Published

August 24, 2024

Gliders!

After reading Dr. Morton Grosser’s Gossamer Odyssey, which tells the tales of the origin of human-powered flight and first-hand accounts of the Gossamer Condor and Gossamer Albatross projects, I’ve grown more interested in gliding and soaring flight. Paul MacCready himself was a soaring prodige: the first American to win the World Soaring Championships, and multi-time winner of the US Championships.

Though I would’ve probably not bat my eye to them before, I took particular interest in the gliders of the Smithsonian. And boy were there interesting stories to be told.

Pictured to the right is the Stanley Nomad. This one has a funny story behind it. The designer, Robert M. Stanley, came up with the design during his service aboard the U.S.S. Ranger. In 1938, he completed construction of the sailplane, and took it to the National Soaring Contest. The airplane looked a bit different than it did in the picture to the right: it had a conventional, cruciform tail. After landing the airplane in a field after a cross-country flight, the tail got stolen!

As a replacement, Stanley fit the aircraft with one of the first V-Tails to be flown in an aircraft, the first to be flown in a sailplane. He recognized a few benefits, particularly the reduced drag from the reduced surface area, an increase in effectiveness from the undisturbed air outside the wake of the wing, and the simplicity of construction of two surfaces instead of three.

Stanley would later go on to break two altitude world records with the Nomad, become president of the Soaring Society of America, and chief pilot of Bell Aircraft Corporation, where he made the first flight of the United States’ first jet aircraft, the Bell XP-59. Wonderful history!

Another glider with chilling history is the Grob 102 Standard Astir III, pictured to the left. The airplane was designed by Grob-Werke GmbH & Company KG to be compliant with the Standard Class of sailplanes, adopted in 1958. This designation imposes restrictions with the intent of decreasing the cost of construction/acquisition of these sailplanes, such as a wingspan restriction of 15m, no leading/trailing edge devices, and a maximum gross takeoff weight of 525 kg.

Indeed, these restrictions put pressure that induced a more widespread use of composites and other weight-saving measures (some of which deemed unsafe, made worse by restrictions seen as unnecessary in the Standard Class, which led to further changes…)

In 1978, Robert Harris first flew a sailplane, and he was hooked. After discovering that the altitude record had not been broken since Paul Bickle flew to 14,065m in 1961, Harris set out to train for a record breaking flight.

Eight years later, on February 17, 1986, Harris was towed into the skies to attempt a world record. With five layers of clothes over his body, he started searching for lift. At 11,552m, his canopy was completely frozen, and he lost all visual reference to the horizon, flying only by his instruments. At 12,768m, his eyes would water but the tears would turn into solid ice as soon as they left his eyes. Finally, at 14,899m, his main oxygen system failed, forcing him to descend with a new world record and a lot of frostbite.

I was also completely unaware of the rich history and role that gliders played during world conflicts, namely World War 2. Nowadays, the name of the game is stealth and unbelievably small radar cross sections, but back then the roaring hum of approaching bombers would likely be as much of a tip-off as any other technology available. Additionally, gliders were the deployment method of choice for commandos operating deep in enemy lines: the deployment was quiet and, most importantly, concentrated. Whereas airborne, parachuting troops would be scattered along a large area, commandos deploying in gliders would be tightly-packed, allowing for concentrated fire power upon landing. This made gliders an attractive approach. Some were even designed to carry artillery, vehicles, and supplies.

Pictured to the left is the Frankort TG-1A. It served as a training glider to the Army’s primary combat glider, the Waco CG-4A (TG stood for “training glider”, CG for “combat glider”). A contract for its prototype and later larger-scale manufacturing was awarded to the Frankort Saiplane Company, who was already known as a glider manufacturer in the competitive gliding and soaring civilian world.

America’s results with combat gliders were mixed, and not as successful as those from the axis powers (after the war, thousands of German combat gliders were recovered, and are believed to have played major roles in the Luftwaffe). Nowadays, the roles previously served by combat gliders in war settings have been largely replaced by helicopters.

So many flying wings!

There were so many flying and blended wings in the Smithsonian - several of them Horten designs, but some other interesting ones too.

Pictured to the right is the Northrop N1-M, the first “true” flying wing from the designer (his previous ones featured vertical or horizontal tails to some extent.) The aircraft was designed as a first step towards Northrop’s vision of an all-wing bomber (a vision that proved accomplished decades later with the B-2 bomber.) Its engines were completely buried within the fuselage. Initially two 65hp, later replaced by almost twice of that, the program faced several challenges, such as controls, underpowered engines, overheated engines, etc.

The program also had the help of brilliant, field leaders. None other than Theodore von Karman helped Northrop with the design, and solved many aerodynamic and elevon-related problems during the flight test stages of the program.

This one is maybe one of my favorites - the Lippisch DM 1. Not only is it quite funny looking, but it was designed by someone quite influential in human-powered flight: Alexander WLippisch, the German aerodynamicist that was present at the early days of the soaring flight revolution at the Wasserkuppe. Lippisch encouraged many developments in human-powered flight by Oskar Ursinus and the Darmstadt institutes, students, and engineers who were involved with human-powered flight during those early days.

