Almost 50 years after it was designed, the Aerostar remains both an enigma and the hottest GA piston twin in the world. Its reputation for performance comes hand in hand with a less desirable one, myth or otherwise, of rather tricky handling. I was lucky enough to flight test the ultimate manifestation of the design—the Aerostar Super 700—that won the 2001 London to Sydney Air Race.
The Aerostar was the culmination of a legacy of design firsts from one of the 20th century’s great aeronautical engineers. His name was Ted Smith, an American pivotal in the design of many record-breaking aircraft, including the Douglas A-20 Havoc bomber—better known to Brits as the Boston.
Ted Smith also designed the Aero Commander, an aircraft made famous by display pilot Bob Hoover that is often mistaken for the Aerostar. Smith set about designing the Aerostar in 1964.
The Spirit of Kai Tak
Owner James D’Arcy bought his Aerostar with one goal in mind: to compete in the London to Sydney air race. Spirit of Kai Tak didn’t just compete but won, with an average speed at altitude of more than 270 knots.
After buying their 1982 Piper Aerostar 601P from the Aerostar Aircraft Corp. (AAC) based in Coeur d’ Alene, Idaho, D’Arcy and his partners, Mark Graham and John D’Arcy (James’ father), then had AAC upgrade it to Super 700 status prior to ferrying it to the UK.
The main difference is the replacement of the 295 hp engines with 350 hp units. In fact the aircraft was completely stripped out, rebuilt, retrimmed and repainted in the process—one of only two ever to undergo such an extensive rebuild by Aerostar. The result is a wonderful machine which looks like new, certainly not a 32-year-old example of a 50-year-old design.
My first impression was how small it is. I had heard so much about the Aerostar I think its size must have grown in my imagination. I anticipated that the Aerostar must be as big as a Piper Navajo; in fact it is smaller than an Aztec.
The Aerostar’s features
In the flesh, the Aerostar inspires just one word, and that word is “speed.” From nose to tail, wingtip to wingtip, the Aerostar is an amalgam of aerodynamic refinement and cleanliness. Starting at the back end, you might notice that the tailplane (horizontal stabilizer) and tail fin look the same. This is because they are; to reduce the parts count for the machine, the Aerostar is said to have a type-specific parts count less than 50 percent of comparable aircraft.
In practice, both the rudder and elevator were found wanting at low speed and later Aerostars have small, stick-on vortex generators to improve boundary layer control at high angles of attack and/or low speed.
The ultra-thin wings are joined to the fuselage just below midsection with the main spar running underneath the cabin floor. The engines are mounted high up on the wing to improve prop clearance. The wing planform is unusual in itself, with the trailing-edge sweeping forward to the tips as opposed to the almost straight leading-edge. The result of all this is a particularly eye-catching design, but the same goes for the smaller details such as the thrust-producing engine exhaust chambers. Even the aluminium door handle is shaped like an airfoil (and costs $700 (U.S.) to replace if it gets stolen).
The Aerostar is a beautiful, beautiful aircraft, even more breathtaking when you realize that the design is 50 years old.
Mindful as I was of its reputation, the Aerostar managed to bite me before I had even climbed in. After a particularly close check of the landing gear, as I climbed out from under the wing I managed to brain myself on one of the knife-like propellers.
There followed 20 minutes of frantic first aid intermingled with assurances from me to all present that no, I hadn’t concussed myself, and yes, I would try not to bleed on the new upholstery. As one of my funny friends said afterward, I didn’t see stars, just an Aerostar.
The gear doors are slightly unusual in that after the gear is extended the doors shut, airliner fashion, to reduce drag. The nosewheel twists through a few degrees as it rises into the nosegear well. In practice, this complicated arrangement can result in retraction and extension problems if the undercarriage is lowered in anything other than wings-level flight, since the gear doors can twist. So for longevity of the system, owner James D’Arcy insisted that I keep the aircraft in level flight before extending and retracting the wheels.
