A Day with John Dyke and the Delta Flyers
By Anthony J. Liberatore, EAA 99484, firstname.lastname@example.org
While interviewing John Dyke for an article on his Dyke Delta, it became apparent that there was more to the story than just a unique airplane; it was about John’s inventive spirit and the creative spirit of Dyke Delta builders that struck me. As John noted with regard to his years associated with both his aircraft and plans sales, “A lot of human interest stories goes into this stuff.” He also revealed that this spirit, and its roots, goes back to his childhood.
Since his teenage days, John has been tinkering with things. “All the time I was growing up I was making something - something to make something easier.” Stuff like taking the two-stroke Maytag washing machine motor (engine) and adding a propeller to it to assist in pushing a wheelbarrow that used to transport chicken droppings. The same motor was then re-used, sans prop, to process corn.
John’s creativity did not stop him from trying to fly out of a window, via cardboard wings, as a kid either. At the age of 14, John “rebuilt” a Ford Model T into what one would call a dune buggy, but long before that term entered the dictionary. “All designers have some element like that. You don’t go to college to train to become a designer; you have to be a designer to start with. You have to have a designer’s mentality. I always had a Buck Rogers mentality, not that I studied Buck Rogers,” John said. It’s this forward thinking that led John to give a speech to his high school class on how man will go to the moon via a rail launch system. The launch system was different, but 20 years to the day of giving his speech, America landed on the moon.
When it comes to aircraft design, John is a proponent of testing and measuring data. He did a great deal of work with scale models in the design phase of the Delta as well as in-flight tuft testing of his prototype, N555A. John noted why it is good to ascertain whether a change does any measurable good by the following example: In the 1980’s, a doctor from Arkansas built a Delta with winglets and it flew a couple hundred hours before being donated to an educational institution. The owner/pilot noted this particular plane’s ability to get out of small strips, but a before-and-after comparison was never made since the airplane had never been flown without the winglets. It was hard to get a handle on what the improvements truly were.
Dave Williams’ Delta in the Homebuilt area at AirVenture 2008 - a stunning example.
The Dyke Delta
During our conversation, John shared a couple of design elements of his Delta. The airfoil shaped center section (cockpit) not only contributes greatly to the Delta’s overall lift, but it has a humorous side effect that lets you know it’s working. John said that when he was younger and had considerably more hair, a slight canopy leak would suck his hair up into the crack! In fact, it was pronounced enough to hold a pencil in flight resting on the canopy seam.
John discussed a design element that the casual observer may not notice. Aft of the center section, the elevons have about 45-degree relief on them at the center-section. Other than to allow for control surface clearance for movement, why the chamfer? John notes that it has been proven out in flight via tuft testing that these chamfers allow for the high pressure underside air to meet up with the low pressure from the wing and center-section to reenergize the flow in this region.
Looking closely at the region where the vertical stabilizer intersects the wing at the trailing edges of each surface, a sharp eye can detect a triangular void created by some slight filleting of the intersection.
Here’s a closer view of the reenergized region.
John’s fertile mind is still going strong at 78. When I asked him about the trend of some designers using low pitching moment airfoils, and if it would it work on the Delta, John responded, “I often thought about using an M6 airfoil. The M6 would be interesting if someone built a Delta like mine but using the M6 instead of the symmetrical and see what the difference would be. But here is where experimentation runs amok, you can just keep running experiments until you die.”
On our way to his home airport, I asked John where the next generation of inventors would come from. He is concerned, especially with kids being so into video games and the limited shop class related activities available in schools today. At that point I ran a wild idea by him - with its large interior volume, could a configuration such as the Delta utilize gaseous fuels? John said it’s possible, but then he noted that as a teenager, not only did he re-build the aforementioned Model T, he also converted it to run off the natural gas that was a by-product of the small oil wells in his farming community! Where can we find kids doing this type of stuff as we near 2010?
John with his historic creation.
At the airport, John rolled out N555A, the prototype of the JD-2, for photos, which was in a partially disassembled state for maintenance. John was almost complete with the maintenance, and shortly after our interview, 55A was flying again. With many flight hours (more than 2,000) 55A may be one of the higher-time homebuilts. John will readily point out that it’s a prototype, not a show plane, and as such he is reluctant to take it to air shows these days even though the Dyke Delta community encourages him to bring it. The patina it wears is one of a rich history. I asked John if I could sit in 55A and he said yes. I was struck for a moment about what I was about to do. This is not just any airplane; it is a reincarnation of the remains of its predecessor, the 2 seat JD-1 that was destroyed in a hangar fire in June, 1964. 55A, John, and his late wife Jenny were fixtures at EAA fly-in’s since 1962, whether they flew in or towed it across many thousands of miles with its folding wings and roadable gear. (See the three-view line drawing) This is not just an aircraft but a piece of aviation history, and in a sense, an EAA treasure given all the folks that have taken rides in 55A over nearly half a century.
