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  • The Great Engine Misinformation War
    Posted by Graham Warwick 3:23 PM on Jun 01, 2010

    Amid votes and veto threats, the battle over the second engine for the Joint Strike Fighter looks set to continue for a few more months and could spill over into next year and the Fiscal 2012 defense budget. As more politicians get drawn into the debate, each side is accusing the other of spreading misinformation about their engine's cost, performance and even right to exist.

    I thought I would take a shot at cutting through some of the misinformation to lay out the arguments for and against competitive engine procurement as clearly as I can see them.


    Pratt & Whitney signed a $4.8 billion contract in September 2001 to develop the F135. Today the Pentagon's estimate of the cost to complete development is $7.3 billion. GE says it will cost $4 billion to develop the F136; the Pentagon estimates it will cost a total of $5.9 billion to get the engine into competitive procurement. Those are the numbers being bandied around, but where do they come from?

    There have been two major cost increases on F135 development. The first came in 2004, when Lockheed had to redesign the F-35 to reduce the weight of the STOVL variant to meet requirements. The F135 was redesigned to increase thrust and reduce weight, pushing the development cost up to $5.9 billion. Then, in 2008, Pratt had to redesign the third-stage turbine, and Rolls the lift fan, which resulted in a $800 million overspend, taking development cost to the $6.7 billion currently under contract.

    The remaining $600 million is a Pentagon planning number, an estimate of the additional cost involved in supporting the 13-month extension of F-35 development under the restructured program. The extra work content has not been specified or negotiated yet, but will not involve changes to the engine, according to Pratt.

    The $6.7 billion under contract covers development of the F135; the common hardware, including augmentor duct and exhaust nozzle, for both the F135 and F136; and the lift system, for use with both engines. Of the total, $1.6 billion has gone to Rolls-Royce to develop the lift system for the STOVL F-35. Lift-system integration is included in Pratt's $5.1 billion, and the integrated propulsion and flight control software logic will be provided to GE/Rolls for the F136.

    GE/Rolls, meanwhile, has received $3 billion since 1996 for the F136 and says another $1 billion is needed to complete development. If the cost of tooling and other production preparations are included, this becomes $1.8 billion - $1.1 billion below the Pentagon's estimate of the cost to get to competitive procurement. GE/Rolls says the difference is mainly in the Pentagon's assumption that F135 prices will increase because of loss of learning as Pratt builds fewer engines.

    GE/Rolls maintains fixed-price contracts for early production engines will eliminate that loss of learning. The Pentagon says its estimates already assume GE/Rolls will be able to match Pratt's prices even though the F136 program is running five years behind the F135. That assumption is based on "a very accelerated learning curve" that will be "extremely difficult to achieve", argues the Pentagon.

    Pratt says it has a plan agreed with the Pentagon to meet the price target - for an F135 to cost the same as an F119 despite being bigger and heavier - by the 250th engine. The company argues GE/Rolls will have to beat that "very aggressive" price goal by $1-2 million to offset the $2.9 billion and make the business case for a second engine break even. GE/Rolls says its fixed-price offer will take the business case from break-even to positive. 

    Verdict: Factor out the STOVL-related impacts that GE/Rolls avoided by being later, and the two engines will cost about the same to develop. It's down to GE/Rolls to prove they can beat Pratt's production prices.


    GE/Rolls says there wasn't a competition to power the F-35; P&W says there was. The truth, now acknowledged by the Pentagon, is there was never a government-sponsored competition to power Lockheed's F-35. But history shows engine competitions are an exception, and not an entitlement. 

    To recap what you already know about engine "competitions", here's how the last few US fighter programs have gone:

    F-14 and F-15 - P&W was selected competitively in 1970 to develop the F100 for the F-15 and F401 for the F-14. The Navy cancelled the F401 after unsatisfactory flight testing, but a decade later re-engined the F-14 with GE's F110 - without a competition.

    F-16 and F-18 - the single-engined YF-16 was designed around the F-15's F100 engine; the twin-engined YF-17 around GE's YJ101. All F-16A/Bs and the first block of C/Ds were powered by F100s. A second engine was developed for the F-16 because of problems with the F100, and competitive procurement of F100s and F110s began with Block 30/32. GE says 70% of all F-16C/Ds are F110-powered.

    The YF-17, meanwhile, evolved into the F/A-18 and the YJ101 into the F404 - without a competition. The Hornet was later scaled up to the F/A-18E/F, and its engine to the F414. In the late 1980s, P&W was qualified as a second source of the F404, but the Navy cancelled competitive procurement saying it wasn't justified by the planned quantities.

    F-22 - GE and P&W developed and flew competing engines - the YF120 and YF119, respectively - on both the YF-22 and YF-23 during the Advanced Tactical Fighter fly-off. Both aircraft teams offered both engines - the US Air Force picked the F-22 and F119.

