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BD-4 NEWSLETTER #27 - April, 1999

Roger Mellema
17605 SE 288 Place
Kent, WA 98042, Ph:253-631-5324
rmellema@halcyon.com (or: roger.d.mellema@boeing.com)
http://www.halcyon.com/www2/rmellema/BDindex.html

The editor of this newsletter cannot verify that the information contained herein is accurate. This newsletter Is only a clearing house for the Ideas and opinions sent In by various BD-4 builders/owners. Treat this information as if you overheard It during a "hangar flying" session at your local airport. rdm

Dues:
The number before your name on the address label tells you how many issues you still have coming (a "=" indicates you have already gotten some free). The cost per issue (5 double-sided pages) is about $2.50 (this one is $5.00 as it is a double+).

Greetings!
A lot of news has come my way and it is time to pass it on.
Oshkosh was a great success and our newest flying BD-4 was judged as winner of the Hugo Schneider trophy. Congratulations Steve Knight! Steve was very happy to be at Oshkosh and to win the recognition of his BD-4 peers ... I'll bet he didn't even mind the flat tire on departing Oshkosh and the weather that plagued him on the way home!
The best way to see who was at Oshkosh with their airplanes is to visit my home' l page listed above. For those of you without web access they were: Tony Castellano, AI Darby, Cecil Hopkins, Paul Kauffman, Joe Lienau, Steve Knight, Dick Marker, Roger Mellema, Deene Ogden, Joe Thalman, and George Wittet.

New owners of the BD-4 design:
 Jim Bede has sold the design rights to the BD-4. Tennessee Valley Aviation Products is the new owner. They say the web address will be http://www.tvap . com (I have not yet gotten this to work). Email is: tvap@ro.com
Charlie Musitano has been named president and he can be reached at: 2225 Drake Ave. Suite 17, Huntsville, AL 35805. Ph: 256.704.2728, Fax: 256.704.8828
Here is a portion of their mission statement:

TVA Products was formed in 1997 with a mission to make quality kit built aircraft available to the general public at an affordable price and with factory built levels of safety. Our plan is to begin by producing two, four and six place owner built kit planes. We will strive to provide our customers with their choice of parts, kits, quick build kits and a factory supervised "Kit Kamp" for each type of aircraft. In accordance with our mission we will ensure that the original designer of each aircraft has certified any part being offered and will assure quality to the level of the designer approved part. As you are well aware, of each 1000 plans and kits sold - typically 5% are completed. We expect a paradigm shift in the way kits are sold, built and flown, as a result of our effort. We will work with existing suppliers to simplify and enhance inventory, handling and shipping for kits and parts. If you produce parts for one of our kit planes we want to buy our parts from you. We prefer partners to competitors.

The first kit we are introducing is the BD-4 aircraft. We are pleased to announce that TVA Products has recently acquired the world-wide rights for the manufacturing and marketing of the BD-4 aircraft. For those companies and individuals associated with the BD-4 this acquisition opens new and exciting opportunities. Mr. Jim Bede, designer of the BD-4, has agreed to consult with TVA Products to certify parts, design improvements, and any desirable or required modifications for inclusion in the evolving design. As designer, he will continue to work with us to move the BD-4 kit airplane forward.
You may have heard rumors concerning the acquisition of the BD-4 and our plans for it. Allow me to clarify our plans and objectives:

We would like to offer you the opportunity to participate in the revitalization of the BD-4. If you are a former supplier to Bede, limited supplier of BD-4 parts, or want to become a supplier to TVA Products please contact us at our Huntsville office. If approved as a supplier you will be added to the drawings and bill of materials (BOM). Our three-dimensional CAD drawings of the BD4 are scheduled for release October 1998.

Editor Update: Scott DeGaynor and John Gill recently took an around the country BD-4 trip and visited TVAP. TVAP is running a little behind schedule as they are changing the cabin to make it more comfortable. The extra 2 Inches in height will please a lot of people. Some of us do worry about bumping out heads on the spar. The good news is that everything is going into a CAD system which should make it easy to develop the specifications for manufactured parts.
Part of the TVAP crowd is located near Las Cruces, NM (as reported by Mike Quigley). Mike saw a BD-4 fuselage and a fiberglass wing displayed at their annual aviation day event. This part of the team call themselves "Adventure Air" and will also have a building center.
TVAP is trying to get a revised-plans aircraft frame to Oshkosh to get the Interest started.

V-6 Powered Canadian: Roger VandeWeghe (519.337.9535)
Empty weight is 1400 lbs., cruise 150 mph, using a Warp Drive prop.

 

Memorial Day Picnic:
We had a great BD-4 picnic on May 25, 1998. I didn't get a count of people present but it was a little low due to the weather (summer doesn't reach Seattle until late July). The picnic is an annual affair and you don't have to call before coming.

The next picnic is on May 31 1999. This is an "uncoordinated" potluck so bring whatever you prefer in large enough quantities to feed you and your guests. The place is: Crest Airpark which is southeast of SeaTac airport near Seattle, WA. The time is: from 12 noon on - we usually eat about 2 PM.