Walking around the airframe, again you can see John’s inventor spirit at work. One modification not shared yet with the Delta community is the main landing gear doors. With its aft-swinging wheels connected via a torsion rod-type gear, the door closing mechanism is very simple and clever. An aft facing sickle-shaped piece of flat stock is attached to the main gear leg, and as the gear retracts aft, it catches under a flat rubber strap about a ¼-inch thick. As the gear continues to swing aft, it pulls on the strap and swings the gear door closed with it. John notes that these doors do not seem to have any effect on cruise speed; however they are good for a 100 feet per minute increase in climb rate. The Dyke Delta community’s “unofficial” historian, Jim Maher, also noted on the more failsafe nature of John’s new gear doors. One Delta builder designed and developed a more elaborate design only to have the doors hang up on him, thus preventing the gear from extending, which resulted in an emergency belly landing. While checking out 55A’s gear doors, John pointed out yet another unshared feature. The disc brakes have been modified by John to fit the landing gear/axles in a compact fashion.
Main landing gear, note the compact brake assembly.
Doing a further walk-around, John pointed out another modification incorporated on 55A; its leading-edge wing-cuffs. John notes that they lower the landing speed by 10 mph. He also says they allow for a slower airspeed in climb, with the same climb rate, but at a steeper climb angle. John noted when building 55A that the left wing may have been a bit out of rig and the plane always had a bit of a heavy left wing, so he added an extension to cuff on the left wing to cure it. John has been flying with the leading edge cuffs for more than 10 years, but he has not released them to the Dyke Delta community, citing he would still like to experiment and maybe design a better setup.
As with many designers, John is reticent of changes being made to his design by builders, especially given the Delta’s unique configuration. However, one modification that preceded John’s most recent approved design change is a small “T-tail” of which John has made plans available to the Delta community. A number of Delta’s have flown with this trim device, and there have been a few different iterations and installations prior to John’s approved version. Jim Maher (current newsletter editor and Delta builder) notes that his Dyke Delta has an earlier trim design, (which can be seen in this photo) that acts as a set of flaps on landing by changing the angle of attack on approach, unloading the elevons for greater control and a lower approach speed of some 10mph. John’s T-tail Trim design is the lightest - in the area of eight ounces - for mass balancing per side, instead of some 8 lbs!
If you look at the underside of a Dyke Delta you will notice a centerline down the fuselage, and an almost uninterrupted wing surface out to the wingtips. With that in mind, Jim Maher also notes the following about the flying characteristics of his Dyke Delta: “It is very stable. Almost like a boat with a deep-vee hull, cutting through the water with its inherent built-in dihedral.” In turbulent air, he notices no rocking in pitch, roll, or lift and drop, which makes for a very stable platform, in his opinion.
As a friend of John’s commented to him about Delta builders in general; “These guys are mavericks - like you are - and they want to express themselves in new ideas.” But John shows a practical side to his inventive spirit, noting his desire to fly as well. “I was a new idea-type person, but I also wanted to fly! I had drive, drive to fly. Naturally I wanted to work on my ideas, I enjoyed working on them, and building and developing things, but the end product is to do something with it, like going flying.”
Dave Williams, who’s magnificently restored Delta has graced the cover of EAA Sport Aviation, is one these mavericks with an innovative nature. Prior to restoring his Delta, he built an unusual vehicle - an 18-foot hovercraft. Although only a cosmetic change, a leftover mahogany vernier from the hovercraft project was used for the beautiful instrument panel overlay on Dave’s N18DW.
Dave Williams’ beautiful mahogany instrument panel.
Dave sums up John’s, his, and the Delta community’s passion like this: “John Dyke is the leader; of course and we have a website. As you know, we debate, sometimes in a ruckus way, but it's just the way it is - it’s ok to state your point; just be polite about it. Most Delta pilots/builders are a bit out-of-the-ordinary people anyway. They take on something that looks like a challenge and get on with it, and that is a good thing because there is a lot of creativity in people like that. It is fun being around them because you hear different ideas and get different thoughts. That is what EAA is all about, the right to experiment. It brings some of the most creative people in the world together at every air show.”
Many thanks to John Dyke, Jim Maher, and to Dave Williams for their time for these interviews and the hospitality extended to Pat Panzera and me at the Dyke Delta gathering at Oshkosh 2008.