The Duncan Download Blog: Business Aviation Advice & Observations

Most communication systems on aircraft are relatively simple, with a transmitter/receiver, corresponding antenna and a controller. However, the HF system is more complex with additional components needed to get the job done.

Duncan Aviation avionic tech reps, Dan Magnus and Scott McKenzie, field numerous calls weekly from pilots, directors of maintenance and aviation technicians around the world needing assistance in troubleshooting their HF systems when they squawk. At the upcoming Aircraft Electronics Association (AEA) U.S. East Regional Meeting at Fort Lauderdale, Florida, Dan and Scott will put their combined years of experience together for a joint training session to assist attendees in understanding common HF issues.

Their class, HF Mysteries in Troubleshooting, will be at 8 a.m. on Friday, September 27, 2013, at the Hilton Fort Lauderdale Marina Convention Center in in Fort Lauderdale, Florida. They will cover the basics of HF technology and get into the quirks inherent in these systems. Discussion will include tuning, grounding and idiosyncrasies of different systems, as well as antennas. The session will conclude with a Q&A session and the critical exchange of pilot and crew debriefs.

You can register for any AEA meeting, by visiting https://www.aea.net/events.asp. While there plan on stopping by Duncan Aviation’s table to speak to all of our avionics experts representing.

 Dan Magnus is an avionics instrument technical representative located at Duncan Aviation's Lincoln, Neb., location. He specializes in ADF, Comms, Control Heads, CVR, DME Gables Control Heads, Receivers, Nav-Comm/Receivers, Radar Systems, GPS, GNS, Transponders and UNS Components and Systems Specialist. His aviation career began in 1976.

Scott McKenzie is an avionics tech rep located in Duncan Aviation's Lincoln, Nebraska, facility. He specializes in troubleshooting the latest in avionics systems installed on aircraft today. His aviation career began in 1995.

Contributed by Dan Magnus, avionics instruments tech rep

Honeywell BA-141 altitude indicators and SI 225/285 airspeed indicators are avionics units common to a variety of jet aircraft. When these units are sent in to Duncan Aviation for repair, one of the most common squawks reported is pointer jitter. Pointer jitter occurs when the indicator's pointer oscillates or vibrates and does not give a clear reading. This squawk can be caused by a dirty sycho, defective potentiometers or power supply capacitors that get weak over time. If the pointer jitters badly enough, it can and does cause a flagging issue during flight.

Troubleshooting

It is a very simple process to troubleshoot altitude and airspeed indicators if you have a spare indicator available. If you do not have a spare indicator, Duncan Aviation has a loaner available.

Replace the suspect unit with a spare unit. If the problem goes away, the indicator is faulty. If the problem remains, the fault is elsewhere, most likely with the air data computer (ADC).

Both the altitude and airspeed indicators provide valuable information to the pilot, but cannot function on their own. They are fed the information from the ADC and in turn report the appropriate information to the pilot. It is not uncommon for these indicators to be blamed for a squawk that resides in the ADC.

When sending the units to Duncan Aviation for repair or overhaul, it is always a good practice to send both the indicator and ADC together. This allows our avionics technicians to identify the cause much quicker and act accordingly. Every unit sent in will be inspected for cleanliness, damaged or broken parts and loose screws. It is put through a full function test that includes inspection of the lights, wiring and electronic components.

Honeywell BA-141 Altitude Indicators

If you send Duncan Aviation your Honeywell BA-141 altitude indicator and your air data computer at the same time, we will certify and return them with an altitude correction card. We must have both the ADC and the BA-141 altitude indicator in order to certify and return with an altitude correction card.

Duncan Aviation is the only Honeywell Authorized Service provider for these units. If you should have any questions regarding these units, don’t hesitate to contact me. To schedule a repair or overhaul event, contact any one of our Duncan Aviation avionics customer account reps. 

