The Duncan Download Blog: Business Aviation Advice & Observations

Contributed by Erin Hart, Duncan Aviation Apprentice

Duncan Aviation provides emergency AOG support to grounded aircraft nearly anywhere in the world, making hundreds of service trips a year. In 2010, team members traveled to some of the most exotic locales including such places as Puerto Vallarta, Mexico; Guayaquil, Ecuador; Merida, Mexico; Cairo, Egypt and St. George, Bermuda. While providing the most-needed AOG services to our customers at their location, team members also took in some local culture, food and sites.

Puerto Vallarta, Mexico

In the spring of 2010, avionics tech Gene Dannenberger flew from the Duncan Aviation avionics satellite shop in Sacramento, Cal., to Puerto Vallarta, Mexico, to install a Duncan Aviation repaired radar system in a Jetstar. While there, Gene took advantage of the wonderful weather to become a sightseer at many of the local tourist spots including downtown Puerto Vallarta, the marina and of course, the beach.

While performing this routine maintenance, he was entertained throughout the day with music playing in some nearby trees and was visited by a couple of armed airport guards who came out to watch the radar change.

Guayquil, Ecuador

A quick trip to Ecuador for one Duncan Aviation Engine Rapid Response Team (RRT) technician turned out to be more than expected one day in July. After arriving, Karl Johnson, Rapid Response Team Leader from Fort Lauderdale, Fla. went to work troubleshooting the squawk and quickly discovered a faulty oil pump. James Holmes, an engine tech also from the Fort Lauderdale RRT, hand-delivered the part in order to complete the project on time for the customer. Together they completed the maintenance and headed back to Florida, arriving at 6 a.m. the next morning.

In reflection, Karl admitted that the trip was too short and had he been able to stay longer would have visited a local establishment known for having great steaks.  

Merida, Mexico

Karl's trip to Central America didn’t end in Ecuador. He took three separate trips to Merida, Mexico in a span of about two months. What began as a fuel control change turned into troubleshooting for a compressor stall. Finally, the project came full circle with an engine change two weeks later.

This trip, even with the short time and busy schedule, Karl did find time to enjoy the nice people and good food of Merida, Mexico. “I didn’t have the extra time to learn about the area and culture, but I now know how to drink a Mexican beer the right way.”

If he ever gets the opportunity to return, Karl hopes to visit the Mayan Pyramids.

Cairo, Egypt

Shane Heier, an Engine Tech Rep out of Lincoln, Neb. traveled over 4,000 miles to Cairo, Egypt not once, but twice in 2010. For six days in the heart of the Arabian Desert, Shane’s first trip provided the Egyptian Air Force LRU training for the Honeywell TFE731-5BR engine on their Falcon 20.

Taking advantage of his time in Egypt, he and his wife Katie stayed an extra couple days traveling the region and exploring a land rich in history. Their adventures took them to the Pyramids of Giza, the Cairo Museum, a church in Coptic Cairo and a visit to the Alexandria Library of Alexandria located along the Mediterranean Sea.

A month later, Shane got the chance to visit Cairo again and was accompanied this time by Jeff Sikes, RRT engine tech from Scottsdale, Ariz. Duncan Aviation's Rapid Response Teams support AOG engine emergencies in addition to most scheduled and unscheduled events, including engine changes and that is exactly what brought the two to Cairo. They were dispatched to change an engine for a Dassault Falcon 20 aircraft onsite.

Shane’s time in Egypt was an experience he will not forget and remarks that he would visit again if given the chance.

St. George, Bermuda

A quick trip to change an igniter box meant a short get away for Engine Line lead technician, Eric Perez. Eric was dispatched from Lincoln to St. George for work on a Falcon 50EX.

The trip was short, not allowing much time for sight seeing, but Eric enjoyed his stay at Grotto Bay Beach Resort and the chance to experience the beauty of Bermuda.

Erin Hart is a Duncan Aviation Apprentice working in the Marketing Communications department at the Lincoln Nebraska facility. She began working in aviation in 2007.

