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1/2 scale warbirds

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BBerson

Light Plane Philosopher
Joined
Dec 16, 2007
Messages
17,548
Location
Port Townsend WA
Bingelis letter to 1/2 scale warbird designers:



1/2 SCALE PROBLEMS

We will move on to another subject which is of concern and I would like to share with you a letter from Tony Bingelis. This letter is as the result of our observation over the years of some activities within our amateur built movement. This particular incident involves a Vfc scale Focke-Wulf 190 replica of a WWII German fighter which, after some 15 to 20 minutes of a staggering first flight after purchase and attempted ferry flight to New York the day after our 1979 Oshkosh Convention, ended in a near tragic crash. The mile drive in Red One with

son, Tom, and the ball of fire and smoke that erupted from the corn field will never be forgotten. Nor will the run through 10 foot high corn with the fire extinguisher to find the pilot thrown clear of the fire but severely injured. This was indeed a miracle. A 230 pound pilot, parachute, tie-downs, baggage, fuel and oil came to about one half the empty weight of the aircraft. After months in Mercy Hospital in Oshkosh he is home recovering — a very fortunate and wiser person . . . but let's share our views with Tony.

Dear Paul:
I'm sorry that I was unable to respond to your letter of September 12, 1979 before this. In the letter you expressed your dismay over the tragic record being developed by small scale replica aircraft and asked for my comments on the subject. I do have an opinion on the matter and perhaps it is very much like your own. At any rate, I, too, feel very strongly that these small scale war replicas are marginal aircraft at best and could be deadly instruments in the hands of low time pleasure pilots. I did not know of the Focke- Wulf 190 accident until I read your letter.

Some months ago I talked with an individual about the airplane. The workmanship was not outstanding but appeared to be airworthy. I said the usual nice things about one's aircraft but I believe he told me he purchased the aircraft from someone else out of state. The airplane looked fast with its retractable gear and war paint and I asked about the performance. The owner told me that it was too heavy and it didn't do too well on its 100 hp engine. As a matter of fact he said his cruise speed was something like 120-125 mph. I somehow had expected to hear 150-160, at least. He said the climb was sorry and was quite disappointed with the aircraft.

Another thing that bothers me about all this is the general revelation given me by the letters I re- ceive. People who are totally uninformed of aircraft design, aircraft construction and the realities of aero- dynamic principles, blissfully write and ask why they can't use a different or bigger engine, change the gear to a retractable or tricycle installation, add spoilers or two or three feet to the span . . . or cut the span by a like amount. A recent letter received from a gent who wrote and told me that he didn't like any of the designs he saw and he was going to build his own de- sign but he didn't know where the landing gear should be.

A lot of builders write me because they can't get information from the designer of the aircraft. And I can understand why. Some of the changes proposed ab- solutely have no merit or logic. If it is a single seater why can't the builder add another seat or another en- gine? Another doesn't like wood construction and wants to change it to an all-metal job. Tell me what changes I should make, they add.

Finally, everybody that weighs over 200 pounds

and/or stands 6 feet tall wants to build the smallest airplane he can find. These big guys seem to have a built-in craving for small aircraft. As you know, this really is a dangerous craving. Most of these low- powered designs are operating on the verge anyway . . . add a 245 pound pilot and you have a fused bomb ready to go off aerodynamically or structurally.

As you know, aerodynamic laws don't work the way the lay mind thinks. For example, doubling the horse- power doesn't double the speed. Four seat, store bought aircraft with full gas on board cannot carry four people. Cutting the span to increase speed by reducing drag will usually do so ... straight down on the final turn.

These 1/2 scale replicas. Builders say that is just the right size and don't worry about the distorted scale effect necessary to accommodate an oversized pilot. Shouldn't the pilot be 1/2 scale too? Let's see, that would make him three feet tall right? How about the en- gine, according to scale shouldn't it have at least a 600 to 1000 hp mill up front? How could anyone ever expect such a 1/2 scale aircraft to perform safely on a mere 60 hp VW or even a "powerful" 100 hp?

Outside of that, it's difficult explaining to each budding builder/designer that building or changing an aircraft design is not like modifying a motorcycle or dune buggy or even an automobile. Up in the air things are different and gravity never takes a holiday. I am often tempted to fluff off letters and questions of the nature under discussion but somebody has to tell them . . . alert them . . . of the difficulties, the consequences. Even the reasons why they cannot or should not do what they are thinking.

Designers catch hell. The minute a design is finalized, here comes a builder who wants to know if he can use a 180 hp instead of a 125. I told this to one builder and he said, "Well, why didn't he design it for a 180 in the first place?" I told him that if the designer had any such inclinations he would have done so but he didn't. Then too, if the design was approved for 180, along would come builders who would bug the designer for information regarding the installation of a 200 hp or 300 hp engine. A buyer of plans has not a license to harass the designer or expect any more after buying his plans than to be informed of manda- tory changes.

Well, this is ranging far and wide on the subject but I don't know how to limit the issue. Years ago, builders compensated the lack of sufficient power by building larger and lighter aircraft. This 1/2 scale fever runs counter to that logic and as a result is getting a lot of people in trouble. Almost every article I write has a safety thought or remark in it somewhere.

I wonder if you couldn't get all this before the builders with an article or two by Al Backstrom. He is a good engineer and understands the layman's at- titudes. He might explain the problems of scale ef- fect and Reynolds numbers so that even I could under- stand. Of course, no single article will solve the prob- lem any more than will 100 articles in sequence. Many people will never get the word and many don't want it in the first place. This is a difficult letter to write, Paul, because I didn't know where I was going with the subject . . . and typing a letter without the op- portunity of editing it makes it even more difficult. At any rate, perhaps somewhere in this rambling you may find something of use to you.

Congratulations on a fine job done by all at Tulla- homa. If man ever conquered the elements, the EAA did just that and in the end had a very successful Fly-In, weather notwithstanding. Thanks for the op- portunity to air these thoughts.

Adios, Amigo Tony Bingelis

4 JANUARY 1980
 
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