I recently sent out a message on the Cozy Mailing List to get a better idea of changes made to the rod ends and inserts for my Cozy MKIV. I got several private replies by individuals that were also somewhat confused by the issue as well. As usual, when I have any confusion about the plans, I turn to Rick Maddy's excellent search tool to look at past discussions on the Cozy Mailing List. In particular, I look for Nat Puffer's name since he's the designer and authoritative source on all matters related to the Cozy. I was able to find a posting from Nat from over 5 years ago which showed that this topic had created some confusion among builders. In his explanation given below, you can read Nat's take on the historical events leading up to the changes related to the CS rod ends and inserts:
Date: Mar 3, 1999 12:00 A.M.
From: "Nat Puffer" <cozy@extremezone.com>
Subject: COZY: CS Inserts
People, There is confusion on the CS inserts which I will try to explain. First of all, our practice has been that if there is a Long EZ part in stock that works, we don't design a new part, or give the same part a different name. Okay? Well, originally there was only one rod insert, and that was CS(for control system)-l. It was aluminum, supposed to fit inside an .035 wall tube, and was tapped 10-32. Then some Long EZ builders were bending the AN-3 rod ends to the elevators, when installing and removing the canard, so the CS-1A was born, which was drilled and tapped for 1/4 x 28 for 1/4" rod ends, and specified to be used on only the elevator push rods. Then a Long EZ had an engine fire and Burt decided the aileron push rods ought to be thin wall steel, so the CS-50 was born, but it was made of steel with an OD to fit inside a .028 wall steel tube. The CS-1A was switched to steel at the same time, although not necessary, and it was not given a new name because the dimensions stayed the same. The change from CS-1 to CS-50 was reported as a design change in the newsletter to all first edition plans builders. The nomenclature was changed to CS-50 in the second edition plans. To summarize, CS-1A is used on the elevator pushrods (for strength) and CS-50 is used in the engine compartment for fire resistance. There will be another change coming up, and that is the OD of the CS-50 will be reduced, because .028 wall steel tubing is very difficult to obtain, and most builders will have to use .035 wall tubing. In reviewing this in the second edition plans, I see that I didn't increase the OD when the designation changed to CS-50, but I don't have to make a design change, because the OD is being reduced for all new production. Clear as mud, huh? Best regards, Nat
Long EZ Plans
I think that where Nat mentions that some LongEZ builders started bending the AN-3 rod ends, he may have be referring to Vari-eze builders. I have a set of LongEZ plans (March 1980 First Edition) and have copied a page from it below and it shows both the CS-1 and CS-1A inserts. The CS-1A inserts are similar except that they are a little longer and drilled and tapped for a 1/4" x 28 thread instead of a 10-32 thread like the CS-1 insert. The CS-1A inserts are used in the elevator pushrod only (2 total) on the LongEZ. The CS-1s are used everywhere else (10 total). Note that neither insert has a flange.
Canard Pusher information
In addition to looking at the plans for the LongEZ, I also searched through the text archive of Canard Pushers and found references to the changes to rod ends and inserts in four of the CP's. I should also mention that the electronic text version of the CPs only goes up to CP82 which was published in October 1995 so if there were any other changes made to CS-50 after 1995, I haven't been able to search for it. These text-based versions of the Canard Pushers were provided by Stet Elliot and have subsequently been released for downloading from the Internet. You can find the Canard Pushers in several formats in the Other Reference Material section of Marc Zeitlin's Cozy Website.
From CP20 Dated April 1979
CONTROL SYSTEM ROD-ENDS The
VariEze control system is unusual in that it uses the small HM-3 rod-ends in its
primary controls. Aircraft normally use the 1/4" hole HM-4 as the minimum size.
