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Frequently Asked Questions (FAQS);faqs.480 ==> series/series.11.s <== V. Colors. ==> series/series.12.p <== A, T, G, C, L, ? ==> series/series.12.s <== V, L, S, S, C, A, P. Zodiacal signs. ==> series/series.13.p <== M, V, E, M, J, S, ? ==> series/series.13.s <== U, N, P. Names of the Planets. ==> series/series.14.p <== A, B, D, O, P, ? ==> series/series.14.s <== Q, R. Only letters with an inside as printed. ==> series/series.14a.p <== A, B, D, E, G, O, P, ? ==> series/series.14a.s <== Q. Letters with cursive insides. ==> series/series.15.p <== A, E, F, H, I, ? ==> series/series.15.s <== L, M, N, O, S, U. Letters whose English names start with vowels. ==> series/series.16.p <== A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, X, Y? ==> series/series.16.s <== Z. Letters whose English names have one syllable. ==> series/series.17.p <== T, P, O, F, O, F, N, T, S, F, T, F, E, N, S, N? ==> series/series.17.s <== T, T, T, E, T, E. Digits of Pi. ==> series/series.18.p <== 10, 11, 12, 13, 14, 15, 16, 17, 20, 22, 24, ___ , 100, 121, 10000 ==> series/series.18.s <== 10, 11, 12, 13, 14, 15, 16, 17, 20, 22, 24, 31 , 100, 121, 10000 Sixteen in base n for n=16, 15, ..., 2. ==> series/series.19.p <== 1 01 01011 0101101011011 0101101011011010110101101101011011 etc. Each string is formed from the previous string by substituting '01' for '1' and '011' for '0' simultaneously at each occurance. Notice that each string is an initial substring of the previous string so that we may consider them all as initial substrings of an infinite string. The puzzle then is, given n, determine if the nth digit is 0 or 1 without having to construct all the previous digits. That is, give a non-recursive formula for the nth digit. ==> series/series.19.s <== Let G equal the limit string generated by the above process and define the string F by F[0] = "0", F[n] = "1" if n = floor(phi*m) for some positive integer m, F[n] = "0" if n = floor(phi^2*m) for some positive integer m, where floor(x) is the greatest integer =< x and phi = (1 + \/5)/2; I claim that F = G. I will try to motivate my solution. Let g[0]="0" and define g[n+1] to be the string that results from replacing "0" in g[n] with "01" and "1" with "011"; furthermore, let s(n) and t(n) be the number of "0"'s and "1"'s in g[n], respectively. Note that we have the following recursive formulas : s(n+1) = s(n) + t(n) and t(n+1) = s(n) + 2t(n). I claim that s(n) = Fib(2n-1) and t(n) = Fib(2n), where Fib(m) is the mth Fibonacci number (defined by Fib(-1) = 1, Fib(0) = 0, Fib(n+1) = Fib(n) + Fib(n-1) for n>=0); this is easily established by induction. Now noting that Fib(2n)/Fib(2n-1) -> phi as n -> infinity, we see that if the density of the "0"'s and "1"'s exists, they must be be 1/phi^2 and 1/phi, respectively. What is the simplest generating sequence which has this property? Answer: the one given above. Proof: We start with Beatty's Theorem: if a and b are positive irrational numbers such that 1/a + 1/b = 1, then every positive integer has a representation of the form floor(am) or floor(bm) (m a positive integer), and this representation is unique. This shows that F is well-defined. I now claim that Lemma: If S(n) and T(n) (yes, two more functions; apparently today's the day that functions have their picnic) represent the number of "0"'s and "1"'s in the initial string of F of length n, then S(n) = ceil(n/phi^2) and T(n) = floor(n/phi) (ceil(x) is the smallest integer >= x). Proof of lemma: using the identity phi^2 = phi + 1 we see that S(n) + T(n) = n, hence for a given n either S(n) = S(n-1) + 1 or T(n) = T(n-1) + 1. Now note that if F[n-1]="1" ==> n-1 = floor(phi*m) for some positive integer m and since phi*m-1 < floor(phi*m) < phi*m ==> m-1/phi < (n-1)/phi < m ==> T(n) = T(n-1) + 1. To