3 Point Attitude…
Posted: Sun Apr 08, 2018 10:44 am
by Ad Eves
I’m a new owner, so be gentle with me…
It seems to me that the taildragger Sonex has a particularly shallow angle of incidence sat on it’s undercarriage. I think this might not make the best of an aeroplane with commendable low speed handling and a very wide speed range when operating from the shorted grass runways we typicallaly have over here. I find that in a fully-flared landing I will always have the tailwheel touching down first, and sometimes would like to be able to unstick at a lower speed on shorter runways. I have both the larger wheels and larger tailwheel which I imagine sort of cancel each other out in terms of incidence. Has anyone ever given any thought to longer undercarriage legs or another means of getting the 3 point attitude steeper or am I missing some sort of major point/disadvantage/lethal gotcha…
I guess the other relevant point is that we’re not allowed to have the last stage of flap over here as our LAA decided that it results in too great a pitch change…
Ad
Re: 3 Point Attitude…
Posted: Sun Apr 08, 2018 3:24 pm
by peter anson
Hi Ad, welcome to Sonex flying and the forum. You probably know all the sayings about aircraft being a bunch of compromises. A few things against the longer gear legs: worse visibility on the ground, easier to bend on a bad landing, expense - have you checked the price of 1.125" titanium bar? I have the small main wheels, 6" tail wheel and normally use second stage flap (have 3 stages). Tail wheel does often touch first but the mains are so close that it doesn’t matter. The runways at my home airfield are 600 metres grass and 700 metres sealed but that is plenty for the Sonex. Are you allowed an intermediate stage flap?
Peter
Re: 3 Point Attitude…
Posted: Sun Apr 08, 2018 4:16 pm
by Ad Eves
Thanks Peter
We have first and second stage flap (10 and 20 degrees??). Yes I completely understand about the compromise of aircraft design, but I was just wondering if another few inches on the mains would unlock better performance. I’m on 700m of tarmac but my ultralight is nearby on 500m of grass and I plan to get in and out of there too if I can.
I’m used to poor taxying visibility in biplanes but the Sonex does feel rather nose-high in flight when you get the approach speed back towards 1.3 Vso! I guess it’s just different..
Over in the UK the LAA decided they didn’t like the (lack of) pitch stability and nose down trim change with flap. The solution to allow approval of the type was to connect the pitch trim tab to the flaps to automatically counter flap down trim, and then to require a spring-bias manual trimmer giving a pitch-down force. I’d like to be able to experiment with the final stage of flap and may look at re-visiting the while arrangement with the LAA at some point. At the moment the aerobatic approval is the priority.
Ad
Re: 3 Point Attitude…
Posted: Sun Apr 08, 2018 9:12 pm
by peter anson
I don’t think you’ll have any problem getting into a 500 metre strip.The 600m grass strip at Kyneton has a noticeable hump (you can’t see an aircraft at the far end of the strip) and is downhill. I have probably used 500m a couple of times landing downhill but usually pull up in less than 350m. I can’t claim any super piloting skills and don’t try to do short landings.
Peter
Re: 3 Point Attitude…
Posted: Sun Apr 08, 2018 10:24 pm
by radfordc
I have landed on a paved runway and made the first turnoff in 150 meters… Do you really need better than that? I found it to be a non problem to land tailwheel first.
Re: 3 Point Attitude…
Posted: Sun Apr 08, 2018 11:47 pm
by mike.smith
Ad Eves wrote:I guess the other relevant point is that we’re not allowed to have the last stage of flap over here as our LAA decided that it results in too great a pitch change…
Such unfortunate silliness. Hundreds of Sonexes flying with 3 notches of flaps, including me. Absolutely nothing about a Sonex that does not work well with full flaps. I can come in with full flaps and land 3 point, wheel-landing, and/or slip the hell out of it, lightly loaded or at gross. About the only time I don’t land with 3 notches (full) flaps, is when it’s gusty and/or in a stiff cross wind.
On paved runways I favor a wheel landing at about 55 kts over the numbers. I don’t let the tail down until I get under 36 kts. On grass strips I still come in like I’m going to wheel land, but just flare out as the speed drops off. Sometimes the tail wheel touches first, but not often. The Sonex lands fine if the tail wheel touches first.
