BD-4 NEWSLETTER #22, Nov. 1994
Roger D. Mellema
17605 SE 288 PI.
Kent, WA 98042
PH 206-631-5324

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

Well, another Oshkosh has come and gone. I did get there but not with the V-6. Boeing and family took their toll and my new cowling wasn't quite done yet so I flew commercial to Chicago, rented a car and drove the rest of the way. It was a real shame too as there were very few EAA'ers showing off auto powered airplanes.

Ray Ward was there with his Chevy powered BD-4 as usual. The airplane looked good and Ray did get a chance to fly but other traffic in the pattern really hindered him from showing just what the airplane could do.

There was a Stits Playboy al Oshkosh that has flown with several different auto engines. It currently had an aluminum 215 ci Oldsmobile/Buick V-8. It was not perfectly done but he had a great time talking about it.

Davey Blanton had his Sport Racer there but I never did get to talk to him.

Rudder Trouble:
There was a BD-4 at Oshkosh this year that had a problem with the rudder. They had taken the airplane up to give someone a ride and later the pilot said that it seemed as if he had no right rudder. When checking it by pushing on the pedals with my hand (and someone simulating wind force on the rudder) everything seemed fine. After a few moments of thought, I tried the rudders again but this time I got in the airplane and put moderate pressure against both pedals and then tried to push in right rudder. There was almost none! The problem was fixed by opening the rear of the airplane and tightening up the turn buckles about 12 turns each.

Ailerons:
A couple of us BD builders recently were given a partially built, one-of-a-kind experimental twin engine aircraft. The designer is an 82 year old ex-Boeing engineer. I noticed that the ailerons were built so that the counter balance was distributed along the lower front in a bit of a crude way. This was done on purpose so that the angle that the counter balance weights were attached to would rotate down into the slipstream as soon as the aileron was rotated up. This greatly increases the drag of the "up" aileron so that adverse yaw would be eliminated (or rather swamped out with drag on the "down wing" side). The designer said that this method will pretty much eliminate the need for rudder when turning the airplane.



The drawing above show approximately how the angle and the counter weights are mounted on the aileron. The one difficult part of doing this is to avoid "aileron snatch". When the aileron is rotated up the force of the air hitting the "angle" times the moment arm (length to the center of the torque tube) must not overcome the force of the air hitting the top of the aileron. These forces can be balanced so that the ailerons would have a "lighter" feel.

After thinking about this awhile, I realized that all the work I did on making the aileron counter balance low drag was exactly the wrong thing to do. The counter balance should be Junky and square so that it produces a lot of drag. Now my problem is how to figure out the proper shape for the lead without cutting large (and wrong) holes in my wing tip.

I have been concerned about adverse yaw effects as a result of using a "Wing leveler" S-TEC autopilot. One option was to get a little rudder movement (bungee cord?) when the ailerons are moved. I now think that there might be a better way.

BD-8:
M. Lee Wachs (Talmage, CA) contacted me recently with questions about the BD-8. There was one present at Oshkosh this year and it looked quite interesting. For those of you who are new to the Bede family, the -8 is a single seat, 200 hp. all-out aerobatic airplane designed to out-perform the Pitts Special.

The BD-8 is built in the same manner as the BD-4 in that it uses all angle aluminum for the fuselage and also the tubular spar for the wing. Mr. Wachs sent me a copy of the plans but they are in such horrible shape that I have taken it upon myself to redraw them on the computer. I have most of the hardest sheets drawn now and am working slowly on the rest.

I would like to build one but there are a lot of projects ahead of me yet!!

BD-12 and BD-14:
Jim Bede must be making some money on the BD-10s as he has taken it upon himself to get started on new designs that "the rest of us" can afford. The word after Oshkosh is that there was a great interest in the new designs and that the company is working full speed on getting the proto-types flying. These airplanes are 2 and 4 place, look just like a larger BD-5, and are made out of carbon fiber laid up in female molds (later to be Reaction Injection Molding). The projected weights are very light and the cabins look very spacious.

I must admit that the prices for the complete kits (including engines) are quite appealing. Contact the Bede Jet Corporation for information packets.

