Jeff's Lunchbreak

From the Ground Up Buy it from Amazon

Fred Weick is probably not a familiar name to most people, even those involved in aviation, despite the significant contributions he's made. He's probably most well known to Ercoupe pilots - Weick designed the plane back in the '40s, and is spoken of almost reverentially on Ercoupe forums (such as the fly-in and tech groups on Yahoo). My great uncle and I share an Ercoupe (and by share - I mean he keeps it in Pittsburgh and flies it, while I get to dream about it while I'm down here in Texas). It was when I first started following along on those Ercoupe discussion groups that Weick became a name that I would remember.

Later on, after I'd started working as an aeronautical engineer, and was just getting started doing design work on propellers, while doing some research on the subject, I came across an interesting paper, Propeller design I: practical application of the blade element theory, by none other than Fred Weick. That lead me to pay even more attention to his name, and it began popping up all over the place.

Continue reading "Book Review - From the Ground Up" »

Posted by Jeff on Friday, May 9 | Permalink | Comments (0) | TrackBacks (0)

104 years ago today, the Wright brothers became the first humans to truly fulfill the dream of flight. Yes, the Montgolfier brothers had their hot air balloon, and others like Hiram Maxim may have gotten an airplane to momentarily lift off under its own power, and Otto Lilienthal had been experimenting with his weight shift gliders decades previously, but it was the Wright Brothers who were the first to really integrate the structures, aerodynamics, and control into the first successful airplane.

Flying has become so common place today that we take it for granted. People complain about the cramped seats, the long lines to get through security, the bad food (if you even get any) on flights. But just remember how long people have dreamt of flight, for how long people looked to the skies wanting to emulate the birds. Flying used to be the stuff of myth and legends, reserved for the gods. Now, we can all get in an airplane, and soar above the clouds. It really is something special.

Happy Wright Brothers Day.

Posted by Jeff on Monday, Dec 17 | Permalink | Comments (5) | TrackBacks (0)

From time to time, I'll receive e-mails from people asking me for advice on some good engineering books to use for aircraft design. Dan Raymer, a well respected engineer, already has a list on his website. It's a pretty long list, though, and would take a while to build up that collection. So, I figured I would recommend the ones that I use most often. The following three books are ones that I use on a regular basis that are generally useful for all aircraft.

Continue reading "Aviation Books" »

Posted by Jeff on Monday, Oct 29 | Permalink | Comments (0) | TrackBacks (0)

This entry is basically, Part II of Where's My Flying Car.

When will there be an aircraft in every garage? In a word - never. Okay, never's a long time, so perhaps I shouldn't be making such a sweeping statement, but I really don't think that it will happen anytime soon.

People have limited incomes, and an aircraft will always be a sizeable investment. I think the automobile industry makes for a good comparison - it's fairly mature, and aircraft are very similar in complexity to an automobile. Even if aircraft were to be mass produced, they're going to be similar in price to automobiles. That's not cheap. People aren't going to go out and buy an aircraft in addition to everything they already own. So, since aircraft would presumably be fulfilling many of the purposes that people currently use their automobiles for, it would stand to reason that a majority of people will purchase aircraft only when they make good substitutes for their automobiles. Unfortunatley, there are two big reasons why I don't think that's the case.

For one thing, flying will always carry higher stakes than driving. You can drive a car that's in bad repair, or with a rough-running engine, or that has a low tire, or any myriad of problems. Yes, it may be a little more dangerous, but I've been in an automobile several times when it's broken down or gotten a flat, and all that happens is that you pull over to the side of the road, and have to get it fixed. Sure, it's an inconvenience, but it's rarely life threatening. That's not the case for an aircraft. If you're in the air and have a problem, you still need to get back down. Yes, pilots train for this, and yes, many emergency landings are performed safely every year, but many emergency landings also result in accidents. And there are some regions that just don't have much area suitable for emergency landings (lots of trees, uneven land, urban areas, etc). So, you always need to be sure that an aircraft is in good condition before climbing in to go somewhere - you need to do your pre-flight inspection every time, to make sure that nothing's happened. You can't just hop in to run down to the grocery store or to fly to the mall to do your Christmas shopping like you could in a car.

It's common to hear the claim that airplanes are safer than cars, or that the most dangerous part of a flight is the car ride to the airport. Statistically, that's true for airliners, but not for other types of flying (more info). And the only reason it's true for airliners is because there's so much maintenance on the airplanes to ensure their mechanical safety, and so much training for the pilots, to ensure that they can cope with any situation. Perhaps pilot training can be replaced with a sufficiently advanced computer control, but maintenance will always be an issue. As I wrote in the previous paragraph, any aircraft will require an inspection prior to every trip, which really does limit their utility for personal transportation.

