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0550209-1 – Textron Aviation Cessna OEM Carburetor Air Temperature Probe Assembly
Available now on the Airparts.aero Marketplace.
Overview
The Textron Aviation 0550209-1 is a genuine OEM, flight-critical Carburetor Air Temperature (CAT) probe assembly for a wide range of Cessna single-engine aircraft equipped with carbureted engines. This is the primary sensor for the CAT indication system, providing the pilot with essential, real-time data about the temperature inside the carburetor venturi. Its most crucial function is to alert the pilot to conditions conducive to the formation of hazardous carburetor ice, which can cause significant engine power loss or complete engine failure.
This probe is a precision-engineered thermistor assembly housed within a durable, thermally conductive body designed for direct mounting into the carburetor air box. The thermistor's electrical resistance changes predictably with the measured air temperature. This variable resistance signal is transmitted to the cockpit CAT gauge. Critically, this sender and the corresponding OEM gauge are engineered and calibrated as a matched set. The accuracy of the pilot's temperature indication, especially within the critical icing range (often marked yellow on the gauge), depends entirely on the specific resistance curve of this genuine Textron sender.
Key Features
Genuine Textron Aviation OEM Part: The only part guaranteed to be precisely calibrated to the Textron/Cessna CAT gauge, ensuring accurate and reliable temperature readings.
Critical Carburetor Ice Detection: Provides the essential temperature data needed for pilots to anticipate and manage carburetor icing conditions by applying carburetor heat.
Engineered as a Matched System: The probe's specific resistance-temperature curve is precisely matched to the OEM gauge, a vital factor for instrument accuracy, especially in the icing awareness range.
High-Accuracy Thermistor: Utilizes a Negative Temperature Coefficient (NTC) thermistor for sensitive and repeatable temperature measurement within the carburetor.
Robust, Sealed Construction: Housed in a durable metal body and sealed against the engine environment to withstand vibration, temperature cycling, and exposure to fuel/air mixtures.
Technical Specifications
Part Number: 0550209-1
Component Type: Carburetor Air Temperature (CAT) Sender / Probe
OEM Manufacturer: Textron Aviation (Cessna)
Sensing Technology: Negative Temperature Coefficient (NTC) Thermistor
Body Material: Brass or Corrosion-Resistant Steel (CRES)
Thread Size: Specific to the carburetor air box mounting boss (verify with IPC).
Aircraft Compatibility
This CAT probe is the specified OEM part for a vast fleet of Cessna's most popular carbureted single-engine aircraft, including but not limited to:
Cessna: 150, 152, 172 (earlier models, e.g., F, G, H, K, L, M, N, P), 177 Cardinal (fixed gear), early 182 Skylane models.
Note: This is a flight-critical instrument sensor. The aircraft's specific Illustrated Parts Catalog (IPC) for a given serial number is the final and absolute authority for determining part applicability.
Applications
Carburetor Air Temperature Sensing: Measures the temperature of the fuel/air mixture inside the carburetor venturi, the area most prone to ice formation.
Carburetor Icing Awareness System: Provides the primary data input for the cockpit CAT gauge, alerting the pilot to potential icing conditions.
Why Choose 0550209-1?
Carburetor icing is an insidious threat that can affect carbureted engines even on warm, humid days. An accurate CAT gauge is a pilot's primary defense. The 0550209-1 is the only probe guaranteed to be calibrated to the Cessna gauge. Using a non-certified, automotive, or "will-fit" sender is extremely dangerous. Its resistance curve will differ, leading to inaccurate readings. A pilot might see a "safe" temperature on the gauge when ice is actively forming, or might apply carburetor heat unnecessarily based on a false low reading, reducing engine performance. For the critical, life-saving function of carburetor ice detection, there is no substitute for the genuine, system-matched Textron OEM sending unit.
The engineering principle that makes the 0550209-1 probe indispensable is its ability to detect the temperature drop caused by fuel vaporization and the Venturi effect. As air flows through the carburetor's narrowing venturi, its velocity increases and its pressure drops (Bernoulli's principle). Simultaneously, fuel is introduced and vaporizes. This phase change from liquid to gas absorbs a significant amount of heat from the surrounding air (latent heat of vaporization). The combined effect can cause the temperature within the carburetor throat to drop by as much as 60°F (33°C) below the outside air temperature. The 0550209-1 probe is precisely positioned to measure the temperature at this critical point, providing the earliest possible warning that the mixture temperature is approaching or has entered the range where impact ice or throttle ice can form, typically between +30°F and +70°F (-1°C and +21°C) OAT with sufficient humidity.
Note: The 0550209-1 is a flight-critical engine instrument sensor. Installation must be performed by a certified A&P/IA mechanic. The probe threads must typically be installed dry or with a specified conductive sealant (check manual) to ensure proper thermal transfer and grounding. The probe must be torqued to the value specified in the aircraft or engine maintenance manual. A post-installation engine ground run to verify correct indication on the CAT gauge is mandatory.
Documentation
No public-facing OEM specification sheet was located for this proprietary part number. All authoritative technical data, installation procedures, and testing criteria are contained within the official Textron Aviation Maintenance Manual and Illustrated Parts Catalog (IPC) for the applicable aircraft models.
