Before the poll goes up to vote for the winner in the Retro Airliner Design Contest, I thought I’d share some of the thoughts that led to the Empress 400 looking the way it does.
Since I chose to explore the 3 Lifting Surface Configuration, utilizing a front wing, main wing, and a horizontal tail, the airplane certainly has some of the look of a Piaggio P180 Avanti. However, there are significant differences when you compare them more closely.
The fuselage on the Empress 400 is heavily ‘pinched in’ behind the wing. Now, since I didn't actually go to aeronautical engineering like I was supposed to back in 1979, I can’t tell you with any degree of certainty that the shape as shown is completely practical. Tho there’s info out there that suggests that this shape concept is great for drag reduction. One thing it does do that’s similar to the P180 is that the fuse is widest just before it begins to reduce. But again, The Empress has the reduction exaggerated. The fuselage is also symmetrical above and below a centerline, and left and right of a centerline. It's not round tho, but rather an oval.
The twin vertical fins is a big difference. They are used for a variety of reasons… to get the vertical surfaces in the prop blast, to lower overall tail height, to provide redundancy, and to reduce stress on the aft fuselage (I might be full of hooey on that last thought, I need to confirm it with the engineering dept : )
The wing is mounted on top of the fuselage primarily to get the really big props well off the ground. This greatly reduces potential FOD issues and also puts them high enuf that people couldn’t even be hit by a spinning prop. The high wing also makes every window seat have a really great view of terra firma below. Lastly, the high wing means the main gear has to move to the fuselage, which means it's much more compact than the really long gear on a low wing aircraft with extremely large props.
The slightly forward swept main wings are another difference. That’s to keep the wing attach as far aft as possible while moving the wing’s effective center of pressure forward where I seem to think it should be. Note: it’s vitally important here that you remember that I may only know enuf aerodynamics to get myself in trouble! Ultimately this is me doodling out some thoughts on what I think is an interesting idea. After some serious engineering evaluation, this airplane might look a lot different. But hey, you gotta start somewhere. Anyway, the wing attach is as far aft as possible to minimize the obstruction of the spar carry-thru in the passenger cabin.
The horizontal tail has some dihedral to get the vertical fins up and out of the way so that an over-rotation would drag a skid on the fuselage and not damage the fins.
The front wing has flap like surfaces that are used to keep the lift balanced when the main wing flaps are extended. The main wing flaps could be specifically designed to take advantage of the thrust from the inboard engines. Might be able to get some decent thrust vectoring out of a good design… sort of a poor man’s C-17 concept.
The 2+2+2 seating in the main cabin area is essentially the same as I showed for my LTJ 100 cross section concept. The middle seat that you have when you put 3 seats across is a really bad idea for passenger comfort. By putting 6 seats across, but with 2 aisles, you dramatically increase comfort, and the ability to move around the cabin. In fact, this would be even nicer than real ‘wide-body’ aircraft because they typically have 7 to 9 people per row which means more people potentially wanting to use those aisles.
The seat width as shown is one of the most important elements of the entire aircraft. The seats in the main cabin are 24” wide! The aisles are also about 24” wide, so this airplane is specifically designed for comfort. In fact, this cabin is about as wide as the 787, but the cross section is an oval so it’s not nearly as much structure overall. Behind the seating is room for an aft galley and restroom (yeah, I know we’re supposed to call it a lavatory, but since I was a kid I thought that was a dumb name for it!)
The first class cabin is much more roomy of course, and due to the narrowing fuselage shape, it would feel a bit like the 747 first class. Between the first row of seats and cockpit would be a forward galley and another restroom.
The main cabin doors are mounted between first class and the main cabin on both sides. This makes for a good primary emergency exit location and it also means the poor people (like me) that are headed for the back of the airplane don’t have to walk thru the opulent first class area to get there! There is also that sweet airstair at the back of the aircraft to allow for easy ramp loading of passengers, as well as provide another emergency exit. I have other emergency exits in mind, but won’t discuss them now.
I give all these details so you can at least see that I have done a lot of thinking to get where I’m at with the concept. And in my opinion, most all of this makes some interesting sense. The whole premise here is to consider if there’s any merit to the idea of modern, high technology radial engines in the 3,500 to 4,000hp range being developed for use in such an aircraft, with an intended cruise speed of 400 mph. I’m sure most people would say it makes no sense at all.
But I think it’s an idea worth thinking a little more about. My gut feeling is that these engines would be boatloads cheaper to manufacture than high temperature turbine engines, turbofan or turboprop. Whether they could be operated reliably and affordably is a big question, but, even tho the concepts for internal combustions engines haven’t changed much at all in the last 100 years, the details have changed a lot, especially in the last 30 years. That’s why I think it’s all an interesting question to ask.
As I’ve said before, my small, non-scientific poll from last year indicated more than 80% of people are willing to slow down to 400 mph if comfort was significantly increased. I know there are a lot of factors involved in the economics of air travel, and most of them I probably don’t know, but the bottom line is it takes less energy to go 400 mph than it does 550 mph.
So, anyone interested in dreaming a little with me?
Wednesday, April 21, 2010 at 04:43PM 
