Flight Test:
Gulfstream 695A Commander 1000 – The Smart Choice
Text: Guy Leitch. Images: Ken Clark, Mitchell Hill and Guy Leitch
Twin turboprops have always been about performance compared to their piston progenitors. So it is remarkable that by far the best all-round performer is also the biggest secret – and that is the Gulfstream Commander 695A-1000.
The Gulfstream Commander is a product of the aeronautical brilliance of Ted Smith. His Commander 500 through 680 piston twins were among the top corporate transports available. Even President Eisenhower used a 680 Grand Commander as an occasional Air Force One, because of its good short-field capability.
DEVELOPMENT
The first Aero Commander twin, the Model 520, flew on 27 April 1948. Using flat-six piston engines instead of the then still popular radials, and a semi-monocoque construction, Smith’s Model 520 was the first true modern light twin.
The 520 has a strong resemblance to the Douglas A-26 Invader which Ted Smith had helped design. With its high wings and tall empennage, the Aero Commander 520 had lots of interior space and load carrying ability, comfortably seating 5, and able to squeeze in two more in optional rear-facing seats behind the front seats. Powered by a pair of 240-hp, geared piston engines, the 520 could cruise along at about 200 mph, when most airliners were still only flying at 180 mph.
Despite having the aura of a private airliner, the Model 520 was blessed with superb handling, great visibility, an easy-to-manage cockpit, and good short-field / rough-field capability, which was important in an age when most airfields were still rough unpaved landing strips.
To demonstrate its excellent engine-out handling, a propellor was removed from the critical engine of the first prototype – which was then taken-off and flown, non-stop, from Oklahoma to Washington, D.C. This feat would serve as a valuable lesson for a company that would eventually benefit from ‘stunt marketing’, thanks to a company vice-president named Bob Hoover.
A more streamlined version of the 500 became the Shrike Commander, which soon became famous in Bob Hoover’s hands. Hoover would get into his big, twin-engined Shrike Commander and fly loops and rolls – with both engines running, then on one engine, and finally the whole routine again with no engines, eventually gliding to land and coasting smoothly to stop on the same spot from which he’d departed.
Aero Commanders had been designed around the big-twin concept and could only get bigger – not smaller and more efficient. With an aisle between the seats, this class of plane came to be known as cabin-class. The Beech Model 18 had first claim to the class, and by 1960 Beech had debuted its Queen Air. The long fuselage Aero Commander 680FL was introduced the next year and Cessna and Piper soon followed with the Cessna 400 series and the Piper Navajo and Chieftain.
The planes had grown, but the power hadn’t, as the flat six piston engines could not make more than 375 hp. So Beech replaced the Queen Air’s pistons with Pratt & Whitney PT-6s and called it the King Air. As the King Air it quickly began winning sales from all top-of-the-line piston twins.
Aero Commander responded by putting Garrett AirResearch TPE-331 turboprops on its 680FLP. The result was the Aero Commander 681 (commonly known as the Turbo Commander, or – briefly, the Hawk Commander). It soon evolved into the slightly more powerful, and more refined 690.
Faster, by far, than the King Air B200, and any of the large Cessna or Piper piston twins, the beautiful 690 Commander was blessed with a cockpit that afforded great visibility for pilots and remarkably simple cockpit systems, while exuding the sophisticated image of an airliner’s flight deck.
With a roomy cabin and the advantage of a spectacular earthward view for passengers through huge picture windows (the King Air’s low wing prevented much of a view from its small porthole windows), the Commander retained a great appeal. The Commander’s high-wing and roomy, rectangular cabins (versus the cramped, round oval cabins of competing planes), great handling and hefty load capabilities made it hugely popular with all who flew them – or sat in the back.
The company was bought by Rockwell in 1958, who in 1981, sold it to Gulfstream Aerospace. Gulfstream introduced a series of improved models, culminating in the Twin Commander 1000, which was produced from 1982 to 1985.
The subject of our evaluation is ZS-KZZ, a 1983 Gulfstream Commander 695A-1000.
ZS-KZZ is the third of three Commander 1000s acquired new by Eskom and operated from Grand Central. It proved adept at the short legs to the nearby Eastern Transvaal power stations with small runways, and well as long flights to Cahora Bassa in Mozambique, and Cape Town, for the Koeberg power station then under construction.
For the historians, Eskom’s three Aero Commander 1000s were ZS-KZX, ZS-KZY and ZS-KZZ. ZS-KZX was exported to the USA in 1997 and KZY went to Australia in November 2014, leaving just KZZ in South Africa. Other 695 Commanders in South Africa are ZS-TWZ and ZS-MWT.