Justification for this is that the control surfaces are small, sized for the low
forces required for a sidestick control. Thus, the design safety factors are
still larger than in normal control systems. However, the small HM-3 rod-ends
are relatively fragile if they are subjected to bending or twisting loads. These
loads do not exist in operation, but they can occur when the canard is being
removed, or at the stick if the roll stops are not adjusted correctly. We
recently heard from a builder who broke an HM-3 while he was installing his
controls! This is a very serious concern, since there is no redundancy in the
pitch system to save the airplane if one should fail in-flight. This is not as
serious in the roll system, since the airplane can be steered with rudder or the
other aileron. Due to the relative frailty of these rod-ends, we are
recommending that you immediately replace the four primary pitch rod-ends with
HM-4's as shown in the adjacent drawings. This includes both ends of the CS136
tube and both ends of the CS102 tube. Note that two CS201 spacers are required
for each rod-end on the CS102 pushrod to allow sufficient roll travel. They are
steel, 5/16 OD x 1/4 ID x 0.1 long. Also, the two CS111 spacers are replaced by
CS202 spacers. Four of the CS1 inserts now are CS1A (1/4" x 28 thread). Note
that this change also effects the parts list on several bolts, washers and nuts.
Drawings for CS1A, CS201 and CS202 have been supplied to Brock so he can
manufacture them. Aircraft Spruce and Wicks have all the new hardware in stock.
If you are retrofitting you can drill (#3 drill) the CS1 spacers and tap 1/4 x
28 thread. **SKETCHES OMITTED**
VARIEZE PLANS CHANGES
Section I
chap 19 add "pitch system rod-ends from the elevators to the front stick (four
total) have been changed to HM-4 size. See CP#20 for details".
Section I pg 2-1 & 2-2 Revise the bill of materials as follows to reflect
changes required to change to the HM-4 rod-ends.
Subtract
(4) HM-3 (1) AN3-11A
(4) VECS13 (1) AN3-15A
(1) AN3-16A
(4) MS21042-3 (1) AN3-7A
(2) CS111 Spacers (4) AN 315-3
(4) CS1 inserts
Add
(4) HM-4 (1) AN4-7A
(4) CS201 (1) AN4-12A
(2) CS202 (2) AN4-16A
(4) AN316-4
(4) MS21042-4
(4) CS1A inserts
From CP49 dated July, 1986
FIREWALLS AND FIRE PROTECTION OF FLIGHT CONTROLS
The study of VariEze accident history has always shown considerably reduced
incidents of fire as a result of an accident than the conventional metal
aircraft with the engine on the front. The reasons for this are relatively
obvious in that the sources of ignition of the fire are more remote to the major
impact. Another feature that has been considered safer than the tractor aircraft
is the airflow pattern through the engine area which pulls the fire away from
the aircraft rather than impinging it toward the firewall. There have been no
accidents or incidents in the VariEze or Long-EZ that have been caused by fire
destroying aircraft structure or flight controls. There may be, however, a
possibility of this occurring and this possibility is something that we feel
obligated to address and, thus, are recommending specific modifications to the
VariEze, Defiant and Long-EZ to reduce, as much as possible, the exposure to
this risk.
Several years ago, we tested a product called Liquid Firewall and found it did not provide satisfactory fireproofing/insulation and, thus, did not recommend its use and, in fact, specifically cautioned those who would attempt substituting it for the recommended firewall. A couple of weeks ago, Wicks Aircraft sent us a new product (Ocean 1644 Intumescent) to evaluate. This material is intumescent which means it swells up to a very thick layer of high temperature insulation and provides surprising results in that it will protect an aluminum surface from fire damage for a considerable time period. We do not have the equipment to specifically qualify this material to FAR 23 regulations, however the torch tests we have conducted have convinced us that it can provide a considerable barrier to deterioration by fire to aluminum or composite structure. The other good news is that this material costs considerably less than the previous liquid protection product.
Because of our concern that it may be possible to suffer unacceptable structural damage or loss of flight controls, we are recommending mandatory changes in this newsletter to all our designs except the Solitaire. This is particularly important in the VariEze and Long-EZ where both yaw and roll systems pass through the engine compartment. Loss of roll control on a Defiant may allow recovery using rudder.
PLANS CHANGES
We at RAF, of course, cannot enforce a mandatory change, as FAA can on a
type-certified aircraft. The regulations allowing amateur-built experimental
aircraft recognize that the homebuilder is the aircraft manufacturer and, that
the aircraft does not need to conform to certification giving him the freedom to
develop new ideas. FAA achieves their goal of providing adequate public safety
by restricting the homebuilder to unpopulated areas and to solo flight until his
aircraft is proven safe.
It is the homebuilder's responsibility to maintain, inspect and modify his aircraft as he desires. However, we at RAF feel that part of our job is to provide information to the homebuilder in the form of recommendations that, in our opinion, are required for him to achieve a satisfactory level of flight safety.
