This article focuses on the design, fabrication, testing, modeling, and validation of a spanwise variable camber section of a helicopter rotor blade. The lower surface skin was slit aft of the trailing edge spar and subjected to a spanwise warping actuation input. A kinematic linkage facilitates a corresponding chordwise motion of the skin along the span length (from zero at the no-camber end to maximum at the maximum camber end). Input warping actuation of 0.18 in length produced an 18° camber variation over a 45 in span section of a modified CH-46 blade. Finite element model predictions of the active camber section showed good agreement with benchtop test data for both the output camber for a given warping actuation input and the corresponding actuation force required. Finite element results suggest that some geometry distortions in the active camber section could be experienced due to the presence of centrifugal and aerodynamic loads, but these distortions could be alleviated with the introduction of a shear-flexible (but stiff through the thickness) core.
AiroldiACrespiMQuarantaG. (2012) Design of a morphing airfoil with composite chiral structure. Journal of Aircraft49(4): 1008–1019.
2.
ArnoldUTP (2003) Recent IBC flight test results from the CH-53G helicopter. In: Proceedings of the 29th European rotorcraft forum, Friedrichshafen, 16–18 September.
3.
AsheghianLReichGEnkeA. (2011) Shear morphing skins—simulation and testing of optimized design. Journal of Intelligent Material Systems and Structures22: 945–960.
4.
BaeEGandhiF (2010) Optimally actuated spanwise-segmented aerodynamic effectors for rotorcraft power reduction. In: Proceedings of the 66th annual forum of the American Helicopter Society, Phoenix, AZ, 11–13 May.
5.
BaeEGandhiFMaughmerM (2009) Optimally scheduled deployments of miniature trailing-edge effectors for rotorcraft power reduction. In: Proceedings of the 65th annual AHS international forum and technology display, Grapevine, TX, 27–29 May.
6.
BarbarinoSGandhiFWebsterS (2011) Design of extendable chord sections for morphing helicopter rotor blades. Journal of Intelligent Material Systems and Structures22(9): 891–905.
7.
BettiniPAiroldiASalaG. (2010) Composite chiral structures for morphing airfoils: numerical analyses and development of a manufacturing process. Composites Part B: Engineering41(2): 133–147.
8.
CaldwellNGutmarkE (2007) Performance predictions of a blade twist actuator system. In: Proceedings of the 45th AIAA aerospace sciences meeting and exhibit, Reno, NV, 8–11 January.
9.
CampanileLSachauD (2000) The belt-rib concept: a structronic approach to variable camber. Journal of Intelligent Material Systems and Structures11(3): 215–224.
10.
ChengRPCeliR (2005) Optimum two-per-revolution inputs for improved rotor performance. Journal of Aircraft42(6): 1409–1417.
11.
ChengRPTheodoreCRCeliR (2003) Effects of two/rev higher harmonic control on rotor performance. Journal of the American Helicopter Society48(1): 18–27.
12.
ChopraI (2002) Review of state of art of smart structures and integrated systems. AIAA Journal40: 2145–2187.
13.
ClingmanDJJacotD (2000) Shape memory alloy consortium and demonstration. In: Proceedings of the smart structures and materials conference (SPIE), Newport Beach, CA, 7March.
14.
GiurgiutiuV (2000) Recent advances in smart-material rotor control actuation. In: Proceedings of the AIAA/ASME/ASCE/AHS/ASC 41st structures, structural dynamics and materials conference, Atlanta, GA, 3–6 April, paper no. AIAA-2000-1709.
15.
HallSYangKHallK (1994) Helicopter rotor lift distribution for minimum-induced power loss. Journal of Aircraft31(4): 837–845.
16.
HaydenE (2012) Design and testing of a helicopter rotor blade chord extension system. Master’s Thesis, The Pennsylvania State University, University Park, PA.
17.
JacklinSANguyenKBlaasA. (1994) Full-scale wind tunnel test of a helicopter individual blade control system. In: Proceedings of the American Helicopter Society 50th annual forum, Washington, DC, 11–13 May, pp. 579–596.
