AOPA Hover Power

In response to my previous blog, Jon S. brought up some very good points. He questioned whether an EMS pilot would climb into the clouds, autopilot or not, if he or she would face an FAA violation for doing so. He is absolutely right as declaring an emergency does not guarantee a pilot won’t be cited with a violation. The FAA has taken the position that if the emergency is caused by the pilot’s action or inaction, then a violation is appropriate. In many cases the NTSB has upheld the FAA’s decision.

So how does this affect an EMS pilot’s decision making process? Well, in all the EMS Part 135 operations manuals I’ve read there is a defined procedure for inadvertent IMC. Basically, it is to climb, contact the nearest ATC, declare an emergency, and perform an instrument approach. In discussing this with other operators, I was told that the local FSDO has taken the position that if a pilot does the appropriate due diligence that they will not pursue a violation.

According to the NTSB, on June 8, 2008, an EMS pilot in Texas aborted a flight because of low clouds and fog encountered en route. The request was then made to a different operator. The second pilot was notified of the flight and performed a weather check for the route of flight. After his weather check, he contacted his company’s Enhanced Operational Control Center (EOCC) to discuss his weather observations and the previous turn down. Both the pilot and EOCC supervisor were observing 10 miles visibility and ceilings acceptable for the flight. At that time, the pilot or the supervisor did not understand the reason the other pilot turned down the flight. The pilot contacted EOCC a second time to discuss that the previous flight had been turned down because of fog. The pilot and the EOCC supervisor again discussed weather observations with the same conclusion, that the restriction to visibility reported by the previous flight was not observed by any official weather reporting station.

The Bell 407 crashed in densely forested terrain killing the pilot, flight nurse, and paramedic. Sheared treetops indicated initial impact occurred with the helicopter’s main rotor blade system in a straight nose-low attitude. It happened in the exact location where the other EMS pilot had encountered low clouds and lost reference to surface lights. The other pilot told the NTSB there were no traffic or weather concerns at the time of his departure. While en route, approximately five miles south of the hospital, at 1,400 feet he encountered wispy clouds. He descended to 1,200 feet and encountered more clouds, continued to descend to 1,000 feet and encountered even more clouds, and finally descended to 800 feet when the visibility decreased rapidly. He stated that he could see to the east but had lost his surface light reference. He turned immediately to the right, towards the freeway system, and was back in good weather. He stated that the low clouds and visibility were very sudden and dramatic.

Whether a potential FAA violation affected the accident pilot’s decisions that night will never be known. This kind of accident happens too often in EMS operations as some pilots obviously underestimate the potential for a CFIT accident. Better training would definitely help. I think climbing is normally the best option, however, Jon’s point is well taken and EMS pilots who could be put in an inadvertent IMC situation need to be sure they perform reasonable due diligence.

Another good question is whether all EMS operations should be flown under IFR. That’s coming up next.

The helicopter EMS industry has been suffering through the worst accident rate in its history. In fact, according to the NTSB, 2008 was the deadliest year on record with 12 accidents and a total of 29 fatalities. As a result, the NTSB has held hearings earlier this year and issued recommendations to the FAA. In a list of additional recommendations issued by the agency this month was the use of autopilots and improved pilot training.

I have flown an EMS helicopter both with an autopilot and without and I believe it is an excellent workload-reducing tool. It can also enhance safety, as many helicopter pilots are reluctant to climb into the clouds. When faced with deteriorating or unexpected bad weather, many helicopter pilots will descend to avoid entering IMC. Understandably, this comes from a lack of experience and confidence at controlling a minimally equipped helicopter on instruments, trying to contact ATC, and setting up for an approach. Moreover, adding to the urge to descend is the fact that helicopter pilots know if they can recover back to visual conditions they can always land. However in many cases it is much safer to climb.

In a 2006 report the NTSB said HTAWS (Helicopter Terrain Awareness and Warning Systems) might have helped pilots avoid terrain in 17 of the 55 accidents analyzed. However, when a pilot receives a terrain warning he or she needs to be comfortable climbing if necessary and an autopilot can be a big help.

The NTSB report also calls for improved pilot training. Training pilots to engage the autopilot, initiate a climb, contact ATC, and set up for an instrument approach will give them the confidence to use that option when appropriate. Autopilots, HTAWS, and other advanced technology tools for enhancing safety must be accompanied with the proper training to be truly effective. With the recent advances in computer technology, helicopter simulation has become realistic and less expensive.

I believe the NSTB has done a good job identifying some solutions that might truly help reduce the accident rate.

