This is a copy of a letter that was sent by Mr. Bruce Baker of Servos & Simulation to Mr. Edward Boothe at the National Simulator Evaluation Program Flight in Atlanta, GA. It is in regards to a simulator upgrade for a CH-46 at MCAS Tustin. The main problem was that the motion base was not following the visual cues and made it hard for the pilots to train on (simulator sickness). The problem was resolved...
March 27, 1992
Mr. Edward M. Boothe Manager
National Simulator Evaluation Program Flight Standards Division, AS0-205
P.O. Box 20636
Atlanta, Georgia 30320
In February of this year, we at Servos and Simulation together with Eyring Corporation from Salt Lake City completed a major upgrade to the CH-46 simulator at MCAS Tustin. This upgrade consisted primarily of the addition of a blade element rotor model and improvements in the motion base. Now that the Marine pilots have been flying the simulator for six weeks, I called one of the instructor pilots (Jim Shirk 714-726-7557) at Tustin to discuss the reaction of the pilots. Following are his comments:
- There is a tendency to over control the aircraft in roll with the motion base turned off. This tendency disappears with the motion turned on.
- The simulator is much easier to fly at hover with the motion on than with the motion off. At forward speed the improvement is not as noticeable, primarily since the aircraft is easier to fly.
- The simulator sickness problem may have been solved. The over-controlling of the aircraft in roll may have been a primary contributor to simulator sickness. Sherry Jones at NTSC is doing a study on sickness and one of the simulators she is studying is the CH-46.
The frequency response of the motion base was measured including the washout equations. The aircraft acceleration input was driven, and the acceleration of the motion base was measured. The motion base coordinate system was centered at the cg of the aircraft, which on the CH-53 is 15 feet behind the pilot. The frequency response plots show a 5-9 Hz response (90 deg phase) in all axes, with the highest response being in roll, pitch, and heave. The phase response goes through zero between 1 and 2 Hz, and so the phase margin of the pilots control loop has not been significantly changed in the vicinity of his crossover frequency. I have enclosed copies of the motion base measured response.
It appears from this that a competent human factors study would put to bed the question of motion vs no motion, and that the worth of the motion bases would be firmly established.
E. Bruce Baker
It would be nice to find the study that Sherry Jones at NTSC prepared. I would love to read it.
It is interesting to note that without motion, the pilot had a tendency to over control the aircraft. That learning to hover the aircraft is easier, and that the motion base being on has reduced the motion sickness of the pilots.