New to FSX and FS2020.

I've crashed trying to land more times than I can count. Isolated the biggest part of my problem to the descent. I can never get to the runway or I'm way past it.

I've changed the rpms by 50 rpm or changed the trim by one 'knob' on the trim wheel. The plane always starts the phugoids. By the time the plane settles down I've destroyed my descent profile. Changing in increments to start a descent is nuts.

So, what is the secret to changing the speed or attitude (or both) of the plane without having it oscillate up and down?

Welcome to the AVSIM forums! 😄  Which Sim was being used when these approach crashes happened?  What aircraft?  Fixed pitch prop, like the C-172 or a constant speed prop like a Baron 58 or similar?

Were you following directions from ATC at the time or doing everything on your own coming into a non-controlled airport?

The trick is that there isn't a trick to it, you already know what you are doing wrong, you just have to adopt the solution. What you have to be, is 'in front of the aeroplane' in terms of controlling it, by anticipating what it is doing and what it will do, then only making timely predictive adjustments to stop any trends you don't want, such as a slight climb, or a slight descent or whatever. So, try this...

Not even whilst attempting a landing, but to suss things out first, just get the plane pretty much straight and level, up at a few thousand feet. When you have it like that, reduce the throttle a bit and then leave it like that, and wait to see what that does. What it will do, is reduce speed, and going slower, the wings will produce less lift, so the plane will start a slow descent, but now it is going 'downhill' a bit, so it will speed up a little bit, which will increase the lift a bit, slowing the rate of descent, but that will slow it down a little bit, so it will be creating a bit less lift, so it will descend a bit etc. All of this happens smoothly, until the thing settles in a steady gentle descent at a steady speed. so you can descend using the throttle.

This is the important concept to grasp here. Use the engine to control your altitude.

Next, get the plane straight and level again. This time, pull the stick back very gently, so your nose is a few degrees above the horizon, and either hold the stick in that slightly back position to keep the nose up a little bit, or if you are familiar with the elevator trim wheel, you can use that to hold the aeroplane in that slightly nose up pitch attitude. When you have the plane pointed ever so slightly nose up as it flies along, wait to see what happens. What you will find is that the aeroplane will initially climb a little bit, but it will slow down a little bit and eventually it will fly along level, but at a slower speed. Next try putting the nose down a tiny bit and holding it there, and you will see the aeroplane speeds up a bit. Again, all of this happens smoothly, until the thing settles at a steady speed. so you can control the speed using stick/yoke, and never even touch the throttle at all.

This is the important concept to grasp here. Use the control stick/yoke to control your speed. I know they never do that in movies, but that is what you do in real life. This is not what most people expect when controlling an aeroplane because of all those movies where people ram the stick forward to land a plane in a disaster movie, or fly along constantly moving the control wheel about all over the place, which is not what you do in real life, most of the the time you leave it alone. Also, many people are far more used to what you do with a car, or motorcycle, i.e. more throttle means you go faster, and the steering points you where you want to go, so it's initially a bit weird to find that in an aeroplane, it is the other way around.

You should bear in mind that you can do it the other way around with an aeroplane, i.e. climb and dive with the stick and speed up and slow down with the throttle, and most pilots  do this some of the time as well as using the other way, and various combinations of all that, but using the throttle to control the descent will help you get your landings sorted out when you are new to it, and it is the way we are all taught when first learning to fly an aeroplane.

Now, apply that technique to a landing. Use the throttle to get yourself alongside the runway up at a 1,000 feet, then throttle back and start descending whilst offset about a quarter of a mile to the side and parallel to the runway, then fly along past it until the end of the runway which you are going to turn for, appears to be over your shoulder at about a 25 degree downward angle and you are at about 600 feet above the ground. In the average light aeroplane, you want to be coming in for a landing at somewhere around the 50-60 knot speed range, and whilst flying the circuit, you maybe want to be at about 75 to 80 knots. These are 'ballpark' figures, it depends on the aeroplane and its weight, but you won't be too far off these numbers.

Make sure the landing gear (if it is retractable) and flaps are set up properly (note you will need more power with the flaps down because they create a lot of drag). Next, turn left onto the crosswind part of the circuit, continuing to descend just using the throttle to control that rate, then aim for being at the point where you need to turn for the runway at about 400 feet. You should now be in a fairly stable descent, lined up with the runway.

You can make minor pitch adjustments and or minor throttle adjustments at this point, but if it ain't broke, don't fix it, and don't use massive control movements, just make a minor adjustment, wait and see what it does, anticipate any unwanted trends and then correct these early if necessary, don't let them develop. If you do that, you end up chasing the aeroplane instead of 'being in front of it' in terms of behaviour.