On paved runways I take off from a 3 point stance. I used to raise the tail, but find it takes off better leaving the tail wheel on the ground (in a strong crosswind I prefer to bring the tail up, as there is better directional control with the rudder than with the small tail wheel skidding sideways on the pavement). On grass strips I raise the tail only enough to get it out of the grass, so still keep a slightly nose up attitude and let if fly off that way.
The long nose of the Sonex is like landing a WWII fighter. I wouldn’t want to raise that nose any higher with longer gear.
Re: 3 Point Attitude…
Posted: Mon Apr 09, 2018 6:05 am
by Ad Eves
Thanks for the interesting replies.
Mike - at 55 kts over the numbers I would definitely be a tail first touchdown I think and that’s my point.. I think the attitude would already be too nose-high for a wheeler landing. Starting to wonder if my undercarriage legs are too short!
On the hard runway I’m down and stopped in 350-400m with heavy braking. I’ll try some 55 kt over the numbers approaches this week if it ever stops raining.
Ad
Re: 3 Point Attitude…
Posted: Mon Apr 09, 2018 11:22 am
by kevinh
Ad Eves wrote:Mike - at 55 kts over the numbers I would definitely be a tail first touchdown I think and that’s my point.. I think the attitude would already be too nose-high for a wheeler landing. Starting to wonder if my undercarriage legs are too short!
Not saying this happened here, but just in case:
I noticed as I was mounting my legs that the plans distance is shown as perpendicular to the bottom of the fuse (not the length of the leg itself). I was like - wow, if I hadn’t noticed that, I might have measured along the leg and cut them too short (by about an inch?).
Later as I was fitting my leg fairings I found other than slightly tweaking the shape they basically fit just right out of the box. But I had seen forum posts from folks who said about an inch had to be trimmed off of the leg fairings. Putting 2+2 together possibly it is a common oops to make the the legs too short because of how the dimension is specified in the plans.
Re: 3 Point Attitude…
Posted: Mon Apr 09, 2018 1:24 pm
by gammaxy
I think you need to consider just how much longer the legs would need to be to make a noticeable difference. I don’t have my plans right now, but I believe a 2 degree change in incidence would require the legs to be about 5 inches longer. I would think that this is about the change required to maybe notice a difference in takeoff speed at the expense of affecting the springiness of the gear legs, moving them an inch closer to the CG and making tip-over more likely, etc.
kevinh wrote:Later as I was fitting my leg fairings I found other than slightly tweaking the shape they basically fit just right out of the box. But I had seen forum posts from folks who said about an inch had to be trimmed off of the leg fairings. Putting 2+2 together possibly it is a common oops to make the the legs too short because of how the dimension is specified in the plans.
In my case, the fairings didn’t come with the kit and the dimensions shown in the plans were too long. I installed the legs flush with the top of the sockets on the mount and bottomed out in the axle sockets and measured the same distance shown in the plans with no adjustment.
Re: 3 Point Attitude…
Posted: Mon Apr 09, 2018 7:50 pm
by mike.smith
Ad Eves wrote:Mike - at 55 kts over the numbers I would definitely be a tail first touchdown I think and that’s my point.. I think the attitude would already be too nose-high for a wheeler landing.
Everyone’s low speed air calibration might be a bit different, but at 55 kts I can glide in in a level attitude. I can either kill the power over the numbers or wait a bit until I touch down on the mains. But at 55 kts I don’t sink out, at least with just me in the plane. In a full nose up attitude with the power to idle I stall at 26 kts indicated. During take-off 36 kts is where the plane will take off, and during a landing, anything under 36 kts will not get the plane airborne again. So during landings I’m shooting for that sweet spot between 55 and 45. Honestly I don’t know the exact numbers because by that time I’ve got all my attention outside.
Re: 3 Point Attitude…
Posted: Mon Apr 09, 2018 8:25 pm
by daleandee
mike.smith wrote:So during landings I’m shooting for that sweet spot between 55 and 45. Honestly I don’t know the exact numbers because by that time I’ve got all my attention outside.
They say that a good pilot won’t know his exact landing speed because he’s always looking outside. 8~) At least I do in my tail dragger.
My previous VW powered nose roller version was extremely easy to land and most likely the easiest airplane I’ve ever landed.
