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# Calculating landing distances

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Hello again! I didn't see in the manual anything about figuring landing lengths needed to figure what runways are ok. Does anyone know the correct way to do this?Thanks!

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Ahh, finally. A mathematics question. The equation for runway length use is represented as follows0.5*((Approach Airspeed - Headwind)*1.6878)^2 / Rate of Deceleration + 1000Approach Airspeed - Headwind equates to your groundspeed. 1.6878 is the conversion from knots to ft/sec. The rate of deceleration is in ft/sec and the addition of 1000 at the end takes into account that the glideslope marker is positioned on average 1000 feet from the threshold.Your headwind is determined by the equation below. If your calculator is set to degrees, ignore the PI/180, that is for radians.COS((PI/180)*(Difference of runway heading to wind direction))*Wind Speed

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mmmm I think a bit of leg pulling is going on. :( Kyle to answer the questiondetermine your TOW or LW, go to the performance charts in your manual, get ambient temperature and wind then look it up from there.and for landing if you are flying a QANTAS aircraft dont forget to add the length of the golf course at the far end... :(

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and for landing if you are flying a QANTAS aircraft dont forget to add the length of the golf course at the far end... :(
Haha, yes! And for your captain commanding a go around then retarding thrust levers 1-3 without telling you when you touch the ground and leaving no. 4 at take-off thrust!I think if you have TOPCAT it will calculate landing distances for you.The equations above don't seem like leg-pulling. Cheers,Rudy

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Hi, I am using program TOPCAT. You can try it for 747 for free. But finally I found it perfect an purchased it.

//double-post//

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Bob, those are the real equations for acceleration. Because deceleration is nothing but acceleration in the opposite direction, the equation works backwards, going from your stop point, up to your approach airspeed, and giving back a distance in feet. "Approach Airspeed" is equivalent to desired final speed, "Rate or Deceleration" is equal to a rate of acceleration.I would venture to say TOPCAT uses a variation of this, if not the exact equation. My calculator is uses it as well (Bonus, its free).

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mmmm I think a bit of leg pulling is going on. :(
I dare to disagree with this comment. The equations proposed are in fact accurate for both take-off and landing distance (with a sign diff). Instead it would have been more appropriate to say that there are actually programs which are doing it for you such as TOPCAT or if you want to spare 10 minutes on an excel sheet you can create your own spreadsheet based on the formulas given in the second post.Cheers

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Ahh, finally. A mathematics question. The equation for runway length use is represented as follows0.5*((Approach Airspeed - Headwind)*1.6878)^2 / Rate of Deceleration + 1000 Approach Airspeed - Headwind equates to your groundspeed. 1.6878 is the conversion from knots to ft/sec. The rate of deceleration is in ft/sec and the addition of 1000 at the end takes into account that the glideslope marker is positioned on average 1000 feet from the threshold. Your headwind is determined by the equation below. If your calculator is set to degrees, ignore the PI/180, that is for radians. COS((PI/180)*(Difference of runway heading to wind direction))*Wind Speed
Rate of Deceleration is in ft/sec², by the way... just a nit-pick.The SI equation would be:0.5*((Vapp - Headwind)*0.5144)² / Rate of Deceleration + 304.8 = distance in metres.Frank Grivel

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