Picture Window Doors:
Larry Fattaleh sent pictures of his beautiful BD to show me his new pointed cowling (shades of Scott DeGaynor) but what I really noticed were the all-Plexiglas doors. It really looks like a good way to go. I think it actually makes the airplane look better.

Larry also confessed to: "While at full power climb-out to stall and snap inverted, fall through a cloud and recovered from the inverted spin at about 600 feet." He is aerobatic trained but "doesn't remember being instrumental in that recovery."

Propeller Efficiency:
I now have quite a bit of time on my Warp Drive propeller. Allan Watkiss reported on his use of a Warp prop on page 21-7 of the last newsletter. He was happy with it but bound that it reduced his cruise performance some. 1 have found that the Warp Drive (3 blade carbon, no taper, 70", ground adjustable) is much superior to the wood prop that I first used. The blades on this prop are much thinner than a wood prop and even a bit thinner than an aluminum prop. This means you should get better efficiency.

I noticed that the wood prop seems to have low thrust in static conditions (full power run-up, taxiing, start of takeoff roll). It did a fine job above 100 mph and in cruise and is the most "almost constant-speed" fixed pitch prop I have ever flown. The full power rpm static on the ground or flat and level at any attitude varied less than 200 rpm. It was almost like flying a constant speed. The engine would never rev past red-line.

Alan said that he used a 14° setting (at the tip) on his Lycoming O-320. I find that an 18° setting is good for climb performance and 20° or 21° is great for cross-country work.

The following chart shows the increase in efficiency with the Warp Drive Prop. It is easy to see that the cruise performance is always better and when the Warp is set for cruise them is a 6 mph speed increase.

I tried a 3 bladed wood prop and found H even worse than my 2 bladed prop (same manufacturer). The 3 blade wood turned up 2600 rpm static (4460 rpm engine), It was amazingly low in thrust in taxi conditions. It performed well at higher speeds but did not equal the Warp Drive prop.



Spar Challenge (by Joseph Alt):
..... There is one area crying but to addressed yet and that is the design has been held hostage to a round pipe that is used for the wing spar. That round pipe is totally out of keeping with the rest of the aluminum angle format design. A spar built out of aluminum angles connected to a web of certain easily calculated thickness must surely have been run through several hundred calculations and computers over the years. Yet here we are still captive by that damn stupid spar pipe!! The design deserves better than this ..........

Attaching a built-up spar made from plates and angles to the fuselage would be easier and more secure than a slippery round pipe would. The built-up spar center section might more profitably be a roadable width of 7.5 feet. Yet leaving roadable width for the attachment fittings ......

editor note: Is there anyone working on an alternate spar?

New Cowling:
I have finished making a cowling mold for the V-6. Anyone who saw my 'Rest" cowling at Oshkosh last year knows why I had to do something! The engine now runs a little hot but I have increased by speed by 7 mph with power settings from 181o 26 inches of manifold pressure.

Retro-fit Ignition Systems:
Steve Mahoney recently installed a "Light Speed Engineering" electronic ignition on his Lycoming O-360. When he was here for the Memorial Day BD-4 fly-in he still had a few bugs in it - primarily the massive ignition noise it generates. It was very impressive anyway in how it smoothed out and allowed a low idle.

By Oshkosh, Steve had the ignition noise solved with shielding and the new system probably helped him when he raced against Scott DeGaynor. It was really tun to watch as they both started up their engines (an O-360 and an O-320). It was quite obvious who had the better ignition system. We did find out that a blueprinted O-320 with a constant speed prop is very good competition for an O-360 with a fixed pitch prop.

Ford Ignition Systems:
I had a partial failure of my ignition system recently due to a broken-off but still touching wire. I had used a lot of RTV sealant to stress relieve the wires but one of them broke off anyway. There must be a lot of wind blowing things around under the cowling.

I decided that it would be a good idea to go to two coils - especially since MSD Ignition has a "coil switcher". This $60 item uses diode stacks to allow two coils to be tied to the single feed to the center of the distributor. The following schematic shows how the system is now wired. Note that the "hot start" (12 volts) is only available on the #1 Ford CDI ignition box. This was necessary to keep from powering the "inactive" ignition box through the 1.3 ohm dropping resistors. It is rare to need the "hot start" feature anyway.



