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The Duncan Download Blog: Business Aviation Advice & Observations

Learjet 20/30 Series: Un-Commanded Aux Cabin Heat

Posted by Diane Heiserman on Wed, May 15, 2013 @ 06:00 AM

Submitted by Dave Schiver, Airframe Tech Rep

This is an update to the Duncan Intelligence article I wrote in December of 2011 about an aging aircraft issue in regards to the Aux Cabin Heat in 20 & 30 Series Learjets not equipped with a Meggitt (formerly known as Keith Products) freon system. This topic was discussed during the NBAA Learjet Technical Committee meeting in February 2012, resulting in Learjet subsequently releasing AFM Temp Rev 2013-01.

Original Duncan Intelligence Article

Without a command from the crew, anytime the main ship batteries were turned on, all four of the heating coils in the Aux Cabin Heat system would power on and heat. Upon further investigation, it was discovered that both sides of the P/J-190 connector (ref 21-42-00 in your applicable W/D), that connects the main heating coil power going into the Aux Cabin Heat Relay box, was internally shorted. Both the P- and the J- side were shorted. As a result, anytime the battery charging buss was powered, which is when either Main Ship Battery or Generator is on-line, there was power to the heating coils of the Aux Cabin Heat system.

P/J-190 connectorP/J-190 connectorP/J-190 connector

Internally shorted P/J-190 connector

If you check the W/D in regards to the power wires that normally go to the power relays (K17 and K18), you will notice the only protection is a single 150A current limiter (FL3).

Please Note
Since the “P” side is shorted, the heating coils will heat even without the Aux Cabin Heat Relay Panel (E33) installed in the aircraft. With this failure, ALL of the safety features on the control side are ineffective in disabling the heating coils. The only way to remove power from the heating coils is to turn OFF both generators and both main ship batteries. This leaves the Emergency Power Supply (EPS) providing the only electrical power for the aircraft. As per the 35 AFM, aircraft equipped with a single EPS will have electrical power available for approximately 30 minutes in this configuration.

P/J-190 connector wiring diagramP/J-190 connector wiring diagram

P/J-190 connector Wiring Diagram

Dave Schiver is an Airframe Technical Representative at Duncan Aviation’s Lincoln, Nebr. (LNK) facility. He specializes in Learjet aircraft. His aviation career began in 1981.

Tags: Troubleshooting, Learjet

Two Notices of Proposed Rulemaking Issued for Learjet

Posted by Diane Heiserman on Tue, Apr 09, 2013 @ 06:00 AM

Submitted by Dave Schiver, Airframe Tech Rep

On March 27th, the FAA issued two Notices of Proposed Rulemaking (NPRM) for Learjet 60 and Learjet 40/45. Continue reading for details.

NPRM Learjet

Learjet 60

The FAA has proposed an upcoming Airworthiness Directive (AD) for Squat Switch & Anti-Skid Shielding on certain model Learjet 60 aircraft. You are encouraged to read the details of and comment about the proposed AD during the open commenting period which ends on May 13, 2013. Details of the Notice of Proposed Rulemaking can be found here.

Required Service Bulletins

This proposed AD will require the installation of the following Service Bulletins (SB): SB60-32-33 & SB60-57-7. These SBs install the metal shielding around the Main Landing Gear (MLG) Squat Switches & MLG Anti-Skid Valves to protect them in case of an accidental impact.

Terminating AD 2010-11-11

The above SBs are two of the four required SBs to terminate AD 2010-11-11. This AD is the 96-Hour Tire Pressure check, per the FAA Alternate Method Of Compliance (AMOC) Letter L115W-12-459. The other required SBs are SB60-27-6, Wheel Speed Detect Box, and SB60-78-7, Thrust Reverser (TR) Interface Box.

Another requirement called out in the AMOC is for the Temporary Flight Manual Change (TFM) 2012-03 to be inserted in the Airplane Flight Manual (AFM). Bombardier first published this information in AW32-061 on July 30, 2012.

SB60-78-7

As a side note, in order to comply with SB60-78-7, the Wheel Speed Detect Box, if previously installed, may need to be exchanged in order to be upgraded for compatibility with the TR Interface Box.

