The Duncan Download Blog: Business Aviation Advice & Observations

Contributed by Bob Tooker, Propeller Sales and Tech Rep

As a part of regular maintenance, aircraft propellers require periodic greasing. The frequency depends on the propeller model and application.

Before you begin to grease the propellers yourself, always review the manufacturer owner’s manual on proper procedures. If you aren’t familiar with these guidelines, it is easy to over-grease your propeller, potentially causing the following consequences.

1. Overspeed Propeller

In extreme situations, the propeller can rotate beyond its designed limit. Overspeed conditions can greatly reduce the life of your propeller and engine and in extreme cases lead to catastrophic failure.

2. Leaking Blade Seal

Over-greasing a propeller may cause grease to bypass the blade-to-hub seal or the clamp parting line gaskets, leading to excessive leaking.

3. Excessive Vibration

An over-greased propeller can become out-of-balance causing excessive vibration and unnecessary wear on the engine and propeller.

Duncan Aviation's propeller shop provides extensive propeller maintenance and overhaul services, and we hold OEM Authorizations for Raisbeck and Hartzell propellers. We also maintain a large inventory of business aircraft parts for sale.

Bob Tooker is an aircraft parts consignment expert specializing in quality control and export documentation. His aviation career began in 1967.

Contributed by Adrian Chene, Avionics Tech Rep.

When a high-speed data (HSD) failure is in an ancillary system, such as Sat AFIS or ACARS, I genuinely recommend hiring a professional to assist you. It will be money well spent. However, if you are determined to proceed on your own, do two things:

1. Determine if the satellite terminal is passing the AFIS traffic to the ground network. Your service provider should be able to assist with this.
2. Ensure that your satcom service provider routed your request to the proper location at the datalink provider’s end.

Unfortunately, there is often a fair amount of blame that occurs between satcom and datalink service providers. In many cases they are companies with competing services. To reduce confusion and root out the error relatively quickly, get both parties on a conference call. In most cases, AFIS / ACARS problems are often resolved at the datalink provider’s end.

These systems are very complex. I cannot stress enough the importance of getting advanced troubleshooters involved early.

For help troubleshooting an internet connection issue in your aircraft, contact the Duncan Avionics installation and line maintenance location nearest you.

Adrian Chene is an Avionics Tech Rep for Duncan Aviation. He provides troubleshooting and technical advice on avionics installation services, and specializes in custom, integrated HSD solutions. He began working in aviation in 1996.

Contributed by Adrian Chene, Avionics Tech Rep.

High-speed data (HSD) failures are difficult to troubleshoot, and require several different skill sets. The most important skill needed is knowing which questions will yield the best results. The price for poor troubleshooting is very high, and my number one recommendation is to get advanced troubleshooting experts involved early.

Here are four steps to troubleshoot why passengers can’t connect to the internet onboard an aircraft. I will also explore each topic in further detail in future posts.

1. Check the router.

Plug a laptop into a ‘hardwired’ Ethernet port in the cabin to verify the router is powered and other basic functions are operable (an internet connection is not necessary). If the Ethernet ports are functioning, but the Wi-Fi is dead, then there is a problem with the router.

2. Verify there wasn’t a connection loss.

There are times and places where connectivity will be lost due to congestion. This is more common in afternoons and airspaces where lots of users are logged in, like New York City or Chicago. It is also common to momentarily lose connectivity when switching between satellite signals during transcontinental flights. Your service provider should be able to tell you if a connection failure was caused by congestion or while switching satellites.

3. Send fault logs to the service provider and equipment manufacturer.

Most HSD terminals have fault logs that can be downloaded to assist in troubleshooting. Send these logs to your service provider and equipment manufacturer technical reps.

I always recommend that operators contact their field service and equipment manufacturer technical representatives, and get them involved early. If you don’t know who your representatives are, ask the facility that installed the equipment. 

4. Hire a professional for ancillary system troubleshooting.

For ancillary system issues, such as Sat AFIS/ACARS, save your time and hire a professional to assist you. In many cases the satcom and datalink service providers are companies with competing services, and unfortunately a fair amount of accusation can take place between the two. To reduce confusion and root out the error relatively quickly, get both parties on a conference call.

