Does anybody know why the droop nose of the first Boeing 2707 SST had two joints instead of one? The L-2000, Concorde, and TU-144 all had droop noses with a single pivot point, I'm curious why Boeing engineers added the mechanical complexity and future maintenance costs of a double jointed droop nose. Did the higher Mach 3 cruising speed of the jet require the longer nose?

https://www.youtube.com/watch?v=jIrDpjPm1Uc

Looks like the second articulation was needed for the swing wing version and its shorter front gear leg
for not scraping the nose in the dirt.
concorde starts out with a higher angle of attack on the ground ( delta wing, no canard )

this video doesn't show the second "knick":
https://www.youtube.com/watch?v=I7RUDDb1UA8

It was to have been much larger than the Concorde/others. That's the main reason; to allow the pilot to visually locate the runway meant moving a lot more "nose" out of his way/field of view.

Looking at the design, I am always amazed at the mechanical complexity. Swing-wings with all those hydraulic and moveable surfaces on the mobile section? A double-articulated nose? All that dead space with the area ruling? I know that fuel was dirt-cheap at the time, but come on.

DocLightning wrote:

Looking at the design, I am always amazed at the mechanical complexity. Swing-wings with all those hydraulic and moveable surfaces on the mobile section? A double-articulated nose? All that dead space with the area ruling? I know that fuel was dirt-cheap at the time, but come on.

They did run into massive weight issues, forcing abandonment of the swing wing altogether.

Indeed an overcomplicated beast.

Starlionblue wrote:

They did run into massive weight issues, forcing abandonment of the swing wing altogether.

Indeed an overcomplicated beast.

Which is so messed up because they essentially ended up presenting a clone of the rejected Lockheed L-2000.

There were two main reasons: increase ground clearance and allow the weather radar and nose tip pitot tube to be used when the nose was down, as the forward nose section pivoted to remain parallel to the axis of flight. The double-jointed nose was abandoned late in the 2707-200 stage as the weight reduction push became overwhelming, and the simpler single-pivot nose was carried onto the fixed-wing 2707-300.

Here are some jaw-dropping renderings of that late 2707-200 design, courtesy of an incredibly detailed 3D model. The thing was basically a Transformer, beautiful but bizarre.

https://blenderartists.org/t/boeing-2707-200-first-flight/652740

DocLightning wrote:

Looking at the design, I am always amazed at the mechanical complexity. Swing-wings with all those hydraulic and moveable surfaces on the mobile section? A double-articulated nose? All that dead space with the area ruling? I know that fuel was dirt-cheap at the time, but come on.

Boeing thought they could get back the weight penalty from the increased aerodynamic efficiency of the swing wing, and it did have a ~1.5 point L/D advantage over the fixed-wing Concorde, L-2000, and later their own 2707-300. They just badly miscalculated how hard it would be to integrate a very slender fuselage and wing structure with all these moving parts. As they got into detail design, the airframe turned out to be more flexible than they expected. It was particularly problematic in low-speed pitch maneuvers like go-arounds and collision avoidance, where the aft CG created by the tail-mounted engines resulted in a very short moment arm for the elevators and thus required enormous elevator authority. This triggered the addition of the canard on the -200 iteration, which put further stress on the long, thin fuselage. The structural reinforcement needed to fix the aeroelastic problems sent the -200 into the dreaded weight-thrust-fuel death spiral. The FAA was concerned about operating economics and refused to budge on the contractually-stipulated 675,000 lb. MTOW, so eventually there was nothing left to cut but the swing-wing itself.

Apparently the aerodynamics were pretty solid and continued to improve over time, but not enough to solve the weight problem. The 2707-300 wing was a big step back aerodynamically, especially at cruise since it was sized and swept to meet takeoff noise requirements. The swing-wing's inherently good low-speed performance plus its huge flap system gave it superb takeoff performance that could be traded for noise reduction in most mission scenarios. That was not the case on the -300, and late in the program, Boeing and GE were forced to delete the afterburner and introduce a "bypass tube" to meet ever-tightening noise standards (similar changes were planned on the never-built Concorde B). This would have sent the -300's gross weight over 800,000 lbs. as the GE4's mass flow and thus size increased substantially to make up for the thrust loss.

By the way, the plywood mockup in the video shows an earlier area-rule design that did waste a lot of fuselage space. They later revised it by widening the fuselage ahead of the wing and tapering it more sharply to the tail. This allowed 2-3-2 seating over almost half the length. Seat count didn't increase much, but the new configuration was aerodynamically better, faster to board/deplane, and more appealing to passengers.