The only single mode failure item that concerns me now is the "pickup" coil in the distributor that takes the place of the points. In talking to shops that repair a lot of Ford products, I discovered that they do replace a lot of these little coils. The failure mode however, is broken off leads due to the vacuum advance movement of the coil mounting plate (we do not have vacuum advance). A check of the leads to the coil shows that they are very secure but it wouldn't hurt to use some RTV sealant to make sure they can't vibrate. I am planning to install a second distributor coil as shown above to get rid of that single point failure hem. I think an MSD crank ignition trigger could also be used to fire the Ford CDI ignition boxes. The magnetic trigger can be bolted into the crank pulley, the pickup sensor must be adjustable for timing and is mounted next to the pulley.

You will notice that large 4 pole 2 throw switch is not needed anymore. A simple 1 pole 2 throw will suffice. I am still using most of my switch as I still haven't put in the other pickup coil or the crank trigger and I don't think it would be a good idea to hook up pins 3 and 4 of both CDls to the single: pickup coil (it may not even work).

Fuel Gauge Calibration (by Ray Ward):
Since our life could depend on knowing how much fuel we have on board, we need to do anything we can to help ourselves know this. This is particularly true in a BD-4 with long, flat fuel tanks. Ordinary fuel gauges are not accurate, but calibration of them will increase their usefulness. It is a good idea at some time to see how long the engine will run after the fuel gauge needle hits "E". My BD-4 runs 30 minutes after that. If you try this -do it at a high altitude so ample time is available to re-Start the windmilling engine.

The most accurate fuel gauge is a dip stick. I made one from a paint-stir stick (1/8" by 12"). I calibrated the stick starting with an empty tank. Each increment of gallons is marked on one side of the stick, and the opposite side is marked with the corresponding fuel gauge readings. If you do this, you will also determine the usable fuel. You will be disappointed to learn lust how much fuel is not usable. I tipped my plane up on the nose and siphoned the fuel out through the filler cap. Then I drained the gascolator. I had to pour in 5 gallons of fuel, and added a little air pressure in the tank with my big mouth to restart fuel flow. I caught and measured the fuel that came out to determine the remaining unusable fuel while the plane was level and the wing tip was propped up to simulate the flight load angle of the BD-4 fuel tank. Two gallons are unusable in each wing tank.

At this point, I put the tail back down to get readings as you would on the ground. I continued to add fuel and observe the fuel guage. The needle comes off the peg and reads "E" at 8 gallons (6 gal. usable). At this level, fuel is just now beginning to be seen coming under the spar, and will show about 1/4" up on the dip stick. At 10 gallons (8 Gal. usable) the needle reads 1/4 tank. Too bad we can't get accurate readings closer to zero but by knowing the fuel flow, we can know pretty accurately the fuel quantity remaining by noting the exact time the needle shows "E". At 1/4 tank, the guage reads the same - tail down or level flight.

My fuel selector is plumbed, "Left, Right, Both", and I recommend "Both" always for take-off. Some of the "unusable" fuel can be used in the BD-4 if we empty one tank with the rudder ball off center, slinging the fuel inboard until it is exhausted before switching tanks. Remember - it will take some time to restart the engine after centering the rudder and switching tanks.

Always use the dip stick with the bottom against the spar at the same angle. I calibrated my dip stick up to 20 gallons and always keep it in my plane.    rw

Wing angle of incidence tool (by: Jim Huber):
The tool shown below will help you get the correct angle of incidence set on your wings. Set a level on the top or bottom of the straight edge. Be sure to check the wings every two feet along their length - your wing may have some twist in it and you want to get the average angle of incidence over the entire wing. Be careful of a wing that has "wash in" (a larger angle of attack at the tip than at the root). This wing will stall at the tip quicker than at the root which will cause you to lose aileron effectiveness. The BD-4 normally stalls the cabin well before the wing and there is sufficient warning to avoid wing stall.


If the distance between points A and B is 40.1 inches, the incidence angle is 3°.

The fuselage must be leveled before setting the incidence of the wing (lay a level on the area under the doors).

Use 0.065" thick aluminum or other suitable material for the "tools". Bond two pieces together so that the tool registers properly on a straight edge. Use a "C" clamp to hold the tools to the straight edge or bolt the assembly together.