Learjet 40/45

The FAA has proposed an upcoming AD for the Baggage Door Fire Seal of certain model Learjet 40/45 aircraft. You are encouraged to read the details of and comment about the proposed AD during the open commenting period which ends on May 13, 2013. Details of the Notice of Proposed Rulemaking (NPRM) can be read here.

Required Service Bulletins

The proposed AD requires the installation of SB40-25-25, Revision 3, or SB40-25-25, Revision 3, within 300 flight hours after the effective date of the AD. These SBs call for the modification of the fire seal on the baggage door, including doing general visual inspections of the fire seal for correct contact.

Exceptions

If Revision 1 or 2 of SBs SB40-25-25 / SB45-25-35 have been complied with prior to the effective date of this proposed AD, no further action is required.

All of Duncan Aviation's full-service locations are Authorized Learjet Service Centers, and are able to provide comprehensive Learjet airframe services, inspections and technical support for all models.

Dave Schiver is an Airframe Technical Representative at Duncan Aviation’s Lincoln, Nebr. (LNK) facility. He specializes in Learjet aircraft. His aviation career began in 1981.

Tags: Regulations, Airframe Maintenance, Learjet

Learjet Tire Changes: Clearing up the Confusion

Posted by Diane Heiserman on Tue, Jan 22, 2013 @ 03:45 PM

Contributed by Dave Schiver, Airframe Tech Rep.

Wheel and Tire Assy

At the end of the day, the person responsible for ensuring ALL requirements are met is the one doing the installation.

Within the last few weeks at Duncan Aviation, we’ve had discussions about tire changes on Learjets and other make/model aircraft and what criteria to use when replacing a tire. It sounds pretty simple, but there is a lot of confusing and conflicting information you should be aware of. 

CMM & AMM Mismatch

There are aircraft maintenance providers that will replace your tire using only the Component Maintenance Manual (CMM) and have the 8130 state that as their only reference data. But when was the last time you looked in your aircraft maintenance manual (AMM) to confirm that this met all the stated requirements?

The AMMs for Learjet 31, 35, 36 & 60 series call out the replacement of ALL the self-locking nuts when re-assembling the wheel halves. Yet the 20 series and 55s do not, at least not at this time. I would be surprised if this is not changed in the next revision.

Wheel & Tire Assembly

Are you aware of what criteria were used on your last tire change?

There is one P/N wheel and tire assembly that can be used across more than one model line. During your last tire change, if only the CMM was referenced and this assembly was installed on your Lear 31, it is possible it does not meet the airworthiness standards for your aircraft since the CMM does not state to replace all the self-locking nuts on every tire change as it does in chapter 32 of the AMM for that model.

Also note, we have seen other OEMs place other requirements such as eddy current and Chapter 5 Requirements on wheel and tire assemblies over and above what the CMM calls out that are installed on their aircraft.

At the end of the day, who is responsible for ensuring ALL requirements are met when installing ANY part on an aircraft? That’s right… the one doing the installation. In most cases, that is probably YOU.

Help Us Serve You Better

When contacting Duncan Aviation's Accessories Department to send a wheel and tire assembly in for a tire change, please state which aircraft maintenance manual you would like us to reference to ensure we comply with all the requirements that you, as the installer, will need.

Dave Schiver is an Airframe Technical Representative at Duncan Aviation’s Lincoln, Nebr. (LNK) facility. He specializes in Learjet aircraft. His aviation career began in 1981.

Tags: Parts & Accessories, Learjet

Five Consequences of Ignoring Landing Gear Trunnion Corrosion

Posted by Diane Heiserman on Tue, Jan 08, 2013 @ 04:04 PM

Contributed by Dave Schiver, Airframe Tech Rep.

Learjet Trunnion Fixture

A unique Duncan Aviation solution saves the customer more than six months of downtime and a significant amount of money.

Corrosion Ignored never stops!

Due to its location and exposure to the elements, landing gear is highly susceptible to corrosion. And corrosion, even in small amounts, will not stop growing until it is effectively removed. If left unattended, landing gear corrosion can grow and jeopardize the functionality and airworthiness of the unit leading to expensive repairs or the premature removal of components.

As a Learjet (non 40/45) owner/operator, I want to advise you of a corrosive situation that can occur on all Learjet model aircraft, excluding the 40/45. These aircraft are susceptible to corrosion in the sockets for the main landing gear forward trunnion pins on the bottom side of the wing. Corrosion in this area is serious if left unattended, with the potential to cause cracks in the weakened casting and eventual failure resulting in a potential gear collapse.