For help troubleshooting an internet connection issue in your aircraft, contact the Duncan Avionics installation and line maintenance location nearest you.

Adrian Chene is an Avionics Tech Rep for Duncan Aviation. He provides troubleshooting and technical advice on avionics installation services, and specializes in custom, integrated HSD solutions. He began working in aviation in 1996.

Contributed by Don Fiedler, Manager of Component Solutions Business Development

Having the right information about the circumstances surrounding a squawk can save your avionics tech many hours of troubleshooting time (and yourself a considerable amount of money) for an avionics repair.

When a unit arrives at the shop for repair, sometimes the squawk is obvious; however, there are many times when it is not. Before sending in your unit for repair, be prepared with the answers to these two questions.

1. When does the squawk occur?

• Does the unit get too cold on the ramp (wintertime) or at altitude?
• Does the unit get too hot (summertime) or after the unit has been in operation for a while?
• Does the squawk occur intermittently?

2. What happens at the time of the squawk or its resolution?

• Is there vibration? Some aircraft produce more vibration than others.
• Is it overheating after long operation?
• Is there poor or no cooling to the unit?
• If the unit gets too cold at altitude and is located outside the cabin, what does the OAT indicate?
• Does the squawk occur in precipitation?

Many times the problem is related to other aspects of the flight or external conditions and may only fail on the bench when these conditions can be recreated. Taking note of the conditions when the component or system fails, is essential to the effective and timely resolution of the problem.

It’s also important to communicate this information when you ship the unit in for repair. It’s always a good idea to include a printed copy with the unit, and to follow-up a phone conversation with an e-mail of the critical details.

To find out more about Duncan Aviation's avionics repair services, contact an Avionics/Instruments Customer Service Representative.

Don Fiedler manages business development for Duncan Aviation’s Component Solutions program in Lincoln, Neb. He specializes in working with OEMs and vendors to expand Duncan's avionics service capabilities. He began working in aviation in 1962.

Contributed By Dennis VanStrien, Airframe Service Sales Rep

Mobile service units are in the headlines a lot these days. Most of the big aircraft service names have them and there are also a lot of smaller operations throughout the United States. They offer everything from cleaning to AOG emergencies to engine changes and even major inspections.

So, how do you know when mobile aircraft service is a good option for you? Here are three things to consider:

1. Downtime

Sometimes a road team will be able to solve a problem faster than you can, and can reach you in a time frame that may compete with a full-service facility's onsite availability.

This is true for troubleshooting and AOG parts situations. You can get the team and the parts to your location in relatively short order and be back in the air in no time. However, for larger jobs, it may take a road team longer than a full team at a service center. Two or three guys working dozens of labor hours will just take longer than five to six guys working an inspection on round-the clock shifts.

2. Cost

Using road teams spares you the cost of moving your airplane to a full-service facility, and for someone to travel with it to watch over the maintenance. A mobile team can be a good solution for an in-house team that needs a day or two of technical or heavy help, but can handle the rest of the inspection on their own.

However, road teams cost more. You are paying for their time, door-to-door service and in many cases their expenses. Convenience costs more.

3. Unforeseen Complications

What if an inspection uncovers something that needs more time, tools, parts or expertise to fix? The short answer is you are most likely in for more downtime. For instance, a cracked window. A repair in the field would extend the downtime, while a repair at a full-service facility would not.

So, consider your options and choose wisely. Sometimes service from a professional team in your hangar can be a real benefit. And sometimes it's just better to take your aircraft to a full-service facility. The great news is you have the choice!

Dennis VanStrien is an Airframe Service Sales Rep at Duncan Aviation's Battle Creek, Mich. facility, and specializes in Citation aircraft. He began working in aviation in 1976.

Contributed by Curt Campbell, Avionics Tech Rep with permission from Carter Hart of Airframe Service

Last week I received a call from Carter Hart of Airframe Service, who was working with an autopilot problem. The autopilot would engage properly, but would immediately disengage as soon as the pitch servo tried to drive the elevator.

The autopilot computer had been sent to the factory but was returned with no fault found. Through several telephone conversations, Carter and I concentrated on the autopilot pitch trim operation and troubleshot the aircraft wiring, and measured voltages and verified logic conditions in the aircraft. This process led to the discovery of a shorted diode internal to the horizontal stabilizer actuator.

