Want to read Slashdot from your mobile device? Point it at m.slashdot.org and keep reading!


Forgot your password?
Check out the new SourceForge HTML5 internet speed test! No Flash necessary and runs on all devices. ×

Comment Re:I don't see how this matters (Score 1) 339

The big problem I see with this is that an incompetant student on a competent team could be carried though while a competent student on an incompetent team could be failed.

What if any mechanisms did they have in place to try and prevent this?

Peer review at the end of each semester was the main mechanism. While the reviews weren't the only component to the grade they were factored heavily by the professor. The professor and TAs keep track of team progress through weekly (or if a team's struggling, more frequent) meetings and update presentations, plus they have enough experience overseeing these projects to get a good idea of who's actually doing what.

The other thing it helped with was teaching the students about how to deal with team dynamics in which the inevitable slacker tried to skate through. How many times have people worked projects in industry when you had a moron on your team and not known what to do with them? At this point in the curriculum the vast majority of the technically incompetant students should have been weeded out, so most of the problems occured due to clashing personalities and other 'team dynamic' problems. The year after I graduated one of the groups actually ousted their incompetant team leader through a (obviously bloodless) coup and they were able to complete their project successfully. The former leader was a decent engineer, he just sucked at the leadership/management part of his former role.

As difficult as the task seems, a team has to actively try to fail as a whole. The professor had been known to fail teams before, but only very rarely. If a team is struggling with a technical aspect of the design there's a lot of help available but the help is only for advice, they won't do the work for you. Peer pressure is usually a pretty good motivator to get adequate work out of everyone on a team even though there will be varying levels of individual effort. However if there's a rare outlier that just won't work for whatever reason they'll be pulled by the professor.

Comment Re:I don't see how this matters (Score 1) 339

I don't have a better way of doing things to suggest.

One thing I always felt were better for learning and testing for understanding of material were projects rather than arbitrary exam questions. When I was working on my aerospace engineering degree professors usually tried to incorporate some kind of project that relates to the course. Some courses, such as CFD, were nothing but programming projects that used techniques we learned during the lectures. Other courses, like the multitude of aerodynamics courses, had everything from building small gliders to emphesize stability and control to writing simple lifting line codes for analysis. Structures courses included design, construction and testing of simple structures that gave real world examples of the principles covered in the lectures. Ultimately the capstone course for the degree was nothing but a single group project that was a "fly or die" course. Design a plane that has certain capabilites as outlined at the beginning of the Fall semester. In the Spring semester you have to build and flight test the plane. If it doesn't fly, you don't graduate. If you can't build a plane that can fly you probably shouldn't be receiving a degree in aerospace engineering so there's lots of incentive to get it right and make sure everyone on the team is pulling their weight.

Granted, certain curricula don't facilitate projects as easily as others; however, for the ones that do I feel that they're a much better benchmark of understanding.

Comment Re:Is summary accurate? (Score 1) 911

Auto-throttle /= Fly-by-wire.

The next-gen 737s are not Fly-by-wire aircraft. It would have added an extra $20M to the pricetag if they had created a FBW system.

As far as the Auto-throttle goes it's easily disengaged with the press of a button. Which apparently they had done when that problem happened twice before in that same aircraft, no one's quite sure why they didn't do it that particular time.

Comment Re: Manual Overrides (Score 1) 911

Not to be pedantic, but Airbus and Boeing are certified under FAR Part 25, not 23. Beyond that, when talking about not being able to engage manual override we're not talking about the autopilot but rather the flight control system which is only governed by 25.1309 as long as it maintains aircraft performance as outlined in 25.671 and 25.672. Autopilots are governed by 25.1329 and are required to have a quick release for manual override. As someone who's used both FAR 23/25 and the military version (MIL-HDBK-516), I can tell you it's really easy to design you way around the FARs to acheive both flight control systems used by Boeing and Airbus and still be well within the guidelines. There's a good article in the IEEE journal written in 1993 about the Airbus flight control system and outlines some of the requirements they used: http://personales.upv.es/juaruiga/teaching/TFC/Material/Trabajos/AIRBUS.PDF

Comment Re:Is summary accurate? (Score 1) 911

Just a minor clarification to your post. The only full FBW (ie computer in the loop, not just electrically actuated) plane that Boeing currently produces is the 777. Other aircraft have electrically actuated controls but the input from the pilot is not augmented by the flight control systems in manual control. It is a major design philosophy difference between the two companies and the majority of people I know in the aerospace industry prefer Boeings implementation... granted they're all Americans, but it'd still be a hard sell to get them to relinquish control like that.

Comment Re:Is summary accurate? (Score 5, Informative) 911

In order to get to the manual override mode in an Airbus (IIRC) you have to navigate through several screens on the flight control computer and disable everything via menus. In order to activate the manual override mode on a Boeing plane you just have to move the yoke. In an emergency situation where, for whatever reason, the automated flight controls aren't working or are working improperly the Boeing override implementation is vastly superior to that of the Airbus. Not to say that autopilots and fly-by-wire systems aren't useful, but they aren't infoulable and limiting the pilot's ability to respond to a situation just seems like a really bad idea.

Comment Re:Have tried it, and it is awesome. ND Aero Eng (Score 1) 259

Not to get into an AE pissing contest but NCSU did that project for their 2003-2004 senior design course. That was a few years before I graduated but I remember seeing them fly and it was really impressive. One of the many videos: http://www.youtube.com/watch?v=RX47ofUrTHQ

It's good to see other schools requiring building and flight testing though. Too many times I've run across engineering students and/or recent graduates who have a lot of theoretical background but don't actually have any idea of how much work actually goes into building even a simple aircraft. Raymer's book was one of the many resources used for our project but it's definitely a good overview. Learning to fly an RC aircraft can be tricky but if the poster starts on something like a T-hawk ( http://www.readytoflyfun.com/ ) it's pretty easy to learn the basic skills and progress from there.

