Quiet Airliners of the Future?

On Wed, 14 Sep 2005 23:46:10 GMT, Chris Kennedy
wrote in ::

but the
issue is with uncommanded roll as a consequence of turbulence.

If the aircraft is not maneuvering (or even if it were), the
electronically augmented control system would detect an incipient wing
displacement before a human could detect it, and issue the appropriate
control input to counter it. These commands would occur so rapidly as
to be virtually undetectable by the occupants.

Think of the electronic suspension systems available on some of
today's automobiles*. They are capable of providing a smooth ride
over the roughest of roads by sensing body dip, and immediately
extending the suspension to prevent further excursions. These
corrections happen in milliseconds; it verges on magic.

If the roll
rate is brisk, there may be some increase in G felt by passengers in
the rising wing, and decrease in G felt by those in the descending
wing, but with today's computerized fly-by-wire control systems, all
these concerns could be largely eliminated in nearly all cases.

Unless you're suggesting that fly by wire could automatically limit the
roll rate to limit the acceleration felt by outboard passengers I'm
unclear how it would address the problem.

I'm confident that an electronic control system could dampen all but
the most severe turbulence induced excursions, in addition to seeing
that the commanded roll rate was strictly met.

There's also the roller coaster effect -- being on the high side and
looking down the width of the cabin at what seems like an exaggerated
angle -- but I suppose one could deal with that with dividers of some
sort.

Exactly. First class would be along the longitudinal axis with coach
toward the wing tips with obscure partitions separating them.

There's also the issue of just how one evacuates such an aircraft.

Umm... Crashworthyness would be an issue less amenable to resolution
than evacuation.

As I said, good for freight, but I'd take some convincing before I flew
in one.

In the event of an in flight electrical failure disabling the
electronic control augmentation, it could get "interesting." What
does Airbus use to overcome that issue?

Of course I'm not too thrilled with the idea of riding in an
A380, either.

Right. In the event of a 800+ passenger stampede, one would likely be
trampled before he could clear the aircraft. :-)




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Larry Dighera wrote:

but the
issue is with uncommanded roll as a consequence of turbulence.


If the aircraft is not maneuvering (or even if it were), the
electronically augmented control system would detect an incipient wing
displacement before a human could detect it, and issue the appropriate
control input to counter it. These commands would occur so rapidly as
to be virtually undetectable by the occupants.

Most contemporary transport aircraft have gust alleviation systems (not
so much for ride comfort than to reduce structural loads); the B-2 has a
similar system. The systems have only limited ability to counter roll
but it's not for want of trying -- it's sort of entertaining looking out
and watching twitchy spoilers trying to keep the wings level -- or the
wingtips from trying to touch.

Actuator response times, interactions with the stability of the design
and the possibility that the roll rate induced by gust could exceed the
roll rate of the aircraft place limits on the magic that you can
perform. It's not to say that you can't come close.

Think of the electronic suspension systems available on some of
today's automobiles*. They are capable of providing a smooth ride
over the roughest of roads by sensing body dip, and immediately
extending the suspension to prevent further excursions. These
corrections happen in milliseconds; it verges on magic.

Yet more technology grafted on from Lotus. I was never quite understood
why they never commercialized that technology -- save for the fact that
it sucked power and had really bad failure modes.

Unless you're suggesting that fly by wire could automatically limit the
roll rate to limit the acceleration felt by outboard passengers I'm
unclear how it would address the problem.


I'm confident that an electronic control system could dampen all but
the most severe turbulence induced excursions, in addition to seeing
that the commanded roll rate was strictly met.

That's sort of my point. Unless you limit commanded roll rate to
something small you haven't done anything to address the problem of G
(un)loading for the outboard passengers, and setting the roll rate limit
low creates its own class of problems.

There's also the roller coaster effect -- being on the high side and
looking down the width of the cabin at what seems like an exaggerated
angle -- but I suppose one could deal with that with dividers of some
sort.


Exactly. First class would be along the longitudinal axis with coach
toward the wing tips with obscure partitions separating them.

Yeah, that's the notion I was after.

There's also the issue of just how one evacuates such an aircraft.


Umm... Crashworthyness would be an issue less amenable to resolution
than evacuation.

Both would be -um- problematic.

In the event of an in flight electrical failure disabling the
electronic control augmentation, it could get "interesting." What
does Airbus use to overcome that issue?

