Hi Tomcat,

It shows overspeed at high altitudes at such a small speed because of the INDICATED airspeed. At 50000 feet the indicated airspeed is half of your true airspeed. So, unless you know about this you think you're travelling half the speed that you really are. You think that the air is moving quite slowly over the wing, though it's really quite fast. I think that overspeed comes at a true airspeed rather than an indicated airspeed. I'm not sure, but you're really travelling faster than you think. If you're cruising at 35000 feet at 400 knots of indicated airspeed, to find your true airspeed do this sum:

Take the first 2 digits of it (35) and multiply it by 2 = 70. Then, devide it by 100 and add it to one. This gives 1.7...
With the 1.7 multiply it by the 400 knots and that equals 680 knots - quite a lot faster than you expected eh? Hope it helped,

- Stevie

When you're flying a heavy at altitude you don't use airspeed - you use mach.

You're using your autopilot aren't you??

Just switch from Speed to Mach - it will cruise all day long at 0.8 - 0.85 mach

Then just pop up your GPS and check out your groundspeed......