A motor does not usually fail without warning. It draws slightly more current for the same commanded thrust, week after week, until one day it does not recover. The warning was present for a month. Nobody was reading it.
An asymmetry of tooling
Commercial aviation has monitored flight data since the 1970s. Flight data monitoring is mature, mandated in many operations, and supported by an industry of tooling.
Below that tier, essentially none of it applies. The tools assume airline data volumes, airline formats and airline budgets. An operator with twenty unmanned aircraft generates telemetry at a far higher rate per flight than an airliner does, in formats that differ between airframe types, and it lands as log files in a folder that nobody opens unless something has already gone wrong.
So the data exists, the signal is in it, and the review does not happen.
Thresholds are the wrong instrument
The instinctive answer is alarms: alert when current exceeds a limit. This is the right idea applied at the wrong moment.
A threshold fires when a parameter reaches a value already known to be bad. By then the useful window has passed. What predicts failure is not the absolute value but the trend: the same motor, the same commanded thrust, the same air temperature, drawing three per cent more than it did a month ago. No alarm fires, because no limit has been crossed.
Trending requires normalisation, and normalisation requires knowing what the flight was doing. Current at hover is not comparable to current in a climb. That context is in the flight record, which is why data monitoring works far better when it is attached to the operational record rather than to a pile of logs.
Exceedances need an engineering definition
The other half is knowing what "too much" means. Most small operators set limits by observing what the fleet normally does and drawing a line around it, which encodes current behaviour rather than design intent. If the fleet has always been flown slightly hot, the limit ratifies it.
Exceedance limits should come from the design envelope, the same envelope the airframe was sized against. A structural load limit is a number that came out of an analysis, not a number derived from what has been survived so far.
The point is maintenance, not dashboards
Flight data monitoring earns its place when it changes a maintenance decision. A trend that predicts a component reaching its limit in roughly forty flight hours is only useful if it reaches whoever schedules maintenance, in time, with enough confidence to act on.
That means the useful output is not a chart. It is a component, a projected date and the evidence behind it, arriving where maintenance is already planned. A dashboard nobody opens is the same failure as a log file nobody reads, with better typography.