ON THE GROUND
The Commanders may not have the ramp presence of the King Airs with their high stance and even higher T-tail. Instead, they are low slung and sleek – and look fast. The high wing means that the cabin floor is low and easy to access. The fuselage is long and has a rectangular cross section, giving plenty of head room. Another popular Commander feature is the large external baggage compartment behind the cabin.
Ted Smith’s designs are easy to spot as they have the cockpit in front of the engines for better visibility out. The Commanders have the main cabin door at the front of the cabin, so the pilot can be the last one in and the one to close the door, without having to thread her way through passengers to the cockpit.
The 695A-1000 is powered by a pair of 820 shaft horsepower TPE331-10 engines, which deliver excellent fuel economy and have long overhaul intervals of 5,400 hours. These turboprops have direct drive props and so need a high idle speed and thus have a loud high-pitched scream on the ground.
The high wing gives the props a very useful 35 cm ground clearance, and the props are not as vulnerable to a pitching motion on the ground as are the forward mounted King Air props.
However, it wasn’t until Gulfstream bought Rockwell Commander in 1981 that the brand really hit its stride with two new models—the 900 and the 1000, also known as the 690D and 695A/B. About 40 of the 900s and approximately 110 of the 1000s were made. You can easily differentiate between the two: the 900s have large mid-cabin picture windows, which offer great views out, but make for a noisier cabin. The 1000s deliver 15 knots better maximum cruise speed—up to 305 knots—and have up to 500 pounds more takeoff weight than the 900s.
ZS-KZZ has just completed a major make-over which includes a new EFIS instrument panel, interior and paint job. Out came the electromechanical ADI and HSI and avionics panel. About 180 lbs of wiring was removed. The new panel features two Garmin G600TXI EFIS displays driven by two Garmin GTN 750 NAV/COM/GPS units in the avionics stack.
Bringing the aircraft fully up to date are two remote ADSB in/out transponders. There is a Garmin 75 weather radar and an S-Tec 2100 digital autopilot.
The cabin has been beautifully redone with a spacious double club interior for 6 adult passengers plus 2 pilots, or 5 adult passengers with 3 children and the 2 pilots.
With an endurance of over 6 hours, the rear cabin can be fitted with a belted electric flushing lav (making it a legal passenger seat) and a semi-rigid privacy door. The ‘squared oval’ cabin provides generous shoulder and headroom for a plane in this class. The baggage section can hold 600 pounds.
All Commanders can be flown single pilot. With pilot, three passengers, full bags, and full fuel, Commander 1000s can fly a very impressive 2,000 nautical miles—that’s eight hours of cruising.
FLYING THE COMMANDER 1000
ZS-KZZ’s Honeywell TPE-331 -10 engines have a ‘mini FADEC’, being a Single Red Line (SRL) computer which prevents novice pilots from doing a hot start by feeding in too much fuel too quickly.
Taxying can take some getting used-to. With the brake pedals operating proportioning valves, Commander brakes are different to most other aircraft. It’s common to see new Commander pilots making jerky side-to side motions with frequent application of brake as they try to figure out the pedal steering.
Unlike the Pratt & Whitney PT-6A turboprop, which has propellers that turn independently of the rotating components of the powerplant (the so-called free turbine design), Garrett TPEs use a single-shaft. This means that the shaft to the propeller gearbox is directly connected to the rotating engine’s compressor.
In a power loss, the windmilling prop still drives the engine and so generates huge drag, not to mention asymmetric thrust. So Garrett engineered a system that senses negative torque, then automatically sends the propeller of the sick engine to a nearly feathered condition (the pilot must manually complete the feathering) when it detects that the prop is driving the engine. Without this NTS (negative torque system) a Vmc rollover may be a risk after an in-flight engine failure. A pre-flight check of the NTS is thus required before every flight. If the NTS doesn’t pass the preflight checks, it’s a no-go item.
With the Commander 1000’s good power to weight ratio, acceleration is brisk, especially at typical lighter weights. Rotation is weight dependant but is around 85 KIAS, which can be reached in 300-400 metres, depending on weight and density altitude.
Climb at 130 KIAS can be greater than 4,000 fpm, and 160 KIAS is a typical cruise-climb still going up at over 3,000 fpm initial climb. It can climb straight to FL280 with a full load. At that level it will do over 300 KTAS, depending on load, typically burning 450 lbs/h, which is about 70 gph.