finish, note that if F[n-1]="0" ==> n-1 = floor(phi^2*m) for some positive integer m and since phi^2*m-1 < floor(phi^2*m) < phi^2*m ==> m-1/phi^2 < (n-1)/phi^2 < m ==> S(n) = S(n-1) + 1. Q.E.D. I will now show that F is invariant under the operation of replacing "0" with "01" and "1" with "011"; it will then follow that F=G. Note that this is equivalent to showing that F[2S(n) + 3T(n)] = "0", F[2S(n) + 3T(n) + 1] = "1", and that if n = [phi*m] for some positive integer m, then F[2S(n) + 3T(n) + 2] = "1". One could waste hours trying to prove some fiendish identities; watch how I sidestep this trap. For the first part, note that by the above lemma F[2S(n) + 3T(n)] = F[2*ceil(n/phi^2) + 3*floor(n/phi)] = F[2n + floor(n/phi)] = F[2n + floor(n*phi-n)] = F[floor(phi*n+n)] = F[floor(phi^2*n)] ==> F[2S(n) + 3T(n)] = "0". For the second, it is easy to see that since phi^2>2, if F[m]="0" ==> F[m]="1" hence the first part implies the second part. Finally, note that if n = [phi*m] for some positive integer m, then F[2S(n) + 3T(n) + 3] = F[2S(n+1) + 3T(n+1)] = "0", hence by the same reasoning as above F[2S(n) + 3T(n) + 2] = "1". Q.E.D. -- clong@remus.rutgers.edu (Chris Long) ==> series/series.20.p <== 1 2 5 16 64 312 1812 12288 ==> series/series.20.s <== ANSWER: 95616 The sum of factorial(k)*factorial(n-k) for k=0,...,n. ==> series/series.21.p <== 5, 6, 5, 6, 5, 5, 7, 5, ? ==> series/series.21.s <== The number of letters in the ordinal numbers. First 5 Second 6 Third 5 Fourth 6 Fifth 5 Sixth 5 Seventh 7 Eighth 6 Ninth 5 etc. ==> series/series.22.p <== 3 1 1 0 3 7 5 5 2 ? ==> series/series.22.s <== ANSWER: 4 The digits of pi expressed in base eight. ==> series/series.23.p <== 22 22 30 13 13 16 16 28 28 11 ? ==> series/series.23.s <== ANSWER: 15 The birthdays of the Presidents of the United States. ==> series/series.24.p <== What is the next letter in the sequence: W, I, T, N, L, I, T? ==> series/series.24.s <== S. First letters of words in question. ==> series/series.25.p <== 1 3 4 9 10 12 13 27 28 30 31 36 37 39 40 ? ==> series/series.25.s <== 1 3 4 9 10 12 13 27 28 30 31 36 37 39 40 ... i in binary, treated as a base 3 number and converted to decimal. ==> series/series.26.p <== 1 3 2 6 7 5 4 12 13 15 14 10 11 9 8 24 25 27 26 ? ==> series/series.26.s <== 1 3 2 6 7 5 4 12 13 15 14 10 11 9 8 24 25 27 26 ... Take i in binary, for each 1 bit (in i, not changed) flip the next bit. This can also be phrased in reversing sequences of numbers. More simply, just the integers in reflective-Gray-code order. ==> series/series.27.p <== 0 1 1 2 1 2 1 3 2 2 1 3 1 2 2 4 1 3 1 3 2 2 1 4 2 ? ==> series/series.27.s <== 0 1 1 2 1 2 1 3 2 2 1 3 1 2 2 4 1 3 1 3 2 2 1 4 2 ... Number of factors in prime factorization of i. ==> series/series.28.p <== 0 2 3 4 5 5 7 6 6 7 11 7 13 9 8 8 17 8 19 9 10 13 23 9 10 ? ==> series/series.28.s <== 0 2 3 4 5 5 7 6 6 7 11 7 13 9 8 8 17 8 19 9 10 13 23 9 10 ... Sum of factors in prime factorization of i. ==> series/series.29.p <== 1 1 2 1 2 2 3 1 2 2 3 2 3 3 4 1 2 2 3 2 3 3 4 2 3 3 4 3 4 ? ==> series/series.29.s <== 1 1 2 1 2 2 3 1 2 2 3 2 3 3 4 1 2 2 3 2 3 3 4 2 3 3 4 3 4 ... The number of 1s in the binary expansion of n. ==> series/series.30.p <== I I T Y W I M W Y B M A D ==> series/series.30.s <== ? (first letters of "If I tell you what it means will you buy me a drink?") ==> series/series.31.p <== 6 2 5 5 4 5 6 3 7 ==> series/series.31.s <== 6. The number of segments on a standard calculator display it takes to represent the digits starting with 0. _ _ _ _ _ _ _ _ | | | _| _| |_| |_ |_ | |_| |_| |_| | |_ _| | _| |_| | |_| _| ==> series/series.32.p <== 0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 1 ==> series/series.32.s <== 0 -> 1 01 -> 10 0110 -> 1001 01101001 -> 10010110 Recursively append the inverse. This sequence is known as the Morse-Thue sequence. It can