Test: Mil Mi-28NE

Protection. If Mi-28NE could be summed up in one word it would be this: protection.

The pilot who occupies the command position of the "Night Hunter" feels absolutely protected in the fully armored cockpit.

After the Aviation of the Brazilian Army (AvEx) began the work to test foreign attack helicopters, some models were selected as possible candidates for comparative analysis, since they could meet the requirements issued by the Army Aviation Command (CAvEx). In this context , the representatives of  Rosoboronexport in Brazil formally invited the Mil Terra Operation Command (COTER) to familiarize themselves withl Mi-28NE, offering a full visit to the simulation center, manufacturing facilities and logistics supply center . Thus, I have arrived to Russia as a member of a multidisciplinary team of the Brazilian Army (EB), including COTER (Ground Operations Command) personnel, flight test pilots from the GEA and CAvEx Army Aviation Material Directorate (DMAvEx).

The first destination was the Training Center of the company CSTS Dinamika, in Moscow, responsible for the simulator training of the Mi-28NE attack helicopter pilots. The equipment we saw was a Flight Training Simulator which is a fixed platform with a full range of scenarios of helicopter operation giving the opportunity to practice using all helicopter systems. The simulator has two seats, one seat in the front part for the pilot-systems operator and one seat behind for the pilot-in-command to fully recreate the real life cockpit of helicopter. On-board systems, their arrangement and control are the same as on a real helicopter.

The distinctive feature of the Russian aircraft according to our opinion was the duplication of the digital multi-functional display with the analog one making the instrument panel rather comprehensive.

After takeoff and starting to hover IGE (in ground effect), I noticed that the aircraft was hard to control. The oscillations occurring in ground effect at zero speed require concentration and efforts from pilot to maintain the aircraft in the desired position. However, after a few seconds the large Mi-28NE became more controllable until it was completely stable. Before commencing the flight, the chief instructor explained why these oscillations occur, he intentionally turned off autopilot and attitude control system (according to the flight manual it is prohibited to fly the helicopter with these systems disabled due to dynamic instability of the Night Hunter). Controllability qualities of this aircraft in the case of unprepared flight were impressive.

After the trial piloting in the simulator, we were to verify the operation and characteristics of the control center of the system, where is the responsible for the instruction of the pilots. Being an FTD, the control station proved to be quite simple, but functional. The instructor has the possibility to choose which point of view the rotorcraft wants to observe, alternating between external views of the helicopter or flight instruments or views of the visual field of the pilots from the cockpit. Also there is a possibility of simulating failures and various malfunctions of the equipment.

Considering the structure currently available in the Simulation Division of the Army Aviation Instruction Center (CIAvEx), this type of simulator would fit easily, without the need for investments to adapt to AvEx. The simulator, after evaluations, was considered satisfactory for its purpose: adaptation of the pilot to the operation of the onboard systems of the helicopter.

We then proceed to Rostov-on-Don, where is Rostvertol, the enterprise that produces Mi-28NE (as well as Mi-35M used today in the Brazilian Air Force). There, after a formal reception, we received a full briefing from the various representatives of the company: executive director, chief of flight test station, head of the logistics division and staff of the commercial area. Prior to AvEx's interest and the tests we planned to carry out, the company's staff highlighted the history of the relationship with the FAB, involving the delivery of the aforementioned Mi-35Ms and the logistical issues for their operation in Brazil.

Going into testing activities, the Mi-28NE's external observation gives us the initial impression that it is quite large for an attack helicopter. Particularly, its tail boom is long compared to the Western analogues. The rotorcraft made available for the evaluations had registration "218".

This classic-scheme helicopter belongs to medium helicopter class. Main rotor has five blades with an asymmetrical air foil, its tail section and spar are made of composite material. There are two tandem seats in the cockpit, rear seat for pilot-in-command and front seat for pilot-operator. The Mi-28NE was designed to perform the following missions: attack, reconnaissance and attack; surveillance; armed air escort; precision strikes; fire support, and ensuring security in urban areas.

There are two wing panels (suspension units) on both sides of the fuselage, on which weapons or auxiliary fuel tanks can be mounted. Each wing has two suspension points for 500kg each, meaning that each wing is capable of carrying 1,000kg of equipment and / or armament.

