Ad: This forum contains affiliate links to products on Amazon and eBay. More information in Terms and rules
Are you planning on taking passengers in this aircraft?For some reason my mind doesn't seem to be working as well as it should be: I understand that if a plane's weight doubles the plane's stall speed increases by the square root of 2 and when calculating for g-load on stall-speed you generally multiply the square of the load-factor against stall-speed to determine what speed the aircraft can pull that load-factor at a bare minimum.
What I'm curious about is the matter of increasing wing area: If the wing area increases two-fold (weird if, but...), does the stall speed decrease by the square root of two or the square of two (four)? I'm curious because there was an aircraft design which had a wing-area of 450 square feet and a proposed derivative with a wing area of 467 square feet (IIRC), I'm curious if it would be (467/450)^2 or sqrt(467/450) to calculate the effect on stall speed?
drgondog , M MIflyer , MiTasol , P pbehn , X XBe02Drvr
And many times the whatever is the take-off and landing speed,The questions should be framed around the desired mission improvement. "I want 20% more range/speed/payload/mpg/whatever".
While this should be something easily understood, I had to plug in numbers to make sense of this (jeez): As I calculate this, the speed decreases by the square of the relationship of the wing area, so if wing area goes up by 2, speed decreases by the square root of 2.
Both wings had the same aspect ratio (that was actually something of interest in my case). It was effectively an advanced F8U-3 derivative and I asked him if the enlarged wing (which the book listed as having a lengthened leading edge that helped deal with the CG drifting excessively far forward) had the same aspect ratio and if the aircraft was also longer. He said the plane was longer and I was able to determine the length of the aircraft and the wing-span by using the position of the fold-line (which would be unlikely to change). While I don't remember how I calculated the wing-area based on what I had, I apparently got the numbers from that and it was either 467 or 469 square feet with the aircraft being around the same as the RF-4B (which struck me as a bit long for a carrier plane, but it wasn't unheard of with RF-4B's being carrier suitable).Simon presented the fundamental relationship for your question. That said, for CL vs alpha, the stall point varies also by aspect ratio of three dimensioal airfoil sections. All Cl vs Alpha presented for airfoils in say, Abbott and Doenhoff, are for infinite span two dimensional wings with no tip effects. The two dimensional data must be modified to account for Aspect Ratio where low AR achieves lowest angle of attack before stall 'break occurs'
I wonder how many flight sim games fail to recognize that last part?Simon presented the fundamental relationship for your question. That said, for CL vs alpha, the stall point varies also by aspect ratio of three dimensioal airfoil sections. All Cl vs Alpha presented for airfoils in say, Abbott and Doenhoff, are for infinite span two dimensional wings with no tip effects. The two dimensional data must be modified to account for Aspect Ratio where low AR achieves lowest angle of attack before stall 'break occurs'
For your question to have a neutral answer with respect to increase in span area (S), you must also increase the span (b) and chord MAC.
AR = same = S1/b1^2 = S2/b2^2
S2/S1 = 2 for double area; 2 = b2^2/b1^2; 2(b1^2) =b2^2
For Aspect ratio to remain same, b2= sqrt(2*b1^2).
For this stall condition velocity to remain the same, b2= sqrt(2) x b1.
For lower stall speed, increase the span/hold Wing Area (S1) same ---------> AR higher, CL vs alpha break point higher.
If you increase b by factor of 2 but hold Area S1 constant: AR1 = S1/b1^2; AR2 = S1/(2*b1^2); AR2/AR1 = S1/(2*b1^2)/[S1/b1^2]; AR2 = AR1*Sqrt 2) = 1.414 AR1
This condition will yield a higher break point and angle of attack (Higher CL) before stall and makes possible lower airspeed for same gross weight condition.
BTW - this discussion, that of section lift co-efficients, is why one May Not assume lower wing loading means better turn performance. Equally important for best constant altitude turn performance are 1.) Maximum CL vs angle of attack, 2.) Power Available vs Power Reqired, 3.) N load
for combat aircraft, such speeds are important - but even more important are the take off and landing roll distance to clear a 50 foot obtacle at either max gross weight or soe other designed load out - usually GWmax.And many times the whatever is the take-off and landing speed,
Or 20% more range/payload at the same take-off or landing speed.
A game type flight Sim is a classic example of KISS and having the same rules based on CLmax, Vmax for a turn at some defined N when THp avail=Thp required where simple assumptions like incompressible flow, parasite drag is supplied from available wind tunnel hisory, all dimenions 'validated' by Wiki lead to to calculations that can be extraced from a 1st year aero book or, say Aerodynamics for Naval Aviators'.I wonder how many flight sim games fail to recognize that last part?
I was lost at "square root of 2" but surely admire Bill's knowledge!Simon presented the fundamental relationship for your question. That said, for CL vs alpha, the stall point varies also by aspect ratio of three dimensioal airfoil sections. All Cl vs Alpha presented for airfoils in say, Abbott and Doenhoff, are for infinite span two dimensional wings with no tip effects. The two dimensional data must be modified to account for Aspect Ratio where low AR achieves lowest angle of attack before stall 'break occurs'
For your question to have a neutral answer with respect to increase in span area (S), you must also increase the span (b) and chord MAC.
AR = same = S1/b1^2 = S2/b2^2
S2/S1 = 2 for double area; 2 = b2^2/b1^2; 2(b1^2) =b2^2
For Aspect ratio to remain same, b2= sqrt(2*b1^2).
For this stall condition velocity to remain the same, b2= sqrt(2) x b1.
For lower stall speed, increase the span/hold Wing Area (S1) same ---------> AR higher, CL vs alpha break point higher.
If you increase b by factor of 2 but hold Area S1 constant: AR1 = S1/b1^2; AR2 = S1/(2*b1^2); AR2/AR1 = S1/(2*b1^2)/[S1/b1^2]; AR2 = AR1*Sqrt 2) = 1.414 AR1
This condition will yield a higher break point and angle of attack (Higher CL) before stall and makes possible lower airspeed for same gross weight condition.
BTW - this discussion, that of section lift co-efficients, is why one May Not assume lower wing loading means better turn performance. Equally important for best constant altitude turn performance are 1.) Maximum CL vs angle of attack, 2.) Power Available vs Power Reqired, 3.) N load
That's the kind of aeronauviating I can understand.I was lost at "square root of 2" but surely admire Bill's knowledge!
My method of testing stall speeds: play with the throttle and pitch angle, then try to remember what happens in each combination...
Course, one can't double the size of a wing without also considering that the wing will now weigh more.