What factors determine a plane's manuverability? Specifically, a jet.

Would vectoring the thrust help at all?

There are a LOT of variables that can affect maneuverability, and plenty of folks here can give more detailed advice as this discussion develops. (and I think it's a worthwhile one to have)

Vectored thrust is a very cool, but somewhat exotic solution. Since you didn't mention if this is a prop-powered pusher, ducted fan, or turbine, I'd be curious as to how you would do that.

One of the simplest ones is the aspect ratio of the wings. All things being equal, you'll find (like pylon racers and glider pilots) that higher aspect ratio wings give you more lift per degree of angle of attack, and tend to lose less energy in the turns than low aspect ratio wings. I'm working on a (pusher prop-powered) sport jet, and for this very reason, chose to use a higher AR than say, an FA-22. (image attached)

You didn't mention if you're using an existing design, or doing a new design yourself, so I don't know if all of these ideas are adoptable, but other things you can do to make the plane responsive are the traditional ones:

• Keep it light.

• Keep it strong, so you don't rip the wings off.

• Balance and trim the plane so it doesn't snap out of tight turns. (2 to 3 degrees of washout at tips may help.)

• If possible, create a fuselage shape that is low drag at low angle of attack, but can add lift when pitched "up" into the turns.

• Consider a slightly cambered airfoil, rather than a symmetrical one. (more lift)

• Consider the effect of high-lift devices such as flaps and leading edge flaps, as on full-size jet fighters.

I look forward to hearing everybody else's input on this...

Ok, thanks for the input. Let me see if I can clarfy.

[ul][*] I plan to build this plane from scratch with the help of other pilots. [*]I'm trying to render the plane to see if it is airworthy before wasting any money. [*] This will certainly have an EDF[*] Did you mean a wide fuselage?
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About the fuselage helping to create lift on pitch-up:

It doesn't necessarily have to be wide, but it's helpful to have a surface, whether it's the fuselage itself, or something like the canard surfaces of the Eurofighter or Rafale, which contribute very little to drag at low angles of attack, but "show" their surfaces on pitch-up. The same is true of rear-mounted ventral fins, as on the F-16, but in reverse. They produce almost no drag at low AOA, but help prevent over-rotation at high AOA. (Learjet, Piaggio, and Raytheon use them on their business aircraft, and they contribute to directional stability, too.)

In the case of my design (previous post) I used lessons learned from slicing up an FA-22 model, and analyzing it the best I could. I found that the maximum thickness point of the fuselage (excluding the canopy) was coincindental with the projected maximum thickness point of the wings... In other words, the fuselage shape is to some degree, a continuation of the wing's airfoil, with the "chine" at the front providing a camber line. (Lockheed-Martin has said that in cruise flight, the fuselage contributes 50% of the lift!) You can look at this from at least two points of view... The American approach seems to be to use sharp chines. The Russians, on the other hand took the approach of actually extending a relatively thick airfoil toward the nose of some of their jets, such as the Mig 29 and SU-27, and the French chose something in between for their Rafale. (images attached) I selected the American approach.

These things are going to be "science experiments", at model Reynolds numbers... Difficult to precisely predict in advance, but to me at least, worth trying. I should have flight test results on my design in about 90 days, and will post the results here. I've also included a small (again, FA-22-ish) "chine" at the nose, in the hope that at high AOA, the chine will create inward-rotating vortexes, helping the air stick to the plane.

Interesting and fun, regardless. Only the results will prove or disprove these ideas.

PS> My particular design is realtively wide for a different reason...
To keep the semi-scale look and shape of a modern fighter, while keeping the engine enclosed, and avoiding the use of drag-producing (fake) inlet ducts, a smooth curve was required, which drove the design to where it is today. The jet "intakes" on my design are not actually there at all, but are graphically faked to provide the illusion. (image attached)

Keep us posted on your results. These things are always interesting to watch, and we all might learn something new.

For models we get all the maneuverabiltiy we need through light weight and big control surfaces. For a short span jet like the modern fighters the span is so low that high roll rate is not really a problem. A long high aspect ratio wing like a U2 has lots of lift but it also has lots of roll damping action due to the long span rolling through more air. So short and squat is the best planform for fast roll and pitch rates even though it is not the best form for creating lift. GO easy here. With short span models flying at high airspeeds a little aileron goes a long way. When I said "big" I was talking in relative terms. I wouldn't go more than about a 10% wide chord aileron for good performance with less chance of flutter. Wide controls can often flutter at higher speeds.

To pitch fast you need some significant elevator area and throw combined with a somewhat rearward balance point. A "nose heavy" model will be stable but also lazy to pitch both up and down as well as requiring a lot of up trim to hold level. That up trim needs to be reversed when inverted. The further back the balance point towards the neutral position the more sensitive the model and the less up (and down when inverted) trim you need for level flight.

Moments of inertia also come into play. Basically keep your radio gear, batteries and EDF unit as close to the aerodynamic neutral point and grouped as tightly as practical. Putting the heavy bits out at the ends of the fuselage will slow the pitch response and also could cause the pitch maneuvers to overshoot until the surface areas of the fuselage and stabilizers can damp the motion. That can make it hard to be precise in your flying.

Both Mike James, and BMathews have given some excellent comments regarding “maneuverability”. In a generic sense, since a maneuver is basically an acceleration, simply keeping the mass low, and the force high will maximize it. In other words light wing loading and plenty of power and control. However from the standpoint of designing an aircraft, not all maneuvers are created equal. There is no one configuration that is best for all maneuvers. That is the reason that a pattern plane doesn’t look like a 3D model which doesn’t look like a pylon racer, etc.

Features that enhance one maneuver may well be detrimental in performance of another. For example, if snap maneuvers are the priority, an airfoil with abrupt stall characteristics may be the best, whereas if tight turning radius without the danger of sudden unexpected stall is more important, one that reacts more gently might be best. Tight turns will usually dictate use of a somewhat cambered airfoil, but if inverted flight were the priority, a symmetrical section would be the choice. For knife-edge flight, roll coupling should be a minimum, but again for snap maneuvers, it may speed up the roll rate. As for vectored thrust, that is exactly what a 3D airplane uses when hovering. The tail surfaces deflect the propwash to control the machine.

To design an aircraft, the first step is to determine the desired flight profile and define what maneuvers are priority. Only then are you prepared to begin determining the features to produce the results you want. A simple generic approach will usually result in a simply generic model.

In model R/C combat, where manuerability is king. The most manuverable designs have high aspect ratio wings with a large amount of taper. For instance, a really hot wing right now is a slightly modified Clark Y with a root chord of 11.5" and tip chord of 5.5 to 6" and a typical span of 64". These wings are flown on .15 and .25 sized planes. This is the most practical example of manuverability in model R/C airplanes. These wings give a wing loading of 12 to 14

Comment on the chines: F/A 22 has sharp chines unlike the rafale, and the MIGs because of stealth considerations, not aerodynamic.

Brian

thojo - I just looked at one of the modern combat models. The high aspect ratio isn't ideal for good roll response, something along the lines of a modern IMAA airplane is better being a compromise in roll acceleration and damping.

The high aspect ratio airplane would seem to double your chances of getting a ribbon cut (compared to a "normal" configuration) - then since with models we usually have more than enough roll rate the penalties in roll due to the high aspect ratio (high Clp and roll moments of inertia) are easily handled. The modern combat model did have a short tail moment arm and small wing chord which gives lower pitch moments of inertia and good pitch response.

But the configuration is driven by things other than optimum maneuverability - cutting the ribbon being the main one.