Why do Dassaults have 3 engines?
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900 EX for Excelent
CON-PILOT and 7xXx ... Never ment disrespect ...
I never tought that the difference between B and EX was so great ... love to get my hands on an EX or in that matter a 7X ...
Done about 3K on the B although I love it, it is a bit limited in my missions ... most of the time I have 12 to 14 pax. for the long legs (That does not help) ... Done KMCO to LFMN once (Ferry) Nice flight .. even got a lightning strike out of Florida ...
One thing I have to add to this thread is that even though this 731s are reliable, they ask for a lot of care, they are not the most durable engines but they have giveN me a non stop 3K hours of truble free flights.
As one of you said, if you don't like the Falcons is becauce you have NOT flown one ...
Keep it Safe..
I never tought that the difference between B and EX was so great ... love to get my hands on an EX or in that matter a 7X ...
Done about 3K on the B although I love it, it is a bit limited in my missions ... most of the time I have 12 to 14 pax. for the long legs (That does not help) ... Done KMCO to LFMN once (Ferry) Nice flight .. even got a lightning strike out of Florida ...
One thing I have to add to this thread is that even though this 731s are reliable, they ask for a lot of care, they are not the most durable engines but they have giveN me a non stop 3K hours of truble free flights.
As one of you said, if you don't like the Falcons is becauce you have NOT flown one ...
Keep it Safe..
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Originally Posted by galaxy flyer
If 2 engines weren't more efficient, the B777 wouldn't be the most popular plane for int'l airlines. There are no 3-engine airliners anymore and the A380 is certainly the last 4-engine design we'll see.
Dassault tried to claim that 2 was for "domestic" use and 3 was for overwater--worked until DA2000 customers wanted more range to go overwater.
GF
Dassault tried to claim that 2 was for "domestic" use and 3 was for overwater--worked until DA2000 customers wanted more range to go overwater.
GF
I remember reading that Airbus applied for some sort of trijet patent in the '00s.
Also, there may be some disadvantage to the trijet design when the plane uses wing-mounted outside engines. With biz trijets, all the engine systems are in the same place. In commercial applications, the center engine is kind of in the middle of nowhere. The hypothetical is for business jets.
If twinjets are so much more efficient, then I don't understand how the Falcon 7X uses 30% to 40% less fuel than its direct competitors. That would imply incredibly poor design jobs by Gulfstream and Bombardier.
No, it would imply that Gulfstream and Bombardier designed larger planes that are heavier, greater cabin volume and longer range--the whole combination being heavier and, yes, less efficient. A 900 grossed out weighs about what the BOW is for an XRS. Big difference.
The 900 has greater range than a 2000 because it was designed that way, not because three engines are more efficient.
GF
The 900 has greater range than a 2000 because it was designed that way, not because three engines are more efficient.
GF
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2 vs 3
The 2000EX and 900EX have almost the same airframe, and if we compare a 1000NM leg, the trip fuel, for the 2000 is 3915 lb vs 4150 lb in the 900. I would guss that most of the more fuel required by the 900, is because of the 2000 lb higher BOW.
Runway required for this leg would be 3370ft (2000) and 2795 (900).
Runway required for this leg would be 3370ft (2000) and 2795 (900).
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Its really just a European/USA-North America difference in design philosophy, just like cars! In Europe, everything is designed with a VERY sharp pencil, across on the other side of the pond..they build bombers
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right...Bear in mind that the purpose of this thread wasn't to prove wich aircraft design is the best (Glex,GV..ect ) versus the Dassault 3 engines concept but just to expose and to learn a little more about what was behind that choice !
As for the "Bombers" from the other side of the pound...we owe you big time ! but it's another old story..
As for the "Bombers" from the other side of the pound...we owe you big time ! but it's another old story..
Just to refute the bombers analogy a bit. The Challenger 600 that overran the runway on take-off at KTEB--it went thru a steel fence, crossed a street, hit a car, punched thru a commercial brick building-the passengers and crew opened the main cabin door and evacuated. Taxi out for a 24 departure, you can see the brick repair work.
Something to "bombers"
GF
Something to "bombers"
GF
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3 Engine Falcon
When the Falcon 50 was designed there were limited choices and none in the thrust range for a two-engine airplane of this weight allowing long range.
Second, at the time three engines were considered the standard for overwater operations; think 707, DC8, 747, L1011, DC10.
Third, operating in third world countries gave the crew the 'option' of ferrying the airplane out on two engines at light weight if one engine was inop.
Obviously in 2010 with engine reliability so high, three engines is not much of a selling feature unless one is only interested in having two spares.
In a Gulfstream II/III/IV is was much less likely to lose one Spey than two Garretts.
One can always swing a conversation to their direction.....
Second, at the time three engines were considered the standard for overwater operations; think 707, DC8, 747, L1011, DC10.
Third, operating in third world countries gave the crew the 'option' of ferrying the airplane out on two engines at light weight if one engine was inop.
Obviously in 2010 with engine reliability so high, three engines is not much of a selling feature unless one is only interested in having two spares.
In a Gulfstream II/III/IV is was much less likely to lose one Spey than two Garretts.
One can always swing a conversation to their direction.....
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No, it would imply that Gulfstream and Bombardier designed larger planes that are heavier, greater cabin volume and longer range--the whole combination being heavier and, yes, less efficient. A 900 grossed out weighs about what the BOW is for an XRS. Big difference.
The 900 has greater range than a 2000 because it was designed that way, not because three engines are more efficient.
GF
The 900 has greater range than a 2000 because it was designed that way, not because three engines are more efficient.
