Thread: 2006 CTSW For Sale - Must Sell

With the departure of the snow, this CTSW is up for sale.

Flight Design CTSW 2006, 425 hours. Always hangared; meticulously maintained by Flight Design USA. Must Sell ! $73,900. UMA engine gauges, Neuform 3-blade prop, photo window, leather seats. Factory-approved avionics: XCOM 760 Radio, Two Bose “X” headsets, Microair T200SFL Mode C Transponder, CAI 302/303 GPS, ELT. Wired for Garmin 696. Includes spare radio, blank left & center instrument panels, spares & tools. Delivery Options.



Contact: dellis@gmavt.net (802) 279 2536

That's a first! I've never seem a Cambridge vario installed in a CT! Do you use the CT for soaring?

Non-soaring folks: The Cambridge 302 is just about the most popular soaring variometer (center panel, upper left).

Doug

Doug
Dave Ellis, the author of the ad, is one of the main developers of the CAI Variometer/GPS. It was installed in the CT primarily for the GPS capabilities although some people did some ridge soaring with it.

All right, soaring guys, enlighten those of us who have never experienced deliberate silent flight as to what a Cambridge Variometer does and why it it such a cool thing. And would we want it on our CT's?

N60VT uses the CAI 302 and 303 for several reasons.

1. The rate-of-climb indicator (vario in gliding terminology) has a response time suitable for a lively aircraft like the CT.

2. The LCD shows Average rate-of-climb that I find interesting.

3. The system does very simple GPS navigation using a custom Navigation Point Database.

4. The system records flights for viewing with specialized PC software or on Google Earth.

5. Airspeed, together with GPS Track and Groundspeed is used to compute and display accurate wind strength and direction.
I find this useful in selecting alitudes for cross-country flights. (high for tailwinds, etc.)

6. The audio variometer is coupled to the radio. The CT simulates glider performance at ~3000 RPM. It climbs nicely in thermals.
But it certainly doesn't "feel" like a modern glider.

7. Most important -- I designed the thing and enjoy playing with it!

Regards,

Dave Ellis

Originally Posted by tlarry17

7. Most important -- I designed the thing and enjoy playing with it!

Seriously? It's quite an instrument, thanks for all your hard work!

Doug

Thanks, Doug!

The 302 also taught me to land the CT at 15 degree flaps. It has accelerometers aligned with the roll and pitch axes. I can record aircraft pitch vs. airspeed for different flap settings. I took data at altitude in smooth air. At 30 and 40 degree flap settings, the nose wheel is marginally above the main gear at stall speed. This makes it hard to keep the nose wheel off the ground at touch-down.

On another topic, I noted odd oil pressure indications after about 100 flight-hours. After receiving a replacement sender, I did calibration runs on the original and replacement senders and the indicator. It turns out that engine vibration wears the sender's resistance element. This causes hysteresis that leads to odd indications. This is probably the reason why Rotax recently changed the sender to a solid state pressure transducer.

If you're interested, send me an email at dellis@gmavt, and I will send a package of information on these two topics.

Regards,

Dave Ellis

Originally Posted by tlarry17

...

The 302 also taught me to land the CT at 15 degree flaps. It has accelerometers aligned with the roll and pitch axes. I can record aircraft pitch vs. airspeed for different flap settings. I took data at altitude in smooth air. At 30 and 40 degree flap settings, the nose wheel is marginally above the main gear at stall speed. This makes it hard to keep the nose wheel off the ground at touch-down...

Dave Ellis

hi dave,

i'm not sure that makes sense, at least to me. i can do a full stall 30 degree landing with a very high pitch attitude even with my throttle closed. i do have to bleed off enough energy/speed to be able to pitch up/flare without climbing.

i could stall at altitude in smooth air with 30 degrees pitched up so high that i will whip stall or i could stall it in a landing attitude or a flat attiude or even a nose low attitude.

it is harder to contact the nose wheel with 15 or less but it is harder to stop short and clear obstacles because of the faster flatter approach. i have 1,000 30 degree landings, usually with the throttle closed.

lastly it becomes easier to contact your tail with less flaps but is almost impossible with 30 or 40.

