What happened to the UDF seemed like a good idea?
The straight turbojets will always out-climb the fan competition. The Learjet 20 series will out climb just about anything made today (except possibly for the Lear 60), but from a fuel consumption and efficiency perspective, plus noise issues, they don't work all that well.
It was too loud, sounded like a giant P-51 with big lungs. In flight damage was another fault. Bird strikes and FOD were deadly.
I flew the 727-100 for Usair. When we received the first of the 200 series I recall I was given a pamphlet on "differences" and NO additional training. My first flight in the 200 was exciting to say the least. First of all, sitting on the ramp, it was brand new. Maybe 5 hours. It looked beautiful. We were going from Kbuf to Kroc, a 20 minute flight with a light load on board. As we accelerated down the runway it felt "strong". When we rotated for takeoff I thought I was riding on top of a rocket. I could not believe the feeling of power. Basicly I was just hanging on to the thing as we soared up up to 5000 feet where I had to level off for the quick trip to Kroc. I was still trying to feel the aircraft out when we were setting up for landing. To say we were busy in the cockpit for about 15 minutes would be an understatement. As they say the landing was uneventful or at least I think it was. Time dims the memory but I do remember when we got to the gate thinking how the hell could they give me the keys to this thing with only a small pamphlet and no additional training. I guess it was "on the job" training. Loved the airplane. Sweet memories.
Don- All the modern fighters are powered by low bypass turbofans, so you might want to rethink that. What determines performance is T/W, drag, wing loading, etc not the propulsion category.
I get the noise issue, but bird strikes more 'dangerous' than to, say, a single engine prop plane? FOD? Cheers, Ian
Foreign Object Damage. A bird strike at 120 knots is one thing. Unless huge or multiple birds, will likely not bother the prop or engine, but a direct hit on the canopy might cause problems. A bird strike at 300 knots on parts turning at really high rpm is another thing. If large enough, will likely take out the engine, as happened to Sully of Hudson River fame. The bigger the diameter of the fan, the easier for a bird to hit the fan, so the UDF had much higher odds of getting a bird where you did not want it. Those big, skinny fans were more susceptible to damage than the thicker ones on a ducted fan, too, and also more susceptible to out of balance conditions from damage.
My U.S. house neighbor is a pilot with United. He started flying for them in 76 and his first jet with them was co-pilot on the 727. He then moved into the L1011, DC10 and now in the 777 as a captain. His favorite plane is the 727. He also flies corporate part time. The corporate guy he flies for, he's had several Gulfstream's III to G5. Now has a Global Express. Even the corporate planes, he says they are not as much fun as the 727.
Even a small bird striking those props would be fatal not only to the bird but to the props. They were too delicate and under heavy loads. From what I remember, they were CRF, somewhat flexible, high rpm, and very loud.
Sorry, I couldn't resist! I always thought that unless you hit an entire flock of geese or the like (ala Sully) the fan would just 'eat them' without causing too much trouble? Incidentally, a good buddy (a centurion off a carrier) once told me Sully should have pulled up to avoid 'em. No idea if true, but he claimed the birds 'fold' their wings and drop in such situations. That Sully went down was the mistake? Which is why I'm a little surprised any kind of FOD (learn something every day ), could really hurt them. I kinda 'grew up' with CRF in the race car biz, and that stuffs *strong*. It'll shatter given enough force, but short of an eagle hitting the thing I'd have thought it wasn't really possible. Noise is of course another issue. Cheers, Ian
And can the modern fighters out-climb the early Century series fighters or an F-4? How about top speed? I'm not saying that they're not superior aircraft in almost every way, except for raw climb performance and maybe top speed. EDIT: You actually made my point. The fighters are powered by LOW BYPASS turbofans. Modern airliners and business jets are powered by HIGH BYPASS turbofans. I think the 727 was also a low bypass engine. The low bypass (or no bypass) engines simply provide a different sort of thrust-- much higher velocity (but lower quantity) than the high bypass engines.
Gas turbines produce gobs of torque and this has been used to turn those big fans that have been placed on the front of the gas producer. Mass flow (heavy push) has replaced the high velocity flow that is far less efficient than the fan. From drag racing days. " There is NO substitute for cubic inches!"
Don- Yes, all of the above. Google Streak Eagle, powered by 2 TF100 turbofans. Saw it at Cannon AFB in the mid-late 70s Even my 60's technology F-111 had twin TF30 turbofans, same as early F-14s. T/W on the afterburning turbofans was much higher than on the turbojets, and at cruise, consumption was much less. Think about an F-22A now with F119 engines in the 35,000 lb thrust class. Supersonic cruise in military power, service ceiling above FL600, max speed like all aluminum airframe fighters limited to short periods up to ~mach 2.5.
