Filing in this field is heavily concentrated: the leading assignee alone accounts for 213 of the 367 records in scope, and the five largest filers together hold 85.3% of all records. That leaves a long tail of 51 ranked companies with only single-digit or single filings each. Anyone doing freedom-to-operate work should focus first on the leader’s portfolio, since it covers the large majority of the mechanical and wear-sensing claim space.

Filings peaked in 2021 at 51 records and had fallen to 14 by 2024, a 73% drop over that three-year window. That is the most recent period that can be read as a complete trend, because publication lags filing by roughly 18 months, so 2025 and 2026 figures will keep rising as more records publish. Treat the recent apparent slowdown as partly a data artifact rather than a confirmed pullback in R&D activity.

The overwhelming majority of records, 82.6%, sit in IPC class F16D (clutches and brakes), covering disc-stack architecture, torque tubes and wear measurement. Aircraft-specific classification B64C appears in 21.3% of records, and the underlying composite material chemistry, classified under C04B (ceramics and refractories), appears in 12.8%. Because a single record can carry multiple classes, these figures do not need to sum to 100%, and they show that mechanical system claims outnumber pure materials claims in this corpus.