A Walk on the Wild Side:
 Ray Ward has inspired a lot of people with his work on high powered and racing engine BD-4s. He has a "lessons learned" story for you:
I think something like an AD needs to be put out to strengthen up or at least inspect the pilot's seat on any BD-4 that has an engine over 180 horsepower. The BD Super Sport accelerates very hard with the 475-hp engine and 3 bladed CS prop and after 798 hours on the airframe, first with a 300 hp Lycoming, then the V-8, the seat back broke on take-off.
As we were taking off in a strong left cross wind the plane started drifting off to the right. I already had full left aileron, so full left rudder was applied, and then hard left brake was applied since the plane was still drifting to the right. By this time the plane was going about lift-off speed. The seat back brake due to acceleration and probably pushing hard against it for braking. The plane became airborne with me looking at the cabin roof. I had let go of the stick and throttle. I was afraid that plane would zoom and stall, so I managed to struggle against the acceleration to grab and close the throttle. This allowed me to sit up in time to see us headed down with the left wing low. The plane had almost snapped to the left with the full left rudder and was near stall speed. The left wing tip hit, then the plane bounced over to the right wing tip, and broke off the right wheel. It was a round steel Cessna 172 LG leg. Nobody was hurt, and though fuel was pouring out of the right wing, there was no fire. The right wing fuel tank, wing tip, LG leg, side channel and wing tip, as well as the left wing tip, and propeller and cowling were damaged. The plane is disassembled and stored in my hangar.
I examined the broken seat. The BD Super Sport seat was made by Gordon Moore, and though it is a little different than Bede's seat, it appears to be made of the same 1" diameter, 0.062 " thick wall aluminum called out for the BD-4. Therefore, I think it would be prudent for anyone using this seat back to put a piece of 7/8 " diameter material inside the tube and at least halfway up inside the tube as a doubler, or some other method be done to strengthen the pilot's seat.
I remember one time Jim Bede said "the single most important part of an airplane is the PILOT". Check that seat if you are using high horsepower.

And the Really Wild Side:

Ray Ward has been working hard on the "Ward Aero" (Super BD-8) that was shown in a past newsletter. The FAA inspectors made him further extend the landing gear for better prop clearance. He had done extensive taxi tests and had worked up to a couple of 60-mph runs. Then as he slowed down (about 30 to 40 mph) the left weldment that attaches the axle to the fiberglass leg broke in two. With the wheel gone the leg stabbed into the turf and there went an expensive propeller. The plane slid around 180 degrees bending the tail wheel spring and left aileron. Then the right landing gear weldment also failed.
The BD-4 type landing gear box was torn apart and pulled outward about 1 /2 inch which moved out the engine mount / longeron just above the leg. He will have to remove the engine, fuel tank, etc. to work on it.

"Build Your Own Airplane" books:
Joe Lienau has been keeping a few of these great books on hand until Bede or TVA produces more of them. He can be reached at: 630.985.8244

Needs:

 

Autopilot update:
Yes, more on the long winded tale about autopilots .... but now I have a solution! If you will remember, the autopilot is an S-TEC series 40 wing leveler. Knowing that the BD-4 has a bit of adverse yaw, the worry was that the autopilot would get confused and it certainly did, even with 'spades' added to the aileron counter-balances. The spades give extra drag to the 'up aileron' (down counter-balance) side and allowed the balance lead to be placed out further and therefore to use a smaller amount. The spades helped a great deal with moderate aileron movement but they did not affect the 'inside wing' drag enough to allow the autopilot action to be robust.
We all know that the BD-4 is a 'rudder' airplane and so it would make sense to connect it to the autopilot. The rudder actuation is with cables, which do not lend themselves to easy hookup to an autopilot. Mounting of the autopilot servo in the rear of the fuselage where a pushpull tube can be used is difficult when the removable panels are not large enough (I hate to ruin the paint job!).
The bare top of the main landing gear box with the rudder cables running over it looked like a good opportunity to at least test a "rudder" wing leveler. A heavy-duty flexible actuator cable, a bellcrank, some pull arms, and some common hardware allowed completion of the hookup. The bellcrank arm ratio was adjusted so that the rudder still had full throw and so that the servo moment arm was correct (didn't want to move the very sensitive rudder quickly). It did help that the servo had to turn the tailwheel along with the rudder.
The test arrangement had a bit of slop but even so, the autopilot worked perfectly. My daughter and I flew to a wedding in Minnesota and it was used during the whole trip. It even worked well in moderate turbulence. It will work better when it is permanently mounted with a push-pull tube to the rudder bellcrank.
Now to buy a GPS error signal converter and a 'heading bug' directional gyro. Just found a reasonably priced signal converter (see below).

