Pilot H wrote:Perhaps I didn't explain clearly enough.
Appreciate your coming back to elaborate
One of the biggest killers in the history of aviation, and one which refuses to go away, in is an inadvertent stall/spin at low altitude, usually this is the base to final turn. Often if the turn is overshot, the stall/spin happens when trying to re-align with the runway. But really anytime the aircraft is low and slow, the need to apply back pressure should be something which lights an amber warning in the mind.
Absolutely.
I am not advocating anything radical, trimming should be done wings level for a particular airspeed.
Phew... I can wind my neck in
All I am saying is that if the aircraft is trimmed for a particular speed on a base leg final in the descent, then as you bank you should be conscious that you are in the corner of the angle-of-attack envelope, and too low to recover if you were to stall/spin. So build in the ability to recognise pulling back on the stick as a threat.
Very much agree with this too.
.....The aircraft is already yaw/roll coupled and right in the corner of the envelope. Then, while still holding back pressure, the airrcaft is rolled the opposite way, to line up with the runway. The down going aileron adds the final kick.
Yep.
So, to avoid being in a situation where you are banking and pulling, always trim for the correct base to final speed, and if you feel any back pressure, gently (the word is gently) unload it as you roll into a turn.
Build muscle memory so that it feels just "wrong" to be holding any back pressure in the base to final turn.
This is where we diverge a bit (my bold).
Consider a level turn. Assuming you start trimmed from straight and level, some back pressure is needed as you roll into the turn, and it needs to be held in order to remain level in the turn. This is because you need enough extra alpha to ensure that the vertical component of the lift is still equal to the weight.
At constant rate of descent (eg trimmed on base), the aircraft is not accelerating vertically. So the upwards forces still balance the downwards ones*. So just as in a level turn, the descending turn on to final needs some some back pressure to maintain that constant rate of descent, and for the same reason. If you don't add back pressure in the turn, the rate of descent will increase, just as it would in a level turn.
Now of course, base leg is a 1G manoeuvre, flown significantly slower than cruise. So of course if you're rolling into the base-to-final turn you need to be more careful as you're closer to the stall than in the cruise.
I know you know all this stuff, but I think it's wrong to build the expectation that turning on to final should involve
no additional back pressure as you turn.
The point is that it shouldn't involve
too much. Rather than teaching people bad descending turn technique, it would be better to tell people that aren't able to feel the difference between 'just enough' and 'too much', to limit their angle of bank to 15 degrees in the base-to-final turn, and to go around if they aren't going to get back to being lined up.
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* up = vertical components of lift and drag; down = weight, plus downward component of thrust.