This airplane, which to me always looked like a cobra, was an Aerodynamics Engineer's dream and a Manufacturing Engineer's worst nightmare. Early in the development phase NAA wind tunnel engineers discovered that with the right angle of wingtip droop there was an interaction between the shock waves generated by the wingtip and engine duct that created additional positve pressure under the wing. A positive pressure under the wing means LIFT! It was estimated the design could achieve a L/D ratio of 8.8 ( ole' "double-eight balls" as it was called). Other supersonic jets of the day were lucky to see a L/D of 4. Consequently, the XB-70 would be a Mach 3 cruise vehicle rather than a subsonic cruise supersonic dash machine. The media of the day said this airplane "rode its own shockwave".
The penalty for cruising at Mach 3 was the the outside skin tempatures reached 600degrees F. This meant the plane would be made of stainless steel and titanium rather than aluminum.and that there could not be any bladders in the fuel tanks. The 2 planes that were produced made extensive use of stainless steel honeycomb sandwich panels which had a very high strength to weight ratio. One of the major problems was attaching the wing to the intake duct. There was no spar carrythrough so the wings had to be butt welded to the duct. The original welding techniques did not produce a successful weld. Much time and money was spent developing an electron beam welder for the task. These machines did the job but could only weld a few feet a day. This problem added about a year to the completion schedule.
The high skin temperatures meant when the fuel burned off the empty tank would become a flying bomb. The plan was to introduce inert nitrogen gas into the empty tanks to prevent an explosion. It turned out to be one thing to seal the tanks (without bladders) to jet fuel but entirely another to seal them to pressurized nitrogen. In fact, the first vehicle never did have use of one of the main tanks.
I used Paul Matt's beautiful drawings as FSDS backgrounds for this project. I modeled the 3 wingtip positions as display functions since there is no speed variable in FS2002 which you can grab. The tips are straight and level for slow speeds, droop 22 degrees as you approach transonic speeds and droop 65 degrees at supersonic speed. I created the elevons and the unique 'Tilt-Twist-Rotate" maingear cycle with SDLEdit. The windscreen does straighten out at high speed although it is a little hard to see because of the scale of this plane. The vertical fins have a unique motion because the hinge line is closer to horizontal than vertical.
This model will reach Mach 3 at altitudes greater than 35000 feet. I have flown it up to 65000 feet without problems. I do recommend that you keep it below Mach 1.5 until you reach 35000 feet as it has a tendency to oscillate in pitch if the speed is too high at the lower altitudes. If this happens to you just pull back on the stick and burn off some speed. The XB-70 had no spoilers or air brakes so you do need to give some room to burn off speed on landing. This project was created for FS2002 and I have not tried it in any other sim.
INSTALLATION: Unzip xb70.zip into a temporary folder. Open the gauges folder and copy all the gauges into the FS2002 Gauges folder. Copy the folder XB-70 into the aircraft folder in FS2002. Close everything and fire up FS2002. This plane will be listed under North American as XB-70 in the aircraft select list.
PANEL: I have included Curt May's excellent Valkyrie panel as part of this file.
SOUND: The XB-70 was one of the noisiest (if not the noisiest) airplanes ever produced. Those 6 J-93 engines simply screamed. I am not aware of a dedicated sound file for this vehicle so I included the sound file for Michael Shulgin's Sukhoi T-4 which I believe has an appropriately nasty sound.
LEGAL: This project is released as freeware. You may modify it, repaint it, etc., upload to another website as long as it is not for profit. You need my written permission to use any of these files for commercial purposes; otherwise just give me credit for the original design. This airplane should not hurt your computer but I am not responsible if it causes problems.
