14.19 How do the stick and the throttle control airspeed and altitude?

From FlightSim

If I may take the liberty to interpose my few cent's worth on the dictum : -

Stick controls the ............airspeed
Throttle controls the..........altitude.

The above is aerodynamically true but on ILS etc we follow different proc. like it is mentioned above.

Basically, as we all know, in level flight Weight=Lift and L = C.q.S where C the lift coeff depends on angle of attack, q the dynamic pressure at the same altitude depends on IAS and S is the surface area of lifting surface.

In short, level flight is sustainable at the same alt, at different specific combinations of angle of attack and IAS.

Now at same altitude and ang of attk , if we increase thrust/power the total lift in eqn L=C.q.S increases and the a/c will start to climb. The reverse takes place if we reduce thrust/power. Hence the saying that thrust controls altitude or rate of descent in approach.

Similarly, at same altitude and thrust, if we increase the angle of attack the drag increases and since thrust same, the IAS drops. So, Change in angle of attack, by using the yoke increases or decreases the IAS. So, the saying that the stick controls the speed.

That is the aerodynamics of it equally applicable to both prop/jet a/c.

The major point here is that is at steady state condition while in the transient stages so many factors like what both have you mentioned come into play. To follow the stick to speed & thrust to ROD (rate of descent) proc safely we need angle of attk indicators or FPV (flight path vectors) like in the fighter a/c of the milsims USNF/ATF etc. My carrier landings are limited to USNF& ATF but you can fly there, an F-22 at as low a speed as 86 kt controlling the speed with stick and adjusting the ROD with throttle adjustments and land on the carrier. Any real-time naval aviator may be able to shed more light on this subject.

But, coming to ILS intercept under bad weather conditions in the absence of angle of attk ind/ FPV etc and also considering the fact that heavy transport a/c are designed to have more stability than controllability, It is prudent to lower the nose at ILS intercept point and as the spd increases reduce thrust/power. From now on, we are maintaining a descent ANGLE rather than a rate of descent which will vary. As such an optimum angle of attack in relation to the glide angle is maintained by the stick. In doing so if the speed increases/decreases thrust/power is varied to keep the desired speed. The catchword here is that we are maintaining an angle with the stick and hence the IAS has to be controlled by the thrust/ power regardless of the fact whether it is a jet or Prop a/c.

If we are not required to maintain a particular descent angle to a particular touchdown point we could have followed the other method.

Bala