Australian aircraft fly millions of kilometres each year, so it is imperative that the aircraft and engines are safe and airworthy at all times. One instrument that maintenance engineers regularly use to inspect the inside of aircraft engines, and so ensure optimal performance, is a videoscope.
Remote Visual Inspection (RVI) of materials, components and structures allows engineers and technicians the ability to inspect internal surfaces and other features of an engine, motor or machinery. Videoscopes are used to carry out inspections without causing damage to delicate parts of an aircraft. Olympus – manufacturer of optical, electronic and precision engineering products – says it has been at the forefront of videoscope development for many decades.
A videoscope is an inspection instrument that consists of a small camera mounted on a length of cable. The camera can be controlled remotely by an operator while it is inserted in the cavity to be inspected. Modern videoscopes incorporate powerful LED light sources which are delivered through the tip of the probe, as well as motors to move the lens tip assembly.
According to Sean Fogarty, senior sales specialist at Olympus in Queensland, the greatest advances and improvements for videoscopes during the past two to five years have been in battery and LED technology.
“Batteries are smaller and lighter so videoscopes continue to get smaller,” he said. “The limitations of original videoscopes were getting light into the area being inspected and the size of the power supply.”
An Olympus videoscope is used to see if there are any signs of wear or damage and using a fine tip probe allows maintenance teams to inspect the insides of components and obscured parts of the fuselage for signs of cracking or fatigue.
Aircraft maintenance from the inside
Wayne Thomson, technical manager Asia Pacific with Dallas Airmotive, travels extensively throughout Australia and South-East Asia inspecting aircraft engines to either prepare a quotation for the repair of gas turbines or to approve the airworthiness of a powerplant. Thomson has more than 20 years of experience maintaining and repairing gas turbine engines.
During his professional career, Thomson has worked on engines manufactured by General Electric, Rolls-Royce, Pratt & Whitney and Honeywell.
In the Asia Pacific region, Dallas Airmotive has field service technicians located in Brisbane, Perth, Bangkok and a Regional Turbine Centre in Singapore. The company operates 24 hours every day and its engine services are OEM-authorised which means it can support most of the turbine engine models that power business aircraft today, and many of the engines used in government, military and commercial applications. It also offers comprehensive engine-specific warranties.
Aircraft maintenance technicians usually refer to themselves as A&Ps, which is shorthand for airframe and power plant mechanics. A&P License holders are certified to inspect, perform, or supervise maintenance of aircraft and aircraft systems. A&P mechanics are certified to accomplish their duties on both commercial and private aircraft. Dallas Airmotive delivers unmatched expertise from field service technicians who have an average of 16 years of experience, hold an A&P license and a IA rating.
One of the main tools of the trade is a videoscope, like the Olympus iPlex model used by Thomson. “The Olympus videoscope allows me to see clearly inside the engine which provides a very good idea of the parts required to repair the engine inspected,” he says. “This allows me to give the customer a far more accurate estimate for a repair which, along with researching the engine log books, provides us the information that we need to have all the parts required on-site at the time of the repair. This enables us to complete the repair in a very short time reducing the need for a customer to have a rental engine.
“Compared to other instruments we have used,” Thomson says and adds, “our iPlex videoscope is the best tool out of anything we have purchased so far.”
It is important that airline and businesses have state of the art aircraft to ensure the safety of passengers and staff. A plane might fly for thousands of hours each year, often in adverse weather conditions. There is also a range of landing strips throughout Australasia, from runways at large, well developed international airports to a wide variety of remote and, at times, challenging grass or dirt airstrips. Aircraft also operate in a range of climatic conditions, from baking dry in the deserts to high humidity in the tropics.
All aircraft have a specified maintenance schedule whereby they are regularly inspected and engines serviced after a designated number of flying hours. After a longer period, engines also undergo a major overhaul which involves the engine being removed from the airframe and refurbished.
The basic Time Between Overhaul (TBO) and Hot Section Inspection (HSI) interval is designated in the maintenance manual for a particular engine model. The TBO interval depends on the specified operation of the engine, which the operator may adjust if required, based upon operating experience but must also get the approval from the appropriate airworthiness authority, such as the Civil Aviation Safety Authority (CASA) in Australia.
Typical engine maintenance actions include, engine washing, compressor and turbine desalination, Foreign Object Damage (FOD) and corrosion inspection of the compressor and inlet case, fuel nozzle inspection and borescope inspection of combustion chamber, compressor turbine and more. Engines operating in sandy or dusty environments, or in smog or salt-laden atmospheres, should be subjected to additional inspections for corrosion and compressor erosion.
“It is far easier and more cost effective to insert a videoscope into an engine to inspect the hot areas compared to that of disassembling a whole engine,” Thomson says.
For an aircraft operator, it is important to minimise the time when an aircraft is not able to fly. Thomson regularly suggests that certain inspections be coordinated with other maintenance procedures. One engine Thomson frequently works with is the Pratt & Whitney PT6A, which is a lightweight free turbine engine incorporating a reverse flow combustion path. It utilises two counter-rotating turbines: one driving the compressor and the other driving the propeller through a reduction gearbox. The latter turbine is ‘free’ or independent of the compressor turbine. The design of the PT6A engine allows it to be split into two major parts called the power section assembly and the gas generator assembly.
“For example, a PT6A Series engine may require the removal and cleaning of the fuel nozzles every 400 flying hours,” says Thomson. “Coordinating this with a boroscope inspection allows me to use the fuel nozzle openings to look at the hot sections of the engine where most deterioration occurs.” The results can be quickly checked against the maintenance manual criteria to determine the serviceability of the engine.
“The latest videoscopes are lightweight and can be used on the flightline,” Thomson says. “The monitor can be placed in the engine bay and I can use the pistol grip to control the camera to inspect the core of the engine.” The camera and cable of a videoscope connect to a monitor where images can be viewed in real time. Data can also be recorded and reviewed for faults which may have been initially missed.
The large, daylight viewing screen of the latest iPlex range also allows them to be used as a training tool. An inspector can be watching the screen at the same time as a trainee maintenance engineer and explain what is being shown.
A less obvious advantage of the smaller size of the iPlex videoscopes is that they are easier to transport between international jobs. “We used to travel with a large borescope case which was checked in and now it is carry-on baggage,” Thomson says. “This also allows for ease of travel at airports not waiting for checked baggage and smoother transitions through customs.”
The cost of videoscopes has also decreased and they are becoming more affordable for more and more markets. There is now potential for other aircraft maintenance companies in the country to benefit from having the ability to see inside the engines and airframes they work on.