Open Letter from a Frustrated Builder (by Tim McGinnis):
It seems I haven't made much forward progress on #480 in the past 6 months. since you were here to pick up the "SuperCoupe" engines last summer I've invested about 500 hours in redesign and rebuilding of various previously completed items. The exasperation which perfectionism breed can become overwhelming! I'm wondering if I'll ever get this thing in the air.

When the project was begun 2 years ago my building buddy, Charles (an A&P mechanic), tried to keep me on the path-of-least-resistance to an early completion. Our original goal of 1,800 hours and 12 months to finish the project seemed reasonable. But after the first year the hours were there but no 'flyable' airplane in sight, thanks to my insatiable desire to MODIFY.

After he moved out of state last and left me to my own devices, paralysis-by-analysis set in and it seems I've been mired down in detail ever since. Oh sure, I may have the smoothest, straightest, most "nearly perfect" set of Dixie-cup wings you've ever laid eyes on. Perhaps even the only '4 with ailerons that actually do achieve the proper deflection ratio (17:25, down:up). Not to mention a true 4 place cabin with a fifth "jump seat"? A 240-? hp SUPERCHARGED fuel injected, multi-coil distributorless, water cooled wonder of modern technology engine. Or more safety related mods than you could shake a control-stick at! In my estimation these are all worthwhile attributes and may even result in a "flyable" airplane some day.

However, I've been to Oshkosh and seen wings so twisted and rough you'd swear it couldn't fly, yet it makes the trip every year! I've talked to '4 pilots about their aileron deflection ratio of 1:1 (what you really end up with if built to plans) who have exclaimed with utter astonishment "so that's why I've got so much adverse yaw during steep turns". And still, I know these guys are out there enjoying the fruits of their labor, flying around and just having a blast while I continue to "nit-pick" the detail with large amounts of blood and sweat and tears and HOURS.

As you know my goal isn't the "cosmetic perfection" of those heavy metal "body-putty favorites" which impersonate composites and walk away with "best" trophies. I want to build it as light as 1 can without sacrificing comfort, safety, speed and the best handling qualities possible. Straight lines and a smooth surface are a "must" but without trying to hide all the rivets and seems that are a natural part of any metal airplane. Its just that you and the other "ancestral" BD-4 builders have come with so many worthwhile mods that including several of them seems like a never ending task (I know what you're thinking, but I really haven't tried to include them all).

At last count I was nearing the 3,000 hour mark now 2 years into this project and really not a lot closer to completion than when Charles left a year ago. If I sound frustrated, I am. That's the price all perfectionists pay for their affliction. But if you think I'm ready to give up, you're wrong. I'll complete i1 it it takes an additional 3,000 hours. I just wish I had saved all the parts I trashed. I could have built two and sold the one to pay for the other!

"Misery loves company" and I'm sure there are others out there who would take a small amount of comfort in the knowledge that they are not alone in their "twilight zone/endless loop" of building dissatisfaction-rebuilding, ad infinitum. So if you want to publish this for their benefit or just for a chuckle from those who have already waded through it and are now flying their "dream machine" be my guest. I'll probably be ridiculed by the "just build if per plans" purists out there, but that's OK. Ridicule fails to pierce the thick skin of someone who knows he is right! Conceited you say? I hope that's not the impression I leave. Sure of myself? You bet! As is anyone who intends to build a vehicle to pierce the unforgiving environment that air has to offer!

I'd like to take this opportunity to thank you for your undying devotion to the BD--4 movement through your newsletter and my (too) many phone calls. Without which #480 wouldn't have a prayer of completion, not to mention the pinnacle of BD-4 evolution I intend d to be! I still hope to have it flyable for the big 25th anniversary bash at Oshkosh '93.

Of course that largely depends on how quickly I can tie up a lot of loose ends and get on with the next major step... engine development. Although I spearheaded the purchase of these V6 wonder engines I'm counting on you and your "engineer" friend to spearhead development. And, although it will mean a fair chunk of time away from my project, I still am intending to edit an alternative engine newsletter. I wish David would have followed through with his, or that some else would have taken the ball and ran with it (for months we both agreed someone needed to), but he didn't and nobody else has. So it seems I'm elected. I've never built an airplane or edited a newsletter before $o I intend to do them both the same way. Relying heavily on ideas and input of others more experienced, and just keep tinkering until I get it right. I hope to have a "trial issue" ready for circulation before the end of May this year.

