Category: Blog

Yaks are another perennial favourite, and their typically wide-stance, robust-looking gear can actually hide developing problems if you don’t know what to check for.

Check gear leg symmetry carefully. Yaks’ wide gear stance means asymmetric flex or damage on one leg can be less visually obvious than on a narrower-stance model — a side-by-side comparison of both legs, ideally with the gear off the model, is worth doing rather than relying on a quick glance.

Tailwheel assembly deserves specific attention on tailwheel Yak configurations — this is a smaller, often-overlooked component that takes a surprising amount of load during taxi and on any less-than-perfectly-smooth landing, and a worn or loose tailwheel steering linkage is a common, easily-missed cause of ground handling problems.

If your Yak runs a petrol twin, the vibration and fastener-loosening points from Day 13 apply directly — a full fastener check across gear, engine mount, and cowl fixings is worth doing as standard pre-season practice.

Inspect any scale add-on details near the gear, such as scale gear doors or fairings if fitted — these are often lighter-duty items than the structural gear itself and can work loose or crack without it being obvious the underlying gear is fine.

Test-fit and function-check retracts if your Yak is retract-equipped, well before your first flight of the season rather than discovering an issue on the day — a full cycle test on the bench, checking clean, positive movement with no binding, catches most retract problems while they’re still a bench job rather than a field problem.

As with the Extra, a Yak’s typically demanding flying style means a proper seasonal check is time well spent rather than an optional extra.

Take a look at our Carbon Fibre Undercarriage for 80cc models – suits Yak and others. for a solid example of correctly sized gear.

The Extra family remains one of the most popular scale aerobatic subjects out there, and a proper pre-season check pays off given how hard these models tend to get flown.

Landing gear first. Extras see some of the hardest, most repeated landing loads of any common scale subject, thanks to their aerobatic flying style — check both legs for the stress signs covered in Day 4, paying particular attention to the mounting area, which takes the most repeated flex over a season of hard 3D and aerobatic landings.

Wheel pants, if fitted, are worth a specific check on Extras given how tightly they’re often fitted for scale accuracy — a season of vibration and hard landings can work pant mounting wire loose even when everything looked fine at the end of last season.

Engine mount and firewall, particularly on the larger petrol-powered 260/300 variants, take significant vibration over a season — a visual check for any hairline cracking around mounting bolts is worth two minutes before your first flight.

Control surface hinges and linkages on an Extra see more full-deflection cycling than most sport models, given how the type is typically flown — a full-range check by hand, feeling for any play or binding, catches wear before it becomes a control surface departing mid-manoeuvre.

If your Extra has sat for the winter, a full re-torque of every accessible fastener — gear, engine mount, control horns — is worth doing as standard practice rather than assuming everything’s still as tight as when you packed it away, particularly with a model that flies as demandingly as this one typically does.

A thorough pre-season check on an Extra usually takes under an hour, and given how hard these models are typically flown, it’s an hour well spent.

For a real-world example, have a look at our EXTRA 300 90 size nitro or electric Carbon Fibre Undercarriage.

Moving from glow to petrol (or the reverse) is about more than just the engine — it changes the whole weight and vibration profile of the model, and that has knock-on effects for landing gear that are easy to overlook.

Petrol engines are generally heavier for a given displacement than an equivalent glow engine, and that extra weight sits right up at the nose — which shifts the model’s all-up weight and often its centre of gravity, both of which affect how hard the gear works on every landing, not just take-off roll.

Vibration characteristics differ too. Petrol twins in particular can have a different vibration signature to a comparable glow four-stroke, and while that mostly affects things like fuel tank mounting and radio gear, it’s also a contributing factor to fastener loosening over time — including the bolts holding your landing gear on, which is one more reason the torque checks mentioned in Day 5 are worth doing as routine maintenance, not just at initial fitting.

If you’re converting an existing glow model to petrol, don’t assume the original landing gear rating still applies once you’ve added engine, ignition, and fuel system weight. It’s worth recalculating your new all-up weight and checking it against your gear’s rated range (see Day 1) rather than assuming the original gear specification still has headroom.

The reverse conversion (petrol to glow) is less commonly an issue, since you’re generally removing weight rather than adding it — but it’s still worth a sanity check against your gear’s original design weight, particularly if you’re also changing fuel tank size or battery specification as part of the conversion.

None of this means a conversion is complicated — it just means treating the gear as part of the weight-and-balance conversation, not a fixed item you carry over unchanged.

Our CRRC GF40i Kit engine. is a good reference point if you’re shopping around.

If you’re moving into petrol power for the first time, or upgrading an ageing points-based ignition, RCEXL systems are one of the most widely trusted names in the RC petrol world, and it’s worth understanding the basics before you buy.

What an ignition system actually does. Unlike glow engines, which rely on a heated glow plug element to sustain combustion, petrol engines need a proper spark, generated and timed electronically. The ignition module takes power from an onboard battery, generates the spark at the correct moment in the engine cycle, and does so reliably at whatever RPM range your engine runs through.

