There are a lot of asymmetric designs on this page: www.obliqueflyingwing.com and in the comprehensive history paper attached at http://www.obliqueflyingwing.com/OWhistory.pdf.Tophe said:Thanks a lot ;D Matej: I had never seen this XV-2 previosly, and I have immediately updated my asymmetric-aircraft page with it (at the end of http://cmeunier.chez-alice.fr/Asymm_addition.htm ). Thanks again! ;D
LOCKHEED-GEORGIA is STUDYING a 100-passenger Mach 0.8 , V/STOL transport, turbofan powered and with a gross weight of 76,000lb. It would have a 500 n.m. range. The project uses four lift fans each of about 20.000lb thrust and four propulsion turbofans. two in wing pods and two in the tail. The former are used to provide low-speed roll control and the latter pitch control. The use of the propulsion engines for attitude control brings the optimum number of lift engines down to four, according to Mr T. Gardner Hill, senior research and development engineer. Lockheed-Georgia.
When lift engines are installed in pods some distance from the aircraft e.g. the unbalanced moment occurring after an engine failure could be of greater magnitude than a bleed-air roll-control system could handle; and the only recourse would be to shut down the corresponding engine on the other side. This in turn would require a considerable number of such engines, to make sure that the percentage loss of lift was suitably low. Lockheed studies indicated that the optimum number of wing podded engines would be eight. In the Lockheed design the lift fans are situated close to the e.g. and the unbalanced moments are small enough for the hover control system to trim out the forces and still meet the hover manoeuvre requirement without the need to shut down the corresponding powerplant. The engine location reduces the moments of inertia, reducing hover control requirements,which in turn reduces gross weight. According to Lockheed the lower weight and smaller number of engines would reduce cost considerably.
Three sources of power are available for control in the hover; bleed-air thrust, lift-engine thrust and cruise-engine thrust. The control moments vary directly with the aircraft moment of inertia, which itself varies roughly as the square of the gross weight. Lockheed suggest that for an aircraft with a gross weight above about 60,0001b there is insufficient thrust from bleed air to provide the desired amount of control. When lift engines are situated close to the e.g.. as in this project, the demands on a thrust-modulating system would be excessive, because of the short moment-arm. In the Lockheed project, therefore, the cruise engines areused for attitude control. By diverting their thrust, both up and down control effectiveness should be good. This system is not subject to the response-lag associated with thrust modulation of lift jets. In changing from horizontal to vertical flight, tailpipe clamshells close, while louvres in the top and bottom of the pod open to divert the thrust from horizontal to vertical. The louvres can then be moved to give differential exhaust areas between top and bottom, when upward and downward thrust is demanded for roll or pitch hover control. By deflecting these same louvres sideways on the two near fuselage-mounted engines, yaw control can be provided. The four turbofan cruise engines have a bypass ratio of about 2.5:1 and are probably in the 9,000lb-10,000lb-thrust class. The bypass ratio was chosen to give a good match between cruise and hover control requirements and helps to reduce turning losses in the thrust diverter. During hover the two cruise engines on the wing devote their entire thrust to providing redundant roll control while those in the tail provide redundant pitch and yaw control. A V tail has been chosen to avoid problems of exhaust impingement on tail surfaces: to retain a long moment-arm for pitch control thrust; and to allow side-by-side engine installation to minimise engine-out coupling between roll and pitch axes. The lift engines are installed in the same pods as the undercarriage and are canted at 30°,'their efflux being deflected to the vertical by a rotatable hoop of cascades. Rotation of these cascades towards the front or rear provides a horizontal thrust component for transitions. The cascade blades can be closed during cruising flight.
The canted engine installation was chosen to allow part of the engines to be tucked into the fuselage, with resulting reduction in pod size; to reduce pod/wing interference drag: to reduce pitch-up caused by the turning moment of the lift engine intake air during transition; and to confer the previously mentioned engine-out advantages. The position and thrust level of the propulsion engines should ensure freedom from re-ingestion into the lift fans. By substituting smaller lift engines the design would give an FAA STOL performance with a gross weight of 69.000lb The proposed aircraft would have five-abreast seating; forward and aft ticket counters; and a self-service retractable below fuselage baggage compartment to reduce turn-round time. Estimates indicate that this aircraft would be "cost competitive with any other generally known VTOL concept." But there is no indication of when the project could come to fruition.
hesham said:the Lockheed designed a nice V/STOL transport aircraft in 1969,
it was powered by four turbofan engines and can carry 100-passenger,
its estimated speed was Mach 0.8 and weight 76,000 1b.