Smooth and Graceful Landings
 

I rarely contribute tips because it seems to me that no one really cares to try them. This one is a little bit different in that it will greatly improve your flying experience, specifically your landings, so much so that I feel compelled to share.

A little background first. For most of my 35+ years of flying, I have been able to land planes of all sorts very, very smoothly with no ballooning or porpoising in the final stages of the approach and touchdown. You know what I am talking about. Even the slightest elevator input now seems to be just a little too much when you are really trying to keep everything really, really smooth; even when using exponential rates. For the last several years though I have had difficulty keeping those landing approaches/touchdowns completely smooth. Think about what the trend has been with servos over the last few years—stronger, yet lightning fast.

Last fall at a jet meet I complimented one of the pilots that I know quite well on how smooth and graceful all of his landings were. We had a conversation about how no matter how hard I try, I always seem to get a little bit of ballooning on landing (Aviation Design Scorpion). He shared with me his secret which I am now putting out for the benefit of anyone who will try it for themselves. His secret is that he uses the servo slow function on his transmitter to slow down the elevator servo even when using exponential rates. Now, this approach had never occurred to me but it made all kind of sense. Unless you are flying some wildly aerobatic plane, who needs a lightning fast elevator?

I couldn’t argue with the success I observed him having so I decided to try it for myself with just a small amount of servo slow added. OMG what a different airplane it was to land. Unbelievable the difference it made! Next flight I slowed the elevator down a little bit more and was quite pleased with the result. Now I am getting compliments on the smoothness of my landings. I now use this technique on every airplane I own with similar great results!

I expect there will be plenty of unbelievers who scoff at the idea of slowing the elevator servo down and will never even try this but, I am telling you, you need to at least try it. If you don’t like it, just change it back!

Could you tell how to slow the servo down . Never heard of that . Does it take some new special servo? I would like to give it a try.

Edit [ I see now it's a transmitter function. I don't think I have that . Guess I'm out of luck.]

I can tell how I did it on my transmitter. Different brands and even different transmitters within a brand may have a different way of doing it. I might be able to help on your specific transmitter if you tell me exactly what you have. Sadly, many of the lower end transmitters do not have this function.

This is my 10th season using my rock solid Futaba 12FG radio. In my case, I go into the "Linkage" section of the menu and I select "End Point". It is on the End Point screen all the way to the right hand side to the column labeled "Speed" where you can slow the servo down. See the attached photo below. You can see that Elevator and Aileron have a value of 6. For flap settings, the number is best anywhere from 18 to 20 which makes them quite steady and slow. You certainly don't want that much on flight surfaces. I started with a value of 3 which helped but went up to 6 which is even better. "0" is the default value where the servo is not slowed at all. I can slow down any or all 12 servo channels if needed.

Steve.... Interesting... I'll give it a try.
I'm thinking, the best landing plane I have is a very old Cub and it has some very old servos in it, so old in fact that they are one of the few servos that are restricted to not allow 6v power and thus have diode voltage drops. Running the low voltage also keeps them slower.

You now have me wondering if it is actually those old servos running so slow that has made that plane so delightful to land.

Edit Notes: There is one other issue at play with this Cub. First, I didn't build it, but rather bought it at a swap meet. The builder used a plastic servo tray having three bays, the kind that the servos drop onto pegs and then keepers lock them down. The builder did something that wasn't kosher but it inadvertently turned out well. He placed this servo tray side to side in the wing bay instead of lengthwise. The trays did not hold the servos tightly and the elevator servo sitting crosswise to the control arm, gives a great deal. After purchasing the plane, I came close to changing it but flew if first and finding no flight problems, left it.

I now think it is a benefit and one of the reason the plane lands so well.

I must admit I have never thought of this, but it makes perfect sense. Do you slow the elevator servo all the time or is the slow function on a switch just for landings?

I keep the servos slowed all the time. Even slowed down you still have quick elevator response. I suppose you could set up a flight condition where they are only slowed down for landing but I think you will find that the elevator is still plenty responsive and this would not be necessary. I used to do pylon racing for many years and I find that, even with the servos slowed down, I can still do the tight pylon turns.

Thanks bunches, my last trip to the field was devoted to shooting landings and proper take offs, Will check Out my Hitec Aurora 9 and see it it's possible? Sounds like an excellent idea.

The H9 does have the servo slow feature, I'm not sure it would allow the feature to be assigned a switch though. This certainly could be useful on most models provided all other things are in line. If the airplane has other issues that make it difficult to land, IMO it would be best to get those issues sorted out as well.

And I thought just holding the stick between my thumb and index finger was enough!

Try and Get to it soon. Thanks

Just a thought, those who are slowing the elevator servo: are you using any expo on the elevator as well as the speed reduction?