GPS Converter: Roger Mellema (253.631.5324, rmellema@halcyon.com)
 Do you use a portable GPS and wish that it could drive your autopilot? Now you can use the "Track Wizard" to do just that. This has been done before but now the price is better!
All handheld GPS units (that I know of) put out their error signals in a digital format called 'NMEA 0183' (NMEA is National Marine Electronics Association). Our autopilots still use the ages old method of analog error signals (go left if -, go right if +).
These units are only $119 and are beautifully small. Contact:
Tru-Track Engineering Ph: 540.341.7227 6824 Sandstone Ct., Warrenton, VA 20187-9315

Propeller Answers: In the last newsletter Allan Franko (allanf@CancerBoard.ab.ca) had comments and questions about propeller changes. Bob Hoey (805.948.1102, hoev@tecnet1.jcte.jcsmill gives the following answer:
Your explanation is correct, except that it has little, if anything, to do with the fact that the prop is made of wood.
If you had only changed the pitch, I would be confused too, but you reduced the diameter from 74 to 68 - a big reduction in disk area. The reduced propeller diameter will allow the RPM to go up - the increased pitch will bring the RPM back down (all other things being equal). The lucky combination you hit on gave you almost the same RPM, and same shaft horsepower near cruise speed. The higher pitched prop (wood or metal) will reach its peak aerodynamic efficiency at a higher speed than the lower pitch. It is therefore converting more of that shaft horsepower to thrust and overpowering a little more of the airplane drag - so you go faster.
Conversely, at low speed (climb) the low pitch prop is more efficient (again, wood or metal) and it will give you better climb performance with the same shaft horsepower.
The overall difference in efficiency between a wood and metal prop with the same diameter and pitch is generally pretty small. I can almost guarantee that a metal prop that was 68d-67p would give you the same results. (I wish I could find one !!!!)

More Prop Answers: Fred Hinsch (604.520.7662)
My first prop was a Warnke "almost constant speed, 68 x 74, a beautiful piece of work. Unfortunately it did not develop more than 2100 static RPM! So I phoned Bernie and sent it back for repitching. It took almost a year to get it back and imagine my disappointment when my RPM now was only 2150. Back on the phone again. This time I asked him to sell it. He did but I took a big loss.
Next I had a prop carved locally. This was a 68 x 66 and RPM was still low. Back it went for repitching, to 68 x 64. This was the optimum for a prop of this diameter, at 2300 RPM on climb out at 90 mph.
This prop lost a blade in flight at 4000 feet after some stalls and steep turns etc. and only quick action saved the day and the BD-4.
Needless to say that was the end of my flying behind wooden props. A Sensenich prop of 72 x 56 was the choice. The model was DTM6S8, cut down to 72". The pitch was not right and it was changed to a 52" pitch. This gave me a 1500-1800 ft./min. climb out but only 130-mph cruise. However, I stuck with this prop until a nosegear failure destroyed it.
After searching for months for a replacement, I realized this was not a commonly used model. I now looked into a Warp Drive prop and got good reports from two guys in Ontario who use one on the Bede. So I contacted Warp Drive and they recommended a four blader with nickel leading edges costing $1,375 plus $225 for the 14" spinner which will enclose the hub. A cheaper 7" polished spinner is available also for $100 but does not enclose the hub. These props are ground adjustable. I did not go for this prop for reasons of money. Instead I bought a McCauley 75 x 53 prop and had it overhauled. My cruise went up dramatically but there was a tradeoff. Climb speed is only 700 to 1000 ft./min.
As you can see finding the right combination is not an isolated problem. My airplane is tri-geared, 150 Lycoming with 30' metal wings and weighs in at 1280 lbs. empty.

Folding Wings: Fred Hinsch (604.520.7662)
As you know, I have built the folding mechanism as per Bede drawings. This functions very well but is definitely not a one-man operation to fold the wings and load it onto a trailer. The airplane is tail heavy in that configuration and needs to have the nosegear secured. Also the doors cannot be opened.
This is no problem if you want to take it home and then remove the wings. The wing rack is needed for sure and works very well. I made it so that it could be slid apart further and then locked with a bolt. The wing hangs on the tie-dawn rings but a pin must be over the top of them with the wing hung on the tube. The only difficulty in building this mechanism is shimming the center section so the tubes will easily slide onto each other. These should be well greased. I made a tool to wedge the wing off and on again as Bede shows, out of a scraper, cut off to leave only the shaft. This tool is 4.75" long and 5/16" thick and of hardened steel. It has worked well and never bent!
Ed: Fred sent me negatives of the folding process. I can get some prints made If anyone needs them.

Wing Extensions: Larry Parham (918.786.3846, shack@greencis.net)
Just to let you know I finished building my wing extensions, flew 1 time and it did make a difference. I will take notes the next time I fly and do a write-up of the changes.

Built-up Spars: Dave Rice (515.732.3676, metal@netins.net) I had spars completely drawn up, and had done a structural analysis. The spars are basically like a Vans RV wing, but somewhat simpler to build and a whole lot less expensive the Dream Aircraft's spars. Then I spoke with J.R. Metals, and he said that there was someone down south doing exactly the same thing and that they were just about ready to release the plans if they could figure out a way to do it without a liability exposure. So I quit working on my plans; why re-invent the wheel? I figured if they had done structural testing, it would save me from the expense. However, I have not heard anything being released yet. Ed: I do not know of anyone else working on a different spar. There was a couple down Texas way but they gave up.

