Standard Article

Health and Usage Monitoring Systems (HUM Systems) for Helicopters: Architecture and Performance

Aerospace Applications

Full-Scale Aerospace Vehicles

  1. Kenneth Pipe

Published Online: 15 SEP 2009

DOI: 10.1002/9780470061626.shm127

Encyclopedia of Structural Health Monitoring

Encyclopedia of Structural Health Monitoring

How to Cite

Pipe, K. 2009. Health and Usage Monitoring Systems (HUM Systems) for Helicopters: Architecture and Performance. Encyclopedia of Structural Health Monitoring. .

Author Information

  1. Humaware, Petersfield, UK

Publication History

  1. Published Online: 15 SEP 2009


To enable the helicopter operator to discriminate between wide price/performance variations in the range of systems marketed as HUM system (health and usage monitoring system) requires that the systems' performance can be measured against recognized standards that relate to the HUM system's primary function of enhancing helicopter airworthiness. This article explores the criteria for measuring the performance of a HUM system, the features of the system that are important, and the standards that can be applied.

Ultimately, the performance of a HUM system is measured in actuarial terms, i.e., the impact of the technology in reducing the number of catastrophic and hazardous events on helicopters. The Regulatory Authorities and the manufacturers maintain appropriate statistical records on helicopter safety, but there is no consensus on how to factor in the contribution of HUM systems to the overall safety improvements achieved since the introduction of the technology. Given this difficulty, the article discusses the other performance criteria that are meaningful in establishing a system's efficacy.

The components of a HUM system form a hierarchy, from the sensors, through processing, alarm generation, and finally the operation of the system. The article discusses how the components of a HUM system contribute to its overall performance and the practical performance criteria that can be applied. Health as well as usage functions are covered, as well as functions that relate to maintenance benefits.

HUM systems are unusual in terms of the close interaction between the airborne and ground-based components of the system. Because of this design feature of maintaining the system's integrity when operating in the helicopter environment is a major issue, the article outlines where standards need to be established.

Finally, the airborne components of a HUM system have to perform as any other item of avionics equipment and the standards that are peculiar to the HUM system are discussed.


  • advisory circular (AC);
  • analog to digital (A/D);
  • Civil Aviation Authority (UK) (CAA);
  • commercial off the shelf (COTS);
  • Federal Aviation Authority (US) (FAA);
  • fast Fourier transform (FFT);
  • helicopter airworthiness review panel (HARP);
  • health and usage monitoring (HUM);
  • Joint Airworthiness Authority (Europe) (JAA);
  • minimum equipment list (MEL);
  • mean time between failure (MTBF);
  • mean time to repair (MTTR);
  • root mean square (RMS)