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Famed Aircraft Designer James Bede Dies
linuxwrangler writes with a bit of news overlooked from last week, but worth noting: Prolific aircraft designer James "Jim" Bede has died at age 82. Although Bede designed numerous aircraft he is most commonly associated with the BD-5J, the "world's smallest jet", that was famously used to help James Bond escape in the movie "Octopussy." Bede's company currently has that aircraft for sale.
When I was a kid I dreamed of building and owning a BD-5... Now that I read that of the first 10 BD-5's built 5 resulted in fatal crashes (50% is pretty steep ratio). Sometimes you have to thank God for unfulfilled dreams.
I've always been fascinated with Jim Bede's designs and his "get shit done" attitude. Personally, my favorite was the BD-10, a supersonic jet for folks on a high end cessna budget.
https://en.wikipedia.org/wiki/...
However, he is also somewhat infamous in the industry for how many of his creations have crashed and resulted int he deaths of their owners. Spark of brilliance with a bit too little attention being paid to safety and reliability.
Speaking of aircraft, right now the San Bernadino Fire Dept is saying that fire-fighting aircraft are being grounded because of all the private drone activity in the area around the wildfire.
http://ktla.com/2015/07/17/15-...
You are welcome on my lawn.
Ashamed of the submitter/editors for messing up this opportunity and letting us all down. The correct title of this story is that the venerable aircraft designer James Bede has died.
The World Wide Web is dying. Soon, we shall have only the Internet.
Aerodynamically and structurally the BD-5 is fine (Burt Rutan was involved) but there are four issues that affect the stats for this plane (disclosure: I own one) but are not generally pointed out in these conversations:
1. The engine was never really solved. Jim started selling the kits with a scheme where people bought them in portions; a builder would buy as much as he could afford, build that much, then go back to buy the next portion, and so-on. By the time they got them fully built except for the engine, Jim did not have an ideal production solution (not an uncommon situation with a certain subset of "visionary" entrepreneurs). A bunch of builders adopted engines from small cars, snow mobiles and such things to their planes out of desperation to get their expensive toys finished and flying. These "solutions" were each custom, unique, and outside of the experience and influence of the airframe's designers. The BD-5 is not particularly spacious in the engine compartment, so these were always sub-optimal solutions.
2. These were home-built kit planes. While some such planes (like Rutan's canard-based designs) are very forgiving and aimed at first-time builders, the BD-5 is a bit of a sports car (both less-forgiving and attracting the sort of builder/flier who is more of a risk-taker and speed junkie).
3. There was a design change in the wing partway through the process that I think was not implemented by all kit-builders. Can't recall at the moment if it was an airfoil change or a wing washout (a slight twist from root to tip for you non-aero types) change, but it affected the flight envelope. Any BD-5 that did not implement the change would have different flight characteristics and almost certainly a different subset of stats.
4. There is a bit of a Corvair syndrome here: The Corvair, particularly the later sleeker-looking models, was a neat little car with rear engine that performed quite nicely and was quieter and cooler in the cabin thanks to that rear-engine. The very things that made the Corvair nice also meant that it handled differently because it was not nose-heavy like most cars. You do not want to put an inexperienced driver in a Corvair on ice. A very famous lawyer made quite a reputation for himself trashing the Corvair in the eyes of the general public even though the vast majority of those cars were driven safely for the full life of the product. The simple fact is that if you design a product that behaves differently from what the average Joe expects, the average Joe who is not paying sufficient attention will be more likely to get into trouble. The result is that the general public has a very-different impression from that of the owners with firsthand experience. The question for our society is this: Do we homogenize everything to the lowest-common-denominator and make everything bland and safe for the idiots, or do we still say that individuals are both free, and responsible, to make their own decisions and risk assessments?
Incidentally, this is all hardly unique. Rockwell used to make a beautiful high-wing twin called a Shrike Aero Commander. They had Bob Hoover fly around the country doing some of the most-amazing dead-stick aerobatics ever in the thing. The Shrike also had a less-than-stellar safety record (wing spar cracks issue). Properly maintained, inspected, and flown, the Shrike was a really neat plane. In the hands of a lesser-owner it could be a death trap. Welcome to the world of human-designed, human-built, and human-operated systems.
The BD-5 will always be there, even when the last one is scrapped or hung-up in a museum, as inspiration to the young future aerospace engineer. RIP Jim Bede. Not a perfect airplane guy, but always pushing to make things better for aviators while others went with the mainstream flow.
> The BD-5 is a propeller-driven plane with an internal combustion engine, which Bede derived from a sailplane version he never sold
Incorrect.
The BD-5 design was copied, deliberately and publicly, from a Schweizer glider. The goal was, always, to produce a powered light aircraft. The B model, the glider, was an offshoot of the A model. As it turned out, the A model wings were substantially under-designed, and an intermediate length was substituted on most models. All of the designs initially made considerable use of fibreglass, but the entire series was moved to aluminum as the orders poured it.
The design was flawed from conception to construction. It fails due to a well-known issue in aircraft design, as it is "close coupled". The short length of the aircraft means that there is limited distance between the various force points like the CoG and CoF and the control surfaces. Exasperating this is the rear mounted engine, which means there's only, literally, inches between the heaviest part of the aircraft and the control surfaces. That means the controls have to be made larger so they have enough force to operate at low speeds. However, this also means that they are dramatically overpowered at higher speeds. There's no way around this, its basic physics. The "solution" for more expensive designs is powered controls and artificial feel.
Worse, in terms of the length of the aircraft, moving the pilot's seat a few inches is more of a relative shift than it is in, say, a Cessna. This means the aircraft is extremely sensitive to changes in W&B. Even something as minor as burning off fuel will require constant trimming, and that trim point will, for the reasons outlined above, change with speed.
So all of this conspires to make the aircraft difficult to fly on approach. As the aircraft slows the trim keeps changing. Combine that with high approach speeds and ever-more-sensitive controls. And finally, put the thrust line above the aircraft, so if you goose the engine it pushes the nose down, precisely the opposite of what you want it to do.
There is a reason a Cessna looks like it does. It is, for the vast majority of cases, the proper layout for an aircraft. Canard and other layouts have well known advantages in particular situations, but these are generally offset by their disadvantages which is why they are used only in edge cases like fighters.
The BD-10 was a joke from start to finish. Bede had no idea what he was doing, which is not surprising because he never really did any of the design on any of "his" projects - the actual design was left to young engineers typically fresh out of university. In the case of the -10, it was designed using a piece of Mac software known as MacFlow which had a number of bugs in both the software and the models. They initially predicted supersonic performance, but this was due to a bug in the model, From that point on the performance of the aircraft continued to degrade as drag and weight increased continually.
Building a transonic aircraft from pop-rivets? Yeah, that will work...