    F-35 - Several engines were studied in the initial phases of what became the Joint Strike Fighter program, but when it came to building concept demonstrator aircraft the teams were directed to use the only suitable engine available - Pratt's F119. While this led to both Boeing and Lockheed Martin proposing JSF designs powered by F119 derivatives, the Pentagon planned for competitive engine procurement from the outset and funded work on the F136 in parallel with development of the F-35 and F135.

    The plan was to complete development of the F-35 with the F135 as its powerplant, as the F-16 had with the F100, then introduce competition. That changed in 2006, when the Pentagon decided it could no longer afford a second engine. Congress kept the F136 alive by adding money each year, but only 80% of what was required, forcing GE/Rolls to focus resources on the CTOL engine to stay on track to fly in the F-35 in 2011.

    Verdict: There wasn't a competition, but there was a strategy. Changing that strategy put the Pentagon on ground that is difficult to defend.


    This would be a good argument were it not for the fact that 100% of the US Air Force's combat-coded F-16C/Ds are powered by GE's F110, and 100% of the USAF's F-15s are powered by P&W's F100 - despite the availability of competing engines. All US Navy and Marine Corps F/A-18A/B/C/Ds are powered by GE's F404 and all F/A-18E/Fs by GE's F414. Having two engine types reduces the risk that a problem will ground the entire fleet, but operators have not seen it as essential.

    The Marines have said they want only one engine across their STOVL F-35B fleet, and the Navy has said it does not want to support two engine types on any one aircraft carrier. So when it comes the reduced operational risk of a mixed fleet, only the US Air Force looks likely to benefit - but it is the biggest customer, with plans to buy 1,763 CTOL F-35As (55% of the 9 partner nations' planned total).

    But the JSF program started out with a dual-engine strategy because nine partner nations planned to neck down from nine aircraft types to just one, and a second engine mitigated risk. A single engine, therefore, increases risk.

    Verdict: It's hard to argue with a customer who no longer wants competition when the operators have historically not made engine diversity a priority.


    GE/Rolls hints darkly there will be more cost growth to come before development of Pratt's F135 is complete, but is not specific on why or how it will have to be "modified or redesigned". Pratt points out the CTOL F135 has completed development and is in production and the STOVL engine will follow by year-end.

    The truth is both engines will undergo further development through their lives. GE/Rolls' unelaborated claims against the F135 are based on its belief the F136 has greater potential for growth. Designed later, the F136 has a larger core than the F135. The F136 pumps more air, while the F135 runs hotter, but for now they produce the same thrust because that is set by the area of the exhaust nozzle, which is common to both engines (and is developed by Pratt).

    If a need for more thrust emerges with later blocks of F-35, GE/Rolls will be able to take advantage of F136's larger core and greater airflow (up to the +10% limit of the F-35's inlets). Pratt will have to run the F135's smaller core at higher temperatures. The argument against running hotter is it shortens engine component life; the argument against a larger core pumping more air is it makes the engine (and aircraft) heavier.

    Pratt will run a demonstrator engine this year that will produce 5% more thrust from significantly increased turbine temperatures. This engine is being built under the VAATE research initiative, and not the F-35 program, but the components developed will be retrofittable to the F135. Meanwhile interchangeability, a key JSF requirement, could become an issue with growth engines, as a hotter F135 competes with a heavier F136. Additionally, extra thrust will not help the STOVL F-35B unless the lift fan is also uprated - not considered an easy task.

    Verdict: Irrelevant - but only for as long as commonality and interchangeability remove performance from the competitive equation.


    Marshalling the facts to make the case for this is tougher than it seems, because fighter engines do not exist in isolation. It is true that, when F-15, F-16 and F/A-18E/F production ends, Pratt's F135 would remain the sole US fighter engine in production. But GE and Rolls would still have their commercial engine businesses, which increasingly provide the technology base for military engines.

    GE and Rolls, but not Pratt, are working to demonstrate adaptive engines for future military aircraft under the US Air Force-led ADVENT research program. Rolls will ground-test a complete engine in 2013; GE will demonstrate an adaptive fan and advanced core. The follow-on AD-HEETE program will combine the ADVENT low-pressure system with a high-performance core using commercial engine technology.

    Meanwhile, both GE and Pratt use essentially the same supplier base for 85% of their engines, so the industrial-base issue is not production jobs but combat-engine design skills. With only a small role on ADVENT, Pratt could be leapfrogged by GE and/or Rolls when it comes to powering the next-generation bomber or sixth-generation combat aircraft (manned and/or unmanned). But GE/Rolls could face a long wait for those promised new programs.

    Verdict: The competitive issue is maintaining design skills in prime contractors, not sustaining production jobs in congressional districts.

    Tags: ar99, F-35, JSF, F135, F136

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