CDI vs other systems. RCEXL’s CDI (Capacitor Discharge Ignition) units are popular because they give a strong, consistent spark across a wide RPM range with minimal power draw, which matters when you’re running everything off a small onboard battery pack rather than a full-scale vehicle electrical system.

Single vs dual ignition. Single-cylinder engines need one ignition module; twin-cylinder engines need a matched pair, generally timed and wired together as a set rather than mixed from different batches — if you’re replacing one half of a twin setup, it’s worth replacing both to keep timing and spark characteristics matched.

Battery considerations. Ignition systems are sensitive to voltage — running one on a tired or marginal battery is a common (and entirely avoidable) cause of rough running or hard starting that gets wrongly blamed on the ignition unit itself. A dedicated, well-maintained ignition battery, checked before every flying session, solves more “engine problems” than people expect.

If you’re specifying a system for a new petrol build, matching the ignition to your engine’s exact cylinder count and displacement bracket is the main thing to get right — beyond that, installation is generally straightforward for anyone comfortable with basic RC wiring.

You can browse our RCEXL Safety Kill Switch 2.0 to see this in practice.

Not every fuselage matches a standard gear width exactly, and that’s more common than you’d think — even within a single “size class” of model, mounting widths vary between manufacturers and even between different production runs of the same kit.

The good news is that carbon fibre undercarriages are generally straightforward to adapt in width, provided you approach it methodically. Many two-part gear designs are specifically made this way — manufacturers intend for the centre section to be trimmed or a section removed, then the two halves bolted back together at a narrower span, which is a well-established and structurally sound method rather than a workaround.

A few practical points if you’re trimming gear to fit:

Mark your cut line carefully and double-check the measurement twice before cutting once — carbon fibre offcuts aren’t reusable if you get it wrong.

Use a fine-toothed blade suited to composite materials, and always cut with adequate dust extraction or outdoors with a mask — carbon fibre dust is an irritant you don’t want to breathe or get in your eyes.

Deburr and lightly seal any freshly cut edge, since a bare cut edge is more vulnerable to moisture ingress and fibre fraying at the exposed layers than the factory-finished parts of the leg.

Re-drill mounting holes rather than trying to reuse factory-positioned holes that no longer line up after trimming — it’s a five-minute job and avoids putting unnecessary stress on a hole that’s now in the wrong place relative to the new span.

If you’re at all unsure whether your specific gear is designed to be trimmed this way, check the product description or ask before cutting — some designs are genuinely not meant to be shortened, and attempting it risks compromising the structural integrity of the leg.

Our EXTRA 300 100CC Carbon Fibre undercarriage is a good illustration of the kind of fit and finish to look for.

Landing gear generally comes in two basic configurations — a single continuous leg spanning the full width of the model, or two separate legs each bolted individually to their own side of the fuselage. Both are common, and the right choice often comes down to your specific airframe rather than a universal “better” option.

One-piece (spring/bow style) gear flexes as a single unit, which can give a smoother, more even landing feel since load on one side is partially shared across to the other through the continuous leg. It’s a simple, proven design used on a huge range of sport and scale models, and there’s generally one fewer set of mounting points to maintain.

Two-piece gear mounts each leg independently, which is often the only practical option on wider fuselages or models where a single-span leg simply wouldn’t fit the available mounting area. It also means a heavy landing that stresses one leg doesn’t necessarily transmit that load across to the other side — which some flyers see as an advantage, and others see as losing the shared-load benefit of a one-piece design.

If you’re replacing gear on an existing model, the honest answer is: match whatever configuration the model was designed around, since the fuselage mounting points and internal structure are usually built around one style specifically. Converting from one-piece to two-piece (or vice versa) on an existing airframe is possible but generally means reinforcing or modifying the mounting area — not a straightforward swap.

If you’re scratch-building or heavily modifying, it’s worth deciding early, since it affects fuselage design at the mounting area rather than being a late-stage decision.

Take a look at our Extra 330 Carbon fibre undercarriage 30e for a solid example of correctly sized gear.

Grass strips are kinder to propellers than tarmac, but they’re not automatically kinder to landing gear — in some ways, quite the opposite.

Uneven ground concentrates shock loads unpredictably. A smooth tarmac landing spreads load evenly across a level surface. A grass strip with even minor undulation means one wheel can hit a slightly higher or lower point than the other on touchdown, putting an asymmetric load through the gear that a flat surface wouldn’t produce.

Longer or wetter grass adds drag exactly where you don’t want it — right at the wheel, right as the gear leg is already under load from touchdown. This is part of why wheel choice (see Day 7) matters as much as gear choice on grass strips specifically.

Rough or rutted ground rewards a slightly wider wheel and a slightly more generous gear stance if your model allows it — narrow, closely-spaced gear that’s fine on tarmac can feel noticeably twitchier on rough grass, with more load transmitted through each leg individually rather than shared smoothly.