Access to the cockpit and cabin is via a single clamshell door on the captain’s side. The bottom of the door drops down to provide a single step; the seat slides forward to access the cabin. The aircraft is a true six-seater but D’Arcy and his partners have opted for three cabin seats plus a table in the club style. An emergency hatch is fitted rear right—especially useful after a ditching, as using it would put the aircraft occupants on top of the wing.
The fuselage design is about as close to a true monocoque as it is possible to get in an aircraft. The fuselage skin is approximately twice the thickness of comparable light twins to reduce internal bracing around inevitable orifices such as doors and windows, and especially in the belly area. This means that the fuselage interior space starts life uncluttered.
The instrument panel itself is a blend of old and new. Some of the instruments and controls look a little dated, whereas the aircraft is also equipped with more modern navigation systems including a Garmin 430 GPS and autopilot.
The fuel system looks quite complicated, and it is, because the aircraft has an additional auxiliary tank in the rear fuselage which transfers fuel into the main tank at the rate of one gallon per minute. For reasons of space, the auxiliary system is on a different part of the main panel (top right) to the main fuel selection and indicating system (center panel).
As with most twins, the fuel can also be cross-fed from the wing tank on one side to the engine on the other. The switching for this is straightforward.
This Super 700 can carry a total of 210 U.S. gallons, 165 in the main tanks and 45 more in the auxiliary. This gives a range of around 1,000 nm plus IFR reserves.
The Super 700’s engines are turbocharged and have wastegates fitted so that the engine cannot be overboosted at low altitudes and/or in cold, dense air. In practice, this means that the throttles can be firewalled for takeoff; when the maximum manifold pressure is reached, the wastegates will bleed off the excess air charge and maintain maximum power without overstressing the engine.
As the aircraft climbs, the wastegates progressively close until they are shut fully. Further climb will result in a manifold pressure less than maximum and so less power.
The quirkiest feature on the panel is the nosewheel control. This is a toggle switch at the base of the center console which is used to steer the aircraft during all but the gentlest of turns on the ground. The rudder pedals simply deflect the rudder and extra turning from this source is by using differential braking.
Cabin pressurization controls further complicate the cockpit and before closing the doors it is important to make sure that the pneumatic door seals have not been fouled by the locking bolts, which protrude from each side of the top clamshell door.
Startup procedures and systems, taxiing
Once seated in the comfortable flight deck, I noticed that the wings and engines are a long way behind the pilot’s position—this really does feel like a baby propliner.
Engine starting is a complicated affair and involves priming with the electric booster pumps while cycling the mixture levers from idle to rich with throttles full open, thereafter closing the throttles and bringing the mixture to cutoff before cycling the engine on the starter and bringing the mixture steadily up to rich once she fires.
With both engines running, cabin noise was about average for a piston twin and, while we waited for them to warm up, D’Arcy brought a few systems online, including pressurization. We set an arbitrary 1,000 feet cabin altitude, as we wouldn’t be going above 5,000 feet.
The Aerostar is able to maintain a cabin pressure well below 10,000 feet when the aircraft is at 25,000 feet. A 7,800- to 8,200-foot cabin is typical. As a comparison, in a Beech Baron 58 the cabin would be at 12,000 feet when the aircraft reaches FL 250.
With the engines up to operating temperature, I released the brakes and rolled forward a few feet before reapplying them to check function. Then I operated the nosewheel toggle switch. Turning is progressive and not at all jerky, but there was a lag between asking for and getting the nosewheel deflection that I wanted.
I found that I had to anticipate the turns a little way ahead, especially when we were taxiing fast. For shallow turns it was much easier to use the rudders with differential braking. I could see how easily a pilot could end up cross-controlled on the rudder; i.e., with left pedal and brake deflection fighting a right toggle switch selection.
For the same reason, it is important to roll straight ahead for a few feet on the runway without brakes or any rudder pedal deflection so that you know the tiller is neutral.
Bog standard engine runups and vital actions were accomplished with an accompanying bass tone betraying the huge power of these engines. I made sure that the fuel crossfeeds were shut so that we were feeding tank-to-engine on each side, and also checked the auxiliary system. (Green lights show that the system is functioning—i.e., transferring—normally; amber lights if not.)
