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SonicCruiser ETOPs/Cruise Height Curiosities

Wed Aug 08, 2001 4:43 am

I've been pondering a couple questions about the SonicCruiser that I haven't seen answered here yet, and was wondering if anyone had some good answers for them...

First, why is the SonicCruiser a twin engine design. If it's going to be a long range point to point craft, aren't most of those flights over-water, and won't ETOP's restrictions lengthen the routes it will have to take, undercutting it's speed advantages? Wouldn't it be better as a tri-engine design?

Secondly, Boeing has said it will fly higher in smoother air, at 41,000 feet. Don't almost all commercial jets have the capability of cruising at 41,000 feet or close to it (39,000 feet). I think a Gulfstream G-V cruises at 50,000 feet, and concorde at 60,000 feet. Given it's speed and performance, shouldn't the SonicCruiser be flying at 50-60,000 feet to minimize drag?

Or should it be cruising at lower altitudes when possible where the speed of sound is higher, allowing it to pickup some extra ground speed?
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RE: SonicCruiser ETOPs/Cruise Height Curiosities

Wed Aug 08, 2001 8:40 am

Just a thought..

ETOPS restrictions are defined in minutes away from a suitable landing airfield. Now, given the SC's speed, wouldn't that make the distance the aircraft can travel in 180 minutes greater than the distance a normal subsonic jetliner can go in the same period of time?
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RE: SonicCruiser ETOPs/Cruise Height Curiosities

Wed Aug 08, 2001 10:11 am

According to earlier Boeing numbers, the Sonic Cruiser will Curise at 47,000ft. Higher than most subsonic aircraft.

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RE: SonicCruiser ETOPs/Cruise Height Curiosities

Wed Aug 08, 2001 10:33 am

I'd suspect that ETOPS will not be much of an issue if and when the SC is built. Boeing will certainly want to have ETOPS 180 out of the box, it wouldn't surprise me to see ETOPS 207 or ETOPS 240 at the begining when this plane enters service arond 2010.
Stop drop and roll will not save you in hell. --- seen on a church marque in rural Virginia
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RE: SonicCruiser ETOPs/Cruise Height Curiosities

Wed Aug 08, 2001 10:46 am

The ETOPS rules are defining the flight-time under the conditions of one-engine-out (which of course is the reason for all this) and I think the SonicCruiser won’t travel much faster than other twins with only 50% power left. Therefore I wouldn’t expect a great advantage in the distance a handicapped SonicCruiser can cover in 180 minutes.

Anyway I share the opinion of AlsaskaMVP that Boeing could have opted for a three- or four-engine-design for an airliner that is intended for extreme long-haul point-to-point routes. In that case no current or future ETOPS rules would restrict its usability. The operating economics of three engines cannot be that critical compared to the anticipated increased fuel consumption of Mach 0.98-travel.

At least one more engine and keeping all promises and it would be the perfect airplane.  Smile/happy/getting dizzy

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RE: SonicCruiser ETOPs/Cruise Height Curiosities

Wed Aug 08, 2001 10:55 am

Good questions, AlaskaMVP, I'm curious too, but I'm not sure there's much to talk about at this preliminary a point of product announcement.

As the years go by and some design details get decided upon and tested, be more to chew on.

I don't think ETOPS will be much of a factor for it though. Not compared to to stuff the designers are gonna face like engine design and fuel efficiency thereof, and materials selection and testing. And optimum cruising altitude to an extent a function of engine design, amount of oxygen --limiting the max altitude for a given engine intake-- and stuff like that.
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RE: SonicCruiser ETOPs/Cruise Height Curiosities

Thu Aug 09, 2001 5:24 am

I realize it's a bit early to speculate, but I find SC design/operational issues fascinating. I can't wait until Boeing issues some more details....
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RE: SonicCruiser ETOPs/Cruise Height Curiosities

Thu Aug 09, 2001 6:46 am

I just found the following article, which some more details on the development.


