Actually, Sam, I think we’re talking across each other. The G-loads I was referring to were from the motions of the aircraft, incidental to whether or not the engine was seized, free-wheeling, or running at full power. Fer instance, what kinds of loads are felt at the pylon mount-point should the aircraft suddenly flip over, or roll into a spin? I’m considering the engine as pendant mass, and am not particularly interested in whether or not it’s producing thrust/causing drag. Your discussion with Broomstick is, I’m thinking, about the issues that caused the aircarft to depart from controlled flight, while I’m considering whether or not the engines departed the wing as a result of that loss of control.
We’ve established that the arcraft had a design feature enabling the engines to depart cleanly under certain circumstances, which it appears at least one did. Further, it appears that neither engine suffered a catastrophic uncontained failure, so it would have to be some other cause. Now, was that cause aerodynamic loads, G-loads induced by uncontrolled flight, or something else?
Derailing the thread a little - as I’d really rather not use the word “hijack”.
one of those incidents being SAS 751 - an MD-81 losing both engines about a minute into the flight due to ice ingestion - at 3000 feet. Engines caught fire, but those were put out. Glided into a field, no fire, fuselage broke up, no lives were lost. Someone was either very good, very lucky or both. And of course, there are more open fields around Stockholm than around JFK.
Anyhoo, apparently noone had thought to include speed and flaps position for an MD-80 unpowered landing, so it was seat-of-the-pants.
I guess I had a point, but I must’ve forgoten it in my other suit.
Re: Birds, tails, rudders… -birds do have tails but they do not have rudders or stabilizers. It is true that some birds’ tails form a “V” shape in flight when viewed from the rear, but not all. There is nothing different in principle between the way a simple rudderless flying wing turns and the way a conventional airplane turns. - MC
Because I don’t know you from Adam and if you have any credentials in this area I am totally unaware of them. If, however, you do have formal education/training/experience in these areas please let us know.
I’ll promise not to get upset at your assumption I would assume jet and prop planes to have the same engine-out characteristics if you don’t get bent because I have no way of knowing your actual experitise in these matters until you tell me.
Ah. Book values. Those book values are set by test pilots working with brand new planes under ideal (or nearly so) conditions. The average Cessna pilot is not going to achieve this under actual emergency conditions. Add in the fact that most of the single-engine fleet is 25 years or older… well, hangar rash and various other forms of wear will decrease efficiency. When in training the rule of thumb was to assume a 7:1 and if you got better that was great. You still try to nail best-glide airspeed, of course, but it’s a way of giving yourself a little extra cushion when eyeing potential landing sites. It’s that gap between theory and reality. Not to mention a good brisk downdraft can really bum you out if you’re flying a Cessna glider, and ditto for any other atmospheric fun you might encounter on the way back to earth. Mind you, I continually try to better my performance whenever I take the controls but fact is everyone goes through a period in flying where the book values are a goal to aim for and not necessarily something actually achieved.
Something like the Mooney will, indeed, have a better glide ratio - it’s not just the retractable gear but the entire plane is more aerodynamic than the typical SEL Piper and Cessna.
I would assume that the pilots of passenger airliners would be much much more likely to achieve “book value”, even under adverse conditions. Certainly, the airline pilots down at the local field who fly little planes on their off hours get MUCH better efficiency than I do - with their education and experience I would expect no less.
If you don’t know me from Adam, why do you have to bring up my credentials or lack thereof at all? Can’t my arguments stand on their own? Do you have to use ad hominem arguments? Anyway, let’s drop it. For the record, I studied physics and engineering in University, and studied aerodynamics extensively after that time on my own (I was involved for a while in the homebuilt movement, and was designing my own airplane). I have a PPL, finished the Commercial license (failed the medical… sigh), and then became ground school instructor specializing in aerodynamics and meteorology. But I haven’t been formally involved in that stuff for a long time now, and nowadays the closest I get to any of it is chatting about it in the SDMB.
Sure, older aircraft can’t generally put up the performance numbers of new ones, but there’s no way the glide ratio is going to drop from a book value of 10:1 down to 7:1 if you are hitting the book speeds accurately. But sure, the average pilot who can’t hold airspeed within 5 kts is probably going to see results closers to what you said.
However, the main point I was making was that parasitic drag like landing gear is not nearly as big a factor for glide as is induced drag, which is primarily determined by the aspect ratio of the wing. I owned a Grumman AA1 for a long time, which was an extremely clean aircraft for its type. It could do 135 mph on 108 hp, which is much faster than a Cessna 152 using the same engine. But it glided like an aerodynamic brick, because it had fat stubby wings. A Cessna 152 has a wingspan almost 10 feet longer, and has the same gross weight. And it has a better glide ratio, even though it’s got more crap hanging off it than a christmas tree.