Dan Magnus is an avionics instrument technical representative located at Duncan Aviation's Lincoln, Neb., location. He specializes in ADF, Comms, Control Heads, CVR, DME Gables Control Heads, Receivers, Nav-Comm/Receivers, Radar Systems, GPS, GNS, Transponders and UNS Components and Systems Specialist. His aviation career began in 1976.

Dan Magnus, avionics instruments tech rep

Northern Airborne Technology Ltd (NAT), dba Cobham Avionics, designs and produces avionics communications equipment installed aboard helicopters. These units control the audio voice transmissions between the pilot and co-pilot and from the cockpit to the crew/cabin.

One of the more common failures that Duncan Aviation technicians have experienced with these units is intermittent audio squawks. The audio transmitted by these units passes through relays or electronic switches. As relays begin to lose conductivity causing poor contact, intermittent audio is the result. At this point the unit needs to be repaired or overhauled.

If you build it, they will come

Duncan Aviation has full overhaul and repair capabilities on many NAT units. These capabilities are continually growing as customers call and request to send their units to Duncan Aviation for repair or overhaul. If a request comes in and we don’t have a current test set capable of repairing their unit, we build it. And it doesn’t take as long as you might think. We are able to order the manual, build a test set, perform the repair or overhaul AND return the unit to the customer typically quicker than the OEM can do a repair.

Cobham (NAT) repair and overhaul capabilities

Duncan Aviation currently has a total of 12 test sets specifically built to troubleshoot and test hundreds of different Cobham (NAT) models and part numbers. Call a Duncan Aviation avionics tech rep to inquire about our repair and overhaul capabilities for your Cobham (NAT) unit.

Duncan Aviation provides comprehensive avionics and instrument overhaul and repair services, and we are an avionics and instrument authorized service center for more than 50 of the top equipment manufacturers. Our capabilities listings are available online in our inventory and capabilities search.

Dan Magnus is an avionics instrument technical representative located at Duncan Aviation's Lincoln, Neb., location. He specializes in ADF, Comms, Control Heads, CVR, DME Gables Control Heads, Receivers, Nav-Comm/Receivers, Radar Systems, GPS, GNS, Transponders and UNS Components and Systems Specialist. His aviation career began in 1976.

Submitted byCurt Campbell, Avionics Tech Rep

Per the L-3 Communications Vertical Gyro (VG206D) Component Maintenance Manual the table below lists the components that must be replaced with the new OEM components to comprise a complete overhaul of the displacement gyroscope.

L-3 Overhaul Components

At Duncan Aviation we do more than what is required; we do the right thing.

During a VG206D overhaul, Duncan Aviation replaces all of the above components. If we were to stop there, the overhauls would be correct according to maintenance manual requirements and the vertical gyro could be returned to service with no issues. This is where most component service facilities stop when overhauling a vertical gyro. Duncan Aviation doesn’t stop here. Twelve additional components, such as the Electrolytic Leveling Switches, are replaced. We do these, not so we can charge more, but because it is necessary and the right additional steps to take.

Electrolytic Leveling Switches

There are two electrolytic leveling switches inside your L-3 Vertical Gyro. These gravity-sensitive switches are sealed glass tubes partially filled with electrolytic solution and three electrodes. They are attached to the inner axis assembly via a bracket. They detect movement; one about the roll axis, the other the pitch axis.

The life cycle of these switches varies and depends on many factors, such as how many times the gyro gets powered up and how long the flights are. But the big factor is how long and many times the pilot uses the gyro fast erect switch. The point is this: the life cycle cannot be predicted, but when they blow, and they will, they explode with such force that glass shrapnel is thrown everywhere, damaging anything in its path. I’ve seen fragments destroy brackets and cut synchro or torque motor windings. Some of the most damage caused by an exploding switch are to the pitch shaft assembly (list replacement cost $1,100), pitch torque motor ($800) and roll synchro ($600). The damage can only be repaired with a complete overhaul of the unit.

Because of our years of knowledge and experience repairing the damage after an electrolytic leveling switch blows, we included its replacement as part of our overhaul. Doing only what is required is not always doing what’s right.

