tboyden

I have a Sig 40 with an OS .46 engine. I'm having a problem with it nosing down just before touching down. I've rechecked the balance and it seems ok. But is this a problem with balance, and if so, does it mean the plane is tail-heavy or nose-heavy? Or do I need more up ellevator trim? Or what? Thanks for any ideas!


tboyden

cowboydfk

Is that the ARF?I got the ARF with that same engine and it balanced perfect and lands perfect.When the plane is in the air high in front of you can you take your fingers of the right stick with out it losing altitude? you should be able to take your fingers away from the controls and the plane should fly straight,if it flys to the ground or goes left or right you gotta trim it out,do you have anyone around to help you out?try reposting your question on the beginners you should get some response there.

tboyden

thanks. I did try giving the elevator a bit of up trim, and it seemed a bit better. I'll also try releasing my thumbs to see if it flies level.

WALKERS210-RCU

My Feedback: (36)

One thing that an old man (great source of information) taught me that on landing start feeding in up elevator gently and never give any thing back until the wheels actually touch the ground. Makes landings look like I knew what I was doing. Proper trim and CG is key to a good flying plane.

alan0899

G'day Mate,
Sounds like it is stalling, just before touchdown, try landing a bit faster, & see if the problem goes away.

fadi

Hello
I had the Sig Fourstar as my second plane, and I remember having the same problem or shall I say pilot mistake on landing.
Since you are used to really slow down the trainer, and probably to stall it a bit just before touchdown you automatically tend to do so with your new taildragger and especially the fourstar which is a model that has a considerable ground effect.

What I suggest you do is to definately fly it a bit faster on landing, it will look fast to you if coming from a trainer experience, but you will quickly get used to the descent rate and its forward speed.
On the other hand, as with any taildragger, do not flare much, try to keep the frame parallel to the ground, of course you will have to feed in some elevator at that speed to keep it straight; probably some ailerons and rudder as well. Now is a good time to start learning and experimenting with throttle control, you can adjust your throttle to reach a low descent rate.

The model might bounce back at touch down, and you could think that this is due to your fast approach, so you slowdown on your second try and this time it stalls.

In fact for a tricycle landing gear (like your trainer) this is rather correct: it bounces due to the fast descent rate and the spring effect of your tires. But for a taildragger the bounce comes from a different effect. As your center of gravity is behind your main landing gears, while loosing altitude at one point your wheels touch the ground, and they cannot go further down, but your tail does. As a result you increase the angle of attach of your wings and you often generate enough lift to fly again and lift your model.
What you should really do is idle the engine as soon as you touch down, and at the same time feed enough down elevator to prevent the center of gravity and your tail of continuing their descent while the wheels cannot follow.

This will also stick your plane to the runway and allow you to free roll on your main landing gears before bleeding off your speed and pose the tailwheel on the ground.

Well... That's obviously not the only way to land a taildragger, but it works best for my Fourstar. You could always continue with your slow stall landing and a three point touchdown, but in gusty winds I found that I often loose lift and see the plane dropping like a rock at the height of roughly 2 feet.

One final note, the Fourstar has a bad rudder/elevator couple, so if you feed in too much rudder your nose will drop (even in full speed flights up in the air).
That could be another reason for the problem you are facing. I suspect you feed in rudder to counter act a cross wind.


In the end, it is up to the pilot to learn/experiment and adapt his flying styles and habbits. The Sig Fourstar remains a low wing trainer and as such remains very forgiving on many aspects.

I wish you good luck and lots of fun and learnings with your new model.
I am sure you will love yours as I adore mine - it is on of my dearest airplane.

Mode One

It sounds to me like it is stalling. Is the balance correct; or, is it nose heavy!

How do you guys know this airplane is a Four Star 40? All the original poster said is Sig 40.

fadi

euh.. oups, probably my mistake I assumed he is a beginner with a fourstar...
Sorry if I offended somebody, it wasn't meant that way.

Mode One

I certainly am not offended, why would I be and no one else appears offended, either. I just thought clarification of what airplane we're talking about, was needed!

tboyden

thanks for all the great ideas. It's a Fourstar 40. I just got back from the airstrip, where I put about 4-5 clicks of up-elevator in. Now it lands like a dream!

-tboyden

da Rock

It sounds like it's stalling.

They do that when they're flared before they should be flaring. Or the pilot slows the sucker until it stops, and it's not on the ground yet.

da Rock

The good news is that you have an airplane that is rather mild mannered in the stall. You're lucky.

Land with a couple of clicks more on the throttle, or with a little less up elevator (until it's time to flare).

Rudolph Hart

Hi tb this guy has summed it up beautifully for us all,you may be a bit nose heavy to is how i read your post.Vague on the cg a bit.

jetmech05

You must remember/....that elevator is speed and throttle is altitude especailly during landings.....I have the feeling your having a hard time grabbing the concept....OK I'll explain it......You're on approach and you don't do anything but add throttle the airplane will climb.....now your on approach and you add elevator only...the airplane will pitch up, slow down and stall..dropping to the runway...down elevator and you pitch down, pick up speed (you have to get faster, gravity) and impact short of where you wanted....
So while on approach after the final turn I usually (remember that every landing is different) just give enough elevator to hold the nose level. this allows the aircraft to settle at a level attitude.....and slow down.....if the airplanes sinks too much then add a click or two of power.....if you have to keep power on then do so. after you cross the threshold of the runway. cut the throttle to idle and begin the flair.
Basically, throttle, a couple of clicks on, then right back off again will flatten out your approach angle....
Good luck to ya

dignlivn

Well put jetmech.


Throttle is Altitude and Elevator is Speed control.


Bob

Never stop flying the Plane never.

Bass1

My first guess would be there is a slight amount of "upthrust" in you engine/firewall setup. Then you compensate for the airplanes tendency to climb under power (from the upthrust) by adding down trim to the elevator. Then when you chop the throttle at flair you loose the upthrust and the downtrim in the elevators takes over.. and down she goes

jester_s1

Check out one of the aerobatics trim guides available on the web. If you will get your thrustline and CG right, the plane becomes very predictable and tame in all aspects of flight, not just landing. Be gentle about adjusting your CG though. As small as 1/8 inch change is noticeable in flight on a .40 sized airplane.