For a helicopter pilot, one of the more difficult anti-torque system failures to deal with is when the tail rotor thrust becomes fixed or limited to a certain amount. This could happen if something jams or blocks the pedals or the associated linkage.

In flight, the pilot needs to determine at what position the pedals became stuck. In a counterclockwise turning rotor the more power a pilot is using, the more left pedal input is required. In this case, the left pedal is often called the power pedal. Should something jam the pedals during a high power take off or at maximum cruise speed, the tail rotor will be producing a lot of thrust.

The following illustrates the challenges of performing this type of emergency landing. As the pilot slows the helicopter to attempt to land, the helicopter approaches its most efficient airspeed (normally about 60 knots). The pilot must reduce power to prevent the helicopter from climbing. This would normally require adding right pedal, but since this is not possible the nose will start to yaw left and if airspeed gets too slow the helicopter will start spinning. The only way to stop the left yaw or spin is to add power, but that makes the helicopter climb and that’s not good because the pilot needs to get close to ground to land.

Some instructors have different techniques to land with a stuck left pedal. One method is to approach the longest runway available at cruise speed. This keeps power high and the helicopter pretty much in trim. Since the nose is trying to turn left, the tail wants to move right so finding a runway with a right crosswind will help the vertical fin oppose the left turning motion. Once over the runway, slowly start to decelerate with aft cyclic. As the helicopter’s airspeed decreases the pilot will need to reduce power. Lowering the collective should be done as carefully as possible as the nose will begin to yaw left. As the airspeed continues to drop below 60 knots the airflow over the vertical fin will at some point no longer be able to prevent the helicopter from spinning. The good news is that as the helicopter continues slowing below 60 knots more power is needed. Timing is critical as the pilot needs to keep adding power to prevent the helicopter from spinning, but can’t add too much power or the helicopter will climb. If all goes well and the pilot is able to get the helicopter to a very low hover with little or no left spinning, he or she will have the best chance to put it on the ground without rolling over.

A stuck right pedal makes it a little easier to land because in this case the pilot needs to keep power low. A common low-power landing maneuver in a helicopter is called a running landing. Since hovering requires more power, the pilot would touchdown on a flat smooth surface (a runway for example) with forward speed allowing the helicopter to slide to a stop. It must be performed carefully and is a maneuver that student pilots practice.

Different helicopters and situations will require different procedures. For example, in a clockwise turning rotor the same concepts apply, however the yawing direction and pedal inputs are reversed, as the right pedal is the power pedal. When provided, the manufacture’s recommended procedure should be followed.

A conventional tail rotor arrangement dates back to the first helicopters designed and produced. However, in addition to the added complexity of drive shafts, bearings, and gearboxes, tail rotors are noisy and susceptible to foreign object damage. In the 1970s engineers at Hughes Helicopters began working on concepts to eliminate the tail rotor for the US Army. They used the acronym NOTAR for NO Tail Rotor. In December 1981, Hughes flew an OH-6A fitted with a version of the NOTAR design for the first time.

The technology that made this possible is based on the Coanda Effect. Discovered in 1932 by Henri Coanda, it is the tendency of a fluid jet to adhere to a solid wall even when the wall curves away from the jet’s axis or direction. The NOTAR system takes advantage of this effect by using an enclosed fan driven by the transmission to force low-pressure air through two slots in the tail boom. This causes the rotor downwash to hug the contour of the tail boom creating a lateral lift vector that counteracts the majority of the rotor torque. The remaining rotor torque and directional control is managed by a direct jet thruster, which is controlled by pedal input.

The system works well and reduces the possibility of loss of directional control from tail rotor strikes in confined areas. Safety of offsite landings where personnel are walking around an operating helicopter is also enhanced. In addition, the system helps reduce maintenance costs and extends the life of structural components by reducing the vibrations levels that are caused by a high-speed tail rotor.

Three years after the NOTAR helicopter’s first flight Hughes sold its helicopters business to McDonnell Douglas. In May of 1990, McDonnell Douglas flew the first civil production NOTAR model, the 520N. In 1997 McDonnell Douglas merged with Boeing to become the Boeing Company. In 1999, Boeing sold the former MD commercial helicopter product lines to MD Helicopter Holdings Inc., but maintained the rights to the NOTAR system.

MD Helicopters Holdings Inc. was acquired in July 2005 by Patriarch Partners, LLC, an investment fund. The company was recapitalized as an independent company and is based in Mesa, Arizona. It currently manufactures several models with the NOTAR system. More information can be found at MD helicopters website.