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Posted for J H Webb <airmale@bright.net>:
In reference to Marshall's Questions, I offer.
For those of you who are already past the flight test phase of your
experimental turbine would you mind sharing with us the data you collected.
Here are some of the more pertinent areas of interest.
I did the first flight and extensive handling testing of a Lancair IVPT in Athens GA. Due to the lighter weight of the Turbine engine the engine and prop plane was extended father forward of the firewall than in the Cont. installation. This
did make for some handling difficulties and required some changes in the vertical surfaces. 1. Did you perform stalls or did you stop at buffet before the stall?
We did complete stalls as defined by the FAA Part 23 requirements. Prior to the addition of the ventral fin the direction handling in the stalls was poor. After the addition of the ventral fin the stall handling was acceptable. 2. If you did a complete stall give the conditions (flight and aircraft;
e.g.. 15,000 ft and forward cg, power on/off, etc).
These stalls were done from 8,000 to 12,000 cg mid range.
3. Have you experienced any stability and control problems?
Prior to the addition of the ventral fin the airplane had some serious directional control problems. At high speed was the most abrupt problem. If you reduced power quickly the airplane wanted to switch ends due to lack of sufficient directional stability. This is caused by adding surface area ahead of the center of pressure and no compensating area aft of the CP. Then a big power reduction would make the prop become a brake with high drag and like a big forward rudder. This was also noticeable in the stall series before the addition of the ventral fin.
4. Have you experienced any flutter? Obviously not of the catastrophic
type, but vibration nevertheless.
None noted through red line.
5. During all of the flight test hours and thereafter have you noticed any
cracks or delaminations on any surface?
None noted.
6. My understanding is that Lancair is not recommending adding to the
leading edge of the vertical stab even though they did it to the Sentry.
Has anyone found it necessary to add vertical surface?
We did find it very necessary see enclosed photo. I measured the body angle for ground contact and determined that there was sufficient room for a suitable ventral fin. 7. What was your determined best rate/angle of climb speed?
Yes we did and the speeds are higher than the Cont. speeds by about 20 knots.
8. Finally, do you have any suggestions for a safe test flight program or
if you had to do it over again, anything you would have done differently?
I wish we had the time and especially money to do all the tests in the FAA 283 Flight Test Guide. In the suggestion area I recommend a very careful program and be very suspicious (looking for any little indicator of problems).
Jack Webb
L 360, L IV
ATP, CFI Airplanes & Instruments, Multi, & Sea
Many Type Ratings
Experienced Experimental Test Pilot both multi and single engine
Former Chief Engineering Test Pilot for a Major Manufacturer
AeroSpace Engineer BSAE
Ohio
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