Predictive Maintenance Reference

This page is the technical reference for PlaneConnection’s predictive maintenance system. For a step-by-step guide on using these features, see Use Predictive Maintenance.

Alert Severity Levels

Predictive maintenance alerts use a five-level severity scale. Each level has a defined meaning, default notification behaviour, and recommended response.

Level	Color	Meaning	Default notification	Recommended response
Info	Blue	Parameter is within normal range but a notable data point was recorded.	In-app only	Note for awareness. No action required.
Watch	Yellow	Parameter is approaching a threshold or showing an early trend deviation.	In-app, email	Monitor at increased frequency. Review at next scheduled check.
Caution	Orange	Parameter has exceeded a Watch threshold or trend slope is statistically significant.	Email, push	Schedule an inspection within the next scheduled maintenance window.
Warning	Red	Parameter has exceeded a Caution threshold. Immediate maintenance attention warranted.	Email, SMS, push	Ground aircraft pending maintenance review unless cleared by DOM.
Critical	Dark red	Parameter has exceeded a Warning threshold or a safety-critical exceedance occurred.	Email, SMS, push	Ground aircraft immediately. Notify DOM and PIC.

Alert severity levels are advisory. Airworthiness decisions must be made by a qualified aviation maintenance technician (AMT) or Director of Maintenance in accordance with the aircraft’s approved maintenance program and applicable FARs.

Monitored Parameters

Turbine Engine Parameters

The following parameters are monitored for turbine (jet and turboprop) engines. Parameter names follow SAE ARP4102 conventions where applicable.

Parameter	Abbreviation	Unit	Description
Fan speed (N1)	N1	% RPM	Low-pressure compressor/fan rotational speed. Primary power setting.
Core speed (N2)	N2	% RPM	High-pressure compressor rotational speed.
Exhaust gas temperature	EGT	°C	Temperature at turbine exit. Primary thermal health indicator.
Inter-turbine temperature	ITT	°C	Temperature between turbine stages (turboprop engines).
Fuel flow	FF	lbs/hr or kg/hr	Fuel consumption rate. Correlates with power and efficiency.
Oil pressure	OIL PRESS	PSI	Engine oil system pressure.
Oil temperature	OIL TEMP	°C	Engine oil temperature. Elevated values indicate thermal stress.
Oil quantity	OIL QTY	quarts or litres	Oil consumption between services. Rising consumption indicates wear.
Vibration (N1/N2)	VIB	inches/sec or EU	Engine vibration level. Elevated levels indicate imbalance or bearing wear.
Torque (turboprop)	TRQ	ft·lb or %	Shaft output torque (turboprop engines).
Bleed air pressure	BL AIR	PSI	Compressor bleed air pressure for environmental and pneumatic systems.

Piston Engine Parameters

Parameter	Abbreviation	Unit	Description
Cylinder head temperature	CHT	°C	Temperature of cylinder heads. Key detonation and cooling indicator.
Exhaust gas temperature	EGT	°C	Exhaust temperature. Used for mixture management and trend analysis.
Oil pressure	OIL PRESS	PSI	Engine oil system pressure.
Oil temperature	OIL TEMP	°C	Engine oil temperature.
Manifold pressure	MAP	in. Hg	Induction manifold pressure. Power setting indicator.
RPM	RPM	RPM	Engine rotational speed.
Fuel flow	FF	GPH	Fuel consumption rate.

Airframe Parameters

Parameter	Description
Landing gear cycles	Cumulative extension/retraction cycles tracked for life-limited components.
Pressurisation cycles	Cumulative pressurisation cycles for fatigue tracking.
Flight hours	Total airframe hours since new and since last major inspection.
Fuel imbalance	Left/right tank imbalance exceeding configured threshold.
Hydraulic pressure	System hydraulic pressure on equipped aircraft.

Trend Analysis Methodology

PlaneConnection’s trend analysis uses two complementary statistical methods to detect parameter degradation. Both methods run on each parameter independently.

Linear Regression

Linear regression fits a straight line through the most recent N data points (configurable window, default: 30 flight legs) and computes the slope. A positive slope on a rising-bad parameter (e.g., EGT) indicates a degrading trend even if no individual reading has exceeded a threshold.

Slope magnitude (EGT example)	Classification	Recommended action
< 0.5 °C/flight hour	Stable	Normal monitoring
0.5–1.5 °C/flight hour	Watch	Increase monitoring cadence
1.5–3.0 °C/flight hour	Caution	Schedule inspection
> 3.0 °C/flight hour	Warning	Immediate review

Slope thresholds are parameter-specific and configurable. Default values are based on typical fleet experience for common aircraft types.

