Grey

Grey's Flight Testing (our Development Mule)

Flight testing of N430J "Grey" is complete on our end. We learned a lot.

"Short field day" were we looked at maximum performance take off and landing was an eye opener. The dramatic reduction in weight of the GXT combined with removing drag has significantly reduced stall speeds. We have consistently replicated stall speeds in the low 70 knot range with some in the high 60 knot range (all dirty or landing configuration) with the differences being attributed to fuel load. All these factors combine to make for a plane that accelerates harder, leaves the runway sooner, lands slower and stops better.

Here is a short field take off. The pilot indicates the plane is of the ground in under 850 feet. This is runway 14 at F45 so it is a 4,300' runway. It is easy to zoom in and judge for yourself just how much of the runway the plane is using.

Here is a short field landing. Again, the pilot has used the first turn off which indicates less than 1000 feet used of 9R at F45 (a 4,300' runway).

The UltimateL39can get off the runway, taking off or landing, in under 1000' at sea level single pilot and half fuel.

Here are some links to supporting data..... Engine performance is verified each day by making sure the motor makes "N1 for the day". This value is obtained from a look up chart (ours came from a Hawker) that provides a minimum static N1 for a given temperature and altitude. The engine flown for development had less than a 100 hours remaining on the hot section. All data presented is from motors at the end of their hot section and NOT fresh motors. Here is a N1 for the day listing for some of Grey's early flights. The very first numbers are off a bit as we worked through N1/N2 calibration. A friend of the project was kind enough to provide G3X data from his L39MS, the Albrtros with the DV2 motor and an extra 1000lbs of thrust over the standard AI-25. Here is a time to climb comparison of Grey v. the MS to FL28. Both planes per paused at different altitudes by ATC so those segments have been edited out. Top speeds for the two planes at altitude were identical with Grey at maximum continuous cruise power. Here is the climb portion from the 14th flight where we are doing a cross country simulation. Here is the cruise performance plot and raw data for that flight at FL25. I integrated fuel flow to determine fuel per segment here. And then did a quick efficiency plot to identify best cruise for range. I start suing those numbers combined with landing with 40 gallons and 290 gallons of internal fuel and I get some amazing range possibilities. These profiles will be test in the year to come as the plane makes the air show rounds. The short answer for performance at FL25 is 451 KTAS and about 170 g/hr when the plane levels and accelerates at maximum continuous cruise power (885ish DegC). Another good data point is 350 KTAS at just under 100 g/hr with power setting and temps that would allow the hot section to last a very long time. Compare that to the AI-25 at 150 g/hr and running the motor much harder.

More information about UltimateL39 performance can be found here.