be defined non-recursively as the nth term is the mod 2 count of 1s in n written in binary: 0->0 1->1 10->1 11->0 100->1 101->0 110->0 111->1 etc. Reference: Dekking, et. al., "Folds! I,II,III" The Mathematical Intelligencer, v4,#3,#4,#4. ==> series/series.33.p <== 2 12 360 75600 ==> series/series.33.s <== 2 = 2^1 12 = 2^2 * 3^1 360 = 2^3 * 3^2 * 5^1 75600 = 2^4 * 3^3 * 5^2 * 7^1 174636000 = 2^5 * 3^4 * 5^3 * 7^2 * 11^1 ==> series/series.34.p <== 3 5 4 4 3 5 5 4 3 ==> series/series.34.s <== The number of letters in the English words for the counting numbers. ==> series/series.35.p <== 1 2 3 2 1 2 3 4 2 1 2 3 4 2 2 3 ==> series/series.35.s <== The number of letters in the Roman numeral representation of the numbers. ==> trivia/area.codes.p <== When looking at a map of the distribution of telephone area codes for North America, it appears that they are randomly distributed. I am doubtful that this is the case, however. Does anyone know how the area codes were/are chosen? ==> trivia/area.codes.s <== Originally, back in the middle 1950's when direct dialing of long distance calls first became possible, the idea was to assign area codes with the 'shortest' dialing time required to the larger cities. Touch tone dialing was very rare. Most dialed calls were with 'rotary' dials. Area codes like 212, 213, 312 and 313 took very little time to dial (while waiting for the dial to return to normal) as opposed, for example, to 809, 908, 709, etc ... So the 'quickest to dial' area codes were assigned to the places which would probably receive the most direct dialed calls, i.e. New York City got 212, Chicago got 312, Los Angeles got 213, etc ... Washington, DC got 202, which is a little longer to dial than 212, but much shorter than others. In order of size and estimated amount of telephone traffic, the numbers got larger: San Fransisco got 415, which is sort of in the middle, and Miami got 305, etc. At the other end of the spectrum came places like Hawaii (it only got statehood as of about 1958) with 808, Puerto Rico with 809, Newfounland with 709, etc. The original (and still in use until about 1993) plan is that area codes have a certain construction to the numbers: The first digit will be 2 through 9. The second digit will always be 0 or 1. The third digit will be 1 through 9. Three digit numbers with two zeros will be special codes, ie. 700, 800 or 900. Three digit numbers with two ones are for special local codes, i.e. 411 for local directory assistance, 611 for repairs, etc. Three digit codes ending in '10', i.e. 410, 510, 610, 710, 810, 910 were 'area codes' for the AT&T (and later on Western Union) TWX network. This rule has been mostly abolished, however 610 is still Canadian TWX, and 910 is still used by Western Union TWX. Gradually the '10' codes are being converted to regular area codes. We are running out of possible combinations of numbers using the above rules, and it is estimated that beginning in 1993-94, area codes will begin looking like regular telephone prefix codes, with numbers other than 0 or 1 as the second digit. I hope this gives you a basic idea. There were other rules at one time such as not having an area code with zero in the second digit in the same state as a code with one in the second digit, etc .. but after the initial assignment of numbers back almost forty years ago, some of those rules were dropped when it became apparent they were not flexible enough. Patrick Townson TELECOM Digest Moderator -- Patrick Townson patrick@chinet.chi.il.us / ptownson@eecs.nwu.edu / US Mail: 60690-1570 FIDO: 115/743 / AT&T Mail: 529-6378 (!ptownson) / MCI Mail: 222-4956 ==> trivia/eskimo.snow.p <== How many words do the Eskimo have for snow? ==> trivia/eskimo.snow.s <== Couple of weeks ago, someone named D.K. Holm in the Boston Phoenix came up with the list, drawn