• Mainly used to increase Mcrit
• Low Thickness / Chord ratio
• If a wing has sweepback, the effective chord (parallel to the aeroplanes longitudinal axis) is lengthened, but the wings Thickness remains unchanged.
• This reduces the Thickness / Chord ratio of the wing, which results in a higher value of Mcrit, and delays the transonic Drag rise / Shockwave formation.
• The Greater the Sweep back, the higher the value of Mcrit, and the greater the reduction in drag under all transonic speeds.
I found this from the Jeppesen books, now one thing that I feel is confusing and keeps getting mixed up, in many different books, or at least a bit confusing to grasp, is the constant use of the term that the Effective Chord, is the one perpendicular to the Leading Edge!
Now as far as I see this is not completely right, the effective chord is the one Parallel to the aeroplane longitudinal axis! The Vector normal to the leading edge, is only to explain what would have happen if the wing would have been straight, or am I missing a point here?
The Chord, perpendicular to the leading edge, can not be the effective chord of a swept wing? !!!