These are the additional Duncan Aviation components that are replaced during overhaul.

These are overhaul components that we inspect for failure during an overhaul and will replace when necessary.

If you have questions about the overhaul of your L-3 Vertical Gyro, do not hesitate to contact a Duncan Aviation Avionics Tech Rep. To schedule your next VG overhaul, contact a Duncan Aviation Customer Account Rep.

Curt Campbell is a Duncan Aviation Avionics Tech Reps. located in Lincoln, NE, specializing in troubleshooting squawks and offering tech support for business aircraft avionics and instruments. Curt's aviation career began in 1975.

By Kevin Miesbach, Shop Manager-Avionics/Instruments

On Monday, June 3, Duncan Aviation consolidated its Shipping and Receiving operations with all shipments to Duncan Aviation-Lincoln now going to one new centralized receiving location. This move improves the efficiency of how packages are received and moved about the company, resulting in many customer benefits.

Consolidated Shipping Services

Customers will no longer have to ship their accessory or avionics units to different physical addresses at the Lincoln Airport to reach the Duncan Aviation shop performing the work or needing the parts. That means whether customers are shipping an accessory item for repair or overhaul, an avionics unit for repair or overhaul, or sending Duncan Aviation an inventory of parts for consignment, they will be able to use the same address.

FedEx Zip Code –68500

As part of consolidation, Duncan Aviation has obtained a special zip code for use in the FedEx shipping system. All packages addressed to this zip code are delivered by FedEx to Duncan Aviation’s Lincoln facility first thing in the morning.

When sending units to Duncan Aviation via FedEx, please use the following address and zip code:

Duncan Aviation, Inc.
Shipping and Receiving
4001 N Park Rd
Lincoln, NE  68500

Reduced Turntimes

The consolidated shipping, along with radio frequency scanning technology implemented in Duncan Aviation’s package receiving process, allows for more efficient shipment receiving and dissemination. Units make their way from the receiving dock to the repair shop and ultimately the workbench even quicker than before and are able to see real-time when an expected unit is received into the system. And customer paperwork is electronically attached to the work order for a more efficient process all-around. We look forward to our customers experiencing the financial and turntime benefits of the new receiving procedures.

No AOG Shipping Charges

All Duncan Aviation customers who need AOG services and use the special FedEx zip code of 68500 no longer need to mark and pay for the “EARLY AM” service from FedEx. Technicians have already been reporting AOG units arriving earlier than the previous “EARLY AM” shipments.

Other Carrier Shipping

When sending units to Duncan Aviation via any other shipping carrier, please use the following address and zip code:

For the most efficient service, it is best to use the shipping addresses as outlined above. However, we have been assured by our carriers that if you forget and use the old addresses, shipments will still make it to Duncan Aviation and the proper shops.

Duncan Aviation's Component Solutions offers extensive aircraft parts repair and overhaul services—including loaners and exchanges—for avionics, instruments, parts and accessories, at the same time maintaining a large inventory of aircraft parts for sale. Their streamlined services and competitive turntimes satisfy hundreds of requests throughout the world 24 hours a day, 7 seven days a week.

Reproduced with permission from Avionics News, May 2013

At the 2013 Aircraft Electronics Association International Convention & Trade Show, Gary Harpster of Duncan Aviation was elected as the new chair of the AEA board of directors. Recently, Patricia Luebke, Avionics News contributor, spoke with Harpster to learn more about his background and aspirations as AEA’s newest chairman.

What does being AEA’s chair of the board of directors mean to you?

One thing I’ve learned throughout the years is that people assimilate new information in a multitude of different fashions. I’ve always prided myself at being able to listen and not form any opinions until the final person has spoken. I hope I can use this characteristic in this new role. The AEA has been working hard to become a sound resource for accurate aviation information, so when we convey a message to the members, we need to be conscious about how it’s perceived. The AEA has a good track record, and I want to build on that.

Do you have a specific agenda in your new leadership role?