Modify the roll and yaw
control systems between the firewall and the wing roots by substituting 4130
steel or any stainless steel for all aluminum components with thicknesses less
than 0.1 inches. This includes tubes, pushrods (with inserts), pulley brackets
and bellcrank brackets. Apply Ocean No. 1644 Flexibilized - Intumescent
Fireproof Coating Compound to the aft face of the centersection spar including
interior flange surfaces between the existing firewall and the wing root rib. If
your Fiberfrax shield is aluminum rather than the stainless steel option, coat
its aft surface with Ocean 1644 Intumescent. Inspect all fuel system plumbing
and fuel system components for approved fireproof components. Substitute
approved fireproof components (steel or stainless) for any aluminum components
and be sure that fireproof sleeves are used on all hose components. Any exposed
aluminum tubing or fittings should be corrected with approved stainless steel or
steel aircraft fitting. If your gasolator bowl is aluminum, wrap it with
approved fire sleeve material similar to the hose sleeves.
LONG-EZ PLANS CHANGES
LPC #130 MAN-GRD Add to owners manual page 16. "Clear" idling engine every 15
seconds or so on the approach. Also, always fly final with the speed brake and
at an altitude to allow reaching the runway without the engine after retracting
the speed brake. Accounting for deceleration to the stall speed, this can be
done from a 3 degree flight path at 1/2 mile final.
LPC #131 MAN-GRD Modify the roll and yaw control systems between the firewall
and the aluminum protective ribs at the wing roots by substituting 4130 steel or
any stainless steel for all aluminum components with thicknesses less than 0.1
inches. This includes tubes, pushrods (with inserts), pulley brackets and
bellcrank brackets. Apply Ocean No.1644 Flexibilized - Intumescent Fireproof
Coating Compound to the engine-side surface of the aluminum wing root shield
ribs. Apply Ocean 1644 Intumescent to the aft surface of the centersection spar
including interior flange surfaces between the existing firewall and the wing
root rib. If your Fiberfrax shield is aluminum rather than the stainless steel
option, coat its aft surface with Ocean 1644 Intumescent. Inspect all fuel
system plumbing and fuel system components for approved fireproof components.
Substitute approved fireproof components (steel or stainless) for any aluminum
components and be sure that fireproof sleeves are used on all hose components.
Any exposed aluminum tubing or fittings should be corrected with approved
stainless steel or steel aircraft fitting. If your gascolator bowl is aluminum,
wrap it with approved fire sleeve material similar to the hose sleeves.
From CP50 dated October, 1986
Clarification of changes to VariEze and Long-EZ control systems aft of the firewall called out in CP 49. As any plans owner knows, the aileron control system aft of the firewall consists of aluminum pushrods and several thin aluminum brackets. The intent of the plans change is to assure that an EZ pilot will retain, at least, roll and pitch control in the event of a serious engine compartment fire. Obviously, pitch control would not be effected by an engine fire, but it may be possible that an aluminum pushrod or aluminum bracket might be melted thus robbing an EZ pilot of lateral (roll) control in the event of a serious but otherwise survivable engine compartment fire. For this reason, we have carefully evaluated the control system for fire survivability. We have decided to only preserve the lateral (roll) control system, and to let the directional (rudders & brakes) system go. Our reasoning is that in such a serious situation as a bad engine compartment fire, the most important thing is for the pilot to retain sufficient control to be able to safely execute an immediate emergency landing. Pitch and roll control are all that are absolutely necessary for this. Stopping, once on the ground, can be accomplished by collapsing the nosewheel.
Toward this end, we are
recommending in the strongest possible terms, the direct replacement of all
aluminum pushrods aft of the firewall, with 1/2" O.D. x .028" wall 4130N steel
tubing. The CS-1 aluminum threaded inserts in the ends of the aluminum pushrods
should be replaced by steel inserts (part #CS-50). These inserts should slip
inside the 1/2" O.D. x .028" wall steel tubes and should be fastened with four
(4) stainless steel pop rivets, such as Cherry #CCP-42. Your existing dash 3
rod-ends can be screwed into these CS-50 inserts. In addition the four CS-127
aluminum brackets on the aft face of the VariEze centersection spar and in the
wing root of the Long-EZ must be replaced by steel parts
fabricated from .032 4130N steel. Ken Brock will have both of these parts
available by mid November. They will be cadmium plated steel per RAF's
specification.
