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BA flies 747 on 3 engines LAX-UK - New EU comp rules
Alan S
sednews On Sun, 27 Feb 2005 18:57:20 GMT, "Robert J Carpenter" wrote: | |"Don Klipstein" wrote in message ... | In article , Mxsmanic |wrote: | Don Klipstein writes: | | Then again, I would think a jetliner pilot can easily avoid a |stall if | engine failure or additional engine failure occurs. If the plane |is | nosed-down before it slows to below stall speed, it will lose |less | altitude and do so more gently than if it stalls. | | Some airliner configurations can enter a superstall from which |there is | no recovery. Stick shakers and stick pushers are supposed to |prevent | that, however. | | What is a superstall? How does engine failure in level flight |cause | this? Why have I never heard of a jetliner crashing from one? | |The first two BAC 1-11 orototype aircraft entered stalls (during |testing) from which they couldn't recover. The T-tail configuration |had the elevator in the turbulence from the wing and had no effect. |The British are thus very likely to require stick a pusher on a T-tail |aircraft. | Nice to see an intelligent response. As a newby here It's taken me a little while to realise that this ng has just as many kids pretending to be experts as any other. *sigh* I'm no expert, just an oldie with a flaky memory. But I worked on BAC-111 avionics in the RAAF in the '70s. It wasn't called "superstall"; it was "Deep Stall". IIRC a test pilot died discovering it, effectively flying backwards into the deck. Once the deep stall was entered, it was unrecoverable. To counter it, the aircraft had external sensor vanes, a stick shaker to alert pilots and an over-ride hydraulic system to force the stick fully forward when a stall angle was exceeded. From memory, shaking occurred at 28 degrees and the ram thrust came in at 34 degrees. It was certainly no joke, even less so when we had a failure of the system caused by faulty design and the ram operated once shortly after take-off. There were footrests on the dash for just such an emergency, and the pilots in that instance needed them, and every ounce of strength their adrenalin gave them. That led to modifications limiting the vane motion. They had reversed 180 as the aircraft taxied to the end of the strip and stayed reversed (ping-pong ball effect) when the aircraft turned into the wind. The stall sensor operated as soon as it was armed by the oleos retracting. To the actual pilots here, think about that timing:-) Uh, no. There was no limit on the vane motion, the safety factor arose from the design of the system, which varied the pressure on the stick from full aft about 180 lbs of force at the yoke to near zero at full forward. the footrests were footrests. You wouldn't have time to get your feet off the pedals and onto th epanel if it fired off uncommanded. There was a "Dump valve (curiously enoug, one of three gadgets so named n the cockpit, another leading Brit aircraft ergonomic feature) wich would release the nitrogen pressure in the line to the push ram. It was awkward to pull against the stick, but for th efew seconds it took to scramble around and find the dump valve, turn and pull it, it was more than manageable, chich was the whole idea. Ask me how I know this. I'm not a pilot (or someone pretending to be one) and I didn't work on other T-tail aircraft, but I believe a similar system was used on DC-9s, 727s and similar aircraft. It's probably in use today, but I haven't worked on a plane for 25 years. Actually, no, the 1-11 was the only one (some others had nudgers, a far less invasive system) Nothing else needed the stick pusher. Except on th eBrit register due to "not invented here" syndrome. Bertie |
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