Five consequences of ignoring Learjet (non 40/45) landing gear trunnion corrosion.

  1. Increased repair costs requiring the sending of the wing to the OEM for repair or even complete wing replacement.
  2. FAA violations for not following the maintenance manual which requires the repair of all corrosion.
  3. If corrosion is ignored for too long, the castings will have to be replaced.
  4. Corrosion can spread into the adjacent spar which translates into a longer downtime and more money to replace the spar, if not scrapping the entire wing.
  5. Catastrophic failure of the Main Landing Gear (MLG) socket resulting in a takeoff, landing or taxi incident leading to injury or loss of life.

Two solutions to trunnion casting corrosion

Replace Trunnion Castings. To replace trunnion castings, the wing will need to be de-mated and shipped to the OEM in Wichita, KS. There it will be placed in the production wing fixture to remove the upper skin and replace the trunnion castings. Depending on the demand for the fixture, we have seen downtimes as long as six months and at a significantly high repair cast.   

Remove Corrosion from Trunnion Casting. Without having to remove the wing, Duncan Aviation is able to remove the corrosion with an on-wing fixture that allows qualified airframe technicians to bore the trunnion and insert a bushing, while staying within allowable limits. This repair process generally takes only 5-7days to complete, eliminating the need for wing removal, shipping, months of down time and at a dramatically less overall cost.

If there is sufficient Ground Support Equipment (GSE) available at your location, this repair can be performed in your hangar by Duncan Aviation’s Engine AOG Rapid Response Teams.

You can read more about this innovative on-wing fixture in the Duncan Debrief. If you have any questions about this or other Learjet technical issues, contact me at anytime. For scheduling and pricing information, contact Learjet Airframe Service Sales Representative Brad Lennemann.

Dave Schiver is an Airframe Technical Representative at Duncan Aviation’s Lincoln, Nebr. (LNK) facility. He specializes in Learjet aircraft. His aviation career began in 1981.

Tags: Learjet, Landing Gear

Learjet Aircraft: Troubleshooting the Master Caution Box

Posted by Diane Heiserman on Mon, Dec 03, 2012 @ 10:01 AM

Contributed by Jerry Cable, Accessory Tech Rep

Master Caution Box

Master Caution Box, P/N 2618055-29, repaired and returned to service by Duncan Aviation electrical technicians.

The Learjet 35/36 model and some Learjet 20s are wired in such a manner that there is potential to cause problems with the Master Caution Box (MCB), P/N 2610855-29 and 2618055-30, which may result in incorrect troubleshooting of the MCB and Glare Shield. It could also result in complete failure of the MCB.

For example: three Transistors (Q210, Q211 and Q212) are mounted in the nose of the aircraft. Transistors Q210 and Q212 control light intensity of the Pilot and Copilot Glare Shield assembly. Transistor Q211 is for a 3.4Vdc regulated voltage Power Supply for the Master Caution Box; that supplies power to the Electronic Integrated Circuit (IC) inside the MCB. The ICs are voltage sensitive with a maximum rating of 15 Volts direct current (Vdc). If transistor Q211 fails, the voltage will be driven to 28 Vdc, nearly twice the maximum voltage that the ICs can handle. This can result in the failure ICs in the MCB.

Care should be taken when installing the new MCB to ensure that unregulated voltage (above 5Vdc) is not applied to the MCB (failed Q211); causing a complete failure of the new MCB. Prior to replacing the MCB; Q211, insulator and hardware should be checked or replaced.

If in doubt, these transistors are easy to access and cheap enough to warrant changing them at regular intervals.

Recommended procedures when replacing or troubleshooting the MCB

  1. Check the GROUND leads from the master caution connectors to aircraft ground. This is to insure Master Caution Box has proper grounding. Problems caused by grounding issues can be numerous; from completely inoperative and intermittent to erroneous caution trips. Troubleshooting this problem can be a daunting task but will save time and money in the long run.
  2. Verify TRANSISTOR Q211 is working properly and replace if needed. A failure of this transistor will allow the unregulated voltage to be applied to the MCB, leading to a complete failure when power is applied to the aircraft.

For exact details including “pin outs,” connectors, meter readings, etc.; contact Duncan Aviation’s Accessory Electrical Team Leader Tim Smith.

