Black boxes in autos?

The O'Hare accident (after which not ONE more DC-10 was ever sold!)
happened way before Sioux City. Again, you could argue it was "human
error" because American Airlines was hanging engines on the pylons with
a forklift, which over-stressed one of the 3 bolts that held the engine,
which in turn led to structural failure of the pylon months (or maybe
years) down the road. But it WAS a structural failure, and you can abuse
most systems on a car much worse than that without causing a failure.

The point of the debate is that airframes are always stressed much
closer to their ultimate limits than cars are because they just can't
carry any excess weight, and that's just a simple fact.


However, it did have at least one major design flaw that

True. But the DC-10 had a hell of a lot more problems than just that one
system. It was a maintenance pig, and the MD-11 was worse. Those two
airplanes killed Douglas, no question. Even the wild success of the
DC9-80 (aka MD-80) couldn't help the company dig out of the hole the
DC-10/MD-11 fiascos created.

 

Nope - I was referring to the McDonnell Douglas DC-10, one of which was
an American Airlines plane that crashed on attempted takeoff out of
O'Hare from - engione pylon bulkhead-to-wing failure due to maintenance
procedure shortcut not authorized by McDonnel Douglas though they
suffered financial devastation over the affair.

Bill Putney
(to reply by e-mail, replace the last letter of the alphabet in my
address with "x")

 

That is hilarious. I've experienced structural failure in an automobile
and witnessed several structural failures. The difference is that
nearly any significant failure of an airplane makes the national news,
whereas rarely does an automobile accident make the national news. The
fact that you aren't aware of structural failures of cars, doesn't mean
they don't exist.

Did the tankers have FDRs onboard?

Must be your definition of many is the same as your definition of much.
Very few small private planes are pressurized. The P210 is one, but
very few of those were built. There are a few piston twins that are
pressurized, but again, not many of those are privately owned, unless
you consider a small business to be a private owner. Maybe you consider
bizjets to be small private planes.

Well, I don't consider bizjets to be a reasonable comparison to
passenger cars as few are truly privately owned and operated. Most are
owned and operated by businesses.

It is only counter productive if the reduction unit weight offsets the
performance and efficiency gain from a high RPM engine. A number of
WWII airplanes used higher RPM engines with reduction drives. They are
also becoming more popular in the homebuilt market. I suspect it is
only a matter of time before Honda or Toyota introduce a high
performance, high RPM piston engine with a decent reduction drive. Then
again, the piston engine market is so miniscule that they may never do
so, especially after the Porsche/Mooney experience.

Except that the turbine has almost no role yet in small airplanes. A
number of 4-6 pax jets are on the drawing board or flying as proof of
concept prototypes, but even the cheapest of those are far out of reach
of the average GA pilot. And turbine efficiency below 25,000 feet is
pretty poor.


Matt

 

A high-RPM engine is not necessarily efficient. In fact its harder to
make a high-RPM engine as efficient as a slower-turning engine with
relatively low compression and a fair amount of turbocharger boost.

You mean "high RPM" as in a Rolls Royce Merlin that ran a whopping 3000
RPM and had a reduction gear so it could swing a 14-foot prop? Or "high
RPM" as in a Napier Sabre that ran maybe 4500 (and was so unreliable
that not a single running example remains)? If 4000 RPM is "high" then I
agree with you- but that's nowhere near the point that 4 valves per
cylinder makes sense.

It'll never happen. The aircraft reciprocating engine has been through a
very, very long evolutionary cycle, and everything except air-cooled /
low RPM engines has ultimately proven to be a failure in that
environment except for niche applications. Nothing's going to change that.

 

Most aircraft piston engines are redlined at or near 2,700 rpm for reasons
having to do with the prop more than the engine. Of course a constant speed
prop is more efficient because you can choose between a faster prop speed
(with the engine developing more power) for takeoff/go-around situations and a
lower speed for efficient (and quieter) cruise settings. According to the
guys at Lycoming, 2,700 is too slow for the engine to develop its potential
max power, but it is a compromise for the prop efficiency, load, and noise.

A reduction gear allows both engine and prop to operate at their most
efficient speeds simultaneously, but it presents several challenges. First it
adds expense and weight, and both are very undesirable--particularly weight.
The cowling would likely need to be extended, changing the W&B. It also is
another complication in a design where simplicity is greatly favored.
Finally, a sharp reduction in power (e.g. pulling the black or even blue
handle back sharply) can cause problems with the reduction gear system and
engine counterweights. In World War II, engineers found that reduction gears
and very high performance engines were a very desirable combination that was
favored over its drawbacks, but they are fairly rare on today's designs.

On the other hand, reduction gears are certainly used for turboprop engines.

 

..

Yeah, but that's a COMPLETELY different loading profile than a piston
engine. With a turbine, there's no torque pulsation as the cylinders
fire, and far less "reverse" torque when power is reduced. Big piston
engines routinely beat the tar out of their reduction gears- even the
ones with planetary reduction gears like the big radials use.

 

All true, and more importantly turbines tend to operate at speeds that would be
considered exotic for recips, such as 30,000 rpm. Needless to say, it would be
very problematic to have a propeller operate at these speeds, and even if you
could design one to withstand the force, efficiency would be terrible and the
noise prohibitive. Hence the need for a reduction gear to a more respectable
2,200 rpm.

 

Most of what you suggest is far too sensible to ever be implemented...

DAS