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