In our ramp test, the jet that rolls furthest is usually the one whose wheels turn most freely, not the biggest or the lightest. Every jet and airliner in the aircraft series has the same landing gear: a long axle with a wheel at each end under the wings and a single nose wheel. So when you roll them down the same ramp, size and weight matter less than you might guess, and a wheel that rubs on its leg matters a lot. This guide shows you how to run the test fairly and what to look for.
You will need two or more aircraft with wheels, a ramp (a book propped on a stack of books works), a tape measure and a strip of tape for the start line.
Pick your test aircraft
All of these push along on their wheels to taxi, so all of them can run on a ramp.
| Build | Kind | Parts | Steps |
|---|---|---|---|
| F-16 Fighting Falcon | Fighter jet | 69 | 23 |
| Rafale | Fighter jet with canards | 67 | 22 |
| Concorde | Supersonic airliner | 66 | 22 |
| Boeing 747 Jumbo Jet | Jumbo jet | 86 | 29 |
| Airbus A380 | Double-deck airliner | 89 | 30 |
A good pair to start with is the Concorde and the 747: they are both airliners, but the 747 has about 20 more parts. If you only have time for one build, the F-16 is a level 2 model of about 40 minutes.
How the landing gear works
The main wheels hang from two L-beam legs, one on each side of the fuselage. A single long axle goes through both legs, with a small train wheel on each end. The wheels stop the axle sliding out sideways, and the legs stop the wheels sliding in. The whole axle turns with its wheels, inside the round holes of the legs.
The nose wheel is a 3-long axle through one leg, with the wheel on one side and a bush on the other. That is where friction most often hides: a bush pushed hard against the leg rubs on every turn.
How the shapes are built
While you build, look at how the wing shape comes from beam lengths. Wing beams get shorter towards the tip, and the faster they shrink, the more triangular the wing. The F-16 has a cropped delta wing; the Rafale, Gripen, Eurofighter, J-10 and Kfir add canards, little front wings built in their own step near the nose. The A380 is the only model with two full passenger decks, and the SR-71 and Su-27 have twin tail fins. Every wing is still slices pinned to slices, braced by short upright legs inside the fuselage: the same bracing that keeps all 40 aircraft rigid.
Run the ramp test
- Set up the ramp on a hard, flat floor and mark a start line near its top with tape.
- Line up the model's nose wheel on the start line and let go. Do not push.
- Measure from the bottom of the ramp to the nose wheel where the model stops.
- Do three runs for each model and write them down.
- Swap the order you test the models in, in case the ramp gets nudged.
Before you start, predict: will the heavier 747 roll further than the Concorde, less far or about the same?
Try the ramp lab first. Change the height, the ramp length and the drag of the floor, and see what moves the stopping point most.
Interactive: Ramp roll-out lab. Roll a car down a ramp onto the floor: change the ramp’s height and length and the drag numbers of the ramp and the floor, then predict how far it rolls. Five challenges: does a steeper ramp send it further, what does doubling the height do, and how to measure your floor’s drag number.
| Model | Run 1 (cm) | Run 2 (cm) | Run 3 (cm) | Middle value |
|---|---|---|---|---|
| Concorde | ||||
| Boeing 747 |
What the results mean
In the lab's simple model, a heavier car gets more pull down the slope but also more rubbing at its wheels, and those two grow together, so mass on its own hardly changes how far it rolls. That is why you may find the 747 and the Concorde end up close together.
Real models are not perfectly simple. If one runs clearly further, look at its wheels before you decide that size was the reason:
- Spin each wheel with a finger. Does one stop much sooner than the others?
- Is the nose-wheel bush pressed hard against its leg? Pull it out a hair and test again.
- Does the model curve? A rubbing wheel on one side turns it towards that side.
- Does it tip onto a wingtip? Check where it balances; a model that is very nose-heavy or tail-heavy can drag its nose or tail.
Change one thing at a time, run three more trials, and compare the middle values. That is a fair test, and it is how engineers find out which fix really helped.
Next steps
Try the same test with two fighter jets that differ only in wing shape, such as the F-16 and the Rafale, and see whether the canards make any difference on the floor. Then read how a steeper ramp changes the roll and repeat your test from a higher start.
Interactive: Check yourself. A few quick questions on the ideas in this guide, each with an explanation.
- How is the main landing gear of the jets and airliners built?
- In the simple ramp model, why might a heavy 747 and a light Concorde roll about the same distance?
- To make the test fair, which of these must you keep the same for every run?
- Your jet curves off to one side every run. What should you check first?
