Military Embedded Systems

Fighter jets and the kill web


June 28, 2018

Ray Alderman

VITA Standards Organization

WARFARE EVOLUTION BLOG: In the previous article, we explored the transition from the static kill chain to the dynamic kill web in future warfare scenarios. Now, let?s look at how fighter jets fit into this new model. That requires a review of the fighters being flown by the U.S. and our allies today. We also need to consider what the Russians and the Chinese are doing with their fighter jets.

This analysis gets complicated fast. There are five basic missions for fighter aircraft: air superiority (controlling the airspace over the combat zone), all-weather attack (bombing enemy infrastructure and military targets), all-weather intercept (aerial dog fighting with enemy fighters), close air support of ground troops (CAS: bombing and strafing enemy troops), and nuclear attack (yes, some of our fighter jets are rigged to carry nuclear weapons). Air-to-air missiles like the AIM-120, with a range of over 100 miles, raise questions about the need for dogfighting capabilities in fighter jets today.

Each mission listed above demands unique performance levels, flight characteristics, and ordinance loads for the aircraft. Yet, we can’t afford to design, build, and maintain five different aircraft types. Obviously, we have to make trade-offs and build one or two fighter jets to handle all five missions. What we get are multi-role fighters that are adequate, but not perfect, for each mission. The design phase of the F-16 used 78 variables and 1,272 hours of wind tunnel tests in the trade-off analysis. Fortunately for those reading this article, I only use five variables in the table below.

To read more Warfare Evolution Blogs by Ray Alderman, click here.

The left column of the table starts with U.S. fighter jets in service. Our first stealth plane, the F-117 Nighthawk, was officially retired in 2008. But there are a small number of them still flying at Nellis Air Force Base (AFB), Nevada, probably as stealth test beds, so we left them off the list here. Next, we have the European Union fighters. Then, we include two CAS aircraft (A-10 and A-29), for comparison. The next fighter is the new Russian SU-57, followed by the new Chinese J-20 and J-31. We excluded the Chinese “Dark Sword” unmanned fighter jet concept, exposed in early June, because there’s no data on that aircraft at this point.

Across the top of the table, years refers to the number of years from design-start to when the plane went into active service. RCS is radar cross section in square meters (how big the plane looks on enemy radar). These numbers have been updated from a previous RCS article. Many of our 4G fighters have received stealth enhancement upgrades: radar absorbent coatings, new engine air-intake geometries, gaps between panels have been filled, low-reflection exhaust nozzles designed, and rear vertical stabilizer angles have been modified.

WL is wing loading (weight of the airplane in pounds, divided by the upper wing area in square feet). T/W is the thrust of the engines divided by the weight of the airplane. Engines refers to how many engines that aircraft uses. Speed is the maximum speed of the aircraft (M is MACH, the speed of sound). I put these numbers together from numerous reliable websites, but don’t take them as absolutes. Some of those websites disagree.

Back in the 1960s and 1970s, Air Force Col. John Boyd was instrumental in the design of the F-15, F-16, and A-10. He came up with a process called EM Theory (energy/maneuverably analysis). His work suggests that a lightweight fighter plane, the sports car of fighters for air superiority and intercept (dogfighting) missions, should have a WL of 60-65 pounds, a T/W ratio of 1.4, and a max speed of M1.6. A multi-role fighter, the SUV [sport utility vehicle] version of fighter planes, should have a WL of 80-90 pounds, a T/W of 0.97, and a max speed of M1.4. Fighter-bombers, the dump trucks in the fighter category, will have a W/L of 100 pounds or more, a T/W of 0.75, and speed of about M1.0.

RCS: The first thing you see from the table is that building a fighter jet with an RCS below 1.0 square meter is hard. With very small RCS values, a plane has the element of surprise and high survivability against enemy air defense radar and SAM missiles (surface-to-air). And, they have the same advantage against enemy interceptor jets. None of the EU fighters can compete with the F-22 and F-35 RCS values. China may have mastered some stealth design elements, but those RCS numbers are estimates since they only have about twenty-eight J-20 prototypes and two J-31 prototypes flying. Russia has about ten SU-57 prototypes flying, so their numbers are also estimates.

Secondly, we need to ask why the first three U.S. fighters, all the European Union fighters, and the two CAS planes (A-10 and A-29) have higher RCS numbers compared to the F-22 and F-35. That’s because they were designed for missions in uncontested airspace and they all carry missiles and bombs on pylons (hard points) under their wings. The F-22, F-35, SU-57, J-20, and J-31 carry their bombs and missiles inside the fuselage of the aircraft. Any airplane carrying ordinance under its wings lights-up a radar screen.

WL: Wing loading tells us how maneuverable an aircraft is in flight. The lighter the wing loading, the smaller the turn radius and the lower the stall speed. As you can see, the three European Union fighters are close to Boyd's numbers for lightweight fighters. That says that these jets were designed primarily for defensive air-to-air combat missions, as sports cars. Loading-up their wings with bombs for offensive missions will push their WL numbers up to 80-100 pounds per square foot, and they will have the maneuverability of a dump truck. Just look at the WL of the A-10 and A-29: they are both designed purely for CAS missions. They fly low and slow dropping bombs in uncontested airspace, so no need for stealth or maneuverability. Look at their air speeds for further verification. Obviously, the Tornado (Germany, Italy, Spain, United Kingdom) was designed as an attack bomber, with a WL of 156, a high RCS number (8), and a low T/W ratio (0.77). It flies high and fast, dropping bombs along the way. It’s a dump truck.

