One Good Turn Deserves Another
Learning to turn well in a fighter aircraft is something that’s much easier said than done. This will not be a definitive, doctorate level dissertation on the subject. I’ll go over the basics here and hopefully help get you on the right track. This discussion is geared toward the F-16 Fighting Falcon. However the principles discussed are just as valid for any fighter aircraft. First we’ll look at Turn Rate & Radius, then corner airspeed and then how to lead turn. Energy Management also plays strongly into turning well. We’ll hit that up at the end of this lesson.
Turn Rate: The rate at which an aircraft can turn or rate it’s nose while turning. In other words if you’re pulling a circle, rate is a definition of how fast you get around that circle. Don’t just think of rate in terms of complete circles though. I give that as an example to help you visualize and understand rate. Turn Rate is usually expressed in reference to instantaneous and sustained rates and is measured in degrees a second. Instantaneous is exactly what it sounds like…. How much rate you can command from an aircraft immediately as you turn. Sustained is the rate you can sustain through a turn.
The F-16 has a 26 degree/sec maximum instantaneous turn rate. I haven’t found reliable figures for the Vipers max sustained turn rate. In the Tac Ref in F4 it states 13 degrees/sec. I promise you I can pull significantly better than that, right around 18 deg/sec. Coincidentally several reputable online sources state 18 deg/sec sustained rate. Of course you’ll need to be at the right airspeed to capture the best rate, both instantaneous and sustained. It’s important to realize that the F-16 is one of the very, very few (in all probability the only operational) aircraft able to pull a sustained 9 G turn.
This fact, along with the F-16’s extraordinary sustained turn rate capability, are among the things the Viper is most legendary for. In Falcon 4 we have to deal with the fact that the Viper as modeled cannot perform a sustained 9+ G turn as it can in real life. We’ll work around this as well as the fact that many other aircraft types are actually over modeled. At times throughout this training I’ll point out differences between actual vs. Falcon 4 performance info so that you’ll be knowledgeable on both. Rate is needed to achieve weapons parameters or defeat attacks.
The F-16’s turn rate increases very rapidly from slow speed up to 330 KCAS, at which point the rate is the highest. Rate allows the attacker to match or exceed the turn rate of his adversary and establish lead for a gunshot. The attacker needs a turn rate advantage that will allow him to pull his nose onto the bandit to employ the AIM-9 or point to lead pursuit for a gun shot. It is important to note an attacker with a higher sustained turn rate can maintain a positional advantage against a defender with a smaller turn radius but reduced rate (Figure 13).
For example, in order to employ the AIM-9, you must have a turn rate that will allow you to keep your nose within approximately 30° of the bandit for tone acquisition and missile launch. The ability to maintain a high sustained turn rate while the defender sacrifices sustained rate for a tighter turn is another key concept in understanding BFM. In this sense, a turn rate advantage is more tactically significant than a smaller turn radius. Keep in mind an old fighter pilot saying that’s always been very true; “Rate Kills! ”
It’s important to note that the F-16 turns better with afterburner (AB). Believe it or not this is not always the “norm” for most combat aircraft. AB in the Viper gives a better turn capability because it allows the pilot to sustain airspeed and thereby sustain a higher turn rate (assuming near corner velocity). In addition, maneuvering at higher AOA’s results in a greater portion of the aircraft’s thrust vector to be pointed toward the center of the turn, which also helps the F-16 maintain a smaller turn radius and greater turn rate.
To achieve the highest turn rate possible, slow or accelerate towards corner velocity speed range as quickly as possible and turn hard to generate maximum angles in the shortest time. Be aware that this is not always the optimum thing to do. However when you decide it’s time to command the highest rate, this is what you need to do. Turn Radius: The diameter in which an aircraft can turn a partial or complete circle at a given altitude and speed. The higher the speed the larger the radius, or circle, the aircraft will make in the sky.
