wingweight <- function(xx)
{
  ##########################################################################
  #
  # WING WEIGHT FUNCTION
  #
  # Authors: Sonja Surjanovic, Simon Fraser University
  #          Derek Bingham, Simon Fraser University
  # Questions/Comments: Please email Derek Bingham at dbingham@stat.sfu.ca.
  #
  # Copyright 2013. Derek Bingham, Simon Fraser University.
  #
  # THERE IS NO WARRANTY, EXPRESS OR IMPLIED. WE DO NOT ASSUME ANY LIABILITY
  # FOR THE USE OF THIS SOFTWARE.  If software is modified to produce
  # derivative works, such modified software should be clearly marked.
  # Additionally, this program is free software; you can redistribute it 
  # and/or modify it under the terms of the GNU General Public License as 
  # published by the Free Software Foundation; version 2.0 of the License. 
  # Accordingly, this program is distributed in the hope that it will be 
  # useful, but WITHOUT ANY WARRANTY; without even the implied warranty 
  # of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 
  # General Public License for more details.
  #
  # For function details and reference information, see:
  # http://www.sfu.ca/~ssurjano/
  #
  ##########################################################################
  #
  # OUTPUT AND INPUT:
  #
  # y  = wing weight
  # xx = c(Sw, Wfw, A, LamCaps, q, lam, tc, Nz, Wdg, Wp)
  #
  ##########################################################################
  
  Sw      <- xx[1]
  Wfw     <- xx[2]
  A       <- xx[3]
  LamCaps <- xx[4] * (pi/180)
  q       <- xx[5]
  lam     <- xx[6]
  tc      <- xx[7]
  Nz      <- xx[8]
  Wdg     <- xx[9]
  Wp      <- xx[10]
  
  fact1 <- 0.036 * Sw^0.758 * Wfw^0.0035
  fact2 <- (A / ((cos(LamCaps))^2))^0.6
  fact3 <- q^0.006 * lam^0.04
  fact4 <- (100*tc / cos(LamCaps))^(-0.3)
  fact5 <- (Nz*Wdg)^0.49
  
  term1 <- Sw * Wp
  
  y <- fact1*fact2*fact3*fact4*fact5 + term1
  return(y)
}