I’m not so sure I have a specific agenda, as much as a desire to contribute 110 percent of whatever is asked of me during this time. There are lots of different avenues a person could delve into, but I want to make sure the board supports a coordinated effort that returns the most benefit to the AEA members. I know one effort will be to introduce members to the various committees the AEA has and encourage more members to find a topic of interest and serve on a related committee. It is vital that we continue to seek opinions, network with each other and become more involved in our industry and its future.

Is there a particular area that interests you as chairman?

Duncan Aviation is the largest privately held MRO (maintenance repair and overhaul) facility in the world, so we not only work on a large variety of aircraft on a daily basis, we have worldwide exposure, as well. I’m hoping I can pass on ideas for other facilities to consider as work opportunities and/or solutions. Right now, the AEA has a great relationship with the FAA, so I’d like to get a chance to contribute ideas that would allow our members to do what they enjoy with a less cumbersome bureaucracy and, hopefully, fewer paperwork challenges

What is your background?

I grew up next to Eppley Airfield in Omaha, Neb. We lived about 3 miles from the airport, so whenever there was an opportunity, my sister and I would ride our bikes by the airfield and wait on the approach end of the runway for aircraft to pass overhead. As soon as they were right on top of us, we would stand up and let the prop blast blow us down the hill. This avionics was in the early 1960s, long before we had the security we have today. We would come home smelling like kerosene that permeated our clothes, so my mother knew right away where we’d been. I still can’t help but look up every time a plane passes overhead.

Click here to read Patricia Luebke’s complete interview with Gary Harpster.

Submitted by Scott McKenzie, Avionics Tech Rep

Last summer I wrote an article about the importance of complying with Airworthiness Directive (AD) 2010-07-02 before the deadline of November 3, 2012. This AD is applicable to the Honeywell RNZ-850/851 Integrated Navigation Units (INU) and addresses possible erroneous glide slope or localizer display indications. The deadline has since come and gone, however, at Duncan Aviation we continue to field phone calls from operators who have discovered their AD had been signed off as being complied with, when in fact, it has not. Cessna released CIL-34-02 on March 18, 2013, to address this issue.

Honeywell RNZ-850/851 Data Plates

There are two data plates on the Honeywell RNZ-850/851 INU. One is on the front, the other on the bottom. There is confusion about which data plate should be inspected to determine if your unit is in compliance with AD 2010-07-02. The answer is BOTH. Two conditions must be met in order for the unit to be in compliance.

Condition #1: Front Data Plate Closely inspect the mod data plate on the front of the unit. In order to be compliant, the square with the “AS” must be blocked out.

Condition #2: Bottom Data Plate Next inspect the status of the mod data plate on the bottom of the unit. In order to be compliant, the square “T” must be blocked out.

Important Note

Your unit is only in compliance with AD 2010-07-02, when BOTH of these conditions are met.

Duncan Aviation can perform the modification necessary to comply with AD2010-07-02. Contact a Duncan Aviation Avionics Tech Rep for more information.

Contributed by Nic Evans, Avionics Team Leader

It wasn’t long ago that I wrote an article about how to properly handle your aircraft’s gyroscope and prevent it from being scrambled. To some, this advice may seem obvious and unnecessary, but it continues to amaze me how little thought and effort is given when a gyroscope is packaged and shipped to Duncan Aviation for repair and overhaul. The gyros that are sent in for repair or overhaul with improper packaging have shown a higher degree of damage as a result.

The following are common squawks that can and do occur when a gyroscope is not prepared properly for shipping.

1. Rocky Bearings – The bearings within a gyro work together to keep the unit balanced. A rocky bearing occurs when a unit is jostled and causes these bearings to misshapen and stick. This can cause your gyro to be slow to slave or slow to erect.
2. Out of balance – A gyro becomes out of balance when the weights within the unit shift or slide.
3. Catastrophic failure – There are stops inside a gyro that are in place to prevent a catastrophic failure of a unit. However, a seemingly innocent drop during shipping can break those stops and render the unit inoperable. Just because the box isn’t damaged doesn’t mean the unit inside isn’t.