Comment Who gave them the photo? (Score 4, Interesting) 1297

TFA says they got the photo from the Army not the Marines.

Stone, 37, said both he and Parker, 39, were most proud of the signed Saddam photo, given to them by the US Army's 4th Infantry Division.

But then again it states in the summary of the article that they recieved the photo from the Marines. So which is it?

Comment Re:Another idea? (Score 1) 242

Just my opinion, but I think you guys are blowing the vortices out of proportion as far as the size of the problem they create. You're essentially talking about forebody vortices, which usually only cause a problem when dealing with high AoA (angle of attack) flight. A lot of research has been done in controlling and even utilizing these types of vortices. Strakes and other vortex generating devices could be used to limit the size of the vortex or redirect the flow of the air around the aircraft.

If a new aircraft was to be designed the wing section could even take these vortices into account and have beneficial flight characteristics because of them (for instance most supersonic aircraft use vortex lift in order to operate at a higher AoA than would be allowed by the camber of the wing, that wouldn't be the solution in this case, but it illustrates how vortices aren't always bad).

My main concern for this idea, as was stated before, is the flow of air into the engine. If the flow is forced around that turn you''ll have large areas of separation, which in turn causes turbulence problems in the intake. When you have turbulence reach the compressor you have the possibility of a compressor stall. If you don't have a compressor stall you're still losing efficiency of the overall engine due to the flow. The reason pylon mounted engines have cowlings is to help smoothly guide the airflow from all around the engine into the inlet so there's very little turbulence at the compressor face. Without a cowling you'll lose a few % efficiency simply due to the knife-edge the flow has to transition around to get into the inlet.

If you have access to the Journal of Aircraft, Vol. 44, No. 3, May-June 2007 has a rather interesting article entitled: "Tradeoffs in Jet Inlet Design: A Historical Perspective" by Andras Sobester. It does a good job of explaining how much of a pain in the ass it is to design an inlet and some of the issues involved when trying to do so (bird strikes, unfortunately, are not included on that list).

And unlike CompMD (who has definitely had some good ideas thus far), I'm an aerospace engineer all the time. Plus I stayed at a Holiday Inn Express last night.

Comment Re:Another idea? (Score 3, Informative) 242

A couple issues with putting a cone over the inlet of a subsonic engine.

1) If you restrict airflow to only entering from the sides, you're going to have massive separation bubbles as that flow has to turn 90 degrees to enter an axial engine. That results in a loss of efficiency and significantly reduces engine performance.

2) The added weight of this would kill the proposal for any aircraft manufacturer out there.

And not to be pedantic, but the inlet and thrust has a lot to do with whether something flies or not. If you can't get sufficient airflow over the wings to begin with your aircraft isn't going to achieve takeoff.

Comment Re:white knight 2 looks too fragile (Score 2, Informative) 81

Actually all the military stuff is governed by MIL-HDBK-516. They don't explicitly specify a SF when they release the RFP. The whole process is extremely tailorable to the specific aircraft being designed, meaning there are no hard requirements just vague criteria like "Verify that the airframe is designed such that ultimate loads are obtained by multiplication of limit loads by the appropriate factors of uncertainty. Also verify that the ultimate loads are used in the design of elements of the airframe subject to a deterministic design approach." (MIL-HDBK-516B, 5.1.5)

That criteria is used as the starting point for negotiations between the aircraft designers and the airworthiness certification offices. Not all criteria listed in 516 are applicable to all aircraft so the first task is to go through the document and determine what is applicable and what isn't. If a criteria is found to be applicable you can't modify it in any way, but you can enact a standard to fulfill that criteria. These standards are the primary source of negotiation between the certification offices and the designers. For example, a typical standard for criteria 5.3.3 (Stresses and strains in airframe structural members are properly controlled...) would be something like a SF of 1.33 for cast parts, 1.15 for fitted parts (if not demonstrated by static test), and 2.0 for bearings for elements with relative motion. However if an aircraft manufacturer comes back with a new process for casting a part that reduces foundry quality control problems and can prove through testing that they have a more accurate construction method thus reducing the need for a factor of safety, then they'll most likely get a reduction on that standard.

Anyway, long story short:

None of the military requirements are set in stone. The standards are negotiated with military technical area experts (TAE). From that the designers submit an Engineering/Data Requirement Agreement Plan (EDRAP) and use that document to outline all the analysis testing and evaluation needed to be done. Since the testing and evaluation is a huge cost driver for the developer they want to reduce the number of tests performed on the system. Each test creates an artifact that is submitted with the agreed upon EDRAP as well as other documents (system safety outline, FMEA, etc) which are then sent back to the certifying authority who then determine whether or not all the requirements were met. If they have been, then a flight clearance is released for that design.

And that, in a nutshell, is the military airworthiness certification process.

Comment Re:white knight 2 looks too fragile (Score 1) 81

And given that the methods to check the structural soundness of such a set-up are well established, and that Rutan isn't an idiot, I'd imagine it can handle worst case scenario loads with a safety factor of 1.2 or 1.3, as is common for any aerospace application.

The SF is actually prescribed for the majority of civilian applications. Since the MTOW of White Knight 2 is greater than 12,500 pounds it falls under FAR Part 25 for certification requirements. The limit load SF prescribed from FAR Part 25.303 is 1.5.

Slashdot Top Deals

Your mode of life will be changed to EBCDIC.