Legacy Bashfest - Bring it on!

[banned username 2]

Watch what you hope for, they may ask you to take it to Shanghai!!

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LOL! No kidding!

 

[GVFlyer]

WSCoD

This is the part where your knowledge hole appears. The airplane had vortilons from day one. The winglets were not added until nearly a decade
later.

I had thought that the wing sprouted vortilons during developmental test, but one of the Embraer factory pilots says otherwise.

Embraer factory pilot, Marelo Romanelli remarked to Aviation International New's Robert P. Mark during a written and flight review of the Legacy conducted by the magazine:

Strakes have been added beneath the rear fuselage and vortillons beneath the leading edge of the wings to increase stability, especially because of the yaw produced by the winglets. Although the ventral strakes do detract somewhat from the aircraft’s clean lines, they make up for it in dispatch reliability, since the strakes can negate the need for a yaw damper on the MEL list for short periods.

As for the engineering goes I can't comment. The winglets must do something or they would be gone. It is probably hard to mate winglets after the fact so some concessions have to be made. I think the strakes look cool any way.

Properly engineered winglets do quite a lot. Gulfstream and Learjet began winglet research in the 1970's. This excerpt is from NASA's Concept2Reality website as Gulfstream used a series of NASA Winglet designs on it's jets, did wing development at NASA Langley and was a developmental partner with NASA for the world's only Supercritical Airfoil Winglet jointly developed for use on the GV. I included the portion on the Learjet to demonstrate to you that properly engineered winglets increase directional stability rather than decreasing it as in the case of the Legacy.

In 1977, Learjet displayed an exciting new test-bed aircraft designated the Learjet Model 28 at the National Business Aircraft Association convention. The Model 28 had been involved in high priority developmental testing of a new wing for a major new Learjet project to be known as the Model 55... Learjet developed the winglet design without NASA assistance, and referred to the new wing as the Longhorn, which coupled the new NASA winglet technology with a wing that had higher aspect ratio. Although the Model 28 was intended to be a prototype experimental aircraft, the performance of the new aircraft was extremely impressive and resulted in a production commitment from Learjet. Flight tests made with and without winglets showed that the winglets increased range by about 6.5 percent and also improved directional stability.


http://oea.larc.nasa.gov/PAIS/Conce...hics/fig029.jpg

Record-setting Gulfstream V with supercritical airfoil sections for its winglet design.

Gulfstream had also been aggressively studying applications of winglets in the late 1970s (contemporary with the Lear activities) and incorporated winglets in its line of business jet transports including the Gulfstream III, Gulfstream IV, and Gulfstream V. The performance of the Gulfstream V has been spectacular. Its operational range of 6,500 nmi at a cruise Mach number of 0.80, and cruise speed capability up to Mach 0.89, permits routine nonstop business travel for routes such as New York–Tokyo. The Gulfstream V also holds over 70 world and national flight records.

Another BS call on you here. The wing tanks are the same as the LR (the Legacy actually claims a slight reduction in wing fuel from the LR). The fuel tanks in the fuselage don't seem too complicated: one bisected fwd one bisected aft. Grand total four fuse two wing tanks.

Two wing tanks and four fuselage tanks! The Gulfstream has two wing tanks, thats it, total - two tanks. There is no fuel management, if you start with the fuel balanced it will remain balanced. It is not possible to load a Gulfstream in an out-of-CG configuration as you can with aircraft with multiple fuel tanks like the Challenger and apparently, the Legacy.

As far as fuel tank evolution is concerned, this information is from Embraer press releases:

[font=&quot]The last day of March marked a major milestone for Embraer’s super-midsize Legacy, a business-jet version of the ERJ-135 regional jet, when it achieved first flight. Aircraft S/N 363–the first iteration to be fitted with auxiliary fuel tanks (two in the belly and two in the aft section), winglets and aft strakes–took off from the São José dos Campos Airport (SBSJ) in Brazil on a sortie that lasted some two hours on March 31. The aircraft program, Embraer’s first foray into the business aviation arena, was officially launched last year at the Farnborough Air Show.[/font][font=&quot]

[/font][font=&quot]The 3,200nm range is with eight passengers on board and was achieved by extending the fairing and redesigning the cargo hold of the ERJ-135 to allow for the additional 7,000 lbs of fuel.[/font]

As for Embraer vs G design philosophy, take a llok at what it was built to do. Embraer told its customers it could deliver 2000-3000+ hours per year and lots of cycles with high reliability. That is what it was made to do and is doing. I cannot call that fragile. In fact, it may be overbuilt for the corporate world...

