A few specs here:
4 OS 15 FP's.
Custom centuries to clear the cowl.
Central bladder feeding the 4 engines.
Pressure regulators on each engine due to the change in fuel pressure to each due to tank location and fuel head from the lateral acceleration.
Each engine had a cam operated fuel cutoff switch. This allowed priming and running out of the prime when the bladder was loaded. Extremely critical to 4 flip starts.
The outboard engine had a fuel pressure cutoff switch. As Brett pointed out, it would run long without it due the the fuel pressure regulator sensing enough head pressure it would stay functioning even after engines 1-3 had quit. The switch was devised to block the flow if the pressure dropped to 5 psi. This valve became very sensitive to any dirt, or the "time of the day" and would not function. Many variants were tried, but none panned out. This was the "best" solution at the time.
The starting procedure was complicated, but totally necessary as FAI rules back then required the pilot to hand start it and there was still starting points for takeoff in one minute. At the World Champs, I flew 7 flights and used 30 flips to get it going and never missed starting points. Key was Howard's glow power system. After we discussed how it was going to work, he built a starting box with on-off switches, voltage meters with 4 complete individual power connections to ignite the glo plugs.
The procedure was to load the bladder and remove any air in the lines. Then all four battery cables were attached to the motors with small alligator clips. Of course, all four by fuel switches were closed. Engine one was then primed and started. It would run the fuel out. I would repeat this until I was satisfied it was warn and clear of fuel. Then I would spray a mist of fuel in the venturing and check for a bump. Once there was a bump, that engines battery was turned off so it would not burn the prime out. This process was repeated until all 4 were ready. Then power was returned to engine one, and signal given, flipped and it fired and as soon as it was running well the fuel switch was opened and it continued to run. Then power on to two, and the process repeated until all four were running. Once I gave Howard the nod he would simply pull the power supply back disconnecting all the power cables. Then takeoff. The timing of EVERYTHING in the process was critical. Getting JUST the right amount of prime, waiting that split second to open the pressurized fuel to each engine was quite critical. Too soon and it could flood the motor, too late and it wouldn't catch. Thiscall took some practice.
But there's more to the story. What had to happen before that was it had to be test run and the needles set. That took time. From the time I hit the field with it it would take one hour before it was ready to fly. Assemble the plane, which took more than a few minutes, test run each engine separately then all together made for a lot of effort for just one flight.
The aircraft:
It weighed 105 ounces. It is just amazing how fast the power system weight adds up when there are four engines. That included lead in the nose to balance it.
It spanned 76 inches and had about 900 square inches.
The fuse was molded shells, and split just forward of the wing. This allowed it to get in a "reasonable" size box for transport. The wing was removable and split in the middle. The tail assemblies were all built up, open bay structure to minimize weight as it was so far aft.
The cowls were removable and FANTASTIC works of art from the shop of Howard. They are carbon fiber, and weighed around 3 or 4 grams each before paint. The mounting method for the motors is another LONG story which I won't repeat here.
Flying: as Brett mentioned, the line tension was significant and always there. It got to the point that I could only fly it three times a day otherwise my shoulder would be in too much pain to fly again soon. It was fairly well balanced between corners and rounds, but still had significant "stick force", probably due to its significant size flaps. I had to fly it faster than I really wanted as the weight required more lift to function and the only way to get that was with more speed.
It was painted as the 909, which was the B-17 with the most missions in Europe in WWII. It survived the war, but was damaged badly in the US doing flights for shows. It was rebuilt using a different "hulk", but still called the 909. It is with the Collings foundation and still flies each year. I got a picture of it and my model together a number of years ago while it was in Seattle.
I wonder if I could still fly it now. I was lifting weights seriously when I was flying it, but not as serious with the weights now, and nearly 20 years older. It might just hurt too much.
Topic: At Last; Paul walkers B-17 . Flight . (Read 3881 times)
