Thorp Air Command - T18.net

I finished N883FF's condition inspection yesterday, and the evening brought perfect weather, so it I did a series of faster and faster high speed taxi's until I could lift and lower the tail without directional problems.
Then when I was doing that again it just sort of floated off into the air at part throttle. So I left it like that and soon I was over 100 climbing out.
883FF flew with a heavy left wing, no suprize, as I weigh about 220#. I adjusted the flap differential control, which slightly lowered the left flap. That did the job.
I went to the practice area and observed over 140 MPH while still climbing, so I slowed down and got to work.
I did an arrival stall, which started with a nibble above 70, and on the second try, a sharp break with the left wing dropping about 45 degrees and the nose down about 70. The recovery was 'stick relaxed forward' roll it and pull it up while adding power. I hope the deployment of the flap for trim was a contributing factor, I'll try stalls with that flap retracted.
I did some turns and rudder work, chasing the skid ball around, also using the electric elevator trim, which is very user friendly.
Then I made an approach to the home drome, figuring to fly by. But the speed control, application of 1 notch of flaps and the height / angle were just right, so I touched down in the first 1/4, rolled out with some bouncing but good directional control, and headed for Bruce Finney's ship for a couple of pics.
Needless to say, I was beside myself with excitement and adrenaline.
My wife was at a 99's fly out dinner, but when she got back, she knew I'd been up to something as soon as she saw me.
I now see that an O-290 ship is not underpowered. I was looking at old NLs, Ed Ulrich opined that 883FF's 68x68 Ted Hendricks prop is about perfect. My first impression is that he was right.
The O-290 gave one little hiccup at reduced power. I didn't like that at all. However, the logs indicate some attempts to change the air filter media to correct it, and other sources have stated that O-290s with MA4 carbs from O-320s can do that.
Cyl Heat temp reached 300F on the ground, and about 280-290 in the air. No leaning was attempted in flight.

Outstanding! Now give that bird a good shake down and hopefully we'll see you on the "Thorp Fly-In Circuit"!

_________________
Lee Walton
Houston, TX
N51863,N118LW
KEFD

Right on Chief!!......no longer a COB......now a COP....Chief Of the Plane

Here's a pic:

Hey Chief, be ready in Sept to bring that new bird to the KVIS gathering in Sept, got 2 birds sporting the 290 and both of em are fine machines. What really shines on that 290 is the good cruise, and the low fuel burn, it is a good power plant. Details for KVIS will be posted shortly, Hope everyone likes Mexican food. And I guess for the Friday arrivals we will have steak again at Tahoe Joes Steak House if everyone would like..........Dan

N883FF got a second flight yesterday. I took the wife along, hoping that she will be able to pick up the T-18 as her preferred flier.
I have a little trouble with the skid ball. I must be a bit heavy on the feet. During the take off, we bounded into the air with some sideways jounces....and a little slow. We picked up a little carb ice waiting for the training flight to clear the runway.
Some smooth flight, a speed test...(152 MPH @ 2550 RPM, 2700 ft, 1450 lbs, no wheel pants), and a flaps up power off stall.
Then Marilyn put her hand to the control. She did well, and had a good time. Much better skid control than me. She is a CFII, and had an aerobatic + tailwheel lesson last week. The stall got her attention, but didn't deter her.
Some more air work, a full pattern into the Home Drome, and a 2 notch flap landing. 95 MPH on final, flair over the numbers @ 80 ish, and a hobby horse landing!!! I must have landed the tail wheel first. I gotta be flying faster then put the main wheels down? (Wheel landing?)
Even with that 3 in 1 landing, the directional control was very good. This plane tracks well. And does not use very much runway. Once on the ground, it whoahs up real nice.
I was pretty shaken after the first flight, but this second flight was much easier on me. I like it and I'm sure we'll be mastering and loving N883FF.
Now to start increasing that speed...

