What Planes?

Comment

Comment by Dennis Cimino on October 20, 2011 at 1:21am

wake vortices are a by product of lift generation on a wing or airfoil.  sailboat sails make them, as do airplane wings generate them.  a wingtip vortice typically manifests itself fully at approximately half a wingspan distance above the ground, and those neat winglets you see on most of the newer jet aircraft are there to delay the generation of them, because the vortice is pure drag incarnate.  in low altitude, moisture laden dense air, they can usually be seen as the pressure drop in the densely laden with moisture air condenses and forms a visible vortice vapor trail from the wing tips.  in any case, at approximately 700 feet above terra ferma, where these planes were at just prior to impact, it's hard to know if their wingtip vortices would be discerned easily as they flew into the towers.  I don't know what the R.H. and temp/dewpoint in New York was at Republic Airport or JFK or LaGuardia that day but I could probably find that out and tell you what I think about the lack of them that day.  but virtually any airplane watcher who's hung out on a humid day and watched planes taking off or landing, has seen them.  They are very easy to spot when high performance fighter jets change AOA suddenly (angle of attack) in moisture laden, dense air down low.  And, a plane's vortice is directly a derivative of the gross weight of the plane, and lift generation co-efficient to sustain flight at whatever speed the plane is at at any given moment in time...hence the F.A.A. uses the term 'HEAVY' for any aircraft above 180,000 pounds takeoff weight and higher to warn other pilots who are behind them or possibly to cross paths with where these planes are, of the potential for extreme wake turbulence.  the heavier the plane, the more nasty the wake is.  experienced pilots will typically fly their departure climbout behind a prior departure just a bit to the upwind side and higher, and when behind, the same way if at all possible, to stay out of these wakes.  I have found that in winter months that wake turbulence from an airplane can last much much longer than the tower controller thinks, and will put you in the danger zone where the other plane was, for much longer periods of time than in summer months, due to the less dense air in summer weather.  extremely cold, dense air is the max danger zone in winter flying and the old 5 mile rule sometimes is not good enough.  One of these days guys like me will build systems that will allow the crews to see that turbulence on their PVD's in the cockpit, assuming that aviation survives this global collapse, which it may not.  All of the air carriers are bleeding red ink right now, due to the TSA bullshit and the fact most people can't afford air travel any longer, or avoid it due to the wholly ridiculous; "may I play with your nutsack" or "finger your vagina, mam?" shit the TSA is doing.  in any case, down low, in moisture laden air, virtually any severe AOA change will make these vortices pretty noticeable.  Most of you no doubt have seen them.  and they are a REAL DRAG (coefficient).