Interview: Tom Burbage [F-35 Bits] 15 July 2011

Interview: Tom Burbage Executive Vice President and General Manager, F-35 Program Integration, Lockheed Martin Aeronautics | Written by: Chuck Oldham (Editor) on July 15, 2011

http://www.defensemedianetwork.com/stor ... m-burbage/

[F-35 BITS]
"...You have an MBA, a master’s in aeronautical science, and at Annapolis, you got a bachelor’s in aeronautical engineering. Between that and your service experience, do you think it gives you a different perspective on building aircraft for naval aviation?

I do. You know, I always wanted to fly. My father was a naval aviator and all the role models I had as a kid growing up were Navy pilots. My brother-in-law and son-in-law are Navy aviators. I always wanted to fly and that’s why I was an aeronautical engineer – really to just learn as much as I could about the science of flight. And then the test pilot school at Pax River [Md.] is really what I would consider the graduation course. It is a graduate school to a much higher degree than any MBA or master’s course at any university. It’s very high-level academic experience for a half-day and then you go out and you fly what you’ve learned in the classroom the other half of the day. It is truly an applied education. My experience there and my three years as a project pilot testing a variety of airplanes has given me a really good perspective that a lot of people don’t have. I read every pilot report every day on F-35 because that is where the real issues are. I feel like I can talk to pilots as well as engineers because of my background.

Obviously, you have overall leadership of the F-35 program, but I wanted to ask you about the two naval versions – the B and the C. Originally the F-35B had a much more aggressive testing schedule and now it seems like the F-35C has sort of moved up and accelerated as far as where it is in planning.

Both airplanes, in my opinion, and I may be a little biased, are great flying machines. It’s been a great experience for me to watch the two of them come to life from a series of electronic drawings to now, when both of them are flying. The STOVL [short takeoff/vertical landing] jet is unique in that it has three separate elements to its flight-test program. First, it has to open up the conventional flight envelope: How many gs does it pull? How fast will it go? What are its flying qualities throughout its flight envelope? That’s one set of tasks and that’s common to the Navy jet. The second area is the missions systems: How does the radar work? How do the sensors work? That’s also common to the Navy jet.

The third piece: How do I take this airplane and do short takeoffs and vertical landings? And that’s uncommon to anything else on the face of the Earth except for the Harrier, the airplane it’s replacing.

So, the STOVL jet has a whole other dimension of testing it has to go through. The ground testing is very stressful on the airplane because we basically tie it down to the ground and run it at very high-power settings for long periods of time so we know we’ve got all the forces and moments being exerted properly on the airplane. We don’t want a pilot to get in it for the first time and find out we got that wrong. In the process of doing that, I think we may have induced some early inefficiencies – airplanes don’t like to be tied down at full power – that’s the bottom line. Because of that, we had some early reliability issues in things like door actuators and thermal fans, not the basic STOVL lift system. We’ve replaced most of those parts that were failing and the airplane is flying great right now. Since about the October/November timeframe, the STOVL jet has been the best performer of the three. In 2011, it’s well ahead of its intended test plan.

It has not been error free. You know, we’ve found some things which you find in tests that you didn’t predict. One of the areas of concern is the big door that opens up over the lift fan; it’s like a ’57 Chevy hood, and it spills a lot of air around it, particularly at higher speeds. That spillage was causing a lot of vibration on the two small doors behind it that allow additional air into the main engine in a hover. Because of that, those doors were in a pretty tough environment, and we were actually exciting the natural frequency of the door. Those doors were not lasting near as long as we wanted them to. So, we redesigned the doors, took the natural frequency out of the range that the turbulence was generating, and we have a good fix that’s being implemented right now.

It’s amazing how often you see resonance come up in flight-testing when you read about the histories of different aircraft.

One of the great challenges with a new design is to identify all of the potential flutter modes. We do that very well for the airplane in general but the new design of the F-35B with its unique doors is a new challenge.

