Part 2 of “Aspects of Aircraft Design and Control”

Lec­ture 2 — Run­way performance
Project 2 — Run­way performance

This lec­ture focus­es on the tools and knowl­edge required to study and pre­dict an aircraft’s per­for­mance on take-off. The project’s aims were to prac­tice ana­lyt­i­cal tech­niques in New­ton­ian mechan­ics by work­ing on an applied and high­ly visu­al aero­nau­ti­cal prob­lem, and to gain famil­iar­i­ty with the com­plex oper­a­tional con­cepts involved in a typ­i­cal air­lin­er take-off.
It was by far the most inter­est­ing and dif­fi­cult project of all. It met only very mod­er­ate success.

The lec­ture, I believe, had merit.
The first part (“Prob­lem-solv­ing tools in mechan­ics”) focused on two tech­niques for solv­ing New­ton­ian mechan­ics prob­lems — but I lost many stu­dents in this chap­ter by not giv­ing detailed con­crete exam­ples of their use. It is under­stand­ably hard for a third-year stu­dent to be attract­ed by a sec­tion titled “Newton’s sec­ond law”! In the in-class project ses­sion that fol­lowed, I end­ed up com­ing back mul­ti­ple times to points I brought up in this chap­ter but that were sim­ply over­looked. So this sec­tion will need re-work.
The sec­ond part (“Def­i­n­i­tions”) was sat­is­fac­to­ri­ly suc­cinct and clear.
The third part (“A take-off”) was frankly good. I took the approach of explor­ing the impor­tant flight mechan­ics con­cepts at play dur­ing a take-off by nar­rat­ing an imag­i­nary one. This was ter­rif­ic fun. I also like my way of tack­ling the notion of Bal­anced Field Length.

The project was split in two parts. The first one, a pure­ly in-class ana­lyt­i­cal exer­cise, took too long. I blame the lack of per­spec­tive and appeal of the lecture’s first chap­ter for that: I should have giv­en exam­ples, as well as real hints towards how to start when stuck. Hope­ful­ly and if any­thing at all, the exer­cise was an effec­tive demon­stra­tion of the some­times immense dif­fi­cul­ty of com­ing up with the rather triv­ial math­e­mat­ics that describe ordi­nary problems.

As for the sec­ond part, the only word that comes to mind to describe it is “epic”. To be frank, I feel it was extreme­ly good, in that it pro­vides a good frame­work for true learn­ing: con­cep­tu­al­iz­ing new notions (V1, the Bal­anced Field Length, Rota­tion, etc) instead of hav­ing them fall from the sky, and solv­ing a chal­leng­ing, real­is­tic problem.

In prac­tice, the stu­dents had great dif­fi­cul­ties with that part. Not only is there no obvi­ous path to a solu­tion, but one is also forced to make sim­pli­fi­ca­tions and esti­mates if s/he is to obtain any result at all. This clash­es spec­tac­u­lar­ly with the learn­ing pat­terns and habits with­in the school. I made sev­er­al mis­takes in hand­ing such a chal­leng­ing project.
First and fore­most, I should have invest­ed more effort in describ­ing prob­lem-solv­ing tech­niques. In par­tic­u­lar, we are used to pro­ceed “from the top down”, work­ing our way from an all-encom­pass­ing, most-gen­er­al heavy math­e­mat­i­cal expres­sion down to a spe­cif­ic appli­ca­tion case. By con­trast, in such cas­es it is much more effi­cient to work “from the bot­tom up”, start­ing from a dum­my, extreme­ly-sim­pli­fied case, and grad­u­al­ly adding lay­ers of com­plex­i­ty whilst mon­i­tor­ing the san­i­ty of the calculations.
Sec­ond, I mis-man­aged our ener­gy dur­ing the ses­sion and with­in the course. We were only able to get in the heart of this project very late in the 6- or 7‑hour ses­sion, which makes for an un-wise con­text for hard-core think­ing. The project came too ear­ly with­in the course, the ses­sion was slight­ly over­loaded, and then too much was left for the stu­dents to do by them­selves afterwards.
By then, the stu­dent team­work and work plan­ning issues that I described in the back­ground remarks on the course had ful­ly kicked in.

The result was that the class, whose gen­eros­i­ty and moti­va­tion keep amaz­ing me year after year, threw in tremen­dous amounts of effort and ener­gy into the project with­out most stu­dents obtain­ing mean­ing­ful cal­cu­la­tions, sat­is­fy­ing results, and indeed, much moti­va­tion feed­back. That is hard­ly a suc­cess­ful learn­ing expe­ri­ence and I feel that most of the respon­si­bil­i­ty for miss­ing this oppor­tu­ni­ty is mine. Many improve­ments come to mind for next time with­out mod­i­fy­ing the core. Great project, per­fectible implementation.