JUL 81

BD-4 BUILDERS NORTHWEST
NEWSLETTER
Issue 2, July 1981

Dear BD-4 Builders and Flyers,

It is time to get out the second issue of the BD-4 newsletter. I'm trying to get this out so that you will receive it before Oshkosh but everything seems to work against it. Besides a lot of travel for the Boeing Aerospace Company, I've been trying to get my BD-4 ready for another pilgrimage to Oshkosh. Three years ago I felt bad about going without the gear fairings - I still don't have them on! Some of us in the Northwest have made up new 7075-T6 gear legs - I don't have these on either yet. I have also recently made up a new cowling mold (my second - the first had the BD style inlets) with increased air inlet size (about 80 sq. in.). I have it on but not painted. I guess I shouldn't complain as changes and improvements are a good part of the fun of home-builders.

The first newsletter was sent to all the people that Hugo Schneider had on his mailing list. Almost 40 builders responded and indicated that about half were completed with their airplanes. I am including a list of all known builders and have put an asterisk by those who have responded. Please notify me of any people you know of that are not listed. Even if some people are not interested in a BD-4 newsletter or club - it would still be-nice to have a list of builders.

Those of us in the Northwest would like to invite everyone to the Arlington Fly-in on August 28-30. 'Arlington is located on the 350 degree radial from Seattle VOR and at about 50 miles. This is an airplane people fly-in, and there is no airshow except the flybys that anybody can participate in. We do not advertise to the general public although they are admitted for a small fee. There is a lot of nice grass for camping and food can be purchased.

Roger Mellema

ACCIDENTS

W. Baker asked about accidents and causes - these are the ones I know about:

California, 1973 (?) Apparently pilots seat came loose on first take-off. Seat was glued to the floor. Pilot was killed, aircraft destroyed. A "V" shaped piece of metal had been substituted for the flaps. It was just glued to the fiberglass wing. This also could have caused the accident.

Minnesota, 1975 (?) Midair between 182 and BD-4. 182 crashed but BD-4 made it back and landed.

North Central area. Family on holiday flew into bad weather. They think the pilot became disoriented and crashed. All were killed.

There were two airplanes that-went off the end of the runway during high speed testing Weak brakes are still a BD-4 problem.

I've heard of at least 3 different nose gear collapses.

Colorado, 1980. Engine failed shortly after take-off, pilot tried to make it back to runway. -Pilot killed, passenger injured.

Illinois, 1980, Pilot trying to land because of deteriorating weather. Apparently carburetor ice caused the pilot to cut, pattern but didn't make runway. Went under power lines and hit old railroad grade across end of runway. Both survived but with very extensive injuries.

California, 1974. Fuel exhaustion caused landing in 3 foot high wheat. Nose gear collapsed, main gear bent back one foot. No injuries.

California, 1981 FAA says weather related but could have been a total engine failure. Pilot killed.

Washington, 1979. Take-off from rough field on hot day caused right gear to shear ¼ inch bolts on pivot plate. Airplane got airborne but gear fell out of airplane. Deadstick landing with no injuries. Just a little scraped paint.

BD-4 PROBLEMS

I've gone through all the letters that builders have sent and will try to summarize the main concerns and solutions.

Fuel cell leakage

The BD-4 has more than it's share of fuel cell problems but don't feel like the Lone Ranger - many airplanes have the same problem. The best way to insure good cells is to prepare the glass panels before wing assembly. There are many people who think sloshing material is a lot better than it really is and hope it will fill all the cracks and pin holes. The panels should be inspected and the best ones chosen for fuel. These should be checked carefully for flaws and these should be fixed on the inside of the wing using fiberglass (some builders lay another layer of glass on the two end ribs of the tank), The inside of the cells should be sanded until the entire surface is roughed up, (don't sand into the cloth). The surfaces should be cleaned more than once with acetone or MEK - not just wiped but flow it on with one cloth and wipe it dry with another. I then painted four coats of thinned slosh material on all surfaces except the 1 inch edge to be glued. Make sure all the pinholes get filled.

After the wing has been glued together, the tanks are sloshed with unthinned slosh. I like to keep turning the wing while a vacuum cleaner, hooked backwards, blows warm air into the fuel gauge hole. This helps the slosh dry evenly on all surfaces. Be very careful to keep sparks from getting anywhere near the fumes as they are very explosive. I know of one person who blew up a wing.

Some people coat the entire outside of the tank area with a light layer of fiberglass. This works very well but the last time I just put 2 inch strips of glass over the cell joints. The 2216 used on the wings does not have very good peel strength. I had a couple joints come loose on my first BD-4. Av-gas eats asphalt beautifully so I quickly flew away before they decided to charge me for it.

Make sure you fuel test your wings before you go to fly. 'Fill them up to the top and let them set for at least two days. It saves a lot of embarrassment come test flight time.

Main gear problems

Most people seem to have problems with the main gear splaying out. Some of the problem is due to donut hardness and builders are going to harder donuts or a solid aluminum link.- I prefer the solid link as it is light and I feel the BD gear is already too springy.

The 2024-T3 gear legs also bend about 1/3 the length down from the top. Some builders have annealed, bent and heat treated their gear only to have it bend again. Some builders have used a hydraulic jack and some log chain to bend it back. The bending apparently does, not occur from hard landings as much as from creep of the metal when it is parked in a splayed-out position.

Some builders have been using 7075-T6 aluminum and have found that bending is not a problem. It is more brittle though and it should be polished.

The pivot plate of the gear has also been a problem. The four ¼ inch bolts tend to elongate and shear off. Several builders have gone to six 5/16 inch bolts in an enlarged pivot plate. The plate can be made larger either up or down the gear leg. The old plate is welded to the new plate. The pivot plate is not nearly as much of a problem if the solid aluminum link is used instead of the rubber donut. The donut allows the top of the gear leg to move fore and aft to some extent. This means that when you touch down at 80 mph, the only thing that keeps the gear from folding back are the four little bolts in the pivot plate. The aluminum link is bolted in solid and does not allow the very top of the gear leg to move. The "arm" for the resultant forces is much longer in the case where the aluminum link is used and as a result there is less stress on the pivot plate bolts. There will be a slightly greater load on the landing gear box where the bottom bolt of the aluminum link is located.

Many builders have beefed up the landing gear box. Some have strengthened up the box itself and almost everybody has strengthened-, the box sidewall (C channel) connection- The bolts in the C channel are countersunk and always seem to work loose. The C channel wall' should be strengthened by adding a 0.063 aluminum plate about 12 inches long on the inside of the C channel. Some people continue the plate along the bottom of the fuselage so that the hole for the landing gear is also strengthened.

Tail wheel problems

The BD design for the tail wheel attach is ridiculous. I have seen two solutions to strengthen it and will draw them up for the next newsletter.

Nose gear problems

No one really complained about the nose gear except to say that the J. Murphy or the Val Barnhardt nosewheels are much better than the original system.

Fuel system

Some builders have had fuel starvation when they have a high angle of attack. The fix, according to some builders, is a three gallon header tank on the firewall My BD-4 is built according to plans and I've never had a problem. The problem I have had with fuel is that with large tanks (5 cells on each slide) a slight "off ball" condition will cause the fuel in one tank to be inboard and outboard, in the other. This is not much of a problem if you have a both position on the fuel selector. If I'm low on fuel, I watch the ball very carefully!

Remember that if a header tank is used, it must be vented up to the tops of the wing tanks.

The fuel selector can be modified to have a both position but the FAA requires that the tanks then must be vented to each other. I had a both position on my first BD and it worked alright without a common vent.