I took accelerometer readings in still air at a takeoff weight of ~ 1000 lbs and temperature of ~ 65 degrees F. Data was taken at different, constant airspeeds. Accelerometer readings were converted to pitch angles. The numbers are the angle between a triangular plane made by the nose wheel and the main gear, and a horizontal runway. Positive angles mean the main gear is below the nose wheel.


ASI 0 deg. 15 deg. 30 deg. 40 deg.
Knots flap flap flap flap

55 2.3 -2.3 -5.7 -6.9
45 5.7 4.0 0.0 -1.7
40 10.4 5.7 1.7 1.1
35 12.1 8.6 3.4 2.3

Sorry about the "scrunched" tablular data!

At 30 or 40 degree flaps, there is less than +2 degree angle between landing gear and runway at 40 knots. The CTSW wheelbase is only 57cm, so if you touch down at 40 knots constant airspeed, the nose wheel is less than 2cm (0.8”) above the ground. That is a 3-point landing!

Of course, we don’t land at constant airspeed. After the initial flare, we try to hold constant altitude just above the ground. We maintain lift by increasing pitch as airspeed decreases, and the main gear settles gracefully onto the ground. The nose gear makes gentle contact as the aircraft succumbs to decreasing lift/gravity. Flare and touchdown are the most critical flight regime. If we flare at 50 knots, we have to hold both altitude and attitude for 5-10 seconds. Because we are so close to the ground, wind gusts require quick, accurate control inputs to avoid hard touchdowns. If I inadvertently touch down at 40 knots, 15 degrees flaps gives me an angular margin of safety of 5 degrees over 30 degrees flap. I like that.

At idle, (~2000 RPM at 50 knots), the CT sinks at 500-600 feet/minute. The rate is surprisingly independent of flap settings between -6 and 30 degrees. We should not, therefore, think of CT flaps as a way of increasing sink rate. A full-rudder slip works better. More positive flap settings decrease stall speed. This means short-final airspeed can be reduced. This, in turn, means steeper short-final glide angle. But this is not necessarily good.

Those of us who fly gliders become very aware of aileron “feel” over a wide range of airspeeds. As airspeed goes down, the ailerons become markedly less effective, and maximum roll rate goes down. At touchdown we commonly use full aileron deflection just to keep the wings level. The problem is more severe with flapped gliders as the inner, flapped wing panel is still flying while the outer wing panel is fully stalled with ineffective ailerons. This is one reason why some modern gliders use full-span flaps (flaperons).

The CT is not immune to this effect. With lower stall speed at high positive flap angles, roll-axis attitude becomes harder to control. At altitude, try simulating a landing with un-accelerated stalls at different flap settings. At 40 degrees flap and ASI < 35 knots, the CT is still flying, but it is hard to keep the wings level. With 15 degrees flap and ASI ~ 40 knots, roll-axis attitude is much more controllable.

The CT can land safely at any flap setting, including -6 degrees. Optimum flap setting for landing depends on conditions and pilot skill. I’ve found that landings at15 degrees flap are easier than landings at 30 or 40 degrees flap for two reasons:

1. There is less chance of a very unpleasant nose-wheel-first landing.
2. Aileron control at touchdown is better.

Note also that, while the CTSW POH doesn’t provide strong guidance on landing flap setting, the Flight Design USA website recommends 0-15 degrees flap for a typical touch ‘n go pattern.

Finally, scratching the CT tail skid occurrs at +12 degrees flap angle. I’ve found that at 0 degrees flap, touchdown happens at 40-45 knots. At 15 degrees, touchdown is at 35-40 knots. If pre-touchdown is done at constant altitude, the data above shows that the CT tailskid is unlikely to be scratched. I’ve done some VERY nose-up landings and have never scratched the CT tail skid.

Regards,

Dave Ellis
dellis@gmavt.net

I think some of the loss of aileron effectiveness can be attributed to the control rod linkage with flaps at 30-40°. As the ailerons droop with the flaps, the pivot point changes in the linkage resulting in less motion of the aileron for the same motion of the stick. Of course, I am probably stating the obvious since this can be seen on the ground with the flaps up and down and was shown to me during my CT checkout.