The CV airplane has its own unique magic. We’ve designed the flight control system to be very responsive to flying the glide slope, flying the ball, and all the pilots that have flown it have certainly endorsed the fact; we do that through a special technique with the flight control software.

All three variants are common in their up and away flight envelopes as far as the testing goes; they’re common in their mission systems testing. Later on this year in about the October to December timeframe, we’ll go out to the ship and we’ll actually do the first ship quals with the F-35B airplane. Next year we’ll take the Navy airplane, the F-35C, out to the ship and qualify it for catapults and arrested landings.

As I understand it, Harrier pilots who have flown the B say it’s just incomparably easier to fly in the STOVL mode in comparison to the Harrier.

This was a very interesting historical point on this program. In about 2003, there were two schools of thought on mechanizing the flight control systems for the F-35B. One school wanted to do it like a Harrier does. When you’re up and away, it flies like a jet – like an F-16 or an F-18. When you come into the hover, though, your hands change what they do and the airplane flies more like a helicopter. You also get very busy in the hover because you’re moving three levers with two hands: a throttle, stick, and a nozzle position lever.

So, Harrier pilots for good reasons have a special mantra “this airplane’s hard to fly and I can fly it well” sort of mentality. I don’t mean that in a critical way at all. It’s just the simple truth. But, one of the things we were asked to do with this airplane was design an airplane that was not only easier but much safer to fly. If you remember in the early days of the Harrier, there were quite a few accidents that occurred, mainly because the thrust-to-weight ratio on the Harrier was very marginal. Our flight control guys – and I was in the middle of this decision with my chief test pilot, Jon Beesley, were doing some flight control development with the Brits using a specially modified Harrier. We put our flight control system in the back seat and there was a Harrier [flight control system] in the front seat. The challenge was: Can I always control velocity with my left hand and always control altitude with my right hand? If you think about what that means, when you come into the hover and the airplane is sitting there with no forward speed on it and I want to move forward, I push the throttle forward, but I haven’t increased the thrust. I’ve only changed the louvers under the airplane – changed the nozzle position. Now, if I want to go backwards I pull the throttle back and the louvers go the other way and the airplane starts moving backwards. If I want to go up, I pull back on what you would call the stick, which is in your right hand. Now I generate thrust to push the airplane higher in the air, and if I want to go down, I push forward with my right hand and I take thrust off the engine and the airplane goes down. When you think about it in that maneuver, the control of the engine went from your left hand to your right hand. You never really knew it.

That’s interesting. It reminds me of the debate over how to configure the flight control systems in the Osprey.

We felt if we could mechanize it that way it would be intuitively obvious to the pilot that he’s always controlling velocity with his left hand and he’s always controlling altitude with his right hand and the airplane would be simpler to fly and safer to fly. That was our theory.

It’s an unstable airplane like all fast jets are these days, so the fly-by-wire flight control system does a lot of cross-controlling with the control surfaces. The pilot says, “I want to go there,” and the flight controls will do whatever it takes to put the airplane there. The flight controls are much more blended in what they do.

It also has to be able to withstand combat damage, so if somebody shoots off a horizontal tail, you want to be able to reconfigure all the other flight controls to accommodate the loss of that flight control.

All that’s built in. So now when the pilot comes in for landing it goes like this. When you pass below 250 knots, you push a button that says STOVL and the airplane begins converting. You can push the button higher, but it won’t begin converting till you’re below 250.