As for landing speed … here’s is an old video from when I was doing the initial flight testing. Landed three point and when the the wheels chirped I was indicating 36 mph (31 knots):
https://www.youtube.com/watch?v=WjA7JDJVKeQ
I do wish they were all that smooth. As far as the flaps … I nearly always use full (30º) flaps for landing. Sometimes I come in too fast and too shallow and I’ll get a bounce. Like this:
https://www.youtube.com/watch?v=MePCcM-pVHA
But then there are days when you just have to work it a bit:
https://youtu.be/0afcagd70UE?t=593
I’m still a newbie tail wheel kinda guy …
Dale Williams
N319WF @ 6J2
Myunn - “daughter of Cleanex”
120 HP - 3.0 Corvair
Tail Wheel - Center Stick
Signature Finish 2200 Paint Job
172.6 hours / Status - Flying
Member # 109 - Florida Sonex Association
Latest video: https://www.youtube.com/watch?v=1VP7UYEqQ-g
Re: 3 Point Attitude…
Posted: Tue Apr 10, 2018 12:06 pm
by LarryEWaiex121
My standard landing in my Waiex is 2nd notch of flaps if the runway is long and breaking isn’t much needed. Full flaps if short field required, or desired.
My reason for using only two notches of flaps is its much easier to get a 3 pt. squeaker with just less than full flaps. The transition time from flying in ground effect to landing is much expedited in the full flap mode. Lots of drag with full flaps.
You definitely “roll on” with a few more mph in the mid/2nd notch condtion but it feels more natural if your aiming for a 3pt. landing so smooth your passenger doesn’t know your rolling yet. I’ve had it happen a couple times. One time the lady asked if we were still flying? LOL “Nope, We’re on the ground”. Smile.
Sometimes, I do an exaggerated 3pt. and deliberately put it gently on the tail and wheelie for awhile until it pays off and plops down on the mains. That’s sort of different and fun. More like the old J-3 days when you waited till just the right moment and sucked the stick into your lap and “plop”, we’re on. Guaranteed, no more flying.
In many ways, the Sonex reminds me of my time flying Citabria’s. They too have a visual picture that you meet (normally about the tip of the cowl on the far end of the runway) and hold just that much elevator and no more. Simply bring in the elevator at a rate that holds that sight angle and no more. If you get aggressive it will only lead to tail-wheel first arrivals, or driving the tail-wheel into the ground.
Last night I made it out after work for a short flight, visiting 3 different airports. Each approach was made differently, to practice both power on, power off approaches. I never cease to be amazed at how far a Sonex will glide if you keep it clean and manage your speed. I waited until I knew I had the field made and progressively brought in flap to control the final approach. Set her down about a 100 feet past the numbers at idle.
These things always seem easier when they are done for practice. The trick is to be able to perform the same way when the simulation turns to, “for real”.
Larry
Waiex121YX, CAmit 3300, Dynon Skyview
Re: 3 Point Attitude…
Posted: Thu Apr 12, 2018 6:20 pm
by Ad Eves
Thanks all
I’ve been looking at photos and there does seem to be a variation in maingear leg length, or at least in the height of the maingear and hence ground incidence. who’s for measuring their ground incidence angles?
Ad
Re: 3 Point Attitude…
Posted: Thu Apr 12, 2018 9:59 pm
by wlarson861
If built to plans the main gear length should be the same. any change in incidence may be due to tail wheel diameter or the tail wheel mount. Sonex came out with an updated tail wheel that raises the tail about an inch. They also have a larger diameter tail wheel that would raise the tail even further. I find that I always raise the tail for take off but just find the three point attitude for landing and let the plane settle onto the runway.
Re: 3 Point Attitude…
Posted: Fri Apr 13, 2018 9:08 am
by Sonerai13
wlarson861 wrote:…but just find the three point attitude for landing and let the plane settle onto the runway.
And that right there is the key. A Sonex/Waiex/Xenos/Onex is not one of those planes where you just suck the stick back and it automatically finds the three-point attitude for landing. Some planes do that, but not these planes. You need to KNOW what the three-point attitude looks like, and FLY the airplane onto the runway in the three-point attitude in order to get a smooth landing. Sure, you can suck the stick back and wait to see what happens. But what happens is that the tailwheel is about 3 feet lower than the main wheels when it touches down. It then becomes the pivot point for the airplane and the mains come down pretty darned abruptly. Jars your teeth I tell you! Not the way to be nice to your airframe and look good for the onlookers. Know what your three-point attitude looks like and fly the plane so that you see that attitude as you touch down. It’s really not that hard!