If You Must (turn back): Steve Craigle (206.767.9434)
I have been studying the forces on and the velocities of an aircraft in a gliding turn with various bank angles. The object is to determine the optimum bank angle for a 180° turn with minimum altitude loss.
The known input factors to this problem are assumed to be the wing loading, aspect ratio, maximum available lift coefficient, the zero lift drag coefficient, and the air density. 
Ed: I have removed the in-depth math here - I can give you a copy of Steve's paper if you desire.
A plot of height lost versus bank angle for a particular aircraft configuration is attached. Due to the complex nature of the above relationships it is not straight forward to solve directly for the least height lost. But, by manipulating the spreadsheet, it can be shown that over a wide range of wing loading, aspect ratio and drag coefficient, the bank angle for minimum height lost always appears to be very close to 45°.

The reader should be cautioned that the decision to attempt a turn-back maneuver should never be based solely on the altitude loss factor presented here. Runway length, wind, local obstructions, and the exact position of the aircraft relative to the runway all play an equal or greater role in making this decision. The main factor presented here is that using a bank angle greater than 45° is a losing proposition, in fact, for a BD-4, a 35° bank angle adds only 7% to the altitude lost at 45° and results in a glide angle 14% less steep. 
Ed: I hope a few of you try this (at altitude, of course) and let us know what you think.

Wings with Dihedral: Noel Dunlap (406.257.1869)
I've often heard the comment that the BD-4 has no dihedral. While the person making that statement was looking at my airplane, he was usually not talking to me. I have to point out that there is dihedral in flight. Enclosed is a photo as proof. Although I don't have much time on this bird (382 hours), I try to fly about once a week summer and winter.
The Eagle One airfoil has been a satisfactory experiment. With the 150-hp engine and constant speed propeller, I cruise at 140 mph indicated with 23 squared. This seems to work out to about 153 mph true. With my dual vent fuel tanks (newsletter #18) I've had no fuel feed system problems. 1 removed the header tank vent from the left wing to directly under the bleeder valve and with a fuel gauge in the header tank am able to monitor how the selected system is doing. Again, since this least mod I've had a troublefree fuel system for at least 300 hours

Ed: I put this picture Into ClarisDraw and discovered that the dihedral exhibited here is about 1.4°. It would be fun to see what It is on other 13D-4s. How tight do your spars fit? Please take the pictures from directly behind the airplane to make my job easier.

Real Machine: Neale Eyler (316.941.7488, nevler@cessna.textron.com)
Still want to do the BD-4 staggerwing thing, but working on something simpler and easier to do to get up in the air quicker and cheaper. A little aluminum two seater Davis DA-2A is not quite as good a deal as a BD-4 in used prices, but operating costs will hopefully be lower. You gotta start somewhere.
                 ....Somewhat later sanity erupts!
 Well... now I am back. Scrapped the Davis to go to a real machine. The bi-wing BD. Expect a lot of engineering questions (I know you love to read these kinds of things). Greatly appreciate all the support and knowledge and wisdom you have shared. Hope all is going acceptably in your world. See you at OSHKOSH?

How do you (and your BD-4) tolerate altitude? (Steve Mahoney):
Steve Mahoney had a scary high altitude incident a couple of years and recently decided to 'fly' the Fairchild AFB altitude chamber. Roger,
Last Tuesday I took a class at Fairchild AFB on physiological training for pilots ... Very interesting. Most of the class was on high altitude flight but they also had a demo of night Vision that was quite good. This is the same class they run their flight B52 and KC135 flight Crews though and is taught by military personnel.
The fun part is a ride in the Altitude chamber to 25,000 ft. and then you are asked to remove your oxygen mask. I did pretty well, lasted for the full 5 minutes. My major symptoms are: I get real slow and my vision went to black and white, it happened so slowly I didn't even notice until I returned to 02. The guy next to me (an older glider pilot) lost it. He was so spaced out he couldn't even put on his mask and load his regulator when told to go back on 02. Two Airforce personnel came to his rescue.
After the class I borrowed Dad's old 02 system from my brother and took the BD to 18,000 ft. Here are the climb rates:

· 10,000 ft 100 mph 900 fpm
· 12,000 ft 100 mph 750 fpm
· 13,000 ft 100 mph 700 fpm
· 16,000 ft 100 mph 600 fpm
· 17,000 ft 100 mph 500 fpm
at 18,000 23,000 RPM 15"mp

The plane had 1 /2 tanks and was lightly loaded with just me and at the last minute, the dog wanted to come... so I let her ...at 18 kft. she seemed to mellow out a bit, I think she was a little hypoxic.
I suspect that the service ceiling would be around 20K. I think the electronic ignition (LightSpeed, Ed) helped a lot, as it was in full advance mode and allowed me to lean really well. Your auto engine with the blower should be pretty interesting to see what it can do. I figured that my Lyc was putting out only 85-90 hp at that altitude.
Ed: When you are thinking about 'beefing things up a bit', think about the performance shown above. You will never get there unless you are absolutely meticulous about WEIGHT. Steve's BD-4 has an 0-360 with a fixed pitch prop and is somewhere in the 1100 lb. range!

