Swept Wing Theory
Hi can anyone help on this? I have always since my ATPL training struggled with this one.
I was taught that for faster airspeeds swept wings can help delay onset of Mcrit by effectively "fooling" the air into thinking that it was travelling slower. I always visualised this as the wing cross section being made thinner by virtue of sweepback (thickness to chord ratio lower) as if taking a slice out of the wing along an axis parrallel to the logitudinal. In this case obviously the air is less accelerated owing to lower effective camber, so the flow is slower than it otherwise would be (with the consequence that the aerofoil produces lower lift at all speeds - necessitating amongst other things higher angle of attacks).
If this is correct, would it therefore not be more correct to say that this effect itself is not the prime reason for sweepback? Afterall, would not a straight wing with the same thickness/chord ratio and camber produce the same effect in terms of speed of air across the aerofoil?
Would it not be better to say that sweepback in isolation has the main effect of providing greater streamlining when viewing an aeroplane from above, and leave it at that?
On a seperate note, why do swept wing aircraft fly with higher nose up attitudes (eg on an ILS)? Is it because angle of attack has to be higher owing to lower cross sectional camber, or is it to do SPECIFICALLY with sweepback ie wing tips being further behind roots)?
Thanks - I hope I have put forward what I am trying to say in an intelligible manner