Showing posts with label aircraft electrical. Show all posts
Showing posts with label aircraft electrical. Show all posts

Wednesday, July 22, 2009

Starting the de-bugging

Now that I proved that it can fly, I need to get after all the squawks. Right now, the main issues are engine heat and power. Yesterday I went out and:
  1. Adjusted elevator push rod for better roll trim.
  2. Significantly opened up the path for cowling discharge air.
  3. Discovered air leak around #2 cylinder. Will repair after next test flight.
  4. Took care of fuel line chafing on cowl.
  5. Plumbed in an airspeed indicator to measure cowling pressure differential.
  6. Hooked up mixture meter so I can observe it in flight. I will continually be checking the fuel/air ration to fine tune the EC3 mixture mapping.
It started raining so I didn't fly.

Regarding item # 5 above. There are a lot of factors about engine cooling and there are several great articles out there if you are willing to search for them.

One of the fundamental things to check for is to make sure that you have an adequate pressure differential between the top of the engine, compared to the bottom of the engine. The engineers like to refer to this as inches of water, as seen in a manometer. Let's say you had no baffling at all. In that case there would be zero pressure differential and zero inches of water.

Lycoming wants to see between 5 1/2 & 6 1/2 inches of water. Since rigging up a manometer can be cumbersome, there is an easier way, using an airspeed indicator. I had an old one laying around so I hooked it up kind of like this (scroll down a bit).

If I don't have enough pressure differential, that should be addressed first. But, if there is enough difference, then I need to go after different things like controlling air flow around a specific component, but first things first.

So looking at the table below, I will be hoping to get about 110 mph on the indicator.

MPH KNOTS IN. of H2O #/IN2
30 26.1 .44 .016
40 34.8 .79 .028
50 43.5 1.23 .044
60 52.2 1.77 .064
70 60.9 2.41 .087
80 69.6 3.15 .114
90 78.3 3.99 .144
100 87.0 4.92 .178
110 95.7 5.95 .215
120 104.3 7.09 .2558


I'll report my results later.

Saturday, October 25, 2008

All Things Electrical

I've been trying to concentrate on all of the electrical items from the firewall aft. This is cool, since I am actually bolting parts on the airframe, and the piles of parts in boxes are getting smaller.

With the exception of the wiring, I have the instrument panel largely complete. The Biggies are; handheld GPS dock for my old Garmin GPSMap196, Dynon D180, ICOM A210 Com., Transponder, and RWS ECU programming panel. You will also notice about 20 pounds of switches, used to control the ignition/injection/fuel pumps. As always, click on the photo for more detail.
On the backside of the panel, you can see two fuse blocks, a couple of diode sets and a couple of switching relays.

Throughout the airframe, I've also installed the engine and battery busses and contactors, the voltage regulator and filter capacitor and the big ammeter shunt device.

Soon, I'll get some preliminary wiring done on the panel, then get it permanently installed.

The biggest challenge, right now, is sizing the batteries. My load analysis shows that I'll need about 13 amps to keep this thing in the air. To make my system redundant, I'll need a backup battery capable of delivering 13 amps for a half hour. Yeauch!

I figured out how and where they should go, I just hate adding all that weight.

Sandy said I should just eat less and get some exercise and not worry about the battery.