A `kiwi' BD-4 is launched: Russell Harris (russellh@xtra.co.nz)
On the 20th dec. 1996, 1130 hrs, my aircraft the BD4, ZK RDH flew for the first time from Kaikohe airfield Bay of Islands, New Zealand with Warwick Bleakley at the controls.
Another 20 year homebuilt project flies. This was after the usual taxiing trials and lift-offs to ensure everything was working as it should. With all the double checking of the systems I had done and in spite of a very detailed inspection by Mike Chubb and Mike Heaphy of Northland Aviation and of course the final definitive word of Rex Kenny of CAA, I still had ambivalent feelings running through my head "-----don't fly yet Warwrick---Yes! Lift off this time-----'. .A mixture of anxiety and elation that most readers are aware of at these times.
After a couple of circuits Warwrick taxied over and we crowded towards the plane anxious to see how she flew. She did look good in the air, fast and quiet and like a real aircraft , and the beaming smile on the test pilot's face was the best indication that everything was O.K. The designer's numbers all came up as far as airspeed, stalling speed and control authority was concerned and he said she was responsive and a delight to fly. That was certainly what I wanted to hear.
I had bought the partially completed kit from Trevor Ancell who had 8 years in the project but other parts of his life imposed restrictions which kept him from finishing. His work was of the very highest quality and I had to struggle to keep up that high standard. Anyway I have 60 hours on RDH now and enjoying every minute of it.
I am chasing up refinements to the fairings to be able to improve the cruising speed. So far I have wheel pants, brake covers, and nose a leg fairing. This gives me 120 kts. and I would like to get to 130 Ids. I know the last stages of speed improvement are difficult to achieve but by talking to other builder/owners I hope to get some help. I know you have done some work in this field with a curved windshield as an example and I have seen some photos of BD-4s with a type of louvre around the windscreen frame. I am curious as to the reason for this and it's advantage.
Maybe you have some other tips I can use. I have an 0320 H2AD Lycoming engine with a fixed pitch Sensenich 74 ADMG-60 prop.
This is a high time engine but seems to operate ok. I am interested in an auto conversion; particularly the V6 Ford you are using as it does seem popular and reliable. This isn't a common engine down here as most of our autos come from Japan as low mileage second hand vehicles, although I have a 266 cu. in. Rover VS in my workshop which I could develop into a useful engine. I would have to develop my own PSR unit as the cost of buying these from the USA is prohibitively expensive as our dollar is worth only half the US dollar.
I suppose my real question is, am I better of spending $10,000 on rebuilding and improving the 0320 by electronic ignition, an Ellison carburetor, improving the induction side or going with an auto conversion. Economy is an aim for me as gas is very expensive for us. Well, this is turning into quite a marathon letter but as I feel isolated down in the bottom right hand corner of the world I hope through the medium of the net and email I can tap into some of the developments you have already made and I can join in the flow of information.

Chevrolet 4.3 Liter: Sam Bien (313.942.1937, samblan1@juno.com) Hi Roger get your N.L, met you at Oshkosh. I'm using the Chevrolet. 4.3, home made PSRU ale Vanderhart, extended wings, and other modifications.
Have questions about weight and balance. Other guys are using the 4.3 with standard fuselage extension. Weight is very close to Ford 3.8 so I'm told. Wonder if it is worth the trouble to extend the fuselage, or just add weight aft.
Also what about folding wings, I don't live on a strip, and would like to bring it home. Need wing tips. I'm inserting steel in 4 motor mount attach points. Also am running an angle, back to front door post to strengthen the firewall area, and also angle over top of cabin spar to strengthen.
I'm using stock EFI with computer, with modifications per Swag Aero. Wondering whether to return fuel to header, or main tanks which will gravity feed the header?
Smoked Plexiglas gull wing doors. Lots of Plexiglas on top. Strengthening main gear with bolted-on 1/8" 4130 plate, and box with aluminum angle and plate of my design. I would like to talk to guys with experience in these areas.

3.8 Liter SuperCharged Ford Weight:
Rick Graf did a quick weight check on his SC project and Aero Kinetics PSRU. This weight does not include the radiator, liquids, or Intercooler (he decided to not use one). The all-up weight came to 525 lbs. with a CG of 17.75 inches from the prop flange. This system seems to be about 70 lbs. heavier than the standard V-6 firewall forward.

Spar Strength:
In order to settle the conjecture about the 'real' spar strength, someone with superb credentials has done an analysis on the new Super Tube spar system. The results are as follows:
Two computer analyses were done for a wingspan of 29 feet that determined very accurately the air loads (using the FAA approved Schrenk method of determining air loads) along every inch of the span for the bending and shear loads of the tube spar.
In one case a gross weight of 2500 pounds was analyzed for a 6 g ultimate load. For this first analysis it was assumed that a fuel of 42 gallons or 248 lbs. was carried in the wings. Under these conditions the maximum stress on the center section spar is at station 21 at the side of the fuselage. The tensile stress at this point was 46,128 psi and the critical buckling stress was a safe 63,560 psi. Therefore, it can be concluded that the center section is not critical. The maximum stress on the wing spar occurs just outboard of where the center section spar ends. This is at station 44 and produced a maximum tensile load of 62,396 psi. This is just a little too high of stress on this spar.
The second analysis was done at a maximum gross weight of 2,360 lbs. (same as above but with the fuel gone) with a 6 g ultimate load, but with no fuel in the wings. Under these conditions the maximum stress at station 21 for the center section was 46,566 psi (up a little due to less fuel weight in the wings) and the maximum tensile stress for the wing spar at station 44, is 61,067 psi.
It can be concluded from these analyses that in either case the center section spar is more than strong enough (obviously overweight also) but the extended wing spar reaches its critical stress levels, when the wings are carrying 42 gallons of fuel at a total gross weight of 2500 lbs. If no fuel is carried in the wings, the maximum grass weight is 2,360 lbs. The final conclusion is that by extending the wing you increase the stress level in the wing spar even with using a much long center section to where the gross weight is limited. It can also be concluded that the center section spar is over-strength under any of these conditions and is perfectly safe but unfortunately, extra heavy.