The other major factor I see is weather. Wind, turbulence, fog, heavy rain - these are all big concerns for flying. Yes, they're concerns for automobiles, too, but you can continue driving a car in far worse conditions than what would ground an airplane. I've been caught in heavy thunderstorms, where I had to slow my car way down and it took me twice as long to get to where I was going, but I still got there. Had I been flying, I would have had to turn around to go back home (actually, before flying, I probably would have checked the weather, and never attempted a flight into conditions like that to begin with), and I never would have gotten to where I wanted to go.

To expand a bit on this weather issue - it's not just a matter of getting sensors that could peer through fog and rain, or having the skill to safely land in gusty conditions, although those are important. It's the fact that aircraft are shaken around a lot more by wind than cars are, because it's the atmosphere itself supporting the aircraft. Anybody who's been on an airliner knows what turbulence feels like - just imagine what a really bad thunderstorm could do. Small planes can get caught in updrafts or downdrafts that are so strong, that no matter what the pilot does he'll get pulled along with them. Maybe the aircraft of the future will have big enough engines that this won't be a problem, and maybe they'll be able to fly high enough that they'll fly above most storms (though being fully pressurized just adds to the maitenance related safety concerns), but that still won't help when a powerful thunderstorm's sitting right over top of you when you want to take off, or sitting right over top of your intended destination.

And I haven't even touched on traffic. Look at what it's like trying to get into a mall parking lot during Christmas season right now - just imagine if all those people were coming in aircraft instead of cars.

I hate to be a naysayer. As a pilot and aerospace engineer myself, I'd love to see personal aircraft become much more common. And perhaps one day, many of the problems I discussed above will be solved. But, being realistic, I have to admit that the demand for personal aircraft will never be the same as that for automobiles, and we're kidding ourselves if we think otherwise. So, when will there be an aircraft in every garage? Not in my lifetime.

Posted by Jeff on Friday, Oct 26 | Permalink | Comments (0) | TrackBacks (0)

I only have a very small update for today. Way back when I had my co-op during college, I figured out a way to fold a pretty good glider out of a Post-It note. I put up a page with instructions on how to fold it not long after, but that page has never been as "attractive" as I would have liked. A few years ago, I tried taking digital photos of the glider to put at the top of the page, but the camera I had then didn't have a good macro setting, so the pictures were awfully blury. So, just recently, I wasted a few minutes making a 3D model of the glider in Solidworks, and using a screen shot from that for the picture at the top of the page. I also added a small note of about a book that used that glider, Post-It: Ideas That Stick!,along with some pictures.

Posted by Jeff on Wednesday, Oct 10 | Permalink | Comments (0) | TrackBacks (0)

The single most popular page on this site is my Autogyros essay. Consequently, I never want to mess around with it too much (if it ain't broke, don't fix it). However, I saw a few areas that I could definitely improve upon, so I made some changes. The biggest of those were expanding the explanation of autorotation, adding a German translation that a reader had sent to me, and creating an archive of previous versions (mainly to give a stable copy at a fixed url for citations). Numerous smaller changes were made throughout the text to improve readability, and a few typos were corrected.

Posted by Jeff on Friday, Oct 5 | Permalink | Comments (0) | TrackBacks (0)

Well, I conceived of this blog entry thinking it would be easy - just come up with a list of my top 5 or top 10 favorite aircraft, write a short entry on why I like each one, and put up a few pictures. However, when I got around to trying to figuring out my handful of favorite airplanes, well, it's tough. There are so many cool airplanes, it's tough to narrow it down. I mean, really, I could just about say, go here, and you'll see most of my favorites.

So, first of all, I decided to do just airplanes - no helicopters, autogyros, dirigibles, or any other type of aircraft. It's still not easy, and I'll probably come back and look at this post later, and wonder why I didn't include certain other airplanes, but this is probably a pretty good representation. Second, I didn't include anything from Carter Aviation Technologies. I figure I'm a little biased on that, since I help design them.

Now, to describe my criteria for selecting these planes- there wasn't any. These planes aren't necessarily the best, fastest, prettiest, or most successful. There's just something about them, that for whatever reason, I just find cool. So, if you want to see what they are, just follow the link to below the fold, where they're presented in no particular order.

