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Cozy MKIV - Eighth Flight Test

Date: August 17, 2002

Friday I started to fabricate an air scoop for the oil cooler to get some dedicated cooling air, and waited around for a while to see how the tiedowns worked in 40 mph winds during a thunderstorm that made me stop working on the oil cooler scoop -).

Saturday I got to the airport around 8 AM and did a preflight. It was cool enough that I decided to start the climb measurements. I had a data sheet to log info according to the recommendations in Ed Kolano's articles in Sport Aviation from October, November, and December of 2000. The object here is to establish a climb at a given speed, pass through a threshold altitude and then measure the time it takes to pass through a given altitude block. Using this data, I could then calculate the rate of climb and Vy (just the speed at which rate of climb is maximized, or the interpolated value thereof), and with a bit of math and data manipulation, calculate the angle of climb and Vx (the speed at which angle of climb is maximized, or the interpolated value thereof). By measuring the OAT at the midpoint of each altitude block on the way back down, I can calculate the Density Altitude, and create a graph of climb rates at velocity vs. density altitude.

I took off from FIT and headed toward (wait, I'll let you guess)........ YES, you're right - Mt. Wachusett! I leveled off at 1200 ft., and chose to use 1500 ft. as the base altitude for the climbs. This would allow me 300 ft. to achieve a constant speed and rate of climb before starting my altitude gain measurements.

The flight would be climbs from 80 mph to 130 mph, timing climbs in 1000 ft. blocks, with 500 ft. of "dead" time between blocks to write data and stabilize speeds, etc. All runs would be at weights between 1570 lbs. and 1510 lbs., depending upon fuel usage. During the descent (from 8500 ft. max. altitude) for the next speed run, I would stabilize altitude for 1 minute at the midpoint of each of the climb blocks to read Outside Air Temps. for Density Altitude calculations.

Turns out this is a lot of work, especially at 1000 fpm - 1500 fpm climb rates -). I found it kind of difficult to stabilize speeds perfectly, especially at low, bumpy altitudes, while writing down times, punching buttons on the timer, watching out for traffic on a busy day, and trying to stay right side up -).

At any rate, I did a run at 80 mph, descended, did a run at 100 mph, descended, and came in to refuel (for weight reasons).

Next run was at 90 mph (in which I forgot to raise the nosegear), descended, did a run at 110 mph, descended, and came in to refuel (for weight reasons).

The next run was a redo of 90 mph, descended, did a run at 120 mph, descended, and then flew from FIT over to ORE (Orange Airport) in mid-north MA for a picnic lunch with John Vance and his EAA chapter 726.

On the way back to FIT from ORE, I did the 130 mph run and the descent (duh).

There are a LOT of data points, but what it boils down to (at least at this weight) is that my Vx seems to be at around 90 mph, maybe a bit more, and the Vy seems to be at about 110 mph. However, the rates don't seem to be very sensitive - the climb rate is not substantially lower at 100, 120, or even 130 mph. I will be redoing all these measurements at different CG's and weights as the flights go by, so I should get better at taking data, and should be able to start getting a more accurate handle on the numbers.

One thing I found was that the oil temps stayed in a pretty reasonable (given the temps I HAD been seeing) range during the 120 mph and 130 mph climbs - I don't think they ever got above 220 deg. F. I know that's still pretty high, but the temps were reaching 240 deg. F. on the 80 - 100 mph runs. I'll still work on the oil cooler scoop when I get back from vacation next week.

So, trying to get a handle on what the next series of tests will be, I think it looks like:

Power off stalls
Power on stalls
Accellerated stalls
Slow flight (gear up and down)
Climb Tests

All at weights ranging from 1550 lbs. to 2150 lbs., and CG's ranging from 97.5 in. to 102 in. That's a stack of data - I think it'll easily take 10 - 20 hours of flying to get that all in.

After that will be longitudinal and lateral stability and flutter testing.......

You can read the Flight Test Protocol and test results for Flight 8.

End Date: August 17, 2002

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