Investigation of Chinook helicopter operations with an external slung load after cable failure

Abstract

NOMENCLATURE a 0f , a 0r coning angle of front and rear rotor (rad) a 1f , a 1r longitudinal disc-tilt angles of front and rear rotors, positive when the rotor disc plane tilts backwards (rad) b 1f , b 1r lateral disc-tilt angles of front and rear rotor, positive when the disc plane tilts to the azimuth position ψ = 90˚ (rad)blade lift curve slope (rad -1 ) C Q rotor torque coefficient (-) C T,elem,f, C T,elem,r rotor thrust coefficients in blade element theory respectively for front and rear rotor (-) C T,Glau,f, C T,Glau,r rotor thrust coefficients in Glauert formulation respectively for front and rear rotor ( ABSTRACTThe Royal Netherlands Air Force (RNLAF) conducts frequent operations of Chinook helicopters with external slung loads. The normal RNLAF practice is for large external loads to be underslung by means of a two-strop suspension system backed up by a third point of suspension, the so-called 'redundant HUSLE (Helicopter Underslung Load Equipment)' comprising a redundant set of slings which come into action if one of the normal strops fails. The redundant HUSLE is relatively expensive in terms of time and operating costs. The present work has investigated the behaviour of a Chinook helicopter with an underslung load following failure of a front or rear strop, to determine whether the three-point suspension system can be safely replaced by a two-point suspension, eliminating the redundant HUSLE. The paper will demonstrate that although in general the redundant HUSLE results in a less violent helicopter reaction to a cable failure, it does not necessarily guarantee safety. It is concluded that flying with loads up to around two tonnes could be done safely with a two-point suspension system. A novel feature of this analysis of helicopter operations with slung loads is the integrated approach used for simulating pilot-in-the-loop load failures using a full non-linear model.

Automatic Flight Control Systems

“…The goal of the chapter will be to implement the advanced automatic flight control system AFCS of the Chinook CH-47 (analogue in Chinook D-version and digital in the latest version F) into a generic Chinook model developed at Delft University of Technology (Van der Kamp et. Al (2005), Reijm, Pavel&Bart (2006), Pavel(2007), Pavel(2010) and investigate the effects that AFCS may have on the recovery prospects of the Chinook helicopter after a failure scenario of its load. In other words, this chapter proposes to analyse how the advanced AFCS, implemented in general in order to improve the handling qualities characteristics, may improve/degrade the CH-47 behaviour during emergency situations such as failure scenarios of its suspended load(s).…”

“…( Van der Kamp et. Al, 2005) (Reijm, Pavel&Bart, 2006) and (Pavel, 2010) investigated whether the three-strop suspension system -usually used to transport large loads (see righthand side in Fig. 1) can be safely replaced by a two-strop suspension.…”

“…A general non-linear six degree-of-freedom (6-dof) rigid body model for a generic tandem helicopter was first developed for piloted simulations ((Van der Kamp et. Al, 2005, Pavel, 2010. In a general non-linear 6-dof model the helicopter motion is represented by three translations and three rotations around the body axes-system centred on the helicopter centre of gravity, see Figure A 1 in Appendix A.…”

Effects of Automatic Flight Control System on Chinook Underslung Load Failures

“…Al, 2005, Pavel, 2010. In a general non-linear 6-dof model the helicopter motion is represented by three translations and three rotations around the body axes-system centred on the helicopter centre of gravity, see Figure A 1 in Appendix A.…”

“…Al, 2005) (Reijm, Pavel&Bart, 2006) and (Pavel, 2010) investigated whether the three-strop suspension system -usually used to transport large loads (see righthand side in Fig. 1) can be safely replaced by a two-strop suspension.…”