Exponential Smoothing

Exponential smoothing applies a weighted average where recent readings have more influence than older readings. The smoothing factor α (alpha) controls the decay rate: higher α means faster response to recent changes. PlaneConnection uses a default α of 0.2 for most parameters, meaning approximately the last 5 readings contribute meaningfully to the smoothed value. For highly volatile parameters (vibration), α defaults to 0.3. The smoothed value is compared against threshold bands to determine alert level. Exponential smoothing is less sensitive to single-point spikes than raw thresholds but more responsive to sustained trends than long-window linear regression.

Combined Alert Generation

An alert is generated when either the regression slope or the smoothed value indicates a threshold exceedance. The higher-severity result takes precedence. This dual-method approach reduces both false positives (single outlier spikes) and false negatives (slow degradation that stays below instantaneous thresholds).

Threshold Configuration Options

Each monitored parameter on each aircraft can be configured independently. Threshold settings are found under **Ops > Predictive Maintenance > [Aircraft]

Configure Thresholds**.

Setting	Type	Default	Description
Alert direction	Rising/Falling/Both	Parameter-specific	Whether the alert fires when values rise, fall, or deviate in either direction.
Watch threshold	Numeric	90% of Caution	Value at which a Watch alert is generated.
Caution threshold	Numeric	Per aircraft type	Value at which a Caution alert is generated.
Warning threshold	Numeric	Per aircraft type	Value at which a Warning alert is generated.
Critical threshold	Numeric	Per aircraft type	Value at which a Critical alert is generated.
Regression window	Integer (legs)	30	Number of flight legs used for slope calculation.
Smoothing factor (α)	0.0–1.0	0.2–0.3	Exponential smoothing decay rate. Higher = more responsive to recent data.
Consecutive exceedances	Integer	1	Number of consecutive readings above threshold before alerting. Reduces noise.
Baseline source	Enum	Aircraft history	Comparison baseline: aircraft-specific history, fleet average, or manufacturer limits.
Suppress below n legs	Integer	10	Do not alert until this many legs have been recorded (avoids false alerts on new aircraft).

Start with the default thresholds and tighten them over time as you accumulate baseline data for each aircraft. The default thresholds are conservative and may generate Watch-level alerts on healthy aircraft during the first few months of use.

Data Sources

Predictive maintenance parameters are populated from the following data sources:

Source	Parameters populated	Update frequency
ACARS / digital OOOI data	Flight legs, departure/arrival times	Per flight event
EFB data import (CSV/JSON)	Engine parameters per leg (N1, N2, EGT, FF, oil)	Manual or automated upload
FOQA data import	Full parameter set at recording frequency	Per flight (after download)
Manual entry (maintenance log)	Oil quantity, maintenance actions, component replacements	Per maintenance event
Sensor integrations (API)	Real-time or near-real-time parameter streams	Per configured interval

FOQA data integration requires the Use FOQA feature to be enabled and data to be uploaded per the Use FOQA guide. Manual parameter entry is always available as a fallback for operators without automated data sources.

Use Predictive Maintenance

Step-by-step guide for using the predictive maintenance dashboard.

Use Fleet Health

Fleet-wide health overview combining predictive alerts and due items.

Use FOQA

Flight Operational Quality Assurance data that feeds engine trend monitoring.

Track Due Items

Schedule-based maintenance tracking alongside condition-based predictive alerts.

SMS Reference

SmartScore

Operations Reference

FBO Reference

Maintenance Reference

Operational Reports

Portal Reference

Platform Reference

API Reference

Alert Severity Levels

Monitored Parameters

Turbine Engine Parameters

Piston Engine Parameters

Airframe Parameters

Trend Analysis Methodology

Linear Regression

Exponential Smoothing

Combined Alert Generation

Threshold Configuration Options

Data Sources

Use Predictive Maintenance

Use Fleet Health

Use FOQA

Track Due Items

​Alert Severity Levels

​Monitored Parameters

​Turbine Engine Parameters

​Piston Engine Parameters

​Airframe Parameters

​Trend Analysis Methodology

​Linear Regression

​Exponential Smoothing

​Combined Alert Generation

​Threshold Configuration Options

​Data Sources

​Related

Use Predictive Maintenance

Use Fleet Health

Use FOQA

Track Due Items

Alert Severity Levels

Monitored Parameters

Turbine Engine Parameters

Piston Engine Parameters

Airframe Parameters

Trend Analysis Methodology

Linear Regression

Exponential Smoothing

Combined Alert Generation

Threshold Configuration Options

Data Sources

Related