tuna hp

The Dassaults are also very interesting to me. Its pretty interesting that they're the only trijets still in production, and yet they are so popular, so I always try to read about them.

In response to these questions, my understanding is that the Dassault isn't necessarily safer overall than the Gulfstream. There are safety performance tradeoffs. The Gulfs can run all their systems off one engine, and then they can run almost everything off the APU. And then even without the APU, there are the multiple redundant hydraulic accumulators, ram air turbines, batteries, etc, to be able to run enough systems to land the thing. Plus the Gulfstream is the bigger plane with better thrust (with all engines) so it should be able to power through weather better.

As far as ETOPS: yes for the planes that are operated as charter, but I don't think that private operators have to comply with ETOPS. They can do whatever they want.

QuietSpike

All a myth... all unsupported... all of Dasso's marketing propaganda... and you bought it all apparently...

With today's technology and reliability-- not to mention the power of modern twin engine long range bizjets and airliners, the three-hole thing is a MYTH.

For example-- A G150 can fly just as far on one engine as they can on two... with 2 TFE731-40AR's. The competitor from Falcon? The Falcon 50, which is no longer made...

You think a falcon 900 with one engine out can stay "in the flight levels and not descend"? Especially in higher ISA temps over the atlantic? Even a 7x would not be able to just keep cruising along like nothing happened with one engine out. You would have to descend in any scenario. If it is a twin, you would definitely crank the APU up-- at a staggering 100-200 lbs an hour (sarcastic)-- and with little to no effect on speed limit (on any of the twins I have flown).

Dasso used to also claim that winglets were "a product of poor aerodynamic design" when comparing their models to Gulfstreams... now every falcon has a retro-fit kit for winglets (including now the 50), and every new model has winglets... Just as with their winglet myth, the 3-hole myth is kaboomed outta here.

ETOPS for private aircraft in the US is not enforced, however Gulfstream ensures that it's product line can meet or exceed the specifications in ETOPS. I am sure other manufacturers do as well (if not all of them), that is just the one I know about.

geosynchronous

Unsupported?

There is definitely no "myth" on the operating economics...

Annual Budget (no depreciation)

Falcon 7X/ G550

Utilization (nm.) 175,000/ 175,000
Utilization (hours) 407/ 413
Variable Cost $1,126,832/ $1,363,016
Fixed Cost $717,506/ $827,531
Total Cost $1,844,338/ $2,190,546
Per nm $10.54/ $12.52
Per hour $4,532/ $5,304
Per seat mile $0.88 / $0.70
Typical price/1000 (mil.) $47,400/ $48,995

Source: Conklin & deDecker Aircraft Cost Evaluator 2009 vol. 1 v. 4.8.0

IMHO, Dassault marketing is brilliant. They have marketed an aircraft that sells for $1,595,000 less; and in terms of an annual operating budget, an owner can utilize the 7X for 16% less than a G550.

All with an extra engine...why not market triple redundancy for less money?

QuietSpike

Comparing a 7x and a 550 is not a "true" comparison!! I could compare a G150 to a Falcon 2000 and it would kick the crud out of it from an operating budget!!

The fact that you are trying to discounts your credibility!!

I never said that dasso's marketing was poor!! I said the MYTH of 3 being better than 2 is just that.. a myth! Any pilot that buys that myth needs to do some research!!

You may "breathe easier" before you cross the atlantic with 3 engines (completely in your head, btw), but you will also be waiting for 3 engine starts for something to fail... 3 times more likely to have something break, and also statistically 3 times more likely to have an engine failure over a 2 engine aircraft.

geosynchronous

Let's not throw out a "straw-man" to make an argument. If you have the data that can be referenced, please use it. Otherwise, subjectively validated personal insight is blatantly anecdotal. On that point, how can the comparison between two bellwether intercontinental business jets not be accurate?

You referred to "unsupported marketing propaganda" from Dassault. The categories of Product, Place, Promotion and Price are all positive. If you do not like the credibility of the data that was referenced from Conklin and deDecker, then you should direct your displeasure towards them.

Please don't kill the messenger.

QuietSpike

Ugh... there is no "debate" here...

Don't you dare tell people on here that they are throwing out "personal insight" and trying to pass it as fact. You have no idea what people's backgrounds are in here, including mine. You think it is an "argument", which again makes me think you are taking this too personally.

Second, I actually said dasso's marketing is quite good!! THEY STILL HAVE YOU CONVINCED!

Third, 2 engines are always better than 3. You can say it is my opinion all you want, but it is a fact.

Fourth, and once again... the comparison between the 7x and the 550 is not a TRUE comparison because the 550 is A LOT more aircraft than the 7x... more aircraft=more $. ONCE AGAIN-- comparing a 7x and a 550 is like comparing a G150 and a 2000ex and saying the G150 is better because it is more cost efficient... completely different aircraft...

Clear?

geosynchronous

Please compare another aircraft and supply supporting evidence if the G550 is not congruent with your expectations.

Research and data establishes the dichotomies of debates (perceived or not), not the interrogative of: "Clear?"

"You can say it is my opinion all you want, but it is a fact."

Subjective.

tuna hp

Not true. Dassault is very much technically right. Extra wingspan is still more efficient than a winglet of the same length. There's a reason why long range Boeings don't have winglets. For the older Dassaults with the winglet retrofit kits, its a matter of loading. Those winglets are what the wing could structurally handle. Presumably a wing extension would have been more efficient but would have been too stressful on the wing. They are a compromise. Same thing with the 7X, actually. The winglets got added to the 7X design when Dassault changed their design goal from 5,700nm to 5,950nm, including an increase in MTOW, while they left their wing design mostly frozen. They could have made a more efficient plane if they went back and did a more substantial redesign to the wing to increase its length. Instead of spending the money to do that, they added winglets. Again, a compromise on total performance.

