6A Performance/Prop Evaluation

[PCHunt]

Originally Posted by gasman

An incandescent light works just fine.... it also flickers 60 times a second and would show 3600.

I always thought that incandescent lights did NOT flicker due to the relatively heavy tungsten element staying hot through the cyclic voltage. OTOH, fluorescent bulbs do flicker. As do Neon bulbs.

I stand ready to be corrected!

[Robski]

Fluorescent tubes do flicker.
That's why the lights in an engineering shop should be of the correct type to stop lathes and mills looking stationary when they are really going full chat!

The only thing left to point out on this very international forum is that in Europe the mains frequency is 50Hz, not 60Hz.

[j-red]

Was able to fly again this morning and check out a couple of things, albeit pretty gusty conditions and limited flying time kept it short, slow, and at lower altitude.

First, I checked static RPM and it is just about exactly 2100rpm, as was suggested it should be. A possible conclusion, then, is that the tach could perhaps be off at the higher rpm's. I'll have to get a light and test it, but that, to me, seems unlikely since the CPI ignition box can display a tach readout that is driven direcly off of the flywheel magnets and that agrees, at least at the lower rpm's I flew today, with the grt which uses both the electronic ignition and slick mag for tach display.

It was really cold today, so the density altitude at 2500' was practically sea level. What I saw was about 135kts indicated at 2200rpm and leaned to 8gph fuel burn. That's all the faster I wanted to go given the turbulent conditions (it was actually worse up higher). From what I can tell, that's pretty comparable performance to others with the same setup. I still don't know how this engine/prop combo is capable of spinning up so high at altitude, but for the time being i'm just going to throttle back when needed to keep it below 2700rpm indicated.

One more quick question before putting this thing to rest for now: I double checked the temperature during Monday's flight and recalculated density altitude. DA was actually 6500' while doing those 4 runs pictured above where the prop wanted to turn higher than 2800. Should I expect the prop to be able to spin faster at a lower DA, or a higher one? In other words, if I was to fly at a true 8k DA, full throttle, would I expect the prop to turn closer to the desired 2700 rpm, or would it actually want to go even faster than the 2900 it was creaping toward the other day?

[brad walton]

Max rpm will decrease at higher density alt

[flytoboat]

This was mentioned earlier, but a lot of Sensenich propellers have a 2600 RPM limit.

[Kyle Boatright]

Originally Posted by flytoboat

This was mentioned earlier, but a lot of Sensenich propellers have a 2600 RPM limit.

The ones for the O-320 have the 2600 RPM restriction. The ones for the O-360 don't.

[DrillBit]

Doesn't an incandescent bulb flicker at 120 Hz (100 Hz in Europe, parts of Japan, etc.)? Two zero crossings per cycle in an AC waveform....

[Bevan]

Your data boxes on the lower right are mislabelled. Looks like your TAS data field is showing rpm and fuel flow data field may be showing density altitude data. Go to the setup page to change the data field to match the same as the label field for each box.

Maybe change the "Flow" box to "% power" along with the data field and put "flow" on a bar chart added to the lower left.

The attitude indicator is showing the plane about 5 degrees nose high even though you're not climbing. That doesn't seem right at that speed and altitude. The AHARS may need a pitch calibration adjustment as may your magnetometer unless the winds were really that variable and up to 57kts. Poor mag calibration can have a large effect on calculated wind velocity and direction.

Bevan