Diesel aircraft engines and are the light jets pushing out the twins?

Ernest Gann in "Fate is the Hunter" described one event in which he
lost nearly all power on 3 of 4 out of LGA once, and another time that
all 4 quit simultaneously with a load of passengers over the Pacific.
The first event was caused by the mechanics testing a new type of
spark plug, which they "unfortunately" had time to install on 3
engines. The second was a glitch in the fuel system.

This is off the subject of small turbines, and the original point was
the theme of sustaining vs. disruptive technologies.

ETOPS is a sustaining technology.

More than that, it's a methodology more than a technology. Most
shutdowns in flight on four engine airplanes were discretionary: a
variable was observed out of bounds and the crew elected to shut it
down because it seemed more likely that the engine might inflict
damage on itself. With ETOPS this is a big no-no because if an airline
has so many inflight shutdowns they lose their right to fly ETOPS or
it is restricted.

ETOPS engines are not more reliable physically. The maintenance
requirements are different to eliminate certain past issues, and
operators have a big incentive not to shut them down and not to fail
to maintain them so they need shutdown.

The real issue with ETOPS is that you have the issue of an aircraft
the size of a 777 which may have to complete a long segment on one
engine, descend, and maybe shoot one or more missed approaches. Maybe
onto a slick runway. That's a lot of asymetric thrust and reverse
thrust as well..

Sooner or later, the bottom line is, we are going to lose nearly four
hundred people in one whack in a 777. No one, myself included, wants
this, but there has never been a commercially marketed airliner made
in any quantity that hasn't eventually had a catastrophic total loss.
IF that crash was in any way perceivable as a consequence of its being
a twin rather than four engine crash, heads are going to roll. Boeing
will likely have a judgment on their hands that will make them wish
they'd built piston singles instead, the operator will be in big
trouble and there will be regulatory changes and possibly a new
Administrator.

Hi Ted,

ETOPS engines are not more reliable physically. The maintenance
requirements are different to eliminate certain past issues,

doesn't that make them more reliable, if certain issues, that might
lead to failure are eliminated? "Physically", all engines are reliable.
If everything works as designed, engines don't fail. Only if faults
occur in parts or systems, failures occur. Maintenance is all about
avoiding faults by regular checks or scheduled replacement.

and
operators have a big incentive not to shut them down and not to fail
to maintain them so they need shutdown.

Now that's certainly a point!

The real issue with ETOPS is that you have the issue of an aircraft
the size of a 777 which may have to complete a long segment on one
engine, descend, and maybe shoot one or more missed approaches. Maybe
onto a slick runway. That's a lot of asymetric thrust and reverse
thrust as well.

same as with a 4-engine plane loosing two. It's still a matter of how
likely this is to occur.

Sooner or later, the bottom line is, we are going to lose nearly
four
hundred people in one whack in a 777. No one, myself included, wants
this, but there has never been a commercially marketed airliner made
in any quantity that hasn't eventually had a catastrophic total loss.
IF that crash was in any way perceivable as a consequence of its
being
a twin rather than four engine crash, heads are going to roll. Boeing
will likely have a judgment on their hands that will make them wish
they'd built piston singles instead, the operator will be in big
trouble and there will be regulatory changes and possibly a new
Administrator.

You might well be right here, but that is an issue of the US legal
system rather than a technical/risk mathematics issue.

regards,
Friedrich

--
for personal email please remove "entfernen" from my adress

Sooner or later, the bottom line is, we are going to lose nearly four
hundred people in one whack in a 777. No one, myself included, wants
this, but there has never been a commercially marketed airliner made
in any quantity that hasn't eventually had a catastrophic total loss.
IF that crash was in any way perceivable as a consequence of its being
a twin rather than four engine crash, heads are going to roll. Boeing
will likely have a judgment on their hands that will make them wish
they'd built piston singles instead, the operator will be in big
trouble and there will be regulatory changes and possibly a new
Administrator.

I beg to differ... the 737, 757, and 767 are all twins. Some of them
have crashed. Some of the 767's are ETOPS qualified. No one has
blamed any of the crashes so far on ETOPS or the fact that they were
twins vs. tri or quad jets.

