AMOC, AD92-12-02

Attached is the AMOC for the aileron push pull tube inspections (AD92-12-02)
LINK

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Trimec has noted that they are finding instances of the flap drive cable housing ends coming loose on the braided housings. This is cause for replacement. This is a manufacturer defect. Pay close attention to this area during the routine inspections. If the housing comes out of the fitting, debris could enter the housing during operation causing cable failure.

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Flight Controls:
On February 2nd 2009, IAI released the CAA approved Service Bulletin 1124-27-156. This bulletin is for the replacement of the left and the right aileron control rod assemblies. To see and download this SB follow this link; http://www.worthingtonav.com/downloads/24sb-156.pdf.

The parts required to accomplish this service bulletin can be purchased from Worthington Aviation Parts Inc. They can be purchased in a kit, Part No. 1124-27-126 Kit or individually, Part No. 513020-503. Please contact the Westwind Sales team at 877-833-2942 or fax at 651-393-3308.

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When accomplishing the inspection on the flexible flap drive cable, look at the attaching hardware for the cables to the actuators. We have had several instances of the hardware splitting and the cables becoming loose.

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During routine inspections, carefully look at the elevator torque tube in the inboard bearing areas. There is a steel bushing on the tube that is supposed to be tight on the tube. This is the wear surface for the support bearings. We are finding that they may be loose enough to move by hand. If left uncorrected the bushing can move out of position causing excessive movement on the torque tube and no surface for the bearing to ride on.

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Aileron Push Pull Tubes
It was brought to our attention that FAA AD92-12-02 and IAI SB 1124-27-144 are not in agreement. An Alternate Method of Compliance (AMOC) has been completed by the FAA to correct the disparity. The AD states to replace the existing control rods P/N 513506-503 with a P/N 513506-503RE or -503RD. The issue is when you comply with the SB 1124-27-144 by replacing the offending push pull tubes with the stainless 513506-505, you are no longer in compliance with the AD

Please refer to the IAI AMM 27-00-00 Flight Controls
Contact Worthington for a copy of the AMOC for your records (ANM-116-08-182R1)

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We continue to find flap vanes not shimmed correctly. This condition will and does cause the potted inserts to fail which causes the forward vane rib and spar to crack. Vane replacement is very expensive. The correct way to install a vane is detailed in chapter 27-50-00, giving the correct amount of shimming washers. If the brackets seem to be under a spread pre-load, adjust the shims to correct. Remember that the instructions call out to re-install the same amount of shims previously removed –“BUT”- this is correct only if the previous technician installed the vane correctly.

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Flap Limit Switches
With the issuance of Service Bulletin 1124-27-153, Mandatory Replacement of the Inboard Flap Actuators, it is an excellent time to inspect the position switches on the actuators. The left actuator has six and the right has two. Pay particular attention to the rollers; check them for flat spots and ease of turning. A drop of LPS 1 on each one will help prevent further problems. Make sure the arms are true and not bent; if they are bent, now is a great time to replace them. Wringing out the switches can also be done at this time. Make sure the 0°, 40°, and 42° switches are good; if high resistance is noted, replace the switch. If you find multiple problems, you would be money and time ahead to replace the entire switch rack.

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When the rudder is removed for any reason, take a look inside the torque tube (rudder post). there has been found quite a bit of debris accumulated at the bottom. There is no drain for this area, so any water, paint stripper, etc. will remain, possibly leading to corrosion. We have removed several for cleaning, inspection. and corrosion treatment and have had to replace one.

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Nitrogen Bottle Service Life
The nitrogen storage bottles have a 24-year service life starting at the date of manufacture, NOT the date when it was placed in service as Israel Aircraft Industries (IAI) thinks and Chapter 5 states. Pacific-Scientific, who makes the bottles, issued a letter stating the life limit begins at date of manufacture. If you need a copy, let us know. The same criterion applies to any pressurized container carried on or in an aircraft such as portable fire bottles, oxygen bottles, etc. Next time the bottles are removed, enter the date of manufacture in the logbook.

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Rear Horizontal Splice
We continue to get phone calls concerning the rear horizontal spar splice radial and axial play. Everybody wants to just jump in and replace the bushings and bearings. In fact, this is a major undertaking, requiring precise measurements and controls. Most, if not all, of these “excessive“ clearance problems can be brought under control by reading and applying Service Bulletin (SB) 1124-55-021 Paragraph E. sub. Paragraph 1.9 thru 1.12. It is a simple procedure that has excellent results. We have found that when the aircraft is re-assembled following splice replacement, the radial and axial measurements are already at or very near the limits called out in the Maintenance Manual, even with the splice having new bushings. It’s frustrating to the shop that after all that work, the tail is still “loose”. Using the above SB procedure will, in most cases, fix the problem. At the same time, take a look at the forward scissors, which have replaceable bushings. Keep them tight with shimming when needed.

