After 40 years turning wrenches, here's what I always find inside a 5-year-sit Cessna.
Forty years of A&P work. The last twenty have been almost entirely bad-condition GA — airplanes that have been sitting in hangars, tied down in fields, or parked in backyards while the owners waited for the right moment to deal with them. I've worked on a lot of five-year-sit Cessnas. At this point I know exactly what I'm going to find before I open the cowl. This list is for owners who want an honest read before they commit to an annual — or before they decide the annual doesn't make financial sense.
I'm going to talk mostly about 172s and 182s because that's the majority of what comes through, but most of this applies to any high-wing single that's been sitting.
The spar carry-through: where I look first
On a Cessna high-wing, the center-section spar carry-through runs under the cabin floor. It's the structural backbone of the entire airplane, and it's the first thing I inspect on any long-sit aircraft because it's the most consequential finding if something's wrong.
Water gets in through deteriorated door seals, cracked windshield bonds, and leaky inspection covers. It sits in the lowest spot it can find — which is right there on top of the carry-through. Five years of that, especially in a humid climate, and you'll see surface rust at minimum. Surface rust I can treat and coat. If it's gone deeper — if the metal is pitting or the flanges have started to separate — that becomes a major structural repair or a ferry permit situation. I've seen carry-through repairs run anywhere from $2,000 for minor treatment to $15,000+ for heavy corrosion work. On a Cessna 172 worth $40,000, that math changes things.
The hoses — every single one of them
Rubber doesn't last. On a five-year-sit airplane, I budget to replace all of it as a matter of course, because the ones that look okay on the outside are often the ones that crack on the first engine run.
The ones I always find failed or about to fail:
- Fuel selector outlet hose. It's a rubber elbow under the floor, right at the fuel selector valve. It hardens, micro-cracks, and weeps fuel the first time you pressurize the system. I've seen these put fuel in the bilge on the very first ground run.
- Oil breather tube. On a sit airplane this often collapses from the inside — age-hardening plus occasional mouse nesting. A collapsed breather causes crankcase pressure to build up and find somewhere else to go. Usually it finds the oil filler or a seal.
- Primer lines. The aluminum AN fittings at the primer are fine, but the short rubber sections at the cylinder primers harden and check-valves fail. You get a primer that won't hold or weeps raw fuel into the intake.
A full hose replacement on a 172 or 182 — fuel, oil, primer, brake — usually runs $400 to $800 in parts. Add 4-6 hours of labor. Not catastrophic, but it's not on anyone's "quick annual" estimate either.
The brakes
Brake caliper pistons seize. Bleeder screws seize (and snap when you try to turn them). Brake discs get a layer of surface rust that won't come off with the first few applications. This is all predictable and all fixable, but it takes time and parts.
On a five-year-sit I assume both caliper piston seals are done and budget for a rebuild on both sides. If the discs are at minimum thickness — which they often are on older airframes — add those too. I'm typically looking at $600 to $1,200 for a full brake overhaul on a single, including discs. That number goes up if the master cylinders need work too.
The magnetos and the impulse couplings
Impulse coupling springs fatigue even without running hours just from sitting. On a cold start after a long sit, a weak impulse coupling gives you a hard start and rough initial idle, which owners often attribute to bad cylinders. Sometimes it is the cylinders. But before I pull a jug, I check the magnetos. Impulse coupling replacement is cheap relative to cylinder work — $200 to $400 each side — and it eliminates the variable before you go further.
I also inspect the points and condenser (if it still has them), and I check for corrosion at the distributor block. Moisture in the magneto body isn't uncommon on a sit airplane, and that leads to tracking and misfires.
The cylinders
Here's what I can predict without even pulling a borescope: on a five-year-sit airplane in a humid climate that has been sitting on its own oil, you will have compression numbers in the 60s to low 70s across the board. The top compression rings develop a varnish coat from sitting oil, the ring grooves get sticky, and the cylinders don't seal the way they did when the airplane was flying 100 hours a year.
What I find under the borescope: rust on the cylinder walls is the real question. Light surface rust often polishes off with a few ground runs. Moderate pitting — you can feel the roughness with the scope probe — typically means you're replacing that cylinder. On a Continental O-300 or O-470, cylinders run $800 to $1,500 new per jug. On a Lycoming O-320 or O-360, similar range. Add 3-5 hours of labor per cylinder for R&R.
In a best case, I do a compression run, get 60-something across all jugs, do a few ground runs to clear the rings, recheck at 65-70+, and we're okay. In a worst case on a humid-state outdoor tie-down, I'm replacing two or three cylinders. I've done both on five-year-sit Cessnas.
The other items I always check
- Baggage door threshold corrosion. Water traps along the baggage door frame on 172s and 182s. The paint blisters first, then the skin. If it's blistering, I probe it. Light corrosion gets treated; anything structural is a sheet metal job.
- Control cable fraying. Cables that sit don't get lubricated at the fairleads, and the outer strands fray at wear points. I check every cable run for broken strands.
- Fuel tank sealant. On bladder-tank aircraft, the rubber can harden and crack. On wet-wing aircraft, ProSeal degrades over long sits — particularly at the drain fitting areas.
What does all this actually cost?
When someone hands me a five-year-sit Cessna 172 and says "what will it cost to annual?" I give them a realistic range: $5,000 to $15,000 before any major structural findings. Here's the breakdown I work from:
- Annual inspection labor (including all the above inspections): $800–$1,200
- Hose replacement: $600–$1,000
- Brake overhaul: $600–$1,200
- Magneto service or replacement: $400–$800
- Fuel selector rebuild: $200–$500
- Minor corrosion treatment: $400–$1,500
- Cylinder work (if needed): $800–$1,500 per jug
If I find carry-through corrosion that needs real structural work, or multiple jugs, or fuel tank sealant issues, that floor goes up fast. The top of the range on a bad airplane isn't theoretical — bills like that run north of $20,000 on a rough five-year-sit single before anyone touches paint or avionics.
What this means if you're trying to decide what to do
If you own a five-year-sit Cessna and you're thinking about putting it back in the air, get an honest pre-buy inspection from a shop that will give you the real list — not just the items that will fail the annual, but the full condition picture including the things that are legal to leave but won't be for long. Thomas has a guide that walks through the math on annualing up versus selling as-is that's worth reading before you write any checks.
If the inspection turns up structural corrosion or multiple cylinder replacements, the airplane can still be sold — it's not worthless. Cash4Planes buys airplanes with known issues. The offer accounts for the condition honestly, but you're not staring down a $12,000 shop bill on an airplane that may only be worth $40,000 afterward. And you're not waiting six months for a buyer who gets spooked at pre-buy.
If you're wondering what a flyable 172 or 182 is actually worth in today's market — before and after the sit-time adjustment — Thomas's Cessna market guide has real comp ranges.