The 6.7 psi pressurisation differential keeps the cabin at 7,000 feet at FL280. The two engines combined use about 85 gallons the first hour, and about 75 gallons every hour after that. Fuel burn and speed decreases above FL290, so in its upgrade, ZS-KZZ was not approved for RVSM operations.
If flying for range, the Commander 1000’s 3,200-pound fuel capacity provides an easy six-hour endurance for as much as a 2,000 nm still air range. The aircraft has an amazingly simple fuel system, having what is in effect just one big tank, although there are in fact 22. So there are no issues with cross-feed or fuel mismanagement. Everything is interconnected, so all fuel comes from just one source.
ZS-KZZ is usually flown for its owner by Mitchell Hill, who notes that the perception of speed is much the same at 80 knots as it is at 180 knots. Consequently, the first few landings with a new Commander pilot usually are either too fast or too slow. Most new pilots seem to want to err on what they consider the safe side, and end up doing the approach and the landing much too fast.
Mitch Hill reports that it climbs at around 750 fpm on one engine at gross weight, and with the large rudder, asymmetric thrust is easy to control. “You can even trim the plane out and put your feet on the floor. Most pilots say an engine failure is a non-event.”
Another key safety feature is that the clean stall and Vmc within two knots of each other. With a clean configuration the buffet comes at 75 KIAS and with flaps, at 72 KIAS, with no tendency for either wing to drop.
Every turbine Commander comes with a maximum turbulence-penetration speed. These speeds relate directly to the structural strength of the airframe, with the empennage usually being the weakest link. Most Commander models therefore have a big 180-kt IAS Va (manoeuvring speed) placard on the windscreen post, applicable to flying in light-to-moderate turbulence. In severe turbulence, depending on operating weight, Va can be 40 -50 kt less than the 180-kt limit. The lighter the aircraft, the slower Va is.
All the turbine Commanders have an excellent short and rough field capability. Approach is typically 110 KIAS slowing to 95 knots over the fence. With the big wheels and if necessary, beta or even reverse on the props, you can get stopped in 300 metres.
King Air B200 fly-off
Mitch Hill reports that they performed a real-life comparison with a Beech 200 King Air – its direct competitor.
Flying ZS-KZZ, Mitch took off from Queenstown for the 485 nm sector to Cape Town, ten minutes after the King Air. Despite being kept low by ATC until he had overtaken the King Air, ZS-KZZ landed 20 minutes before the King Air – and burned 200 litres less fuel. And the Commander has significantly lower maintenance costs, due to longer engine times between overhaul.
For an owner operated twin turboprop, the Commander 1000 is indeed the smart choice.
CONCLUSION
Ted Smith’s aerodynamic genius is evident in many aspects of the Commander. He got it right first time so you don’t see aerodynamic afterthoughts like stall strips, wing fences or vortex generators.
Gulfstream’s ownership of Commander lasted only from 1981 to 1985, but Commanders produced during this period are highly valued.
Once you have flown a turbine Commander, pilots understand why the passion for these planes runs deep. Commanders might have been out of production for nearly forty years, but with hundreds still flying regularly, and with strong support from type certificate holder Twin Commander, these planes should continue to fly for decades to come.
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PARTS AND SUPPORT.
For aircraft types no longer in production there is always potential concern for long-term parts supply.
Today, Twin Commander Aircraft of Creedmoor, North Carolina, holds the type certificate and supports the type with parts it makes from more than 58,000 pieces of original production tooling. Matt Isley, the CEO, notes that “95 percent of our parts requests are out the door the same day. We stock a lot of inventory. When you compare the support we provide with the support of an in-production aircraft, we’re on par with some of the best OEMs to make sure our owners have mission-capable aircraft. Guys are comfortable flying this airplane in revenue-producing roles because the product support is there.”
Twin Commander’s Grand Renaissance program is a virtual rebuild of the aircraft that effectively zero-times the airframe. But even without such investment, Commanders tend to be robust. Still, “when you’re dealing with an aircraft that has been flying for 30-plus years, you’re going to have some corrosion things and structural issues,” Isley notes.
“Gulfstream really learned from the earlier models and eliminated a lot of problems with the changes they made on the 900 and 1000,” Isley continues. “There have been only two large service bulletins on the [Commander] line in the last six years, but those have not applied to the 900 and 1000 models, so they are fairly clean from an SB [service bulletin] or AD [airworthiness directive] standpoint.”
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