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Rudder Trim
Several new Westwind operators have called us asking why their aircraft “wing walks”. We have heard this same question for years, so we thought we would offer a few suggestions to help correct the problem. First, though, the pilot and mechanic need to understand the difference between wing walk and “Dutch roll”. The first is a roll axis problem and the second is a yaw axis problem—two different controls with very similar characteristics. Almost every Westwind we have worked this problem on has turned out to have a very slight Dutch roll. In almost every case, we were able to either eliminate the problem or lessen it to a greater degree by doing the following:

1. Run the rudder trim to the right stop and hold the trim switch in that position for 2-3 seconds. (DO NOT depend on the trim indicator for any of this.)
2. Run the trim to the left stop and again hold the switch.
3. Center the trim and go fly.

The trim actuators are not connected and will run at slightly different speeds. Over a period of time, they will position themselves out of rig and will bend the tab out of shape—causing a Dutch roll. Synchronizing the actuators again will straighten the tab. Don’t worry, it doesn’t hurt the tab at all.

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Aileron Cross-Over Cable Maintenance
Recently, while working with Trimec Aviation, I noticed they had found three aileron crossover cables thatwere worn with broken cable strands in them. No big deal, except that it just so happened to be during the last three 800-hour “C” Inspections that they accomplished. Even though bad things seem to come in threes, I still sensed that there seemed to be a trend starting here. I chatted with the one of the lead technicians, Jay Stewart, about this in much more detail. Jay gave me the rundown on his technique for inspecting the flight control cables. First and foremost, clean the cables thoroughly; there are no super mechanics with x-ray vision to see through the filth that collects all over the cables. Next, and you may note this to be a very important step, blow-dry the cables with compressed air to remove the grime stuck between the cable strands. Finally, once the cables are clean, they can be visually inspected. Areas of importance to look at are on the rear cross-over cable at the rear outboard pulleys (see detail “A”). While moving the ailerons through their full travel, look for shiny spots on the cable where it contacts the pulley assembly. A shiny spot may indicate wear, and it will need to be looked at through a magnifying lens. If wear on the cable strands is more than 40 to 50%, it will need to be replaced. What Trimec has been finding in this area is at least 50% wear with some broken strands as well.Now for the weird part – upon replacing the rear cross-over cable, Trimec has been finding broken cable strands under the other pulleys in that system. The ones that I looked at had absolutely no wear at all, but a closer inspection revealed broken strands. Chapter 27 of the Westwind Maintenance Manual states that any broken strand at a pulley necessitates replacement of that cable as well. If you have to replace the rear cable, it is always a good idea to remove the forward cross-over cable as well for a detailed inspection. It takes only a few more minutes to remove it, once you have the aft one out; so it makes good sense to take the time to look at something that, more than likely, hasn’t been thoroughly looked at in many years. As a matter of fact, every forward cable that Trimec has pulled out recently due to the rear one not passing inspection has broken strands in the pulley areas as well (see detail “B”). Those areas cannot be seen until the cable has been removed. I believe that there is no better aircraft in our industry for the money that will do what the Westwind does. It flies high, it is fast, and it has very long legs, while at the same time being comfortable and actually quite maintenance friendly. But, it “ain’t gettin’ any younger.” As the Westwind 1124/1124A continues to serve us so well, during routine inspections, we are going to find areas that need to be inspected more closely and more attention paid to them.With the help of Trimec Aviation and Worthington Aviation, I hope to be able to supply more information on issues like this in the future.

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Rudder Airworthiness Directive (AD) 2004-14-14
We have received confirmation from the FAA that aircraft that have previously been inspected inaccordance with Section 5-40-03 (dated January 31, 2003) of the structural inspection program (structural“B”) meet the requirements of paragraph (a).We are discussing an adjustment to the AD compliance time of 50 hours with the FAA. It seems that theFAA, Civil Aviation Administration of Israel (CAAI), and Israel Aircraft Industries (IAI) weren’t in agreementas far as the compliance times were concerned. Unfortunately, your local Flight Standards District Office(FSDO) is not authorized to grant an extension to the 50-hour limit. That must be done through the FAA inSeattle using the Alternate Means of Compliance (AMOC) procedure. Contact Dan Rodina at 425-227-2125.He is the FAA person whose name is at the bottom of the AD.

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Lift Dump
Scenario:
During a routine “C” inspection, the required lift dump electrical control check is performed per the1124/1124A Aircraft Maintenance Manual (AMM). Both main gear oleo switches are in the ground position and throttles are at idle during the start of the test. Main hydraulic pressure is applied, the lift dump switch is placed to ON, and the lift dumps deploy. The throttles are advanced, and the lift dumps retract because the open throttle micro-switches remove electrical power from the control valve.The throttles are returned to idle, and the lift dumps re-deploy. The final check requires placing the left and right main gear oleo switches to the flight mode (one at a time) to verify the lift dump ground latching(anti-bounce) circuit operation. However, when either main oleo switch is placed to flight, the lift dumps retract.
Note: There are no wiring problems, and the crew reported no faults prior to the inspection. Remember, a“C” check is in progress.
Answer:
Yes, the lift dumps are working as designed; however, during a “C” check inspection, the forward relay panel located under the copilot’s seat is routinely removed for inspection. Because the lift dump “ground-latching” relay (LDR) is located in this panel, the anti-bounce feature is disabled if the forward relay panel electrical connector is removed. Lift dump control valve electrical control power will still flow through the throttle switches and main gear ground contact switches, but the lift dump latching relay is removed from the lift dump control system because the forward relay panel connector is removed. Hook the electrical connector to the forward panel, and the lift dump functional test should now operate “as advertised.”