Re: 3 Point Attitude…
Posted: Fri Apr 13, 2018 11:03 am
by Ad Eves
Thanks Joe but I didn’t say it was hard! I’m quite happy landing the aircraft in the correct attitude. All I’m saying is that I feel like my aircraft could have considerably more comfortable exploitation of it’s shorter field potential if it had a greater ground incidence.
Ad
Re: 3 Point Attitude…
Posted: Fri Apr 13, 2018 3:25 pm
by Rick524
Hi Ad, I have a tail dragger with 500-5 tires (tyres) and the newer tail wheel which is 5 1/2"
diameter. The tip of the spinner to the ground measures 46 3/4".
The gear legs are standard length as received from Sonex.
Hope this helps.
Rick
Sonex 524
Re: 3 Point Attitude…
Posted: Mon Apr 16, 2018 6:17 pm
by Ad Eves
Thanks Rick, that’s great and you’ve got the same setup as me. I’ll measure when I next go to the airfield.
Ad
Re: 3 Point Attitude…
Posted: Tue Apr 17, 2018 8:50 am
by Sonerai13
Ad Eves wrote:Thanks Joe but I didn’t say it was hard!
I know you didn’t. I was just making a general comment. Didn’t mean to direct it specifically at you. Should have added a smiley face. 
Ad Eves wrote:All I’m saying is that I feel like my aircraft could have considerably more comfortable exploitation of it’s shorter field potential if it had a greater ground incidence.
In general terms, you’re probably right. But as we all know, all things in aviation are a compromise. There is no airplane that can do all things well. If you maximize one performance parameter, you will give up something someplace else. The Sonex line do a lot of things pretty well, especially considering the “bang for the buck”.
If you (that’s a general “you”, not directed specifically at any one individual) really need an airplane that lands shorter, you probably should be looking at a different design. It’s fun to sit around sometimes and talk about “what if”, but most of the “what ifs” have already been considered by the designers of the airplanes when they made the design decisions. Still, homebuilt airplanes are all about “experimentation”, so for those who want to experiment, there are always “what ifs”!
Re: 3 Point Attitude…
Posted: Sun Apr 29, 2018 11:39 am
by Ad Eves
Well I’ve just managed to measure the height of my spinner tip and it’s only 43.5” off the ground which is a good deal lower than Rick524’s…
I measured the visible portion of my undercarriage legs (from lower fuselage edge down to the start of the hub’s steel socket) and it’s 18” - does anyone have a comparison measurement?
Some experimentation this week shows that if I come over the numbers at 65 mph I’m guaranteed a tail first touchdown.
Ad
Re: 3 Point Attitude…
Posted: Mon Apr 30, 2018 9:39 am
by builderflyer
Ad,
I measure exactly 45" from ground to spinner tip. I can’t measure the length of gear leg without removing stuff but it appears they could be longer than 18". When I built my airplane I cut the length of the titanium gear rods exactly per plan. I’m currently using a very worn 4" tailwheel but I’m also using a modified tailwheel fork which raises the tail end about 1".
Art,Sonex taildragger #95,Jabiru 3300 #261
Re: 3 Point Attitude…
Posted: Mon Apr 30, 2018 11:49 am
by gammaxy
I measured 45.5" from ground to spinner tip. Only trust this number to within about an inch since I doubt the ground is that level near my spinner. Measuring along the top of the gear leg to the axle socket is 18". It seems like the difference between the highest and lowest spinner mentioned so far is a little under 1 degree.
Here’s why I don’t think you’re going to be able to find any noticeable increase in performance without huge changes in gear length:
A 2% increase in airspeed (about 1mph at takeoff speed) creates 4% more lift. If you want to create this lift without increasing speed, you need to increase the lift coefficient by 4% from around 2.0 (approximation based on clean stall speed and gross weight) to 2.08. A perfect wing has a lift curve slope of about .11/degree. On the Sonex, it is closer to .08/degree. You need about 1 degree extra angle to make a 1mph difference in takeoff/landing speed.
It’s a shame the LAA is limiting your flaps. I think there’s more performance to be gained there. I usually don’t use flaps on takeoff, but with my Aerovee, 10 degrees makes a noticeable difference. Depending on whether you are trying to clear obstacles, or just get out of a short runway, I wonder if 20 degrees is reasonable with the 3300?
