Main reason for not firing in the Glen with the PC9 is the chance of riccochets coming back up into the path of the aircraft. Obviously the bedrock in the hills is not that deep underground and can result in this. Anyone who has watched a .5 firing into supposed bog and seen tracer rounds spinning off into the distance will vouch for this. Supposedly, water is just as bad for riccochets, so I'm not too sure if the PC9 drivers have a specific SOP for firing on the water target in Gormo or if they restrict the .5 firing to the beach target. With the rockets breaking up on impact, there is no chance of them riccocheting if fired from the correct profile. Strangely enough, the arguement to stop firing of the 7.62 and rockets from the Marchetti was based on the possibility of shots falling outside the safety template, but anyone who has done basic marksmanship theory will know that the beaten area of a weapon fired from an elevated position is reduced compared to one fired from the ground. The possibility of a runaway gun was present, but in many cases, the pilot would be aware of this occurring and would keep the nose pointed in a safe direction until ammunition was expended. Ground clearance issues and noise issues were also considered. At the end of the day, it was windiness on the part of the authorities who control the Glen range.
