Oh, Your Private Jet Is Just Subsonic?

zerogeewhiz writes "Found this article here at The Sydney Morning Herald . It seems that Bill and his mates need to move a bit quicker these days and for a cool US$80 million, you too can overtake the Concorde on a dash to Harrods for dinner. As described in the article, the main complaint about Concorde is that it can only fly supersonic over water and creates those nasty sonic booms that punch holes in buildings and shatter windows. They reckon they can get rid of these waves by making the plane longer. These are gonna be fast but hideous. 737-700s are suddenly passe as a corporate jet..."

Comments

Why the Sydney morning herald?

[Anonymous Coward]

The original Telegraph article is much longer and talks about the economics of production, and other developments in the fast-plane industry.

Newscientist Article

[null-loop]

There's a very cool article over at newscientist.com about this (http://archive.newscientist.com/archive.jsp?id=23 044700 free reg required), I read the print version of it. They've got a number of technologies they want to bring to supersonic travel, lengthening the plane being just one of them.

Re:"Bill and his mates"?

[b0r1s]

the article says A$160m , whereas the description says US$80m ... not all dollars were created equal.

Sure maybe you've heard a sonic boom....

[moniker_21]

but have you ever seen one? Check out this image I found a little while back.
(http://antwrp.gsfc.nasa.gov/apod/ap010221.html for the concerned web surfer)

When I read stuff like this, I can't help but wonder how long it's going to be before we'll all travel at super-sonic speeds for our presonal excursions, not just the ultra-rich.

Re:Extending Length to PREVENT Sonic Booms?

[G-funk]

Read the article, the story poster got it wrong, they're elongating the front and the eng of the plane, ie stretching them out so the angle isn't so great, not making the plane longer. They're not actually trying to say they can prevent sonic boom, afaik that's not possible (hey prove me wrong), they just want to controll it a bit so it's not so damaging to ears / buildings / windows / fine crystal wine glasses

About private jet economics and lifestyle

[daviddennis]

I seem to remember Bill flew in Coach class until his well-known appearance made that a non-starter, so I don't think Bill's that great a candidate.

Larry Ellison, on the other hand, will buy the first one available, the microsecond it comes up. And Warren Buffet will buy a few for his Executive Jet fleet.

You can charter a Gulfstream V for $8,500 per flight hour, which means a transcontinental flight would cost about $ 38,000. Skyjet.com reports round trip charters on an IV at $60,000 for the same flight. Ownership is, of course, mind-bendingly expensive; a Gulfstream V is in the $45 million range, and the Citation X (fastest bizjet around, but less luxurious and with half the passenger capacity) is $18m. You also need a full-time pilot and copilot, together with very expensive maintenance, all of which amounts to an overhead of tens of thousands of dollars a month.

After being squeezed in like a sausage in the USAIR tourist class cabin, I can very much see the appeal of having your own jet. I'm sure that if I was as rich as Bill or Larry, a jet would be one of the first things I'd get. Bear in mind that the Gulfstream has a top speed of Mach .80 and you can get up to Mac .93 on a Cessna Citation X. So it might not be worth the extra money to go supersonic unless you're doubling or tripling the speed of sound (as you do with the Concorde). The long and thin design also might not be as comfortable as the Gulfstream.

The aforementioned Citation X is about 100 knots (or 25%) faster than a typical commercial flight, and you can arrive at a general aviation airport about 15 minutes before takeoff. Since general aviation airports are most likely a lot closer to you than commercial ones, you can save literally hours by just getting there in ten minutes and taking off almost immediately instead of taking an hour to get to the airport and taking off an hour later. This speed and flexibility is the jet's main advantage compared to, say, simply buying a first-class ticket on a scheduled airline.

In other words, if your time is worth a lot, you probably want a jet. And if you can fill it to capacity, it's not that much more expensive than first-class airfare. A Gulfstream IV can fit 19 people; first-class airfare coast to coast is about $3,068 for a non-stop flight. So if you're paying $60,000 for your round trip flight, you're paying $3,157 per person instead of $ 3,068 for first class; not too shabby.

(I spent quite a bit of time flying with a friend who owned a small propeller plane, so I can attest first-hand to the ease and convenience of general aviation airports. Sadly, I have yet to fly on a private jet).