Rudder Sensitivity:
I recently got a letter from Don DeMarco asking about the rudder bellcrank dimensions. He feels the rudder is too sensitive.
This is a complaint that I have heard from a small percent of builders. Most of them have been trained to fly in airplanes that have very insensitive rudders and quite often they are not needed much even in turns. Our rudder is quite sensitive (which is similar to the sensitive elevator) and the best way to deal with that is to rest both feet on the pedals and then 'fight' one against the other when activating them.
The BD-4 is very much a 'rudder airplane' and I use only- rudder to control the airplane during cruise.
You could move holes in the bellcrank around - but do you want more pedal movement (move holes inward), or more 'resistance to pedal movement'to give you the feel you need. If you opt for more pedal movement, be careful that you can still get full rudder deflection. You could fit strong centering springs to better resist your foot pressure.

Flight Test (with true 'tail-dragger' landing): Tom Metty (313.231.1497, tmetty@umich.edu)
I finally started flying the BD last week and have made 4 flights so far with landings at 3 airports. My home base is only about 2000' of sod with poor approaches. The Lift Indicator works so well I haven't even looked at the airspeed indicator on final yet. If it's a short runway I use (an indication of) 15, a longer one gets 20. I'm appending the email I sent to my family and friends at the bottom of this message.
The real reason I'm writing you is a problem with hot starts and quitting after landing. I think I'm cooking the Ellison with the muffler. I have the stock BD-4 muffler on an 0-360 which places it only a couple inches from the Ellison. My first instinct is to add a heat shield between them. What did you do?
It's also painfully obvious from the CHT that I don't have enough cooling air inlet area and on the 4th flight I finally remembered to look at the oil temperature gauge ....right on the redline. More work to do.

First Flight

I was sitting in my office on Thursday morning and was thinking about Lloyd Dunlap who had flown his Lancair 320 for the first time the day before. It was a cool day, about 68 degrees with a light wind out of the Southwest. There was a high, thick overcast that provided a ton of visibility with no glare from the sun. It was 10 AM and the clock was ticking, what else could I do?
I made a few phone calls and left a few messages and headed for the airport. Unable to find Jerri, I left a note on the stove. John Wiltse (airport owner) showed up first and Beth arrived a few minutes later with munchies in hand. She loaded her camera and got ready for business. At about 12:20 we rolled it out. What a great day ....so far.
It started right up and we tried out our radios. I could hear the ground crew fine but they were unable to make out what I was saying. What the hell, what could I possibly need to ask them? I was about to find out. A couple of brisk runs down the runway to warm it up and it's Hammer Time! As I taxied into position I saw Jerri arrive, that's nice.
I used 2 notches of flaps and put my foot in it. Within 200' the tail was up and another few hundred and I was off. It was going uphill smartly and I was hanging on for dear life when John broke radio silence "your tailwheel fell off ". I pressed the mike button and said "kdoiw do lioe kkee". John responded "I can't understand a word you're saying". Great, just great!
Let me tell you about my flight plan. "Climb straight ahead at 110 indicated, level at 3000' and reduce power to 24/24, commence a 30 degree bank turn to the left and come around 180 degrees ....etc., etc. Anybody want to guess what happened to that "plan"? I don't remember anything about the first 5 minutes. I couldn't find anything and all the sights and sounds were wrong, I was passing through 3000' before I even found the altimeter, I didn't find the airspeed indicator far 10 minutes. I watched the cylinder head temperature gauge intently and when it hit 400 degrees, I leveled off (at 3000' it turned out). I started reducing power to get the temperature to stop rising, which it did. Then I noticed the airspeed readout on the GPS, 98 mph! Now what, and the engine seems to be slowing down. What kind of power setting did I set? ...Find the tachometer ...2200... what's the manifold pressure ....12"! Jeez there's another knob I'm supposed to be turning. I ran it up to 22", which brought the tech back up to 2700. I dialed it down to 2400 rpm and went back to wondering why the airspeed was so slow. Flaps were up, the gear doesn't retract, damn, I'm still climbing, lower the nose, now it says 155 mph. This thing is sneaky. The temperature dropped to below 350. Good.
After 10 minutes I was beginning to find more instruments and controls, the little airplane on the moving map display looked absolutely lost. It just kept wandering around like a confused ant. The neighbor went home and brought a scanner back which allowed the ground crew to finally understand me. "How much of the tailwheel fell off?" I asked, "All of it" was the response. By this time fellow BD-4 builder Don DeMarco had arrived and helped translate for me. It appeared the nut had fallen off that holds the fork on and the whole assembly had simply fallen off when the weight was lifted. At one point early on in the flight I had given some thought to landing right away but that would have been messy. I needed more time. After 20 minutes I began to feel like I was in control.
I was testing it's slow flight capabilities when I noticed I had wandered over Dexter at 5500', "I bet you can't see me anymore" I commented. I don't think they were watching. I was able to turn the plane until the dotted line on the Moving Map lined up with Cackleberry and head back. The Lift Indicator was working well, I tested it with flaps and no flaps. I was able to fly it down to "10" with full flaps so I picked "14" for approach. After 40 minutes I spiraled down at 170 mph and went out over Hamburg to start a long, straight-in approach. I don't remember what speed I was indicating, I was concentrating on the Lift Indicator. I was expecting to make several approaches until it felt right but the first one looked good so I went for it. The stud that was substituting for my tailwheel bore silent witness to the touchdown a mere 150' down the runway. There were no surprises as I slowed it to a stop about halfway down the runway. Beth was there to take the "One Small Step For Man" photo.

