Introduction to Aircraft Structural Analysis (Elsevier Aerospace Engineering)

384 CHAPTER 13 Airframe Loads

wherev 0 isthetouchdownspeed,visthefinalspeed(=0),andsisthelengthofdeckcovered.Then,

v^20 =− 2 as

thatis,

252 =− 2 (− 3 ×9.81)s

whichgives

s=10.6m

Example 13.2
Anaircrafthavingaweightof250kNandatricycleundercarriagelandsataverticalvelocityof3.7m/s,
suchthattheverticalandhorizontalreactionsonthemainwheelsare1200kNand400kN,respectively;
atthisinstant,thenosewheelis1.0mfromtheground,asshowninFig.13.5.Ifthemomentofinertia
oftheaircraftaboutitsCGis5.65× 108 Ns^2 mm,determinetheinertiaforcesontheaircraft,thetime
takenforitsverticalvelocitytobecomezero,anditsangularvelocityatthisinstant.

ThehorizontalandverticalinertiaforcesmaxandmayactattheCG,asshowninFig.13.5,misthe
massoftheaircraftandaxandayitsaccelerationsinthehorizontalandverticaldirections,respectively.
Then,resolvingforceshorizontally

max− 400 = 0

fromwhich

max=400kN

Nowresolvingforcesvertically

may+ 250 − 1200 = 0

Fig.13.5

Geometry of the aircraft of Example 13.2.