TERF

Taken from Air NTTP 3-22.3-CH46E

2.1

Terrain Flight
2.1. Terrain flight (TERF) is the employment of an aircraft in a manner that utilizes terrain, vegetation, and man-made objects to enhance survival by degrading the enemy’s ability to visually, optically, aurally, and electronically acquire and target the aircraft. It involves a constant awareness of the positions and capabilities of enemy weapons and acquisition systems in relation to the route of flight and en route terrain. TERF encompasses those tactical flights in which the intent is to fly at or below 200 feet above ground level (AGL) using low-level, contour, or nap-of-the-earth (NOE) flight techniques to counter an enemy’s capability to acquire, track, and engage the aircraft.

2.1.1 Low-Level Flight. Low-level flight is conducted at an altitude where detection and observation of the aircraft are avoided or minimized. The flight route is pre-selected, generally straight-line, and flown at a constant airspeed and indicated altitude of 100 to 200 feet AGL. Figure 2.1, Terrain Flight Profiles, illustrates the low-level flight path.

2.1.2 Contour Flight. Contour flight is conducted at an altitude which conforms generally and in proximity to the contours of the Earth’s surface. It takes advantage of available cover and concealment to avoid an enemy’s observation while maintaining airspeed (above 40 knots). It is characterized by varying airspeed and altitude as terrain, vegetation and obstacles

2.1.3 Nap-of-the-Earth Flight. Flight that follows as close to the Earth’s surface as vegetation and obstacles permit is called NOE. It is characterized by varied airspeed of 0 to 40 knots and an altitude of 10 to 50 feet AGL as influenced by terrain, weather, ambient light, and the enemy situation. The pilot preplans a broad corridor of operations based on known terrain features with a longitudinal axis pointing towards the objective; while flying NOE, the pilot uses a weaving and devious route within the corridor and oriented along the axis to take advantage of the cover and concealment afforded by terrain, vegetation, and man-made features. Figure 2.1, Terrain Flight Profiles, illustrates the NOE flight path.

2.5.3

Helicopter Maneuvering
. The altitudes associated with terrain flight require that certain maneuvers be performed with due consideration to terrain clearance. In no event should these maneuvers be attempted if the pilot feels that minimum power requirements are not met.

2.5.3.1 Masking/Unmasking. Masking and unmasking from a covered position during terrain flight is performed from a hover. The maneuver is used when a view beyond the terrain is needed to increase situational awareness about the enemy threat or the route of flight. Maintaining the aircraft in a covered and concealed position behind a terrain feature while in a hover achieves masking of the aircraft. Special care should be taken to reduce the rotor wash signature in the masked position. Unmasking is achieved with a coordinated increase of collective to raise the aircraft out of the masked position and slightly above the terrain feature so that visual reconnaissance of the area can be performed. Exposure of the aircraft in the unmasked profile should not be longer than 10 seconds. Unmasking can be performed laterally as well with inputs to the cyclic to either side of the terrain feature.

2.5.3.2 Quickstop. The quickstop is a maneuver designed to slow or stop the helicopter at a high rate of speed in the TERF environment. Tactical emphasis when performing the maneuver is placed on maintaining the aircraft in a tactical profile or masked position while maintaining proper aft rotor clearance. The quickstop is a coordinated maneuver of applying aft cyclic and lowering the collective, while maintaining heading control with pedals. The helicopter must rotate about the aft tip-path plane in order to maintain proper dictate. Altitudes for contour flight are 50 to 100 feet AGL. Figure 2.1, Terrain Flight Profiles, illustrates the contour flight path.

2.5.3.4

Bunts
. When high terrain that is perpendicular to the route of flight is unavoidable and must be negotiated, bunting the aircraft over the terrain feature will maintain the tactical profile of the aircraft the longest and minimize exposure time. Approaching the terrain feature, acquire and maintain only enough altitude to clear the obstacle. Once clear, lower the nose and immediately reduce power to descend into a masked position while keeping the tail clear of terrain and maintaining a constant airspeed.

2.5.3.5

Rolls
. Rolls are used when a decision is made because of threat or other factors to shift the tactical flight profile of the aircraft laterally while maintaining the same general path of flight. The maneuver is initiated with a 45-degree turn toward the obstacle and at the same time applying power to climb above the terrain. Positive power remains on the rotor system throughout the maneuver. The obstacle may be crossed wings level or wing down. If crossing wing down, ensure clearance of the tip-path on the inside of the turn. Remember that turns in excess of 30 degrees make the tip-path the lowest portion of the helicopter. Upon crossing the obstacle, lower the nose and immediately reduce power as in a bunt and descend into a masked position to resume the original heading while maintaining a constant airspeed.

