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Basic Fighter Maneuvers, Part II
By Len "Viking1" HjalmarsonArticle Type: Training
Article Date: July 11, 2001
Back To Part I
The Plane of Motion
“The important thing [in tactics] is to suppress the enemy's useful actions but allow his useless actions. However, doing this alone is defensive.” Miyamoto Musashi (1584-1645)
Japanese Samurai & Philosopher
Before we talk about where we want to go, we need to understand where we are. Before we talk about circles, let’s understand alignment and the plane of motion. Very simply, the plane of motion is the flight path of your aircraft along its fuselage line through the rudder. In this next image you can see two aircraft, each with their own plane of motion, or flight path.
Split Planes of Motion
Since these two planes are not aligned we refer to them as split planes. When two aircraft are maneuvering within their own planes of motion they are out of plane with one another. BFM requires you to maneuver out of plane in order to gain turning room and a positional advantage. The basic requirement, as with all BFM, is to manage closure rate and attain a preferred alignment for a guns solution.
Now consider the split plane image from the perspective of closure rate. While the air speed of each aircraft might be 240 knots, the closure rate is something around 350 knots. These two aircraft are not yet in a dogfight, but merely passing each other head-to-head. The best possible snap shot has a fairly low probability of scoring a hit. The pilot must maneuver not only to get in plane with the bandit, but to lower the closure rate.
If instead of 30 degrees off the nose the pilot was 30 degrees off the tail, the closure rate would be drastically reduced, perhaps to 100 knots or less. It would be necessary to think of ways of reducing that rate by another maneuver or chopping the throttle.
What do we learn from this? The throttle is only one method of changing your speed relative to another aircraft. The closure rate can be as readily changed by changing the position of your nose. In other words, whenever your airspeed takes a different vector relative to the bandit, you alter your closure rate. Your airspeed itself can be identical, but whenever your flight path to the bandit varies, your closure rate will also vary.
Well, wait a minute. When would you need to alter your flight path, and how would you determine how much alteration is enough?
Turn Circles, Turn Performance and Separation
Argh! you mean there are more terms to know? Only a few more, and then we can begin to understand how important it is to think in terms of circles and the three dimensional world instead of a flat plane.
Back in the 60s the results from air combat performance in Korea were being assessed, and some of the first books about air combat maneuvers were being published. At that time the only “modern” text in existence was the one written by Frederick “Boots” Blesse based on his experience in Korea, “No Guts, No Glory.” In that text were the basics of fighter tactics and maneuvers, but there had not yet been much formal consideration of turn performance.
Then along came some bright fighter pilots, and EM diagrams were born. These diagrams plot true airspeed on one axis, and turn rate in degrees per second on the other axis.
“A good fighter pilot, like a good boxer, should have a knockout punch…You will find one attack you prefer to all others. Work on it till you can do it to perfection…then use it whenever possible.” Group Captain Reade Tilley
RAF, 7 Victories, WWII
EM Diagram of Spit IXe
In this diagram we can see that the Spitfire IXe can turn at 37 degrees per second at 220 mph and 500 feet altitude. This is the instantaneous turn performance of the Spit. Comparing a second diagram that plots the performance of the P-38L, we can see that the Spit will turn inside the P-38 at the same altitude.
These “doghouse plots” (so called because of their characteristic shape) tell us that different aircraft need a different sized circle to complete a turn at a given airspeed and altitude.
Naturally, the combat load of the aircraft will also impact these figures (full fuel tanks and external ordnance drastically affect performance).
EM Diagram by Joseph Hong
There are a few important points to notice about these diagrams. First, the peak of the doghouse shows the maximum turn performance, or the instantaneous performance. But no aircraft can maintain its maximum performance for more than one turn. After a few seconds of maximum performance the speed of the aircraft has dropped and the pilot can no longer maintain peak performance. The aircraft moves rapidly toward its sustained turn performance. The descending green line represents sustained performance as the speed of the aircraft drops. At 150 mph the Spit IXe can maintain a turn rate of about 24 dps.
What does this mean for the combat pilot? It means that the turn radius of a given aircraft the instant it begins the turn is at its highest. As soon as the control surfaces are loaded and the pilot is pulling G’s, the turn rate drops and the turn radius increases. The turn radius at 150 mph will be much greater than when the pilot makes his first turn at 240 mph.
“The characteristics of the aircraft determine the tactics. The Zero could out-maneuver, out-climb, out-speed us. One Zero against one Grumman is not an even fight, but with mutual support two Grummans are worth between four and five Zeros, and so on up.” Major JN Renner
USMC. Command Officer, VMO 251
Now let’s take this discussion and translate it into the world of BFM. There are two immediate applications, a general one and a specific, case by case application.
The general application is simply this: coming into a fight against any bandit, you must know the performance of your aircraft and how much space you require to complete a turn at any moment that will put you in the weapons engagement zone (WEZ). You must know both the instantaneous turn performance and the sustained turn performance.
Spitfire Kill in WarBirds III
This became very relevant to me a few days ago when I encountered a Spit Mk Vb in WarBirds while I was flying the Bf 109F-4. I was five hundred feet below the Spitfire and I began a lead turn shortly before the merge.
While the sustained turn performance of the two aircraft is very similar, the instantaneous performance of the 109 is superior. Since I was also five hundred feet lower and began a lead turn, I had some serious advantages over the Spitfire. In fact in just two maneuvers I was high and ten degrees off the tail of my surprised opponent. Had this fight continued for a couple of more turns the outcome could have been different.
Angle off the Tail (AOT)
The engagement zone is fairly small in practice since high angles of deflection increase closure and make overshoot more likely.
