NDLI: Influence of dynamic inflow on the helicopter vertical response

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Influence of dynamic inflow on the helicopter vertical response

Content Provider	NASA Technical Reports Server (NTRS)
Author	Chen, Robert T. N. Hindson, William S.
Copyright Year	1986
Description	A study was conducted to investigate the effects of dynamic inflow on rotor-blade flapping and vertical motion of the helicopter in hover. Linearized versions of two dynamic inflow models, one developed by Carpenter and Fridovich and the other by Pitt and Peters, were incorporated in simplified rotor-body models and were compared for variations in thrust coefficient and the blade Lock number. In addition, a comparison was made between the results of the linear analysis, and the transient and frequency responses measured in flight on the CH-47B variable-stability helicopter. Results indicate that the correlations are good, considering the simplified model used. The linear analysis also shows that dynamic inflow plays a key role in destabilizing the flapping mode. The destabilized flapping mode, along with the inflow mode that the dynamic inflow introduces, results in a large initial overshoot in the vertical acceleration response to an abrupt input in the collective pitch. This overshoot becomes more pronounced as either the thrust coefficient or the blade Lock number is reduced. Compared with Carpenter's inflow model, Pitt's model tends to produce more oscillatory responses because of the less stable flapping mode predicted by it.
File Size	1339743
Page Count	51
File Format	PDF
Alternate Webpage(s)	http://archive.org/details/NASA_NTRS_Archive_19870015049
Archival Resource Key	ark:/13960/t6b32rf5p
Language	English
Publisher Date	1986-06-01
Access Restriction	Open
Subject Keyword	Aircraft Stability And Control Dynamic Response Aircraft Stability Helicopters Rotor Aerodynamics Vertical Motion Thrust Loads Hovering Flapping Aircraft Control Ntrs Nasa Technical Reports Server (ntrs) Nasa Technical Reports Server Aerodynamics Aircraft Aerospace Engineering Aerospace Aeronautic Space Science
Content Type	Text
Resource Type	Technical Report

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