The main runway is long at Bournemouth (EGHH) and so D’Arcy elected for me to fly a flapless takeoff.
Three thousand feet of runway is the magic number when operating an Aerostar—forget shorter runways and grass airfields. A flapless takeoff would mean even more runway eaten before we were airborne but it would also result in a faster transition between takeoff speed and single-engine safety speed.
With the aircraft running straight, I released the steering toggle and concentrated on pointing her down the runway with rudder pedal alone. I opened the throttles together and checked that the engines were running up at the same rate (if not, I would have directional control problems) before bringing them up past 50 percent power as we leapt forward. We were already accelerating at an impressive pace as I carried on pushing to the forward stops of the throttles.
Slippery and strong in flight
The Aerostar felt hugely powerful but controllable and we surged along the runway. Despite the acceleration it still seemed to take a while to get to the 90-knot rotation speed, a little like the takeoff roll on a long-haul flight in a large jet.
As the ASI needle flickered past 90 knots, I raised the nose and the Aerostar leapt into the air at 95 knots. The elevator seemed sensitive but the effect deadened for an instant as the tailplane lowered into ground effect above the runway.
Now I was pushing the stick forward slightly so that we could accelerate as quickly as possible toward 117 knots and a guarantee of a safe departure if an engine failed—below this speed, my response to engine failure on one side would be to close both throttles. A little dab on the brakes to stop the wheels rolling and I asked D’Arcy to raise the gear.
A single red confirmed that the gear had cycled correctly and now we proceeded to gallop past 140 knots before I translated the Aerostar into a climb with a healthy 1,500 fpm showing on the VSI. The performance was more like that of a turboprop than a piston twin.
One of our most important tasks before coming to Bournemouth had been finding an aircraft to act as a camera ship fast enough to photograph it. We finally settled on 150 knots for the air-to-air work with photographer Keith Wilson hanging out of the back of a Chinese military trainer, the Nanchang CJ-6.
As we approached the Nanchang, I was getting used to the Aerostar’s sensitive elevator and slippery behavior. The ailerons were light and powerful, the rudder firm to the touch but powerful and responsive nevertheless. I wondered if Ted Smith had anticipated such a power upgrade to his original design (yes he did, I later learned) the prototype of which flew on less than half the power of the Super 700.
This ultimate Aerostar copes with its bigger engines admirably, the airframe strong and taut enough to cope with such a massive increase in thrust, weight and accompanying aerodynamic loads. In light turbulence over the coast the Aerostar felt very stable, although I noticed that the rear end was fishtailing occasionally—not so comfortable for rear-seat passengers but fine up front.
As I brought the throttles back to maintain station with the camera ship, I noticed that there was no surge in the pressurization. It is obviously a good system. The Aerostar is predictably slow to respond to throttle inputs and it took a little longer than normal before I felt comfortable enough to get in close to the CJ-6.
I later wound the Aerostar up to maximum power and pointed it along the coast west of the Isle of Wight’s Needles. The ASI stopped climbing at 230 knots IAS, truing out to 240 knots at our altitude and temperature. But it is above 10,000 feet where the Aerostar really starts to earn its keep.
Turboprop numbers are easily achievable—the Aerostar is actually faster than some turboprops, including the early King Airs. Aerostar pilot Alex Wells explained that he flight plans the Aerostar at 240 knots (that includes climb and descent) however, 270-plus knots is easily achievable. At this speed the aircraft will consume more than 50 U.S. gallons per hour but economy speeds at altitude can get the burn below 40.
Control feel was firm but not too stiff even at these high speeds, the elevator still lighter than ideal but easy to get used to. I thought the Aerostar might actually be unstable in pitch, but it wasn’t—a 10-knot departure from trimmed speed had the aircraft returning to the trimmed speed in just one phugoid. Roll stability is neutral at high and low speed.
At the low speed end, the Aerostar is stable and controllable all the way down through the stall. As we neared the clean stall speed of 87 knots, I was deliberately rough on the controls but the aircraft just wallowed through the sky.
There is a warning horn which sounds off when the throttles are closed with the gear up and this proved to be a bit of a pain during the flight (it can’t be canceled) and I now found myself ignoring it, which is even worse if you think about it.
The stall itself was benign and the Aerostar didn’t wing-drop… that put another myth to bed as I’d heard that the wing-drop can be vicious. Next time, I tried it with a handful of power to exacerbate the characteristic, but the outcome was the same: a mushy, indistinct stall not at all representative of a laminar-flow wing and definitely not difficult to deal with. Conversely, the loss of height was prodigious and I routinely needed 500 feet to recover fully.
D’Arcy and I had agreed that it wasn’t appropriate to actually shut down one of the engines during the flight because they are very new. However, we did bring one back to zero thrust and I recorded a climb rate of better than 500 fpm at our moderate weight of 5,500 pounds, which is 800 pounds below MTOW. At MTOW and sea level, the book figure is 387 fpm.
The aircraft felt very controllable on one engine, and not the beast that I had been anticipating. I brought the speed all the way back to 117 knots with full power on the live engine and had no difficulty maintaining control. In fact I wouldn’t mind guessing that the aerodynamic mods, especially to the tail, have reduced the Vmca of the Aerostar Super 700 despite the power upgrade. The trick in all multi-engined aircraft is to trim early and keep trimmed—a change of power or speed heralds a trim change, likewise for a change of configuration.
Landing
I turned for base with D’Arcy calling out the relevant information. The Aerostar is a “numbers airplane” just like the bigger, higher performance aircraft to which it aspires. The intermediate approach is flown with just one power setting: 20 inches manifold. And when leveled, the aircraft’s speed will bleed back slowly through flap and gear speeds without shock cooling the engine.
The first stage of flap can be lowered at 170 knots, which we did, followed by the gear at 154 knots. The rest of the approach we flew at 120 knots. Only when we were committed to landing was the speed reduced below the blue line speed of 117 knots. Then 100 knots over the hedge seemed to work well and she settled in a flat attitude, and in ground effect at 90 knots with the throttles closed after the flare.
Accuracy is the key to operating the Aerostar: five knots slow on the roundout and you will fall onto the runway; five knots fast and you will float for an age while watching the far threshold rushing toward you. In this respect, the Aerostar would make a great airline trainer—all large transport aircraft are numbers airplanes, even fly-by-wire Airbuses.
Not a relic
You might think that the Aerostar is a gas-guzzling relic of the 20th century and irrelevant in any practical sense to the 21st. You’d be wrong as the Aerostar remains the highest performing piston twin and is actually quicker than some turboprops including the Piper Cheyenne and the ubiquitous King Air (I’m talking about the King Air 200, not the old and slow 90).
So, for a lot less than the cost of a turboprop you can have the same performance—and the seat passenger mile costs are comparable, even with Avgas costing £2 per litre against £1 per litre for avtur. (Editor’s note: Adjusted at current exchange rates, in dollars per gallon, Avgas would be a little over $13, while Jet-A would be about $6.60 per gallon.) Aerostars are certainly not cheap to run but they don’t have to be crazily expensive.
Insurance rates are favorable because the insurance companies anticipate and insist that operators of these machines will always get the necessary training and currency required to operate such high performance aircraft. Maintenance bills are similar to other piston twins. The test aircraft just had its annual, which came in under £6,000 ($9,873).
And if you think that the 47-year-old Aerostar’s story is history, you’d be wrong again, because a jet-powered Aerostar FJ100 has flown over 200 hours in development testing and was on display at EAA AirVenture in Oshkosh in 2011. (According to Jim Christy, vice president at Aerostar Aircraft Corp, the company is currently working toward certification. For more on the FJ100, take a look at “Ted Smith’s Dream: Record-setting piston twin sprouts jet engines” by Dave Hirschman. The story, published Jan. 24, 2014, is available on aopa.org. —Ed.) Since Ted Smith had the foresight to wind tunnel test the original design to 800 mph, an increase in performance won’t be a problem if this 500 mph aircraft is able to make it into production. What a clever fellow he was.
