sang..."Wishing Don't Make It So". And the regs put it right back in the lap of the owner/operator, regardless of who signed what in the maintenance records.

mvivion · Post by **mvivion** » Wed Aug 25, 2004 6:07 am

Well, you make some interesting points. The fact remains, however, that a part can have a manufacturer's approval, and be installed on an airplane without specific approval for that airplane make and model.

Where on your bin full of bolts, nuts, washers, and other hardware is the specific approval for the 1953 Cessna 170 B? Those are approved aircraft parts, and require no further approval for use, since they have been documented to meet certain basic standards in manufacturing, and meet the basic standards called out by Cessna for a particular application.

A tailwheel steering spring is a steering spring. We can argue this all you like, but not every part you bolt on your airplane has to be approved specifically for that make and model airplane. These things come standard on some factory aircraft, the Husky being one, the Maules another. They are "approved" parts, by FAA definition. You can call them whatever you like.

The whole field approval/minor alteration thing has way too many people paranoid (and not without good reason, I'd agree) about performing minor alterations.

I agree that steering is a serious issue, and one needs to be careful. That's why I consulted with a professional maintenance person, and took his advice AFTER consulting with an FAA maintenance inspector.

Are they approved on my airplane? I think so, my local FAA thinks so, my mechanic thinks so. Just exactly who else should I consult?

Anyway, I never suggest to folks that they should just bolt stuff on. I would note that replacing steering springs on a Cessna 170 is not within the purview of a pilot or owner, unless they hold the appropriate repairman's certificate. So, if someone wants to install approved parts on their airplane, I recommend that they take their question to their mechanic, and/or the FAA for the answer, but to say that every part must be approved on a specific make and model of airplane without exception is a much too narrow interpretation of the rule.

There is such a thing as a minor alteration. You can't install a spring off your screen door in place of an approved part, but if it's an airplane part, your mechanic MAY be willing to call it a minor alteration.

Or not,

Mike

Post by **GAHorn** » Fri Aug 27, 2004 12:10 am

Mike, you really are still just "wishing it were so". You are incorrect that springs can be simply installed because some other airplane has them. It just ain't so.
Your example of aircraft hardware being applicable to all aircraft is an example of simplicity...but you misunderstand it. The rules says "standard" aircraft hardware...such as AN or MS or NAS hardware may be installed without further basis of approval...PROVIDED that the aircraft manufacturer approved such hardware or PROVIDED it is replacing similar hardare.
For example, It DOES NOT authorize using an AN SHEAR nut in lieu of an AN STANDARD nut! Why? Because even tho' they are BOTH aircraft hardware, and they are BOTH approved for aircraft use, they ARE NOT the same part! They are both nuts, but they have different design characteristics for different purposes.
A COMPRESSION spring has different design characteristics for different purposes (or different installations.) You can't simply install it because it makes sense to YOU. It must meet SOME basis of approval. (The compression spring in this discussion does NOT have an AN, MS, or NAS part number. It may NOT simply be substituted for an approved part without further basis of approval unless it is replacing an identical compression spring in the SAME application on the SAME type design aircraft.)
If your mechanic thought installing them was a minor alteration and he was willing to put his name to that statement in your aircraft logs....then more power to him and yea! for you because that is likely a valid basis of approval! (Providing, of course, that he is right about it being minor! If the FAA or any other authority should take issue with that opinion of his then HE will have to defend his actions.)
If you don't understand the logic behind these differences, then I suggest you contact your mechanic, and together you guys go over to the FSDO and have nice lunch with your inspector. I'm sure you'll all be much better informed come the end of the day. But don't go around telling too many people how you stick airplane parts on your airplane on the assumption that because they're approved for some OTHER airframe that you think that makes them applicable to YOURS. Wishing don't make it so.