D

Re:About private jet economics and lifestyle

[warmenhoven]

The long and thin design also might not be as comfortable as the Gulfstream.

Er. The Gulfstream V is a Gulfstream IV with an extended fuselage. The Gulfstream IV is somewhat narrow, and they haven't widened it because they want to keep the larger windows. (And when I say larger, I mean larger; the windows are ovular and about 2 to 2.5 times the size of the normal ones you see on commercial jets.)

The larger windows are part of an old series of planes with the FAA used to allow but have since grandfathered. You can't use the larger windows on new planes unless if you're using the exact same fuselage as was previously allowed; extending the fuselage was allowed, however, hence the Gulfstream V, which has a larger capacity and I think also more powerful engines, but is just as narrow as a Gulfstream IV. But what a view out of those windows; when you're cruising at 6-12 thousand feet over the coastline of the pacific, it's absolutely gorgeous.

There's other advantages to owning a private jet, in addition to the time advantage, but money isn't one of them. Not having to deal with all the other passengers is a big one. Having your own private movie system, complete with DVD players and VCRs and screens for each seat, is a nice perk. Being able to see flight information, like how high you are, what your ground speed is, and ETA is especially nice. On-board private fax, modem, ethernet, A/C outlets, etc. etc. But like I said, you won't be saving money by having your own jet, no matter how much you travel. Feul, landing fees, storage, maintenance, crew, all add up. Not to mention the millions that you pay just to own the jet. But fortunately, most private jet manufacturers artificially inflate the price over the years, to create inflation. With light to moderate use you'll get most of the cost of the jet back when you sell it, assuming you've paid for regular maintenance, of course.

Most private vehicles tend to be bad investments unless if you're using them to sell rides (e.g. busses, taxis, commercial airlines, trains, etc.). It's much more economical to go commercial than to buy a private jet, no matter how much or how little you use it (similarly, it's much more economical to ride the bus than to own a car). But the time savings and comfort level are phenomenal.

The regulation on sonic booms

[mr_death]

The government takes a dim view of sonic booms over the US land mass.

http://www.access.gpo.gov/nara/cfr/cfrhtml_00/Ti tl e_14/14cfr91_00.html

91.817 Civil aircraft sonic boom.

(a) No person may operate a civil aircraft in the United States at a true flight Mach number greater than 1 except in compliance with conditions and limitations in an authorization to exceed Mach 1 issued to the operator under appendix B of this part.

(b) In addition, no person may operate a civil aircraft for which the maximum operating limit speed MM0 exceeds a Mach number of 1, to or from an airport in the United States, unless --

(1) Information available to the flight crew includes flight limitations that ensure that flights entering or leaving the United States will not cause a sonic boom to reach the surface within the United States; and

(2) The operator complies with the flight limitations prescribed in paragraph (b)(1) of this section or complies with conditions and limitations in an authorization to exceed Mach 1 issued under appendix B of this part. (Approved by the Office of Management and Budget under control number 2120-0005)

Re:Extending Length to PREVENT Sonic Booms?

[costas]

Short lesson on high-speed aerodynamics follows:

* The "intensity" (read: energy) of a boom is proportional (roughly) to the speed of the aircraft and the angle of attack of the wing or fuselage.
* To lower the energy wasted in a sonic boom, you can either go slower (neah...) or lower the angle of attack. For a wing, this is kinda easy: either sweep it back (notice a how much further back a fighter's wings are than an airliner's?) or make it thinner (so that the cross-sectional angle of attack, so to speak, is less).
* For a fuselage it gets trickier: a fighter need only fit one person, and you can extend the nose long enough to lower the leading angle of attack. And you don't care about traling shocks or really shocks at all, because you're in a fighter. You're supposed to terrify people.
* But for a commercial jet, you will have to take care of both ends of the fuselage, and the only way is to make them longer, and have them taper out smoother. Look at the Concorde's absurdly long nose (so long, it has to be pivoted so that the pilots can see the runway at take-offs and landings) and its thin tail. Now, you know why they're there.

Supersonic business jets have always been possible. However, new, more efficient engines and cheaper high performance materials are only now making them affordable (well, relatively at least :-)...

