The International Cessna^® 170 Association

I think the point mekstrand was making is that the control system is designed to withstand air loads up to maneuvering speed and hopefully that is higher than any air load imposed by wind while the aircraft is on the ground. I can't disagree.

I have to say that I was not immediately thrilled attaching anything around the light fixture. Instead despite warnings I used a clamp style lock at the top of the rudder and the stabilizer. Of course when I started to see the damage I was told would happen from that style lock, that being wrinkled rudder skin, I decided maybe I shouldn't try to reinvent the wheel and use what others had been doing successfully. That being some kind of attachment from the rudder light to each side of the aircraft.

I have no experience with the York lock so I won't comment on it or whether I'd trust it and the control system would stop the rudder from smacking the control stops which is the objective because most wind damage is found at that location when no gust lock is employed. It is fairly apparent that mekstrand has not used the system we are suggesting either as making what seems to be a negative statement that we are just wrapping twine around a light fixture is not really accurate or fair. But come to think of it, twine would probably work as well.

As simple and cheap as the system and variants George and I have described are, and despite how ineffective it might seem to just loop around the light fixture to secure the rudder, the system really does work very well. It is certainly not the only system that can work, and it is not infallible, but I will put it up against any other otherwise I wouldn't suggest it.

George,

No offense taken. We just have different opinions about how we choose to protect our aircraft from wind damage. The fact that we all choose to do something is what is really important. My primary gust lock is my hangar.

That being Said, my York gust lock may be different than what others have described. The lock I have secures the rudder pedals in the neutral position by latching on the the heel portion of each rudder pedal. With the pedals immobilized, the rudder can not move. I personally prefer this method as it utilizes the proper load path that was designed in to the structure to secure the rudder. The loads imposed on the rudder through this system are no different than those created by my feet during flight as this is a reversible control system.

Dispite the success that everyone seems to have with the rope method I'm not convinced that securing a large flight control by it's trailing edge is the best possible solution. The trailing edge was not designed or engineered to withstand any force other than air loads. Securing the largest flight control by the weakest portion of it's structure seems like a great way to damage your rudder to me. (just my personal opinion)

My comment about maneuvering speed was ment to clarify that the cables, pulleys, and control horns were designed to be capable of handling the air loads generated by a very large rudder at a very high speed. I do not believe that gust loads on a stationary aircraft would exceed the strength of the rudder control system without damaging the rest of the aircraft. (I fly a French jet for a major airline and I am very familiar with AA 587 and the increased awareness of exactly how maneuvering speed is derived and relevant)

As I said before, our methods and reasoning may differ. The important thing is that we protect our aircraft from wind damage.

I also mean no offense... only discussion...which should hopefully be mutually beneficial if not simply of some interest.

I really see a big difference in using the control cable system to hold a flight control in position as opposed to using a more directly applied resistance to wind.

The leverage of the leg is powerful, I agree. And the cables used are rated in the 7,000 lb ultimate-load range. And that is the problem. The pulley's and brackets are not.

Using a cockpit control lock: Any force applied to the rudder will move that rudder due to the geometry of the lever and the size of that rudder. (The rudder can impart far more energy into the cable system than any force placed upon the pedals simply due to the differences in mechanical advantage. Rudder pedal leverage is about 8" and bellcrank is about 6", but rudder trailing edge to hinge line is more than 20" and has far more surface area to multiply the force.) Therefore, using a locking method at the rudder is much less abusive to the entire control system than any method applied in the cockpit.

Using the trailing-edge of the rudder: Gives the greatest mechanical advantage (again due to leverage.) Any forces applied by winds affect the rudder only (as long as the method survives) and unlike the cockpit methods, places no strain whatsoever on the control system. The trailing edge, particularly at that reinforced light-fixture, is very capable of withstanding high forces. I do not know of ANY damage to any rudder using this method, and my particular arrangement isn't the only one I have in mind when making that statement. The leather "bra" (which I first encountered from Cleo Bickford) preceded my own little modified-version, but they both utilize the same principle. I have seen two aircraft damaged using cockpit locking methods (admittedly in severe winds which damaged more than just rudders.)

Due to the mechanical differences in applied forces, I strongly disagree that "manuevering speed" has any relevance to locking controls with cockpit methods. I doubt any of us will lose sleep over it. It's just a difference of opinion.

