Flying the Tank Killer - Rooivalkby Charlie Marais
The night was dark. No moon, just stars. We were moving at about 25 knots forward speed at a height of 25 feet. Yes, we still fly in feet, though the rest of the systems are metric. The radar altimeter bug was set at 20 feet. The audio that sounds when the height is bust, is not mistakable as the height bar on the flat screen flight page also turns red. Situated in the right hand lower corner, the height bar is easily distinguishable from the other 12 "instruments" represented on the flight page. You would not cancel the audio, but acknowledge the potential emergency by simply saying, "climbing" as you pull Collective Pitch (CP) and thus power to restore the height above the bug setting.
Out here amongst the riverbeds and small hills, this night felt especially dark. The night vision goggles (NVG's), through which the night outside appears in shades of green, from light to dark and then finally black, makes little white sparkles. A sign that says it is dark and the only light available for the goggles to enhance is starlight. It is feeling pretty dark, especially as this is the first night we explore category three NVG flight, or flight in the nap of the earth sphere between ground level and 50 feet in "dark moon" conditions. On bright moon nights we could easily proceed at double the speed at this height, but that again depends on terrain features and obstructions in the way. Haste is not the idea. To reach the firing position undetected is vital for mission success and that is our primary concern for this flight.
Not this night; the natural feeling when struggling to see is to slow down and fly the Rooivalk Attack Helicopter at between 45 and 90 degrees sideways. The visibility through the large cockpit side windows allows obstruction free viewing. Flying or tracking sideways is a smooth and comfortable manoeuvre in the Rooivalk. A very ingenious vibration isolation system installed between the main rotor head and body of the helicopter ensures that virtually all the vibrations around the 17-hertz frequency are fed back to the source and are thus nullified. Unnatural is the only way to describe a near vibration free helicopter. No other helicopter of the many types I have flown afforded such a smooth ride. When compared to Apache and Tiger, old technology rattle boxes come to mind. But this is the kind of stability one needs to guarantee a perfect launch when utilising smart weapons such as the Mokopa tank killer.
To come back to side tracking. Flying so close to the ground makes pitching moments around the lateral axis quite dangerous as the helicopter tail could easily strike objects, resulting in possible catastrophic failure of a main component. You only need to see "Black Hawk Down" to understand the consequences of losing a tail rotor. For this reason all stopping manoeuvres in the nap of the earth environment is performed in a sideways fashion. Rooivalk loves side stopping and side tracking as even in these circumstances the vibration levels stays zero for all intent and purposes. Yes well, there is still a little translational judder, but only in a very narrow speed band, and also much less pronounced.
As we approach a high-tension (HT) power line I set the bug to 5 feet. As sight through the NVG's is like flying in a tunnel without peripheral vision, a continual scan through 180 degrees is maintained by turning your head from side to side, but not when flying underneath HT wires. The wires are normally not visible through the NVG's, only the pylons or poles, so continual scanning is to ensure no surprises in smaller electrical and telephone wires. The Rooivalk is equipped with wire cutters for just such occasions, but their effectiveness would be zero if encountered sideways. Going under the wires is much safer when a fixed point on the other side of the wire is selected and the helicopter flown in a straight line towards it. The flight path is normally close to the pylon so as to have maximum wire clearance above the helicopter. Flying towards the chosen point ensures that there is no possibility of striking blades on the pylon. Setting the bug at 5 feet and then flying so as to trigger the audio ensures a flying height of less than 5 feet. Should the audio go quiet, the height bar turns green and it means that you are now closer to the lines as you pass beneath. Flying in the red thus means maximum separation between the main rotor head and HT wires is guaranteed.
Coming up to the firing position chosen at 6 kilometres makes it time to utilise the main sight to acquire and lock onto the target. The powerful zoom quickly confirms the target as a group of tanks. The front one is selected as its breakdown would block the passage for the rest and give us more time to take out the other seven. The powerful laser ensures a lock on and the launch goes without a hitch. Not waiting for the hit, which we know has a 95% probability, we reposition so as to avoid detection by the enemy. On reaching the second firing position, with no background hills to mask us, I simply ease the helicopter higher amongst a clump of trees. Our Rooivalk becomes just another tree and is not detected by man or radar. Too much clutter from the ground to see us and we are out of earshot.
The success of the first launch is clearly visible through the main sight. In the ensuing pandemonium each of the tanks get its turn to be destroyed. The same technique is used to egress from the firing positions as we take care to end the mission in one piece. This flying tank killer has once again proved to be far superior to any other weapon designed for combat support in the anti-armour division.