I too was stung by the last guy to offer an automotive newsletter, for $18.00, and never received an issue. Which understandably left me, and probably many others, without a "warm-fuzzy-feeling" toward that person. Therefore I won't be asking for any up-front money from subscribers. Instead I'll send anyone interested a trial issue. If they think it has potential value to them and wish to subscribe then we'll talk money. Until the first issue is finished and actual costs pinned down I can only estimate an approximate annual price of $15.00. My intention is for a more or less quarterly publication depending on interest and input, new developments, etc. Should any of your readers want a free issue, have them send their request to;

T. L. "Doc" McGinnis

editors note: Tim is now writing an excellent newsletter aimed at the supercharged Ford engine. He is also the author of an excellent BD-4 article in a recent issue of Kitplanes magazine.

For Sale Items:
Coronary trauma at 61. I'm selling my'79 tailwheel BD-4. Only 390 hours on both O-360 Lyc. 180 HP and airframe. Scott tailwheel, BD pants and gages. Full panel, two Nav Corns, glide slope, Hobbs, Name 50 transponder, mode C, gyros, always hangared, white Imron with blue trim, exterior 9, interior 7, aluminum header tanks behind front seats, 4 point aerobatic harnesses, anchors, Murphy wing kit and tooling (in boxes), wing folding kit (in box), 70 gal. fuel, strobe, heated pilot, quick drain, nav & landing lights, Hartzell C.S. recent $600 AD, cruise honest 180+ mph, land/takeoff 600', battery door, flame proof upholstery, intercom. Thousands of $ and years of sweat and TLC invested. Offers. Video. Paul F. Wood (402) 486-3339.

BD-4 for sale. Spars and pre-bent parts, big tail, SN 696, started with 1 wing together, fuselage sides together, ribs on the stabilator. Kits 1 through 5 (approximately). Ed Fisher (513-464-5294)

Excess BD-4 Components: (prices based on 1977 B & D Products price list)

1 2 3 2 1 2 2 1 1

Mahogany wood trim wheel Main landing gear struts Lord landing gear rubber mounts Master brake cylinders with flexible hose Nose/tail wheel assembly $235.00 Main landing gear axles with nuts Door latches (H7215J) with hardware Primer Xerox copy of Build Your Own Airplane

$18.00 $100.00 $75.00 $120.00 $235.00 $75.00 $24.00 $25.00 $20.00

John Steere,(317)342-2417

For Sale: BD-4 exhaust system with stacks and shrouds for Lycoming O-360-A1 A, (used, new can, pressure tested), $325.00 or offer (shipping included). For Sale: Hartzell Prop HC2YK-1 BF with logs, has damaged blades, was shipped with 180 hp Lyc engines with BD-4 kits. $425.00 or offer (shipping included). Reg Lukasik, Alberta, Canada, 403-459-0813

For Sale or Trade: BD-4, N14WT. TTEA is 340 hours, 10 32081A Lycoming. Tricycle gear, digital radios, strobe lights, landing lights, GPS. $25,000 or offer. Skip Hellen, 15330 Cabell Ave Bellflower, CA 90706 310-866-1923

Philip Pisczak is interested in building a BD and offers his services to draft up, at no charge, any plans for variations on the BD-4 theme. He works in AutoCad from a 3D computer model and can produce color originals and for a small fee full size copies. 216-338-1712.

William Justusson, (c/o Saudi Aramco, Box 1284, Abqaiq 31311, Saudi Arabia) is interested in buying a copy of "How to Build Your Own Airplane".

Robert Mascharka (3915 Floramar Terrace, New Port Richey, FL 34652 PH: 813-849-3710) would like to by a "How to Build Your Own Airplane".