They don't. Everything is inputs to the redundant autopilot system;
stick and throttle are suggestions, not really commands. Raise your
hand if you've had to sit on the ramp while they do a complete engine
shut down in order to reboot an A320 series aircraft prior to departure
(it's happened to me twice).

Of course I'm not too thrilled with the idea of riding in an
A380, either.


Right. In the event of a 800+ passenger stampede, one would likely be
trampled before he could clear the aircraft. :-)

That's assuming that you weren't in the middle of a refreshing mud bath
with cucumber slices on your eyes (if you believe for a moment the
claims of Airbus and Branson that A380s will have such amenities as
opposed to high density seating).

"Larry Dighera" wrote in message I would guess that much of the
inefficient airline fleet would not be
competitive in tomorrow's airline industry, and should be relegated to
the junkyards. How else will tomorrows airlines be able to be
competitive?

Here's a question. Will replacing a $3mil medium by-pass jet with a $28mil
high bypass jet save money? Lower mortgage apyment of lower fuel bill, which
is better?

D. (answer to follow)

On Fri, 16 Sep 2005 02:46:39 GMT, "Capt.Doug"
wrote in ::

"Larry Dighera" wrote in message I would guess that much of the
inefficient airline fleet would not be
competitive in tomorrow's airline industry, and should be relegated to
the junkyards. How else will tomorrows airlines be able to be
competitive?

Here's a question. Will replacing a $3mil medium by-pass jet with a $28mil
high bypass jet save money? Lower mortgage apyment of lower fuel bill, which
is better?

D. (answer to follow)


I suppose Boeing would have the answer to that question. I doubt
they'd be considering producing the aircraft if air carriers were not
going to operate it.

In article ,
"Capt.Doug" wrote:

"Larry Dighera" wrote in message I would guess that much of the
inefficient airline fleet would not be
competitive in tomorrow's airline industry, and should be relegated to
the junkyards. How else will tomorrows airlines be able to be
competitive?

Here's a question. Will replacing a $3mil medium by-pass jet with a $28mil
high bypass jet save money? Lower mortgage apyment of lower fuel bill, which
is better?

Depends, "How long do you plan on keeping it?"
What is the depreciation schedule?

"Capt.Doug" wrote in message ...
"Larry Dighera" wrote in message I would guess that much of the
inefficient airline fleet would not be
competitive in tomorrow's airline industry, and should be relegated to
the junkyards. How else will tomorrows airlines be able to be
competitive?

Here's a question. Will replacing a $3mil medium by-pass jet with a $28mil
high bypass jet save money? Lower mortgage apyment of lower fuel bill, which
is better?

D. (answer to follow)



Doesn't everyone lease the planes (or powerplants) these days, or at least have some sort of power by the hour
performance based logistics maintenance program these days?

" Blueskies" wrote in message Doesn't everyone lease the planes (or
powerplants) these days, or at least have some sort of power by the hour
performance based logistics maintenance program these days?

In most jet airlines, fuel is 50% of the cost. One year ago, jet-A was
around $1.26/gal for my employer. Now it is just under $2.00/gal (not
considering hedges). Replacing an MD-80 with a B-737NG or an A-320 results
in 30% fuel savings. Even with the higher lease payments, my employer saves
$200,000.00 per airplane replaced in the first year.

It's a Catch-22 for the legacy carriers who are stuck paying high fuel costs
because they don't have the cash to update their fleet. They don't have the
cash to update because they have high fuel costs. Of the discount carriers
ringing up a profit, how many are flying high bypass engines and how many
are flying medium bypass engines? Everytime I see a Northwest DC-9, I wonder
how long before they file for bancruptcy (question recently answered- longer
than I expected).

Why did Boeing discontinue the B757? I'm not sure, but I do know that the
A-321 hauls nearly as many passengers and yet the A-321 has a MGTOW that is
60,000 pounds lower. It takes a lot of fuel to haul around an extra 60,000
pounds. What will the new B-787 weigh? Why did Airbus feel threatened enough
to counter with the launch of the A-350 program? It's about saving fuel.

As for leasing, there are many ways to structure a lease. Many times, large
shareholders will own an aircraft (though the paper trail may be long and
convoluted) and lease it to the airline, often at a sweetheart rate. With
this method, the shareholder makes money on it's investment in the airline
even if the airline doesn't make money.