Conversely the slower the speed the smaller the radius. Turn radius determines the size of the turn circle. This radius is based on the aircraft’s TAS and radial G. In a fight, the size of the circle and the relative turn rate capability of the two aircraft, will determine how well the pilot can solve the angular problems the defender presents. The objective is to work to where available G will allow the attacker to point his nose at the defender to achieve a missile or gun shot with an acceptable specific power (Ps) bleed-off.
How well an aircraft can turn is a function of the turn rate and radius it generates. As already stated, Radius defines the size of an aircraft’s turn or its turning “circle. ” In the F-16, turn radius at max AOA/G is relatively constant over an airspeed range of 170 knots calibrated airspeed (KCAS) up to 330 KCAS. Above 330 KCAS, turn radius increases slightly as max G is obtained (440 KCAS). Above 440 KCAS, turn radius increases dramatically. The chart at left graphically depicts the effect of airspeed on radius. Note also how rate is affected.
Understanding the concept of Turn Circles is another important principle for you to grasp in order to be a really effective BFM practitioner. Again, we’ll be going into this and many other things discussed in this lesson in greater detail later on in the course. For now concentrate on understanding how both radius and rate affect the fight. Knowing your adversaries capabilities in both these areas across his flight envelope and knowing your own in the Viper, or whatever other aircraft you are flying, will help you decide how best to approach employing BFM at different times in the fight.
One thing to note here is that offensively, sustained operations are not possible in the same plane against a defender with a smaller turn circle (radius) assuming similar turn rates without inviting an overshoot/reversal situation. Alright. In plain English what this means is that if you run into a bandit that can turn in a tighter radius while maintaining a similar rate as you…. Things are gonna get really uncomfortable real quick if you continue a turn in the same plane with him. You need to use the vertical/get out of plane. That’s either vertical up or down and not necessarily 90 degrees for either.
Depending on the situation a little either way may do. Corner Airspeed: Each aircraft has a specific speed at which it can turn at both the best rate and tightest radius. This is not to say the absolute best rate or the absolute tightest radius the aircraft is capable of, but rather the best combination of both. Because of the F-16 flight control system, the F-16 does not have a true corner velocity. It has a “corner plateau” which is an airspeed range of 330 – 440 KCAS that produces a good turn rate based on available G. In this chart you can see the “corner plateau” of the Viper.
Note how both radius and rate stay fairly constant between 330 and 440 knots. Note also how rapidly radius increases and rate decreases above 440 as well as the decrease in rate below 330. As mentioned previously Radius stays fairly constant all the way from 170 to 330 knots or so. We’ve discussed turn rate & radius as well as corner airspeed. Understanding how these factors play into the fight is key to your ability to not only survive but dominate your adversary. It’s more than just knowing your own aircrafts performance in these areas, it’s knowing the enemies as well.
On top of that your ability to exploit this knowledge is what will make the difference in the end. As an example. F-4F’s from Holloman AFB’s 20th FTS routinely flew and won against F-15’s during the 114th FTS’s bi-annual Sentry Eagle Air to Air meet. The most interesting matches were the F-15 instructors vs. the F-4F instructors. Even though the F-15’s had the advantage in power, radius, instantaneous and sustained rate, the F-4’s were able to still come out on top. Why? Partly because the F-4 pilots had more experience and seat time.
Many of the F-4 instructors had more than 3,000 hours in the F-4. Bottom line though is that they flew better BFM. They knew their jet and they knew their adversaries jet and it’s capabilities to a better level than their adversaries did. They used this knowledge to overcome the advantages of the enemy by taking advantage of their own aircrafts systems and flight characteristics. The moral of this story? Study and train hard. Know your jet inside and out and explore and become a expert at handling her. Know your enemy as well.
Study of other aircraft and knowing what their performance actually translates to in the fight, will make the difference between killing or dying. Here’s another example. The F-18 has better nose pointing ability at lower speeds (below 240 knots down to 190) than the F-16. Nose pointing ability is rate & G/AOA. Commonly referred to as Alpha in fighter pilot speak. Does this mean that the F-18 will always win in this speed range? Think about that question. What are the reasons you think so or not? We’ll use group discussion to answer it in depth. There’s way more to it than most people think.