In this combat mission very little combat manoeuvring was required. Seeing the Rooivalk flying displays at air-shows and other aviation events, led to a few ideas born and certain misconceptions taken as fact. Firstly it looks so easy to fly that everyone flying helicopters at shows started to copy the manoeuvres. The question should not be if the manoeuvres performed are easy, but rather if your helicopter is flown within its design capabilities when you zoom about at an impressive sideways and rearwards estimated speed, but non-quantifiable as you do not have the instrumentation. Rooivalk is equipped with an omni-directional airspeed indicator. The sensor is positioned above the main rotor disc on top of the main rotor shaft. So, no matter what direction the Rooivalk is manoeuvred in, the air speed is at hand. One of the pre-production model Rooivalk was wired and the complete display or combat flight envelope measured. All the manoeuvres performed at air shows are more aggressive versions of manoeuvres used in combat.
During combat the helicopter would be much heavier and the manoeuvres performed scaled down in aggressiveness to conform to basic aerodynamic principles. Yes, we always apply the basic principles for all flight conditions and to determine sortie profiles. Rooivalk was tested to extremity, thereby ensuring all manoeuvres as prescribed to be inside Alpha limits. There are definite manoeuvres where it is extremely easy to venture into Beta limits and those will drastically limit component life. Such a manoeuvre is the loop and roll that has previously been performed by test pilots in the Rooivalk, but stopped because of sound financial reasoning. Yes, she can still perform a loop, but at a price. As your helicopters have no fatigue measurement capability directed at hard manoeuvring, I would suggest you refrain from copying manoeuvres that look easy, probably are easy to fly, but not cleared by the manufacturer.
Okay, so Rooivalk is tested and the manoeuvres are flown inside specific "g" limitations, roll-rates, yaw or pedal turn rates as well as engine handling specifications. Besides, I was taught by Tim Maice, a British subject qualified as a helicopter test pilot, aerobatics instructor and judge. We now perform the so-called inclined loop or for short I-loop. When performed towards the spectators, the optical illusion still persists of a loop proper being performed - I mean, loops the crowds want, so loops they get. During the initial pitching, the helicopter is banked by approximately 15 degrees or more from the normal/vertical. Pitch-up is regulated at two "g" and power is applied as the helicopter is pitching through 45 degrees nose up attitude. Power is slightly reduced at the apex as a torque spike is encountered. Positive "g" is maintained all the time and all manoeuvres are limited to between 2,2 and 0,5 "g". The closer the I-loop is performed to the vertical or normal, re-circulation and the associated vibrations will be encountered just past the apex. On a hot day in Pretoria with the density altitude way past 7000 feet and the Rooivalk weighing 7 metric ton, I add at least 100 feet to the display height to facilitate recovery from such conditions.
For the record, it is not a good idea to fly by the seat of your pants when performing such heavy helicopters in extreme manoeuvring. Your instruments play a vital role in triggering you what you have to do when and how much you can do with how much you have got, if you know what I mean. So seat of the pants as well, but very definitive instrument assisted.
Wind plays a major role. Into wind can only happen at best through half of the manoeuvres. Besides, in the battlefield one cannot plan for wind, you take what you get and you better know what you have to do with it. Another 100 feet added for good measure and wind normally makes everybody who does not know, complain about a display height of above 250 feet. The Americans call leaving yourself scope to manoeuvre the "fudge factor". I like that. Here I am talking air show and not combat, so do not get all depressed because of how high we are above the ground. In combat you would not see a Rooivalk so high above the ground; it would be suicide.
Performing the porpoise is like manipulating your own roller-coaster ride. The manoeuvre was so called as it reminds of the manoeuvre that a dolphin does when surfacing and diving in its quest for a fresh breath of air. Pitch-up is about 75 degrees and as the helicopter starts rearward flight, a controlled bunt is performed to 70 plus degrees below the horizon. When I watch the ground head-on, I'll swear it is closer to 90 degrees. This equates to 0.5 "g" prior to accelerating for the next manoeuvre. Speed throughout the display is between zero and 110 knots.
Rearward flight is one of the more exiting manoeuvres. Limited to 45 knots for normal flying, speeds up to 86 knots have been claimed by the test pilots. I know, I was there. It is like flying a dart the wrong way around. Extremely unstable in the longitudinal axis and great care has to be taken to maintain a straight flight path parallel to the longitudinal axis. Any slight deviation in heading from this would result in weather cocking, forcing the nose to yaw into the direction of flight. Very much so as a dart that was thrown tail first would do to still pin in the board. Should this happen, as the forces are already outside tail-rotor control effectiveness, you just hold on as she settles herself. You are a passenger for the quick turn about. Then you take control and try again. Not dangerous, but uncomfortable. That is if your helicopter is stressed to handle such sideways forces.