The Mi-28NE standard armament includes NPPU-280-1 rapid-fire single-barrel 30 mm gun, model 2A42, on a turret. The IR TOES-521 system controlled by the pilot in the rear cabin gives the ability to select and send several types of targets to the pilot-operator. This operator has the OPS-28 target sight system, a target selection system, threat sensor and IR camera, which team to provide more advanced features than the TOES-521 system.

The aircraft has armored cockpit, its windshield withstands impact by 12.7 mm bullets, while the cockpit is able to withstand 20mm shell fragments. Main rotor blades are capable of resisting the impact of projectiles even greater than 20mm.

The Cockpit

The pilot-in-command’s station is located in the rear cockpit; equipment and switches are positioned on the front panel and side consoles on the left and right sides of the pilot. The cyclic control stick is of the conventional type, that is, located between the legs of the pilot and the information is transmitted to him by means of two MFD, by analog indicators and a HUD (Head-Up Display). Engine controls, both for start-up and for power adjustment, are located on the left side console. In this location is also the control panel of an autopilot, which in this rotorcraft has the great function of keeping the "monster" dominated and controlled. As mentioned previously, some information is passed to the pilots through MFD, and all are compatible to the flight with Night Vision Goggles (NVG), classes A and B.

The automatic pilot, or AFCS (Automatic Flight Control System), has two major modes of operation: full 4-axes control and stability augmentation system (SAS). The first allows long-term stabilization for a "hands-off" flight situation and can be coupled with the director control. SAS already provides short-term vibration control for hands-off flights.

Flying with the autopilot system switched off or failing is prohibited - possible, but prohibited.

There are also analogue indicators, which, under the conditions evaluated, showed good illumination and visualization. However, as we observed in the simulator, the units of speed, altitude and altitude variation are provided in "km / h", "meters" and "meters /minute". The manufacturer clarified that if this model is purchased, the panel can be adjusted to the western indication pattern without major problems to meet the AvEx's operational requirements.

The armored and jettisonable rear access door is on the right side of the rotorcraft. Next to the door there is a pneumatic system that inflates a ballonet (similar to an escape slide) to assist the pilot in case of emergency exit and parachute opening. Yes, when flying the Mi-28NE, you use a parachute, and certainly the reader, like us, is curious to establish "how" the pilot does jump from a helicopter on a parachute, since there is a "big slicer" over the pilots' heads. The Russians' response to the system is even more astonishing: "the pilot levels the helicopter, activates the pneumatic system, and when the door is knocked off, the ballonet inflates automatically and the pilot is' thrown 'out of the rotorcraft where he can open the parachute safely ... "But then the curiosity gets even sharper:" what if it is not possible to level the helicopter? "Again the simplicity of Russian thinking surprises us:" In this case the pilot stays in the rotorcraft!". As, I should note, in any other helicopter.

The front cockpit is intended for the positioning of the crew member responsible for the rotorcraft's weapon system, however, this position is also used by the flight instructor when training the new pilots. At this location are the controls of the helicopter's electronic and weapon systems. The main information is transmitted to the weapons operator through two MFDs, as well as analogue instruments. The front door, which is also armored and jettisonable, is on the left side of the helicopter and has the same capabilities for the emergency escape.

Both cockpits are fully pressurized and sealed by a system, allowing their use in chemical, biological, radiological or nuclear warfare environments; having a system for flight in high altitudes constituted by an oxygen generator set and mask with capacity to provide one hour of flight in these conditions.

Main and Tail Rotors and transmission

The main rotor is built with the use of elastomeric bearings performing the function of three joints and above its hub the helicopter's mission radar is installed. The blades’ oscillation is damped by hydraulic dampers that have resilient rubber elements at this joint. The rotor hub is composed of the case made of titanium, elastomeric bearings, dampers and pitch control levers. The tail X-shaped rotor is also three-hinged, equipped with elastomeric bearings, which allow the movements of the blade within the plane of rotation. Its design and location are intended to reduce noise and increase efficiency of helicopter control.

The Mi-28NE is equipped with two VK-2500-02 turbo-shaft engines, which are TV3-117 series modifications. Each engine delivers 2,200hp in takeoff mode. They are installed externally on the fuselage in engine bays and a side axle connects the engines’ shafts to the main gearbox case. This propulsion system is also composed of the following equipment: APU AI-9V auxiliary power unit; lubrication system; engine air particle separator and exhaust heat shield.