So maybe you could argue that winglets have proven to be a good structural / performance tradeoff, but even then you'd have to figure out why Boeing, a very aggressive winglet implementer, leaves them off of their long range 777s, 787s, and 747s.

Extra wingspan > winglets is still definitely the case

I don't know why QuietSpike is so defensive, but I do agree with him as far as saying that Dassault isn't necessarily safer than Gulfstream. Maybe has something to do with the fact that he is named after a Gulfstream research program .

The deal is that you're thinking, "oh the Dassault is safer because it can lose one engine and still have 67% of its power, and it can lose 2 engines and still have power." Well yeah and thats part of the safety tradeoff, but these turbofan engines are EXTREMELY reliable. Chance of failure of any one engine is something like 2% per 1000 flight hours. So most of the time you're going to have all your engines, and in that case the Gulfstream is going to have significantly better thrust and be able to power through dangerous situations better. Also, since the Gulfstream has much higher thrust to weight with all its engines, the Dassault's thrust to weight advantage with an engine out is relatively modest. Its not the difference between 50% and 67%. The Gulfstream has almost 20% more thrust to weight than the Dassault so with an engine out the comparison is something like 60% for the Gulfstream vs 67% for the Dassault, if that makes sense (basing all engine thrust at 120% for the gulfstream, 100% for the Dassault).

Either plane has all the redundancies that they need to be able to run all the systems with an engine out. In fact, before the 7X's improved systems, Gulfstreams were known for having better redundancies than Dassaults. Either plane be flown with all power out.

Also, engines aren't the only consideration for engine out performance. The wing is a huge factor. If the Dassault wing is slightly more optimized for high speed flight than the Gulfstream's (as it technically could be since it uses high lift devices more aggressively), then that could be the difference between the Dassault and Gulfstream's with engine out power. The Dassault would have a little more thrust, but the Gulfstream's wing would be a little more suitable to the lower speed flight that you'd be doing with an engine out. I'm not saying that this is definite, I'm just trying to convey the true safety difference between 2 engines and 3: not necessarily anything.

As far as efficiency, yes it is cheaper to run and uses less fuel. It also has about 10% less cabin volume than the G550 and can't fly quite as long, and is a newer design. The Dassault is more fuel efficient because it is so much lighter. BOW of 35,000 lbs vs 49,000 lb in the Gulfstream. Thats a huge difference, and yet the fuel savings isn't that huge. This is the way that Dassault gets better fuel efficiency while having 3 engines: their planes are MUCH lighter. 2 engines would have been more fuel efficient than 3. The dominant factor in choosing 3 engines is engine availability. There simply aren't modern and efficient engines available in the thrust class that would be needed to power the 7X. So Dassault figures that they can build the plane the 3 PW+C engines which are very popular and considered safe and efficient, and they'll still get better fuel economy than the competition by virtue of their plane being 30% lighter than the competition.

There are obviously a lot of tradeoffs 2 engines vs 3. However, overall, from an engineering standpoint, 2 engines is overall better. Like I said, its a matter of engine availability. Back in the day (the 1960s) all the purpose built business jets were small and relatively short range. The engines built for them offered maybe 3,000 or 4,000 lb of thrust. They were considered to be less technologically advanced and less efficient then airliner engines of the day, and also were relatively expensive to buy and service. So Gulfstream innovates by just saying, "we're going to build our plane around low end commercial airliner engines, which have much higher economies of scale and are better developed, and we're going to be able to give people much more airplane at a relatively good value". Then Dassault responds with the Falcon 50 by saying, "we're going to actually put some engineering into this problem and create an efficient S-Duct trijet so that we can give people the plane and range that they need at a much lower price than the Gulfstream".

And thats where they still are today. However, I predict that there will not be any more new Dassault trijet designs. They are over after the 7X. Every single engine make is currently working on engines in the current 10,000lb to 13,000lb gap where there are no good engines available. Without a gap between where efficient purposebuilt business jet engines end and where efficient commercial airliner engines begin, there's zero reason for trijets.

geosynchronous

Tuna hp,

Thank you for your professional, lucid, and data laden insight. In the end, macroeconomics, mission, and marketing will be the final arbiters to the customer.

Life-cycle costing is a consideration as well. I was surprised to see that the 7x only requires 0.70 maintenance hours per flight hour compared to the G550's 1.53 maintenance hours per flight hour. Engine restoration costs are budgeted at $513 per hour on the 7X vs. $622 per hour on the G550. This is on top of the leading fuel efficiency from the 7X.

All of this seems counter intuitive...you can operate three engines on less fuel, and you can complete HSI/MPI/overhaul on three P&W 307's for less than two BR 710's. Again, this data is according to Conklin & deDecker's Aircraft Cost Evaluator 2009 vol. 1.

From the operational and budgeting perspective, the 7X does have it's nose in front; but I would be happy to operate either one.

tuna hp

When you think about it, its not really counter intuitive. The BR 710s are much bigger engines. They're making 60% more max thrust. So they use 20% more fuel and have 10% higher maintenance cost? Big deal, they're providing a higher thrust/weight ratio to an airplane that weighs 30% more. The BR710s probably have much better "thrust specific fuel consumption" than the PWC307s if they are only using 20% more fuel.

Still, it is amazing that the 7X weighs 30% less than the G550. Its smaller, but not that much smaller. They really build a good airplane.