The best way to ship a gyro is in the same box and packing material it was received in from the manufacturer. However, if that box is long gone, your efforts to prepare your gyro for shipment should be equal to or better than the manufacturer’s packaging. If you take shortcuts when shipping a gyro, you run the risk of voiding all applicable warranties.

Two Box Shipping Method

When the original packing boxes and materials are long gone, the best way to pack a gyroscope for shipping is to use a two-box method. This will ensure that unit is packed securely and more protected against inappropriate handling during transportation.

Step One: Box #1

Place the gyro in a box that is just large enough to hold the unit and enough Styrofoam or other soft packing material to line all sides, including top and bottom. Be sure to include enough packing material so the gyroscope will not shift in the box during shipping. It is better to use too much than not enough.

Step Two: Box #2

After the box containing the unit has been closed and sealed, pack it into a larger box with additional packing material. Do not skimp on the size of the box #2 or the amount of packing materials. The second box must be large enough to fit Box #1 and still allow for at least two inches of packing material between any point of the box and the inside walls of the carton. Make sure that Box #1 will not shift or the packing material to become compressed during shipment.

I cannot stress enough how fragile and delicate of an instrument a gyroscope is. You invest a lot of money keeping gyros airworthy. Duncan Aviation does not want to see your money and effort wasted because of improper shipping, handling and procedures.

Gyro Overhaul

As an Authorized Honeywell Service Center, Duncan Aviation is able to overhaul most Honeywell gyroscopes. If you ship your gyro directly to Duncan aviation for overhaul, you will receive it back within five days using Duncan Aviation's AOG service.

Duncan Aviation has four Avionics Tech Reps at your service to answer your questions or assist in troubleshooting your avionics units, including the gyro.

Contributed by Scott McKenzie, Avionics Tech Rep and Rod Walther, NAV Team Leader

The Universal Avionics Flight Management System (FMS) has two batteries. One is located on the CPU board that supports Flight Plans and Navigation databases. The other is located on the GPS board and supports the GPS Almanac information. It isn’t unusual for these batteries to begin to lose power or fail with minimal warning resulting in a CDU Data Bus Failure message being displayed.

As previously stated, this failure can happen quite suddenly. The crew may get a “Low Battery” message at start-up on the first leg of a flight, but then have a “CDU Data Bus Failure” message on the start-up of the return flight. When this happens, the FMS becomes unusable until the battery is replaced. Depending on your current flight schedule and where you are located, the downtime could be hours or even days. Especially if it becomes necessary to order a rental unit from the OEM while your unit is sent in for battery replacement.

When there is sudden battery failure, you also lose valuable Pilot Data. After this failure is noted, the only way to replace the data is for pilots to manually re-enter the data after the batteries are replaced.

Below are two simple solutions to avoiding the sudden loss of battery power and potentially all of your stored pilot data.

Two-Year Maintenance Program

It is perfectly fine to retain the original Universal Avionics FMS batteries. However, we recommend that you tie the battery replacement to an airframe maintenance event already on a two-year general maintenance program. The original Universal Avionics FMS batteries are still currently available, however could at some point in the future be discontinued. At that time, operators will need to switch to the new Extended-Life battery modification.

New Extended-Life Battery Modification

Universal Avionics has issued a battery modification that considerably extends the useful life of the batteries. More importantly, this new battery appears to have a steadier decline in voltage, prolonging the low battery indication which in turn, could allow the pilot up to three months to schedule maintenance. However, to ensure continuous battery operation, we recommend you put the FMS with the new battery modification, on a four-year general maintenance program for battery replacement, reducing the likelihood of the sudden loss of battery power and pilot data. If you do this on a dual FMS System, you will save hundreds of dollars of maintenance over the life of the battery.

