Archives for March 2016

Brian’s Blackburn

Side view of Brian's completed Blackburn

Side view of Brian’s completed Blackburn

Brian recently purchased a set of Blackburn CAD plans, completed his model and was kind enough to share the results. Executive summary:  Brian’s Blackburn looks great!

Detail of Blackburn cockpit and after servo installation

Detail of Blackburn cockpit and after servo installation

The 1912 Blackburn Type D Monoplane was one of the first aircraft designed and built by an Englishman and then flown in the United Kingdom. With its front mounted engine and aft tail surfaces, the Blackburn has a surprisingly modern layout for an aircraft conceived just nine years after the Wright brothers’ first flight.  The generous wing and control surface areas as well as the substantial nose and tail moments make for an ideal radio control model aircraft.

Front view of the Blackburn, ready for takeoff

Front view of the Blackburn, ready for takeoff

Brian’s reports that his model finished out a bit tail heavy. Brian wisely added the correct amount of nose weight to bring the model with the proper center of gravity range.  It is absolutely critical that any aircraft balance within the correct center of gravity range prior to any test flights.  A model will be uncontrollable if flown with a CG out of limits as there is simply not enough control authority to override the resulting uncommanded pitch changes.

Top view of Brian's Blackburn showing rigging and ample wing and tail areas

Top view of Brian’s Blackburn showing rigging and ample wing and tail areas

As to why the model came out tail heavy, there is no certain answer. What I do is to always attempt to “build in lightness” as I construct the model.  I try to employ the lightest weight balsa for any fuselage structure aft of the cockpit, to include the tail surfaces, to minimize the possibility of a tail heavy aircraft.

Nice job with simulated spoke wheels and landing gear arrangement

Nice job with simulated spoke wheels and landing gear arrangement

Sometimes, despite your best efforts, a model will come out slightly tail heavy. One of the reasons I selected the Blackburn is the generous nose moment (distance of the propeller to the center of gravity) to make the most use of any weight added to the nose to move the center of gravity into the correct place.

Custom built foam carry case

Custom built foam carry case

The slight added weight for Brian’s model (about five ounces) should have no appreciable impact to the Blackburn flight characteristics. The full scale Blackburn had ample wing area, as the aircraft of those initial days were woefully underpowered due to the early state of aviation engine technology.  In a sense many of these early flyers were powered gliders.

This plentiful wing area makes the addition of some extra weight essentially not noticeable. The added mass will likely make for a smoother flying aircraft in the end.

Detail of custom built foam carrying case for the Blackburn Monoplane

Detail of custom built foam carrying case for the Blackburn Monoplane

Brian also took the extra step of constructing a custom designed foam carrying case for his Blackburn. As per the plans, the Blackburn’s wings friction fit into metal tubes mounted to the fuselage.  This makes it a snap to disassemble the model for ease of transport.

Brian did a superb job of tailoring his foam carrying case for the Blackburn. This is a great idea I had not thought of, and I will for sure employ this approach for future model aircraft designs.

Brian, thanks again for sharing the photos of your finished aircraft and carrying case.  Good luck with the test flights!

 

 

Kit Bashing and the Dreamlifter

Korean Air B-747-400 touching down

Korean Air B-747-400 touching down

A great way to begin with radio control aircraft design is to “kit bash” a model made from a kit or set of plans. The idea behind “bashing” is to make simple changes in an aircraft’s shape and dimensions such that the overall flight characteristics will not change yet you have a plane that differs in appearance from the original version.

Bashing does not require drafting skills as you can eyeball the various changes. Examples would be changing the shape of the rudder and fin, perhaps lengthen the wingspan or add an upper deck.

Singapore Airlines B-747-400 on landing approach

Singapore Airlines B-747-400 on landing approach

As a general rule it is acceptable to change a control surface outline if you maintain the same surface area. Same goes for the wing.  For example you can increase the wing span without any harm to the flight handling characteristics.  On the other hand you could run into problems if you reduced the wingspan, as the smaller wing area would now have to support more aircraft weight per square inch.

Side view of the Boeing Dreamlifter

Side view of the Boeing Dreamlifter

Once you bash a few of your models it is a logical next step to consider designing an original airplane of your own!

Believe it or not, “bashing” occurs in a similar vein with full scale aircraft. The changes could be a simple as adding a canopy to an open cockpit homebuilt to a fuselage stretch of a jet airliner.  Perhaps one of the best examples of “bashing” a full scale aircraft is Boeing’s B-747 Dreamlifter.

Swing tail assembly on the Boeing Dreamlifter

Swing tail assembly on the Boeing Dreamlifter

When Boeing designed their new B-787 Dreamliner, ANA (All Nippon Airways) was one of the initial customers with an order of 50 aircraft. As part of this initial launch ANA built the wing for the B-787.  Fuselage production was also planned for the B-787 in Italy.

Boeing was faced with the problem of how to safely get these very large sub-assemblies to the Boeing factories in Washington and South Carolina. It would have taken up to 30 days to ship these items overseas via cargo ship and rail.  There was debate if this would even be a feasible approach due to the huge size of the assembly.

Boeing Dreamlifter taking off

Boeing Dreamlifter taking off

Boeing’s solution was to “bash” a B-747-400 to allow carriage of the fully assembled B-787 wings and fuselage sections. This entailed detailed engineering studies that created the Dreamlifter.

Four of these huge cargo aircraft exist and they are used solely to fly B-787 sub-assemblies from Japan and Italy to the United States for final assembly

The Boeing Moscow office did some of the initial Computer Aided Design work for the enlarged fuselage with a Spanish company devising the swing tail. Modifications of the B-747-400 were completed in Taiwan.

At 65,000 square feet the B-747 Dreamlifter’s cargo hold is the largest of any aircraft in the world, and three times larger than a B-747-400 freighter.

Interestingly enough, even after all of these changes the Dreamlifter flies much like an unmodified B-747-400.  Pilots who are type rated in the B-747-400 are fully qualified on the Dreamlifter with no special FAA check ride required.

There is a lesson to be learned here that with this amount of outline and fuselage volume changes to the Dreamlifter with minimal impact on flight characteristics, the same approach can be applied to changes with our radio control model aircraft. Go ahead and give it a try!

 

Workshop Progress

New modeling workbench under construction

New modeling workbench under construction

It has been a busy time here at our new house. Mesa flying is going very well. I now have 540 hours flying the CRJ-700 aircraft for United Express out of Dulles Airport. Still a few more snowstorms and March winds to dodge in the northern states, but a great learning experience.

Shelving installed in the rear of my new workshop

Shelving installed in the rear of my new workshop

Workers are making tremendous progress with our basement refinish, and most importantly with the installation of my new workshop. The bench, pegboards and shelving are all in place. Paint is being applied with further finishing details to be completed over the next few weeks.

My new modeling work area will allow me to build a much wider range of larger and more complex electric radio control model planes. In addition, the flying weather in Georgia will be a lot more hospitable as compared to the ever-present wind in the Chicago area.

More to follow as the basement upgrade is completed, I unpack my boxes and start on my next building project!