Lambda Wing

[ripgoose1991]

I'm wondering what the internal layout of the MQ28 Ghost Bat wing would look like as a Lambda Wing. I understand the low RCS implication, but why is it the only UCAV which has opted for this wing shape? XQ-58, XQ-67 are all straight high AR simple.

 

[Nik]

Could still triangulate the internals ?
Or put stowage hinge-line at crease ??

 

[flateric]

Not 'only UCAV' - GA-ASI MQ-20, Scaled Model 437, Spirit AeroSystems Mosquito

 

[Suricato]

I'm wondering what the internal layout of the MQ28 Ghost Bat wing would look like as a Lambda Wing. I understand the low RCS implication, but why is it the only UCAV which has opted for this wing shape? XQ-58, XQ-67 are all straight high AR simple.

The wing of an XQ-58 is not so straight.

Kratos XQ-58 Valkyrie - Wikipedia

en.wikipedia.org

It is as written by Lockheed Martin.
A straight wing provide usually a high AR. And a high AR provide a high L/D. A high L/D gives a good range.

Lift-to-drag ratio - Wikipedia

en.wikipedia.org

As soon as the aircraft goes transsonic, the wing need a sweep angle to reduce the drag.

North American F-86 Sabre - Wikipedia

en.wikipedia.org

But with a sweeped wing, the inner part of the wing has high structural loads, especially by flying with high G numbers. And this require a lof of material and finally weight. So moving the kink more outside is a good approach, if the range requirement accept this.
Further, this maybe help against effects like the saber dance.

 

[ripgoose1991]

I don't agree that it saves weight, its structurally inefficient to break the rear spar line, and this design actually hence introduces a structural weight penalty. Despite the root being much wider in ratio to the tip.

The trade-off is a higher AR, higher cruise and manoeuvre L/D.

In regard to the Sabre Dance, the problem being the tip stalling first (far aft of the CG) causing that deadly pitch up moment at low speeds. The lambda wing might alleviate this as the root still generates lift at the same longitudinal location where the tip has stalled - retaining the balance. Wow I didn't think of this.

So you can vary the area and and AR with a constant chord. Sweep a bit more without worrying. A very flexible planform if the wing has to come off and squeeze into a container with the fuse.

 

[Jety]

I'm wondering what the internal layout of the MQ28 Ghost Bat wing would look like as a Lambda Wing.

To create the internal structure of the Lambda Wing, you can imagine the wing being separated at the cutting line. This means that two wing halves are considered. (Inner wing half and outer wing half) The rib profiles on the cutting line have the same shape. The wing spar is continuous from the root rib of the inner wing half to the end rib of the outer wing half. That's how I imagine it could be.

 

[VTOLicious]

Not 'only UCAV' - GA-ASI MQ-20, Scaled Model 437, Spirit AeroSystems Mosquito

...and EADS Baracuda

 

[Justo Miranda]

Hi

 

[Voltzz]

To create the internal structure of the Lambda Wing, you can imagine the wing being separated at the cutting line. This means that two wing halves are considered. (Inner wing half and outer wing half) The rib profiles on the cutting line have the same shape. The wing spar is continuous from the root rib of the inner wing half to the end rib of the outer wing half. That's how I imagine it could be.

EADS seems to have gone for a very different spar design on the Barracuda to allow for interchangeable wings:

The only significant metal airframe component is the centrally mounted wing spar, which passes through the fuselage to extend out on both sides by almost 1m, almost one third of the way along the wing structure and ending directly in line with the trailing-edge “crank”. Within the fuselage the spar passes to the immediate rear of the payload bay and well ahead of the engine mount.

Hunkel says the spar is derived from glider designs, intended to take the bulk of lift forces and at the same time provide a simplified mechanism for exploring alternate wing forms, including the proposed medium-altitude, long-endurance version being considered by the German air force alongside vehicles such as the General Atomics Aeronautical Predator B and EADS’s own EuroMALE system. The current configuration has a span of 7.22m with the wings produced in Spain by EADS Casa.

FlightGlobal | One step beyond | June 2006

 

[red admiral]

I wonder whether that single spar is taking torsional loads as well, or whether there are also fore/aft joints. I can't see from any of the build/maintenance photos.