Gulfstream and their wing

[stilton]

From the GII to the -650 they have stuck with a large, lightly loaded wing with no slats.


No question they build a great aircraft but, in every class it competes in it does burn quite a bit more than the competition.


Surely a smaller, more highly loaded wing with slats would provide better field performance, lower drag and better fuel burn ?

[envoy]

Well... I guess the fact that there have been a succession of marques from GII through to G650 suggests that the customers are pretty happy. Notwithstanding the aerodynamic questions you raise, that would seem the most important thing when it comes to measuring the success of a brand.

IMHO, any wing/airframe/engine combination needs to have a focus - if you try to do too much with one aircraft you run the risk of creating a jack of all trades, but master of none. Perhaps there have been tradeoffs to ensure performance in particular areas, at the expense of others.

Who knows. Maybe the -750 will have leading edge slats, or some other design feature previously unheard of on Gulfstreams. No doubt it will have 9 cabin windows so large that pax will be freaked out by the fishbowl view in the cruise.

I can remember a time when Dassault sold Falcons without winglets because (so they said) their wings were better designed, and didn't need them. Viva change and innovation...

[tuna hp]

I completely agree with you that their wing seems outdated and unoptimized, which is amazing when you consider that they actually don't use much more fuel than their competitors. They burn less fuel than the globals, if I remember correctly, and they only burn a little more fuel than Falcons and way less than you'd expect considering that they weigh ~50% more than comparable falcons.

[FLEXJET]

Not having slats not only eliminates weight, but also a few pages in the QRH and MMEL.
Also the G650 wing has a 36° sweep, a much higher value than the 550's.

[galaxy flyer]

They have also had several in ground effect stalls including the last fatal one. Highly swept wings should have slats to control the boundary layer, provide a larger usable range of AoA and better stall characteristics, not least reducing leading edge stalls.

GF

[Mach Tuck]

Others marvel at the great versatility of the G550 wing without resort to any bells or whistles...

[tuna hp]

Others marvel at the great versatility of the G550 wing without resort to any bells or whistles...

Ha its just physics. A smaller wing with slats should be able to achieve better field performance AND better cruise efficiency. All else equal there would potentially be a tradeoff in terms of lower climb performance and engine-out performance, but thats straightforward.

It makes me assume that Bombardier and Dassault are terrible aerodynamicists. Their planes have slats and are also less efficient. If you take the max fuel and max range numbers for the G650 and the F5X, you see that the G650 uses only 16% more fuel per nm at its max cruise of 7,000nm @ M.85 compared to the F5X's efficiency at its max cruise of 5,200nm @ M.80. Considering how much larger, heavier built, faster and longer range the G650 is, thats a very small fuel consumption difference.

[dss3000]

Lets wait until until the F5 X is built for comparisons ! sales figure are all hogwash the 650 is a real airplane and it works fine. On the other hand the BBD is also a good performer with respectable performance, which competes head to head different strokes for different folks :)

[Trolltuner]

From the GII to the -650 they have stuck with a large, lightly loaded wing with no slats.

While true, their wing design has certainly changed over the years - especially between the original G-II (G-1159) and the G-III (G-1159A). The latter "supercritical" wing was also retrofitted to the "straight" G-II to make the G-IIB (G-1159B) with Gulfstream designed winglets. About 70% of the original G-IIs were retrofitted with Joe Clark's (Aviation Partners') winglets to create the G-IISP, using his patented "blended winglet" design.

I'm pretty sure that certification costs and efforts precluded the G-IISP AFM to reflect obvious performance increases however.

Cheers,

Tom

Home of the "Fresh Pick" STC - Trolltune Corporation (http://www.182stc.com)

Home (http://www.gulfstream-stc.com)

[Doodlebug]

Is the lower fuel-burn of the 550 when compared to the GLEX not also due to it's having a narrower fuselage cross-section?

[stilton]

'They have also had several in ground effect stalls including the last fatal one. Highly swept wings should have slats to control the boundary layer, provide a larger usable range of AoA and better stall characteristics, not least reducing leading edge stalls'


Agree, and my point exactly.


'Others marvel at the great versatility of the G550 wing without resort to any bells or whistles... '



Hardly bells and whistles, slats have been around for over 70 years and are basic aerodynamic enhancements to most modern jet's


A non slatted wing is also far more vulnerable to any wing contamination, as a few Challenger operators have discovered.

Perhaps Gulfstream just won't let that go of that G1 wing..

[envoy]

You raise a good point Stilton, but as I previously mentioned, any aircraft design needs to balance design characteristics to best meet the required spec. Every design feature carries a benefit - and a penalty.

I agree with you about the benefits of leading edge slats. I have sampled these benefits myself operating the Falcon 900, especially when landing on short/wet strips when we had surprising short(er) field performance. We used to contrast this performance against that of compatriots in the smaller/lighter CL604, which had no LE devices. We held that the LE slats were the key to the performance difference.

