On the Scene

What emergency medical service helicopter provides the best combination of flying qualities, cabin room, and economy of operation? Many hospitals vote for American Eurocopter's (formerly Messerschmitt Boelkow-Blohm) twin-engine BK 117. Currently, there are 320-plus BK 117s in service, with more than 400,000 hours flown. More than 30 percent of EMS helicopters in service today worldwide are BK 117s, and they are the most popular EMS helicopters in the United States. As a full-time BK 117 pilot for Columbus, Ohio's Grant Medical Center, I understand why.

Grant's LifeFlight program operates three BK 117s under contract from Omniflight Helicopters of Dallas. From three bases, it covers central, southern, and eastern Ohio and has racked up more than 10,000 consecutive accident-free missions.

Flying the BK 117 nearly every day, I quickly developed an appreciation for its responsive flight characteristics, a result of the unique hingeless rotor system developed by MBB in the 1960s. The system's control response is impressive. For example, where a typical two-blade teetering rotor system takes nine tenths of a second to respond to pilot inputs, the BK 117's hingeless system reacts in one tenth of a second.

The four glass-fiber-reinforced plastic main rotor blades attach directly to a rigid rotor head forged from a single piece of titanium. This arrangement makes the rotor system extremely strong, yet allows the blades a necessary welcome flexibility to flap and lead-lag. The rotor blades have no time life limit and with more than 3.8 million flight hours, the rotor head has never had a catastrophic failure.

I did all my initial training in the earlier BK (Model A1) with the smaller tail and a gross weight of only 6,280 pounds. Two major problems with the A1 are the low gross weight and a lack of tail rotor thrust. Many times, when landing on windy rooftop pads, I simply ran out of left pedal. MBB fixed the problems with the A3, which is the model that I typically fly. It has a larger tail rotor and an optional yaw stabilization augmentation system (YSAS) and a gross weight of 7,055 pounds.

All A-series BKs use the 650-shaft-horsepower Lycoming LTS-101- 650B1 turbine engine derated to 550. The engine problems that plagued the similarly powered Coast Guard Aerospatiale Dolphins and the Bell 222 — turbine wheel cracking, for example — have not shown up in the BK. This is due in part to lower power demands placed on the engines because the BK is so much lighter. Also, Lycoming has addressed many of the airworthiness directives, resulting in a more reliable engine.

Next came the B1 which uses the more powerful, 750-shp LTS-101- 750B1 engine, but still derated to 550 shp, and an improved tail rotor design for more thrust, and the YSAS became standard equipment. The additional horsepower margin allows the engines to run cooler. The current production model is the B2, with a beefier landing gear and shorter pitch change horns to improve main rotor response time and a gross weight of 7,385 pounds. Also available is a C1 model with Turbomeca Arriel 1E engines rated at 708 shp maximum takeoff power for better hot and high performance.

For redundancy in boosting flight controls, the BK is equipped with two completely independent hydraulic systems. If the main system malfunctions, the standby system automatically takes over. MBB eliminated switch-over problems that had occurred in the earlier versions by replacing the electrical switches with hydraulic ones. The hydraulic pumps are driven by the transmission so that pressure is maintained during autorotation. The current system has proved so reliable that it is certified as fail-safe.

Hydraulic boost is notorious for lacking control feedback — many pilots say it makes the controls feel like a wet noodle — but not in the BK. MBB has installed an artificial force feel on the cyclic control, complete with an electric trim, to mimic natural control forces. The system is designed to provide a firm feel and give the pilot a good reference for stick displacement.

Because we do a lot of on-scene landings that are not always on level terrain, the BK's hingeless rotor system can impart very high bending moments to the main rotor mast. Even on flat ground at idle, large bending moments can occur if the cyclic stick is moved or bumped away from the neutral point. The bending of the rotor shaft is shown on a mast- moment indicator gauge mounted on the panel. Exceeding the load limits will illuminate a red light that will stay lit and should be reset by a mechanic. Normally no damage is done, but the then-required inspection is a tedious job and a fast way not to get an invitation to that mechanic's Christmas party.

I constantly hear our flight crews praise the BK 117 for the rear clamshell doors. The doors permit two patients to be quickly loaded side by side into a roomy 176-cubic-foot cabin. The main precaution with this arrangement is the close proximity of the tail rotor during hot loadings. However, the safety record is very good because of the high tail rotor clearance and increased awareness from properly trained medical crews. Complementing the clamshell doors are standard, wide-entrance sliding doors on both sides.

The cockpit is roomy, and the seats adjust up and down as well as forward and aft. Add adjustable pedals to that combination, and the pilot can really customize the fit for maximum comfort. I especially like the fact that the cockpit is completely isolated from the cabin. This is a major advantage because EMS operations can be very distracting.

Empty, the BK 117-B2 typically weighs in at 3,820 pounds, yet has a maximum gross weight of 7,385 pounds. That's more than 3,500 pounds of useful load. With full fuel, the BK can still carry 2,300 pounds — even though it measures only 42.65 feet from tip to toe and has a rotor diameter of 36 feet. That's only 3.5 feet longer in length and less than 3 feet larger in rotor diameter than a Bell JetRanger. I have landed the BK on crowded rural roads and felt completely comfortable because of the compact size.