Re: 3 Point Attitude…
Posted: Mon Apr 30, 2018 3:56 pm
by avee8r
My spinner is 44 3/16, measured on a good level floor. I can’t get to the gear leg, sorry.
I have the short flaps and my Sonex stalls right at the book value of 42 with full flaps. (I understand you’re flap limited by gov. Regulation) My speed over the fence is 53 (1.3 X Vso) and I get the sweetest tail wheel first, by just a moment, touchdown most every time.
Happy Landings
John
N50NX
Re: 3 Point Attitude…
Posted: Mon Apr 30, 2018 8:13 pm
by fastj22
I tested a really slow 3 point landing last weekend (Gary Motley style). I have a lift reserve indicator and was flying just at the stall on approach, around 40 MPH, full flaps. Gary is the master of this. Sink was significant and I was adding power to make the threshold. The plane felt very spongy and just before touch down, the buffet of the stall. I bounced. Landed three point and the roll out was short. Carrier landing. But it wasn’t the type of landing I would like people to see. Seemed forced. I’ve seen Gary do this perfectly, but I don’t have his skills.
My perfect landings is an approach around 65 mph. Then attempt to wheel land but it ends up a three point (its just too slow to keep the tail up). If I want to do a nice wheel landing, I have to come in a lot faster, around 75 to 80. At that speed, you can keep the nose down and fly the tail until the speed bleeds off.
3 Point Attitude…
Posted: Mon Apr 30, 2018 9:44 pm
by caveman370
fastj22 wrote:I tested a really slow 3 point landing last weekend (Gary Motley style). I have a lift reserve indicator and was flying just at the stall on approach, around 40 MPH, full flaps. Gary is the master of this. Sink was significant and I was adding power to make the threshold. The plane felt very spongy and just before touch down, the buffet of the stall. I bounced. Landed three point and the roll out was short. Carrier landing. But it wasn’t the type of landing I would like people to see. Seemed forced. I’ve seen Gary do this perfectly, but I don’t have his skills.
My perfect landings is an approach around 65 mph. Then attempt to wheel land but it ends up a three point (its just too slow to keep the tail up). If I want to do a nice wheel landing, I have to come in a lot faster, around 75 to 80. At that speed, you can keep the nose down and fly the tail until the speed bleeds off.
Sent from my iPhone using Tapatalk
3 Point Attitude…
Posted: Mon Apr 30, 2018 9:48 pm
by caveman370
caveman370 wrote:
fastj22 wrote:I tested a really slow 3 point landing last weekend (Gary Motley style). I have a lift reserve indicator and was flying just at the stall on approach, around 40 MPH, full flaps. Gary is the master of this. Sink was significant and I was adding power to make the threshold. The plane felt very spongy and just before touch down, the buffet of the stall. I bounced. Landed three point and the roll out was short. Carrier landing. But it wasn’t the type of landing I would like people to see. Seemed forced. I’ve seen Gary do this perfectly, but I don’t have his skills.
My perfect landings is an approach around 65 mph. Then attempt to wheel land but it ends up a three point (its just too slow to keep the tail up). If I want to do a nice wheel landing, I have to come in a lot faster, around 75 to 80. At that speed, you can keep the nose down and fly the tail until the speed bleeds off.Sent from my iPhone using Tapatalk
Oops
I have the Flyboy tail wheel as John does.
My tail sits a tad higher. I do like it because I can see over the nose at 3 point attitude.
I seem to be in the area of 65 to 70 and let it settle on. I haven’t noticed any longer ground roll either
Sent from my iPhone using Tapatalk
Re: 3 Point Attitude…
Posted: Tue May 01, 2018 7:48 am
by Ad Eves
Thanks all.
I guess I’ll do some more experimenting to figure out the best short field technique for my aircraft just accepting the tail-first landings. I will also have a discussion with our LAA to see if they will allow me to experiment with the factory full-flap setting when I do the aerobatic flight test programme.
Ad
Re: 3 Point Attitude…
Posted: Sun May 02, 2021 5:32 pm
by flyingbear
I have hundreds of hours in a Thatcher CX4 and over 1000 in a Cassutt. Both need more angle of attack on the ground for short takeoff or landing. My Cassutt would lift off at 120 mph 3 point when I got it. I added 5 inches to the gear and got that down to 100 mph.
The CX4 will hit tail first any time it is anywhere near a stall. I do not like that but it does mean the aircraft stays planted better for low time pilots.
Glen Bradley