I think all sounds are repeated, when you enter, the seatbelt click plays multiple times too.
May 10 2016
Might be windows sticky keys feature freezing it. Check the settings described here http://www.techrepublic.com/blog/windows-and-office/quick-tip-disable-the-sticky-and-filter-keys-in-windows/
That's how VSync works in every game. Your FPS will be capped at your monitors refresh rate. If your FPS drops below your refresh rate the cap will drop to half of your refresh rate.
Here's a better explanation to why this happens: http://www.tweakguides.com/Graphics_9.html
May 9 2016
@Raistlen007 The engine only starts with up collective which starts at 50% if you have both the raise and lower collective assigned to different parts of the axis.
If you want to use 100% of the slider range for up collective you can do so by assigning both the - and + range of the slider axis to 'collective raise' and nothing to 'collective lower'. You will lose some descent speed by doing this though. But it'll start the engines even at 1%.
You'll get 75% for up collective and 25% down by assigning both the - and + range to 'collective raise' and only + or - to 'collective lower', depending which way you use the throttle. This will not decrease the descent speed.
Keep in mind the order in which the - and + ranges are listed in the controls affects the direction in which the throttle functions.
Also have a Saitek X52 Pro and the collective works fine for me.