A White Paper By: Lockheed Martin
The F-35: Creating a 21st Century Fighter
Advanced stealth – built in from the beginning – is a defining characteristic for 5th Generation combat aircraft. It is not however the only one.
The F-35 provides a glimpse of the 5th Generation fundamentals in action. From the ground up, the F-35 was built to be an integrated fighter capable of playing a pivotal role in joint and coalition operations. It’s designed for the future and developed on a foundation of more than 40 years of real world combat experience.
In a real sense, the F-16 and F-22 were the risk reduction programs for the F-35. Many lessons learned were incorporated into the F-35.
With its integrated systems and software upgradeability, the F-35 is laying the groundwork of ever-evolving capabilities for decades to come. Stealth is just one enabler of a 5th Generation fighter and in actuality we’ve had stealth in the past, but until the F-22 it wasn’t coupled with combat agility. Consider the B-2 and F-117. Both are very stealthy but lack agility, so much so that they could only be deployed at night.
The F-22 and the F-35, which also employ stealth, were designed for agility. We want to fly them day and night and in all combat conditions. They are not designed to be specialized aircraft for narrowly defined mission sets.
Building the airplane from the ground up means that what used to be on the outside of the airframe must be moved inside. This includes sensors, fuel and weapons.
The sensors are integrated through the fusion engine, which is another discriminator that makes the F-35 a 5th Generation aircraft.
True 5th Generation stealth must be built into the aircraft. It can’t be added post production. It’s just not possible to make a 4th Generation aircraft stealthy because you’ve got to hang tanks and stores and pods external to the airplane’s exterior.
Consequently, agility and radar cross section are compromised. You also lose agility because there’s a huge aerodynamic penalty for hanging anything outside the airplane.
So, that’s what caused us in the beginning to say the airplane must be agile and it must be stealthy, which requires us to put the fuel, weapons and sensors inside the aircraft.
One of the challenges we had was to make an airplane that had the low speed characteristics of the Hornet and the high speed of an F-16.
The Hornet can fly slow extremely well and get to high angles of attack and point the nose all around. The F-16 can’t do that as well, but the F-16 can fly extremely fast and can recover energy quickly. The Hornet does not do that very well. Once they get into an energy deficit, it’s hard for them to recover because of the low thrust to weight ratio and the aerodynamic penalty of sensors and weapons in the airstream.
The F-35 incorporates the best of both in flying qualities: it will fly slowly at high angles of attack; it can fly supersonic for extended periods of time; and it regains energy quickly because of its large engine.
The engine is another example of building stealth into the airframe from the ground up. In a legacy aircraft, the power plant creates a significant element of combat visibility. This impact to radar cross section comes from the front and rear of the engine. Ideally, the engine is totally hidden from view as in the B-2 and F-117. This approach impacts agility so a different design is found in the F-35. In front of the F-35’s engine is a bifurcated diverterless intake which totally blocks line of sight to the compressor face while not severely impacting performance. At its rear is a reduced signature nozzle.
A final consideration with regard to building from the ground up is how stealth is manufactured into the aircraft. The F-35 is manufactured with stealth built in as well.
As Bill Grant, Lockheed Martin F-35 Supportable Low Observables Integrated Product Team leader, has put it:
From day one, supportable LO has been a key entity on the program and has had a profound influence on the very design of the airplane. In fact, the element that is manufactured into the skin was an initiative brought about by our LO maintenance discipline. We’ve also had a profound influence on the selection of the materials and then once they were decided upon, we helped refine the properties to make them more workable for field use.
And Grant added:
Our system requirement was for end of life, which means that throughout the 8,000-hour service life of the jet, it is to remain fully mission-capable. So we anticipated that the amount of maintenance that would be done over the life of the airplane and anticipated that in the design.
So when we deliver the jet, it’s delivered with a significant margin of degradation that’s allowed for all of these types of repairs over the life of the airplane, again, without having to return to the depot for refurbishment. There may be some cosmetic-based reasons why the jet might go back to a facility to get its appearance improved, but from a performance-standpoint we recognize no need to do that.
An example of the new approach to stealth and the new combat systems can be seen in the Northern Edge 2011 Exercise.
This exercise is a major U.S. joint forces exercise held in Alaska which tests the ability of the various elements of the forces to work together.
With the new emphasis on the Pacific or the Asian Pivot, the exercise highlights the working of U.S. forces in dealing with the Pacific challenge.
In this exercise, fifth generation aircraft each played an important role.
The F-22s demonstrated their air dominance role, and then shifted to an air battle management role.
The F-35 combat mission systems flew in the exercise on a test bed aircraft.
As a Joint Program Office release underscored:
Participating in Northern Edge for the second time, F-35 Joint Strike Fighter sensor capabilities were tested in Alaska’s premier multi-operational environment from June 13-24, 2011. Hosted by Alaskan Command, Northern Edge is a biennial U.S. Pacific Command exercise that prepares joint forces to respond to crises throughout the Asia-Pacific region.
This year provided an invaluable opportunity to observe the performance of the F-35 JSF systems in multiple robust electronic warfare scenarios.
The AN/APG-81 active electronically scanned array radar (AESA) and AN/AAQ-37 distributed aperture system (DAS) were mounted aboard Northrop Grumman’s BAC 1-11 test aircraft. Making its debut, the AN/AAQ-37 DAS demonstrated spherical situational awareness and target tracking capabilities. The DAS is designed to simultaneously track multiple aircraft in every direction, which has never been seen in an air combat environment.
A return participant, the AN/APG-81 AESA demonstrated robust electronic protection, electronic attack, passive maritime and experimental modes, and data-linked air and surface tracks to improve legacy fighter situational awareness. It also searched the entire 50,000 square- mile Gulf of Alaska operating area for surface vessels, and accurately detected and tracked them in minimal time.
Navy Cmdr. Erik Etz, Deputy Mission Systems Integrated Product Team Lead from the F-35 JSF Program Office, said the rigorous testing of both sensors during NE 2011 served as a significant risk-reduction step for the F-35 JSF program. “By putting these systems in this operationally rigorous environment, we have demonstrated key war fighting capabilities well in advance of scheduled operational testing,” Etz added.
Having the exercise in June had its seasonal weather challenges for system operators to adapt and overcome. Inclement and cloudy weather hampered in-flight visibility. The DAS was significant in providing clear and discernable horizons, and views of ground features and nearby aircraft. It also wasn’t dark enough for testing night vision functions. A surrogate test visor was used for displaying DAS imagery to the operators.
“The implications of F-35 JSF sensor systems for air-land-sea battle are immense,” said Peter Bartos, Northrop Grumman’s Test Director.
In short, during this important joint exercise, the presence of 5th Generation fighters in the air package increased the overall forces’ mission effectiveness by enhancing survivability and lethality for entire package.
It showed as well that 5th Generation fighters enhanced battlespace awareness enhanced overall mission effectiveness of the entire mission package.
And finally, the exercise showed that 5th Generation fighters with this enhanced SA tend to function as Air Battle manager for entire package. Even when F-22 was weapon bingo it stayed in fight as battle manager!
In other words, the exercise highlighted the cross between current and future capabilities, which are central to the future of airpower.