Challenges to Engine Manufacturers


By: Mark H Goodrich

Changes within corporate structures and governmental agencies present aircraft engine manufacturers with a moment of sea change. Enormous opportunities exist, but are coupled with equally large risks not only to individual manufacturers, but also to the industry writ large, including airframe and component manufacturers, airlines, and myriad collateral businesses. Balancing opportunity and risk poses challenges for engine manufacturers that could well determine not merely market share and profitability, but survival of engine manufacturing subsidiaries within the larger enterprises that represent today’s industrial makeup.

This article considers two fundamental challenges. Both are, at their root, a function of consolidation within the industry, but one is internal and the other external to the engine manufacturing business. Nonetheless, both are emerging challenges that manufacturers will, in one way or another, be forced to address.

To lay the groundwork for these challenges, some history is relevant. Over the past four decades, the most significant aspect of improved airplane performance, payload capacity, range, fuel specifics, noise and dependability has been engine technology. It has been some fifty years since jet engines entered airline service, forty since the original turbofan engines first allowed a quantum leap to carry large payloads at fuel-efficient altitudes, and twenty since improved turbofans coupled higher power-to-weight ratios with dependability that allowed for wide-spread approval of extended-range twin-engine operations.

Performance with early jets and turbofans was marginal, and both industry and regulators often “winked” at the minimum performance standards in order to certify both airframes and engines. From the design and test perspective, there were often substantial differences between the letter of substantive federal regulations and the interpretive guidance of the regulating agency by which certification was actually measured. The result was products that were incapable of meeting the minimums ostensibly required by the legally controlling standards. Those early engines could also be temperamental, as manufacturers struggled to understand and cope with metallurgical issues, air flows and fuel-air mixtures across the panoply of temperatures, pressures and thrust lever movements. The next generation of turbofans was substantially more powerful, but brought into sharp relief how performance and reliability could be affected by changes in design.

Those issues were not isolated from changes in the industry, but a result of them. Merger and acquisition concentrated the industry generally, including engine manufacturers. Larger corporate structures required additional layers of middle management, and increasingly isolated executive management from product development. At the same time, the makeup of senior management was changing. Fewer people in the executive offices were a product of a life-long career path through the company ranks, and brought less understanding of technical and production issues to their work, instead depending upon executive summaries and reports from their subsidiary managers.

Differences in facility locations and record-keeping systems often resulted in documents that no longer seemed relevant being discarded with older machinery and tooling. The efficiency experts that made those decisions often saw the world refracted through a prism of limited technical knowledge, and did not understand how often past lessons forgotten rise again and again over time in the manufacture of technically sophisticated products.

At the same time, more power, better fuel specifics, reduced emissions and less noise were being demanded by airlines, regulators, lessors, and airframe manufacturers. New materials and technologies were being introduced, accompanied by economic pressures to accelerate their incorporation into products. More complicated technologies and new materials, coupled with dated expertise and limited resources at the certification and oversight regulators, meant government was ever less able to knowledgeably validate design and manufacturing, and instead compelled to delegate more of those functions to the manufacturers.

To place in perspective the potential affects of design changes, consider hydrogen embrittlement. Industry confronted this issue some four decades ago, but its absence as a concern during the intervening time, along with the loss of institutional memory through corporate consolidation, recently made it once again an issue of apparent first impression.

Consider also how volcanic ash was presumed to be only a modest threat after flight testing fifty years ago with early model axial-flow turbojets. Two decades later, failures during ash encounters raised the specter that damage from volcanic ash was no longer limited to “polishing” low-pressure compressor blades. The difference was temperature. Engines used for earlier flight testing operated hundreds of degrees cooler than later turbofans, and the higher temperatures were sufficient to melt ash into engine-clogging glass.


A third example concerns the potential for engine icing at cruise altitudes. Based on designs of the early 1960s, it was determined that, absent vertical updrafts from thunderstorms below, engine icing would not occur at ambient temperatures below minus forty degrees Centigrade. But changes in the design of compressor blades, stators and air flow path control, coupled with higher engine operating temperatures, later resulted in a potential for ice buildups at even much colder temperatures.


Today, composite, ceramic and alloyed metal materials are presenting new engineering challenges, and the resulting affects from their incorporation must be comprehensively considered in the design process. Dimensional requirements and a de minimis requirement for fasteners make composites even more attractive for engine designs than for those of airframes. Ceramics likewise offer significant advantages for use in engines, where larger coefficients of thermal expansion and contraction exist when using metals. And, new aluminum and steel alloys offer the potential for a variety of desirable characteristics, including higher strength, lower weight and reduced intergranular corrosion in high-temperature environments.

