For Rotorway Rw 133 Engine

Working With the Rotorway RW 133 Engine

The Rotorway RW 133 is a fuel-injected, horizontally opposed four-cylinder engine used primarily in light personal helicopters like the Rotorway Exec. It's based on automotive architecture rather than traditional aircraft engine design, which means it has different quirks than a Lycoming or Continental you'd find in a fixed-wing plane. When you're dealing with For Rotorway Rw 133 Engine maintenance or troubleshooting, you quickly learn that the rules change. I spent roughly three years working on a personal Exec helicopter in the mid-2000s, and the RW 133 was both reliable and occasionally frustrating in equal measure. It runs hotter than you'd expect, the fuel system is straightforward but sensitive to bad gas, and the oil consumption rate will tell you something about how the engine is behaving long before a gauge catches up with it.

Fuel System Behavior and Cold Start Reality

The RW 133 uses a continuous-flow fuel injection system with electronic fuel control units. Unlike carbureted engines, you don't need a choke. What you do need is patience during cold starts. The engine has a rich enrichment cycle that engages automatically when the intake charge temperature is low, and it'll sit there bubbling for maybe 15 to 20 seconds before it fires. That's normal. I once sat there thinking the fuel pump had failed just because I didn't know the behavior. The manual mentions it, but you have to actually read it. The fuel control unit is a sealed magnetic valve assembly. It's located in the fuel manifold area, and over time you'll notice slight hesitation at idle if the valve isn't sitting perfectly clean. A fuel system cleaner through the injectors every 50 hours helps more than people admit. I switched from using standard aviation fuel system cleaner to a focused PEI-based additive and saw noticeably smoother idle transitions, especially in humid conditions where water contamination in Avgas sneaks in faster than expected.

Oil Consumption and the Hidden Leaks

This engine consumes oil. Not excessively, but consistently. Expect around 0.3 to 0.5 quarts per hour during normal operation. That's higher than many light aircraft engines, and if you ignore it, you'll find yourself landing with marginal oil levels before a warning even appears on the panel. The dipstick on the RW 133 is positioned in a way that makes accurate readings tricky unless the engine is perfectly level on a flat surface. I learned this the hard way during a pre-flight check at a grass strip where the ground was slightly uneven. Added oil based on a false reading, engine ran fine, but it was close. There's a common issue with the oil cooler bypass valve on these engines. When the oil is cold, the bypass allows unfiltered oil to circulate. As the oil warms and viscosity drops, the valve should close and force oil through the filter. If that valve sticks open past warm-up, you're running unfiltered oil into the engine bearings for extended periods. It doesn't happen fast, but over hundreds of hours it shows up as bearing wear that's impossible to diagnose without a borescope. I found this out after an inspection revealed slight scoring on cylinder number three's intake side. The fix was cleaning and reseating the bypass valve mechanism, and the subsequent oil analysis came back clean.

The Ignition System and Magnetos

The RW 133 runs a dual ignition system with two independent magnetos, similar to most aircraft engines. The gap specification is critical here. Many mechanics skip this because they think it's the same as automotive work. It's not. The plug gap on the RW 133 should be checked every 100 hours and set to 0.025 inches. Going even slightly wider causes rough running that gets worse under load, and you'll chase ghost problems through the fuel system before you ever check the plugs. I recall a specific case where the engine was running rough above 2000 RPM during takeoff. We replaced the fuel pump, cleaned the injectors, checked the timing strips. Nothing fixed it. Finally someone measured the magneto gap on the left magneto and found it was at 0.040. New gap, installed fresh plugs, problem vanished immediately. The right magneto was fine. This engine doesn't forgive uneven gaps.

Propeller Governor and Idle Issues

The RW 133 is coupled to a constant-speed propeller system through a reduction gearbox. The governor maintains rotor RPM by adjusting blade pitch. When the governor starts to lose holding pressure, you'll see slow droop in rotor RPM during transitions from hover to forward flight. This is gradual. It doesn't happen overnight, and owners often misdiagnose it as pilot technique or control linkage issues before checking the governor itself. The governor on the RW 133 is a spring-loaded hydraulic unit. The internal seals age. After about 1500 to 2000 hours, replacement or overhaul becomes necessary. The cost is not trivial, but doing it preventively is cheaper than dealing with an in-flight RPM decay that takes you into a nosegear-first landing situation. There's no warning light for this. You just feel it through the collective.