The aircraft never flew outside of wind tunnels, but has an interesting history. It was designed by Lippisch to investigate a potential solution to high-speed, transonic jet-powered flight: the inovative delta-wing design. When the airfield where this aircraft was being built by Darmstadt students was captured by the U.S. Army, military leadership was so impressed that they ordered the students to resume construction.

Several important figures learned of this design and were involved, or curious, about its development, including Theodore von Karman, Walter Diehl, and even Charles Lindbergh, who personally paid a visit to inspect the aircraft.

Lastly, there were general aviation flying wings too! Picture to the right (hard to see, but just above the Concorde wings) is a Mitchell U-2 Superwing (arguably just as cool as the other U-2). It is a 10m wingspan, flying wing kit plane, powered by a single small two-cycle engine rotating a pusher propeller. This kit was very popular: more than 1,500 sold in just a few years. It also boasts some impressive achievements: one pilot flew to a world record altitude in the aircraft’s class.

Mitchell also advertised an incredible aerodynamic feat: a lift-to-drag ratio of 25:1.

I’ve seen this one before!

There were also aircraft whose name rung a bell, and it took me a bit of brain-searching to remember where from.

The Westland Lysander pictured to the left is on display right at the entrance, and greeted me into the museum. It has an impressive history: it was used by England for covert missions, and much of its operational history is still unknown. It is believed to have been used as a tow plane, but also as a means of effectively injecting agents deep into enemy territory.

The name rung a bell, and it took me a while to recall where from. The planform gave it away: it is a great example of the use of a compound-tapered planform, explained in detail in Gudmundsson’s General Aviation Aircraft Design.

The planform yields two immediate benefits: it gives more lift for the same angle of attack (to the right, an example at 10 degrees of AoA) compared to a hershey-bar wing, and it promotes root stall with a highly loaded inboard root chord. However, one is left to wonder whether the structural complexity are worth these benefits versus, say, a more conventional single-tapered planform with some washout. It is also said that the LE discontinuity provides better stall handling by effectively splitting the planform into two lower AR segments

From Gudmundsson General Aviation Aircraft Design

Though the Westland Lysander is a short takeoff and landing (STOL) aircraft in order to operate in deep enemy territory, that is not due to its planform but rather due to its high-lift devices. The choice for planform was more practical: pilot field of view! The wings are mounted to the cockpit, so a smaller chord inboard section tapering outwards allowed the pilot to observe better, a key function of the aircraft.

The other “Ah!” moment was this interesting plane: the Grumman G-164 Ag-Cat. This also has interesting history: it was the first airplane specifically designed for agricultural purposes by a large aerospace manufacturer, and has been extremely successful in doing so. Some of these aircraft are still flying today, though many have been replaced by other designs such as the Air Tractors. Over 2,000 of these aircraft were built.

The answer to where I knew this one from is a bit unrelated, but a common-theme in my current endeavors: human-powered aircraft! In Gossamer Odyssey, Dr. Grosser describes MacCready’s search for hangar space to build the Gossamer Condor, eventually settling down at Shafter Airport (nowadays oficially Minter Field Aiport District). He describes the scene and atmosphere of approaching and arriving at the airport:

As you drive down the dusty, bumpy road off the Lerdo Highway wondering who flies here? the car roof suddenly vibrates around your ears with the roar of a 600-horsepower (447-kilowatt) Pratt & Whitney radial engine. You clutch the wheel and duck as a big yellow Grumman Ag-Cat heads straight at you and climbs out over the car as if someone upstairs is pulling it on a string. In light or calm wind conditions, ag aircraft may be operating from any runway or taxiway. Yes indeed.

Ag-Cats!

General aviation… but clever!

I was also impressed by some clever general aviation designs. Some funny ones too.

Battle for the smallest: picture on the right, is the Stits SA-2A Sky Baby. The designer, Robert Stits, built the aircraft as a response to a dare from another pilot in Riverside, California. Calling it the “world’s smallest”, he hired pilot Robert Starr to fly the machine. For a few months it was flown at air shows across the country, until the airplane was retired. The claim that it was the “world’s smallest” went undisputed for a long time, until Robert Starr, the man who was originally hired to fly the Sky Baby, made a claim of his own: he had built the Bumble Bee II, even smaller than the Sky Baby!

The Stits fought back: in 1984, Ray Stits’ son Donald designed and built Baby Bird, a monoplane currently at display in the EAA Aviation Museum. This aircraft is impressive: a wingspan of just over six feet!

In 2002, the Guiness Book of Records settled the dispute: Baby Bird was the world’s smallest monoplane, and Bumble Bee II was the world’s smallest biplane.

I was also familiar with several of Burt Rutan’s designs coming in, but had never seen anything other than a VariEze in person.

Pictured to the left is the Rutan Quickie. Two designers, Tom Jewett and Gene Sheehan, sought Rutan’s help with what they envisioned being a cheaper, high-performing kit with “more flying enjoyment for less money” compared to other popular kits at the time. In June of 1978, the aircraft was ready. They flew it into Oshkosh and garnered a lot of positive attention, winning the Outstanding New Design award for that year.