Then apparently Embraer only expects the Legacy to stay in service between a year and eight months and two and one-half years, because it is only warrantied for 5,000 hours (or 5 years, whichever comes first). The Gulfstream is warrantied for 20 years with no hour limitations.

Gulfstream is wonderful, but it sounds like they are a lot less efficient than they need to be if they are as overbuilt as you say.

Stucture equals safety. There is no such thing as overbuilt when you're talking about high altitude aircraft. Here's what the regulation says.

[font=&quot]Sec. 25.365 - Pressurized compartment loads.[/font][font=&quot]

For airplanes with one or more pressurized compartments the following apply:

(a) The airplane structure must be strong enough to withstand the flight loads combined with pressure differential loads from zero up to the maximum relief valve setting.

(b) The external pressure distribution in flight, and stress concentrations and fatigue effects must be accounted for.

(c) If landings may be made with the compartment pressurized, landing loads must be combined with pressure differential loads from zero up to the maximum allowed during landing.

(d) The airplane structure must be designed to be able to withstand the pressure differential loads corresponding to the maximum relief valve setting multiplied by a factor of 1.33 for airplanes to be approved for operation to 45,000 feet or by a factor of 1.67 for airplanes to be approved for operation above 45,000 feet, omitting other loads.

The maximum PSID for the GV/G550 is 10.48 psi and the GIV/G450 uses 9.8 psi.
[/font]

Also, forgive my ignorance, but would the Legacy delay flutter with a boosted elevator?

The short answer is yes. During developmental test the Legacy encountered early Mach effects, buffet and buzz prior to encountering elevator flutter. Such effects are characteristic of flight controls that are not hydraulically boosted . I participated in the certification and military conformity of the C-21 Learjet. It also had unboosted flight controls. Mach Crit for the 39'6" wing was at M 0.75. At that speed you could see the shock wave form up on the wing's upper surface. Mmo was M 0.81. At altitude, at M 0.825-0.83 a shock wave would form up on the ailerons which could not offer hydraulic resistance for stability and they would buzz and cause control wheel snatching. If you went faster or rolled into a turn, Mach buffet would occur followed by a pronounced rumble.

On the GV, even when it was inadvertently flown to Mach 1.07, there was no buzz, no buffet, no rumble, no roll off and no flutter.

The Legacy doesn't have elevator hydraulics for the same reason it doesn't have roll control spoilers.The Legacy was designed to be cheap and light. Spoilers and boosted elevators would increase complexity, weight and cost. The strength needed to make a jet warrantied for 20 years requires structure which increases weight which increases passenger seat mile cost. The driving force behind EMB 145/ EMB 135 / Legacy development was keeping passenger seat mile costs down and acquisition costs low.

GV





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[JetBlast2000]

Strakes have been added beneath the rear fuselage and vortillons beneath the leading edge of the wings to increase stability, especially because of the yaw produced by the winglets.

properly engineered winglets increase directional stability rather than decreasing it as in the case of the Legacy.

[font=&quot]Any chance you had any more info on this topic? Not that I don’t believe the EMB pilot, but there seems to be more here than meets the eye. I’m just not well enough versed in the subject to know…[/font]

 

[GVFlyer]

WSCoD Winglet Induced Yaw Instabilities

[font=&quot]Any chance you had any more info on this topic? Not that I don’t believe the EMB pilot, but there seems to be more here than meets the eye. I’m just not well enough versed in the subject to know…[/font]

Sure, here you go.

This is from an Embraer press release.


According to Sam Hill, vice chairman of West Palm Beach, Fla.-based Embraer Aircraft Corp.–the division that is marketing the 3,200-nm-range Legacy–an ERJ-135 (S/N 002) fitted with winglets and a dummy belly-tank fairing to simulate the aerodynamics of the Legacy, has been flying for several months. In those tests it was determined that aft strakes needed to be added to the design for “better stability and handling characteristics,” even though the twinjets are equipped with a yaw damper. Additionally, the aft strakes eliminate the yaw damper as an MEL item, which potentially translates into higher dispatch reliability.


This is from "Aviation International News" flight review of the Legacy.


