Class A Aircraft - Take-off — Page 395, Lesson 493

Right, we’re now into the take-off speed tables for a Class A aircraft. This is where we actually pull the V speeds — V1, VR, and V2 — out of the performance data. So, in CAP 698, Section 4, you’ll find two sets of speed tables. One is for a 5-degree flap setting, and the other is for a 15-degree flap setting. For our example, we’re going to use 5 degrees of flap, with a regulated take-off mass of 57,900 kg. Now, the first thing you do is identify the column for speed band B. That’s the speed band we’re working in for this example. The left-hand scale of the speed table is mass. Our regulated take-off mass of 57,900 kg sits between the 55,000 kg and 60,000 kg marks. So we have to interpolate to get our V speeds. Let’s do that. For 55,000 kg, V1 is 138 knots. For 60,000 kg, V1 is 145 knots. Interpolating for 57,900 kg gives us V1 equal to 142.06 knots. We’ll round that shortly, but that’s the raw interpolated value. We do the same exercise for VR and V2. For 57,900 kg, VR comes out to 145 knots, and V2 comes out to 152 knots. Now, here’s the important part — V1 must be corrected for slope and wind. That correction is shown in the table at the top of page 18. So the raw interpolated V1 isn’t final; we adjust it based on the runway slope and the wind component before we use it. So to recap: we pick the speed table for our flap setting, find the speed band column, interpolate between the mass marks for V1, VR, and V2, and then apply the slope and wind correction to V1. That gives us our take-off V speeds for the regulated take-off mass.