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Safety and Reliability

Helicopter Landing Ship: Undercarriage Strength and the Role of the Human Factor

[+] Author and Article Information
E. Suhir

 Bell Laboratories, Physical Sciences and Engineering Research Division, Murray Hill, NJ 07974; Department of Electrical Engineering, University of California, Santa Cruz, CA 95064; Department of Mechanical Engineering, University of Maryland, College Park, MD 20742; ERS Company, Los Altos, CA 94024suhire@aol.com

J. Offshore Mech. Arct. Eng 132(1), 011603 (Dec 22, 2009) (6 pages) doi:10.1115/1.4000497 History: Received September 19, 2008; Revised August 17, 2009; Published December 22, 2009; Online December 22, 2009

We address, using probabilistic modeling and the extreme-value-distribution technique, the helicopter undercarriage strength in a helicopter-landing-ship situation. Our analysis contains an attempt to quantify, on the probabilistic basis, the role of the human factor in the situation in question. This factor is important from the standpoint of the operation time that affects the likelihood of safe landing during the lull period in the sea condition. The operation time includes (1) the time required for the officer-on-ship-board and the helicopter pilot to make their go-ahead decisions and (2) the time of actual landing. It is assumed, for the sake of simplicity, that both these times could be approximated by Rayleigh’s law, while the lull duration follows the normal law with a high enough ratio of the mean value to the standard deviation. Safe landing could be expected if the probability that it occurs during the lull time is sufficiently high. The probability that the helicopter undercarriage strength is not compromised can be evaluated as a product of the probability that landing indeed occurs during the lull time and the probability that the relative velocity of the helicopter undercarriage with respect to the ship’s deck at the moment of encounter does not exceed the allowable level. This level is supposed to be determined for the helicopter-landing-ground situation. The developed model can be used when developing specifications for the undercarriage strength, as well as guidelines for personnel training. Particularly, the model can be of help when establishing the times to be met by the two humans involved to make their go-ahead decisions for landing and to actually land the helicopter. Plenty of additional risk analyses (associated with the need to quantify various underlying uncertainties) and human psychology related efforts will be needed, of course, to make such guidelines practical.

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Figures

Grahic Jump Location
Figure 1

Probabilities that the time of HLS operations exceeds the time level T̂ versus the ratio of this level to the most likely time of decision making or the most likely time of landing: (a) the case when the most likely times of decision making and of actual landing are equal and (b) the case when one of the above times is negligibly short compared with the other

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