With Rooivalk's design it is apparent that it actually has no definable tail section. It just happens to be where the tapered body comes together. Thus a very strong design and fully capable of withstanding sideways forces well in access of 80 knots. Yes, the only reason we cannot fly faster than 60 knots on a side pass is because the tail rotor control is not capable of greater blade deflections. Once again the omni-directional airspeed indicator comes in handy, but as you accelerate past 60 knots side ways you run out of opposite pedal deflection and weather cocking will again force the nose of the helicopter in the direction of flight.
Oh, I was about to talk about the rearward acceleration. Starting the manoeuvre from the hover is optional, but most spectacular, especially when facing the spectators. From the hover a 40 degree nose-up attitude is selected. Simultaneously power is increased to around 112% on the total torque gauge. Not to worry, this is still in the orange arc and well within power or total torque limitations. Engine torque will be less than 100%, I know, because the other main function display page is now set on the engine page. So you monitor both.
She is now accelerated in level rearward flight until 65 knots on the clock. As pitching is also very sensitive and unstable, the cyclic is moved forward as a thought rather than a physical action. The nose now pitches down with an ever-increasing rate as the tail-section changes its angle to the relative airflow from behind. Great care is taken to regulate the pitch rate, as control could be lost in an instant. Normally resulting in an over-pitch with the nose passing 90 degrees down with the associated negative "g", and for helicopters negative "g's" below 0.5 is normally unhealthy. I am talking about non-ridged rotor heads, so hold your horses. The Rooivalk's main rotor head is of the articulated type, not even semi-ridged, so aerobatics are actually not part of the flight capability. The nose down pitch is stopped at as close to 90 degrees (I suspect between 70 and 80 degrees, but it seems more from the outside) as you can get below the horizon and a "vertical" 90 degree turn is performed along the longitudinal axis. An excellent manoeuvre for adrenaline junkies at 300 feet above the ground, facing the ground head on!
Banking a helicopter past 90 degrees when performing a wing-over is old hat. The Puma pilots of yesteryear performed these with great finesse, but it still gives you the chance to see the ground through the blades from a near total upside down position. With no switches in the roof, proof that it is not a transport air vehicle, there is nothing to obstruct your view. This would be the case in chandelles', I-loops and high or steep wing overs. But seeing the blades between you and mother earth makes me feel like I could cut grass.
The front cockpit is there for utilising the main sight and firing smart weaponry. Rockets and gun ass well, but those can be fired from the rear cockpit in self-defence of the helicopter. The front cockpit has a full set of controls, but you cannot start the engines from there. The Weapons System Operator (WSO) occupies the front seat and the pilot the rear seat.
I call the front cockpit the "lonely cockpit". Sitting in the front with no part of the helicopter visible, makes me feel like I am in a space fighter as seen in Star Wars. The glass cockpit with its modern design and colourful lighting makes for an unforgettable experience during night sorties. From the rear cockpit one can at least see the front cockpit, engine air intakes and with a slight twist of the head even the armament racks on the stub wings. A spacious cockpit with virtually all systems at the command of your fingertips. As there is no scope for "head in the cockpit" when flying so close to the ground, all controls required by the pilot and WSO are either on the collective pitch lever or cyclic stick. The so called HOCAS system denoting Hands on Collective and Stick. This interface with the helicopter makes it safe to operate low level with heads out the cockpit, but needs a lot of practice not to press the wrong button on the controls. To practice switch-ology on the ground a suitable simulator was designed and put to good use. Pressing the wrong button could make this 8 metric ton beast somewhat cross which could lead to some misbehaving on its part and stained undies on the crews part.
One of the main design drivers was to take cockpit load away from the crew so that the pilot can fly "head outside the cockpit" while the WSO gives his undivided attention to operating the main sight. That is where the monocular designed heads-up display (HUD) helmet, an electronic marvel and excellent piece of engineering, comes into play. With a head tracker installed, the forward-looking infrared (FLIR) and 20 mm cannon are synchronised to instantaneously follow head movement. The sight information is silhouetted in the HUD and where you look, you can shoot! Not the Mokopa, as the missile has to be laser locked before launch. And then naturally there is the built in NVG with the image also displayed on the full face of the HUD. For those who are flying the normal NVG head gear, this is like the future.
Yes, it is a privilege and great fun to fly the newest technology on the block. With excellent handling capabilities and stressed to do the job, the question still remains what I personally prefer to fly. Is it the Alouette III, the Puma, the Oryx, the Rooivalk or even the MI8/17? Or is it one of the few civilian types that I have had the pleasure of flying? The answer is quite obvious - "out of all the types I must confess to prefer to fly helicopters". After all, to fly is heaven, but to hover is divine!