Continue reading "My Favorite Airplanes" »

Posted by Jeff on Friday, Aug 10 | Permalink | Comments (0) | TrackBacks (0)

Since I'm the webmaster at the company I work for, and my e-mail's about the only contact info on there short of writing us a letter, I have to handle a lot of feedback. One of the questions I often get asked is why we don't pursue a roadable version. (Yes, "roadable" is a word. Merriam Webster may not know what it means, but Wikipedia does, and Google certainly returns enough hits for it.) Indeed, it is possible to make an autogyro that you can drive on the road - consider the Pitcarin AC-35 of the past, Larry Neal's Super Sky Cycle that's currently available, or the PAL-V, that's the latest buzz, but hasn't gotten off the ground yet.

While a flying car has long been a dream that we've all wanted, there really are some practical reasons that make it very difficult. For one thing, you have to get power to the wheels, and ideally, disengage the propeller to make ground operations safer. While it's not a huge technical challenge to do this - it's just a gearbox, driveshafts, and clutches - it certainly does add weight.

For another, cars need to have much more collision protection. Aircraft designers don't worry about this because there's not much to hit in the air, but automobiles are constantly in danger of being hit by or running into something. They need the bumpers and other protection that they have. Plus, since they're more apt to smaller "collisions," like shopping carts in the parking lot, they need thicker skins to handle it (plus, a small dent to the leading edge of a rotor is a big deal - it would have to be fixed before you could go fly again, as opposed to a ding in your door, where you cuss that it happened, but just hop in and drive off). Once again, all this adds weight to the vehicle.

Thirdly, since air really isn't very dense, you need something pretty big to act on it to get an aircraft into the air - rotors or wings. You don't want something that big on an automobile sticking out into the other lanes of traffic, so you need some way to stow it, and preferrably a way that keeps it attached to the vehicle, since history has shown that people don't want to have a roadable car where they leave the tail and wings at the airport and drive a detachable car away from there (such as the Taylor Aerocar). To me, a folding rotor seems like the best option to accomplish this, but it's still a good bit heavier than a regular, non-folding rotor. Plus, you'd like to have something that stows pretty quickly and easily - have you ever noticed how many Jeep CJ owners only fold their tops up or down every month or so, even though it only takes about 10 minutes to do?

I hope you're seeing a trend here - weight. Weight is much more of a premium in an aircraft than in a car - you rarely see automobile drivers adding up the weight of passengers, fuel, and any cargo before each trip to make sure they're not over gross weight. Plus, have you ever noticed how chintzy everything seems on an airliner - it's not because the airlines are cheap; it's to keep everything light. For all the issues I discussed above, you can try your best to engineer everything as light as possible, but you can't go too far or you'll be left with a fragile vehicle. Yes, it's possible to make a roadable aircraft, but the compromises necessary add a fair amount of weight, reducing the useful load you can carry. For some people, this reduced useful load would be offset by the greater mobility, but for many applications, it's not worth it.

So, it's this weight issue that I think is the primary reason flying cars never caught on. There are a few other, smaller issues, that I plan to discuss in an upcoming blog entry, "When Will There Be an Aircraft in Every Garage?"

Posted by Jeff on Wednesday, Jun 20 | Permalink | Comments (1) | TrackBacks (0)

I'm a private pilot. I haven't been very active over the past few years, but I still like to follow the goings on, because I plan to become active again in the future. The latest brouhaha is a proposed plan to change where Air Traffic Control (ATC) gets its funding from, basically reducing what the airlines pay and making general aviation (GA) pilots foot more of the bill. Obviously, as a GA pilot, I don't like it. Flying's expensive enough as it is (the reason I haven't been very active for the past several years), and when I do fly, I hardly ever use ATC. I fly mostly in uncontrolled airspace under Visual Flight Rules (VFR). I still talk to other pilots over the radio, but ATC doesn't have anything to do with it. (For you non-pilots, it's like driving your car. You use turn signals and what not to communicate with other drivers, but there's no central authority organizing where and when you can go.) The only time ATC really does anything for me is when I'm a passenger on an airliner, and airline tickets are already taxed to cover that. So why should I have to pay more taxes than the average citizen for a service that I don't use any more than they do? You can find a lot more information on AOPA's page

Anyway, on the Ercoupe Yahoo Group I'm a member of, one of the other members, Ed Burkhead, recently made a very good post about this issue. I've copied his message below.

Any of these thoughts that get refuted buy you gals and guys won't be included in the letter I'll send my senators shortly. My preliminary thoughts on user fees are these:

1. I pretty much never use the air traffic control system except:

a. I'm affected (penalized) by it because it keeps me out of areas in greatest use by airliners (even though their use may be just a few planes a day.

b. When I do use the medium-airliner-use airports, my use of the air traffic control system is mostly because it's imposed by the government on behalf of the airliners. It's not a "benefit" for me, it's an imposition.

