update

20240507.md

@@ -52,6 +52,11 @@ Parasitic drag: for example "form drag" caused by the shape of the plane as it h
 Lift-induced drag: caused as part of generating lift (e.g. Newton's 3rd law: when you increase your angle of attack
 your lift vector isn't straight up, it has a component pointing backwards; also something to do with Bernoulli's principle).
 
+The engine can rev up to 5800 rpm but in this instance it is "pitch-limited" which means it runs out of power before that point,
+because of the load created by the pitch of the propellor blades. The blade pitch is ground-adjustable, but you're not allowed
+to adjust it because it is set to a spec that is approved for noise control and changing the pitch changes the amount of noise it makes,
+in particular if you let it spin too fast then the tips can break the speed of sound which makes a loud noise and breaks people's windows.
+
 ### Exercise 3: preparation for flight and action after
 
 Before starting you want both ignition switches off, crank it for 5 seconds. Then turn both ignition switches on, choke on (or was choke