Ion Design Goals

When we first began working with our engineers, we broke down our design specifications into two major groups: Requirements and Goals.

Simply put, requirements were items that had to be included or specs that had to be met. Conversely, goals were things that we felt would be nice to have, or things that were "cool" but could be costly or heavy.

Below are the edited and annotated program requirements and goals, with a little commentary at the end.

Requirements:

Aircraft is safe in all flight regimes

So far, so good. Flight testing to date has not revealed any bad habits or unsatisfactory flight characteristics.

2 seats, in tandem, with rear occupant elevated for good visibility

Done. The rear occupant (spouse, father, mother, brother, sister, best buddy or student) is elevated above the front seater by about 8.5 inches (22 cm). It is a really good view.

Twin boom pusher configuration

Done. It isn't the easiest configuration in the world to engineer and build, but it does allow for that great pusher visibility and it looks very sexy (and you'll look sexy flying it, won't you?)

Interchangeable wing sets for cross-country flight versus slow sightseeing flight

Done. You can buy one or both sets of wings, depending on your personal desires. The cruise wings give you an extra 20 or so knots of cross country speed, but their stall speed will be above the LSA limit--if that's important to you, stick with the loiter wings.

Aircraft is LSA compliant

Done, if the loiter wings are used.

Minimum of 20 gallons of fuel (safe stowage)

Done. Fuel tanks are in the wing roots and the current capacity is 24 gallons.

Aircraft can be easily put in an enclosed trailer

Done . . . sort of . . . this was a headache. The "easy" part isn't so easy, but it can be done. There's a whole section on it (click) below.

Capable of basic aerobatics, with 4.4 G's positive and 2.2 G's negative

Done. There are folks who wanted full aerobatic category G loading, but frankly it's really expensive to engineer and build a plane to those specs without sacrificing something else. We did a survey of our existing customer pool and it scored low as a priority.

Capable of safe flight with engines within an 80-125 HP range

We have dropped all pretense of flying this thing on anything under 100 HP. Once you see it in person, the plane is physically pretty large. Two big people on a hot day with full fuel on 80 HP is a bad idea. We want to see you have at least 100 HP to stay out of the trees.

Provision for mounting a ballistic recovery chute

Done. It can be mounted to the front of the firewall, behind the rear occupant.

Provision for cockpit heat

Done. Not a big deal.

Provision for wheel pants & retractable landing gear option

This has been rethought. First off, retracts don't give you much better performance than a well-faired gear set. They weigh a lot. They have a lot of moving parts. They make your insurance go up quite a bit. The new thinking is that we will eventually offer nose-gear retraction and the mains will stay fixed--exactly like the Rutan EZ's. Getting the nose gear out of the way will give a decent drag reduction without too much weight, and the insurance isn't bad because you won't kill your prop and engine if you do a wheels-up. Keep in mind that the LSA rules specifically DO NOT allow retractable gear.

A few words about trailers . . .

Getting a plane to fit in a trailer isn't very hard. Getting a plane like ours to fit in a SMALL trailer is really hard, at least if you don't want to do major disassembly after every flight.

In designing the airplane, we ran into a problem reconciling the desirable length of the tail vs. the width of the tail vs. any potential folding or removal mechanism in the wing roots (where the tail booms attach).

Here are your choices if you're faced with this dilemma:

1. You could make the tail booms removable. This was going to be both heavy and expensive unless we cut corners, and if we did we felt that safety would be out the window.

2. You could make the tail booms fold. Same problem as above.

3. You could make the tails booms shorter, thus making a smaller trailer possible. The problem here is that shorter booms means less lever arm, which then means you need a bigger tail SURFACE, which makes the tail too WIDE to fit in a trailer (don't you love aviation?).

4. Lastly, you can bite the bullet. You can make the tail booms fixed structures, thus saving weight and cost. You make them as short as possible, but without making the tail surface too wide. You do all of the above and then accept the fact that folks will need pretty long trailers.

As the plane is designed now, it will (barely) fit in a 24' x 102" racecar trailer. Make special note that the 102 inch trailers are less common than the 96 inch trailers, but they are out there. The problem is not the overall width of the trailer, it is the door clearance. If there is a flange around the door, you will probably have to notch it to get the wing stubs through the door.

We felt this was the best compromise possible. Racecar trailers are readily available on the used market without having to mortgage your house, and the racecar folks are usually very friendly and easy to work with. They are usually fairly nice trailers to boot.

And now for an opinion:

There is one key thing about trailerable planes that isn't widely acknowledged--most people never trailer their planes anywhere. They're just parked at the airport.

Yes, we all know someone who trailers their plane all over the place, but that person is in the tiny minority. Most folks want to be able to put our planes in a trailer so we don't have to pay rent on a hangar, not because we want to drive it around.

What you're really looking at is a portable hangar. Many airports will let you more-or-less permanently park your trailer "out behind the T hangars" for a tiny fee--like 10 or 20 dollars a month. Those of you from airports that have sailplanes have probably seen this very thing.

Folks who don't like this solution can get their friends to also buy a couple of Ions. Pop the wings off and keep three of them side by side in a regular hangar, splitting the hangar rent three ways. Just a suggestion.

Goals:

Take off roll of approximately 500 feet or less

Done. This only holds true for hard surface runways . . . grass has a higher rolling friction and will result in a longer take off roll.

Wings should be attachable / removable without tools by one person in 10 minutes or less

Done, although you do need a socket. We copied a common pin-and-fork mechanism that has been around on sailplanes for decades. Although you CAN do it by yourself, you SHOULDN'T. Why not? Because sooner or later you will drop one of your wings. They don't weigh much, but they are fairly big and awkward.

Build time of 150 hours or less

Not going to make it. It was a lofty goal, but it just isn't in the cards. We estimate that a person with reasonable skills can do it in 300-400 hours and a total beginner in about 400-500 hours. We have made arrangements with one of our contractors to provide classes on some of the skills you might not already have.

Climb rate of 1,250 FPM or greater with 100 HP engine

We have climbed the prototype as hard as 1,700 FPM. Weight and prop pitch are, of course, the two biggest variables. In a high/hot/humid/heavy condition it is reasonable to assume a climb only slightly in excess of 1,000 FPM whereas a cold/dry day with a climb pitched prop will climb like crazy.

These tables represent the results of the projections we got from our engineers. In the absence of major changes, the engineers warrant to us that these figures will be accurate within +/- 5%.

All figures are calculated at max gross weight of 1,320 pounds at sea level on an ISA day.

Design Goals

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