M-111 - Textron Aviation OEM Exhaust Gas Temperature Probe

M-111 – Textron Aviation OEM Exhaust Gas Temperature (EGT) Probe

Available now on the Airparts.aero Marketplace.

The M-111 is a genuine Textron Aviation (Cessna/Beechcraft) OEM, flight-critical Exhaust Gas Temperature (EGT) probe. This sensor is an indispensable component of the engine monitoring system, designed to provide the pilot with real-time temperature data from the engine's exhaust stream. Its primary function is to measure the temperature of the exhaust gases exiting a specific cylinder, providing crucial information for accurate fuel mixture leaning (finding peak EGT or operating lean/rich of peak) and for diagnosing potential engine health issues such as combustion problems or injector malfunctions.

Engineered for extreme reliability in the harsh exhaust environment, this probe is typically a Type K (Chromel-Alumel) thermocouple.1 It is constructed with a robust, high-temperature alloy sheath (often Inconel 600) protecting the thermocouple junction and mineral oxide insulation. The accuracy and rapid response of this probe are essential for efficient engine operation, fuel economy, and preventing engine damage caused by improper leaning or undetected combustion anomalies. As a genuine OEM part, it guarantees the correct fit, calibration, and materials required for integration with the aircraft's EGT indicating system.

Key Features

• Genuine Textron Aviation OEM Part: Ensures correct calibration, material specifications, and compatibility with the aircraft's EGT indication system. (Note: Often manufactured by specialists like Alcor under the OEM P/N).

• Provides Critical Exhaust Gas Temperature Data: Essential for precise fuel mixture leaning (peak EGT method) and engine health diagnostics.

• Type K Thermocouple (Typical): Utilizes industry-standard Chromel-Alumel thermocouple wires, known for their wide temperature range and good linearity.2

• High-Temperature Alloy Sheath: Features a durable Inconel 600 or similar superalloy outer sheath, providing exceptional resistance to the extreme temperatures (up to 1600°F / 870°C) and corrosive environment of exhaust gases.

• Mineral Oxide (MgO) Insulation: High-purity Magnesium Oxide powder insulates the thermocouple wires within the sheath, ensuring electrical isolation and protecting against vibration-induced shorts.

• Rapid Response Time: Engineered to quickly detect changes in exhaust gas temperature for accurate leaning and diagnostics.

Technical Specifications

• Part Number: M-111

• Component Type: Exhaust Gas Temperature (EGT) Probe / Sensor

• OEM Manufacturer: Textron Aviation (Likely manufactured by Alcor or similar under Textron specification).

• Sensor Type: Thermocouple, likely Type K (Chromel vs. Alumel).

• Sheath Material: High-Temperature Nickel-Based Alloy (e.g., Inconel 600).

• Insulation: Mineral Oxide (MgO).

• Temperature Range: Suitable for typical piston engine EGT range (e.g., 1000°F - 1650°F / 540°C - 900°C).

• Electrical Connection: Typically features standard screw terminals or ring terminals for connection to the EGT harness.3

• Mounting: Threaded boss for installation into exhaust manifold/riser (Thread size must be verified, often 1/4" NPT or specific clamp style).

Aircraft Compatibility

The M-111 EGT probe is specified for use on a vast range of Textron Aviation (Cessna and potentially Beechcraft) piston engine aircraft equipped with EGT indicating systems. Common applicable models include, but are not limited to:

• Cessna 152

• Cessna 172 Skyhawk

• Cessna 177 Cardinal

• Cessna 180, 182 Skylane

• Cessna 206 Stationair, 210 Centurion

• Beechcraft Bonanza, Baron (Check specific P/N applicability)

Crucial Note: The specific aircraft model, serial number, and engine type must be checked against the latest revision of the official Textron Aviation Illustrated Parts Catalog (IPC) or engine monitoring system documentation to ensure correct part number applicability. Installation location (specific cylinder) is also critical.

Applications

• Measures exhaust gas temperature for display on a single-cylinder or multi-cylinder EGT gauge/engine monitor.

• Primary sensor for fuel mixture leaning procedures (finding peak EGT, operating Lean of Peak or Rich of Peak).

• Engine diagnostics: Helps identify issues like fouled spark plugs, malfunctioning fuel injectors, or induction leaks by comparing EGT readings across cylinders.4

Why Choose M-111?

Choosing the genuine Textron M-111 (or the underlying manufacturer's equivalent specified by the OEM) is essential for accurate and reliable engine management. EGT readings are critical for safe and efficient leaning, preventing engine damage from excessively lean mixtures or detonation. Using a non-certified probe risks incorrect readings due to poor calibration, material impurities affecting thermocouple voltage output, slow response time, or premature failure in the harsh exhaust environment. A faulty EGT reading can lead to improper engine operation, increased fuel consumption, or even catastrophic engine damage.5 The genuine OEM part guarantees the certified accuracy and durability required for this flight-critical sensor.

The M-111 EGT probe operates based on the Seebeck effect, a thermoelectric phenomenon. It consists of two dissimilar conductors (for Type K: Chromel, an alloy of ~90% nickel & 10% chromium, and Alumel, an alloy of ~95% nickel, 2% manganese, 2% aluminum & 1% silicon) joined together at one end—the measuring junction located inside the probe tip exposed to the exhaust gas. The other ends are connected to the measuring instrument, forming the reference junction. When the measuring junction is heated by the exhaust gas, a temperature difference ($\Delta T$) exists between it and the reference junction. According to the Seebeck effect, this temperature difference generates a small, predictable voltage (electromotive force - EMF) across the thermocouple wires, typically measured in millivolts.6 For a Type K thermocouple, this voltage is approximately 41 microvolts per degree Celsius difference.7 The EGT instrument measures this millivoltage, compensates for the reference junction temperature, and converts the signal into a calibrated temperature reading (e.g., in °F or °C). The accuracy of this measurement is highly dependent on the purity of the Chromel and Alumel alloys and the integrity of the welded measuring junction, factors rigorously controlled in the OEM component.

Note: This is a flight-critical engine monitoring component. Its accuracy is crucial for safe engine operation. Probes must be installed in the correct location (typically 2-6 inches from the cylinder exhaust flange) and torqued to the specified value to prevent leaks and ensure proper heat transfer. The electrical connections must be clean and secure; contamination or loose connections can significantly affect the millivolt signal and lead to erroneous readings. Consult the aircraft or engine maintenance manual for specific installation and inspection procedures.

Documentation

No public-facing OEM or regulatory documentation was located for this specific part number during research (it may be an older or specific internal P/N). All technical data, installation procedures, and applicability must be sourced from the official Textron Aviation Illustrated Parts Catalog (IPC), engine maintenance manual, or the documentation provided with the installed EGT indicating system. Cross-reference to manufacturer P/Ns (like Alcor 86255) may be necessary.