Learn more

[Blackjax]

This article had an annoying lack of details. These stories have more information on why this is being explored now:

aviationnow
and
savannahmorningnews

Re:B-52H Avionics (or lack thereof)

[wufpak]

The B-52H [bombnav.org] does have a cool looking CRT in it, but we are NOT talking glass cockpit here. All of the instruments are conventional dials (and, with 8 engines, that's a lot of dials). The CRTs are merely used to see outside.

Of course, seeing outside the aircraft is pretty important, too. Especially when you consider that, when these aircraft take off in a nuclear scenario, all the cockpit windows are covered with heavy (and opaque) thermal curtains. The only way the crew can see out is by looking at the CRTs.

For those who might be curious, the B-52H has two cameras mounted just below the nose: an infrared camera, and a visible-light camera. The view from those cameras is displayed on the cockpit CRTs, along with radar-derived terrain-avoidance data. Very handy for skimming the ground at night over hostile territory, with intermittent thermonuclear detonations occuring in the middle distance ...

Now, for a truly cool-looking glass cockpit, check out the B2. Yours for only $1,999,999,999.95 [Prices are MSRP including delivery, plus any options. Your final price may vary, contact your dealer.]

Re:Concorde Avionics (or lack thereof)

[Remote]

People's lives are at stake with the equipment in an aircraft, so you don't want to upgrade simply to make everything look cool.

But you still want to upgrade. Reducing pilot stress is one main factor in improving safety and those cockpit's from the 60's and 70's suck. You should see the cockpit of the infamous Comet, pity I don't have a link... Modern avionics are just as reliable as old dials, but pilots don't like the feel of not having control. I used to fly airplanes (ok, Piper Cherokees) and if I could have a dial showing me tire temperature or rudder angle I'd surely want one, yet usefulness would be highly questionable.

The Concorde is a weird beast, and most things about that airplane are are different. Let me give you two examples:

Cruise flight in a modern airliner is boring. You just supervise a few systems and sip your coffee (or actually sleep, as many pilots acknowledge. Some other things they won't acknowledge...). Not in a Concorde. That airplane burns lots of fuel considering its size, which means weight and CG change considerably during a trip. The flight engineer has to monitor the fuel in the many tanks and transfer it from here to there to maintain the CG where it's supposed to be, which also depends on how the plane is loaded in each trip. Lots of calculations, lots of monitoring. Also, the lighter the airplane, the highest it will fly at optimum fuel consumption. In normal jet aviation you're given a flight level and during the trip you are tipically allowed to switch to a higher level two or three times. The Concorde flies high, above 40.000 ft, where airspace is not controlled, so the pilot can gradually increase altitude during the trip. Actually one *has* to, if consumption is to be kept to the minimum. These are two tasks that should be handled by computers in my opinion, drawing attention from the crew only if something goes out of pre-established parameters.

Warning about private jets

[Anonymous Coward]

Among the different classes of aircraft,
private jets (including corporate) have one of
the worst accident rates.

Re:Extending Length to PREVENT Sonic Booms?

[SysKoll]

There is actually a way to soften the sonic boom by lenghtnening the plane.

What makes a sharp sonic boom is the dissipation of a lot of energy over a small distance. You can't do much to lower the energy of a plane's shockwave when it reaches Mach 1, but you can expand the area over which that energy will be concentrated. This is done by lenghtening the cone-shaped high-pressure shockwave that surrounds the plane.

This way, the shockwave's pressure gradient is spread over a longer surface (roughly a cone starting from the tip of the plane), and thus, with the same pressure difference over a bigger distance, the gradient is lower.

The sonic boom's enery is the same, but since it's spread over a longer distance and hence a longer time, it gives less instantaneous power. So you have a flattened pulse that is theoretically muffled, instead of a sharp spike. (If you want to visualize the concept, burn a candle, then explode a hand grenade. See, the total energy was roughly the same, but the grenade produced it in a sharp spike.)

The resulting experimental plane looks like the old supersonic fighters of the 60's, with a cone tip that looks way too long for modern standards.

There was an article about this in Aviation Week but their web site is subscribers only.

-- SysKoll