Checking with our accessory technicians, it was determined that we could repair the actuator the same day it was received. The stabilizer actuator was pulled by Carter on Thursday and arrived at Duncan Aviation on Friday. The unit was inspected, repaired and returned to service that same day then shipped back to Carter for delivery on Saturday. Carter reports the aircraft is now flying fine.

Duncan Aviation autopilot technicians have seen the isolation diodes in the stab actuator fail before, and we are trained to assist in diagnosing this problem without having to pull the stab from the aircraft. We can provide one-day repairs on all Learjet stab actuators if we are given prior notice of the unit coming in.

Contact Curt Campbell or an Accessory Technical Representative for troubleshooting assistance.

Written by Larry Troyer, Avionics Tech Rep

The FZ-500 Flight Director computer that is installed in many business aircraft and King Airs provides the mode annunciator drive out to the mode selector annunciators. If some of the mode annunciators do not test or light up the problem may be the FZ-500 computer. However, it could also be the lamp in the mode selector switch.

Great care should always be taken when replacing the lamps in the mode selector. Due to the construction of the switch sockets, it is possible to short the bulb supply voltage to the control terminal that comes from the FZ-500. This can spike and take out a very expensive part in the FZ-500 computer.

Contributed by Jeffery A Witt, Team Leader, Pneumatics

If your passengers or crew are beginning to complain about uncomfortable cabin temperatures, it is time to take a look at your aircraft's air conditioning system. The following is one of the most common solutions.

Stop the squawks. Change your socks!

The coalescer assembly is responsible for separating water from the air being introduced into the cabin. Unfortunately over time the coalescer fabric collects dirt and dust and the efficiency of the assembly is significantly reduced. Occasionally ice will build up on the safety valve contained inside the assembly and almost always causes the air to bypass the coalescer sock allowing moist air to enter the cabin, increasing the humidity, which in turn increases the likelihood of corrosion and the probability that passengers and crew will begin to feel the uncomfortable effects.

It is very simple to replace the coalescer socks and bags to increase the airflow to the cabin. Duncan Aviation is able to replace coalescer bags and socks on a send in basis on Falcon 900 & 2000, Beechjet 400 and Challenger 600 & 601.

Written by Dan Magnus, Avionics Tech Rep

Honeywell's GNS-XLS is a Flight Management System that provides control for an aircraft's navigation sensors, computer-based flight planning, fuel management and frequency management, among many other necessary capabilities. When this unit begins to malfunction, it is critical to get it back on line quickly.

I recently fielded a phone call from a DOM asking for troubleshooting advice when the screen on the GNS-XLS went white. Here are the steps I used to determine the cause and provide the solution.

The best way to determine if a unit is faulty is to install another and see if the squawk disappears. I sent out a loaner to arrive the next day. After the unit was installed, the screen remained white, telling me it wasn't the unit causing the squawk.

Next, I had him unhook the antenna. This immediately brought the screen back to its normal state. We replaced the antenna and the system is back on-line.

Squawk solved.  

If you need help troubleshooting or repairing your avionics, contact Avionics Tech Support.

A Learjet 35 pilot reported intermittent audio clacker in his headset, even though the stab actuator was not trimming. The audio clacker is designed to alert the pilot when the horizontal stabilizer actuator is trimming.

At Duncan Aviation, we connected the stab actuator to a Learjet test stand for function testing. The results indicated that everything was working properly. Knowing we couldn't give the unit back with a No Fault Found, we investigated and tested further.

With the trim-in-motion potentiometer connected to an "analog" Simpson meter, we ran the stab actuator the full length of its travel. We discovered if we stopped the stab actuator in a specific spot and lightly tapped on the potentiometer, the analog meter would read an erratic resistance (the needle jumped around). A change in resistance triggers the audio clacker in the pilot's head set.

After replacing the trim-in-motion potentiometer and retesting the whole unit, no other faults appeared. On the next trip, the pilot reported the audio clacker only went off when the horizontal stabilizer actuator was really trimming.

Written by Chris Gress, Component Solutions Manager