A pre-flight walk of your usual strip is worth the two minutes it takes, especially early in the season after a wet winter — molehills, rabbit holes, and ruts that developed since your last visit are a common and entirely avoidable cause of hard, unexpected landing loads.

None of this means grass strips are bad for landing gear generally — most carbon fibre gear is more than capable of handling reasonable grass strip use for years. It just means the checks in Day 4 are worth doing slightly more often if grass is your regular home field, since the loading is genuinely less predictable than tarmac.

For a real-world example, have a look at our 1 Pair of Wheels with Plastic Hub for RC Airplane.

Landing gear isn’t meant to be perfectly rigid, and that surprises some flyers who assume “stiffer is always better.” In reality, a certain amount of controlled flex is doing useful work every time you land.

When your model touches down, the gear leg absorbs a portion of the vertical energy by flexing, rather than transmitting all of that shock straight into the fuselage mounting points. This is the same principle full-scale aircraft undercarriage legs use, just without the oleo struts and hydraulics — a well-designed carbon fibre leg uses the natural spring properties of the laminate itself as a simple, maintenance-free shock absorber.

The trouble comes when flex crosses from “designed-in” to “developing damage.” A small amount of consistent, symmetrical flex under load, with the leg returning fully to its original shape, is normal and expected. Flex that’s asymmetric between the two gear legs, flex that doesn’t fully recover, or flex accompanied by any audible creak or crack, are all signs the leg is being stressed beyond its intended range.

This is also why gear sizing matters so much (see Day 1) — a leg designed for a lighter model, fitted to a heavier one, will flex more than intended on every single landing, accelerating fatigue long before any single landing looks dramatic enough to worry about.

If you want a rough real-world check, watch a landing on video in slow motion occasionally, or have a friend watch from the side. A small, even flex and rebound on both legs is exactly what you want to see — anything that looks lopsided is worth a closer inspection on the ground.

Our Carbon undercarriage for 50 size – 90 size profile models. is a good reference point if you’re shopping around.

Wheel pants finish a model off beautifully, but they’re also one of the most common sources of frustration when fitting new landing gear, mostly because pant fitting is rarely as plug-and-play as the box suggests.

The core issue is tolerance stacking: your gear leg has a certain width and axle position, your wheel has a certain diameter and hub width, and your pant has a fixed internal cavity shape. Get any one of those slightly different from what the pant was designed around, and you’ll end up with rubbing, or a pant that sits at a slightly odd angle.

A few things that help:

Fit the gear and wheels first, pants last, and only trim the pant’s mounting slot once you can see exactly where the leg actually sits relative to the pant — resist the temptation to pre-drill mounting holes based on a diagram alone.

Leave a genuine air gap around the tyre, not just clearance when static. Tyres compress and the gear leg flexes rearward under load on landing, so a pant that just clears the wheel when the model is sitting still can make contact the moment you land.

Reinforce the pant mounting wire or bracket, since this is usually the first thing to fail — vibration loosens it long before the pant itself wears out. A drop of thread-lock and a periodic check goes a long way.

Accept that some trimming is normal. Even pants sold as a matched set for a specific gear rarely fit arrow-straight from the bag — a small amount of careful trimming with a sanding block is standard practice, not a sign you’ve bought the wrong part.

If you’re planning pants on a model that didn’t come with them designed in, it’s worth test-fitting before final paint — cutting a freshly painted pant to fit is a job nobody enjoys.

Our Wheel Spats is a good illustration of the kind of fit and finish to look for.

Fitting new gear is one of the more satisfying jobs on any model, and it’s genuinely straightforward if you take it in order.

1. Remove the old gear completely, including any old thread-lock residue on the bolts, and inspect the fuselage mounting points for damage before fitting anything new — there’s no point bolting fresh gear to a cracked or soft mounting rail.

2. Dry-fit before you commit. Offer the new gear up to the mounting points without any fasteners tightened, and check the leg sits square to the fuselage centreline and that the wheel axles will clear any cowl, wheel pant, or fuselage side when the wheels are fitted.

3. Use the correct grade of fastener, torqued to a sensible value by feel rather than gorilla-tightened — carbon fibre mounting plates can crack under excessive clamping force just as easily as they can crack from flight loads. If in doubt, a drop of thread-lock on a moderately tight bolt beats an over-tightened one.

4. Check axle alignment with the gear bolted down — sight along both wheels from directly behind the model to make sure they’re parallel to each other and to the fuselage. Toe-in or toe-out, even slight, will cause the model to pull on take-off roll.

5. Fit wheels and pants last, and spin each wheel by hand to check for free rotation with no rubbing against pants or fuselage before your first flight.

6. Do a firm hand-push test on each gear leg, simulating a moderate landing load, before you ever trust it to a real one. If anything flexes further than you’d expect or you hear any cracking sound, stop and re-check the fit.

Take your time on step 3 in particular — most gear failures we hear about trace back to fasteners rather than the gear itself.

Take a look at our Carbon Fibre undercarriage for 50e and 50 size nitro Narrow Fit YAK50e 50e for a solid example of correctly sized gear.