from the Inupiat Eskimo Dictionary by Webster and Zibell, and from Thibert's English-Eskimo Eskimo-English Dictionary. The words may remind you of generated passwords. Eskimo English Eskimo English ---------------------------------+---------------------------- apun snow | pukak sugar snow apingaut first snowfall | pokaktok salt-like snow aput spread-out snow | miulik sleet kanik frost | massak snow mixed with water kanigruak frost on a | auksalak melting snow living surface | aniuk snow for melting ayak snow on clothes | into water kannik snowflake | akillukkak soft snow nutagak powder snow | milik very soft snow aniu packed snow | mitailak soft snow covering an aniuvak snowbank | opening in an ice floe natigvik snowdrift | sillik hard, crusty snow kimaugruk snowdrift that | kiksrukak glazed snow in a thaw blocks something | mauya snow that can be perksertok drifting snow | broken through akelrorak newly drifting snow | katiksunik light snow mavsa snowdrift overhead | katiksugnik light snow deep enough and about to fall | for walking kaiyuglak rippled surface | apuuak snow patch of snow | sisuuk avalanche =*= ==> trivia/federal.reserve.p <== What is the pattern to this list: Boston, MA New York, NY Philadelphia, PA Cleveland, OH Richmond, VA Atlanta, GA Chicago, IL St. Louis, MO Minneapolis, MN Kansas City, MO Dallas, TX San Francisco, CA ==> trivia/federal.reserve.s <== Each of the cities is a location for a Federal Reserve. The cities are listed in alphabetical order based on the letter that represents each city on a dollar bill. ==> trivia/jokes.self-referential.p <== What are some self-referential jokes? ==> trivia/jokes.self-referential.s <== Q: What is alive, green, lives all over the world, and has seventeen legs? A: Grass. I lied about the legs. The two rules for success are: 1. Never tell them everything you know. There are three kinds of people in the world: those who can count, and those who cannot. Xref: bloom-picayune.mit.edu rec.models.rc:11696 news.answers:4468 Path: bloom-picayune.mit.edu!enterpoop.mit.edu!eff!sol.ctr.columbia.edu!spool.mu.edu!olivea!sun-barr!cs.utexas.edu!rutgers!cmcl2!arizona!cs.arizona.edu!sham From: sham@cs.arizona.edu Newsgroups: rec.models.rc,news.answers Subject: R/C Flying: Part 1 of 2/rec.models.rc FAQ Summary: A Beginner's Guide to Radio Controlled Flying Message-ID: <27674@optima.cs.arizona.edu> Date: 7 Dec 92 15:00:10 GMT Expires: 18 Jan 93 15:00:08 GMT Sender: news@cs.arizona.edu Reply-To: shamim@cs.arizona.edu Followup-To: rec.models.rc Organization: Dept. of Computer Science, University of Arizona Lines: 398 Approved: news-answers-request@MIT.Edu Supersedes: <26083@optima.cs.arizona.edu> Archive-name: RC-flying-FAQ/part1 Last-modified: Aug. 24 1992 Greetings! This is the "Radio Control (R/C) Flying" help file, containing information of general interest to beginners. This file is posted regularly (every 28 days). I have tried to address all questions a beginner may have; if your question isn't here, please send it to me so I can include for the next person needing help. Remember, no amount of FAQ reading can substitute for an instructor! Shamim Mohamed shamim@cs.arizona.edu {uunet,cmcl2,noao..}!arizona!shamim ============================== Cut Here ====================================== Authors: W.A. - Wayne Angevine (angevine@badger.Colorado.EDU) G.H. - Gary Hethcoat (gdh@dobbs.Eng.Sun.COM) K.S. - Ken Summers (cs3871aa@triton.Unm.EDU) S.M. - Shamim Mohamed (shamim@cs.Arizona.EDU) Thanks to the following for comments and reviews: Dave Burritt (drb@druwy.Att.COM) Jeff Capehart (jdc@reef.Cis.Ufl.EDU) Warren R Carithers (wrc@cs.Rit.EDU) Carl Kalbfleisch (cwk@boomer.Ssc.GOV) Contents: -Part 1 General -- Organizations, radios -- (S.M.) Building -- Kits, ARFs and Scratchbuilding -- (S.M.) The rec.models.rc ftp site -- to get