File(s) under permanent embargo

Reason: This item is currently closed access.

Modeling and specification of time-limited dispatch categories for commercial aircraft

journal contribution
posted on 24.10.2008, 11:01 by Darren R. Prescott, J.D. Andrews
Time-limited dispatch allows the degraded redundancy dispatch of aircraft. Aircraft can be dispatched with certain control system faults and fault combinations for specified periods of time if the failure rates from those configurations meet certification requirements. The various system faults and fault combinations are assigned to dispatch categories according to these failure rates. This gives the dispatch criteria for the system. The overall failure rate of the system can then be calculated according to the dispatch criteria. Dispatch criteria are allocated to a small example system, and the system is subsequently modeled using a reduced-state Markov approach currently recommended in SAE ARP5107. An alternative method of setting dispatch criteria and modeling systems, using Monte Carlo simulation, is proposed in this paper, and this technique is also applied to the example system. Dispatch criteria applied to the different models are seen to differ, as are the system failure rates calculated using the different models. A method for setting the dispatch criteria for a system using a Monte Carlo simulation approach is introduced. The method is applied to a simple system, giving auditable results that exhibit the expected behavior for such a system. Because restrictive assumptions in the mathematics are unnecessary with Monte Carlo simulation, it is expected to give more accurate results in comparison to Markov approaches. Also, the results of the reduced-state Markov model appear to be largely dependent on failure rates, which are very difficult to determine.



  • Aeronautical, Automotive, Chemical and Materials Engineering


  • Aeronautical and Automotive Engineering


PRESCOTT, D.R. and ANDREWS, J.D., 2008. Modeling and specification of time-limited dispatch categories for commercial aircraft. American Society of Mechanical Engineers Journal of Dynamic Systems Measurement and Control, 130(2), 021004


© 2008 American Society of Mechanical Engineers

Publication date



This article is Restricted Access. It was published in the journal, ASME Journal of Dynamic Systems, Measurement and Control [© 2008 American Society of Mechanical Engineers] and ia available at