I've always been fond of oddball aircraft, and the BAe 146/RJ85 is one of them. I also think the 727 is beautiful, and though the MD 80/DC9 is a bit dodgy lookin', I admire it greatly.
What I'm hear to ask is this: What are the chances that a major new jet will be designed with either aft mounted engines or a top mounted wing? Sure, you've got your CRJ-1000 in the works and Dash 8, but I'm asking about mainline jets that would be competing with the 737 or A320.
On a side note, are there any of you who could tell me the advantages/disadvantages to such a design vs a standard engine under the wing configuration?
HumfryTerminal: What are the chances that a major new jet will be designed with either aft mounted engines or a top mounted wing?
Not that much I guess... maybe in 2020s if the "open rotor" engine cocept will finally find the way in the market we will get back to the MD-80 configuration (rather than the An-70 one...), because of the rotor-ground clearance.
HumfryTerminal:On a side note, are there any of you who could tell me the advantages/disadvantages to such a design vs a standard engine under the wing configuration?
There are several PLUS and MINUS in all configurations for both design/manufacturing and for operating/maintaining an airplane:
Hi/Low wing configurations: normally the hi-wing solution gives the possibility to increase the engine clearance from the ground (see ATR/Dash turboprops or BAe146) or for operations from semi preparated strips (see C-17 or other military transport) to avoid FOD ingestion by the engine or propeller or debris lifted by nose landing gear impacting on wing or flaps. For example I've never seen "performing" or "STOL" turboprops mounting powerful engines using low wing configurations (such the one used in SF340 or J31/41 were engines are relatively small). The S2000 is an exception to this but is derived from the SF340.
You can see for example how high are mounted the engines of the An-26.
Same consideration could be made for the BAe146 where the design was quite particular (big flaps and 4 engines well separated from the wing to avoid engine exaust interfering with extended flap), the alternative for the 146, for using a low wing configuration, was probably an excessive stetching of the landing gear.
Wing/Tail engine mounting: the "clean design" engine installation is under the wing, of course for mainly two reasons: the fuel is in the wing so the easiest solution is to have the engine directly under the tank (on the MD80 you need long fuel pipes running into the fuselafe), and the lift of the aircraft is generated by the wing, so the more far you move the "heavy parts" of the aircraft from the wing , the more you need to strenth the wing fuselage attachments and fuselage design (in the MD80 style design you are adding over 4 tons at the end of the fuselage!). Nowadays turbofans are even heavier (on the MD-90 you have 5 tons...) so this solution, you understyand is more and more unpopular....
But of course the tail engine mounting has advantages as well: without engine under the fuselage you can reduce the wing clearance from the ground (smaller landing gear), and with the tail engines you lower engine-arm from centerline that allows smaller tail surface (that is normally dimensioned on "engine failure" condition at V1).
Of course there are 1000 more good/bad reasons.... those up here are just part of it...
/HAL9000
I'd say the probability is quite high. The future will see a number of radical changes in engine design:
- increase diameter for propulsion efficiency (both for ducted and open rotor)
- intercoolers / recuperators in the engine core to increase thermal efficiency
In this case, the traditional engine-under-the-wing design has many disadvantages. In addition, future stringent noise requirements will need the aircraft wings/fuselage to act as a "noise shield" and thus will require the engine mounted on top in the aft section (with wings below). It may also be of advantage to have the core engine _integrated_ into the fuselage to properly accomodate also the recuperator part and to have only the fan part outside (driven electrically or via a gear transmission).
Hi Guys;I will not go over step by step how to build this kit as it looks to be a relatively easy build straight out of the box, due to the good fit and clear instructions, and certainly nothing beyond the ability of any competent modeller, despite its considerable size. The following is a general overview of the kit and how to make an impressive kit into an even more impressive model, including correcting some inaccuracies and omissions.Thanks
Sherry
The top mounted engine concept was tried in the sixties/ seventies with the The VFW-Fokker 614. The VFW 614 is often described as being ahead of its time. It was a brave but in the end unsuccessful attempt to build and market a small capacity regional jet, a market sector that developed later with the strong sales of aircraft such as the Canadair CRJs and Embraer ERJs.
The aircraft was of unconventional configuration, with two quiet, smoke-free, but untested RR M45H turbofans mounted on pylons above the wings. This arrangement was used to avoid the structural weight penalties of rear mounted engines and the potential ingestion problems of engines mounted under the wings, and allowed a short and sturdy undercarriage, specially suited for operations from poorly prepared runways.
Even with the WFW 614 history not being succesful the future for this concept does look somewhat promising. here is what Honda has to say about their new business jet:
"Conventional wisdom has long held that mounting the jet engines over the wing of the aircraft creates unfavorable aerodynamic interference. But through extensive experimentation and testing, Honda engineers discovered an optimal over-the-wing engine mount configuration that actually achieves lower drag than the standard rear-fuselage engine mount design."
If you want to read the Honda Paper on over the wings engine mount it is available here.
Gravity always wins!