There have been plenty of four engine jetliners that have crashed as
well. An Israeli 747 crashed in the Netherlands when it lost two
engines on one side of the plane at the same time (both separated from
the wing, so the were REALLY lost).

ETOPS isn't an exotic or inherently risky concept. In fact, I believe
that the additional rigors of ETOPS certification actually make ETOPS
planes safer. If you lose two engines in a 747, you are going
swimming just the same as if you lose two engines in a 777. There was
a case of fuel-mismanagement on a 747 operated by [not to be name U.S.
carrier] on its way to Narita that ran two engines dry, and barely was
able to stretch its glide to reach the airport with the two remaining
engines. If they hadn't been as close to their destination as they
were, they would have ditched in the Pacific.

Dean

ETOPS isn't an exotic or inherently risky concept. In fact, I believe
that the additional rigors of ETOPS certification actually make ETOPS
planes safer. If you lose two engines in a 747, you are going
swimming just the same as if you lose two engines in a 777. There was
a case of fuel-mismanagement on a 747 operated by [not to be name U.S.
carrier] on its way to Narita that ran two engines dry, and barely was
able to stretch its glide to reach the airport with the two remaining
engines. If they hadn't been as close to their destination as they
were, they would have ditched in the Pacific.

First, a 747 at low fuel weight should be able to stay airborne
indefinitely (until the fuel runs out) on two engines. Also the 747
fuel system has transfer and crossfeed-they should have had time to
transfer over a lot of fuel, enough to relight the outboard at least.

ETOPS losing one engine is very much akin to a four engine jet
losoing two on the same side. Some of what ETOPS mandated should have
been made industry standard anyway-such as no one mechanic working on
all the engines before a revenue flight.

(Ted Azito) wrote in message . com...

ETOPS isn't an exotic or inherently risky concept. In fact, I believe
that the additional rigors of ETOPS certification actually make ETOPS
planes safer. If you lose two engines in a 747, you are going
swimming just the same as if you lose two engines in a 777. There was
a case of fuel-mismanagement on a 747 operated by [not to be name U.S.
carrier] on its way to Narita that ran two engines dry, and barely was
able to stretch its glide to reach the airport with the two remaining
engines. If they hadn't been as close to their destination as they
were, they would have ditched in the Pacific.

First, a 747 at low fuel weight should be able to stay airborne
indefinitely (until the fuel runs out) on two engines. Also the 747
fuel system has transfer and crossfeed-they should have had time to
transfer over a lot of fuel, enough to relight the outboard at least.

Not if they are both lost on the same side... thrust asymmetry is
much worse on a 747 in this situation due to the positioning of the
outboard engine. The 747 that ran its two engines dry ran them both
dry on the same side.


ETOPS losing one engine is very much akin to a four engine jet
losoing two on the same side. Some of what ETOPS mandated should have
been made industry standard anyway-such as no one mechanic working on
all the engines before a revenue flight.

Not exactly, the ETOPS engines are mounted fairly close to the
fuselage on twins to minimize the asymmetric thrust. Four engine jets
have their engines mounted farther out.

Getting back to the original point: the 777 is not more efficient
primarily because it is a twin.

The cost of the 777's twin engines is probably less than the 747's
four engines, but not very much less. The larger and higher bypass
engine is a continuing step in the sustaining progression, which is
that the bigger engine delivers more total "power by the dollar-hour",
but at less unit affordability. You can't buy a fractional engine: you
either do or do not own the engine.

Small turbine engines at affordable prices-a 250 hp (flatrated to FL
200) aircraft engine for at the absolute most the price of a midsize
car-is what GA needs. A small engine in that power class could be
built for that price at existing Lycoming volumes, but that would be
disruptive development.

(Lest you believe that turbines are inherently expensive to make,
take a good look at a modern truck turbocharger. CNC machining and
investment casting have reduced costs drastically, which has not been
reflected in aircraft small turbine pricing partly because they are
old designs but partly because the market is price-insensitive. I'm
convinced P&WC could sell PT6-class engines for well under fifty
thousand dollars if they had to.)