S2550-12 - Textron Aviation Tachometer Shaft Assembly

S2550-12 – Textron Aviation OEM Tachometer Shaft Assembly

Available now on the Airparts.aero Marketplace.

Overview

The Textron Aviation S2550-12 is a genuine OEM mechanical tachometer shaft and casing assembly, a flight-critical instrument component engineered specifically for the Cessna 150 and 152 series of aircraft. This precision-manufactured assembly provides the direct mechanical link between the engine's accessory case and the analog tachometer in the instrument panel. It is designed to accurately and smoothly transmit the engine's rotational speed, providing the pilot with the essential RPM data required for all phases of flight, from engine run-up to cruise power management.

Key Features

• Low-Friction Operation: The flexible outer casing is lined with a specialized low-friction material. This allows the inner rotating core to spin freely with minimal drag, which is essential for preventing the tachometer needle from oscillating ("wavering") and ensuring an accurate, steady RPM indication.
• High-Strength Flexible Core: The inner, rotating shaft is constructed from multiple layers of high-tensile strength steel wire, contra-wound for high torque transmission capability and excellent resistance to kinking or breaking under torsional load.
• Durable Outer Casing: The protective outer casing is built to withstand the harsh firewall-forward environment, resisting heat, abrasion, and contamination from engine fluids, while remaining flexible enough for proper routing from the engine to the instrument panel.
• Precision End Fittings: Equipped with precisely machined and staked B-nut fittings on both ends, ensuring a secure, vibration-proof connection to both the engine's tachometer drive port and the rear of the cockpit instrument.
• Genuine Textron OEM Part: As a genuine factory component, it guarantees the correct length, end fitting design, and performance characteristics required for a certified, airworthy installation on specified Cessna models.

Technical Specifications

• Part Number: S2550-12
• Component Type: Mechanical Tachometer Shaft and Casing Assembly
• Inner Core Material: Multi-Layer, Contra-Wound Steel Wire
• Outer Casing Material: Protective Casing with Low-Friction Inner Liner
• Overall Length: 34.75 inches
• End Fittings: Standard AN-style threaded B-nuts.
• Certification: FAA Production Approval

Aircraft Compatibility

The S2550-12 is the specified OEM tachometer cable assembly for some of the most popular training aircraft ever produced. It is imperative to consult the specific aircraft's Illustrated Parts Catalog (IPC) for final verification.

• Primary Aircraft Models:
  • Cessna 150L, 150M
  • Cessna 152

Applications

The S2550-12 is a critical component of the primary flight instrumentation system:

• Engine RPM Indication: Its sole purpose is to mechanically drive the analog tachometer, providing the pilot with a direct, real-time indication of engine speed. This is essential for all power management tasks.
• System Maintenance & Repair: The primary component to replace when troubleshooting an erratic, wildly swinging, or inoperative mechanical tachometer.
• Preventative Maintenance: Flexible drive cables are wear items. They are often replaced after a certain number of years or hours to prevent failure from internal friction or fatigue, which would result in a loss of engine RPM information in flight.

Why Choose S2550-12?

An accurate and steady tachometer reading is crucial for safe and efficient engine operation, especially in a training environment where students are learning power settings. A faulty tach cable can provide misleading information or fail entirely. Using a genuine Textron Aviation S2550-12 OEM assembly ensures you are installing a component with the correct length, high-quality low-friction liner, and durable core required by the aircraft manufacturer. For a primary flight instrument, the reliability and accuracy afforded by a genuine OEM part are paramount.

Order Your S2550-12 Tachometer Cable Assembly Now

Ensure your primary engine instrumentation is accurate and reliable with a genuine Textron Aviation component. Visit Airparts.aero to order your S2550-12 tachometer cable assembly today.

The S2550-12 operates on the principle of a flexible drive shaft, a technology perfected for transmitting rotary motion over a curved path. The outer casing is held stationary, anchored to the engine's accessory case and the instrument panel. The inner core is free to rotate within the casing's low-friction liner. One end of the core has a keyed tip that engages with the rotating tachometer drive gear on the engine. The other end has a matching keyed tip that engages with the input of the analog tachometer gauge. As the engine spins, it spins the inner core at a 1:1 ratio, and this rotation is transmitted directly to the gauge's mechanism, which then displays the RPM. The quality of the casing's liner is the most critical factor in the cable's performance, as any friction or binding will cause the core to "wind-up" and release, resulting in the characteristic "swinging" needle of a failing tach cable.

Note: This is a primary flight instrument component. Installation must be performed by a certified A&P mechanic. The cable must be routed carefully to avoid sharp bends that exceed the minimum bend radius, as this will cause premature wear and failure. The end fittings should be tightened to the specified torque and properly secured.