Why all the 2 dimensional thinking?
The point surely is that we adjust the "performance" to match what is required.
If one is flying a glider down the ILS, one would use attitude to control the speed and accept whatever rate of descent that resulted.
If the glider is too fast, we raise the nose, reduce the rate of descent and thus reduce speed.
If the glider is too slow then the only option available is to lower the attitude to regain speed. That may result in the aircraft descending below the glide slope but withour power, there is nothing we can do to avoid this.
Thus in the glider we have full control over speed but in the absence of power, must accpet the rate of descent that a particular airspeed gives.
That is not the full story........... with reference to the drag curve, we can see that flying at a speed for minimum drag with give us minimum rate of descent. If we fly the approach at say 10Kt above the min drag speed, we now have some adjustment over the rate of descent.
If the aircraft is going high on the glide slope, we lower the nose slightly to add 10 Kt onto the airspeed. This increases the drag and thus our rate of descent increases. Once back on the glideslope, we return to our original performance and slide nicely down the slope.
If the aircraft is going low on the glideslope, we raise the nose slightly to reduce the speed by 10Kt. This reduces the drag and thus with a lower rate of descent we regain the glideslope.
Have I mentioned power yet? No
This is one method of flying the ILS.....accept the speed moving either side of the approach speed by a certain amount.
Now back in a powered aircraft approach at a constant airspeed.....if the speed is right but the aircraft moves above the glide slope.......what is wrong?....answer....the rate of descent is too low......How does one adjust the rate of descent without adjusting the speed.........answer reduce to power.....but remember that in order to retain the speed at the new lower power setting, the attitude must be lowered slightly.
Thus with a stable airspeed, we never adjust power or attitude in isolation.
So to recap, we are adjusting the performance of the aircraft in order to match the performance required to follow the ILS.
Power + Attitude = Performance.
Now no matter what camp one sits in.....power for speed...or power for rate of descent.....it does not matter because in both cases, the pilots are operating the controls in the exact same way to obtain the exact same performance from the aircraft. The only difference is in how they "think" that they are acheiving the result.
Moggie,
If one is nicely settled on the ILS with the speed and power correct, provided that the attitude is correct for the rate of descent then the aircraft will fly down the glide path perfectly.
However, one will have a sore arm if the aircraft is not in trim from constantly pushing or pulling to keep a steady attitude.
Adjust - HOLD - Trim.
The trim does not fly the aircraft.....it simply reduces the control forces. That applies to every type
DFC