Wednesday, January 27, 2010

F35 Test Pilot: The F135 has lived up to our lofty expectations

Pratt & Whitney’s F135 propulsion system recently powered the Lockheed Martin F-35B Lightning II short takeoff/vertical landing (STOVL) fighter through the first in-flight engagement of its STOVL propulsion system. In the cockpit, at the controls during this historic flight was Graham Tomlinson, F-35 Lead STOVL Pilot and an employee of BAE Systems. Graham shared his thoughts on the significance of this major milestone, the performance of the aircraft and the performance of the Pratt & Whitney F135 engine.

1. As part of the first F-35B in-flight STOVL engagement, what specific criteria were you evaluating?

Graham Tomlinson: In the cockpit the task is to make sure that the “throttle and stick” responses are as predicted through these first conversions and our first experience of flight in STOVL mode. This really means comparing the responses to the training we’ve done in the simulators. All the responses did match extremely well – pitch, roll, yaw, and thrust - so it was a very easy and satisfying task for me. And the things the simulator can’t reproduce – noises, vibrations etc – were pleasantly subdued in the real thing.

But the key criteria were engineering responses, checked and analyzed on telemetry by the control room team. The pilot only gets a general impression; the engineers can check the detail. We were especially interested in the propulsion system response through the conversions, spooling up the liftfan and radically changing the thrust center of the engine and liftfan combo. We’ve done this static on the ground but never before with the aerodynamic effects of 200 knots (on the doors, on the intake flows, on the liftfan exhaust etc).

And after conversion in STOVL mode this again was our first flight opportunity to check the total thrust response and the balance of thrust from liftfan and core engine which are now not just thrust, but primary aircraft controls. These key parameters, plus the roll bleed posts off the core engine, are absolutely critical to STOVL flight control. The engineers were very pleased with the results.

2. Were there any surprises during the 14-minute STOVL segment of the test flight, not just in aircraft/engine performance, but also how it felt?

Graham Tomlinson: I hadn’t realized some of the limitations of motion simulators. When we make small acceleration requests the simulator gives a modest kick-in-the-pants. In flight, the kick-in-the-pants feels stronger (which all pilots will love!).

The other expected effect, but still nice to confirm in flight, was the smoothness of the ride. The liftfan is right behind your back, and you can hear/feel it humming away, but both the noise levels and the vibration levels were just fine. It’ll undoubtedly get louder as we slow down to the hover, but I was very pleased with the subdued levels at the speeds we’ve tested so far.

3. How would you characterize the performance of the Pratt & Whitney F135 engine and how does its performance differ from other fighter aircraft engines?

Graham Tomlinson: So far in the JSF test program the F135 has lived up to our lofty expectations; it has been there when we want it, and has been no trouble at all. That’s a remarkable achievement for an engine which has to reconfigure from a 40K pound thrust category in Max AB conventional mode, to a 40K pound thrust category with the liftfan spinning in STOVL mode. For me the best thing has been that we simply haven’t had to worry about it!

4. What was going through your mind when you engaged that clutch for the first time?

Graham Tomlinson: The flight test team is super-professional. We’re all thoroughly practiced and trained; we can do the job in our sleep. And that means that for this first button press there was zero stress, we were just going the through a routine test we’d seen a hundred times before. And that’s a good thing too, as pilots’ brains are well known to shrivel to the size of a pea in flight!

5. What is the best part of your job as the F-35 test pilot?

Graham Tomlinson: Being part of the team, bringing back the results and the data we need, and the satisfying feeling when the team makes progress. We’ve just made a huge step forward.

Monday, January 18, 2010

New Year, New Milestones, Same Great Engine

By now, most of you will have viewed the video posted here and elsewhere on the Web showing the first in-flight F-35 engagement of the Short Take Off Vertical Landing (STOVL) Lift Fan propulsion system. Days later, I still get goose bumps watching the F-35 Lightning II, powered by the Pratt & Whitney F135 engine, successfully achieve such a crucial milestone. And while that video engenders excitement and gratification throughout the Pratt & Whitney family as well as among our teammates, it also reminds us that there are numerous milestones ahead as the F135 continues to power Lockheed Martin’s F-35 flight test program while the engine also advances toward full production.

First, however, let’s remember how far we’ve come. Roughly a decade ago, Pratt & Whitney evolved the proven F119 engine (the exclusive propulsion system for the F-22 Raptor) to power both Joint Strike Fighter finalists. Following Lockheed Martin’s selection as the winning prime contractor, Pratt & Whitney began testing and manufacturing 18 flight test engines, the last of which will be delivered shortly. More than 126 test flights and 13,000 test hours later, the F135 remains the only engine to power an F-35, an accomplishment that will continue for quite some time to come.

In the world of jet engine test, there is a metric that is used to determine how the engine is progressing through System, Development and Demonstration. The metric is referred to as risk retirement. As the risk in the program is retired, the engine progresses in maturity. It’s worth noting that 90 percent of the F135’s program risk has now been retired through testing and other verifiable processes. And that number will be even higher by year-end. The most visible benefit of this engineering rigor is that despite the occasional challenge inherent with such a sophisticated propulsion system, the F135 has never caused a flight test delay or in-flight incident.

Pratt & Whitney will deliver its very first production F135 in the coming weeks. Also expected in the near future, and arguably most noteworthy is achievement of Initial Service Release for the Conventional Take Off and Landing/Carrier Variant (CTOL/CV) F135 engine, a key U.S. government endorsement that will mean the F135 meets all safety, reliability and performance requirements for operational use in the field. Simply put, the F135 is about to become the most advanced fighter engine ever certified for the defense of America’s freedom. Stand by for even more goose bumps.

-- Eagleblogger

Friday, January 8, 2010

Onward and Upward – Literally

Now that the holiday season is behind us, EagleBlogger is back from hiatus. However, that doesn’t mean the Pratt & Whitney F135 engine program has taken a break, far from it.

In fact, just in time for the holiday season, Pratt & Whitney has delivered its final Conventional Take Off and Landing/Carrier Variant (CTOL/CV) F135 flight test engine to the U.S. Air Force. This marks yet another important milestone in the transition from System Design and Demonstration to full production for the F135 engine. Pratt & Whitney has delivered 17 F135 flight test engines and expects handing over of the final Short Take Off Vertical Landing (STOVL) test engine early this year, for a total delivery of 18 flight test engines – still the only propulsion system powering the F-35 Lightning II flight test program.

And as another illustration of this transition from SDD to production, Pratt & Whitney finished assembly and test last month of the first F135 engine production line at their facility in Middletown, Connecticut.

Best practices gleaned from the F-22 Raptor’s F119 engine production line were refined further in the design of the F135 production line. Despite Pratt & Whitney’s undisputed status as the world’s only manufacturer of fifth generation propulsion systems, it invested more than a year planning the first F135 line, leveraging tools from the company’s Achieving Competitive Excellence operating system to maximize integration, efficiency and safety in the years to come. This assembly line will redefine “world class” once operational, powering not just an aircraft, but also the defense of this nation and numerous allies for decades to come.

Meanwhile, the F135 has logged more than 13,000 test hours, powered a non-stop ferry flight from Ft. Worth to the Patuxent River, Maryland flight test location, and just yesterday powered the F-35 through its first in-flight engagement of the STOVL Lift Fan propulsion system.

-- Eagleblogger