Military, Products

Flying The MD540F

By By Ernie Stephens, Editor-at-Large | January 1, 2013

Though still in development, the MD-540F is showing the potential to be
a superior warrior.

They say that the best situation an aircraft manufacturer can be in is to have a product that both the military and the civilian worlds want. Very few have been able to continuously satisfy both sectors with a single hull design. But MD Helicopters (MDHI) based in Mesa, Ariz. is one of them.

In 1963, Hughes Helicopter Co., the birth name of MDHI, introduced the OH-6 “Cayuse;” a light, single-engine, turbine helicopter that looked like a flying egg. But say what they wanted about the little reconnaissance aircraft, its speed and agility made it perfect for snaking around the jungles of Vietnam, and its egg-shaped hull provided the most crash-worthy cabin in the Army’s inventory.


In 1984, the OH-6 was redesigned into the AH-6 “Little Bird” attack/reconnaissance helicopter. Its agility, coupled with an assortment of wing-mounted weapons, has made it the helicopter of choice for the Army’s elite 160th Special Operations Airborne Unit. And although MDHI’s previous owner, RDM Holdings, sold the design rights for the AH-6 to Boeing in 2003, current owner Patriarch Partners bought at least some of those rights back, and now builds a portion of the tough little helicopter—designated the AH-6M—and the AH-6i light attack helicopter as a Boeing subcontractor.

Meanwhile, MDHI’s MD500 line—a civilian version of the OH-6—has enjoyed great success as a police and power line patrol platform in its D, E and F models. A 500M variant called the “Defender” has seen service with the armed forces of several small countries, but with fewer accolades.

The last ship in the 500 line to be certified was the MD530F, with its increased main rotor and transmission ratings. Those features, plus other changes and upgrades, gave the F model substantially increased high-hot-heavy capabilities, and a service ceiling that was 4,800 feet higher than the E model when it was certified in the mid-1980s. 

The six-bladed rotor system gives improved handling over previous models in the 500 line. Hard banking is smooth with minimal blade slap.

Now comes the MD540F, the company’s state-of-the-art, armed helicopter. If the Boeing AH-64 Apache is the “big gun” of Army aviation, the 540F is a point scout packing a big sidearm and a very sharp knife. MDHI hopes it will be certified “soon,” but no one would commit to a date.

Even with its weapons systems still in the integration stage, MDHI wanted Rotor & Wing to be the first publication to take the 540F for a test drive. So, out to their plant near Phoenix I went to see what it would do. Chris Nehls, vice president of engineering, explained that the MD530F was built for the battlefield. “It’s everything you’d want in [an armed] scout aircraft,” he said. “We wanted to make it an affordable solution for both the U.S. military and foreign militaries.”

The 540F is currently powered by the same Rolls-Royce 250-C30 gas turbine engine that’s in the 530F. But the company will later install an even stronger Rolls-Royce powerplant. That engine will drive an all-composite, six-bladed rotor system specially designed for MDHI by Van Horn Aviation of Tempe, Ariz., giving the ship greatly increased lifting capability. But for now, the main rotor shaft flies with the same six-bladed setup found on the larger MD600, instead of the shorter, five-bladed set on the 500 line.

After a short technical briefing, I met up with company pilot Nick Page, whom I would be flying with. As with all of the evaluation flights I do, I got a good briefing, reviewed some emergency procedures, then headed out into the bright, Arizona sun. 

The MD540F can carry a variety of missiles and guns on each end of its weapons ring. The structure doubles as a 62.1-gallon auxiliary fuel tank.

On approach to the flight line, I immediately noticed that the skids on the 540F were beefier. This is because the engineers are looking for a 3,800 to 4,100-lb. takeoff capacity for production models. That kind of weight, they determined, needed more robust skids than the standard 500-model tubes. So, instead of designing a brand new set, the 540F will come with the skids used on the heavier MD600 helicopter.

The back doors of the fuselage were gone from the aircraft to allow for the weapons wing, which can hold a combination of externally mounted guns, missiles and guided rockets. The wing also serves as a 62.1-gallon fuel cell, nearly doubling the approximately 2.8 hours of flying time provided by the main 64-gal fuel tank.

The targeting gear had been removed by its manufacturer, L-3, but I was told that it features the same general kind of in-helmet target acquisition system found in the Apache. The system aboard the 540F is also capable of showing each pilot exactly where the other pilot is looking, thus making crew coordination much easier. Nick Page and the ground crew had already done a thorough inspection of N540HH, so after a quick walk-around it was time to board. Pilots who drive civilian versions of the MD500 know that the pilot-in-command sits in the left seat.