The doors start opening and the shaft coming off the main engine engages the Lift Fan. That starts the Lift Fan turning as you’re slowing down. And now you’re transitioning from wing-borne flight to jet-borne flight; when you’re above about 120/130 knots, all your lift is coming from the wings. When you’re at zero, all your lift is coming from the engine, and when you’re in between those two numbers you have a combination of both engine and wing lift. The flight controls blend that so the pilot says, “I want to hover” at whatever altitude he wants; he just puts the airplane there. The airplane will slow down. If he doesn’t want to slow it all the way down and he wants to keep forward motion, he just tells it to do that. He selects a little switch movement and the airplane will maintain the 80 knots or 60 knots or whatever you want. You get over the landing point and it goes to zero and when he’s ready to go down, he pushes forward on the stick. The airplane comes down and touches down on the gear. There’s a weight-on-gear switch and when it connects, it pulls the engine to idle. So it’s very simple. The first time my chief test pilot flew it, he said, “You know I could have pulled out my iPad® and e-mailed my wife and told her to come out and watch me in the hover because I wasn’t doing anything.”

Well, that’s great.

I’ll tell you that all the pilots rate the short takeoffs and vertical landings. They give it a handling qualities rating, and none of the STOVL activity has had less than the top rating. Nobody’s found it to be difficult, and we’ve had a significant number of pilots fly the airplane now, including guys who were not trained to be Harrier pilots.

I think a lot of people don’t get what capabilities the Navy and the Marine Corps will gain, which they don’t have now, when the F-35B and the F-35C enter the fleet.

They’re going to get what we call a fifth-generation fighter. One element of a fifth-generation fighter is stealth. That means that the airplane is hard to find … not impossible to find … but hard to find on radar. It’s harder to track on radar and harder to kill on radar. The further you get down that chain, the more difficult it is. We do that through a combination of technologies that have evolved since the days of the SR-71 to the F-117 to the B-2 to the F-22 to the F-35. That technology has evolved quite substantially, particularly in the area of maintainability and ease of operation.

The airplane has a very low signature. So what does that do for you? It gives you the element of surprise. So your sensors are more effective in prosecuting any threats that are around and the other guys’ sensors are less effective, which gives you a very significant tactical advantage.

On top of that we’ve integrated a set of multispectral sensors that are day, night, and all-weather. So, you have radar, you have electronic warfare, you have infrared search and track [IRST], you have what we call distributed aperture, which is a series of cameras that stare out up in the infrared spectrum. And we’ve integrated those sensors now so the pilot doesn’t actually control the sensor. The sensors are all working all the time and they’re generating a picture for the pilot of the world around him. The pilot doesn’t really care or need to know which sensor is generating the information. He can, if he wants to know by doing a couple of switch movements, but he doesn’t need to know. So, what does that do for you? That gives you situational awareness on a level that you haven’t had before. And, when I combine the two, I get the element of surprise and near perfect situational awareness. I have a very large tactical advantage over anything else that’s in the air.

Today there are 11 big-deck carriers, probably nine or 10 of which are capable of operating at any one time. But, there’s also [a similar number of] L-class ships that carry helicopters and Harriers. With F-35, I now have a capability to take an F-35B on an L-Class ship as an asset to be employed on the first day of the war strike or intelligence-gathering capability. I now have a much larger, more flexible fleet.

You’ve basically doubled the number of carriers.

Right.

And you’ve got a supersonic strike fighter – a supersonic stealthy strike fighter for the Marine Corps.

And, if you look at the Navy, our CV variant changes Carrier Operations. This is the first stealth airplane in a carrier air wing, and it’s got much longer legs, relatively speaking. The CV jet has a combat radius over 600 miles and keeps that range with a combat load which today’s airplanes don’t. They can fly fairly substantial distances when they’re clean, but once you hang all of the ordnance outside of them, then they’re much draggier and shorter ranged.

And, in virtually all cases, they are hanging all sorts of ordnance on them.

That’s right, but we move our external fuel internal in this airplane. We carry about 20,000 pounds of fuel internally in the Navy airplane. And then we carry our weapons, both air to ground and air to air, internally when we’re stealthy – that allows us to maintain the high-performance capabilities that are compromised with external carriage.

The Navy now has a first-day-of-the-war deep strike, anti-access capability in the air wing that they haven’t had before...."

Thanks, didn't know he was a fromer test pilot.