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Flight Control Balance And Installation
We have recently discovered several aircraft that have been repainted, and the flight control hinge bolts were painted at the same time. Makes one wonder how the facility balanced the flight controls with them installed on the aircraft.
Customers are advised to ask the selected paint shop how they balanced the flight controls. The procedures require that special tooling be used. It has been our experience that most paint shops do not have this available and just use the old "knife edge" procedure. Nothing could be more wrong, because it results in substantial weight being added to the control surfaces.
Look at the flight controls prior to accepting the aircraft after painting. We find that the floating bushings are bottomed out at the hinge fittings and the controls are not shimmed properly, allowing the control to be loose on the hinges. The elevators will fit the stab hinges either way; however, the correct way is to have the large, rectangular hinge cutout on the bottom and the tapered cutout on the top. Otherwise, interference can result between the hinge and flight control skin. Contrary to what we heard, one shop tell thier customers it is NOT the customer's choice how the elevators are installed.

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Flap Actuator Dust Seal
When accomplishing routine inspections in the area of the flap actuators, pay close attention to the dust seal in the end of the actuator. We find them split or missing. This allows dirt and water to be drawn into the actuator housing, which in turn, leads to corrosion and premature wear of the sleeve bearings and actuator shaft. The dust seal, P/N B132-116-2, is readily available fron the Worthington Aviation parts department.

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Oversized Taper Pins
If during inspection of the elevator torque tube assemblies you find the taper pins flush with the collars or adapters, note that Engineering Order (E.O.) DDWW5533576 allows installation of oversized pins. Don’t just continue to pound the taper pins in trying to tighten them up – DO THE REPAIR!

ATA 27

Flaps Extended, No Retract
Your aircraft has landed at a facility with no maintenance operations on site. The pilot reports the flaps are full down and the flap unbalance light is illuminated. There is not an apparent physical asymmetry between left and right flap surfaces. The fault unbalance condition is thought to be a result of an electrical fault, not a mechanical failure in the flaps drive system.

Question:

1. What action may be taken to retract the flaps to 0° in order to return the aircraft to home base?
2. Once the flaps are retracted, what must be accomplished to render the flaps system inoperative?
3. When the flap unbalance indication exists in flight, is it safe to cycle the flap unbalance test switch in an attempt to clear the fault?

Answer:

1. A maintenance technician may temporarily disconnect the flap comparator asymmetry box electrical connector. This will allow the flaps to be retracted, since the flap comparator relay will be de-energized and allow flap operation. Extreme care must be taken when operating the flaps in this condition. If a true mechanical asymmetry exists, the condition must be thoroughly investigated and the aircraft should not be ferried.
2. The flap comparator box connector must then be re-connected. This will ensure the flaps will not operate if inadvertently commanded to run.
3. No, the unbalance switch should never be used in flight. If the flaps test switch is reset while a true failure exists in flight, the fault may progress to an actual flap asymmetry with negative aerodynamic effects.

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10,000 Hour Replacement Parts
As many aircraft in the Westwind fleet approach the 10,000-hour mark, we have received numerous calls concerning the requirement to replace the thrust reverser feedback cable assembly. Per Service Bulletin (SB)WW-24-13, this requirement applied to serial numbers 187-199 and 201 only. All other aircraft were delivered with the later dash number assembly.

Another item on the 10,000-hour list is the requirement to replace the flap drive cables with new parts. We have found that several of the new cables that we have received, have failed at the end fitting swedge within the first 200 hours of service. It seems that the vendor did not properly crimp the fitting to the braided outer housing, allowing the housing to pull out of the fitting. If you have replaced any of these cables recently, re-inspect them to make sure they are still serviceable.

We are still finding a lot of operators who do not realize that compliance with SB 1124-27-136, Horizontal Stabilizer Trim Actuator Jackscrew Replacement, terminated Airworthiness Directive (AD) 98-20-35. As a reminder, please keep track of the life-limit card for this actuator. Lucas gets really testy when you can’t provide current cycles and hours on the units.
Concerning the trim actuators—pay close attention to the upper rod end bearings. We still find them being pulled from the rod end housings, due to side-loading. In an effort to eliminate this problem, we are testing, inconjunction with Israel Aircraft Industries International (IAII), a different mounting procedure on an aircraft,and so far, it seems to be working fine.

Please remind your maintenance personnel to make an AIRFRAME logbook entry for the 150 Flight Hour Inspection. It is a Chapter 5 requirement and should be accomplished every engine inspection. Be aware that CAMP SYSTEMS does not track this as a 150 Flight Hour Inspection.