But since military specification almost always call for the PIC to sit on the right, the aircraft’s primary flight instruments favor the person on the starboard side. MDHI’s policy—at least in aircraft still designated as “experimental”—is to put their pilot on the PIC side. So, I strapped myself into the left seat. 

The same 650-shp Rolls-Royce 250-C30 powering the older MD530F is installed in the experimental MD540F. By the time it goes into production, it will have a more powerful RR engine.

Once aboard, the 540F felt like the other members of its model line that I’ve flown. With a fixed seat, the only thing you can do to find a comfortable position is to move the pedals a few inches fore or aft. And for my 5’10” frame, that meant setting them as far away as possible. As for proximity to the cyclic, what you have is what you have.

The size and shape of the instrument panel is typical for a latter-day, civilian 500. The instrument panel is T-shaped, but narrow enough to easily see around for steep approaches.

The engineers installed three multi-function displays. From left to right, the largest screen is an Elbit Systems moving map with navigation and battlefield situational awareness capabilities. The top-right module is a split-screen Garmin G500H displaying primary flight information. On the lower portion of the console is a backup glass instrument display, along with a standard Garmin GNS 430 GPS/radio transceiver.

The lower console houses a targeting control system, communications head, and a weapons control panel for managing the things that make stuff on the ground blow up. All instruments, switches and controls were easy to consult and reach. Even the bright sunshine didn’t cause any problems with the displays.

Cranking the 540F was straightforward. Page executed a modulated start, holding the igniter switch for just a couple of seconds before the compressor reached its 12 percent light-off minimum.

After completing the pre-takeoff checklist, Page hopped the ship over the fence of the company ramp, set us down on Taxiway Echo at Falcon Field (FFZ), and waited for the tower to clear us for departure to the training area six miles northeast. When it was received, he turned the controls over to me.

Having logged many hours in MDHI products, I was already used to the heaviness of the unboosted cyclic, which tends to disturb most other pilots who are accustomed to hydraulically assisted sticks. In fact, only 3 oz. of hydraulic fluid is aboard the aircraft. It resides in a small mechanism mounted under the flight deck that dampens rotor-induced cyclic kickback. But bumping the trim control on any 500-model’s cyclic will alleviate that stiffness, making the aircraft very easy to fly. (For those used to flying a 500, the 540F’s trim motor is noticeably faster!)

Climb-out was spritely in the calm wind. And with a takeoff weight of approximately 3,100 lbs., it was easy to tell that the engine and rotor combination upgrade produced a substantially more powerful ship than previous 500s.

The 540F’s field of view is excellent, except for the issue that plagues all of MDHI’s 500 models. The doorframe closest to you, being about 4 inches wide, can be right at eye level for pilots around my height. One remedy is to slouch or bend down when turning to look in that direction. Flying with the doors off is the second cure.

Once out over the practice range, I put the 540F through its paces. The MD500 line has always been a well-mannered aircraft that won’t do anything until you give it permission, and this one was no different. The collective didn’t wander. The pedals moved easily, and there was that great feedback in the cyclic that let me know that it was working for me, not vice versa.

MDHI’s engineers made the right call with the new rotor system. Whether I eased the aircraft into a bank or threw it on its side, the blades executed the maneuvers smoothly and with less blade slap than its five-bladed predecessors. Even while heeled over in a 70-degree bank, “dirty” from its weapons wing, the 540F seemed happy to comply, and could have taken much more, I suspect.

Hauling the 540F from a 90-knot cruise into an out-of-ground-effect hover was so uneventful, it could have put me to sleep. As it passed through ETL I could really feel the power of the two-bladed tail rotor as it bit into the air. The unnerving shake that is common in the MD520N’s NOTAR (no tail rotor) design was also missing, and there was an abundance of power remaining as the airspeed indicator reached zero. Getting back underway was equally smooth.

In an effort to see how much speed we could get out of the 540F, I returned the controls of the aircraft over to Page, and asked him to drive us up to the first limiting factor, which on this day was going to be torque. With him holding the aircraft at the top of the green, it delivered 128 KIAS (133 TAS) straight and level at 1,960 feet MSL on a 23° C day with an altimeter setting of 29.93. Not bad at all.

Normally, I would check to see how well an aircraft autorotates. But because the 540F is still under development, certain flight maneuvers have yet to be approved, at least for demonstration purposes to an outsider. So, the flight concluded with a variety of approaches and takeoffs back at Falcon Field, along with some playtime in ground effect. No problems, no surprises, and no complaints.

Since my opinion of the MD540F is limited to how it flies, as opposed to how it fights, I can only say that current and former OH-6, MD500 and AH-6 pilots will be quite impressed with what MDHI’s engineers did with this design. They took a more-than-capable light attack scout and, to quote MDHI’s president and CEO Lynn Tilton, “...gave it attitude.”

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