trailing boom-mounted control surfaces

[steelpillow]

A few aircraft and projected designs had control surfaces mounted on short booms trailing behind the wing outer section. (NOTE! This is not about the outboard tail, where a single boom is on the wing tip and the tail sticks out beyond it. That deserves its own thread, not to mention an article by me in a forthcoming issue of The Air Historian).

The ones I know of off hand are:

• The early Skoda-Kauba prototypes V1, V1a and V3. These had them on spindly booms attached to each end of the surface, and used them as elevons.
• The Cornelius Fre-wing, which mounted them on a pivoting wing, where they acted as servo tabs.
• The B.Ae Kingston P.1216 proposed "Super-Harrier", and associated projects. Here the outer boom was omitted and they act as combined tail plane and wing wake conditioner.

I feel sure I have also seen a French proposal, possibly a patent drawing. Any offers?

 

[red admiral]

I'm not sure what's common between those apart from the layout as it seems all were for different reasons?

E.g. on P1216 I would have thought that a high straight tailplane between the booms a la Sea Vixen would have been preferred for structural stiffness and mass, but the supersonic flight regime precludes this due to excessive drag and control, and it's not that feasible to sweep forwards from the fins - hence the position on the outside of the booms. They ran out of other places to put them...

 

[GTX]

See here: https://www.secretprojects.co.uk/threads/boeing-flying-wing-concepts-from-the-mid-1930s.304/

 

[riggerrob]

B.Ae Kingston P.1216 is merely a variation on the tail surfaces of many modern jet fighters: F-15, Yak-141, F-35, etc. They want to install after-burners ahead of tail surfaces (perhaps for balance), so install tail surfaces on short booms extending aft of the engine nacelles/center fuselage.
The only difference on the proposed B.Ae Kingston P.1216 is the wider width between the booms.

 

[_Del_]

They want to install after-burners ahead of tail surfaces (perhaps for balance)

Provides a longer moment arm by placing the control surfaces as far away from the cg as possible.

 

[steelpillow]

B.Ae Kingston P.1216 is merely a variation on the tail surfaces of many modern jet fighters: F-15, Yak-141, F-35, etc. They want to install after-burners ahead of tail surfaces (perhaps for balance), so install tail surfaces on short booms extending aft of the engine nacelles/center fuselage.
The only difference on the proposed B.Ae Kingston P.1216 is the wider width between the booms.

That is incorrect, or at least so far short of the whole story as to grossly misrepresent the P.1216. Its wing was aeroelastically tailored so that the tailplanes twisted during manoeuvring to enhance the performance of both surfaces. Consequently, both could be reduced in size. Also, the tailplanes were far enough out to massage the wingtip trailing vortices and reduce overall drag. It's all in Mike Price's book from Blue Envoy.

 

[steelpillow]

See here: https://www.secretprojects.co.uk/threads/boeing-flying-wing-concepts-from-the-mid-1930s.304/

Boeing Model 306 added to my knowledge, many thanks! I wonder if there were any accompanying patents?

The flying boat reminds me of the Westland-Hill Pterodactyl VIII, which was similar except it had conventional inset elevons and short stabilising sponson floats similar to Dornier practice. But tailless flying boats deserve their own thread.

 

[steelpillow]

I'm not sure what's common between those apart from the layout as it seems all were for different reasons?

E.g. on P1216 I would have thought that a high straight tailplane between the booms a la Sea Vixen would have been preferred for structural stiffness and mass, but the supersonic flight regime precludes this due to excessive drag and control, and it's not that feasible to sweep forwards from the fins - hence the position on the outside of the booms. They ran out of other places to put them...

Different conceptual reasons often converge on common technicalities, when one scratches the surface. I have a feeling you are right about the origin of the idea, but BAe put a huge amount of effort into leveraging that idea and taking the design concept to a whole new level.

 

[steelpillow]

See here: https://www.secretprojects.co.uk/threads/boeing-flying-wing-concepts-from-the-mid-1930s.304/

Boeing Model 306 added to my knowledge, many thanks! I wonder if there were any accompanying patents?

Having studied the linked thread in some detail, I strongly suspect that the Boeing 306 may not be all it seems. I posted my analysis there. Hey-ho.

 

[publiusr]

I wonder if this would lend itself to launcher use…solid support bracing running through…

 

[red admiral]

What about WhiteKnight / Stratolaunch? Are they close enough to fall into this category?

 

[steelpillow]

See here: https://www.secretprojects.co.uk/threads/boeing-flying-wing-concepts-from-the-mid-1930s.304/

Boeing Model 306 added to my knowledge, many thanks! I wonder if there were any accompanying patents?

Having studied the linked thread in some detail, I strongly suspect that the Boeing 306 may not be all it seems. I posted my analysis there. Hey-ho.

Updated discussion on the linked thread: seems it was a real project after all. Hooray!

 

[Sundog]

I'm not sure what you're asking; is it "Why use twin booms, versus the standard fuselage layout?" If so, it's usually packaging, especially as it relates to propulsion location. For instance, the twin booms on the P-38 allowed all of the radiators/superchargers propulsion related equipment to be mounted in each boom. From the standpoint of internal volume, this solution allowed the packaging of all of the propulsion systems in the boom and left the wing to hold a maximum amount of fuel. If it had been a standard layout, then they would have required large nacelles to handle all of that equipment or a large fuselage to handle the components for both engines and then ducting through the inner wing section, which would have increased complexity and reduced fuel load. Also, having the two systems in separate booms meant if one was damaged in combat it was isolated from the other system. Also, a box structure can lead to a stronger tail, the penalty being higher drag, weight, and cost.

In terms of single engine designs, if a single engine pusher was being pursued with a conventional layout, i.e - not a canard, then twin booms was how you would mount the tail to meet stability and control requirements, as it is the lowest weight, least complex solution. Some German designs had the pusher prop spinning around a conventionally tailed fuselage, but I would argue that any aerodynamic gains for such a layout would be lost in added structural weight and complexity. That's not even bringing into account maintenance/accessibility issues.

In terms of the early jets that used this layout, it allowed for propulsion installation with very little duct losses at the inlets and the tail pipes. At the time, they didn't have advanced nozzles yet and duct losses were still an issue since early layouts had the powerplants placed relatively forward in the fuselage with long tail pipes. That's why the Hawker Seahawk went with bifurcated exhaust as opposed to one long tail pipe through the fuselage. Obviously, through development and testing they eventually figured out how to overcome this with the various P series upgrades of the Seahawk, eventually leading to the Hunter.