Fuel/Air Separator (by Tom Metty):
I am installing a fuel pump in each wing root to push fuel through a 2 quart air separator tank also located in the wing root. The fuel pickup point is at the level-flight low point in the tank. The separator canister has a fixed orifice at the top plumbed back to the fuel tank adjacent to the pickup. The back pressure in the fuel system should force a small circulation from the top of the canister to a point below the fuel level. Sizing the orifice to bubble air off the fuel while maintaining enough fuel pressure is the trick. With the electric pump off, air may start to accumulate due to sloshing. Each separator has 2 magnetic float switches (similar to Wicks FWS-1) to sense the amount of air. Since there will be dual systems operating, switching tanks will select a totally independent, pre-pressurized fuel system.

Ergonomics of a Seat (by T. L. (Doc) McGinnis):
The Problem
I suppose the Pinnacle of light, cheap aircraft seating is the BD-4's rear canvas/tube sling seat. The new Murphy Maverick even uses one as the front seat and claims it's "comfortable"! I challenge those of you who view weight reduction with singular awe, to shed your BD front bench (about 12-15 lbs. depending on upholstery) in favor of that! It may be OK, even necessary, for under-powered short duration ultralights. But I tend to view the '4 in a different perspective, and my personal comfort as a very important aspect of flight. Oh sure, you could sit on a foam covered tin can (pretty good description of a BD bench don't you think?) and still enjoy a romp around the patch a time or two before TB (tired butt) attacks. For sure you're a lot better off than those poor souls in that rear sling!

Fatigue promotes distraction and loss of concentration, a deadly duo in air travel. In an auto you just pull in somewhere and stretch. Not so easy for us pilots. We're faced with the most demanding aspect of flight during the time we're the most fatigued. You can bet that when the pressure/pain receptors in your butt and back start screaming at your brain, your concentration will suffer. This may not even be evident on a conscious level. But then a good portion of flying (as in driving) takes place on a sub-conscious level, i.e. automatic responses, second-nature type of reactions, etc.

Physiology of the "Squirm Response"
It's at this subconscious level that the brain gathers and processes signals from its millions of proprioceptors (pressure, pain, temperature, etc. sensors) and then relays appropriate reactions to the muscles/blood vessels to change and improve the situation. I've coined the term "squirm response" to cover and simplify this vastly complex mechanism. Like gravity, its a force that can't be resisted. You will "squirm" for relief wherever and whenever the pain threshold is breached. If movement is sufficiently restricted, thereby preventing relief, the signals will grow to the point of distraction, first on a subconscious then a conscious level. Which means if your back/butt is "barking" at you, the distraction has already escalated from moderate to severe.
No wonder, given all the "unavoidable" distractions, it is so hard to make a perfect "squeaker" at the end of a long or demanding flight. Airlines know this. The best seats in the plane are usually found in the cockpit, not coach (problem is they won't sell you seats in that area!). Even long-haul truck drivers know this. Their eighteen wheeled "severe turbulence simulators" are usually equipped with fully articulating air suspension seats costing several hundreds of dollars each. Ask any of them and they'll tell ya their butt is worth ii! As pilots shouldn't ours be? There's just as much riding on it (pun intended)!

At What Price Comfort?
Physiologically speaking the best solution is to build all airplane cabins high enough to stand up, stretch out and walk around a couple minutes every hour or two of flight. Of course drag-wise that's a ridiculous suggestion!

Naturally if you're only into weekend joy rides of an hour or so duration this is a non-issue and doesn't warrant further concern. However, if like myself you see your '4 in the same class as any high-speed cross-country airplane capable of extended duration flights and ever intend to make one in "comfort" then read on.

The physical universe has within it certain immutable laws, I think one of which says "the more you fiddle' with an original design the more its going to weigh and the less its going to look or fly like the original" or something to that effect! J.B. designed the '4 to have an empty weight of under 900 lbs. and powered by a 160 hp engine. Its obvious to me that the "one hour bench" was designed for just such an airplane. But be honest now, how many BD-4's actually fit that description? Me thinks not one, Horatio! So why is it then that almost all are overbuilt some 300 lbs and overpowered by an extra 20 - 40 hp, but still built too light (Ugh! that's almost blasphemy) with respect to the one area most important to comfort?

Want to ask someone who has been on a long, I mean a really long, cross-country flight how bad it can be without comfortable seating? Talk to Dick or Joanna.

Possible Solutions
Since you are still with me I can assume you agree something better is required. So let me share with you what I've learned from many hours and a couple hundred or more dollars invested during the past year while I wrestled with the problem.