Written by Jon Dodson, Duncan Aviation Turbine Engine Service Sales Manager

Over the years I’ve logged countless hours with my hands inside a Honeywell TFE731 turbine engine as an aircraft turbine engine technician. For the last 19 years my perspective has been from the sales desk assisting owners, operators, DOMs, pilots to better understand their engines and how to keep them in the best operating condition for many years of service. Amid the many customer requests, I’ve noticed a recent trend. Occasionally, I’ll get a customer who requests a test cell run be performed on their engines after completion of a Major Periodic Inspection (MPI) and prior to reinstallation. This request tells me there is a misconception about the TFE731 engine. I’m going to take this opportunity to clear it up. The Honeywell manual has never required a test cell run after the completion of an MPI. Where all of a sudden are customers getting the idea they need a test cell run to gauge whether or not the engine is rebuilt correctly? What is the issue or is there an issue at all?    

False Sense of Security

For years, no service center would consider absorbing the time and expense necessary to run the engines through a test cell after an MPI, even if they had the equipment. So Why now? Because they can, it’s about marketing.

They are attempting to differentiate themselves by selling the only thing they have over the competition—the test cell. If they can create a perceived value where there isn’t one, it may be just enough to convince an unsuspecting customer he’s getting something for nothing. This works, because when you create fear, you create a need, and if you happen to have a solution to that “need,” then your marketing efforts have worked. It’s a marketing tool.

An experienced TFE731 engine technician will tell you, creating the need for a test cell run after an MPI is creating a false sense of security. And if you’re being sold on the idea that your test cell run is “free,” rest assured, it is not. The time and expense is being paid for by someone, most likely the unsuspecting customer. Let’s talk about the true need for test cells.

Time & Place

Test cell runs can be beneficial. There are two types of test cell runs, certified and non-certified. Certified runs are a maintenance manual requirement whenever the compressor section of the engine has been dismantled. Non-certified runs are 5-point runs performed in the cell. The Honeywell maintenance manual is very clear when a test cell run is required. In the case of the TFE731 engine, the only time a test cell run is required is when the HP impeller is removed from the HP shaft. An engine can be dismantled to any level up to this point and then be reassembled and returned to service without a test cell run. An MPI is far less invasive because the compressor impeller, core bearings and carbon seal package have not been disturbed.

The test cell run that customers are being sold in addition to their MPI, is the non-certified type. During a non-certified test cell after an MPI, engines are subjected to harsh conditions in an artificial environment for up to an additional three hours of run time. The results mean little because the engine performance margins will vary greatly when installed. The ITT and speed margins will have changed. Because of the time and effort it takes to prepare the engine, run the test and then de-stage the engine and make it ready for installation with its own equipment, with variable results , the non-certified test run performed after an MPI is a glorified leak check and a huge waste of time, energy and money.

This run provides NO additional value-added benefits to a MPI than the required post-MPI on-wing ground runs. During the post-MPI on-wing ground run, your engines are installed on the aircraft and retain its original inlet nacelle, tailpipe, afterbody, accessories and pylon installation. This is the real world operating environment for the engine where numbers really mean something.

In greater than 98% of the engines that come through our turbine engine shop for MPI, an on-wing ground run provides more than sufficient evidence the engine is operating with satisfactory performance and may be returned to service. If the engine needs an N2 speed change, this can be accomplished on-wing in far less time than it takes to de-stage the engine from the cell, access the engine, make the adjustment, re-stage the engine, run it, remove it from the cell and then begin the installation of all the airframe equipment to reinstall the engine on the aircraft.

TFE731 Performance

We must give credit to Honeywell Engineering for developing the TFE731 and building into it the performance repeatability we see today. The original engine design has come along way. Vast improvements made in diagnostic electronics to perform 5-point runs, vibration surveys, fan balances and everything else the engine needs for return to service are readily available with incredible accuracy. Just about all the hardware in the hot section of these engines has been improved, reinforced, engineered for robustness and performance.

The engine has indeed gotten better over time. Repeatability of performance is no longer an issue for all models of the TFE731 engine and hasn’t been for quite some time.

For engines undergoing a Major Periodic Inspection, the test cell run is about as necessary as a GPS to find your way to work everyday. If you know where you're going, what use is it?

We build engines. We have been for more than 30 years.

We'll stack our post-MPI re-entry rate up to any shop out there.