This is perhaps one of the best instances of “design synergy”, a concept I read so much in design textbooks, in play… so much of this aircraft just makes sense. The staggered tandem wings (officially a “canard” since the wing areas are not exactly the same) with outrigger wheels on the forward wing. I imagine the negative stagger and generous separation, helped by the “curved” OML of the fuselage, helps keep the aft wing away from the downwash of the forward wing, a common downside of tandem wings. The dihedral of the aft wing might help with that, in addition to dihedral effect for stability. Very interesting overall!

Some space stuff too!

Besides aircraft, the Udvar-Hazy also has an impressive selection of spacecraft and human spaceflight history. A major highlight is, of course, the beautiful, enormous, ingenious Space Shuttle Discovery… but another thing caught my eye.

Pictured to the right is an early idea for recovery of the Mercury capsules: a paraglider! Instead of a conventional ocean landing, the idea was to deploy this inflatable paraglider that would perform a controlled descent, glide, and landing on a paved runway. North American Aviation was the prime contractor, developing and testing the paraglider with moderate success. However, the program never became operational, and NASA opted instead for ocean landings.

One interesting thing I learned with this was that the inventor of the Rogallo Wing, Francis Rogallo, worked at NASA Langley. It is no surprise, therefore, that this paraglider makes use of that design. Rogallo Wings, most famous for their use in hang gliders, inspired the structural design of the Gossamer Condor and Albatross.

The Great Ultralights

Last but not least, of course, are the great ultralights.

Pictured to the left is the aircraft that I wanted to visit in the first place: the majestic (true to its first name) Gossamer Albatross. After reading the Gossamer Odyssey, seeing this in person was a truly incredible experience. It’s hard to grasp the sheer size of the wings from reading its dimensions on books and websites, but looking at it on display - as it sits not far from the Concord, whose wingspan falls short of the Albatross by 10 feet - puts everything in perspective. What an incredible achievement of aeronautics, manufacturing, structures, and human endurance.

I also had an erroneous perspective of the Albatross as having a “crude” construction, especially compared to the apparently more streamlined MIT Daedalus. However, that is entirely not the case after reading its history and seeing it in person. The techniques used by the Albatross crew to construct the airplane’s carbon fiber spar and torque tubes were deemed 5-10 years in the future by other ultralight and human-powered enthusiasts of the time.

The mylar coverings, even aged in time as the aircraft sits in the museum, are very clean. I am curious as to how the aircraft would have appeared immediately following a heat-shrinking session of the coverings… The propeller also surprised me, especially considering it was built by hand, almost 50 years ago… absolutely fascinating.

There is another Paul MacCready-esque mark left in the museum: pictured to the right is the NASA Pathfinder Plus, one of NASA’s early experimentations with HAPS aircraft. This one was used to research the possibility of very-long/perpetual flight powered by solar power. Many features are of interest. The distributed propellers, angled slightly downward to more directly actuate the up-turned air from the wing’s frontal upwash; the solar panels scattered throughout the wing.

It is also easy to see how directly applicable some lessons learned from human-powered flight are incorporated into such airplanes. The ribs are a prime example: it is hard to ignore the resemblance of the Albatross ribs to those of the Pathfinder Plus.

The Smithsonian had one last surprise on my way out to grab a much-deserved Shake Shack burger (and a copy of Skunk Works from the museum store): the Langley Aerodrome A.

The aircraft, pictured to the left, completely evaded my pre-visit research, so was a very pleasant surprise when I first spotted it. The designer, Professor Samuel Pierpont Langley, was moderately successful with a 1/4-scale model that flew in 1901 and in August of 1903. However, his two attempts at human-carrying flight were unsuccessful: first in October of 1903, when his assistant, Charles Manley, fell into the water along with the flying machine. In December 8, 1903 - a mere nine days before the Wrights! - he attempted the flight again, unsuccessfully yet again.

Later analysis showed that the downfall of the Aerodrome A was its structural design, partly attributed to the fact that Langley’s approach was simply to scale up some of his earlier model designs that had flown successfully. These failures marked the bitter end of Langley’s career. He was unable to get more funding and suffered some public ridicule until his death three years later.

The legendary Glenn Curtis was able to restore the aircraft and make it fly some short straight hops after the Smithsonian hired him to do this work in 1914. The model was then refurbished to its original configuration and set on display.

I learned about an interesting piece of controversy involving the Smithsonian: when the repaired Aerodrome A was put on display, it was labeled as the world's first airplane "capable of sustained free flight.” In protest, Orville Wright lent the 1903 Flyer to the Science Museum in London. It was only in 1942 that the Smithsonian clarified the label, allowing the Flyer to return to the United States, where it was donated to the Smithsonian in 1948.

Conclusions

All in all, a great visit. This is the second aviation museum I’ve been too, the first being the Intrepid in New York City. I’ve found it fun to have a piece, or multiple pieces, that I intend to see before I even visit.

After this one, I’ve received several great recommendations of other museums from friends, and am looking forward to seeing more historic aircraft. The main conclusion, however, was this: I really, really want to build a human-powered airplane.