Now through the end of January 2013, save $100 on your next repair, overhaul or functional test on your electrical and pneumatic units. Download the details and coupon here

Jerry Cable is an Accessories Tech Rep located at Duncan Aviation’s Lincoln, Nebr., facility. He is a landing gear and accessory components and systems specialist. His aviation career began in 1991.

Tags: Parts & Accessories, Troubleshooting, Learjet

Learjet 45: Windshield Coupe Rail Inspection

Posted by Diane Heiserman on Thu, Jul 19, 2012 @ 10:00 AM

Contributed by Dave Schiver, Airframe Tech Rep

Learjet 45 coupe rails inspection

The coupe rail inspection cannot be avoided. Don't put off getting it scheduled.

Bombardier has issued a recommended Service Bulletin (SB 45-56-3) that calls for the inspection of the windshield coupe rails on all Learjet 45 models -005 through -427, that needs to be completed within the next 600 flight hours or 36 months of the original basic issue date of the SB (April 30, 2012).

This requires the aircraft to be shored-up with the main cabin doors closed while the windshields are removed and the support structure is inspected with ultrasound and Eddy Eurrent inspection. The coupe rails will be re-identified one of two ways depending upon the inspection results. One part number for a 5,000 hr. re-inspect, and another PN if no further inspections are required. If the coupe rails are found to be outside of acceptable tolerance, the rails must be replaced immediately.

3 Possible Outcomes

Keep in mind when planning for this inspection, there are three possible outcomes.

  1. The rails are fine and no replacement is necessary
  2. The rails are acceptable but need to be re-inspected within 5000 hours per Chapter 5.
  3. The rails are outside acceptable limits and need to be replaced immediately at the Bombardier Business Aircraft Service Center in Wichita.

There is no way to know the results until the rail inspection is performed.

Don't Procrastinate

This is an inspection that you will have to do sooner or later. You will be tempted to put it off as long as possible. Don't. Postponing will only result in your heightened frustration because a hundred other operators, who also waited, are scrambling for the few time slots and parts available. The longer you wait for this inspection, the longer you will wait to be scheduled. Don't be that guy!

Parts and labor are covered by this inspection if the work is performed at the Original Equipment Manufacturer (OEM) or a Learjet Authorized Service Facility. Travel expenses for a Mobile Repair Party (MRP) from Learjet and Paragon are not part of the Bombardier Service Bulletin coverage.

If you have any questions, please don’t hesitate to ask.

Dave Schiver is an Airframe Technical Representative at Duncan Aviation’s Lincoln, Nebr. (LNK) facility. He specializes in Learjet aircraft. His aviation career began in 1981.

Tags: Airframe Maintenance, Learjet

Learjet 40/45 8-Year Landing Gear Inspection Bottleneck Anticipated

Posted by Diane Heiserman on Tue, Feb 28, 2012 @ 06:00 AM

Contributed by Dave Schiver, Airframe Tech Rep

Learjet LH Main Landing Gear

If you wait too long to schedule the 8-year gear inspection on your Lear 40/45, you may be waiting longer than you want.

Between now and July 6, 2012, a potential bottleneck and scheduling conflicts could occur as an unknown number of Learjet 40/45 gear sets come due for the 8-year gear inspection. This applies to the main struts and main landing gear (side stay) actuators.

This deadline is dictated by a note included when IRNs 3220018 and 3220111 were published. This note stated, “On A/C with over 6 years from C of A, perform inspection within 24-months of July 6, 2010.”  

There are a limited number of Heroux-Devtek Authorized Maintenance providers able to perform this inspection. At present the vendor is estimating a turntime of 15 calendar days. This does not include the added time necessary for the removal, shipping and reinstallation.  

Avoid The Last Minute Rush

You can avoid the last minute rush and scheduling conflicts by choosing to do your 8-year gear inspection early in combination with a larger Learjet maintenance inspection that requires a longer downtime.

I recommend you get this on your calendar soon. As the July 6, 2012, deadline approaches, I anticipate the turntime will only increase.

Gear Log Book

Upon completion of the 8-year gear inspection, you will receive a gear log book for each strut and actuator. If you have had any components replaced or had loaners installed (i.e. axles), providing any landing differentials upfront will ensure that you receive an accurate log book for your gear.