Notes Before Proceeding: Prices are as quoted to me from salvage yards in my neck of the woods and may vary elsewhere. Weights are personally taken with a spring type hanging scale and, although not extremely accurate, offer good comparative weights. The track and mounting hardware weights are not included but will add from 5 to 10 lbs per pair. The pre-fatigue flight times are a personal "guesstimate" based on my own limited flight experiences along with 15 years in the field of spinal health care. Obviously, different sized and shaped people will experience fatigue in different anatomical areas and at different time thresholds. Naturally then the best seats will be those that either articulate the most or are custom shaped to fill your particular body type.

A Certificated Approach
Just about any production airplane in its class offers seating far more comfortable "one hour bench". With an average frame width of only 16" and very little upholstery overhang, most can be made to fit. However weight variation can be considered a factor in selection , especially in lower powered aircraft. As with anything "Certificated" the largest factor by far is the price.

The plain non-articulating type (Beech Skipper is a nice high-backed example) will weigh about 20 lbs per pair and cost around $225. With its better back support and fewer pressure points as compared to the "bench" it should be good for a two hour flight.

Moving up to an articulating seat will cost more in both respects. The Cessna 152 Aerobat seats offer the best compromise between comfort-cost-weight of any aircraft type I've come across. It offers two back positions, either straight up or slightly reclined (3 or 5 degrees). A pair will weigh about 30 lbs and cost around $400. Although the recline is a big plus, they aren't high backed, which means no rest for the upper shoulders or neck on those really long flights. Therefore I estimate a "pre- flight time of 2 to 3 hours.

Add another $100 plus 4 or 5 lbs and you can get a pair of fully articulating, high backed, seats which should improve "human range" even more.

Automotive Alternative?
Almost any late model auto bucket seat is far more comfortable than even the best light single aircraft seat I've seen. Not to mention far less expensive than even the cheapest aircraft seat. They have internal spring wires to support and absorb shock without causing pressure points. Most have infinite recline positions from straight up to almost flat. We all know what the big problem is though... weight and width. Right?

Well I went to some auto salvage yards to investigate. I expected to find the subcompact seats a lot smaller than their full sized counterparts. Boy was I wrong. Regardless of country of origin or size of vehicle, auto bucket seats were pretty much standardized to a frame width of 21 to 22 inches. Add to that an overhang of from 2 to 5 inches each seat and hey, they just won't squeeze between the doors of a BD-4. Then consider the extra 20 to 30 lbs per pair weight penalty over and above the aircraft variety and that pretty well finishes the auto story. That is with 3 notable exceptions.

A couple of exceptions were Toyota and Pontiac Hero. With a frame width (including seat back adjuster of 19.5" and only minor overhang, they will fit most BD-4's. Weight penalty (approximately 10 to 15 lbs over aircraft types) may still limit use except in the higher horsepower planes.

My project however is restricted from their use due to a three inch wide center console extending aft between the seats. But I didn't give up there in my search for the best seating possible.

Yes, I saved the best for last. The narrowest and lightest auto seat in existence and you heard it here first! This auto seat's frame measures only 18.5" (adjuster included) has negligible overhang and better yet, weighs no more than the fully articulating airplane types. At 35 lbs per pair they're only 5 lbs over the "mid-range" Aerobat seats. That weight does exclude the heavy headrests which can easily be replaced with lighter ones or left off altogether.

How so light compared to all the others? I found out the hard way. I tore one apart and for several hours ground off and drilled out any excess steel I could find. But with thin-wall steel tube construction most of the time was spent "looking" for excess. By eliminating the heavy (1/41b) seatback return spring and grinding off another quarter pound from the mechanism, along with drilling (too) many 1/2" holes in the seat bottom side panels the weight savings wasn't worth all the time and effort. It was well worth wasting a seat to know for certain that all excess had already been engineered out by the factory.

Get this, the price was only $100 for a pair. By far the best news for me was that by swapping sides (to position both back mechanisms aft of the center console) they fit perfectly! Add an air-adjustable lumbar support and I believe flight duration will be limited only by my brain rather than my butt! Oh, by the way these seats are found in Suzuki Samurai vehicles.