Pacific Scientific T555-8 Riser #2C Tensiometer Riser

The Pacific Scientific T555-8 is the OEM replacement Riser #2C for T5-2000 series cable tensiometers, used when measuring 5/32" and 3/16" aircraft control cables. It is the mid-size riser in the standard three-riser set that ships with most T5-2000 series instruments, and it is a critical precision component — not a generic hardware item. The riser establishes the exact cable contact geometry that the tensiometer's internal mechanism and calibration card are designed around. Without the correct riser installed, the instrument will not produce accurate tension readings, regardless of how well it has been calibrated. Mismatched or missing risers are a documented source of cable tension measurement error in aircraft maintenance, which is why the T5 service manual emphasizes riser selection as a mandatory step before every measurement. The T555-8 is manufactured by OPTI Manufacturing, the OEM producer of Pacific Scientific tensiometers, ensuring dimensional conformance with the original specification.

Why the Correct Riser Is Not Optional

The T5-2000 series tensiometer measures cable tension by deflecting the cable over an internal mechanism. The height and geometry of the riser block determines how much deflection occurs for a given cable diameter, which in turn determines what the dial reading means in terms of actual pounds of tension. The calibration card maps dial readings to actual tension values based on a specific riser geometry for each cable size. If the wrong riser is installed — or if no riser is installed — the deflection geometry is wrong, the calibration card mapping no longer applies, and the resulting tension reading is invalid. On primary and secondary flight control cables, an invalid tension reading can result in an improperly rigged control system. Always consult the calibration chart supplied with your tensiometer to confirm the correct riser for the cable size being measured before taking any reading.

Riser #2C — The Mid-Size Riser in the T5-2000 Series Set

• Riser designation: #2C
• Part number: T555-8
• Cable sizes: 5/32" and 3/16" aircraft control cables (and equivalent CWT British sizes on dual-calibration models)
• Position in the standard riser set: Mid-size — between Riser #1 (T555-2, small cables) and Riser #3 (T555-6, large cables)
• OEM manufacturer: OPTI Manufacturing Corp., Luquillo, Puerto Rico — dimensional conformance to original specification guaranteed
• Field-replaceable: Can be swapped in the field without instrument recalibration
• Compatible: All standard T5-2000 series multi-riser models — confirm with individual calibration chart

When to Replace the T555-8 Riser #2C

The T555-8 should be inspected regularly and replaced when any of the following conditions are present: visible wear, scoring, or deformation of the contact surfaces; corrosion or pitting that alters dimensional geometry; loss or misplacement in the field; or any incident (drop, impact) that may have altered the riser's dimensions. Because the riser's dimensional accuracy directly affects measurement accuracy, a visually damaged riser should never be used as a measurement aid regardless of how minor the damage appears. Replacement risers should always be OEM-sourced — OPTI Manufacturing is the only authorized producer of Pacific Scientific tensiometer risers, and dimensional substitutes from non-OEM sources cannot be assumed to meet the tolerances required for calibrated aviation measurement.

The Complete T5-2000 Series Standard Riser Set

• T555-2 — Riser #1: Used with 1/16", 3/32", 1/8" cables (small cable group)
• T555-8 — Riser #2C: Used with 5/32", 3/16" cables (mid-size cable group) ← this item
• T555-6 — Riser #3: Used with 7/32", 1/4" cables (large cable group)

Pacific Scientific T555-8 — Calibration Note

Replacing a riser does not require recalibration of the tensiometer instrument itself — the instrument's calibration is not affected by swapping risers. However, the correct riser must be used for each cable size measurement, as specified on the calibration chart. If your T5-2000 series tensiometer is due for recalibration regardless of riser condition, Pilot John International's ISO 17025-accredited calibration laboratory performs recalibration of Pacific Scientific T5 series tensiometers to original manufacturer specifications, issuing a fully traceable calibration certificate upon completion. Learn more about PJi's ISO 17025 Calibration Services →