AvWeek: Adding New Technology Favored for Sonic Cruiser

By Bruce A. Smith/Aviation Week & Space Technology
03-Aug-2001 2:33 PM U.S. EDT

SEATTLE -- Most airlines selected to help Boeing define the basic configuration of its Sonic Cruiser would like new technology applied to the design, even if it results in a little later service-entry date.

Boeing has said timing of the high-speed aircraft's operational availability would depend, in part, on how much new technology initial customers wanted to have included in the introductory model.

John Roundhill, vice president of marketing for the new aircraft at Boeing Commercial Airplanes, said that while airline input has varied during the course of the definition phase, potential customers generally would like the Sonic Cruiser to be as efficient an aircraft as possible.

Key drivers to the technology improvements sought by airlines tend to revolve around environmental issues, with some of the advances ultimately targeted for enhancements in areas such as fuel burn, engine emissions and noise levels.

"My guess would be, based on everything we are hearing, that we will incorporate a fair amount of advanced technology into the aircraft," Roundhill said.

"We are still providing customers with trade data, but that seems to be where we are headed."

In addition, most customer input has been focused on long-range applications of the design which would result in the aircraft being used primarily on international routes. However, interest remains among carriers in an aircraft that would be used on routes of only about 3,000 mi. and those typically flown by 747-400s.

Boeing expects to have the basics of the design -- such as range, speed, overall size and fuselage cross section -- in place by year-end. In the meantime, project officials continue to work on technical issues, conduct tests and select features to be included in the baseline configuration. Recent program activity includes:

-- Trade studies to determine relative positions of the landing gear and engine air inlets, which are under the wings. Foreign object damage (FOD) is one of the key criteria the company is considering in its Sonic Cruiser design because of concern that runway debris could be kicked up by the landing gear. Options under review include shielding of landing gear wheels and adjusting the location of the main gear.

-- Because of the design's canards and long wing strakes, there is limited space along the fuselage for access by service vehicles. Primary galley service is through door No.2 forward of the wing, but Boeing is evaluating ways of servicing an aft galley so that carts won't have to move through the cabin. The baseline design has a system that lifts carts up to the aft galley from beneath the aircraft.

-- To provide increased clearance and avoid possible contact by a passenger boarding ramp or service vehicle, Boeing is considering placing the canard's full-moving surface nose-down while an aircraft is parked at a gate. The current design calls for independent elevators on the canards that are coupled with elevators between the engines.

-- The baseline configuration is about half-way through an initial cycle of wind tunnel testing using a 2-3% scale model. The program will include evaluating various tail sizes and wing geometries to validate computational fluid dynamics tools. Overall testing is expected to run for at least a few years as engineers refine the design.

-- Consideration also has been given to flying a manned or unmanned Sonic Cruiser design in an aircraft larger than could be tested in a wind tunnel. A decision on whether to conduct such a test series is not expected to be made until much later in the program.

-- The current baseline includes an all-composite wing that will be evaluated along with advanced metal structures during engineering trade studies.

-- Boeing is targeting its design to meet QC2 noise levels on takeoff and to better that standard on approach and landing.

The question for Boeing, Roundhill said, is determining what the range of the initial aircraft should be, the range of a follow-on model, and the timing for introducing a second model. "It's the classic issue of how you develop the family."

While the baseline configuration is a very long-range aircraft, he said, there is some customer interest in a model that would have about the same range capability as 747-400 and 777-300 Extended Range aircraft. That capability would cover a large number of airline requirements, he added, including the U.S. East Coast to Japan, the U.S. West Coast to Europe, and Europe to most of Southeast Asia and Tokyo.

There also is interest in an aircraft with a U.S. transcontinental range capability, since it would shave about an hour off such flights and could allow for an additional cycle per day.

The baseline of the high-speed model calls for an aircraft that could carry more than 200 passengers in excess of 9,000 naut. mi. at a 45,000-50,000-ft. maximum altitude. Cruise speed would be Mach 0.95-0.98

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