H384, H484 & H598 Series Airborne Engine Monitors

A vital component of condition-based maintenance, our health and usage monitoring systems monitor critical engine parameters to reduce operating and maintenance costs.






A vital component of condition-based maintenance, Howell’s health and usage monitoring systems help flight crews:

  • Troubleshoot problems by isolating abnormal performance
  • Reduce maintenance cost and system damage through early diagnosis
  • Reduce parts replacement
  • Improve maintenance scheduling and logistic support
  • Improve incident or event analysis
  • Eliminate errors in data recording and analysis
  • Establish critical engine condition and trend monitoring for enhanced performance

Parameters include:

  • Engine Temperatures
  • Outside Air Temperature
  • Pressure Altitude
  • Airspeed
  • Engine Speeds
  • Fuel Flow
  • Bleed Valve Position
  • Torques
  • Pressures

Data Reduction

Our monitors retrieve and process data in several ways:

  • Monitors display data for a quick check of parameter values, or data can be downloaded to a computer for more in-depth review and analysis.
  • User-friendly software prints a report, formats the data into useful graphic presentations or transfers it to other computers. The data can be stored to maintain historical records.
  • Our patented Referred Engine Diagnostic Data (REDD)®1 software package provides detailed analysis and diagnosis of processed data. REDD® software quickly determines actual engine condition by calculating and displaying variances between an ideal engine and the monitored engine.


Trend data can be recorded manually or automatically during flight. The monitor records all relevant parameters along with the date and time. The data can be formatted for use with an engine manufacturer’s approved software or with Howell’s own patented trend software programs.


Monitors detect an exceedance and record the time of the event, its duration, peak value, values of related parameters, and if applicable, the maintenance level required based on severity. Monitors can also recall related parameter values leading up to the event from a buffer. These values are stored in memory and assist in post flight analysis of the exceedance. An output signal to a cockpit advisory or warning panel is also available.


Monitors record profile data by two methods: Timed Recording Mode or Profile All Mode.

  • The Timed Recording Mode collects data at fixed time intervals set by the operator.
  • The Profile All Mode collects transient data, including start and shutdown data at a preset rate. All other operation data is recorded when the engine stabilizes within a new “operational band.” This data compression technique minimizes the amount of data stored, thus maximizing operational time monitored.


  • Date and Time
  • Aircraft Number
  • Engine Number
  • Engine Starts
  • Engine Hours
  • Engine Cycle Counting
  • Hot Section Exposure
  • Low Cycle Fatigue


H484 H384 & H598
Dimensions 3.00” H x 6.00” W x 7.16” D 3.75” H x 5.75” W x 6.50” D
Weight 4 lbs 4 lbs
Processor 32 BIT RISC 32 BIT RISC
Input Power 14 to 40 VDC, 50W 14 to 40 VDC, 50W
Operating Range -40 to 70 °C -40 to 70 °C
Frequency Inputs [email protected] 3.5 to 30,000 Hz [email protected] 3.5 to 30,000 Hz
Thermocouples 2 ANSI Type K 8 ANSI Type K
RTD Inputs 2 3
Discrete Inputs [email protected] 0 to 28 VDC [email protected] 0 to 28 VDC
High Level Inputs [email protected] ±30 VDC [email protected] ±30 VDC
Discrete Outputs [email protected] 28 VDC, 1 Amp [email protected] 28 VDC, 1 Amp
Serial Interface USB/RS-232 RS-232