CPU Board Damage

Waiting too long to replace your FMS batteries also increases the probability of CPU board damage due to battery corrosion. Although a battery may have exceeded its life expectancy, the longer battery replacement is put off, the greater the chances the battery will begin to leak and cause corrosion and damage to the CPU board. When this happens, the CPU board must be replaced at a potential cost of more than $3000.

Both the two-year maintenance cycle of the current FMS battery and the new Extended-Life battery modification can be performed at Duncan Aviation. And by using Duncan Aviation's AOG service, turn time can be as little as one day, if scheduled. To discuss your Universal Avionics FMS Battery maintenance options, call Duncan Aviation’s Avionics Tech Reps.

To schedule your next Universal Avionics FMS battery maintenance event, contact Duncan Aviation’s Avionics Customer Account Reps.

Scott McKenzie is an avionics tech rep located in Duncan Aviation's Lincoln, Nebraska, facility. He specializes in troubleshooting the latest in avionics systems installed on aircraft today. His aviation career began in 1995.

Rod Walther is an avionics team leader located at Duncan Aviation's Lincoln, Nebraska, facility. He leads a team that specializes in NAV systems. His aviation career began in 1993.

Contributed by Scott McKenzie, Avionics Tech Rep and Nic Evans, Gyroscope Team Leader

Gyros are an essential piece of business aircraft avionics equipment and you invest a lot of money to keep them airworthy. They can operate properly for many years or fail in just a few days, whether new in the box or overhauled. It all boils down to the environment in which it is operating and how well you take care of it. When the OEM prints the words “Handle Like Eggs” across every unit, they mean it!

Here are a few things to keep in mind when handling the gyro.

Proper Gyro Handling

1. Allow the aircraft to come to a complete stop and sit for at least 15 minutes minimum before attempting to remove the gyro. This gives the gyro time to completely spool down and stop spinning. The newer and more efficient the unit, the longer the gyro will spin.
2. Handle Like Eggs, seriously! During transportation is when potentially serious problems can occur. You may send in a unit for a simple fix, but if it is not properly packaged and shipped, then you increase the likelihood of it arriving with a more serious problem. To minimize ground turbulence, a gyro should be shipped by air.
3. Do not unplug or plug your gyro in with aircraft power on. Gyros should only be connected or disconnected after they have spooled down completely, minimizing the chance of any excessive vibration from installing or removing the connector to damage the gyro. 
4. Unpack your overhauled gyro at the aircraft to avoid rumbling it across the ramp on a cart. Dropping a gyro from ½” above a hard surface can do significant damage.

When you need to remove the gyro from the aircraft to troubleshoot squawks or gain further access, the same care should be used.

Proper Gyro Storage

1. Anytime a gyro is removed from the aircraft, it should be immediately put into an adequately padded shipping container, if possible.  
2. Store the gyro flat on a shelf resting on padding in a temperature controlled environment.
3. If gyro will be stored for an extended period of time, it should be powered up every six months and allowed to spin for 10-15 minutes. This redistributes the oil or grease throughout the bearings. If left to sit, the oil and grease will pool at the bottom of the unit and cause friction damage of the upper bearings upon the next start-up.

Remember that a gyro is like an egg, unless you want it scrambled, handle accordingly.

Gyro Overhaul

As an Authorized Honeywell Service Center, Duncan Aviation is able to overhaul most Honeywell gyroscopes. If you ship your gyro directly to Duncan aviation for overhaul, you will receive it back within five days using Duncan Aviation's AOG service. Before shipping your gyro to Duncan Aviation for overhaul, please call a Customer Account Rep to get proper packing instructions.

Duncan Aviation has four Avionics Tech Reps at your service to answer your questions or assist in troubleshooting your avionics units, including the gyro.

Scott McKenzie is an avionics tech rep located in Duncan Aviation's Lincoln, Nebraska, facility. He specializes in troubleshooting the latest in avionics systems installed on aircraft today. His aviation career began in 1995.

Nic Evans is an avionics team leader located at Duncan Aviation's Lincoln, Nebraska, facility. He leads a team that specializes in the gyroscope. His aviation career began in 1999.