Since this was published in CP 49, we have received all kinds of mail, mostly
wanting clarification. Hopefully, the above has done that. We also received a
few derogatory letters suggesting we were simply trying to "cover our -ss".
Obviously, anyone is entitled to his opinion, but you should know that a
decision to make such a change as this one is not taken lightly. First of all,
RAF's agreement with Brock means that RAF has to buy all remaining inventory
such as CS-127 aluminum brackets and CS-1 aluminum threaded inserts.. Secondly,
a change like this is always confusing to many builders and our workload on
builder support goes up dramatically. Thirdly, and most importantly, we have
tried and will continue to try to make any change necessary to make flying RAF
designs safer, no matter what it costs or what anyone thinks. We have an awful
lot of friends out there and are very sincere in our efforts to provide any
information to make flying these airplanes safer. Last but not least, we cannot
force anyone to make any changes, we can only print the suggestions in the CP.
It is up to you whether you comply or not. Naturally, we hope every one will
because these changes are not made on a whim. However, we do not have the
authority to force you to ground your airplane and make the change, only the FAA
can do that and then usually only when it concerns certificated airplanes.
From CP79 Dated October 1994
LONG-EZ PLANS CHANGE
1/2"X.028" WALL STEEL TUBING NO LONGER AVAILABLE.
Ken Brock Mfg. has informed us that the 1/2"x.028" steel tubing called out for use in place of the original aluminum aileron control push rods is no longer available. They will supply 1/2"x.035" wall 4130 steel tubing from now on.
This means that the CS-50
steel inserts originally called out won't fit. Brock has changed the sizes of
the CS-50 to ensure that these inserts do fit the 1/2"x.035" steel push rods.
These inserts have a 10-32 thread machined into them
to accept the dash 3 rod ends.
Cozy-related Changes
Nat had also mentioned in his message to the Cozy mailing list that the Cozy plans had been changed and so I searched for relevant changes from the list on Marc's web Cozy Builders web site that made references the control rod inserts. The changes below related to the inserts are for the first edition plans, but it appears that all editions have the same corrections applied to them with respect to CS-50 inserts and changing all the rod ends from MM-3 to HM-4.
Misc:
An interesting discovery when researching this topic was that the Cozy plans have
CS-1 and CS-1A drawings that are different than the equivalent parts in the LongEZ plans.
Below are the drawings that appear in the Cozy first edition plans:
Please note that these rod ends are shorter than the LongEZ plans (1" length for both vs. 1.4" and 1.7" for the CS-1 and CS-1A respectively in the LongEZ plans) and they have a 1/4" flange on them and are made of steel (STL) instead of 2024-T3 aluminum. In addition, the inside appears to be opened up to a different and unspecified diameter where the part isn't tapped. The LongEZ inserts have a single diameter thru hole. In the latest catalog from Ken Brock Manufacturing, there are two distinctly different pictures shown for CS-50 and CS-1A. Brock no longer shows the CS-1s in their catalog and has not for some time.
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Another interesting side subject is that it would appear that the CS-50 never had a drawing for it published anywhere that I could find. I haven't seen a print of it in any of the CPs that mentioned the CS-50. So there is no reference to it having been changed from 10-32 to 1/4" x 28. It had also undergone a change at some point to reduce its OD from .441" to .427" to slip fit inside the .035" wall thickness 4130 tubing probably around October 1994 as mentioned in that edition of the CP.
I have a good friend who built a LongEZ and he is helping me with the Cozy and this topic has consumed more than a few minutes of discussion, ranging from whether steel rivets should be used in the engine compartment (such as the Cherry CCP-43 rivets mentioned in CP50 instead of the solid aluminum rivets) to whether the 1" length of the CS-50 inserts leaves enough room to install the rivets and still have room available for adjusting the HM-4 rod ends. Incidentally, I'm using MM-4 rod ends which are a "form-fit-function" replacement for the HM-4s because the Heim parts cost more than twice as much ($13.50 vs. $5.70). I couldn't understand why the rod end was changed from an MM-3 (Aurora) to the much more expensive HM-4 (Heim) part since the MM-4's were already called out for the elevator rod ends in the Cozy plans. The LongEZ plans use the HM parts exclusively, presumably because there was no equivalent available from Aurora at the time.
