Abstract: Disclosed is a system and method for horizontal directional drilling (HDD). The system and method utilize predictive algorithms to both characterize the soil within the borehole and to quantify instability within the drillstring. The soil characteristics are represented by a soil coefficient (?) which relates the curvature of the borehole with the length of thrust of the drill rig as well as by comparison of thrust while thrusting with torque while drilling. The value of (?) is obtained by comparison of the historical orientation of the drilling head over the length of the borehole and the borehole shape as determined by an arbitrary navigation sensor. Drillstring instability is determined as a function of historical thrust and torque efficiencies and windup over the length of the borehole.

Abstract: Disclosed is a system and method for horizontal directional drilling (HDD). The system and method utilize predictive algorithms to both characterize the soil within the borehole and to quantify instability within the drillstring. The soil characteristics are represented by a soil coefficient (?) which relates the curvature of the borehole with the length of thrust of the drill rig as well as by comparison of thrust while thrusting with torque while drilling. The value of (?) is obtained by comparison of the historical orientation of the drilling head over the length of the borehole and the borehole shape as determined by an arbitrary navigation sensor. Drillstring instability is determined as a function of historical thrust and torque efficiencies and windup over the length of the borehole.

Abstract: Disclosed is a system and method for horizontal directional drilling (HDD). The system and method utilize predictive algorithms to both characterize the soil within the borehole and to quantify instability within the drillstring. The soil characteristics are represented by a soil coefficient (?), which relates the curvature of the borehole with the length of thrust of the drill rig as well as by comparison of thrust while thrusting with torque while drilling. The value of (?) is obtained by comparison of the historical orientation of the drilling head over the length of the borehole and the borehole shape as determined by an arbitrary navigation sensor. Drillstring instability is determined as a function of historical thrust and torque efficiencies and windup over the length of the borehole.

Abstract: Disclosed is a system and method for horizontal directional drilling (HDD). The system and method utilize predictive algorithms to both characterize the soil within the borehole and to quantify instability within the drillstring. The soil characteristics are represented by a soil coefficient (?), which relates the curvature of the borehole with the length of thrust of the drill rig as well as by comparison of thrust while thrusting with torque while drilling. The value of (?) is obtained by comparison of the historical orientation of the drilling head over the length of the borehole and the borehole shape as determined by an arbitrary navigation sensor. Drillstring instability is determined as a function of historical thrust and torque efficiencies and windup over the length of the borehole.

Abstract: A nozzle guide structure (10) is provided for receiving a fuel nozzle (34) in an opening (30) in a planar bulkhead (28) of a combustion chamber (12). The guide structure (10) includes an inner bushing (44), a transverse heat shield (46), and an annular retainer (52) disposed opposite the heat shield (46) with respect to the bulkhead (28). Flow openings (62) disposed in the retainer (52) admit cooling air (64) into an annular gap (50) formed between the bushing (44) and the bulkhead (28). the cooling air (64) subsequently flow between the bulkhead (28) and the heat shield (46) to provide cooling thereto.