plotfoil, airfoil data, circuit diagrams &c. -- Learning to Fly -- Instructors, Pre-flight checks -- (S.M.,G.H.) Gliders -- Launching, Staying Up, Recommendations and Costs -- (S.M.) -Part 2 Power (gas) -- (G.H.,K.S.) Electrics -- Advantages, Equipment, Motor Specs., Recommendations -- -- (W.A.) Some Aerodynamics -- Speed, Turning, Stalls -- (S.M.) :::::: -- General -- :::::: >Should I start with powered flight, or with a glider? Depends on preferences. I prefer gliders; that's where I started. The 2m (6 foot wingspan) class is a good size---large enough to be easy to fly but small enough for easy transport. Gliders are easier to fly and more acceptable to the non-flying community---no noise or mess. Gliders are also cheaper (at least the trainers are) than powered planes---no fuel, batteries, starter etc. to worry about. Electric Flight is silent and clean so finds greater acceptance from neighbours etc. at the flying field, although some people feel that electrics are not robust/easy enough for beginners. There is a little more paraphernalia - you may need spare battery packs, but you can fly from smaller fields. Power will let you fly longer, and your model doesn't need to be as light as with electric (so it's likely to be easier to build); however, you may have to go to a field far from populated areas. The type known as "40 size" are the most popular, about 50" wing span and a .40 cu. in. engine. >Are there any organisations etc. I can join for information? Ask at your local hobby shop---there may be a club in your neighbourhood. This is the best way to meet other pilots and find an instructor. Most pilots will more than glad to help you out. If you can find a club, for an instructor, choose someone who is smooth in flying his/her plane and that you get along with. Remember, the ones best at flying (hangar or otherwise) may not always be the best instructors. An organisation well worth joining is the Academy of Model Aeronautics (AMA). They are the modellers' main voice where it matters---they liaison with the FCC, the FAA and Congress. It is an affiliate of the National Aeronautic Association (NAA) and is the US aeromodeling representative of the Federation Aeronautique Internationale (FAI). Membership in the AMA also gets you $1,000,000 of liability insurance, without which most fields will not allow you to fly. You also need to be an AMA member to participate in contests. Besides, you also get a magazine, `Model Aviation' which is rather good in itself, and it keeps you informed about the state of the hobby. So JOIN AMA!!! You can write to: Academy of Model Aeronautics, 1810 Samuel Morse Drive, Reston, VA 22090. Membership is $40 per year (and well worth it). Their phone number is (703) 435 0750. --- Radios: >Since a trainer needs only 2 or 3 channels, should I get one of the cheap > radio systems? Don't bother with the cheap 2 or 3 channel sets---get a 4-ch system. It will come with NiCad rechargeable batteries and (usually) 3 servos; this is the most popular and most cost-effective kind of system. You can put the main pitch control (elevator) and the main turning control (in this case the rudder) on one stick, which is how most people (and thus most instructors) fly. The cheaper systems come with the controls on separate sticks and you will have tough time finding someone willing to teach you with that setup. >What is a "1991" system? Strongly recommended! A "1991" system is so named because in 1991 the radio control frequency regulations changed, which effectively made the "old-style" radios unusable. The "old-style" radios have a separation between channels of 40 kHz. In 1991, a separation of 10 kHz will be needed, this even though R/C channels will still be 20 kHz apart---because the FCC in their infinite wisdom have created channels for pagers and such _between_ the R/C channels, i.e. 10 kHz away from our frequencies. The Airtronics VG4 FM series is an inexpensive example, and is about $120 mail order. If you can afford it, a system that has a "buddy box" is a really good idea. This is an arrangement where the instructor's radio is hooked up to yours, and he just has to release a button on his radio to take over control, rather than wrestling the radio from your grip. If you do this, be aware that you need to get the same (or compatible) radio as your instructor. :::::: -- Building -- :::::: >Should I start with plans and build my own plane from scratch, buy a kit >plane with wood and plans included, or go with one of those everything >included ready to fly planes. There are a few good trainers that are ready to fly (or almost ready to fly, aka ARF). ARF planes are usually heavy and hard to repair. The new generation of ARF kits is all wood and better built but more expensive. The better kits have parts that are machine cut, the somewhat cheaper ones are die-cut. You'll probably have to so a little more work with a die-cut kit, mostly in separating parts and sanding them. ARFs vs. kits: this is a matter of opinion, but more people seem to think that kits are a better idea for beginners. Pro kits: you get valuable building experience and are able to do repairs. Moreover trainers are good planes to learn to build as well as to fly, and most of them are cheaper than most ARFs. Pro ARFs: you can be flying sooner, and you have less emotional investment in the plane so when you crash you don't feel as bad. However: regardless of what you chose, your chances of a painless education are greatly improved if you have an instructor---both for building and for flying. Remember, the plane you buy doesn't have to be good looking, it just has to teach you to fly! Many pilots after building a beautiful model are so afraid to crash that they never fly. Far better to have a scummy looking plane that you don't mind crashing again and again and learning to fly than to have a slick model that you can only mount on a stand! After you are proficient you'll have plenty of time to build good-looking planes. It seems to be the general consensus that there are enough decent kits around that building from scratch is not really worth the effort unless you are into design or obscure scale models. If this is what you want, you may find the "plotfoil" program (available from the rec.models.rc ftp site and from comp.sources.misc archives) useful. Covering: for now, stay with Monokote. It's reasonably easy to apply, not too heavy, and fuelproof. (The label gives directions.) :::::: -- The rec.models.rc ftp site -- :::::: Nur Iskander Taib <ntaib@silver.ucs.indiana.edu> has been kind enough to establish an ftp site for the use of the rec.models.rc community. Use anonymous ftp to log in to "bigwig.geology.indiana.edu" and go to the directory called "models" . You will find subdirectories called "airfoil", "faq" and "circuits". These contain, respectively: plotfoil---a program to plot airfoil sections on PostScript printers. It can also draw spars and sheeting allowances, and can plot airfoils of arbitrary chords (on multiple sheets). It also includes a library of airfoil data, including many from Soartech 8. faq ---contains this FAQ file. circuits---circuit diagrams for modelling applications, including "smart" glow-plug drivers. Other FTP sources: Sometimes people have trouble getting to bigwig. Plotfoil is also available from comp.sources.misc, which is archived at many sites, including sites in France and Australia. Get Volume 31, parts 28-30 (archive name: plotfoil). Contact your sysadmin, or read the periodic posting in comp.sources.misc for more information on how to reach the nearest one. This FAQ is available from pit-manager.mit.edu, the news.answers archive. It is in /pub/usenet/news.answers/RC-flying-FAQ/part*. These two sources are guaranteed to be up-to-date, since it is all done automagically. :::::: -- Learning to Fly -- :::::: The most important point, one which cannot be overstressed: *GET*AN*INSTRUCTOR!