T/W: When you look at the thrust-to-weight ratios of the U.S. fighters, you can see that the F/A-18 was designed primarily as an all-weather attack plane. That’s what the “A” stands for in F/A-18. The F-35 and F/A-18 are closest to Boyd's numbers for a multi-role fighter. They perform like SUVs. Look at Russia’s SU-57: with the T/W of 1.36, a speed of M2.0, and WL as low as 65 pounds (estimate), it best fits his numbers for a superior dogfighting plane, a sports car. That says the SU-57’s primary mission is to intercept and shoot-down US and EU fighter jets in an air battle. Look at the T/W of the A-10 (0.36) and A-29 (0.31). That's additional evidence that they were designed as dump trucks.

Engines: Obviously, two engines can push a plane through the air faster than one engine, but they require more fuel. Two engines can carry more ordinance, and with the additional fuel, that adds more wing loading. Two engines is a trade-off indicator, along with the WL, that the plane is a multi-role fighter.

Only three jet fighters in this table have a single engine: the F-16 Fighting Falcon, the F-35 Lightning, and the JAS-39 Gripen (the A-29 is a propeller-driven plane). These are all air superiority planes. More than 4,500 F-16s have been built and put into active service worldwide. According to web sources and my calculator, about 300 F-35s have been delivered to the U.S. Air Force, US Navy and Marines, and a few going to our closest allies. It took seven years to build and ship those 300 planes. They will begin to replace the F-16s over time. Also, Boeing has made significant modifications to the F/A-18 and created the Super Hornet, including a weapons bay inside the fuselage. It has better RCS and performance characteristics that previous Hornets, for attack missions.

Years: As you can see, it takes the U.S. about 14.6 years, on average, to design, build, and deploy new fighter planes. But the F-22 and F-35 took an average of 21.5 years. One reason might be software: the F-22 contains 2 million lines of code, and the F-35 contains 8 million lines of code. The Block 3 upgrades to the F-35 contain 10 million lines of code. Additionally, there’s another 16 million lines of code in the F-35 logistics system (computerized parts lists, assembly diagrams, blue prints, etc) and flight simulation systems (a total of about 26 million lines of code). For comparison, the F-16 contains 150,000 lines of code. Manufacturing mechanical parts and putting them together takes less time than debugging, verifying, and maintaining millions of lines of code.

It took the Russians nearly 30 years to develop the SU-35, and the Chinese took an average of 12.5 years for the J-20 and J-31. But the Russians have not mastered stealth while the Chinese have not mastered how to design and build engines. They use Russian engines in their planes, to cut their design-to-deployment time.

The Europeans take 16.5 years, on average, to deploy new fighters. But their planes are designed for defensive purposes, with much lower complexity and capability. In April, Germany and France announced they would start the design of the next Eurofighter, through cooperation between Dassault (who makes the Rafale) and Airbus (who makes no fighter planes). The program is called FCAS: Future Combat Air System. Japan, Turkey, India, and South Korea all have indigenous design programs ongoing for their future fighter planes. If you extrapolate the numbers in the years column of the table, by the time any of these countries deploy new 5G jets, the U.S. will be deploying our 6G fighter planes (called PCA: Penetrating Counter Air). Here’s an artist’s conception of that fighter jet. <>

This brings-up the "high-low mix” arguments of the past. They stressed that we need tens of highly sophisticated expensive aircraft, like the F-15, feeding targeting information to hundreds of low-technology inexpensive fighters, like the F-16. We are seeing a rebirth of that strategy today. Building many low-complexity armed drones is much cheaper that building more high-complexity fighter planes. The AFRL (Air Force Research Laboratory) has released a promotional piece showing an F-35 controlling six drones. They show-up at about 3:10 in the video. <>

How will the U.S. integrate our allies' fighter planes into our developing kill web? It will be painful, unless they buy F-35s (we do not sell F-22s to anyone). Our allies' older fighters are antiquated, and their new 5G fighters won’t be in service for 16.5 years. By then, the US will have 6G fighters in the air (14.6 years, if we get better at debugging code). The German-Franco FCAS fighter project contains some political and economic elements: the creation of government jobs, development of military platforms for export to other European Union (EU) countries, and the reconstruction of the diminished military-industrial base in the EU. A brief look at the latest SIPRI worldwide military spending report endorses that statement. <> If you want to explore the topic of aircraft design and performance, without getting a headache, read Grant Hammond’s book, "The Mind of War."

There you have it. You now enjoy an elementary understanding of a fighter’s missions, and a few design elements for those aircraft, without bringing drag polars, fuel-fractions, and engine bypass ratios into the conversation. If the values in the table for fighter jets were interesting, you’ll love the numbers for big long-range bomber aircraft. That’s the target for our next installment, so be prepared for another table of numbers.

Ray Alderman, Chairman of the Board of VITA, presents how embedded electronics and open standards enable enhanced C4ISR - from sensors to signal processing to real-time communications. Join us on August 30 at 2pm EST with Military Embedded Systems and VITA Technologies for the webcast titled: Leveraging Open Standards and C4ISR for Multi-domain Challenges in Modern Warfare. To Register, visit: