The centerline thrust concept with one engine pulling while the other pushes is nothing new. Cessna built more than 2,000 Skymasters between 1963 and 1980 and the push-pull twin still has many fans. But the Skymaster, though its design was focused on engine-out ease of flight, came along at a different time. The Skymaster was pushing uphill against a large fleet of conventional twins at a time when the industry believed that all twins were safer than singles, particularly at night, over rugged terrain or in instrument conditions.

Now, it’s a different environment for the piston twin. Insurance companies, and many pilots, assume that a piston twin is more risky than a single unless that twin is flown by a pilot of extraordinarily high experience, and one who receives regular recurrent training. The piston twin is the bad boy of perceived safety these days, while the Skymaster was simply, as all prophets must be, ahead of its time predicting attitudes that were to come. You will still need a multiengine rating to fly the A500, but it can be restricted to centerline thrust only so you won’t need to go through all of the Vmc control demonstrations and other engine-out maneuvers that just don’t apply to this airplane.

Back in 1998 Rick Adam correctly identified the need for a new type of twin if the typical pilot was ever going to have a chance to move up from a single, and the A500 was born. Centerline thrust with its total simplicity of engine-out flying qualities puts the question about pilot capability and experience to rest. And Rick also thought the time was right to transition to an airframe made from carbon fiber instead of aluminum or the less costly but heavier fiberglass some other manufacturers were using.

Rick is an experienced pilot with lots of time in turbines as well as pistons, and he feels most comfortable with a second engine, particularly since he has spent much of his time flying over the hostile terrain out west. But he also understood that 350 hp is the practical limit of piston aircraft engines at this time, so if cabin size and performance were to be increased, the power of a second engine was necessary.

What Rick didn’t grasp-and nobody else has-is how complicated, even overwhelming, a job it is to design and build an all-new airplane, and a new airplane manufacturing company, all at the same time. Adam expected the A500 to be in service five years ago, but just now the airplane has won approval for pressurized flight to its ceiling of 25,000, operating air conditioning and workable avionics. The basic airplane has been “certified” for more than two years, but that time has been needed to complete work on winning approval for the full flight envelope.

Burt Rutan was a consultant for Adam on initial design work for the A500 and you can see his influence. The twin booms sweeping up to grasp a horizontal tail between them, the slender 44-foot wing, and the pod type fuselage are all elements Rutan has used before. Tail booms are almost a necessity for a centerline thrust twin to allow space for the rear propeller, and getting the horizontal up and out of the prop wash reduces overall vibration and stress on the tail. The booms provide a handy place to locate the main landing gear, and the fuselage shape is ideal for containing pressurization loads.

The ramp presence of the A500 is dramatic. It’s a big airplane that sits high off the ground. The wing is a foot longer than Piper’s Malibu and Meridian, the wingspan kings before the A500. And the Hartzell propellers are aggressively swept, giving the airplane a powerful appearance at rest.

The carbon fiber construction yields very smooth surfaces that are, of course, free from skin laps or fastener lines. But the first complete production A500, serial number seven, is still rough around the edges. The company acknowledges that it has details to work out to make fairings and access hatches fit as they should. To this point Adam has been a development company and is now working very hard to transform itself into a manufacturing company. It has the FAA production certification so the big things are all being done correctly, but Adam is now concentrating on the dozens of little things that make an airplane look right.

The engines are twin turbocharged and intercooled Continental TSIO-550s rated at 350 hp each. Continental provided a great deal of guidance on engine installation and cooling, and those issues are not a problem.

Adam made an interesting pressurization design choice that was not obvious, at least not to me, but makes a lot of sense. The airplane taps cabin pressure air only from the forward engine turbochargers. Using pressurization air only from the forward engine saves a great deal of complexity, and thus cost and weight. If the forward engine fails you descend. Actually, you are not going to stay at 25,000 feet on one engine in any case because not enough thrust would be available. And the cabin leak rate is low enough, combined with a prompt descent, that there is no concern about hypoxia, any more than there would be in an unpressurized piston airplane that experienced a failure of its oxygen system while flying at 25,000 feet.

The rear engine is assigned the task of turning the air conditioning compressor. Again, this simplifies the plumbing by keeping the air conditioning equipment in the rear of the cabin, while the pressurization lines and connections are forward.

The A500 cabin is bigger than other six-seat piston airplanes. It’s a full foot wider than the Baron cabin and nine inches longer. The A500 cabin is a couple of inches wider than the Malibu, but several inches taller. One issue with the A500 is that the wing spars intrude into the cabin floor. Most recent designs place the fuselage on top of the wing and its carry- through spars.

The A500 avionics package has been in transition but now with production rampup has settled on a three-tube Avidyne Entegra flat glass display system, with S-Tec autopilot and Garmin GPS and other avionics. The airplane is fully approved for IFR and night flight.

The pilot seats are easy to access with the cabin airstair door ahead of instead of behind the wing as it is in other cabin-class pistons. The cockpit is roomy enough for comfort, and the panel is modern looking with its big glass displays and sidestick controls. The engine and propeller control levers are arranged in the normal way with the left set of levers operating the forward engine. It seems natural to me that the left levers would be for engine number one, even though number one is in the nose instead of on the left wing. In any event, that’s how Cessna did it with the Skymaster.

As in all airplane development programs, the A500 has gained weight. The airplane I flew, serial number seven and the first with complete systems, had an empty operating weight of 5,460 pounds with a maximum certified ramp weight of 7,050 pounds. Four years ago empty weight was expected to be 4,200 pounds with a maximum takeoff weight of 6,300 pounds. Some of the weight gain came from the unanticipated little things that add up to a lot when the airplane is complete. But some of the empty weight can be blamed on too much unusable fuel which is now at 30 gallons, the weight of a full-size passenger. Adam expects to trim that down to five gallons per side with more testing to show that the fuel is in fact usable even in uncoordinated flight.

With about 175 gallons of the available 230 gallons in the tanks, and two onboard, we were close to the 7,000 pound maximum takeoff weight, though after taxi we would be down to somewhere around 6,950 pounds for the actual takeoff weight.

It makes sense to start the aft engine first so that you can hear it respond even though you can’t see the propeller. The starting techniques are typical for any big turbocharged Continental, and the engines fired immediately.

The A500 has a castering nonsteerable nosewheel, which is odd in this size airplane. I found it natural and easy to taxi using differential brakes-though I did keep trying to lead a turn with an engine as in a normal twin, to no effect, a habit experienced twin pilots will need time to break in the A500-but on a long taxi with a crosswind a lot of brake pressure, and thus brake heat, would be needed. The company will probably add nosewheel steering in the future.

It was a hot day at Adam’s home base on Centennial Airport near Denver, but the initial acceleration and takeoff roll were surprisingly quick given the airport elevation and our maximum weight. I needed about two seconds to be comfortable with the sidestick control after rotation. The forces are on the heavy side so you need to keep the airplane in pitch and roll trim. As with all sidesticks, the left roll input is where I notice the effort most. Pushing the hand, wrist and forearm away from the body is not a natural motion, particularly for a right hander operating the side stick with his left hand.

Initial climb rate was around 1,000 feet a minute, even though we were starting from a density altitude of nearly 10,000 feet. And the A500 held the rate well as I climbed toward its certified ceiling at FL 250. There are only three recommended power reductions on the way up, and in 29 minutes we were level at 25,000 feet. I was most impressed by the smooth and cool engine operation. Both engines remained within a couple degrees head and oil temperature of each other, and always comfortably in the green. Pilots with memories of hot rear engines in Skymasters can put them to rest with the A500. To get two engines mounted on wings to operate that uniformly would be a challenge, but to accomplish it with fore- and aft-mounted engines is truly remarkable.

At FL 250 the air temperature was 21° C above standard and, with 20 gallons per hour going through each engine, the A500 showed a true airspeed of 208 to 210 knots. I could have shaved two to four gallons per engine and slowed down to 190 to 195 and been able to stretch out the range. We descended to FL 220 where the A500 hits its top airspeed and saw 220 knots true on 44 gph total fuel flow. In the early days of the program Adam had hoped for a top speed of 250 knots, but that was with an airplane weighing considerably less and a program full of youthful optimism. The reality of 200 to 220 knots for an airplane of this size is pretty good.

The A500, as many airplanes do, had a problem with rolling off at the stall, particularly in the so-called “accelerated” stall test where speed is decreased at five knots per second. The solution, which is also a popular one, was to add drooping leading edge cuffs ahead of the ailerons along with vortex generators. The drooped leading edge operates at a lower angle of attack and thus continues to fly while the wing inboard of it stalls, so the ailerons remain active and effective through the stall, allowing the pilot to counteract any roll off. The vortex generators create a high energy wake that helps keep air streaming aft at high angles of attack instead of tumbling off in a span-wise flow that can reduce aileron effectiveness.

I stalled the A500 with no aileron or rudder input and it sort of mushed straight ahead. Even with the stick held full aft the airplane showed no tendency to roll at all, so the wing design is clearly a success.

Landings will be one of the greatest delights of an A500 pilot. The airplane has very long stroke trailing-link main landing gear and very powerful pitch stability, so it is extremely easy to put the airplane in the landing attitude and let it roll on. The greaser will be the typical A500 landing, which is great for the ego.

Adam hopes to begin testing to earn flight into icing condition approval this winter. The company had initially planned to install a weeping wing TKS ice protection system, but will probably go with inflatable deice boots, as it plans to on the A700 light jet. The windshield, propellers and pitot tubes are heated electrically.

The A500 is what I would call a specialty airplane for the pilot who wants the redundancy and performance of a twin, but is uncomfortable with or lacks the experience to be insured in a conventional twin. And it’s also for the pilot who simply wants a pressurized piston twin that is less than 22 years old. The last of the pressurized twins from Cessna, Beech and Piper rolled out in the mid-1980s and since then the only choice for piston and pressure was the Piper Malibu/Mirage single. At $1.25 million the A500 is not cheap, but the Mirage comes in at nearly $1 million with one less engine, and the Meridian at nearly $2 million is the lowest priced turboprop single.

For Adam the A500 is important because it is the company’s first airplane, and to pave the way for the A700 jet. Adam says about 65 percent of the airframe components are common to both airplanes, and even a higher percentage of the suppliers are the same. The lessons learned in developing the A500 will help push the A700 program along immeasurably.

Adam is under totally new management since founder Rick Adam retired earlier this year, and the new team is focusing its energy on developing production methods that can take much of the man hours and cost out of building both airplanes, while at the same time attacking issues of cosmetic quality. It has taken 15 months to build the first few A500s, but the goal is to shrink that process to 14 weeks. Adam is building subassemblies in Pueblo, Colorado, and will soon begin final assembly of A500s, and then A700s, in a new facility just completed in Ogden, Utah. Adam has raised more than $200 million dollars in the capital markets in the past year and has the funds to see its way into volume production.

The post Adam A500 appeared first on FLYING Magazine.

Maybe “tandem twin” can be made to stick. Whatever, Adam Aircraft has created a twin built mostly of composites that looks back a bit but that is all new and optimizes the concept of the tandem twin, the power available and the current technology.

The airplane pictured and flown is the second Adam A500 built by the company. (Scaled Composites built an initial proof-of-concept airplane that looked similar but really wasn’t.) The first Adam-built airplane has been retired to static test, and flight testing is continuing with this second airplane. A third airplane is now being built and may have flown by the time you read this. The third airplane will be the first to fully conform to production standards.

A lot of people have seen the Adam A500 at airshows, in a crowd. The airplane has a different personality when you see it alone, in a hangar or on a ramp. Everyone agrees that it looks bigger. It is. With a 44-foot span, 36.7 foot overall length and 9.5 foot height, it compares dimensionally with a Cessna 421 and is substantially larger than the four-seat Cessna Skymaster. The size is enhanced by the fact that it has more pieces than a conventional airplane. The booms are large and gracefully shaped as they arch up to the horizontal tail, which is high above the power pulses from the props. The tail is quite shapely and couldn’t have been as nice had the airplane been made of metal.

The wings are nicely shaped, too, and have removable leading edges for access to control cables and TKS deicing components. The horizontal tail also has a removable leading edge. The TKS system was recently chosen as the ice protection for the airplane after Adam considered deice boots and other ice protection technology.

It apparently made more sense for the control surfaces to be metal, so they are. Different things affect designs in different ways because in transport airplanes a first move to composites has been in control surfaces.

The airplane I flew had a removable door with no hinges and no steps. It was not pressurized and may never be. It did not have nosewheel steering as the production airplane will have. Nor did it have cabin heating or much of an interior. The two seats installed, in the cockpit, were fixed, not adjustable. The airplane was being operated as an experimental, approved by the FAA for market survey work but restricted to day VFR conditions.

The two A500s have flown more than 200 hours, but there is much flight testing left to be done, and the FAA will want data from testing with the fully conforming third airplane. The airspeed envelope had been examined out to 180 knots indicated airspeed, which is well within the green arc on this particular airplane. Airspeed limits will be established in the final testing phase.

Boarding the Adam A500 is currently done with one of those three-step ladders, just like the one that I carry around so I can look in the gas tanks and that my wife likes to use boarding our P210. The production airplane will have an airstair door. The door opening is large and the cabin is entered just aft of the cockpit. With no seats, the cabin looks huge and promises to offer luxurious seating for four in a club arrangement.

The flight deck is spacious and, because the fuselage is wide, elderly or portly pilots won’t get a cramp in the old tummy trying to wedge in there.

The instrument panel is conventional. The circuit breaker panel is to the left, and many breakers on this airplane are banded because of equipment that isn’t installed or operational, such as ice protection and an autopilot.

The instrumentation is conventional. Adam plans to evolve to a glass cockpit, but for now the concentration is on certifying the basic airplane.

The power controls appear to be low on the panel compared with other twins, but the controls come naturally to hand, so the location is fine. The left controls are for the front engine, the right for the rear.

The panel is a little farther forward than most. Somehow a panel farther away is easier to scan than one that is right in your face. This one seems especially spacious because of the generous width of the airplane.

The panel’s most wonderful feature, though, is that there is no control wheel jutting out of it, taking space and obstructing the pilot’s view of the panel. The Adam A500 is flown with a sidestick, which is being embraced in most of the new-design airplanes and which is a great way to fly.

The Adam is an all-electric airplane with two buses and two batteries. Excellent work has been done in this area, both by the FAA and the manufacturers, and those short-lived old vacuum pumps are just not going to be found on a lot of new-design airplanes.

For engine instrumentation, the A500 has a Vision Microsystems VM 100 engine management system. This was, to me, not a great step forward. The old Cracker Jack box mechanical instruments are easier to interpret, but then I’m used to them and not to the Vision system.

The airplane also has a Vision electronic checklist and caution advisory system that seems to cover everything.

Glenn Maben, one of the best demo pilots I have flown with, briefed me on the airspeeds to be used and offered one bit of advice about the sidestick. When the ailerons are neutral the stick is maybe 20 degrees to the right of being straight up and down. Apparently some pilots have wanted it straight up and down and have thus found the airplane rolling to the left at liftoff.

On Cessna Skymasters we used to always start the rear engine first. On the Adam they have been starting the front Continental TSIO-550E first. Full authority digital engine control (FADEC) will be available on the airplane but is not fitted on this particular airplane. That will eliminate the mixture control and automate the operation of the engines.

The starting is like any injected Continental, and even with the front engine running it is plain that the rear engine is coming on line just fine.

The visibility is great, and taxiing with the non-steerable nosewheel is no problem. Certainly if the production airplane had the steering of this one it wouldn’t be a problem.

I look at a lot of things on a new design to try to form an opinion of what that first takeoff will be like. The location of the A500 main landing gear suggested to me that the liftoff would be just right. If the landing gear is located a bit aft of where it really should be, the forces required to unstick are often high, meaning there will be a tendency to over-rotate, which often results in a little pilot-induced pitch oscillation after takeoff.

The Adam sits on the ground at a neutral angle of attack. This is also ideal for takeoff because the airplane neither gets light on the wheels in the roll nor requires a big tug for liftoff.

Finally, when the Adam is viewed from behind you can’t see much of the prop blades. This often means that the static thrust isn’t going to be too whippy.

The airplane had 120 gallons of fuel on board (total capacity is 270 gallons) and two standard people, so it was what you would call “light.” Remember, too, as I relay thoughts about the A500, that the airplane flown was of a design that has flown only a couple of hundred hours and that is in a state that is subject to change and constant refinement.

My advance thoughts about the takeoff were right and they were wrong. The wrong part relates to the static thrust. It felt very good as the 700 horses were allowed to gallop down the runway. The sense of acceleration felt much like that found in a conventional twin. Maybe good propeller work by Hartzell helps on that static thrust.

The transition from the roll to flight was neat, too. It’s a challenge to think about how to do it just right and a reward when the airplane agrees with the way it is done. Vr was 85 knots and the speed was up to about 95 when the rear wheels broke the surly bonds.

Because we were operating under the Atlanta Class B airspace (from Dekalb-Peachtree, PDK), the initial climbing was done at cruise climb. The indicated airspeed was 140 knots and the rate of climb probably averaged 800 to 1,000 feet per minute in the roiling air of an enthusiastic spring day.

I will give a report on my impressions of the sidestick when the flight is completed.

Once the last ring of the TCA had passed above, as shown on the two Garmin GNS 530s that will be standard, Glenn advanced the power to full and we went for the best rate of climb airspeed where the vertical speed vaulted up to 2,000 feet per minute. The airplane is going to be a strong climber.

After a little of that we were passing through 10,000 feet. Glenn reduced power on one engine to zero thrust, and by the time everything settled down we were at 12,000 feet and climbing at about 500 feet per minute. The airplane is going to remain a strong climber even with but one engine running.

The need for speed determines how much money we spend on airplanes, and the A500 does well in this regard. An upwind/downwind GPS run at 10,500 feet verified that production airplanes should cruise at least 200 knots at that altitude while burning 40 gallons per hour total. This airplane didn’t have main wheel well doors, which I understand will be fitted; it had a test boom, it had that temporary door that probably added some drag, and it lacked the final aerodynamic tweaking that is always good for a few knots.

Given the likely specific fuel consumption of the engines, 40 gallons per hour is about 75 percent power. So, lets say the conforming airplane will do 205 at 10,500 feet. Using the speed increase with altitude that is found in most other turbocharged twins, that would equate to a cruise of about 235 knots at FL 250, which will be the airplane’s maximum certified ceiling. If the temperature aloft is warm, though, the engines probably wouldn’t make 75 percent power at 250. In standard temperature, the engines are said to be able to maintain full 350 horsepower to 17,500 feet. The cabin will be at 8,000 feet at FL 250.

On descent I pulled the power back enough to stay comfortably below that 180 knots to which they have tested and to get a healthy rate of descent that brought the power to well below 20 inches.

At higher speeds the airplane rode well in the bumps. In fact, from what I saw, the airplane really does give a good ride in turbulence at any speed.

As we got close to PDK, the tower asked if we could land on Runway 27. Glenn said we could, though it appeared that we were a little close and high. I slowed to 140 knots, the speed they are using in test for the landing gear extension, and Glenn extended the gear and takeoff flaps. The airplane started coming down well and with just a little widening of the pattern we were able to turn final with the visual approach slope indicator saying “yes.”

Glenn said to use 105 as a Vref with full flaps and we did. As the end of the runway was approached, I reduced the power to idle, the airplane floated just a bit and then touched down. The trailing-link landing gear helps the pilot’s ego on landing.

Glenn then informed me that I had set a record by landing the A500 on the shortest runway, 3,378 feet, that it had ever used. With enthusiastic use of the brakes we could have turned off 2,250 feet down the runway. There was about a 10-knot headwind component on the runway and for a serious short field the Vref could be reduced to about 95 knots, which is still more than 1.3 Vso.

I thought the sidestick in the airplane is great. In roll, especially at higher speeds, the stick forces are on the high side but no higher than in my P210, for example. In pitch, everything seems just right. There are no big changes when the configuration of the airplane is altered and the coolie hat for the electric trim is at your thumb. Glenn asked what I thought of the speed at which the trim moves. It was a little fast for me, but the speed at which the trim runs will be determined during S-Tec autopilot certification, which should be under way as you read this.

The only thing I would look at on the sidestick is the relationship between the grip and the armrest. On this airplane my arm was not level on the rest when I gripped the stick. This meant that some of the roll commands were with arm as opposed to wrist motion. That did give more leverage but it also meant that roll commands were not as smooth as they should have been.

Because this airplane isn’t “finished,” I couldn’t make a guess on how the sound level will be, but I will say that the cabin was quieter than I thought it would be. My expectations were low, though, because sharing a composite tube with two engines can be like relaxing inside a drum. There was some low-order vibration that usually comes when the engine moves in the cowling under power and touches something.

The A500 was in Atlanta for, among other things, a showing to owners at AirShares Elite, a fractional provider that currently operates 14 Cirrus airplanes.

AirShares finds a great deal of A500 interest among its Cirrus shareholders and has ordered three of the airplanes. The deal is $170,000 for an eighth share, $1,600 a month for management and $160 for each hour flown. David Lee of AirShares reported six verbal commitments for A500 shares after the airplane was shown in Atlanta. He also reported that the insurance weenies were mentioning an instrument rating. One thousand hours total time with 100 multiengine, factory training and 25 hours in type are the requirements to fly the airplane solo.

The 100 hours multiengine requirement seems beside the point. There is simply no similarity between the technique required to handle a twin with wing-mounted engines after one fails and that required to handle a tandem twin after an engine failure. With the tandem you fly exactly as you would in a single with no power. Maintain the proper airspeed and follow the proper procedures and things work as well as possible. No fancy footwork required.

The Adam A500 isn’t a revolutionary airplane, but what it does is give the advantage of tandem power with no performance penalty and no flying qualities penalty, as was found in the Cessna Skymaster. Any pilot who is competent in a high-performance single will be perfectly suited to fly the A500 with the extra safety potential of a second engine. In fact, when you compare the A500 numbers with those of the Cessna 421, everything is close without the potential flying challenge of dealing with the asymmetric thrust if an engine fails.

Adam projects certification by this summer, but that looks ambitious to me. There are too many battles yet to be fought. And the elements that affect every new design-primarily weight and cost-have to be addressed every step of the way. Adam does appear up to the task, though, and I’m looking forward to a nice long trip in an A500 and to hearing them on the frequency and seeing them on the ramp. It’s a great and unique new shape in the sky.

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