[#36] DesignAlternatives

Design Alternatives

The following alternatives have been considered:

Under consideration or selected layout

When selection process completes, there will be only 1 alternative remaining, other alternatives are moved under topic rejected layout alternatives. Each alternative is documented why it was either selected as a candidate or why it was rejected.

Conventional twin tractor

Trimaran tractor

This alternative looks quite much like Globalflyer. The difference is that the left and right pods have propeller
on front of them.

The configuration layout comprises of following items:

- three pods

- very high aspect ratio wing

- two tail booms, one behind each engine pod

- minimal fuselage pod, optimal fineness ratio

- the pods are connected to the wing from high wing position

- there are three landing gears in this configuration, nose gear in the center pod and main gear in the two engine pods

Open issues:

Effect of propeller slipstream to laminar flow wing behind the prop and compared to clean pusher config.

Historical examples:

P38 Lightning http://fi.wikipedia.org/wiki/P-38_Lightning
Scaled Global Flyer http://planetagadget.com/wp-content/uploads/2007/09/globalflyer.jpg

Twin fuselage tractor

The layout comprises of the followings:

- two pods

- two tailbooms

- left fuselage has cockpit on it

- right fuselage has no cockpit, but only engine and baggage space

- there are four landing gears in this configuration, nose gear for each fuselage and the main gear for each fuselage

Open issues:

Effect of propeller slipstream to laminar flow wing behind the prop and compared to clean pusher config.

Historical examples:

Scaled White Knight Two

Conventional twin tractor

"Doing it all without trying and learning anything new"

Open issues:

Effect of propeller slipstream to laminar flow wing behind the prop and compared to clean pusher config.

Historical examples:

Diamond DA42

Beech King Air

Conventional twin pusher

Historical examples:

EM-11 Orka

Rejected layouts

Tandem wing

Tandem wing pusher

Similar to Rutan Proteus. Rejected due to low Clmax and 1/2 effective span because of downwash.

Tandem wing tractor

Similar to Rutan Proteus but with tractor engines. Rejected due to low Clmax and 1/2 effective span because of downwash.

Three surface wing

Three surface twin pusher

Rejected because of complicated aerodynamic layout.

Historical examples:

Piaggio P180 Avanti

Three surface twin tractor

Rejected because of complicated aerodynamic layout.

Flying wing

Rejected because of low Clmax.

Canard pusher

Rejected due to too low Clmax.

Boom tail push-pull

Rejected due to prop inefficiency of this configuration.

Engine alternatives

Modularity is a design point in this design. The idea is that several different engine types can be used for the same airframe.

Read more about this on the ModularConcept -page.

Takeoff calculator spreadsheet was used to estimate rough gross weights for each different engine alternative.

Download takeoff calculator spreadsheet

HKS700E

60 hp
wing loading and gross weight limit has to be set so that takeoff is possible with this engine and engine failure will be no worse than on Diamond DA42 Twin Star.
Rough estimate of gross weight: 880 kg long range, wing loading 20 lbs/sqft, 750 kg short range.