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Glasair 1 TD (SN 238) Flight Testing

It has been about 9 months since this project was purchased and now the fun begins.

11/28/2007 - Today at 7:15 AM N238SH took to the air piloted by Bob Woolley. Bob has built and test flown several Glasairs and I was really blessed to have his experience in the cockpit for the first flight.

11/28/2007 - The initial flight lasted 30 minutes and overall impressions from Bob were good. I have the following tasks to complete: stiffen the cowling along the top rear camlocs , relocate oil cooler with a naca duct intake, increase carburetor air intake volume by adding a third scat tube, trim the left flap up one half turn to cancel right roll. All of these changes were expected and should be completed within a week to allow test flights to continue. Thanks again Bob.

11/29/2007 - The current setup is pulling oil cooler air from the left rear baffle and venting the oil cooler outflow into the lower cowling. During the first flight oil temps quickly climbed to 210 and stabilized. Slow flight caused temps to rocket to 230. The first change will be to provide a dedicated air source to the oil cooler via a naca duct on the lower left of the cowling. This will also allow more airflow for cylinder cooling since the oil cooler will no longer be using air from the upper deck.

11/30/2007 - Today was my first flight. This hop lasted about 30 minutes to test the changes in the oil cooler ducting. There was no change from the initial test flight reports on temps. Oil temp quickly went to 210 and climbed to 235 by the time I landed. Reviewing the cowling and duct shows that I have 38 sq inches of air going to the upper deck and 11 sq inches going to the oil cooler via the naca duct. Since the engine induction is taken from the rear baffle, about 6 sq inches of the upper deck air is going into the engine. This gives an effective inlet area of 43 sq inches. The outflow from the cowling is extended under the fuselage into a 14 by 2.5 inch duct netting a total of 35 sq inches. I have heard in the past that the cowling out flow should be about 1.3 of the intake, so I need to add about 20 sq inches to get a total of 55 sq inches. That seems like a lot. After rethinking the problem my fist modification was probably unnecessary and the original 32 sq inches of total cooling air should be adequate however the cowling exit should be increased to at least 42 sq inches. Since the oil cooler ducting is in place, I will leave it alone and just add additional area for the cowling outflow. I have added 2 temporary cowl flaps with a total for 8 sq inches for the next test flight.

12/4/2007 - Another test flight showed that the previous modifications to the cowling exit area improved temps. Oil temp took much longer to rise and stabilized at 200 and all cylinder temps stayed under 400. Tonight I started hacking into the cowling exit tunnel to section it out and increase the area. The original tunnel provided a 14 by 2.5 inch exit area (35 sq inches). The new modified tunnel is 14 by 3.75 inches (52.5 sq inches). This change gives a ratio of 1.2 inlet to exit area. I am going to leave the temporary cowl flaps installed until after the next test flight but I think they will be omitted in the final version. I did get a chance on this flight to enjoy the airplane and not focus 100 percent on temps. I even had a chance to do a victory roll.

12/5/2007 - Changes to the lower cowl exit tunnel are complete and test flight shows oil temp at 200 and all cylinder temps around 390. Running laps over the airport at high power settings saw the oil temps eventually climb to 210 however the cylinder head temp stayed in the 375 to 388 range. I am going to tape over the temporary cowl flaps and test again to see if these can be omitted. The next option will be to change the oil cooler ducting back to the rear baffle and remove the naca duct. I still think I am getting plenty of air into the cowling and having problems getting it out the bottom. Some have suggested exhausting the oil cooler out the side of the cowling like the GIII. Tonight I mounted the wheel pants. It is starting to look like a real Glasair.

12/23/2007 - Test flying has been slow with the Holidays at hand and Gym Ratz opening this week. I did have a little time to fly two ship with Link in his RV-6. This picture has been retouched since the cowling has not been painted yet.

3/16/2008 - I finally got around to painting the cowling and spinner this weekend. Looking good.