While we sat there in the middle of the runway waiting for the ground crew to bring the tailwheel, we reflected this must be what the Wright Brothers felt when they completed a flight and waited for the adoring crowds to catch up and surround them. We lifted the tail and plugged the wheel back on and Jerri hopped in for a ride back to the hanger.
I'm guessing I had put the tailwheel nut on temporarily 15 years ago because I didn't have a new seal to install. I found the seal in my parts bin along with enough spare parts to put the tailwheel back together. It's back on the plane and Saturday I hope to try it again WITH a tailwheel. The problem with communication may be simply the high level of cabin noise, I hadn't noticed it because I was wearing a Telex Active Noise Reduction headset. Next time I'll try talking louder or maybe try my David Clark ANR headset with a noise canceling electret mike.
There's more to do before I try any serious cross-country flying ...one step at a time.

Scott 3200 Steering Arms, etc.: Wally Kingston (joharowa@erols.com):
Question: On your Scott 30xx tailwheel, do you have the narrow steering arm or the wide steering arm like the Cessna 180/185?
I just upgraded to the wide steering arm on our Cessna 170. As I noted in one of the early newsletters (Dec 93, Funny Business, Pg. 6), the tailwheel does go to an extreme angle before it "breaks loose". I intend to install the longer pawl mentioned in the article as soon as I can.
BTW, the part numbers required to upgrade from the narrow steering arm to the wide steering arm, including the longer pawl, are: 

Ed: We use the narrow steering arm (I am quite sure) and the wide one would require a lot more 'throw' on the rudder bellcrank which Is not possible as the width of the rear fuselage is so narrow.

Exhaust Systems: Ken Blackburn (314.240.4548, kblackbu@mail.win.org)
Greetings from Boeing in St Louis (Mc Boeing as I call it). As you may remember I own N186JB constructed by John Bracher. I am thinking of getting a Pitts S-2A within the next year or so, and N186JB is working its way to the "for sale" status.
FYI, the exhaust on N186JB (mild steel crossover for 0-360) needed replacing, so I searched for a replacement. Paul Blades at Aero Specialty (209-668-0241) is building a replacement from my old exhaust. He builds exhaust and other metal aircraft parts, and will use stainless or mild steel, and will do custom work. He is making a jig based on my exhaust, so he could help out any other BD-4s out there needing exhausts.

A BD-4 Compared: Steve Mahoney (503.472.8668, mahoney@viclink.com)
A friend of mine recently purchased a Lancair which has a converted Lyc 0-290 G. This is the original model designed for the smaller engine. He gave me a ride in it ...and man compared to my BD-4 the pitch stability at the slower speeds was all over the place ...it scared me .. but my friend seems to have gotten accustomed to it's behavior and finds it a bit squirrelly, but acceptable. Nice visibility though and the cockpit was claustrophobic compared with the BD.
We then flew both aircraft side by side, throughout the flight envelope. I couldn't believe how closely matched the two aircraft where .... here is what I observed. My BD-4 with Lyc. 0-360, fixed pitch prop, 20 gallons fuel, one person on board, and his Lancair with Lyc 0-290 G, 15 gallons fuel, and one person.
The BD accelerates and gets off the runway in about 3/4 the distance of the Lancair. I could easily out climb the Lancair, I would guess that I had at least 200-300 fpm on him clear through 7,500. I could hold 1750 ft/min (it was a cold day).
The slow flight, to stall was similar ...we kept reducing our airspeeds to see who would fall out of the sky first 1 think the BD had a sight edge here, about 2-3 mph slower.
Level at 7,000 ft with the BD pulling 21" of manifold pressure, the Lancair had to do 22" to keep up. The rpms where perfectly matched.
With full throttle at 7,500 we where exactly the same speed. We flew next to each other for about 5 minutes and neither aircraft move ahead of the other. GPS showed 193 knots ground speed (tail wind that day).
I believe that at higher altitudes I would be faster than the Lancair and slower at lower altitudes. At higher altitudes my electronic ignition helps a lot. The higher parasitic drag (fixed gear and bigger cross section) of the BD would have less impact in the thinner air.
This test was a lot of fun to do... with the airplanes so closely matched I have a good bench mark in the future to compare new speed mods against. My only advice to you other BD flyers is: unless you have an engine like Ray Ward in your BD don't take on any Lancair 360x.
Addendum: The Lancair has an empty weight of 987 lbs., and the factory gross is 1600 lbs. In the above comparison, the Lancair was at about 1257 lbs. (44% useful load), and the BD-4 at about 1485 lbs. (28.5% useful load).