Chief - 95 seems a little fast on final - As I learned to fly my first Thorp, I too flew it a little fast on final thinking it gave me a little margin of safety - I was wrong - it only made landings more exciting. With the thought that every (homebuilt) aircraft is slightly different and the good thing you are doing is learning the stall characteristics on the upfront, perhaps try the 1.3 times stall speed on final - 80 over the numbers is good tho - having said that, I'm usually 80 MPH on final and down to 70 over the numbers, then fly the sight picture and ignore the speed until touch down - a little forward nudge on the stick when the wheels touch will glue the mains. If a minor bounce, then just gently flaring to a three point works for me.
A reasonable bounce and I apply a sniglet of power to save it - werks fer mee.
I find the T-18 to be very "ball" sensitive - just resting your feet on a rudder pedal will give a full ball of skid - even very minor inputs during a turn will send the ball hard over.
Keep enjoying and stay safe.

Finally something I can agree on with Fraser. 95 is fast. 80 more better. That faster speed is just more energy you have to bleed of to get the A/C on the ground. Not to mention trying to stop on a "short" runway.

RB

Agreed, 3 ways here, 80 over the numbers with the speed fallin off, I use 1 notch flaps for this. I havent used both notches of flaps in a good long time. I notch of flaps and the mains touch at 62 mph thats indicated...Dan

Thanks for the helpful tips.
The observed clean stall was about 70 or 72 indicated. 1.3 times this made a good starting point for approach to land. 1.3 times 72 is 93.6.
The stall is very abrupt with left wing drop. Don't want to do that near the ground. So that is a starting point that works. 1 notch of flaps on the first landing seemed better than the 2 notch landing.
T-18 gear is stiff and springy. Getting to know that one too.
I'm also building an RV-8, so the structure and controls are not a problem for me. I notice the right aileron was built with a slight upward reflex at the trailing edge, which might be the cause of N883FF's low left wing. I would like to figure this out and get a better stall.
Of course, flap down stalls are next, and maybe I should have done them already.
As always, I can't say enough good things about the stick mounted electric trim.
Also, the visibility is beyond compare.
Making a long slashing turn and a high approach at a nearby field, With a zoom climb!

Scott,
You might want to do a pitot/static system check/calibration, I found that I had a leak in the pitot line, since fixed, that was affecting my airspeed. I have a water manometer board set up that you can use.

Those are two nice looking Thorps in your photo

_________________
Bruce Finney
N18JF T-18C #262
Yelm, WA USA

You can do a pitot system leak check with a balloon. Blow it up and attach it to the pitot tube. Note the airpseed and the drop over time. There is a limit, but off hand I can't remember the limit...so many mph drop over a period of time. As far as the static system goes you can use modeling clay, a suction cup, some surgery tubing and a large syringe. Attach the suction cup to the static port and sercure it with modeling clay. The clay helps hold the sction cup in place and provides for an air tight seal. Hook up the tubing to the suction cup and the syringe and pull for vacuum. Again there are limits as to how fast it can bleed down to be with limits. I found 2 leaks in my static system. Both at the rear of the instruments. Applied some fuel lube, rechecked and Bada Bing, Bada Boom ! It held within limits ! I did this before having the official Pitot/static/encoder check. He checked the pitot static system and it was tight. Just Goggle the system check and it will talk you thru the process.

RB

Today was service day (it rained)
I removed the eye poker NAV antenna.
I repaired the wheel pants, where they were crushed by the chocks when the tires went flat during the 9 year nap. I'll put them back on tomorrow.
I kept looking for the cause of the heavy left wing.
I took a level to the outer wing panels, between the spars, both were perfectly the same.
I checked the ailerons, the right one is a bit squeezed on the trailing edge, not reflexed up as I had thought before.
The nose radius of the wings was the biggie!!
The right wing has the landing light, a big 2 light unit in the outer most station. The plexiglass lens has a very generous radius, which was the first thing I noticed. Then I went to the left wing, and noticed how thin and pointy the leading edge radius is. Mostly in the outer bay, but thinner along the entire leading edge of the outer panel.
So that explains the stall character and the 267 TT hours since 1985.
The Fix??
Any suggestions?

If you can detect that much difference just by looking and not measuring, then there probably is a problem. To be sure get one of those radius gauges they use to duplicate moulding. The kind with all the little fingers on it and when you press it against an object it follows the shape. Then you can see how far it is off compared to the radius on the drawings. I used one to compare my LE radius.

My guess is it may require a re skining of that panel to get the correct LE radius. Sounds like the leading edge radius was OVER bent ?

RB

Here is a "bent Wire" profile gauge: