Alternate Engine Does Not Improve Safety, Reliability or Reduce Risk of Fleet Groundings
Aircraft engines have never been safer and more reliable than they are today. Engines of all stripes have made great strides when it comes to this all-important measure.
In the debate over the alternate engine for the F-35 Joint Strike Fighter, however, there’s an edge when it comes to reliability and safety. And the Pratt & Whitney F135 holds that edge.
An engine’s performance is tied to pedigree. Fighter engines that mature as part of a twin-engine platform end up safer and more reliable than those that are developed solely for a single-engine aircraft.
We know that the F135 engine was borne of the F119 engine that is currently powering the F-22 Raptor twin-engine fighter. In fact, the F135 uses the same core as the F119, which itself has benefited from more than 22 million hours of F100 operational flight time world wide, leading directly to better reliability.
The Pratt & Whitney F100 family of engines powering the F-16 has a much lower U.S. Air Force mishap rate than the competing F110 engines on the same platform (the second engine of the Great Engine War; see previous blog entry). The F100 matured in the twin-engine F-15, while the F110 was developed on just the single-engine F-16. The cumulative mishap rate for the F100 is at least 15 percent less than its F110 competitor. In fact the latest generation F100 engine has a mishap rate of zero.
The reasons for this gap in reliability are two-fold. First, an engine matured in a twin engine application can experience a more robust operating environment based on the different missions accomplished by the different aircraft. Twin engine aircraft can perform more challenging maneuvers with less risk of aircraft loss because of the second engine. Second, the maturity time increases at a greater rate for twin-engine jets because hours and learning are logged at twice the rate.
An engine brought in late in the game for a single-engine aircraft still must go through the same trial-and-error process, but without that crucial backup of a second engine.
An alternate engine actually reduces the rate of maturity of the fleet-wide propulsion system because two different engines reduce the accumulated time for maturing either one.
Furthermore, the idea that an alternate engine would prevent fleet-wide groundings ignores the fact that such groundings due to propulsion issues are virtually unheard of these days.
Advances in safety risk management and mitigation practices have all-but-eliminated the need to ground entire classes of aircraft when issues arise. If an engine issue were to arise, specific bases would likely call for a local safety stand-down to take a corrective action while letting the fleet to continue to fly safely.
Even if fleet-wide grounding were a legitimate concern, an unneeded second engine would not be an effective safeguard. The fact that the alternative engine doubles the number of vendors, parts and procedures makes it mathematically more likely that some portion of the fleet might be grounded due to an adverse incident. This is an issue that was highlighted by Senator Tom Harkin back in 2007. Senator Harkin, a Navy pilot in the 1960s, said: "We had problems all the time . . . and there was a series of supply problems and mix-up problems with parts and everything” (Inside the Air Force, 12/14/07). So the alternate engine actually makes the F-35 less safe and reliable. (*** LOL *** See this about Harkin and neither the F-4 (GE) or the F-8 (PW) had an alternate engine in U.S. Service. You can look up the number of F-8 mishaps vs the number made yourself. --EP )
With all of this, we can now add safety and reliability to the long list of reasons that the alternate engine for the F-35 is a bad idea.
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And now kids, this new collection of words from the boss of PW military jet engines.
A recent editorial on the Joint Strike Fighter program in this magazine, “Still Some Explaining To Do” (Aug. 11/18, p. 74), failed to address some significant details about progress with F-35 development, and with the F135 engine in particular, and on a broader basis reflects a fundamental lack of understanding of, or disregard for, how aerospace technology advances. Delivering dependable, affordable engines is our No. 1 priority at Pratt & Whitney. We take this job very seriously and believe it is our responsibility to make sure that the taxpayers, who are our partners and customers, and those protecting our freedoms are armed with the best engine possible—and with the facts.
Most Aviation Week readers understand the development process inherent in technology advancement and specifically in engine design. At Pratt & Whitney, we work to minimize risk through extensive up-front analysis, aggressive ground testing and meaningful flight test. As expected in high-technology programs, we uncover problems in each of these phases, and some issues cannot be identified and addressed until these phases are completed. The fact is, we have identified a number of issues, resolved risks and implemented cost-saving activities throughout the development process. As we go further into flight test, we expect to learn more about our engine and to incorporate additional improvements as we prepare for initial operational capability.
The F135, for its part, has logged nearly 26,000 ground test hours, more than 8,000 flight test hours and 19,500 overall flight hours to date, and averaged a 98% mission availability rate since receiving initial service release in 2010. That measure of readiness at this stage in the program is significant, especially since the F-35 program is only 60% through development, and fighter engines are considered mature only after attaining more than 200,000 flight hours.
The F135 has also performed exceptionally well within the test environment, including demanding air-start and high-angle-of-attack tests, and 167 short-takeoffs-and-vertical-landings during sea trials. And notwithstanding a 40% reduction in production volume since engine deliveries began in 2009, we still have been able to reduce engine costs by 50%. What is more, we have invested $65 million into the F135 program, which has enabled Pratt & Whitney to deliver every low-rate initial-production contract at or beneath our “War on Cost” targets. We are on track to deliver the much larger and more capable F135 engine for the same cost as the F119 engine powering the F-22.
As we look to the Pentagon’s announced plans for future air dominance platforms, we believe the F135 may provide the foundation for the next generation in military engines technology. That is one reason for maintaining the privilege of keeping our engine cost data private and sharing cost details only with our customer. That should not be surprising to this magazine or to anyone familiar with the aerospace industry. Engine pricing and cost data constitute proprietary, competition-sensitive information, and protecting it is standard industry practice.
Incidents like the June 23 fan-stage breakup at Eglin AFB, Florida, while disappointing, occur while developing state-of-the-art technologies like the F135. We don’t like it when issues arise, but in the process of meeting our customers’ demands and pushing beyond the boundaries of technology, we expect to learn new things. If we did not encounter or discover new things in development or flight test, we would still be operating in the comfortable realm of the known and the status quo. Certainly, more than others, Aviation Week should know that is not what we do in our industry.
As the Aviation Week editorial noted, we have not been able to release many details about the cause of the June 23 incident, pending conclusion of the investigation. At this time, however, we believe we understand what occurred, and we are running rig and engine tests to simulate as nearly as possible the conditions that led to the event. We also have been working on a new design change that we believe will correct the problem. We hope to share further details when that process is completed, and our customers feel confident we have established a root cause and identified a fix. Based on their concurrence, we hope to share those details in the near future.
When you consider all of the facts, it should be clear that on balance, the F135 is living up to its promise as the propulsion system for the F-35.
While we continue to work closely with the military services and our partners to address and resolve this recent incident, there should be no question about Pratt & Whitney’s dedication or commitment to providing our customers with dependable, affordable engines—that has been our mission for nearly a century, and it will always remain that way.
Bennett Croswell is president of Pratt & Whitney Military Engines in East Hartford, Connecticut.
USG accepts PW F-35 engine deliveries again -- root-cause for engine fire still a question mark
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