Strakes have been added beneath the rear fuselage and vortillons beneath the leading edge of the wings to increase stability, especially because of the yaw produced by the winglets. Although the ventral strakes do detract somewhat from the aircraft’s clean lines, they make up for it in dispatch reliability, since the strakes can negate the need for a yaw damper on the MEL list for short periods. The strakes under the leading edges of the wings assist with air flow over the ailerons.[font=&quot]
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[font=&quot]And here is more information than you ever wanted on Embraer winglets from a Computational Fluid Dynamics website that I hang out on.
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http://www.fluent.com/solutions/articles/ja133.pdf



GV

 

[GVFlyer]

WSCoD

The thread's primary debators have not even established a true baseline upon which to objectively discuss the airplane in question. The data being quoted is in dispute. That is quite clear. I would think that if a Legacy is so poor an airplane then use the best numbers available - i.e. those most favorable to it - in order to evaluate it. It is quite clear that the Gulfstream numbers used are most favorable to it coming from a man who is arguably one of their test pilots. To use the best numbers for yourself and the worst for your competition is automatically an unbalanced playing field.

In order to insure objectivity, the data used for Gulfstreams were from the same Conklin and deDecker I used for Legacy data.

All the data I have managed to find - which shows a more up-to-date acquisition of information - exceeds C&DD for the Legacy. Why are some afraid to simply accept that as factual for the sake of the argument? If Embraer were lying about their performance numbers would they not be liable as well? I would think it was a bit more important for the manufacturer to get its numbers correct. Needless to say, nothing I have seen anywhere other than C&DD shows the 3,050NM max. range that was quoted earlier.

The current Conklin and deDecker shows the Legacy range to be 3,220 nm @ M 0.74 which is what I have quoted. What do you show for Legacy range?

On fuel burn alone the Legacy beats the G-350 by 27.7% per hour. And we all know Legacy pilots make much less (being the second class citizens they are treated like here is that surprising to anyone?). EMB parts are cheaper (being made out of tin foil and such), too, so how can the G-350 even approach 25% much less 7%? It defies the laws of physics in my mind.

Pay attention this time! As I previously stated Direct Operating Costs are a combination of factors including maintenance labor, parts, engine reserves, and miscellaneous flight expenses as well as fuel burn. Quality and a comprehensive warranty play a part in operating costs as do the 12,000 hour TBO engines. Gulfstream year to date dispatch reliability rate is 99.85% so those expensive Gulfstream parts aren't breaking that often, apparently those EMB tin foil parts are.

Cost per mile numbers claimed by Embraer take into account the difference in speed, by the way, and Embraer claims a huge savings over G-Anything. I have yet to hear the cost of MX and parts replacement addressed either, but based on discussions, Gulfstream parts cost a great deal more. Also I am told Embraer's "on condition" engine replacement program is also cheaper based on how it is "charged" to the customer - based on hour credits and other things - to the point that Embraer is claiming a 40% operating savings over a G-350.

Heresay and "Embraer claims" say it all, no further explanation is necessary.

Six million bucks is a lot of coin, too, so I don't know that throwing money at something necessarily makes it better.

It is certainly better. At only $6.35 million more than the Legacy, the G350 is a real bargain. It exceeds the Legacy's performance and general characteristics in every aspect by a wide margin. Speed, range, field performance, comfort, reliability, longevity, warranty, altitude capabilty, systems and retained value are all significantly better in the Gulfstream.

GV





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[ERJ-140]

This is from "Aviation International News" flight review of the Legacy.


Strakes have been added beneath the rear fuselage and vortillons beneath the leading edge of the wings to increase stability, especially because of the yaw produced by the winglets. Although the ventral strakes do detract somewhat from the aircraft’s clean lines, they make up for it in dispatch reliability, since the strakes can negate the need for a yaw damper on the MEL list for short periods. The strakes under the leading edges of the wings assist with air flow over the ailerons.
______

Embraer factory pilot, Marelo Romanelli remarked to Aviation International New's Robert P. Mark during a written and flight review of the Legacy conducted by the magazine:

Strakes have been added beneath the rear fuselage and vortillons beneath the leading edge of the wings to increase stability, especially because of the yaw produced by the winglets. Although the ventral strakes do detract somewhat from the aircraft’s clean lines, they make up for it in dispatch reliability, since the strakes can negate the need for a yaw damper on the MEL list for short periods.

The magazine is in error as vortilons were part of the ERJ nearly a decade BEFORE winglets were even thought of. Anyone who has ever even seen a ERJ knows this.

Romaneli was clearly misquoted or something was lost in translation from words to print as the Vortilons have nothing whatsoever to do with winglets. The Vortilons have been on the ERJ since the very first airplane off the assembly line. Winglets didn't appear until over 350 airplanes later.

Romaneli's e-mail address is readily available. I am sure one could ask him if he wished.

