The testing of the twin turbines is now complete, below are a couple of notes regarding my last flight test:
The weather and wind was favorable for the one remaining flight test last Friday. After assembly and one turbine test run the HP-18J was pulled out to the runway for the last remaining flight test - the self-launch exercise.
Wind speed and direction was 5 to 10 mph almost right down the runway. I strapped in and powered up the aircraft, extended the turbines and proceeded with the start sequence. Once both turbines were started and stabilized at idle (33,000 RPM) the thumbs up was conveyed to the wing runner. Full power was applied (105,000 RPM) and the takeoff roll was started.
Once the aircraft speed exceeded the wing runners pace the left wing dropped and the roller blade wheel at the end of the wing did its job. Within a short time the ailerons took effect and I was once again level and accelerating towards takeoff speed. The airspeed was climbing rapidly and the tail was next to lift followed shortly by the sailplane takeoff. I stayed in ground effect for a couple of seconds then started my climb.
By the time I crossed the end of the runway I had gained 400'. I continued the climb at 60 to 70 KTS until reaching my goal altitude of 3000' AGL. Upon reaching altitude the engines were shut down, cooled and retracted. I soared for 30 minutes, did some more spin exercises to spend my excess altitude and did one re-lite to verify the restart success for the previous weeks testing. Both turbines started successfully and were shut down after a couple of minutes. I returned to the airport for landing and was greeted by my support crew once I rolled onto the taxiway.
My Oudie flight computer provided all of the finite statistics from the flight. The runway takeoff run was between 850 to 900'. The time to climb to 3000' from a standing start was 4 minutes and 45 seconds. The climb rate from the standing start averaged 631' / minute. Total fuel burn for the takeoff, climb and one restart was 3.5 gallons. Remaining fuel in the header fuel cell was 3.5 gallons.
Anticipated flight sequence. Self-launch and climb to 3k, shut down the turbines and retract. Utilize one engine for sustained flight if needed at reduced throttle. This should provide a 25 to 30 minute duration run with the remaining 3.5 gallons of fuel.
Note: The flight test performance results came within 10% of what my preliminary calculations provided. This was quite satisfying and shows that the math can really work for predicting performance results.
Lots of fun but I am glad it is over,
Hoping for video and photos from the flight crew later this week,
Regards,
Chris
