View Full Version : Aerodynamic Misconceptions

12-06-2005, 02:59 PM
have read one or two misconceptions as to why aircraft act in certain flight conditions.
1.An a/c at the stall point will roll in a direction that is relative to the rudder position as indicated by the ball in a slip /skid indicator. The inside wing does not normally stall first, it stalls first only if too much rudder is applied, pushing the ball too the high side of the a/c (skidding).
In a correctly co-ordinated turn (ball centered)
the high wing will stall first upon application of sufficient stick back pressure, the a/c
will roll level.This is called an accelerated stall.(a/c stalls at higher speed in than level flight.)Prop. rotation has nothing or very little to do with this condition.

Some very high Horse Power A/C ie. Mustang, have insufficient rudder authority at low speeds
to counteract a condition known as "torque roll"
ie. upon application of rapid throttle on intial roll out, accompanied by premature lift
off a Mustang will attempt to "roll around the engine". Rudder and ailerons are ineffective at low airspeeds. Quite a few training accidents attributed to this.
Allowing some a/c to get too slow, before applying rudder, in a "hammerhead" manoeuver will put you in a torque roll condition.
Constant speed props do require the pilot to set the RPM each time by referencing the tach. and adjusting the setting by a knob or lever. Some earlier WW2 a/c ie.Russian,and early spitfires had only ground adjustable props on which the blades had to be hand set for either fine or coarse pitch.(fine for good climb, coarse for max cruise speed but poor climb)
Best approach speed for any a/c is 1.3vso or 30% above level flight stall speed, which varies with a/c weight.ie. an a/c will stall at a higher airspeed when loaded than when it is low on fuel and ammo. An A/C will stall at a much higher than "normal" airspeed when in a high G turn. (accelerated stall.)
Which way the prop turns is only significant on multi engine a/c.On take off you just have push the appropriate rudder to keep the a/c straight.
A quart of "clean" a/c oil on your wind shield can completely blind you, even at high cruise.!