The internal fuel capacity amounts to 1,317 kg of aviation kerosene, which, under conditions of maximum continuous power, allows two-hour flight autonomy. For longer sorties there is a possibility of using external tanks, which also have self-sealing characteristics. It is also worth noting that the fuel system is fully pressurized, that is, it allows the accomplishment of maneuvers with low fuel reserve without compromising the power of the engines or leaks.

Protection and Countermeasures

The rotorcraft's protection and countermeasures system is designed to alert the crew to hostile radar or laser illumination and aiming/firing of air-to-air or ground-to-air missiles. Altogether, there is a Laser Warning Receiver, L-140E, which detects laser emitting from ground or in air, "illuminating" the rotorcraft, and identifies the type of threat (missile or rangefinder ), elevation angle, azimuth angle in relation to the rotorcraft in a sector of 15º and provides information about the type of armament that is illuminating.

The L-150-28E alert radar performs the identification of radio-electronic weapon control systems, has an active recognition and indication system that informs the direction and type of the radar emission. The system also measures the frequencies of received signals and identifies the type of emitting radar.

Finally, embedded countermeasure systems consist of flare dispensers located in the wing tips’ containers.

Mission Radar

The helicopter carries the N-025 airborne radar, which is installed above the main rotor hub, and can operate in the following modes: ground surveillance, detection of obstacles during flights at low altitude and combination of these two modes.

The capabilities of this radar system are as follows: standard or continuous scanning; microplan mode (mapping); indication of azimuth and distance to targets; selection and automatic tracking of targets.

Evaluations and Tests

In vertical take-off maneuvers, hovering in ground effect, air taxiing and vertical landing, the Mi-28NE demonstrated good flight performance despite its size and weight. The responses to the pilot did not allow rapid movements like those obtained in light aircraft such as Fennec of AvEx. However, this aspect could be compensated by the great armored protection, which is confirmed by the analysis of the helicopter’s ability in air combat with lighter and agile attack aircraft , but less armed and / or armored.

In normal takeoff and horizontal flight the rotorcraft showed a smooth behavior without losing stability. There were also tactical maneuvers typical of AvEx, fulfilling a high-speed flight profile only 5.0 m from the ground.

But in discussions with former Russian military pilots we have seen that helicopter employment tactics in the Russian Armed Forces itself is quite different from that of AvEx, with Russians acting on the standard scenario of full airspace control and, given the large armored protection capability, the flights at such low altitude are not required.

Combat Maneuvers

Before the beginning of the flights a quick adaptation to the helicopter was performed with basic maneuvers like take-off, landing and maneuvering near the ground. At the first takeoff, you can feel the strength of the rotorcraft's big engines and the great weight of the armored colossus. I confess that upon returning to Brazil, after the first question on "How is the helicopter?", I told my colleague: "It seemed that I was performing the flight hovering in an Army M113 armored personnel carrier."

After takeoff and air taxiing, I was able to verify that the adaptation is quick, particularly after the flights in the simulator: the rotorcraft showed the responses expected from a heavy and stable model. For pilots accustomed to large types such as AS532 or Blackhawk, the pilotage is similar, but with more effective responses.

I have also performed a number of maneuvers employed in combat:

“Transient turn”

The purpose of this maneuver was to check performance deterioration of the helicopter in quick maneuvers and undesired helicopter control command response lag.

The desired performance would be to complete the maneuver within 10 seconds at altitude below 60m with a maximum loss of altitude of 15.25m, and appropriate performance would be to complete the maneuver within 15 seconds at altitude below 60m.

I started turning at a speed of 220km / h, at 60m at 40 degree bank, first reducing engine power and then increasing it to compensate altitude loss. During the maneuver the bank angle reached 65º. There were no structural load limit warnings or signs of loss of control, although at the beginning of the turn to the curve the rotorcraft had a tendency to climb, which was compensated to maintain the expected parameter of the maneuver.