When you come over the end of the runway and you know you're gonna make it, throttle back and ease the stick back to try to keep the plane flying as it descends, this should put you gently on the runway.

If there is a trick at all to flying an aeroplane at all, it is actually to 'leave the goddam controls alone' and only make minor corrections to keep it doing what you want it to do. Don't get frustrated if you are not brilliant at it immediately, it won't take you long to suss it out now you know what to do. Practice makes perfect. 

Edited December 26, 20205 yr by Chock

Thank you for your time and detailed explanation. I have a flight set up to take me into my home airport, KERV.

Initially I'm at 2000 rpm, 85 KTS, VSI:0, 5800 ft. and about 18 miles from KERV.

I reduced the rpms to 1800 and touched nothing.

Airspeed went to 80 KTS.

The VSI vacillated between these values: -400 -200 -350 -150 -300 -200 -300 -200 -250 and apparently settled on -200. I didn't time it, but the excursions took a couple of minutes.

The straight-in RNAV (GPS) RWY 12, for KERV, as I understand it, stipulates I should be at 4000' at waypoint OBUCO 12.3 NM from the airport to begin the descent.

But how can I make an accurate descent if the plane is pitching up and down? That was only a -200 rpm excursion on the rpms. If I wanted to descend at, say, 500 fpm at another airport I would have to reduce rpms further inducing greater swings on the VSI. How in the world could I do something more complicated, like stay on a glideslope?

In round numbers I've got about 10 minutes of descent time at 80KTS at KERV. I've just blown about 2 min. of that because of the plane's wild up-down gyrations. 

It's obvious I'm not understanding something.

bcdozier

Sounds like you need to trim it out. Unfortunately trimming is a bit more difficult on a computer flight sim keyboard/joystick than it is in a real aeroplane with a trim wheel, where in real life it is very intuitive and quick to do. But if you understand the concepot, then if you assign a button or key to 'elevator trim up' and 'elevator trim down', you should be able to get the aeroplane behaving itself in either level flight, a descent, or a climb. for more info on what that is actually doing, this will have you up to speed:

https://en.wikipedia.org/wiki/Trim_tab

 

On 12/26/2020 at 2:24 PM, charliearon said:

Welcome to the AVSIM forums! 😄  Which Sim was being used when these approach crashes happened?  What aircraft?  Fixed pitch prop, like the C-172 or a constant speed prop like a Baron 58 or similar?

Were you following directions from ATC at the time or doing everything on your own coming into a non-controlled airport?

FSX. Cessna Skyhawk. Fixed pitch. Attempting a straight-in landing to KERV, a non-controlled airport, from about 13 miles out at 5,000 ft.

That should be a fairly easy approach.  Cut back on engine RPM and slow down. (basically, reduce your throttle). Once below the appropriate speed, lower the flaps to the approach position.  Keep descending and slow down to around 75 knots and lower the flaps to landing position.  Set yourself up for a landing at 65 knots speed.

Be sure your pitot tube heat is on and you are adjusting the mixture according to your altitude.

I highly recommend the Sitka Landing Mission to practice this type of approach.  Just follow the instructions of the Instructor.

With all the oscillation you describe, sounds like you may have the auto pilot engaged. If so try without it and fly pattern circuits using all the information provided in this thread. Probably the most valued is pitch/trim for air speed and throttle to control descent/ascent. Keep in mind, each aircraft is different. Pattern flying is a good way to get familiar with each aircrafts attributes.

you can check YouTube, Sim CFI, he has a bunch of quality videos out there with great information and tips.

Good Luck!

I set aileron and elevator trim on buttons on the yoke.  

Then I set the rpms on my practice flight for -500 fpm descent. While adjusting the rpms I added one click of up elevator via the yoke button. 

Smooth as silk. Plane went to -500 fpm and never bobbed once. 

Now, I'm eager to try landing tomorrow. 

Thanks again for the help.

On 12/27/2020 at 1:10 AM, Chock said:

If there is a trick at all to flying an aeroplane at all, it is actually to 'leave the goddam controls alone' and only make minor corrections to keep it doing what you want it to do. Don't get frustrated if you are not brilliant at it immediately, it won't take you long to suss it out now you know what to do. Practice makes perfect. 

Alan,

Practice makes perfect. 

That brought back memories! Cessna 150 at Luton 1966. My first couple of lessons. Just could not get the landing right. Then suddenly, after about 10 attempts (over about 2 weeks of touch and go) it suddenly clicked and from then on, I never missed one. And that includes the nervy first solo after my Instructor got out and said " OK, now you try it on your own".