Power by the hour contracts are available for both old and new engine
series. The difference is that the newer engine models have fewer
life-limited component times resulting in less down time. The same thing
applies to other components. Brake overhauls can be contracted for old and
new planes. The difference is that the old style steel brakes have more down
time, and man-hours required for replacing, than the new style carbon
brakes. Contract or not, someone has to pay the difference.

D.

"Larry Dighera" wrote in message In the event of an in flight electrical
failure disabling the
electronic control augmentation, it could get "interesting." What
does Airbus use to overcome that issue?

Airbus's first answer is that it has never happened.

If an engine generator drops offline, the other generator picks up the load.
The APU generator can pick-up the load if the second engine generator drops
offline. The ram air turbine powers a back-up generator if all 3 main
generators crap out. Even if the RAT doesn't deploy, the batteries provide
at least 25 minutes of electricity. The engines' FADEC units have their own
independent generators.

Augmentation may be the wrong word. It refers to the levels of protection
afforded to the flight envelope. As long as you have a generator or a
battery, you will have control. 'Complete electrical failure' is the wording
I believe you wanted.

Try flying a light twin without touching the yoke. You have throttles,
rudder, and elevator trim, but no elevator, ailerons, flaps, or instruments.
And the gear probably won't extend. The A-320 stalls like a C-172, lots of
buffet and drops straight ahead. With calm winds and a long runway, you can
make your dinner reservations at Nanno's.

The real danger is if you lose all 3 hydraulic systems.

D.

"Chris Kennedy" wrote in message
They don't. Everything is inputs to the redundant autopilot system;
stick and throttle are suggestions, not really commands.

This true when operating in normal law mode (99% of the time). However, when
degraded to direct law mode, the A-320 operates like a normal airplane. The
reboot is not because it can't fly, but because we like everything to work
so as to provide the safest flight we can (and we are lazy and don't want to
handfly a whole leg).

D. (it tunes it's own VORs)

On Sat, 17 Sep 2005 03:41:46 GMT, "Capt.Doug"
wrote in ::

"Larry Dighera" wrote in message In the event of an in flight electrical
failure disabling the
electronic control augmentation, it could get "interesting." What
does Airbus use to overcome that issue?

Airbus's first answer is that it has never happened.

That smacks of the argument used in assuring security against the
September 11, 2001 attacks. :-)

If an engine generator drops offline, the other generator picks up the load.
The APU generator can pick-up the load if the second engine generator drops
offline. The ram air turbine powers a back-up generator if all 3 main
generators crap out. Even if the RAT doesn't deploy, the batteries provide
at least 25 minutes of electricity. The engines' FADEC units have their own
independent generators.

At first glance, five levels of electrical power source redundancy
would seem safe in guarding against 'Complete electrical failure',
however there are other points of failure in electrically operated
systems. Each electrical circuit is fed through a circuit breaker.
How many circuit breakers are involved in the Airbus flight control
system? How many electrical buses?

Augmentation may be the wrong word. It refers to the levels of protection
afforded to the flight envelope. As long as you have a generator or a
battery, you will have control. 'Complete electrical failure' is the wording
I believe you wanted.

No, that is the phrase that describes the issue you addressed. I'm
more concerned about single points of failure.

If the circuit breaker (an electrical/mechanical device) feeding the
electrical bus supplying the flight control system were to
malfunction, regardless of power being available, the bus could be
de-energized, and no amount of available power would bring the flight
control system back into operation, unless you know of additional
redundancy designed in to the Airbus control system that you have not
yet discussed.

Try flying a light twin without touching the yoke. You have throttles,
rudder, and elevator trim, but no elevator, ailerons, flaps, or instruments.
And the gear probably won't extend.

I've not had that experience, but in a light single engine aircraft
with exclusively mechanical controls, its occupants would probably
walk away from the "landing." In the event that a mechanical
malfunction in its control system, it would only affect the control of
a single axis (like the Alaska flight that went down off the Ventura,
California coast five years ago :-(), not the entire 3-axis flight
control system. But Airbus products do have mechanical elevator trim,
IIRC, so in the event of the electrical portion of the flight control
system failing, there would still be some control of one (important)
axis.

The A-320 stalls like a C-172, lots of
buffet and drops straight ahead. With calm winds and a long runway, you can
make your dinner reservations at Nanno's.

So you're intimating that only the ailerons and elevator are
electrically operated?

The real danger is if you lose all 3 hydraulic systems.

Are you saying there are three hydraulic actuators, one from each
hydraulic system, attached to each control surface?