In the conditions evaluated, the Mi-28NE showed a tendency of lateral rotation and pitch-up that had to be compensated by the pilot. And the turn was completed in 18 seconds, with altitude loss of 6.0m. For a time comparison basis of this turn, the AvEx rotorcraft Fennec completes the same maneuver in 9 seconds. The weight and inertia of the MI-28NE explain this difference to AvEx's much smaller aircraft.

“Slalom”

The maneuver, which consists of crossing a line of obstacles in front of the rotorcraft, curving back and forth as a kind of "snake" on the ground, started in a level flight at 15.25 m and speed of 166km/h, and it was established that the desired performance would be to maintain the speed at least 148km/h and maintain the height below 18.3m, while the appropriate performance was to maintain the speed of at least 130km/h and the altitude of +/- 15.25-6.0m.

The desired performance was obtained because the helicopter allowed stabilized bank angles that, combined with the great inertia, were in charge of taking the aircraft to the desired position, making it possible for the pilot to stop the movement and to prepare the turn of the rotorcraft around the next obstacle.

Maneuverability and control capability are highly desired in attack helicopters, particularly during successive changes in flight direction at medium speed; and it was possible to position the Mi-28NE exactly in the planned points.

“Tactical landing in “U”

The maneuver, typically used in AvEx, aims to see the ability to perform the prompt landing in a position located on one side from the rotorcraft in the shortest possible time in order to quickly escape the detection and adversary fire.

The maneuver was commenced at the altitude of  30.45 m and with a speed of 148km/h. Once the landing site was identified, the power was quickly reduced and as soon as the rotorcraft began to lose altitude, a quick right turn was made to reach the initially desired touch-down location.

The helicopter, despite its inertia and size, showed a good response to the command, allowing a rapid and steady descent with a sharp curve to the right, landing in the desired location.

“Tactical take-off in “U”

After the tactical landing, another maneuver was performed much used in the AvEx for the abandonment of areas of observation or repositioning of the helicopter. In this maneuver, from the hovering, the pilot initiates a lateral movement and, as the rotorcraft gains speed, the pilot allows the aircraft to spin on its axis, still accelerating. At the end of the turn, in the direction opposite to the initial, the helicopter continues the flight at low altitude or the takeoff.

In the tests performed, the rotorcraft reached the end of the turn at a speed of 92.5km/h, the desired parameter to safely continue takeoff or tactical displacement. No significant pilot command compensation was required, which facilitated maneuver execution and control.

The helicopter ability to perform lateral shifts followed by takeoff is a desired feature for tactical use, since in case of firing or observation, the rotorcraft must be able to quickly take off and continue the mission, even in the opposite direction.

“Quick startup and take-off”

Among the important maneuvers for attack rotorcraft is the ability to perform deceleration and instantaneous hovering en route during nap-of-the-earth flight. The flight itself and changes in flight direction occur dynamically and, in case an adversary is detected, helicopter hovering without changing the altitude guarantees safety of operations.

The maximum altitude variation of +/- 3.0m and maximum in the heading of ± 5º during stabilization was considered a desired parameter. The helicopter was then placed in rapid acceleration mode and, when reaching 185km/h, the power was reduced for 3 seconds until the indication of torque in each of the engines was 2%. When the speed reached 74km/h, the stop was commanded by performing a pitch-up of 30º. At the moment, the visual field ahead was totally covered up for the pilot, however, side observation allowed the crew to have a perfect view of the ground. When commanding the stop, the rotorcraft showed a tendency to lower the tail too much, fact observed and promptly corrected by the pilot. The performance was considered satisfactory.

Conclusion

The tests proposed to the GEA were partially fulfilled, since some flight profiles were not authorized during that visit. The results obtained were considered satisfactory, with some opportunities for improvement. Certainly, in case of option and pre-selection of  Mi-28NE there will be the demand for new flights, particularly under IFR and with the use of Night Vision Goggles.

The weapon system and radar system display the target information and active weaponry at the HUD, and the information, under the conditions assessed, was clear and easy to interpret for the pilot. At the time of our test, an HMD (Helmet-Mounted Display) was not available at Mi-28NE, while the HMD is a mandatory requirement issued by AvEx. However, today such a system is already available and operational for the Russian helicopter.

Major Thiago Fatorelli is Head of the Army Aviation Testing and Assessment Group (GEA).

The article was first published in ASAS magazine (Brazil), issue 101.