<script>on mouseUpput the short name of this card into xTempput char 2 to 6 of xTemp & ".mov" into Movie--put Movieif Movie is not empty then-- put "Videos:WTN:" & Movie into pMovieplayMovie Movie,"Videos:WTN:"end ifend mouseUp</script>
</part>
<content>
<layer>background</layer>
<id>25</id>
<text><span class="style10">ircraft (6 of 7)2. How Aircraft Work</span><span class="style7"></span><span class="style10">Aircraft propulsion</span><span class="style7">Until 1939 virtually all airplanes were powered by piston engines driving a </span><span class="style19">propeller</span><span class="style7">, which provides thrust by accelerating air through aerodynamic rotating blades. Almost all modern propellers are of the variable-pitch type - the angle at which the blades attack the air can be altered. The blades are set to fine pitch for take-off to match high engine speed with low aircraft speed, and then automatically adjusted to coarse pitch for cruising flight, to match economical low engine speed to high forward speed. After landing, some propellers can be set to reverse pitch to help brake the aircraft.During World War II, engines grew rapidly in power. The Spitfire Mk I, for example, had a two-blade propeller, while the Mk XIV had five blades, in order to absorb the increased power within the limited available propeller diameter. Today some turboprop airliners have six-blade propellers, turning at relatively low speed for minimum noise.During and after World War II, the propeller gave way to the turbojet for most purposes. The turbojet itself was largely eclipsed by the turbofan, which offers better fuel economy and reduced noise levels.</span></text>
</content>
<content>
<layer>background</layer>
<id>23</id>
<text>ΓÇó ENGINESΓÇó AIRCRAFT 1</text>
</content>
<content>
<layer>background</layer>
<id>36</id>
<text>308348</text>
</content>
<content>
<layer>background</layer>
<id>26</id>
<text><span class="style10">ussia's latest jet fighter</span><span class="style7"> the SU-35 is shown in action at an air show in Kubinka Russia.</span></text>