So, to recap what I've discovered:
In April 1979, RAF decided to increase the rod ends from HM-3 to HM-4 (10-32 to 1/4-28) after a report that a builder had broken a rod end on the elevator pushrods during installation. This necessitated a new part, the CS-1A insert made of the same material, 2024-T3 aluminum, identical to the CS-1 except it had a 1/4-28 thread. This changed only 4 push rod ends and inserts for the elevator pushrod and the pushrod between the front and back stick. The other 8 push rod inserts were left at the original size. It's interesting to note that the LongEZ only had two CS-1A inserts on the elevator pushrod, with the front/back control stick linking pushrod still using the CS-1.
In July, 1986 RAF announced a mandatory modification to the roll and yaw control systems between the firewall and the wing roots by substituting 4130 steel or any stainless steel for all aluminum components with thicknesses less than 0.1 inches. This included tubes, pushrods (with inserts), pulley brackets and bellcrank brackets. Details of how to make these changes to the push rod inserts were not discussed.
The October, 1986 CP 50 clarified the previous mandatory change and announced the availability of the CS-50 control rod insert for the first time. No drawing of CS-50 was made public and the only text description was that the part was made of 4130 steel and otherwise identical to CS-1 except with a larger diameter to slip fit inside .028" wall thickness tubing. The mix of rod ends in the LongEZ would thus have been: 2 CS-1A inserts/HM-4 rod ends for the elevator, 2 CS-1 inserts/HM-3 rod ends for the tube that ties the front/back control sticks together, 8 CS-50 inserts/HM-3 rod ends in the engine compartment.
In October of 1994 due to a lack of availability of .028" wall thickness 4130 tubing, RAF announced in the CP-79 that the CS-50 would be reduced in diameter to fit .035" wall thickness tubing.
Some time after this, the CS-50 rod insert was modified to accept a 1/4" x 28 thread thus necessitating the change of all remaining -3 rod ends to -4s on the Cozy MKIV. Also, the parts that connect to these rod ends had to have their holes opened to .250 to accommodate the larger diameter hardware to fit in the bearing at the end of the -4 rod ends. Since the CS-50 rod insert is shared with the LongEZ and Varieze, this would affect those planes as well if someone was attempting to update their control system. There may have been a similar announcement in a CP beyond CP-82 (Oct. 1995) but I don't have a copy of those CPs so I cannot say for sure.
My take on these changes:
It would appear that these changes were initiated by an isolated report of breaking an HM-3 rod and a change motivated by an accident involving an engine compartment fire. By some strange coincidence, I had actually met the builder who had broken his rod end while sitting in his Varieze. When I asked him how much force had been used to cause the -3 rod end to fail, he said, 'almost none'. Then I had noted that the -3 insert was held in place by a locking nut. I figured he'd applied too much torque to the locking nut to the point of causing the part to nearly fail completely. Then when he was sitting in the fuselage, yanking away on the stick and making airplane noises, the part failed the rest of the way. He seemed quite proud that he had uncovered what he had considered to be a design flaw when he had more than likely had a workmanship defect of which he was completely unaware. In any event, that's something that other builders might have done as well so increasing the rod ends to MM-4s was a good change.
The second set of changes, precipitated by a fatal crash that was related to an engine compartment fire, and one in which the controls were functional all the way to the forced landing, looks to be a change aimed at mitigating potential liability claims. I could imagine that a fire in the engine compartment is likely to go unnoticed on a pusher aircraft until something very serious gets the pilot's attention, perhaps a very high CHT reading or the failure of a critical control. In any event, a device that would provide an early detection of an engine fire would be a lot more useful than a set of controls that would still be functional after the spar and wings had burned off the plane. That way the pilot has a chance of turning off the potential fuel source, assuming a fuel leak, while quickly looking for a place to land.
In addition to these changes, I intend to install a set of temperature sensors to monitor the air entry/exit temperatures for signs of an engine compartment fire although it's hard to know how effective monitoring a change in temperature through the engine compartment will be for that purpose. If nothing else, it may provide a little peace of mind, just like my all-steel controls in the engine compartment.
Send feedback to Lee Devlin regarding this topic