Aerokid From Belgium, joined Jun 2000, 348 posts, RR: 0 Posted (14 years 4 months 1 week 4 days 13 hours ago) and read 9521 times:
This is an assignment I have do to for my aircraft design class next tuesday.
The question goes like this:
The Fokker 100 was derived from the Fokker 27. Major modifications include:
1) New "glass cockpit"
2) Streched fuselage
3) Modified wing, without developping a new wingbox
4) New engines (RR Tay Mk 620)
Off course they needed the wing to generate more lift, and by keeping the same wingbox the wingspan had to increase and at the same time the wing aspect ratio increased as well, off course.
Now the question is as follows:
What are the effects of the increased aspect ratio on the wing structure and the wing aerodynamics for the Fokker 100 and eventually for any other wing?
I already figured out that increasing the aspect ratio reduces drag until a ratio of about 12 or 13. From there drag increases again.
Concerning the structure, the increased wingspan requires a stronger and there for heavier wing in order to prevent the wing from bending too much.
Could you please give me as much info and points of view on this matter? Our teacher is really a smart guy and not satisfied with a short anwer. He really wants us to get really deep into this.
Buff From Australia, joined Mar 2007, 0 posts, RR: 1
Reply 2, posted (14 years 4 months 1 week 4 days 9 hours ago) and read 9500 times:
Don't think you're going to get any help here! Learning takes place as a collateral effect of research. You already have a handle on some of the fundamentals of your required answer. Why don't you just open a book (Mechanics of Flight) and study the math in there. You'll probably come up with a darn sight better answer than any of the responses you'd see here! With absolutely no disrespect to the talent that is here.
This is your project. You should do the homework. Not us! Don't you think?
Chdmcmanus From United States of America, joined Mar 2001, 374 posts, RR: 2
Reply 3, posted (14 years 4 months 1 week 4 days 9 hours ago) and read 9503 times:
I am not specifically familiar with the Fokker family, but there is another principal you may want to factor in to the relationship, fineness ratio. Aspect ratio is length and width; fineness ratio is the chord line to its maximum thickness. The biggest difference is that fineness ratio controls turbulence and skin friction. If the wing has a high fineness ratio, it is a very thin wing, but produces a high amount of skin friction ( a form of parasite drag), a low fineness ratio is a thick wing, but produces more turbulence (induced drag). The point is that there is a max performance number in there just like the 12-13 aspect ratio, so, better wing performance is a function of both. Don't forget also that aspect ratio is based on wing area, and wing are is the "shadow cast' measurement, not just "lifting area". The description above says that the fuselage length was increased; this will change the amount of airflow across the wing as the portion blocked by fuselage airflow changes (may be more or less, I don't know the design). What was the thrust, weight and fuel flow changes with the new engines? This may give you some room to play with for wing strength. Did they change the materials used in wing construction? If newer alloys and composites were used this will also change the strength / weight of the wing. A hidden resource for wing development information is the development of propellers, as much of the advances and research actually came from here, after all, they are just "little wings" right? Propellers have a much higher sensitivity to drag and speed based on engine power than wings sometime do. You may be able to find some helpful aspect ratio and fineness ratio info there. I'm sorry this wasn't type specific to the Fokker, but I hope it helps! Good luck on your research paper!