At Grant, four pilots are assigned to each helicopter. We work 12- hour shifts, and the program, which is single-pilot VFR, operates 24 hours a day. When we arrive to start a shift, we do a preflight, weather check, and some required paperwork. This assures that the helicopter can launch with minimum delay. However, during marginal weather, the decision to go is made at the time of the request. In these cases, no details about the patient are given; the weather decisions must be based purely on safety of flight. Because this is a time-sensitive operation, we normally have only a few minutes to possibly make a weather decision, plot an approximate course on a wall map, and have the helicopter ready to lift.

The hospital provides the pilots and medical crews with very comfortable quarters. Each base has shower facilities, a place to rest (this is actually required by the Federal Aviation Administration), and complete weather services. Our weather decisions are based on information from Kavouras, local ATIS, and color weather radar. Our weather minimums vary from a 1,000-foot ceiling and 5 miles visibility for night cross country to 500 feet and 2 miles for local daytime flights.

A recent mission exemplifies a typical trip — if any EMS flight can be called typical. We received a request to proceed to an auto accident about 20 miles from our base. Five minutes later, we lifted off into the night sky. Climbing to 1,000 feet agl, I rolled out on a general heading and then awaited latitude and longitude coordinates from our dispatch center.

At this point the BK was well below gross weight with a medic, flight nurse, and full fuel on board. When the coordinates came over the radio I entered them into a loran receiver, made course adjustments, and relayed our estimated time of arrival to dispatch.

Upon arriving at the scene several orbits were necessary to verify landing zone (LZ) information received earlier, and look for other hazards with the search light. Because landing areas tend to be highways or fields, on-the-spot decisions must be made regarding approach/departure paths, obstacle and terrain clearance, and safety of ground personnel. The challenge in EMS flying is doing this as quickly as possible without compromising safety, the Federal Aviation Regulations, or aircraft limitations.

After assessing the LZ, I set the helicopter up for a steep approach. When lining up on final it is important to keep in mind the BK's one-engine-inoperative (OEI) performance limitations, which are 40 knots and 300-fpm rate of descent. Keeping the helicopter within these limits for as long as possible during the approach allows the best chance to break off and fly away in the event of an engine failure. Because the BK has an excellent power to weight ratio, OEI performance is impressive.

The local EMS ground crews had set the LZ up in the middle of the road and marked it with red flares. As a result of the BK's full panel, keeping the LZ in sight during steep approaches is difficult. However, a little left pedal solves the problem by making the LZ visible through the lower right-hand corner of the windshield. (Now you know why a BK sometimes looks out of trim on landing).

Dropping down through 100 feet, I used the search light for another scan of the area for wires and positioned the BK into the LZ. Rolling the throttles back to idle is the signal that it is safe for the crew to leave the aircraft.

While on the ground, I recalculated the weight and balance based on the patient weight received from the crew. With two hours of fuel and a flight nurse, paramedic, and patient on board, the A3 is still 440 pounds under gross weight. The B2 model currently being produced would have 770 pounds to spare.

In about eight minutes the patient was on board and the crew had secured the helicopter for departure. Lifting off, the BK has plenty of power to go straight up. Once clearing the obstacles, I set a course for the hospital.

Our route of flight required a transition through Columbus's Class C airspace. Using the "lifeguard" call sign alerts the controllers that we are on a time-sensitive air medical mission that requires priority handling. The flight was smooth, and the BK settled into a typical cruise speed of 130 knots. The BK's roll, pitch, and yaw stabilization systems do an excellent job of damping out the small oscillations characteristic of the hingeless rotor system.

Grant's main helipad is in the middle of downtown Columbus and surrounded by tall buildings. The approach and landing is tricky and the wind almost always a good challenge. This is where I developed a special appreciation for the hingeless rotor system, because the quick control response allows for crisp control of the helicopter in changeable winds.

Flying EMS also means balancing aviation matters against the requirements of the medical crew, and sometimes that's very difficult to do. On another trip, we picked up a severely injured 16-year-old male who suffered head injuries after being involved in a motorcycle accident. Strong headwinds meant a 35-minute flight to the hospital. Just minutes from landing, he went into cardiac arrest. Our crew and the trauma team at Grant tried everything possible but were unable to save him.

Having to deal with situations like this adds a different factor to helicopter flying. I keep it in perspective by knowing that for the few who don't make it the helicopter was their only chance, and for the vast majority who survive the helicopter probably saved their lives.

While this work is exciting, challenging, and very rewarding, it is also very difficult. The medical crews want to help everyone who needs them, but it is the pilot's job to say no when weather or other situations warrant it. Holly Herron, one of Grant's most experienced flight nurses, says, "We trust our pilots implicitly, and when they turn a flight down, it is never questioned." Still, the occasionally hard but necessary decisions need to be made — like having unforecast weather force you to land enroute to the hospital with a critical patient so that a ground ambulance can complete the trip.

Air medical transport has come a long way since the days of the Korean War and the Bell 47. Civilian air medical service is still a young industry, and more changes are coming as manufacturers introduce new models and upgrade existing ones. Today, the BK 117 leads the pack, but soon some new and innovative designs will be out to give the BK 117 a challenge. MBB saw the need for a good EMS helicopter early on, and now American Eurocopter has no plans for complacency and soon will be introducing the upgraded BK 117-C1+, which includes an automatic rpm control and other system enhancements to the Arriel engines. The benefactors of all this are the hospitals, flight crews, pilots, and, most of all, our future patients.

Tim McAdams, AOPA 925518, is a CFI and has accumulated more than 4,300 hours, of which 4,000 are in helicopters. He is employed as a pilot by Omniflight Helicopters and is on contract to Grant Medical Center's LifeFlight program.