18.
JacklinSANguyenKRichterP. (1995) Reduction in helicopter BVI noise, vibration, and power consumption through individual blade control. In: Proceedings of the American Helicopter Society 51st annual forum, Fort Worth, TX, 9–11 May.
19.
KesslerCFuerstDArnoldUTP (2003) Open loop flight test results and closed loop status of the IBC system on the CH-53G helicopter. In: Proceedings of the AHS 59th annual forum, Phoenix, AZ, 6–8 May.
20.
KhoshlahjehMGandhiF (2014) Extendable chord rotors for helicopter envelope expansion and performance improvement. Journal of the American Helicopter Society59(1). DOI: 10.4050/JAHS.59.012007.
21.
KroningerC (2008) Characteristics of a rotor optimized for hover and forward flight. MS Thesis, The Pennsylvania State University, University Park, PA.
22.
LachenalXDaynesSWeaverP (2013) A zero torsional stiffness twist morphing blade as a wind turbine load alleviation device. Smart Materials and Structures22: 065016.
23.
LeonOGandhiF (2009) Rotor power reduction using multiple spanwise-segmented, optimally-actuated trailing-edge flaps. In: Proceedings of the 35th European rotorcraft forum, Hamburg, 22–25 September.
24.
LeonOHaydenEGandhiF (2009) Rotorcraft operating envelope expansion using extendable chord sections. In: Proceedings of the 65th annual AHS international forum and technology display, Grapevine, TX, 27–29 May.
25.
LiuLFriedmannPPKimI. (2008) Rotor performance enhancement and vibration reduction in presence of dynamic stall using actively controlled flaps. Journal of the American Helicopter Society53(4): 338–350.
26.
McHughFJShawJ (1978) Helicopter vibration reduction with higher harmonic blade pitch. Journal of the American Helicopter Society23(4): 26–35.
MiaoWKottapalliSBRFryeHM (1986) Flight demonstration of higher harmonic control (HHC) on S-76. In: Proceedings of the 42nd AHS forum, Washington, DC, 2–4 June, pp. 777–791.
29.
MistryM (2008) Induced warp systems to obtain active twist of rotor blades. MS Thesis, The Pennsylvania State University, University Park, PA.
30.
MistryMGandhiF (2012) Hover performance improvement with warp-induced spanwise camber variation. In: Proceedings of the 68th annual AHS international forum and technology display, Fort Worth, TX, 1–3 May.
31.
MistryMNagelsmithMGandhiF. (2011) Actuation requirements of a warp induced variable twist rotor blade. Journal of Intelligent Material Systems and Structures22(9): 919–933.
32.
MoffittRCBissellJR (1982) Theory and application of optimum airloads to rotor in hover and forward flight. In: Proceedings of the American Helicopter Society 38th annual forum, Anaheim, CA, 4–7 May.
33.
MoserPBarbarinoSGandhiF (2012) Helicopter rotor blade chord extension morphing using a centrifugally actuated von-Mises truss. In: Proceedings of the ASME 2012 conference on smart materials, adaptive structures and intelligent systems, SMASIS2012, Stone Mountain, GA, 19–21 September, paper no. SMASIS2012-8053.
34.
NguyenKChopraI (1990) Application of higher harmonic control to rotors operating at high speed and thrust. Journal of the American Helicopter Society35(3): 78–89.
35.
NguyenKChopraI (1992) Effects of higher harmonic control on rotor performance and control loads. Journal of Aircraft29(3): 336–342.
36.
OlympioKRGandhiF (2010) Zero-Poisson’s ratio cellular honeycombs for flex skins undergoing one-dimensional morphing. Journal of Intelligent Material Systems and Structures21(17): 1737–1753.
37.
OlympioKRGandhiFAsheghianL. (2010) Design of a flexible skin for a shear morphing wing. Journal of Intelligent Material Systems and Structures21(17): 1755–1770.
