Hi dubaibilly & welcome to SimV,
The 'problem' you are experiencing with the overspeed alarm going off at 335 in the Learjet is correct.
The problem you have is that you are looking at the speed in KIAS (Knots Indicated Airspeed) - basically, this is the rate of speed that 'air' is hitting your plane at. The max operating speed for a Learjet in KIAS is 335.
However, the higher you fly the faster you will be going because the air is thinner (Even though your KIAS will still be reading 335 - your groundspeed & Mach will be higher).
Above 15,000ft you will need to look at your speed measured in Mach & not KIAS (The blue numbers beneath where you are reading your airspeed is the Mach indicator - it will say something like M 0.55)
How fast you can fly will be directly linked to how high (up to a point) you are flying.
The readings below were taken in clear weather (29.92 inches of mercury on the altimeter) - they will show you the differences in speed compared to KIAS, relative to the altitude I was flying at:
8000ft at 335KIAS = Mach speed of 0.55 (Groundspeed of 359kn)
25,000ft at 335KIAS = Mach speed of 0.76 (Groundspeed of 460kn)I hope this has helped you a bit, just remember KIAS isn't the only way to measure speed & is really only a useful measure of speed at low altitudes (Although you will have to take into account the direction & speed of the wind).
There was a really good discussion on it
HERE that might prove helpful.
Cheers,
TSC.
)