* Here's what one beginner had to say: > I just started doing RC planes myself. In fact, yesterday I flew my > plane for the first time (with an instructor). He took off for me, > got the plane at a real high altitude and then gave me the controls. > I did OK (in my opinion) but did have to give him the controls twice > in order to get the plane into stable flight again. I figured the > controls would be sensitive but I did not realize HOW SENSITIVE. I > only had to move them about 1/8 of an inch to turn. > > There is no way I could have landed the thing without crashing. > > By the way I am a full scale pilot. That did not help me at all. > In fact I think it hurt. I didn't realize how much I use the "feel > of the plane" when flying a real one. Obviously you have no feel > whatsoever with RC planes. You probably won't have any really bad (i.e. irreparable) crashes. (Of course, you'll still crash.) Also make _sure_ you have your instructor check your plane thoroughly _before_ the first flight---as someone said, "it is much better to go home with no flights and one airplane than go home with one half a flight and many little pieces." This is really, *REALLY* important. --- Pre-flight Checklist --- When your model is ready to fly, make sure it is thouroghly checked over by someone who has done alot of building and flying. When I say thouroughly, I don't mean just picking it up and checking the balance and thumping the tires a few times. Every detail of setup and connection should be gone over in detail. If your instructor doesn't want to spend this much time checking your plane, find a new instructor. The importance of this pre-flight check cannot be overemphasized! Many planes are lost due to a simple oversight that could have been caught by a pre-flight! Here's a checklist: _Before_the_first_flight:_ 1) Weight ---is the model too heavy? 2) Balance ---Is the center of gravity (fore and aft) within the range shown on the plans? ---Is the model balanced side to side? (right and left wings of equal weight) 3) Alignment ---Are all flying surfaces at the proper angle relative to each other? ---Are there any twists in the wings? (other than designed-in washin or washout) 4) Control surfaces ---Are they all *securely* attached? (i.e. hinges glued, not just pushed in) ---Are the control throws in the proper direction *and* amount? (usually indicated in the plans) 5) Control linkage ---Have all linkages been checked to make sure they are secure? ---Are all snap-links closed? ---Have snap-links been used on the servo end? (They are more likely to come loose when used on the servo) ---Have all screws been attached to servo horns? 6) Engine and fuel (if applicable) ---Has the engine been thoroughly tested? ---Are all engine screws tight? ---Has the engine been run up at full throttle with the plane's nose straight up in the air? (To make sure it won't stall when full power is applied on climbout) ---Is the fuel tank level with the flying attitude of the plane? ---Is the carburetor at the same height (not above) as the fuel tank? ---Is the fuel tank klunk in the proper position and moving freely? 7) Radio ---Has a full range check been performed? ---Has the flight pack charge been checked with a voltmeter? ---Have the receiver and battery been protected from vibration and shock? ---Is the receiver's antenna fully extended and not placed within a fuselage with any sort of metallic covering? _After_repair:_ The checklist should be gone through again, with particular attention to the areas that were worked on or repaired.