Flight 7: Two Issues Fixed

I took my Bede BD-4C airplane up for its seventh flight yesterday. Everything was smooth sailing, so to speak.

Intake Manifold Repair

On Thursday evening, I had ended my sixth flight with the engine backfiring badly. My mechanic discovered that the intake manifold had come loose from cylinder #2.

In the photo above, you can see that the manifold is hanging from just one bolt; the second bolt is missing entirely. To fix it, I removed the old gasket from the intake manifold, installed a fresh one, and replaced the missing bolt. I also checked the bolts on the manifolds on the other three cylinders.

Flap Adjustment

The left wing was also a bit heavy, meaning that if I took my hands off the controls, the left wing tended to slowly drop and the plane started to turn left. The wings should stay level and the airplane should fly straight, even with my hands off the controls, much like a car will drive straight even if you take your hands off the steering wheel.

I adjusted the flap on the right wing upward, reducing the amount of lift that the right wing generates. This is a simple process. I remove this rod end from the flap mechanism and give the square block a couple of turns so that it is higher up on the threaded part of the rod end.

Since you are an attentive reader, you are now puzzling over that photo, wondering how in the heck I could remove that rod end since the bolt cannot be removed. You are right, of course. That is a “before” picture.

I had assembled my flaps from the original plans for the airplane, drawn in 1968. After I did that, Bede Corp. updated the plans, indicating that the rod end should be on the other side of the black weldment and the bolt should be installed in the other direction.

I had to cut the end off the bolt and reinstall the rod end according to the new instructions (with a fresh bolt). Now it looks like this.

Flight 7

With those tasks accomplished, I test ran the engine. Everything was fine, no backfiring. I reinstalled the cowling and took the plane up for flight #7.

The next test in the EAA Flight Test Manual is a fairly time-consuming set of short flights to measure the speed which produces the best rate of climb. I did not want to do that yesterday so I opted for a short flight to

• Check whether the left wing was still heavy,
• Get a feel for flying the plane at 20 degree and 30 degree bank turns, which are pretty typical for the kind of flying that I do, and
• Check the cruise speed at 65% power, which is typical for how I will probably fly the airplane on cross country flights.

I flew north from my airport, climbed to 5500 feet, and leveled off. At that altitude, 65% power means setting the propeller for 2100 RPM and opening the throttle all the way. The airspeed indicator (ASI) showed a very pleasing 129 knots (148 MPH) and the airplane flew straight and level when I took my hand off the joystick. So far so good with two tasks checked off my list.

For the turns, I started by doing a full circle to the left and then a full circle to the right with the wings banked 20 degrees. It was super easy to fly, even easier than my Arrow had been. Once set into a bank, the BD-4C tends to stay right where it was put with very little pressure on the joystick.

I have noticed that I use the rudder differently in the Bede BD-4C than I did in my Piper Arrow. When I started a turn with the Arrow, I would begin with both aileron (turning the control wheel) and rudder (pressing the pedal with my foot). With the BD-4C, I start with the aileron (moving the control stick) and then very slightly afterward, I add opposite rudder (more than the Arrow required). It takes more words to describe than effort to do. Mostly it is notable just because it is different from what I was used to.

I tried two more turns at 30 degrees of bank. These were just as easy as the 20 degree bank turns.

Then I horsed the plane over into a 60 degree bank and did a 180 to head back toward the airport because hey! it’s fun!

I climbed up to 6500 feet (going westbound, you should be on an even altitude + 500 feet, eastbound you should be on an odd altitude + 500 feet) and tried one stall, to see if my flap adjustments helped in this department, too. The left wing still dropped but less quickly than on Thursday and it was easier to bring the airplane back to level flight.

Exhaust Gas Temperature

I have an MGL iEFIS (Electronic Flight Instrument System) installed. Among the things it monitors is the exhaust gas temperature (EGT) for each cylinder. Other airplanes that I have flown have had a single EGT gauge, monitoring just one cylinder. That is useful for setting the mixture for best fuel efficiency but not for spotting problem with the engine.

Here is the graph for the EGT during the flight after I repaired the intake manifold.

Here is the graph for the previous flight, when the intake manifold was loose on cylinder #2 (the orange line).

You can see that the #2 cylinder was not right; the EGT was consistently low starting 15 minutes into the flight. When I landed, the manifold dropped away from the cylinder head and that cylinder stopped operating. You can see that the EGT basically dropped to 0.

There is a lesson for me here: Remember that I have four EGT gauges available to me in flight. Pay attention to them and, if I see something amiss on one cylinder, consider landing and checking it out. Had I done that on the March 19 flight, I would have seen the problem develop 15 minutes into the flight and returned to the airport.