2. If they want to impose a use tax on people who *use* the air traffic control system, let them charge the same per-occupied-seat tax on us as they do on the airliners.

a. It may, truly, cost as much for air traffic control to handle a Piper Cub at PIA as a 747 but the cost is there for the benefit of the 747, not the Piper Cub.

b. Thus, charging per person is more equitable than charging per plane.

3. We already pay our fees through existing taxes.

a. We pay our share through fuel taxes.

b. Moreover, we pay our fair share of the airliner-protection-system through general fund taxes - as we should. The benefits of airliner flights accrue to all of us through the economic benefits of moving people and goods.

c. To disproportionately charge the people who fly on private and business aircraft for the airliner-protection-system is unfair. We all benefit equally per person from the safety of the airliners.

d. It may be fair to charge a moderate per-person fee (ticket-tax) for aircraft using the IFR system, but I think it's better to keep the current funding system.

4. As we can see from the example of Europe, imposing user fees on non-mass-transport aviation is a powerful means of killing it.

5. A strong small and general aviation industry and environment is of value to all the population, witness the developments and science developed from Weick's W-1 as well as many other aircraft developed for the personal market.

Ed Burkhead

http://edburkhead.com

Posted by Jeff on Monday, May 21 | Permalink | Comments (0) | TrackBacks (0)

Well, a fan of the company I work for (Mat Recardo is the fan, Carter Aviation Technologies is the company), just put together a highlight video of our small single place demonstrator and posted it online. I think he did a pretty kick-ass job (but of course, he had a good aircraft to show off). Anyway, here's the YouTube video.

Posted by Jeff on Friday, May 11 | Permalink | Comments (1) | TrackBacks (0)

Just a small entry for today, and I'm a few months late in getting to it, but I thought people might still find it interesting. I work for Carter Aviation Technologies, an aviation research and development company. One of our recent projects was heavily modifying an ultralight autogyro to retrofit it with some of our technologies, that we call the CarterGyro Demonstrator Trainer. To explain what we've done and how this benefits the aircraft, I'll just go ahead and quote our website.

To enable jump takeoffs, the aircraft has been modified with the Carter propeller & the two-setting Carter prop pitch control mechanism, the Carter designed mechanical pre-rotator, and the Carter rotor with automatic mechanical pitch control. For improved safety on landing, the aircraft now has the Carter smart strut on a Carter designed main gear, and a slightly modified commercially available nose gear with more stroke and a larger tire than the original nose gear.

In the current configuration, the CGD/T will fly straight and level as slow as around 20 mph airspeed, can perform zero-roll landings, and can jump over 150 feet straight into the air.

Anyway, what's so cool that I wanted to link to were the videos on the website. Follow the link above to watch them. They're pretty damn cool, and show just what an autogyro is capable of performance-wise. Keep in mind that this is an autogyro, not a helicopter. The rotor is only directly driven by the engine while on the ground when the tires can take care of the torque, and is disengaged before the aircraft lifts off the ground - you don't need any anti-torque devices like tail rotors that way. The aircraft can jump about 150' straight up just from that energy stored in the rotor.

Posted by Jeff on Thursday, Mar 15 | Permalink | Comments (1) | TrackBacks (0)

Carter Aviation Technologies has successfully demonstrated stable, slowed rotor flight. The CarterCopter "achieved a Mu of 1 at a flight speed of 170 mph and a rotor rpm of 107. The flight was stable and extremely smooth, and the pilots reported there were no vibrational indicators that they were even in a rotary-wing aircraft." (CarterCopter Technology Demonstrator Flight Test Data and Analysis). Data from the flight indicates that the slowed-rotor/compound concept does offer the potential for efficient, high-speed flight, in an aircraft capable of performing vertical flight like a helicopter. Yet there has been little funding into research on this concept, despite the huge promise that it shows.

Continue reading "Slowed Rotor/Compound Technology- Why Isn't There More Research?" »

Posted by Jeff on Thursday, Jan 19 | Permalink | Comments (2) | TrackBacks (0)

At my job, we've done some thrust testing of a propeller that I had a large hand in designing (pretty much all of the aerodynamics, and probably about 90% of the composite structure). It's a prop designed for the Rotax 582 engine. Our prop produced 16% more static thrust than the best conventional prop that Larry Neal (designer of the Monarch ultralight gyro) could find. So, I thought that was pretty good. If you want to read more about it, you can do so at the weekly update on Carter Aviation Technologies.

Update 2005-12-13 I've decided to include a picture of the prop, so that you can see how it's different from conventional propellers without having to dig through the archives of the Carter site to find a photo.

Posted by Jeff on Monday, Dec 12 | Permalink | Comments (0) | TrackBacks (0)