sv51macross Posted May 25, 2009 Share Posted May 25, 2009 (edited) I'm confused. I've heard the FGR.2 was slower than J-79 powered Phantoms, but the Speys put out about 3000lbs more [combined] thrust than the J-79s. What gives? Were they Spey engines that much heavier? [edit clarification] Edited May 25, 2009 by sv51macross Quote Link to post Share on other sites
MQM107 Posted May 25, 2009 Share Posted May 25, 2009 I'm confused. I've heard the FGR.2 was slower than J-79 powered Phantoms, but the Speys put out about 3000lbs more [combined] thrust than the J-79s. What gives? Were they Spey engines that much heavier? It all comes from fitting a engine into a established fuselage as opposed to designing the fuselage around a engine. And a tubofan as opposed to a turbojet. The British Phantoms required substantial airframe modifications, with the rear fuselage width increased to accommodate the Speys, and 20% larger intake ducts to provide the greater airflow required by the Rolls-Royce engines. Even then, the Speys were temperature-redlined to Mach 1.9, due to cost-reduction measures imposed on Rolls-Royce that dictated use of cheaper metals. Between the airframe changes, which undermined the Phantom's "area ruling", and the limitations of the engines, the British Phantoms were sometimes described, most likely by a certain famously caustic senior British aviation writer, as the "most powerful, most expensive, and slowest Phantoms in the world." Mike Quote Link to post Share on other sites
DonSS3 Posted May 25, 2009 Share Posted May 25, 2009 I don't think the difference was so much a function of weight as it was aerodynamics. The intakes had to be enlarged to take in the greater amount of air that the Spey required. This "widening" continued on aft of the intakes, thus compounding the drag problem. So, essentially, the increase in thrust was offset by the increase in drag. Quote Link to post Share on other sites
spike7451 Posted May 25, 2009 Share Posted May 25, 2009 See my post HERE. Merv Quote Link to post Share on other sites
alrite Posted May 25, 2009 Share Posted May 25, 2009 They basically had more drag than any other phantom due to the larger fuselage and intakes. Slower at high altitude but faster on the deck and better acceleration/climb from low to medium altitude. Anything above 40 kft wasn't very good from what I've read. cheers Quote Link to post Share on other sites
PlasticWeapons Posted May 25, 2009 Share Posted May 25, 2009 "What happens when you Spey a Phantom? It gets slower and fatter." Quote Link to post Share on other sites
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