Triplane Builder

Articles by Triplane Builder - William (Bill) Woodall

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Learning From Flying

Most pilots like to read about the experiences of other pilots. It is presumed that these add to their "data base", and may provide some ideas about what might be done, should a similar situation arise for them.

I am not so sure about this premise. Most people probably react to what is happening, and think about it later.

My account will probably be of little use to pilots who may read it.
Who among you is thinking about test flying a reproduction of a 1916 triplane?
Who of you would be using a World War 1 rotary airplane engine? (Where the crank is stationary, and the engine spins with the propeller)
Who is going to fly with no brakes and rely on a tailskid for stopping?
(It's also pretty hard to find anyone willing to check you out for doing this for the first time).

I had spent a large chunk of my life putting together a reasonably accurate reproduction of a Sopwith triplane, even using the wooden box girder fuselage construction of its day.
I did deviate from the 130 HP Clerget rotary,(I couldn't find one) and substituted an 80 HP LeRhone for its engine. (I did install all of the Clerget mountings in case one ever turned up). I spaced the LeRhone forward, and extended the hollow crankcase tube so that the carburetor and intake pipes occurred in the right places.

I read everything that I could about operating rotaries, but there isn't much to read.
There are two levers that control what passes for a carburetor. One operates a needle valve that regulates the volume of gasoline entering the carburetor, and a second that operates an air gate, along with a second needle valve. The engine is primed by depressing each exhaust valve, and squirting raw gasoline at the spark plug. Once the engine is running, you adjust the levers to get the maximum RPM-somewhere around 1200, and then you try to idle it down so that it is ticking over at about 450. There is also the well-written-about "blip switch" or "coupe' button". This protrudes from the center of the spade grip on top of the control stick. It grounds the single magneto and stops all firing. (The use of this sounds good on WW1 movie sound tracks but should be used judiciously. The spinning engine continues sucking fuel and air, so when the button is released, the engine resumes firing. There may be a volatile mixture collected within the cowling. A cowl fire can result with an attendant explosion that blasts out through the breather pipes. This can be spectacular and somewhat unsettling).

Rotaries need slipstream airflow for adequate cooling, so my ground run-ups were brief.

Before proceeding, it would be well to make known some construction details that will play a role in what was to happen.
Forward of the cockpit, and on each side, are "side shields"- aluminum coverings that are removable for interior servicing. Each side shield contains a rectangular door for access to the carburetor. These doors are affixed by spring loaded, rotatable latches. The aft end of each shield is secured by cable. These cables are anchored to the top longerons, and are tensioned by eye bolt devices attached to the lower longerons.
A large, one-piece aluminum cowl covers the nose of the airplane, and collects the castor oil that is slung from the spinning engine. The front edges of the side shields nest under the trailing edge of the nose cowl. A turnbuckle-tightened cable wraps around the rear of this aluminum sandwich and squeezes into a contoured steel ring that is directly below.

When the big day dawned, I went to the airport, accompanied by a commercial pilot friend who could drive my car home in case this wasn't a success.
I had told only the airport manager of my intentions, but there was large group of people on hand.
The airplane was pushed to the grass between a runway and a taxiway. Taxi lights had been removed from one turn-off, so that the blade on my tailskid would do no harm.
This airplane is difficult to enter. There are anti-drag wires bracing the lower and middle wings. These extend past the cockpit. They have to be negotiated while searching for the narrow step on the rear spar of the low wing. You then stand in the seat and lower yourself in. Since I saw no way to do this while wearing a parachute, I was going to be flying like the guys who did it for real. When seated, only your head is visible above the cockpit coaming.

The engine proved difficult to start on this chilly morning, but finally accepted gas from the main tank, and began running well.

With the engine wide open, I waved the chocks away-- corrected my alignment so as to be parallel to the runway-- and eased the stick forward. The tail came up immediately, and with slight back pressure, I felt the wheels leave the ground. Since this was to be a test flight, I thought I should check the airspeed indicator. To do this, one has to duck his face into the cock pit and get below the crash padding on the rear of the Vickers machine gun.
When I got it in view, it was reading zero.
OK-this was a good excuse to land and call it a day.
I looked overboard, but the plane was far too high to get back on the grass. The old girl really climbs. I was going to have to fly by "feel", only I didn't know what "feel" was supposed to be like-I climbed to do a pattern-(the altimeter seemed OK)- and turned crosswind. Even though the airplane has 6 ailerons, it took a lot of rudder to get it around. On downwind, I reduced throttle and realized that I had been flying cross-controlled-left stick, and right rudder to stay level-I had mis-rigged it. I didn't want any steep turns, so when I turned to final, I was not at all lined up for the grass I needed to use.
The next attempt was equally bad, although I carried it out to a lower altitude.
As I went around this time, I could hear a howl-- and then-the right side inspection door popped into my sight, and disappeared. Almost at once there was a grinding noise and much vibration. I accelerated the engine, and the vibration was somewhat reduced .As I was about to turn to base on this third approach, the entire right side shield disappeared aft, accompanied by a change in the way the airplane flew.
This time I was going to land-come what may! I set the levers for slow running -got myself aligned, and began breaking the glide. Just at stall, the left wings started to drop, but a hard shove on the rudder bar corrected things, and the airplane dropped into a 3 point landing. The tailskid dug in, and we barely rolled a couple of fuselage lengths.

When I climbed out, I was startled to see what my airplane looked like. The nose cowl was tilted into the propeller-the right side shield was gone, and the interior quite visible.

In retrospect-the door fasteners had vibrated out of their locked positions, and the door blew open from the front. Its drag slid the right sideshield back from under the nose cowl cable, and the loosened nose cowl went forward onto the spinning engine and into the trailing edge of the wooden prop. When the side shield got loose from its rear cable it tumbled aft and hit the flying wires bracing the stabilizer. This caused an incidence change for the right side.

The main thing that I learned from this is don't trust eye-witnesses. The people on the ground thought that I was having a ball.

I guess the old adage "fly the airplane" or what's left of it, applies.

I did change to more secure door and cowl retention methods, and the next flight was far less demanding.

Bill Woodall

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