2.7.2

Emergencies
. The aircraft commander shall assign and thoroughly brief aircrew duties and responsibilities concerning emergency procedures. In the TERF environment, given the critical time constraints in an emergency, successful resolution requires crew member preparation especially on immediate-action procedures. Certain emergency procedures, such as dual/single engine failure, partial power loss, stability, and flight control augmentation system failures, and hydraulic failures, are far more critical during terrain flight than when they occur in flight at altitude. Most pilots need additional training and practice to develop the proficiency to satisfactorily cope with emergencies during terrain flight. Based on the narrow clearance limits associated with low altitude flight, control transfer during TERF is not recommended. Emergency training and practice shall be conducted IAW Chief of Naval Operations (OPNAV) instructions, command directives, and the appropriate NATOPS flight manual, and should concentrate on perfecting aircrew skills in the prompt recognition of an emergency situation, the prompt and coordinated initiation of immediate action procedures, precise control of the helicopter, and minimizing loss of altitude. Consider climbing out of the TERF environment if the situation allows. This gets the aircraft away from obstacles and will allow greater time to analyze and properly diagnose the emergency. It will also allow the crew to potentially land the aircraft.

2.12.1

Low-Threat Environment Departures
. Tactical departures used in the low-threat environment are designed to achieve a rapid climb to high altitude (above 1,500 feet AGL) and to minimize exposure to the small arms threat.

2.12.1.1

Spiral Climbout Departure
. This departure is executed using military power and best climb performance airspeed when terrain dictates an immediate climb on departure. AOB is adjusted to keep the climb-out path within the confines of the secure area. Steep angles of bank reduce the rate of climb and lengthen the exposure time. This technique should be used only for departures from secure areas.

2.12.1.2

Zoom Climb Departure
. This departure employs high airspeed at climb entry and Mil power throughout the maneuver to achieve a high rate of climb through the area of greatest vulnerability. After takeoff, contour flight is continued until the helicopter accelerates to high airspeed (approximately 110 knots). Once the desired airspeed is attained, begin a cyclic climb to allow airspeed in excess of that required for best climb performance to be translated into vertical climb rate. The cyclic climb must be performed smoothly to avoid blade stall. This departure uses a straight-out flight path oriented away from the threat to reduce vulnerability.

2.3

Aircrew Coordination
. TERF requires precise archway teamwork and coordination, particularly with respect to pilot and copilot/observer flight duties and cockpit coordination. Aircrew coordination is a prerequisite for safe, effective TERF. Specific cockpit duties and responsibilities may vary with the mission, tactical situation, and TERF profiles used. Aircrew duties and responsibilities shall be assigned and briefed thoroughly with all members of the flight before each mission.

2.3.1 Brief. During the mission and cockpit briefs, assign specific duties to each member of the flight. The aircraft commander ensures that crew member duties and responsibilities are understood for each phase of the flight and that each crew member is properly performing those duties. The cockpit brief should cover preflight planning considerations, conduct of the flight, aircraft awareness factors, aerodynamics, and environmental effects.

2.3.2 Pilot at the Controls. The aircraft commander is ultimately responsible for mission accomplishment. With this in mind, decide whether the aircraft commander’s responsibilities can most effectively be performed as the pilot at the controls (PAC) or as the pilot not at the controls (PNAC). Regardless, the PAC has two primary responsibilities: controlling the helicopter and avoiding obstacles. The PAC must keep a visual scan outside the helicopter and avoid distractions; particularly internal distractions that could interrupt the external scan. The PAC is also responsible for reporting terrain and landmark information to the PNAC to assist in navigation. It is essential that the PAC continuously keep the crew chief and aerial observer informed as to which way the aircraft is about to turn and the planned movement of the tail of the aircraft. The PAC must control the aircraft during emergencies and execute all emergency procedures IAW Naval Air Training and Operating Procedures Standardization (NATOPS) and the cockpit brief.

2.3.3 Pilot Not at the Controls. As dictated by the aircraft commander, the PNAC is primarily responsible for accurate navigation, remaining oriented at all times, continually informing the PAC of the route to be flown, and of appropriate airspeed adjustments required to meet timing goals. Secondary responsibilities include monitoring aircraft systems, and monitoring the performance of the crew chief and aerial observer. During an emergency, the PNAC executes the procedures required by NATOPS and delineated in the cockpit brief.

2.3.4 Crew Chief/Aerial Observer. The crew chief and aerial observer are essential parts of the crew and must be thoroughly briefed to mission and responsibilities. The crew chief is primarily responsible for monitoring the mechanical condition of the helicopter and clearing the aircraft of obstacles on the crew chief’s side and aft. The aerial observer is responsible for clearing obstacles on the aerial observer’s side and aft. If the aircraft is configured for ordnance delivery, both crew members must also be prepared to bring their weapons to bear should the aircraft be engaged. With the good visibility available from the cabin area of the CH-46E, both the crew chief and aerial observer can be tasked with assisting in navigation, looking for landmarks, and keeping a running or leg time as a backup to the PNAC timing. In an emergency, the crew chief and aerial observer are responsible for assisting the pilot with systems diagnosis, clearing the aircraft below and into a landing zone, and all other procedures required in NATOPS and briefed in the cockpit brief.