Rob,
B&S answers the basic question you ask - but how much difference between 100' and 5000'? A rough guide is to add approximately 3 knots per 1000' altitude to get TAS
For example: a sea level runway threshold speed of 140kts Indicated Air Speed (which is what the pilot sees on his instruments) results in a groundspeed of 140 kts with no head or tail wind. However for the same IAS, at 5000' the groundspeed becomes approximately155kts. As this speed is obviously the one that affects stopping distance it results in a significant difference in landing distance required.
As I say, a rough guide, because temperature also come into it, but close enough for government work!
1106
Last edited by Type1106; 13th Jul 2010 at 14:35.
Reason: To explain that the IAS for the weight remains the same groundspeed changes