( I will admit that using seat belts to secure elevators is contrary to the logic I just explained, ..in fact, the elevators are probably the weak-link in the methods I use.... my imagination has been long at-work trying to come up with a suitable system to address that issue. I've imagined a sort-of "cross" which might be applied to rudder/elevators simultaneously at their trailing edges to lock them in unison. I've just had too many other holes-in-the-dyke and only two thumbs to deal with them, so far.... )

I don't buy the argument about maneuvering speed, because it doesn't account for the force of a wind gust coming from behind the airplane. A gust hitting the rudder straight on from the rear could slam it pretty hard against what ever is holding it. The rudder has a pretty high mechanical advantage against the horn, cables, pulleys, etc. Much less so against a cord holding the anti-collision light. I'm with George on this one.

jrenwick wrote:I don't buy the argument about maneuvering speed, because it doesn't account for the force of a wind gust coming from behind the airplane. A gust hitting the rudder straight on from the rear could slam it pretty hard against what ever is holding it. The rudder has a pretty high mechanical advantage against the horn, cables, pulleys, etc. Much less so against a cord holding the anti-collision light. I'm with George on this one.

My guess would be that a direct crosswind would be worst case on the rudder, and wind from behind (neglecting the improbability of straight down) would be worst case for the elevator; neither likely to survive a gust at Va . My hangar too is my primary gust lock, but I find my 170 gross-weight-challenged for its use when away from home. I need to find my Bickford leather eyelet for the tail light and make up a gust lock. Knowing Cleo, I'm sure he looked at it from every angle (literally and figuratively ) and thought that was the best option.

cessna170bdriver wrote:I need to find my Bickford leather eyelet for the tail light and make up a gust lock. Knowing Cleo, I'm sure he looked at it from every angle (literally and figuratively ) and thought that was the best option.

As reported Cleo designed the leather bra but that was not his design in his '72 drawing. In it he describes using particle board for a center device around the rudder.

Being it was '72 and particle board had probably just come on the market as a new modern material, Cleo might not have realized particle board would disintegrate in the weather. Finding that choice of material was the weak link in his design is probably what prompted the leather bra design. We will never know.

gahorn wrote:I took the vinyl-coated hooks off a bungee cord, and threaded some braided polypropylene rope thru them...Another short piece of the rope is inserted in the mid-point forming a small "bra", so that... a hook is placed into each end of the horiz stabilizer.

I have attempted to make one of these for my 170A and have succeeded for the most part. Problem is, on my A model and my hangar-mate's '48 170, both of our horizontal stabilizers lack the gap in the end rib through which this photo depicts the hook going through. Has anyone else made some sort of adaptation to still use this setup? I was thinking of trying to fabricate a bracket that would wrap around the leading edge and outboard side of the rib with a tab extending out to capture the hook. But if someone else has already developed something they'd be willing to share...?

I made a sling and tie it off with at the elevator hinges. I used 1/2" twisted nylon rope that I braided a loop in the middle to go over the tail light. I keep 81D outside all year long and it's worked quite nicely, not even chafing the paint so far. Will try to take a pic later today.

RE: rear vs cross wind damage, a gust directly from behind the airplane will be the worst.
From the side, the rudder deflects away from the wind the closer it gets to the stop. The more it deflects, the less cross section is presented to the wind. So when the rudder finally hits the stop, it has less force being applied to it.

From the rear, the rudder deflect INTO the wind the closer it gets to the stop. This presents MORE cross section to the wind. When the rudder hits the stop, is has the maximum force applied to it.

A 10MPH wind from the side may not have enough force to overcome the rudder springs but that same 10MPH wind directly from behind will slam the rudder over to one side or another and hold it there.

That picture is of George's technique. Works if the elevator is held up. I store mine with the elevator down. My plane has been tied down outside using a hook over the elevator to the slot of each hinge in it for 45 years with no damage other than a rust stain. The rope or the 1/4" rod we use at home passing over the elevator also serves to hold the elevator down.

I ended up fabricating some brackets that attach to the horizontal, through which the rope is routed to (instead of the bungee cord hooks). Nothing too fancy, just some bent and cut up scrap sheet metal painted bright red to help with visibility. Also glued some extra art foam I had laying around to pad/protect the horizontal.

I guess since they FASTen to the horizontal that's why they're RED.

Nice work.

My solution. A little pvc pipe, foam insulation for protection and a bungee cord.

juredd1 wrote:My solution. A little pvc pipe, foam insulation for protection and a bungee cord.

We use these in gliders a lot but I would advice against it on the 170. I wish I could find the pictures of the damage. Doug

Damage....please elaborate.

juredd1 wrote:My solution. A little pvc pipe, foam insulation for protection and a bungee cord.

Where do you store those long things? My hangar mate told me about that sort of setup, but they look so much more bulky than the ropes when not being used. I just wad mine up and toss 'em under the bench seat. Installation is a cinch, no messing around with bungees and long tubes on opposite sides of each a stabilizer.