How is Your Balance?: Roger Mellema (253.631.5324, rmellema@halcyon.com)
I finally did it! For the last 3 years DSS (Dynamic Solution Systems) has been tempting me at Oshkosh with their beautifully simple (although pricey) balancing system. It is primarily advertised as a 'dynamic balancing' system for airplane engines but it is soon much more.
My initial interest came from wondering why the Ford V-6 was not as smooth as expected and needing a way to sort out the possible causes. Then came the gyrocopterl These things will really drive you nuts when you try to figure out what causes what vibration. They also naturally have a lot more shake than any BD-4 will every have.
Dynamic balancing of airplane prop/engine combinations has been done for many years. Engines are balanced to a good degree during design and sometimes during overhaul, and so are propellers. The problem usually develops when the two are bolted together and run at various rpms. Statically, each is properly balanced but when the dynamics enter into the picture, things are not always so good.
The dynamic balancing of prop/engine combinations is done by running the engine at rpms that are close to those used in flight, measuring the 'shake' of the engine with an accelerometer, and using a strobe and a computer to determine where the true center of mass of the driveline is located. There is no determination of which component is at fault. Weights are added to the spinner backplate or the flywheel to achieve balance.
Why is it necessary? I have already seen a couple of 'horror stories' where the shake of the system was around 'one inch per second'. In better terms, if this vibration were being measured at the standard 2100 rpm, the center of mass (crank & prop) would be offset from the center of rotation by about 0.01 inches. Vibration in this range is considered 'destructive'. A friend's seaplane had this amount of vibration and indeed, he had cracks everywhere after one trip to Oskosh.
My BD-4 with the 10-360 and Hartzell Constant Speed prop read close to 0.5 inches/second of shake. That would be not 'half as bad' as 1 inch/sec but more like 1/4 as bad because shake in inches/sec is not a linear function. A very acceptable shake is less than 0.1 inch/sec.
James Butler reported in the November 1999 issue of "Rotorcraft" magazine that the Navy achieved twice the mean flight hours between failure of nine selected systems when the average imbalance was reduced from 0.4 in/sec to 0.15 in/sec. Some of the 'selected systems' were the reduction gear box, the fuel tanks, and avionics.
Below is the polar chart of the balance progress for the seaplane I did recently.

Each circle is 0.1 in/sec. You can see that the final result is within 0.1 in/sec.
Sometimes the first 'trial' weight that is added to the system will cause the vibration to be worse than before. This is because the DSS system is still 'learning' about this particular engine. It will still rapidly converge on a solution. The algorithms present in the DSS eliminate a lot of guesswork.
As was mentioned before, the DSS system does a lot more than just balancing. A very useful feature is the frequency spectrum measurement shown below.
This spectrum is typical of a 4-cylinder Lycoming engine. Note that there are a lot more vibrations present than the single line for which we balanced (2100 rpm). Also note that my tachometer is off by over 100 rpm (another useful feature of the balancer).

This engine being a '4 stroke' causes the spectral line at about 1000 rpm. The pistons do a different thing every other time they reach top dead center. First they fire, the next time they merely push out exhaust gasses. This difference causes an imbalance that produces a spectral line.
The second harmonic of the crank rotation (4400 rpm) is the 'firing harmonic'. Two cylinders fire for each rotation of the crank. This harmonic is quite large due to the large power pulses. This harmonic would be bigger still if the accelerometer were mounted with its sensitive axis in the same direction as the piston movement.

The 6 cylinder engines exhibit quite a different spectrum. 2100 rpm is used here again and '1/2 rpm' line is present at about 1000 rpm. In this engine there are 3 power pulses per crank rpm. The spectral line at 6400 is the 'firing order' harmonic.
There are some higher order harmonics on both charts that are mostly harmonics of the lower main spectral lines. It is possible to search though them and find the 'shake' of some of the accessories such as the alternator.
The DSS system also allows the characterization of any object. The resonant frequency can be found by setting the DSS to 'trigger' and then rapping the object with a hammer. This can be useful for finding objects (engine mount, alternator mount, etc.) that are resonant to some of the engine harmonics shown above. When this is discovered, it may be necessary to 'retune' the object so that it does not vibrate and fatigue.

This figure shows the BD-4 cabin vibration at different power / rpm settings. '1x' is the crank rpm and the other harmonics are shown as multiples of that rpm. This chart shows that 2400 rpm is a good, low vibration, point to use for long duration cruise.