Rear engined airliners
 

As I understand a big disadvantage of this layout is the difficulty in recovering from a stall because the tailplane is masked by the wing at high angles of attack. Another, particularly on the VC10, was that the centre of gravity was so far back that the tail had to be huge to make up for the lack of leverage.

There was obviously a good reason why rear engined airliners and bizjets were never built with a canard instead of a tailplane, but what would be the downsides of this layout?

I'm sure the aerodynamics of the deep stall have been covered ad nauseam elsewhere so I will not repeat it all here.

Canards were considered, but the obvious disadvantage is that your main lifting surface can be compromised by living in the foreplane's wake.
As you can see in this diagram, de Havilland considered a rear-engined canard when scheming a trans-Atlantic mail plane in 1945, but access to the work of (inter alia) Lippisch changed all that.

http://upload.wikimedia.org/wikipedi..._106_Comet.jpg

A Comet with a swept tail would have looked rather smart !

Quote
A Comet with a swept tail would have looked rather smart !

Only if it also had both the wings swept 45 deg. as per the port one in the diagram!
Mmo around 0.90???

Deep stall was not the big disadvantage with rear engined, T tailed airliners. Once understood it was easily managed. The big disadvantage of this layout is excess structural weight. The fin has to be stronger to take elevator loads, the rear fuselage has to be stronger to take thrust loads and the wing has to be stronger to resist bending (wing mounted engines provide wing bending relief). In all these cases for stronger, read heavier. After all this the need for fuel lines to run through the fuselage was a minor inconvenience. The bigger the aircraft, the bigger the problem, which is why nobody (except BAC) seriously considered a widebody rear engined design. The fact is that Boeing got it completely right in 1952 with the design for the 367-80 and all modern airliners are built in it's image.

It's also easier to make a longer version of an aircraft with engines on the wing simply by inserting a fuselage "plug". With the engines on the tail there is only so far you can extend it before you get major issues.

Worked for the DC-9 ...

And for the CRJ - the 1000 has twice the pax load of the 100.

The BAC 1-11 was also lengthened by adding a fuselage section.

And the Caravelle too, come to that.

Super VC10 was longer too.

#5.....The fact is that Boeing got it completely right in 1952 with the design for the 367-80 and all modern airliners are built in it's image.


Well nearly right...most modern airliners have the DC-2/DC-3 pattern of just 2 powerful engines, wing mounted, fairly close to the fuselage so how important is the bending relief especially now that wings are looking skinny and 'bendy' (787)?

Two advantages for rear-mounted engines:
Shorter - and therefore lighter - gear especially with high bypass ratio engines.
Easier ground operations - less chance of equipment & personnel being ingested.

Add that the rear fuselage also has to be stronger to take weight and inertia; additionally the wing centre-section. I read somewhere in the VC10 vs 707 debate that the 10 suffered a 5-tonne penalty because of this.

I think this thread has run its course when it reached the "I read somewhere" level.
There are sound reasons for most configurations and compromises have to be made. A relevant example might be that the rear-engined aeroplane has a clean wing with uninterrupted high lift devices which is, to an extent, offset by the short tail arm requiring a higher tailplane load.

It is perhaps a little unfair to denigrate the views of others purely on that basis. We are not all a/c engineers or designers, but most of us have enough knowledge of, or interest in, the question to hold a discussion.

evansb,
Do you have any info relating to that Fokker concept? (Post #13)


It looks like an amalgam of:
Fuselage of a Boeing 307,
Wings by North American,
Tail feathers by Douglas
and powered by RR Nenes on steroids.
The apparent C/G vs C/L also looks interesting.

That is an amazing looking aircraft, evansb.

The beauty of that design is that if there is any engine problems in flight, the pilots can reach down with a spanner and fix it themselves or remove the offending bird etc.


Still, nobody has answered the important question. How fast would it have gone? :ok:

Not all that fast I'd say looking at the wing and tail design, but what I'm more curious about is, how would one load the passengers seeing that the door is not only above the wing, but the left engine as well. :p