Speed Help

Pro Member Trainee
captainsimon Trainee

A few questions:

Is the IAS in knots?

Also why can i fly at FL150 at 330k IAS on a 737-800 but at FL380 I can only do 250k IAS

Also I was under the understanding that flying under FL100 the speen was limited to 250k IAS, when going over 250k FSX does not call up an overspeed warning.

Thanks in advance gents.

2 Responses

Pro Member First Officer
Llain First Officer

HI IAS is in knots

IAS= Indicated Airspeed which is not the same as the speed you are travelling over the ground. The higher you fly the air becomes thinner or less dense, this means you have to fly faster to get the same amount of air through the pilot tube and over the wings in the same amount of time. The pilot tube is used for the airspeed indicater.
so if you are flying at FL150 at 330k you are in fact doing about say 430k over the ground G/S, if you the fly at FL380 at 250k you will be doing about 500k.

Use the GPS to check your ground speed= G/S
On the B737 the speed limit is shown by a red line on the airspeed indicater and the stall limit by the yellw line. These will change as you change flight level

You also say that FSX does not call out over speed limit when flying over 250k below FL100 this is because this is imposed by ATC not by the speed limit of the aircraft. It is up to the pilot to remain below 250k below FL100.
FSX does not impose this but it might be something they can include the next FLIGHT SIM.

THese are common mistake poeple make when new to FS or avation
I hope this helps you understande how IAS works

Pro Member Trainee
captainsimon Trainee

Thanks Liam

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