The common denominator is a challenge to ensure that engineering is not unduly affected by the inherent pressures within a large corporate enterprise to minimize expense and time in design and certification, including too much reliance on computer projections and too little consideration of lessons previously learned. It is all-too easy for such pressures to result in addressing only minimum standards of the regulating authority, or lowering established company standards. History instructs that margins are the key to safety and maintainability in aircraft and engine design, and minimum regulatory standards are never valid design targets. They are minimums, and often remain unchanged for decades while the state-of-the-art advances. At best they represent good engineering practices at an earlier time when the standard was first proposed. With respect to new technologies, regulations often contain no standards, and recognized industry standards likewise have not yet been established by professional engineering or materials organizations. A new material or technology may indeed seem like a miracle, but any presumption to that effect before thorough analysis and testing is just theory. When Albert Einstein was asked why he always referred to his work on general relativity as a theory, he replied, “In theory, theory and practice are always the same, but in practice, theory and practice are never the same.”

It is thus the manufacturer that is challenged to think beyond minimum regulatory standards, and consider the panoply of potential affects due to changes in design technologies and materials. The regulator is required only to obtain documentation validating that minimum standards have been met. It is the responsibility of the manufacturer to ensure that all reasonable steps have been taken to design and build an engine that will reliably perform in service, and be maintainable over time. It is critical to remember that performance – not reliability or maintainability – is the principal driver in certification, but reliability and maintainability are just as important in operation. Passengers rely upon engine integrity, as do airframe manufacturers and operators. The world-wide industry now relies upon twin engine airplanes for long-range operations, and any absence of dependability – actual or perceived – has the potential to send economic ripples across the industry like waves on a pond.

Politically, the time is right for an expansion of the authority delegated to manufacturers for the internal oversight of their own product development and manufacture. The ability to use such delegated authority is a significant advantage, but easily abused. A single high-profile event can result in loss of delegated authority, costing efficiency, time and money over years, if not decades. Many forces within a large corporate enterprise push for a fast schedule, and the quick incorporation of new materials and technologies. The Board wants better share performance every quarter, executives want bigger bonuses by December, and middle managers want to hear only good news from their subordinates. Marketing often wants to begin incorporating performance, weight and pricing into sales agreements before engineering has established a baseline for any of those factors. But, first to market is of no advantage when a product fails to meet expectations or contractual guarantees. Expenses required to properly design and thoroughly test are high, but pale when compared to the quantification of expense for a fleet-wide grounding, an airworthiness directive, and loss of perceived company integrity in the industry. The challenge for manufacturers is to ensure that engineering is given the tools and time to test new materials and technologies without allowing the imposition of corporate pressures that short-cut proper engineering and testing standards.

A second major challenge also arises frequently from corporate consolidation factors, but in this instance within the user community – that is, with lessors and airlines. Substantially all customer service operations of engine manufacturers report failures by their lessor and airline customers to comply with operating recommendations and requirements of the manufacturer as a major recurring issue. The challenge is to ensure engines are operated and maintained in conformance with those procedures.

Nearly half of the airline aircraft in the world are owned by leasing companies, most of which see themselves as banks, rather than as owners and operators of aircraft. The interaction between lessor and lessee is often highlighted by gamesmanship over which will be responsible for what maintenance and inspection events, with work accomplished by a hodgepodge of facilities that rarely have operations specifications for engine types. Leased aircraft are seldom treated as owned aircraft, and maintenance that is recommended, but not required, is often rationalized as unnecessary expense. The casualty to this situation is often engine integrity, higher costs for scheduled maintenance and overhauls, and reduced engine life on the wing.

Merger and acquisition have also affected airlines. Bridging maintenance programs can be prohibitively expensive, and two or three separate airlines sometimes operate under one logo for years. Support personnel of engine manufacturers frequently find that airlines have not faithfully incorporated operations, maintenance and inspection details into airline manuals. Even when such details are incorporated, airline personnel often continue to operate and maintain engines as they did prior models, and claims for warranty often reveal failures to maintain and operate as required or recommended by the manufacturer.

Most lessors and airlines rely upon third-party maintenance organizations, and MROs often find themselves in the middle, as regulators require contracted maintenance for an airline be performed in conformance with the airline maintenance and inspection program – often at odds with recommendations of the manufacturer. The MRO finds itself caught between legality and proper procedure.

The solution to this challenge is not as simple as just denying bad warranty claims. Engine problems in service can shed bad light on the manufacturer even when the causes are local to an airline operation, and doing battle with customers invariably sours relationships. Hourly-based maintenance programs have been a positive step towards ensuring the ongoing involvement of the manufacturer with its engines, but are still far from universally elected by users. Manufacturers could, as part of the contracts for sale, require access to down-linked data and involvement in overseeing engine maintenance generally. They might also seek to lease in lieu of sale, including contract terms allowing them to monitor engine data through down-link, conduct recurrent inspections on-site, and perform all major maintenance.

There is always resistance to change, but the increased sophistication of aircraft engines coupled with new technologies, new materials, increased responsibilities of manufacturers in the certification of their products, and corresponding changes in how airlines and lessors operate and maintain their fleets, all combine to present challenges that call for an equally new and creative business model for engine manufacturers.

  Copyright 2014 MRO Network Publications

“Challenges for Engine Manufacturers” was first published by the MRO Network in London in its “Engine Handbook: 2015”.