I’ve noticed in the Sim, when manually trimming for descent, let say 500 fpm, the plane will begin to descend at that rate and after about 10 seconds or so, level off. I’m thinking the aircraft is picking up speed which increases lift and that offsets the elevator trim? Should I backing off the throttle too? I’m trying to maintain a steady vertical speed and not a series of swoops like a paper airplane landing. Thanks!
Pitch for speed, throttle for altitude.
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Either that or you will have to increase the amount of negative trim to compensate. But if you do just increase the amount of negative trim, the speed could very quickly build up too much.
Depends on what you are flying, but IRL with single engine piston aircraft, when I was descending I would trim down and adjust throttle to allow the speed to build up to where I am comfortable (below the yellow zone!) at the rate of descent I wanted. When you are familiar with the aircraft you will get to know what settings will give you what speed and descent rate. And then (more so with a non turbo piston single), you will have to continuously reduce power because i) the manifold pressure will increase as you descend and ii) the Indicated Airspeed will increase as you descend.
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Sounds like it’s picking up speed, which means it’ll pitch back up and level off. Did you ease off on the throttle first?
Exactly. You got it! 
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APT-PAT
When climbing set Attitude, then Power, then Trim once stabilized. When descending set Power, then Attitude, then Trim once stabilized.
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To start a proper descent, you don’t have to touch the trim. An aeroplane is trimmed for airspeed, so if you want it constant, you shouldn’t change the trim. Instead, reduce power by a small amount and then upon reaching the desired rate of descent gently counter any possible oscillations with the yoke or control stick.
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It help a lot if you know the power setting for your planes, for a given decent, so you are not constantly searching for the right power settings, Comes with practice and familiarity with your given plane .
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If you were already flying trimmed for level flight, you do not touch the trim wheel at all.
Simply reduce throttle and watch your VSI … then either back the throttle off a little more or put a little power back in … to get the rate you want or need.
To level off, at pattern altitude for example, you simply go back to the power setting your were at in the beginning….the airplane should level off and hold that altitude.
Do it smooth enough and you don’t have to touch anything but the throttle, but since air is generally not 100% homogeneous…you will need to correct small deviations with the control column.
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Thanks all - this is very helpful! I was definitely doing things wrong (using trim as primary control). So, allow me a follow-up question: at what point in the approach/descent should I apply flaps? At TOD or along the descent as long as I adjust for VS with throttle? This would be for a single-engine GA plane like a 172.
Usually, you apply 10º flaps when on downwind abeam the numbers, 20º after turning base and full flaps when on final. On a Piper, you can delay this until final and then extend all flaps at once since on Pipers flaps don’t perturb trim speed as much, but it’s more convenient to do it in stages. I’m referring to the standard traffic pattern (circuit) here.
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IRL, on final I am using throttle and pitch only. I don’t mess with trim, now that may be unique to my aircraft. my 152 does not require very much trim ever in flight. I have noticed low wing guys in thier pipers using a ton of trim on landing, however, I can not speak to that. One other note, I am not looking at decenst rate on final, just making sure my speed is 100% where it needs to be and my sight picture of runway remains constant, and if there are VASI or PAPI lights I am maintaining above glideslope
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Standard technique in low to no wind. 1. on downwind turn on carb heat in fial 1/4 of runway. 2. when you beam to numbers, drop your RPM to 1700 and get into flap speed. once in flap speed prior to base turn 10 flaps. on base 20 flaps on final 30-40 flaps. If there is higher wind or wind gusts don’t use flaps or never exceed flaps 10. Take a look at this video https://www.youtube.com/watch?v=KIjW1Jr4a4M
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For Cessna 172 (and it’s applicable to the C152 too), we would keep the flaps clean until turning base.
Reduce to 1500RPM with the carby heat out if yours is a non-fuel injected model.
Set 20 degrees of flap as you turn and keep the nose up to wash off speed.
Once your speed is back lower the nose slightly to maintain your airspeed and trim back 3 wheel movements, top to bottom.
On the final turn remember to keep your nose at this lower attitude to maintain your speed.
Once on final the runway should be sitting about 3 finger widths above the dash.
I have over 2000 hours instructing on C152 and C172 aircraft.
Remember that most aircraft (especially a Baron and bigger) really use pitch for attitude, and power for speed. That works for the smaller aircraft as well, but is harder to teach, hence why flying schools use the above method.
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Lot’s of pros helping out. Very nice. Very eloquent.
Now for sone simmer to simmer advice: once you have a good visual with the runway and you feel you got a quick gap to plummit your aircraft towards it if only you can struggle to keep it ligned up long enough: at about 2500 feet above the ground, pull back on your throttle and move your flaps out to the APP position. As you slow down quite quickly, throw out that landing gear too. Then at around 90 knots, soaring towards that runway now, you feel the drag slowing you down and down. Hit that flap lever again, quickly settle back some.engine power and pray to god youre nailing it. Have fun mate. It will get second nature over time.
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Glad to see you added that… as I read the prior post in this thread, that was something I was going to add.
(You save me the typing – thanks)
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lol – and if you don’t, in the sim, you live to try it again the next time.
Practice, (either) makes perfect,
or
(in the sim), can re-enforces bad habits !
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Many years ago, on a PPL renewal with an instructor that I had never flown with before, I was shown a very neat trick with a C172. As a desperate last ditch measure if you get stuck above cloud without a hole anywhere and you are not IF competent and running out of fuel: throttle to idle, elevator trim as far back as it can go… and let go of everything! The aircraft gently and slowly spirals down at less than 1,000FPM and <50kts if I recall the numbers correctly. I do suppose this presupposed that the aircraft is rigged well. With those numbers you have a good chance of surviving if the clouds are all the way down to the ground and you hit the solid stuff. Haven’t tried it in the sim yet but I would be surprised if that is modeled correctly
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If your set up right and there is minimal crosswind you should be able to pretty much grease a landing with just throttle and rudder.
Rudder (and the resultant adverse or dutch roll) will give you a lot better and safer directional control at low airspeed then banking.
In MSFS
38 % trim, 80 Knots 500-1000 ft.min in a shallow spiral, once it finally stabalizes !!! Close enough, but unless trim is right, its a spiral to death !!
I think I would much prefer to stay in control and FLY the plane down.
Far easier, and more controlled, to fly correctly trimmed, at 120 knots, -500 ft/min on a steady heading, making small adjustments, and staying in control.
Probably far easier for ATC as well, that someone spiraling out of control !!
IMHO – but I am NOT a CFI – just my personal choice should I ever get into such conditions in RL
Steps back, for the wave of attacks from the rear seats !!!