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# Advanced Math/Retractable mechanism for Landing gear in airplanes.

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Question
Dear Prof Scott

en.wikipedia.org/wiki/Landing_gear

Are the Landing gears always retractable in all airplanes ?.

i.e.

Once the airplanes takes off, the front and rear wheels are always
folded ?.
Once the airplanes wants to Land, the front and rear wheels are unfolded ?.

What are the Pros and Cons with and without having these retractable mechanism for Landing gears in airplanes ?.

Once the commercial airplane takes off by what time the front and rear wheels are folded ?. i.e. after 1/2 min, 1 min, 5 min, 10 min etc ....

Once the commercial airplane has to land before what time the front and rear wheels are unfolded ?. i.e. within 1/2 min, 1 min, 5 min, 10 min, 30 min etc ....

Are both these timings critical i.e. After plane take of and Before Landing and are these timings fixed globally as part of airplane operations ?.

Thanks & Regards,
Prashant S Akerkar

Answer
All aircraft have some type of landing gear, as seen in
www.faa.gov/.../handbooks_manuals/aircraft/amt_airframe_handbook/media/ama_Ch13.pdf

Occasionally, the landing gear doesn't work right, as can be seen in
www.wimp.com/landinggear/  Was that a miraculous save, or what?

Landing gear can sometimes be a good place to hide, as in
www.askthepilot.com/lucky-stowaway ,
but at other times, the landing gear can be quite deadly, as seen in
time.com/3053012/air-force-boy-landing-gear/

Currently, if the airplane is small, the landing gear is not retractable, but that does increase the fuel needed.  To make it retractable on small aircraft, however, is usually
too expensive to do.

Larger aircraft need to travel at such amazing speeds that if the landing gear were not retractable, the plane would need to land a whole lot sooner and not be able to achieve the speeds that they currently do.  Since they are so large, landing gear can be made.  Since they are used to make money, and time is money, not putting it in would cost too much.

Now my questions are usually in math, but I don't see any here besides the physics of drag.
Since this is a mathematical question place, the main paper to read is
ffden-2.phys.uaf.edu/212_fall2003.web.dir/Will_Salzman/

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#### Scott A Wilson

##### Expertise

I can answer any question in general math, arithetic, discret math, algebra, box problems, geometry, filling a tank with water, trigonometry, pre-calculus, linear algebra, complex mathematics, probability, statistics, and most of anything else that relates to math. I can also say that I broke 5 minutes for a mile, which is over 12 mph, but is that relevant?

##### Experience

Experience in the area; I have tutored people in the above areas of mathematics for over two years in AllExperts.com. I have tutored people here and there in mathematics since before I received a BS degree back in 1984. In just two more years, I received an MS degree as well, but more on that later. I tutored at OSU in the math center for all six years I was there. Most students offering assistance were juniors, seniors, or graduate students. I was allowed to tutor as a freshman. I tutored at Mathnasium for well over a year. I worked at The Boeing Company for over 5 years. I received an MS degreee in Mathematics from Oregon State Univeristy. The classes I took were over 100 hours of upper division credits in mathematical courses such as calculus, statistics, probabilty, linear algrebra, powers, linear regression, matrices, and more. I graduated with honors in both my BS and MS degrees. Past/Present Clients: College Students at Oregon State University, various math people since college, over 7,500 people on the PC from the US and rest the world.

Publications
My master's paper was published in the OSU journal. The subject of it was Numerical Analysis used in shock waves and rarefaction fans. It dealt with discontinuities that arose over time. They were solved using the Leap Frog method. That method was used and improvements of it were shown. The improvements were by Enquist-Osher, Godunov, and Lax-Wendroff.

Education/Credentials
Master of Science at OSU with high honors in mathematics. Bachelor of Science at OSU with high honors in mathematical sciences. This degree involved mathematics, statistics, and computer science. I also took sophmore level physics and chemistry while I was attending college. On the side I took raquetball, but that's still not relevant.

Awards and Honors
I earned high honors in both my BS degree and MS degree from Oregon State. I was in near the top in most of my classes. In several classes in mathematics, I was first. In a class of over 100 students, I was always one of the first ones to complete the test. I graduated with well over 50 credits in upper division mathematics.

Past/Present Clients
My clients have been students at OSU, people who live nearby, friends with math questions, and several people every day on the PC. I would guess that you are probably going to be one more.

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