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17 June 2003, 01:50 PM

The book "Aeroelasticity", by Bisplinghoff, Ashley, and Halfman (BAH), Addison-Wesley Publishing, 1957, is a highly respected textbook on aeroelasticity and it would be surprising if their description of torsional divergence in the Fokker DVIII were completely inaccurate. My assumptions about the DVIII wing being related to the DVII wing came from a figure caption at another web site. Thanks to Cigogne for setting me straight on this. Since BAH directly quotes Fokker ref. [1-6] - Fokker, A. H. G., "The Flying Dutchman, " Henry Holt and Co., Inc., 1931, perhaps some of the BAH claims can be easily verified. Unfortunately, I don't have a copy of this book. Perhaps someone in this forum who has the book can check the quote? If the reference is correct, then it would be surprising if Fokker would have admitted to a design error if it really was an issue of sloppy fabrication as claimed by Cigogne. Of course, aeroelastic effects were not well understood in 1918, so Fokker should be credited with discovering this phenomena on his own! Also, no mention is made in BAH as to how Fokker corrected the problem, though he must have come up with a fix. What was the fix?

If the BAH quote is accurate, who were the pilots that were killed in the DVIII? I doubt that a mono-wing could fail in a dive without killing the pilot!

Torsional divergence is usually associated with high aspect ratio wings with insufficient torsional stiffness. I am not familiar with the DVIII wing, but if the wing had a plywood covering as stated by Cigogne, it seems as though the DVIII wing would have had a relatively high torsional stiffness. The Bublitz reference given by greenknight sounds interesting. I would be surprised if the torsional behavior of the DVIII was not examined more closely in the post-war period, since aeronautical engineers would have been very interested in understanding aeroelastic problems associated with the transition from the biplane to monoplanes. For example, BAH state: "In later experience with the D-8, subsequent to the war, U. S. Army Air Corps engineers at McCook Field, Dayton, Ohio, observed a violent but nondestructive case of wing bending-aileron flutter. This was cured by statically balancing the ailerons about the hinge line, a technique which seems to have been pointed out first by Baumhauer and Koning (Ref. 1-7) in 1922."

17 June 2003, 01:50 PM	#4 (permalink)
NiedHF Guest Posts: n/a	The book "Aeroelasticity", by Bisplinghoff, Ashley, and Halfman (BAH), Addison-Wesley Publishing, 1957, is a highly respected textbook on aeroelasticity and it would be surprising if their description of torsional divergence in the Fokker DVIII were completely inaccurate. My assumptions about the DVIII wing being related to the DVII wing came from a figure caption at another web site. Thanks to Cigogne for setting me straight on this. Since BAH directly quotes Fokker ref. [1-6] - Fokker, A. H. G., "The Flying Dutchman, " Henry Holt and Co., Inc., 1931, perhaps some of the BAH claims can be easily verified. Unfortunately, I don't have a copy of this book. Perhaps someone in this forum who has the book can check the quote? If the reference is correct, then it would be surprising if Fokker would have admitted to a design error if it really was an issue of sloppy fabrication as claimed by Cigogne. Of course, aeroelastic effects were not well understood in 1918, so Fokker should be credited with discovering this phenomena on his own! Also, no mention is made in BAH as to how Fokker corrected the problem, though he must have come up with a fix. What was the fix? If the BAH quote is accurate, who were the pilots that were killed in the DVIII? I doubt that a mono-wing could fail in a dive without killing the pilot! Torsional divergence is usually associated with high aspect ratio wings with insufficient torsional stiffness. I am not familiar with the DVIII wing, but if the wing had a plywood covering as stated by Cigogne, it seems as though the DVIII wing would have had a relatively high torsional stiffness. The Bublitz reference given by greenknight sounds interesting. I would be surprised if the torsional behavior of the DVIII was not examined more closely in the post-war period, since aeronautical engineers would have been very interested in understanding aeroelastic problems associated with the transition from the biplane to monoplanes. For example, BAH state: "In later experience with the D-8, subsequent to the war, U. S. Army Air Corps engineers at McCook Field, Dayton, Ohio, observed a violent but nondestructive case of wing bending-aileron flutter. This was cured by statically balancing the ailerons about the hinge line, a technique which seems to have been pointed out first by Baumhauer and Koning (Ref. 1-7) in 1922."