My personal belief on stability issues are that the 145 being much longer is perfectly stable. Shortening the fuselage 20 feet or so to make a 135 decreased the rudder arm available and made the airplane slightly less stable than it was as a 140 or 145.

Perhaps also the stability issue is related to the higher ceiling as well.

 

[ERJ-140]

[font=&quot]Any chance you had any more info on this topic? Not that I don’t believe the EMB pilot, but there seems to be more here than meets the eye. I’m just not well enough versed in the subject to know…[/font]

When it comes to winglets, neither am I. All I know is that every airplane is unique. G-IV winglets won't work on a Legacy and BBJ winglets won't work on a 737-300. Some (most) airplanes appear to suffer stability issues when winglets are added (at least in the past). Newer designs perhaps mitigate these issues, but I have a feeling the Legacy winglets were designed with less knowledge than is available today. If the increase efficiency at the expense of some stability (corrected with strakes) I would consider that an acceptable tradeoff.

 

[ERJ-140]

The Legacy doesn't have elevator hydraulics for the same reason it doesn't have roll control spoilers.The Legacy was designed to be cheap and light. Spoilers and boosted elevators would increase complexity, weight and cost. The strength needed to make a jet warrantied for 20 years requires structure which increases weight which increases passenger seat mile cost. The driving force behind EMB 145/ EMB 135 / Legacy development was keeping passenger seat mile costs down and acquisition costs low.

GV

[font=&quot]
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I do not dispute you here at all. But again, there is a difference between low cost and fragile. The airplane cannot be fragile to do what it does. I doubt corporate Legacys will ever see the hours piled up by the ERJ fleet. 5000 hours is probably 10 years worth of flying to the average corporate flight department. An ERJ does that much in two years or less.

 

[ERJ-140]

The current Conklin and deDecker shows the Legacy range to be 3,220 nm @ M 0.74 which is what I have quoted. What do you show for Legacy range?

3,250NM with NBAA IFR Reserves at M 0.74 with 8 Pax.
3,050NM with NBAA IFR Reserves at M 0.80 with 8 Pax.

So, 30NM. That's better at least than the 3,000 seen earlier.

Pay attention this time! As I previously stated Direct Operating Costs are a combination of factors including maintenance labor, parts, engine reserves, and miscellaneous flight expenses as well as fuel burn. Quality and a comprehensive warranty play a part in operating costs as do the 12,000 hour TBO engines. Gulfstream year to date dispatch reliability rate is 99.85% so those expensive Gulfstream parts aren't breaking that often, apparently those EMB tin foil parts are.



Heresay and "Embraer claims" say it all, no further explanation is necessary.


It is certainly better. At only $6.35 million more than the Legacy, the G350 is a real bargain. It exceeds Legacy performance and characteristics in every aspect by a wide margin. Speed, range, field performance, comfort, reliability, longevity, warranty, altitude capabilty, systems and retained value are all significantly better in the Gulfstream.

No need to get testy.

Yes, DOCs take into account many factors. I am not a warranty expert and I have no idea what Embraer's warranty is but I can tell you there are other ways to warranty things (per hour, per mile, per cycle, etc.). Think of your warranty on your car battery. Free replacement up to so many months then pro-rated from then on. Embraer must offer a competitive warranty or they wouldn't have a chance selling them. Also, what are the part replacement costs on a Gulfstream 350 for example? If your window heating elements failed would you just get a brand new window no matter how old the airplane is?

That being said, the Legacy is meant to compete with older and smaller jets than the G-350. It does offer people who want a G-sized cabin an alternative without going to a G-350 (six million is a lot to me - heck, five bucks is a lot to me these days! ).

Your cost per mile is most certainly higher, regardless.

I will do some digging to find this information if I can. You have any such data available?

 

[ERJ-140]

Good article on winglets, but it simply states what other studies have - "Winglets can contribute to Dutch Roll."

I see this theme repeated constantly. Designing a perfect winglet after-the-fact is a very difficult process.

To quote NASA:
" Not all airplanes use winglets, however. Planes with extra-long wings sometimes have folding wings to accommodate their dimensions. Winglets would be in the way with such designs. In other planes, weight and design issues could cause instability if a winglet was added to the wing area. In the proper context, though, winglets have proven themselves valuable in the quest to make the skies safer and the planes more economical. "

That being said, Aviation Partners and/or Blended Winglet Technologies may have been able to design a better winglet for the airplane but I am not the one to know.


As for vortilons, the "G-IISP" with AP winglets added vortilons in place of fences in conjunction with the blended winglet. Vortilons are not just an Embraer thing.