Comanche Crew Station Development - helicopter design

Program Manager, Sept, 2000 by Deborah J. Chase, Robert R. Copeland, Ronald J. Ferrell

"Mockpit" Lets Comanche Fly in Simulation Long Before Actual Aircraft Production

During the two years leading to Engineering, Manufacturing and Development (EMD) Milestone approval in April 2000 for the Comanche RAH-66 advanced technology helicopter, the Army Training and Doctrine Command (TRADOC) System Manager (TSM), Program Manager (PM), and industry team initiated design and process improvements related to both physical and cognitive aspects of Comanche's crew station design. These improvements, made possible only by recent unprecedented advances in computer processing technology allowed the Comanche program to maximize user involvement early in the process of designing a weapon system with the best possible pilot-vehicle interfaces.

Modeling and Simulation, Computer Aided Design

A variety of modeling and simulation tools provide the means to obtain feedback from developmental test pilots and Army aviators with combat experience. Computer Aided Design tools and other leading-edge human engineering models and simulations allow the weapon system developer to iterate potential airframe design solutions to satisfy issues arising from the user feedback And, simulations allow the materiel developers to evaluate how well the crew station design accommodates human cognitive processes to ensure the crew workload and pilot training techniques are effective.

"Growing the Cockpit"

Based on user input and a preliminary Army Research Laboratory-Human Research and Engineering Directorate (ARL-HRED) evaluation indicating that the Comanche cockpit may have been too small, a Crew Station Process Action Team (CSPAT) was formed that included members from the Aviation Technical Test Center, Aviation Research and Development Center, the ARL-HRED, and the program office/industry team. The question, "Do we need to grow the cockpit?" needed to be answered prior to the Weapon System Design Review, six months away at the time. The impact of "growing the cockpit" would be substantial, including expansion of the existing aircraft outer mold line.

Historically, "human factors" engineers evaluated the adequacy of a cockpit design after an aircraft was built, taking measurements in the aircraft itself. Although two prototype aircraft existed at the time of the study, planned design changes for future aircraft would further impinge on cockpit volume. Also, the total population required to be accommodated within the cockpit increased in 1996 after design of the existing prototype aircraft. Fortunately, significant improvements over the past five years in human engineering tools and human figure modeling allowed the CSPAT to conduct an "early intervention" without need for an actual aircraft.

The first step in answering the overarching question about the cockpit was to

FaroArm

resolve a longstanding disagreement about the design eye point (DEP). Because of perceived flaws in previous analysis based on helicopters with floor-mounted cyclics and questions about formal guidelines, the CSPAT decided to determine the actual measured eye reference point (MERP). The CSPATs hypothesis was that a pilot using a sidearm-controller would sit in a more erect posture than one using a cyclic control.

We developed a methodology to locate the MERP, which included placing 20 subject aviators, including TSM pilots, in the full-scale Comanche mockup. We then used a FaroArm to measure the location of specific anatomical features. The FaroArm, originally designed for surgical applications, measures a point location in three dimensions to 2-sigma accuracy.

The evaluation concluded that none of the earlier DEP analysis and guidelines adequately predicted the MERP. We were left with two alternatives for the application of our data: a major redesign, or a minor redesign in such a way as to place the MERP as close to the Comanche DEP as possible. We proceeded with the latter, since the variances were minor and fewer perturbations were created in the total aircraft design.

Once the industry-government team was satisfied that the DEP was properly placed, it proceeded to determine whether the cockpit design provided adequate knee clearance; a specific concern to the TSM pilots and the ARL-HRED preliminary evaluation. The CSPAT evaluated knee clearance accommodation in three segments.

* First it was necessary to take measurements in the aircraft using the FaroArm to ensure that the computer-graphic-aided 3D interactive applications (CATIA) data accurately represented the actual aircraft.

Second, we needed to use the data we collected to conduct modeling using Natick-developed human figures to represent the required population in the Transom Jack model. Transom Jack allows the modeler to place figures of varying dimensions in a cockpit built with CATIA design data. The human figure modeling effort allowed us to develop recommendations for the design engineers.

Finally to quantify the population that the cockpit accommodated in various design iterations, the CSPAT sought the help of Naval Air Warfare Center Crew Station (NAWC 4.6) to conduct statistical modeling similar to that which they developed for the Joint Primary Aircraft Training System. Based on the CSPATs input, the crewmember's seat was redesigned from one that adjusts on a single axis to one that allows dual-axis adjustment. The CSPAT's effort showed that expanding the outer mold line was not necessary. Comanche will provide the necessary anthropometric accommodation for knee clearance with a seat redesign. The CSPAT has continued its collaboration with industry, the user, and NAWC to identify design changes that will improve accommodation for both reach and ingress/egress requirements in the same fashion as was accomplished for knee clearance.