the Apollo Program". Although Armstrong had to eject from the LLRV, no other astronaut ever had to eject from the LLTV, and every Lunar Module pilot through the final Apollo 17 mission trained in the LLTV and flew to a landing on the Moon successfully. LLRV#2 was eventually returned to the Armstrong Flight Research Center, where it is on display as an artifact of the center's contribution to the Apollo program. In January 1971 LLTV#3 was destroyed while testing a major modification to the LLTV's computer system. Its test pilot, Stuart Present, was able to eject safely. The sole surviving late-model LLTV, NASA 952, is on display at the Johnson Space Center. Lunar Sim Mode There were two distinct modes of flight for the LLRV and LLTV. The basic mode was with the engine fixed so that it remained 'normal' with respect to the body. In the gimbaled "Lunar Sim Mode," the free-gimbaled turbofan engine was allowed to swivel and was kept pointing downward to Earth's center of mass regardless of the LLRV's attitude; this allowed the vehicle to tilt at the far greater angles that would be typical of hovering and maneuvering above the lunar surface. Despite its ungainly appearance, the LLRV was equipped with a highly sophisticated array of early sensors (mainly Doppler radar) and computational hardware. The system had no specific name, but the effect it produced was called "Lunar Sim Mode." This was the highest degree of hardware-based simulation. It was not a system to unburden the pilot, as an autopilot does, nor was it meant to introduce any sort of safety or economy. Lunar Sim Mode can also be thought of as a mixture of stability augmentation, recalculation of vertical acceleration according to the lunar gravity constant, all followed by accompanied instantaneous corrective action. The LLRV's Lunar Sim Mode was even able to correct for wind gusts within milliseconds, as they would have disturbed the impression of a missing atmosphere. FRC test pilot Don Mallick's comments following the vehicle's first flight in the lunar simulation mode illustrate the experience of piloting the LLRV: Deke Slayton, then NASA's Chief Astronaut, later said there was no way to simulate a Moon landing except by flying the LLRV. Specifications (LLRV) Control system The electronic control system for the Lunar Landing Training Vehicle was developed for NASA by Bell Aerosystems, Inc. which had engineering facilities located in Niagara Falls,