All of Duncan Aviation's full-service locations are Authorized Learjet Service Centers, and are able to provide comprehensive Learjet airframe services, inspections and technical support for all models.

Dave Schiver is an Airframe Technical Representative at Duncan Aviation’s Lincoln, Nebr. (LNK) facility. He specializes in Learjet aircraft. His aviation career began in 1981.

Tags: Parts & Accessories, Learjet

Duncan Aviation Technicians Travel the World in 2011

Posted by Diane Heiserman on Wed, Jan 25, 2012 @ 10:04 AM

In 2011, Duncan Aviation team members made hundreds of trips around the world providing AOG services. While providing the most-needed AOG services to our customers on nearly every Continent, team members also took in some local culture, food and sites.

Berlin, Germany

Berlin, Germany

In March, Scott Shefke, Challenger/Global Tech Rep, traveled to Berlin,Germany, to perform and assess the viability of restoring a Challenger CL 604 to airworthiness status. The project included performing engine boroscopes, performance runs, system operations checks, fuel sampling and general condition of aircraft.

“Berlin is a magnificent city to visit,” says Scott. “It is rich with history.”

Cairo, Egypt

Cairo, Egypt

In Cairo, Egypt, Dan Soderstrom, Master Turbine Engine Mechanic, and Bill Walker, Engine Tech Rep, were in the right place at the right time when one project turned into two. While troubleshooting a faulty fuel control unit on a Hawker 800XP, a local Hawker 850XP operator approached them for assistance in fixing leaking starter/generator seals.

Both Dan and Bill said that everyone they had contact with in Egypt were very nice and helpful. Dan hopes to have more opportunity to see the great city if he gets the chance to go in the future.  

Bordeaux, France

St. Emilion, France

Ron Grose, Falcon Tech Rep, attended the annual Falcon 7X Steering Committee meeting in May, in Bordeaux, France, a beautiful old city located in southwestern France along the Garonne River, surrounded by elite vineyards. As a member of the steering committee, Ron and others oversee the development of the scheduled maintenance program for the Falcon 7X aircraft.

One of Ron’s favorite places to visit was the small village of Saint Emilion. It is a 1,700 year old village which was, at one time, surrounded by a large moat used for protection against the warring tribes. This quaint village had narrow cobblestone streets, great restaurants and many wine tasting shops.

Brisbane, Australia

Brisbane, Australia

Duncan Aviation Fuel System Lead Technician, Jon Abrahamsen, took a week long trip to Australia in May. He was dispatched to repair a wing junction plate fuel leak on a Falcon 2000EX.

Jon used one of his days to drive two hours down to Surfers Paradise, a large tourist beach. He also took the train downtown to the south shore for dinner and a couple of local beers. Jon says the area was beautiful.

Shanghai, China

Shanghai, China

Scott Howell, Airframe Lead Mechanic, along with three other fellow Duncan Aviation team members, traveled to Shanghai, China to complete a crucial fix on a Falcon 7X. Getting tools and equipment through customs posed a challenge, but the team stuck to the task, completing the project early.

On the first full day of their trip, the group made their way to The Bund, a mile long street lined with shopping. A local gentleman led them beyond the glamour of these stores to another area. Here, they had the adventure of walking up steep wooden stairs, entering into random people’s homes, where they bargained with local merchants for various items. It is an experience they will not soon forget. Scott describes the city’s transportation as very convenient and clean. The food was not what he would have suspected, but enjoyed trying the various delicacies of the region. 

Santo Domingo, Dominican Republic

Ned Shanks, Engine Rapid Response Tech out of Fort Lauderdale, FL, made a trip to Santo Domingo, Chile, in October to assist a customer. The #1 engine on their Lear 35 would not start. Having seen this squawk many times before, Ned suspected there was an issue with the aircraft’s igniter box and prepared for his trip with this in mind. This was a very important job because the aircraft was an air ambulance and was scheduled to fly a sick infant back to the United States for medical care.

After arriving, clearing Customs and making it to the aircraft, Ned quickly discovered his suspicions were correct, a failed igniter box. As soon as he complied with the removal and replacement of the box, ground runs and required paperwork, they were airborne and on their way back to Ft. Lauderdale. Shortly after arrival back home, the aircraft was prepped and sent out on another rescue mission.

Tags: Learjet, Falcon, AOG, Hawker, Challenger

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