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Confused about cruise speed

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flyforever View Drop Down
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    Posted: 17 Apr 2017 at 1:29am
The dc8 specs indicate a cruise speed of 480kts. How does one test this. I get overspeed  conditions when the IAS reaches 340 kts.  As I bring the aircraft to a higher altitude, not much changes.
What's the secret?
tony
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Mustang1977 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mustang1977 Quote  Post ReplyReply Direct Link To This Post Posted: 17 Apr 2017 at 7:38am
Yo,

The 480 kts is the GS - Ground Speed. The 340 is correct, as you can see the values in the aircraft.cfg (here the 32):

cruise_speed=460.0
max_indicated_speed=370.000000
max_mach=0.88

The max indicated speed can only be reached in a specific height - this you have to find out. This varied from airplane to airplane. Generally between 25.000 - 28.000 ft for Jetliners.

But attention: The GS can easily distorted with wind. So, for best Testresults you have to disable a possible Weatherengine and select the neutral weathermodel.
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Hangar200 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hangar200 Quote  Post ReplyReply Direct Link To This Post Posted: 30 Apr 2017 at 5:17pm
Actually, a DC-8 once went super-sonic.  


…I don't suppose that part of the flight envelope was written into JustFlight's version.  LOL
R/ Hangar 200
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Mike70 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike70 Quote  Post ReplyReply Direct Link To This Post Posted: 30 Aug 2017 at 12:52am
Use 300 knots Indicated below FL310; 0.80 Indicated Mach above FL310 for a decent cruise profile for mid-long range
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