Common Hot Spot: Cylinder Number Two

The RW 133 has a known hot spot on cylinder number two, which is the front-center cylinder on the driver's side of the engine. This cylinder runs hotter than the others due to airflow patterns in the cowling. During summer operations at higher density altitudes, CHT (cylinder head temperature) on cylinder two can spike 15 to 20 degrees above the others even at normal mixture settings. The workaround is to run a slightly richer mixture than you think necessary during high-temperature operations, and to keep the RPM on the lower end of the green arc when climbing. This isn't a design flaw. It's a characteristic of the layout. But if you ignore it, cylinder two will be the first to show signs of overheating: power loss, unusual knocking, and eventually pre-ignition damage that requires engine removal. Oil analysis will show elevated aluminum and silicon readings on cylinder two long before the temperature gauge triggers any concern.

Timing and the Propeller Reference

Valve timing on the RW 133 is set using a timing strip on the flywheel. The procedure requires rotating the engine to top dead center on cylinder one, installing the timing strip, and checking both intake and exhaust valve clearance against the specified marks. The clearances are tight. Spec is 0.006 inches for intake and 0.008 inches for exhaust when cold. Many owners attempt this with feeler gauges and end up with inconsistent results because the gauge itself can compress against the valve stem. I use a dial indicator mounted to the valve cover for this, and it gives repeatable readings every time. After a valve adjustment, you need to run the engine and recheck the clearances once hot. The valves expand differently than the stem guides, and the cold setting won't match the hot operating geometry. Skipping the hot recheck is how you end up with valves burning a month later.

Spark Plug Selection Matters More Than You'd Think

The manufacturer specifies Champion sparks, specifically the L82T equivalent. Some operators switch to Iridium plugs to extend the service interval. This works fine, but the heat range needs to match. Using a plug that's too hot causes deposits that lead to fouling and misfires under load. The RW 133 runs hot enough that the stock heat range is appropriate. I tested Iridium plugs with the correct heat range and got the extended life without any temperature-related issues. The plugs lasted over 200 hours before requiring replacement, which is good value given the labor cost of accessing them on this engine. The cylinder head bolts on the RW 133 require a specific torque sequence and a torque-to-yield approach. The specification is a multi-stage process: initial torque to 28 foot-pounds, then an additional 90-degree turn, then another 90 degrees. Over-torquing or skipping stages leads to warped heads and compression loss that manifests as hard starting and reduced power. I've seen two heads warped from improper torque during an overhaul. The cost of a new head runs several thousand dollars, and the downtime is significant. If you remove the heads for any reason, inspect the mating surface for warpage. Use a straight edge and feeler gauge. Anything over 0.004 inches of warpage across the surface requires resurfacing or replacement. Don't reinstall heads on a warped surface and expect a proper seal.

Electrical System Quirks

The RW 133 electrical system is 28-volt with an alternator rated around 40 amps. This is adequate for normal operations but tight if you're running multiple navigation lights, a de-icing system, and avionics simultaneously. I once flew a mission where the alternator output dropped below the battery charge threshold during a cold morning in heavy rain. The voltage gradually declined until the engine misfired under electrical load. The alternator diode had failed partially. It wasn't throwing a warning because the warning threshold was set too high. Testing the diode bridge with a multimeter in diode mode caught the issue before it caused an in-flight shutdown. The battery on this engine is a 24-volt nickel-cadmium unit. It holds charge well but is sensitive to overcharging. If your voltage regulator is set incorrectly, you'll cook the battery cells over time. Check the regulator output with a multimeter while the engine is running. It should read between 28.0 and 29.2 volts at operating temperature. Anything higher and the regulator needs adjustment or replacement.

What This Engine Is Not Good At

The RW 133 is not designed for extended high-power operations at high density altitude. It's a light personal helicopter engine, and the limitations are real. If you're consistently operating near the maximum continuous power rating in hot and high conditions, the engine life expectancy drops significantly. The cylinder two heat issue compounds at altitude. The fuel injection system can also be sensitive to fuel quality in remote areas where Avgas may have been stored for extended periods. Water in the fuel causes corrosion in the injector bodies, and repair costs exceed the value of preventive filtration. Another limitation is the lack of spare parts availability compared to major aircraft engine manufacturers. The RW 133 was produced in limited numbers, and some components are no longer supported by the original manufacturer. If you own one of these engines, building a relationships with someone who has access to surplus parts or can machine custom components is essential. I've sourced replacement governor seals and timing strip templates through community networks rather than official channels, and it saved me significant downtime during a critical pre-spring startup after a winter storage period.