I fly with down elevator trimmed, so I am constantly putting pressure on the stick, so I don't have that problem anyway...

Can you elaborate? I don't see any connection to the question I asked or the thread topic.

I tried a .4 sec elevator servo speed reduction today for the first time on a Cub. I do use 40% expo. The landing was in fact smooth but I can't say for certain where the credit lies, what I can say, is that it didn't hurt.

I would not have expected it to hurt at all on a Cub, in fact most airplanes would not suffer from taking a bit of speed out of a servo. Back in the day most standard servos would have a speed rating of .18 to .20 and we were able to fly just fine. I get where there are cases where a faster servo is desirable but for most guys if slowing a servo down will make an improvement with the particular airplane they are flying then I say go for it.

I've a Seagull Funfly 3D with an Evolution 10cc swinging a 14x4W funfly prop that I'm anxious to try the throttle servo delay on. Controlling pitch on landings has always been more difficult than the rest of my fleet. In fact it is the only plane I run 60% expo on and still it is challenging.

Sometimes I swear that the slower it goes the more pitch sensitive it gets, but I've tried balancing further forward but gotten no relief. And... it doesn't linger down the runway like it is tail heavy. It is just pitch sensitive at slow speeds. Maybe it needs more expo at slower speeds.... who knows?

What i do know now is that I'm going to play with an elevator servo delay with it.

Actually moving the CG forward is counterproductiv. You want the airplane to be more neutrally balanced. Start out with moderate elevator throw and CG back around 35%. The object is to have the elevator trim stay constant from just above stall to full speed. That is a product of CG and elevator trim. For a 3D type airplane the wing and stab should both be set at zero. If the CG is too far forward you will need to carry up trim. The result is much like a car that always pulls to one side. Hard to drive smoothly that way.

Yep... testing a more forward position was indeed counterproductive and it was reset back to where it was. Where it is now provides proper power on/off trim .
I've come to believe that the very thick foil perhaps in combination with the short moment is something I've just not gotten used to. Thick foils continue to produce a lot of lift at slower speeds and my normal pitch control habits when landing likely produce over controlling. It might be that more than 60% expo would help. Or... maybe a land setup is needed. Or maybe.... elevator servo slow down... I'm going to try it and maybe do so on a land switch as I like kicking the bird around other than when landing.

It's possible you are just running too much throw on low rates on your 3D plane. Flying pattern has taught me the value of low rates; the more your turn the throws down the smoother your plane becomes. It's really easy to make a 3D plane twitchy with those big surfaces.

Yep... very possibly just too much throw.

I'm thinking a lot of pitch sensitivity comes with the agility of a short moment. I flew the Fun Fly yesterday because of the desire to test the elevator servo speed delay. I flew twice and the first flight was mid afternoon with a cross wind and no benefit was felt from a .4 sec speed setting.

The second flight was made early evening and deciding to up the delay to get some effect, the set screen showed the delay off.. Silly me, the mix switch was in the wrong position for the delay so it hadn't been in effect the first flight. It was left at .4 sec.

The second flight was all about touch n goes... a couple of dozen of them and landings were in fact smoother with pitch control much easier to manage. The other thing sensed was that with less concentration needed for pitch control, more could be given to throttle control, which is critical on this plane running 14x4W prop as going too low on idle is like slamming the brakes on.

After a few landings and trimming the idle to maintain a desired glide slope, landings were very smooth to touch down.

At play is the mode II coupling problem of slight pitch movement when giving aileron. A delay seems to help deal with that.

Good to see some folks actually trying this. It tamed down my pitch sensitive planes and makes my landings look like I know what I am doing. Looking forward to reports from others who have also tried this.

I talked with the guys about this at the field yesterday. Several said it made sense to them. Whether they will try it, of course remains to be seen and likely depends on whether they sense a need or value in doing so.

I found the same thing with my 1/8 scale hydroplane. I know, we're talking elevator servo speed but servo speed is just as relevant to my boat's rudder.
I have an S9156 high torque digital servo handling my rudder. I found that the boat was difficult to hold a steady arc while cornering until some one told me to slow the rudder servo down. I found my transmitter, a Futaba 4PLS has a servo speed adjustment, both faster and slower. By setting the servo speed at 50% and increasing the throw from 30 to 45 degrees, the boat now holds a smooth, constant arc without me having to play with the wheel during a turn. This is very important when you have multiple boats going through a turn together as a boat that is "twitchy" is a danger to every other boat on the water

You know all these 'experts' you see making these unbelievably smooth and straight take offs and landings.

Many of them will be using an electronic aid, gyro control of rudder and elevator.

Shhh it is a secret.

By a cheap switchable gyro and have a play. You will look so smooth.