However: the incorporation of leading edge devices into a wing takes up space that robs you of fuel volume therein, and requires the carriage of additional hydraulic/electrical services for operation and more complicated ducting for leading edge anti icing. This all requires a tradeoff in available payload or fuel load, and more complicated systems where things can go wrong. These offsets might have been undesirable in the eyes of Gulfstream's engineers, assuming they were aiming to reduce complexity and maximise burnable fuel capacity.

There may well be other reasons why there are no slats on a Gulfstream wing. If so, I share your interest in learning why.

Are they hanging on to the GI wing?? Funny guy - or a typo! But maybe they are just exhibiting typical conservative design philosophy, slowly evolving over time with experience and experimentation. Boeing did the same for years, sticking to what they knew, but producing rubbish wings until the 777. If you ask Dassault, the reason why the 777 wing was a significant improvement was because Boeing started using Dassault's CATIA CAD/CAM systems.;)

[con-pilot]

I was once told by a Gulfstream salesman that the reason there are no leading edge devices on Gulfstreams is a heating issue for the leading edge anti-icing systems.

My reply was, "Well Boeing and Dassault figured it out, why can't your engineers?"

Got no reply. :p

Just one more reason we bought a 900EX rather than a G-IVSP.

[Lone_Ranger]

You bought a French design?, it is the better aircraft, but I'm quite shocked You admit it

[falconeasydriver]

Wash thy mouth forthwith Ranger, the 900EX is indeed a superb machine, as is the wing (even if the flap speeds are a little on the low side), and as for the 777, tis a delight...and I can stand up in the toilet to pee :E
You can brandish your aviators at the top of the stairs in a 550/650...but try getting in and out of LCY with 5 hrs gas.....

[Yellow & Blue Baron]

If slats would make Gulfstreams safer, then why don't they add them?

Someone asked if Falcon wings were better. I remember being told that while the early Gulfstreams had a forest of vortex generators the Dassault wing was smooth and clean! Falcon wing also handles runways with pitch better.

[Astra driver]

I'm sure that Gulfstream has looked at the idea of using LE devices with each new design but if you consider the two most recent designs, ie the G5/550 and the G650, both required the use of a large wingspan design to meet their very long range cruise requirements (6,500/6750 and 7,000nm respectively). By default this large wingspan will produce low t/o and landing speeds and hence largely negates the need for LE devices. For reference, I typically see Landing Ref speeds on both the 550 and the 650 in the 113 to 118 range.
As for takeoff performance, after reading how a Falcon can loft 5 hours worth of fuel out of LCY, I was curious what a 550/650 could manage out of a similar, sea level 4,800 ft strip on a 30 C day and enroute at ISA + 10

G550 : MTOW 80,000 lbs, enough to carry 5 pax 3,400 nm at M0.85 (7.5 hrs)
G650 : MTOW 85,000 lbs, enough to carry 5 pax 4,300 nm at M0.85 (9 hrs)

(As for landing, max landing weights for 550/650 are 75,300/83,500 respectively, still enough for 6 hours/8.5 hours and well within 4,800ft)

And yes I know that Gulfstreams can't LAND at LCY due to the fact that they are unable to meet the steep GS requirements without deploying flight spoilers which is currently prohibited with landing gear down per the AFM, although Gulfstream is rumored to be working on an ASC for the '650 at least to allow this.

No question the Falcons, Bombardiers, etc are all great aircraft in their own right, and I'm sure Gulfstream would be using LE devices too if they thought it would produce better results.

[falconeasydriver]

Astra, interesting info, however, have you looked at the OEI perf in respect of the obstacles around LCY?
That was ALWAYS the limiting factor with the 900, it wasn't as limited by field length.

[con-pilot]

Wash thy mouth forthwith Ranger, the 900EX is indeed a superb machine

We had a series of demonstration flights between the 900EX and the G-IVSP, most from Aspen to St. Maarten and from OKC to various destinations in the UK and Europe.

Primary deciding factor was Aspen performance on summer days and whether either aircraft had the capability of going to London non-stop from Aspen.

The 900EX was capable of non-stopping Aspen to London in the winter*, the G-IVSP was not, plus the boss liked the idea of three engines for Pacific crossing to China and Singapore, therefore, we bought the 900EX.

Both aircraft are excellent performers and I would have been happy flying either one. The Falcon was a nicer handing machine than the Gulfstream, but in truth that was not a deciding factor.


* Going non-stop to London from Aspen greatly depended on the OAT at Aspen and good VMC weather both at Aspen and London. Plus the expected tail winds of that time of year. To be honest, I have forgotten the minimum OAT we needed at Aspen. However, in the dead of winter on early clear mornings, it would usually be low enough to plan a 07:00 (local) departure.

Once the boss showed up for a 07:00 departure for London at 10:00 and guess what, hello Bangor. He took it in good humour however, knew it was his fault.

[HeliStudent]

con-pilot that's interesting. :ok:

It is true (as Yellow & Blue Baron mentioned above) that the Falcon series (50's and 900's) are much better at handling sloped/inclined runways?