In some cases, a human pilot would be incapable of reacting fast enough to safely fly the plane if the automated controls fail. Inherently unstable aircraft are a bad idea (especially near the ground) unless there is some automated control system that is very rapid and very reliable. On the other hand, the pilot or other control system must always actively fight to keep the plane rightside-up. The tendency of the plane to invert itself can give it an advantage in maneuvers that require rapid rolling. If, however, the wings have too much effective anhedral (negative dihedral), the airplane will continually try to roll itself inverted. Basically, if there is sufficient inherent stability the airplane will automatically return to flying upright. It includes both the center of gravity and effective dihedral. The mention of inherent stability is important.
#LAMINAR FLOW AIRFOIL FULL#
Your source is technically correct, but as is often the case, the full answer is more complicated. I have lost the link, but you can find it by searching for "NASA sp-468."
#LAMINAR FLOW AIRFOIL DOWNLOAD#
pdf book (500+ pages) that you can download for free. There is a section (Chapter Five) in the NASA document sp-468 "QUEST FOR PERFORMANCE The Evolution of Modern Aircraft" that has a good discussion of the actual performance of early production laminar-flow wings vs. The designers had no way to test for this, so these high-speed characteristics were a very fortunate accident. Remember that the P-51 was designed before much was known about compressibility (airflow at or near the speed-of-sound). This allowed it to dive faster than most planes while staying in full control. The main (unanticipated) advantage of the P-51's "laminar-flow" wing is now well known: it delayed the effects of compressibility, giving the plane a high critical mach-number. In my opinion, this made all the difference. Luckily for the P-51, the British had the better performing merlin engine to use in it. My guess is that the wing performance was well below predicted. You might recall that the original P-51's performance was good, but not spectacular. I can't imagine what they (or their bosses) did when the actual performance was very much less than predicted. I actually feel very sorry for the design teams that used the wind-tunnel data in their performance calculations. It too showed extremely low drag in the wind tunnel, but not in the production aircraft. The first article that you mentioned also mentioned the "Davis wing" that was used on the B-24. This might explain some of the P-51's handling characteristics.īoy, do I feel better now that I got that off my chest! the stall characteristics of some laminar-flow wings became very ugly (abrupt) when the laminar boundary was disturbed. Similar stories exist about sailplanes that happened to fly into a small cloud (swarm?) of gnats or other insects. The water droplets "tripped" the air boundary layer from laminar to turbulent - increasing the wing drag and drastically reducing the glide ratio. There are stories of sailplanes landing miles short of their landing strips because they encountered some mist or rain. Even on these high-performance sailplanes, laminar flow could be lost from something as minor as a few bug-hits on the leading edge. In fact, until recently, high-performance sailplanes were about the only "production" aircraft to actually have extensive laminar flow over their wings. Extensive laminar flow is extremely difficult to achieve and requires incredibly exact tolerances and smoothness to achieve. Yup, it is true that the P-51's wing did not have any significant laminar flow. I studied aeronautics in college and even had a part-time job at a windtunnel, so the continual references to the P-51's "laminar-flow airfoil" has been a sore point for me. OK, this thread finally got me to join the forum.
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