38.
PrahladH (2002) Development of shape memory alloy (SMA) torsional actuators for variable twist tilt rotor (VTTR) blades. PhD Thesis, University of Maryland, College Park, MD.
39.
PrahladHChopraI (2001) Design of a variable twist tilt-rotor blade using shape memory alloys (SMA) actuators. In: Proceedings of the smart structures and materials conference (SPIE), Newport Beach, CA, 5 March.
40.
PrahladHChopraI (2002) Characterization of SMA torsional actuators for active twist of tilt rotor blades. In: Proceedings of the 43rd AIAA/ASME/ASCE/AHS/ASC structures, structural dynamics and materials conference, Denver, CO, 22–25 April.
41.
RandOKhromovVPeyranRJ (2004) Minimum-induced power loss of a helicopter rotor via circulation optimization. Journal of Aircraft41(1): 104–109.
42.
RobinsonLHFriedmannPP (1991) A study of fundamental issues in higher harmonic control using aeroelastic simulation. Journal of American Helicopter Society36(2): 32–43.
43.
RuggeriRArbogastDBussomR (2008) Wind tunnel testing of a lightweight 1/4-scale actuator utilizing shape memory alloy. In: Proceedings of the 49th AIAA/ASME/ASCE/AHS/ASC structures, structural dynamics, and materials conference, Schaumburg, IL, 7–10 April.
44.
RuggeriRJacotDClingmanD (2002) Shape memory actuator systems and the use of thermoelectric modules. In: Proceedings of the smart structures and materials conference (SPIE), San Diego, CA, 17 March.
45.
SakaryaE (2010) Structural design and evaluation of an adaptive camber wing. Master’s Thesis, Middle East Technical University, Çankaya.
46.
SeberGSakaryaEInsuyuT. (2009) Evaluation of a camber morphing concept based on controlled flexibility. In: Proceedings of the international forum on aeroelasticity and structural dynamics, Seattle, WA, 21–25 June, paper no. IFASD-2009-182.
47.
ShawJAlbionNHankerEJ. (1989) Higher harmonic control: wind tunnel demonstration of fully effective vibratory hub force suppression. Journal of the American Helicopter Society34(1): 14–25.
48.
ShawJAlbionN (1980) Active control of the helicopter rotor for vibration reduction. In: Proceedings of the American Helicopter Society 36th forum, Washington, DC, 13–14 May.
49.
The Boeing Co. (1983) Helicopter flying qualities characteristics CH-46E, vol. 1. Technical report, Naval Air Development Center (Code 6053). Report no. NADC-81118–60, 3October. Philadelphia, PA: The Boeing Company.
50.
ThomasJO’BrienMPogueW (2008) Active twist hollow beam system. Patent no. US8246303 B2, USA.
Van WeddingenYBauchauOKottapalliS. (2010) Application of out-of-plane warping to control rotor blade twist. In: Proceedings of the American Helicopter Society aeromechanics specialists conference, San Francisco, CA, 20–22 January.
53.
VosRGurdalZAbdallaM (2008) A novel mechanism for active wing warping. In: Proceedings of the 49th AIAA structures, structural dynamics, and materials conference, Schaumburg, IL, 7–10 April.
54.
VosRGurdalZAbdallaM (2010) Mechanism for warp-controlled twist of a morphing wing. AIAA Journal of Aircraft47: 450–457.
55.
WachspressDQuackenbushTSolomonC (2005) On minimum induced power of the helicopter rotor. In: Proceedings of the 61st annual American Helicopter Society forum, Grapevine, TX, 1–3 June.
56.
WalshDM (1986) Flight test of an open loop higher harmonic control system on an S-76A helicopter. In: Proceedings of the 42nd AHS forum, Washington, DC, 2–4 June, pp. 831–843. Alexandria, VA: AHS International.
57.
YenJG (1981) Higher harmonic control for helicopters with two-bladed and four-bladed rotors. Journal of Aircraft18(12): 1064–1069.
