(L/D)max Aviation Group

When it comes to the investigation of engine features in aviation accidents, the ever-changing technology has made the process complicated. With newer, more technologically practical small gas turbine engines being used in both business aircraft and helicopters, similar large gas turbine engines being used in commercial aviation and special uses of both large and small engines in military applications, it has become more urgent for investigators to expand their knowledge to fully understand the impact of design characteristics and failure modes of these state-of-the-art engines.

(L/D)max Aviation Safety Group designed the various GTI courses to educate and train investigators that work frequently with gas turbine engines installed in aircraft. To do so, the GTI courses provide attendees with the knowledge and training needed to take an active role in the detailed investigation of a gas turbine accident and to make applicable field determinations. In an effort to reach these goals, these courses have been designed to deliver a variety of benefits to attendees. Those benefits are outlined below.

In addition to the many benefits associated with the GTI courses offered by (L/D)max Aviation, it is important to point out that these courses also place great emphasis on the important nature of gathering evidence accurately and efficiently so that precise reporting of that evidence can be developed. In doing so, it becomes easier for the investigator to draw accurate conclusions while putting together a final report. Understanding the relationship between the engine and the remainder of the aircraft, and its operations, is a critical piece of knowledge that investigators are sure to gain in this course as well. These courses offer the opportunity to observe actual evidence, evaluate summaries of studies that have been done over the years, and look into details of work accomplished by industry-wide committees.

While it can be said that all gas turbine engines operate the same, there is a significant difference between smaller engines (turbofan, turbopropeller and turbo shaft) used in regional, business and rotary wing aircraft and their larger cousins, the large high by-pass fan engines used in large transports. In addition, both large and small engines have been adapted (or evolved from) military gas turbines which operate in shorter cycles and higher demand missions. For this reason, (L/D)max Aviation has developed three courses that specialize in investigating the commonalities as well as the differences.

Completion of the GTI courses provides individuals with the necessary skills and knowledge to effectively investigate a gas turbine accident, write a detailed and accurate report, and make vital field recommendations when applicable.

Generalist aircraft accident investigators along with engine specialists will benefit from one or more of the following Gas Turbine Investigation courses.

• Large Gas Turbine Investigation (LGTI): Individuals most likely to participate in the accident investigations involving gas turbine powered aircrafts in commercial aviation.
• Small Gas Turbine Investigation (SGTI): Individuals most likely to participate in the accident investigations involving small turbine powered aircraft and helicopters.
• Military Gas Turbine Investigation (MGTI): Individuals most likely to participate in military accident investigations involving gas turbine engines.

As mentioned, there are unique design characteristics and failure modes that need to be accounted for in gas turbine accident investigation. But, beyond understanding these aspects of gas turbines, there are a variety of things to be learned in the GTI courses. The following is a detailed list of the various benefits students will receive in attending and completing any or all of these courses:

• Increased knowledge of the unique features, failure modes and investigation techniques for the newest gas turbine engines being employed in the aviation industry
• Receive education on general terminology used in these investigations
• Gain unique knowledge of the layout and functions of the internal workings of a jet engine
• Education of the basic modules associated with a jet engine and how these play a part as either causes or in ground impact damage
• Understanding of the most primary causes of engine-related accidents and/or incidents, as well as how these affect or are affected by the aircraft itself and the flight crew involved
• Evaluating realistic examples of such accidents and current case studies provides investigators with the skills to better apply theoretical knowledge in a useful way to the accident investigation
• Development of the ability to identify post-crash evidence of some of the most serious engine-related aviation accidents. In addition, students will gain the knowledge necessary in distinguishing those that are also known as "benign" engine failures
• Identification of the role crew error plays in such accidents
• For those professionals who must satisfy continuing education requirements (professional engineers, medical personnel, etc.) (L/D)max Aviation awards each attendee that completes this course successfully with the award of 3.6 CEU's
• The Board of Certified Safety professionals recognizes these GTI courses for Continuation of Certification Credit

In addition to the general benefits outlined above, each course specializes its approach to the investigation.

Large Gas Turbine Investigation (LGTI)

The Large Gas Turbine Investigation course addresses the investigation of the modern large diameter high by-pass turbofan engines commonly found on major transport aircraft. Design, certification and failure modes have changed the need for three and four engines to long range extended twin-engine overwater operations. Some of the basic components of the Large Gas Turbine Investigation course are:

• Design of the engine
• Types of installations
• Multi-Rotor configurations
• Large fan engines windmilling issues
• Large non-failed fan engines may producing significant gyro forces in an aircraft upset
• Speed and Angle of Impact
• Engine Power Determination
• Failure mechanisms
• Radial Deformation and Axial Impacts
• Mechanical and Thermal Non-Containment
• Bird Ingestion/Foreign Object Damage
• Engine Surge/Compressor Stall
• Large engines with cowl-load-sharing producing significant seizure damage to nacelles, and pylons
• Blade Failures and Containment
• Disk Failures
• Bearing Failure
• Cooling Air Failure
• Internal and External Fire

Small Gas Turbine Investigation (SGTI)

The Small Gas Turbine Investigation course focuses on the small diameter gas turbines in two categories:

• Gas turbines most commonly found in those engines identified with shaft horsepower to drive propellers and rotors
• Small diameter by-pass fan engines most commonly used in general aviation, regional jets, business aviation and very light jets

While gas turbine principles remain the same as for the Large Gas Turbine Investigation course, these engines exhibit significant differences from their larger cousins in failure modes, power transmission and in evidence in a post-crash environment. Some of the issues and topics to be discussed in the SGTI course include:

• Turbo-propeller efficiency
• Core-Lock
• Rotor/Transmission power transfer
• Short cycle, high demand operations
• Single or dual engine applications
• Power developed between from 500 to 2,000 SHP
• Hydromechanical control systems unlike the Large and military engines which have FADEC systems
• Turbofan engines and turboprop engines for regional applications have much more sophisticated diagnostic capabilities that can be used to determine engine health status with relative ease without relying on physical contact signatures alone

Military Gas Turbine Investigation (MGTI)

Military aircraft, both fixed-wing and rotary-wing have a wide range of uses and demands of the gas turbine engine. Large military transport aircraft may have similar cycles and loads as commercial transports, but have several operating environment and maintenance issues not associated with the commercial world. Military-unique gas turbine engines make use of specialized capabilities, wide speed ranges, afterburning, and rapid changing of engine conditions in the operational environment, just to name a few. Some of the key topics:

• Understanding of mission cycle and how it affects a Gas Turbine Engine design and manufacture
• Non-combat differences in system usages i.e,. Low altitude effects on engine durability, high speed, high altitude effects, edge of envelope operations, fuel and oil limitations
• Modular versus non-modular construction
• High pressure ratios for high performance
• Airframe engine interfaces
• Anti / De - Icing systems
• On board Jet fuel starting systems
• Afterburner operations - No lights, blowouts, stalls - what are causes of each
• Types of Afterburner control / actuation systems  Hydraulic, Pneumatic etc.
• Stalls resulting in stagnations - causes and preventions
• Temperature relations during stalls
• Oil analysis programs
• Alternate fuels and their relation to operation

(L/D)max Aviation has designed each of these courses for completion in 4.5 days. Beyond lecture outlines and notes, students will have access to use of a textbook as well as pertinent reference materials. Attendees will also receive a certificate of completion upon finishing all 36 hours of classroom instruction training for each of these courses.