GF
My point is that if you do the math comparing the newest planes, the G650 has about a 12% higher thrust-rating to MTOW ratio than the 7X. So even being almost 60% heavier, with its 2 massive engine it has about 12% higher power to weight. Why can Dassault have less power and still perform? Because when you eliminate one engine from both, the 7X is left with a 10% higher thrust-rating to MTOW ratio than the G650.
So I'm thinking, can this phenomenon be key to a lot of the tradeoffs? For example, Gulfstreams are known for their low-sweep, no forward high lift device wings designed for climb performance AND ALSO engine out performance. They can stay in the air better with 50% of their power if they have a wing optimized for slightly slower speeds. However, obviously this costs them efficiency at normal cruise speed. The 7X, keeping 67% of its power with an engine out, with 10% better remaining power to weight than the G650, uses a more highly swept, faster wing. Is it possible that a reason that the Dassault wing can be more highly swept is because it doesn't need as much aerodynamic help from the wing in the case of an engine out?
These are the reasons that I'd really like to talk to a business jet engineer. 2 engines are inherently much more efficient than 3, but if the 2 engine plane has to produce more thrust, and it has to have a less efficient wing, and if it has to have more drag because an S-duct engine is more aerodynamic than any tailcone... then I can see how a 3 engine plane can be competitive.
Also, I know that there are many different design decisions that go toward Dassaults' great takeoff performance, but could smaller engines be part of it. One thing I know about cars is that smaller turbochargers spool up faster, and a turbocharger is just a form of turbine. Is it possible that smaller turbine engines on a plane spool up faster and start producing more of their thrust faster than larger engines? Could this have an effect on takeoff performance, or no?
Tuna HP
The answer is no, smaller engines are not faster to spool up; FAR 33 has standards that apply to all engines. In any case, spool up time, in this application won't change performance numbers.
Comparing Dassault and Gulfstream is not that easy. Dassault uses lots of high-lift devices that make the slow speed arena favorable to them-their speeds are probably about 15 knots lower than GLF at equivalent weights, as is Bombardier GLEX. The advantage of the 3-engine design is exactly as you say, loss of an engine is a 33% loss of power versus 50%. Wing design is pretty much independent of number of engines. GLEX, for example, has 35 degrees of sweep, high-lift devices and the same engines as the GLF with less sweep and conventional flaps. GLF operates about 15-20 knots faster in the runway performance, but field length is pretty close for the same mission. The GLEX would be about M.05 faster in cruise, but the GLF can do that at a bit higher fuel flow.
GF
The answer is no, smaller engines are not faster to spool up; FAR 33 has standards that apply to all engines. In any case, spool up time, in this application won't change performance numbers.
Comparing Dassault and Gulfstream is not that easy. Dassault uses lots of high-lift devices that make the slow speed arena favorable to them-their speeds are probably about 15 knots lower than GLF at equivalent weights, as is Bombardier GLEX. The advantage of the 3-engine design is exactly as you say, loss of an engine is a 33% loss of power versus 50%. Wing design is pretty much independent of number of engines. GLEX, for example, has 35 degrees of sweep, high-lift devices and the same engines as the GLF with less sweep and conventional flaps. GLF operates about 15-20 knots faster in the runway performance, but field length is pretty close for the same mission. The GLEX would be about M.05 faster in cruise, but the GLF can do that at a bit higher fuel flow.
GF
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When making "performance" comparisons, remember this...
I may have missed it here on this thread, but has anyone addressed the climb performance under normal conditions, or a given set of conditions, when comparing the Falcons vs. the Gulfstreams and Bombardier products? I have only a few flights under my belt in the 900EX to use as a comparison, and nearly all of my 7500 hours of PIC jet time is split between the entire Challenger series and the G-III and G-IV. It seems to me that the Falcons and Challengers cannot begin to compete with a Gulfstream at max takeoff weights when it comes to climb and initial cruise speed and altitude. I cannot remember a day when I couldn't go straight to FL410 as my initial cruise altitude, and do at least M.80 when I got there, even at ISA plus a lot (I have several hundred Atlantic and Pacific crossings for comparison). Those are numbers that mean something to me, especially when there is weather to deal with (summer thunderstorms across the southern US and parts of the Pacific rim are no fun to get around when they can top 65K). I just love those Rolls Royce engines! If you check the failure rate history of the engines on Gulfstreams, it is a fraction of what you will find on other makes. And I for one think a G-III, G-IV or G-V is sexier than a Falcon any day.
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I don't know how the Gulfstreams compare with the Falcon 3 holers on a engine out departure, 50% loss compared to 33%. I do know that I could retire to a life of luxury on the difference in purchase price, and or live in luxury on the difference in annual DOC's. I would love to fly a Gulstream, I think they are fantastic but I also love the Falcon.
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Originally Posted by captainmorgan888
The 2000EX and 900EX have almost the same airframe, and if we compare a 1000NM leg, the trip fuel, for the 2000 is 3915 lb vs 4150 lb in the 900. I would guss that most of the more fuel required by the 900, is because of the 2000 lb higher BOW.
Runway required for this leg would be 3370ft (2000) and 2795 (900).
Runway required for this leg would be 3370ft (2000) and 2795 (900).
Your 1000nm numbers show the 900EX using 6% more fuel.
-It is 1,500 or 2,000 lbs heavier
-has a longer cabin that should add some drag (housing 20% more cabin volume)
-14.5% higher MTOW (carries enough fuel to fly 20% farther)
-It also is an older plane using even older engines first sold in 1972. The PWC engines on the 2000 didn't come out until the early 1990s.
-900 has much lower runway reqs
Seems to me that this is a very favorable comparison for the 900. Especially when you consider than 1000nm is a short leg for either of these planes, and shorter legs should favor the twinjets because of their faster climb.
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It also is an older plane using even older engines first sold in 1972
Yet you have to see, what range you would expect once you have done your 1000nm leg without having to refuel...
