Red faces in IAF over snag in Antony's copter

Discussion in 'Internal Security' started by Someoneforyou, May 5, 2011.

  1. Someoneforyou

    Someoneforyou Regular Member

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    Red faces in IAF over snag in Antony's copter
    India - 5 may 2011

    NEW DELHI: It could have proved much worse but defence minister A K Antony was fortunate enough to escape with just a mild sunstroke. Two Mi-17 helicopters deployed to ferry Antony and his high-level entourage to forward areas in Rajasthan developed technical snags, one after the other, on Monday.

    Already grappling with a resurgent crash rate, with close to 50 fighter and helicopter accidents being recorded just since 2007, the fact that technical problems can dog even VVIP flights has come as a major embarrassment to IAF.

    "Fortunately, the rotor and power-pack problems took place while the helicopters were on the ground. If they had occurred in the air, it would have been curtains for the passengers...helicopters, after all, drop like stones," said a source.

    IAF, however, tried to downplay the episode, holding that there was "no need to order a full-scale inquiry" since they were "just some minor technical problems in starting the helicopters". Added another officer. "Sometimes in hot weather, the battery does not give optimal power... it does not mean there is something wrong with the helicopter."

    The Antony episode, however, comes in the backdrop of a spate in helicopter crashes around the country, including the one which killed Arunachal Pradesh CM Dorjee Khandu. Incidentally, Antony's entourage included Army chief General V K Singh and defence secretary Pradeep Kumar, among others.

    The two main reasons for crashes in IAF, both for fighters and helicopters, are attributed to "human errors" and "technical defects". In other words, "inadequate" training to pilots, ageing machines, shoddy maintenance practices and lack of adequate number of spares all come together to form an explosive mix. Just last year, IAF recorded a dozen crashes, which killed five pilots, 11 military personnel and four civilians.

    Sources said while the flight of the two Mi-17s from Jaisalmer to Tanot went off fine, the problems began on the way back. First, one of the helicopters developed the technical snag, leaving the "less important" among the passengers to take to the road back to Jaisalmer.

    Then, the second Mi-17, which was supposed to take Antony and the other VVIPs to the airport from the Jaisalmer military station also refused to start. This time, Antony and the others had no recourse but to travel by cars to the airport to take the plane back to New Delhi.

    Antony did not attend office on Wednesday as he was "slightly indisposed" after his hectic Rajasthan tour, which took place in blistering heat. The 71-year-old minister also has to conserve his energy for his three-day visit to Saudi Arabia and Qatar beginning Saturday.



    Source: The Times of India
     
    Last edited: May 5, 2011
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  3. Sam2012

    Sam2012 Tihar Jail Banned

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    IAF should be red faced for the Mig crashes & Pilots looseing life which in Invaluable , if there is a mere snag in lazy Defence minister IAF should not be more concerned eiether ways if he dies in a crash what is the big deal?

    why politicians are given so importance more than of our own soldiers & pilots?
     
  4. Ray

    Ray The Chairman Defence Professionals Moderator

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    That is not true.

    By autorotation technique one can land the helicopter safely.

    Helicopter Autorotations or Engine Off Landings

    How to Land a Helicopter When the Engine Fails

    Many people think that if a helicopter engine stops, then the aircraft simply plunges out of the sky. Indeed, I have seen a description of this happening in a novel by a well known author who should know better! But this is not the case. Instead, the pilot can put the helicopter into a controlled descent and land it safely – a manoeuvre known as ‘autorotation’.

    How Does Autorotation Work?

    It is not the engine which ultimately keeps the helicopter flying. The air over the rotor blades produces lift, and it is this lift which enables the helicopter to stay in the air. Normally it is the engine which turns the blades in order to produce that airflow. So if the engine stops, something else is required.

    If a descent is started after the engine stops, the resulting airflow coming from below will keeps the blades rotating, a little like a windmill or sycamore leaf. The helicopter can still fly and it is now established in what is known as ‘autorotation’. It will descend quite quickly, typically at around 1700 feet per minute. But it will be coming down under control, and the pilot can choose where to go, decide to speed up or slow down, and eventually he or she can turn into wind and select a safe landing site.

    The Aim of Autorotation Practice

    Autorotation is practiced extensively during the PPL(H) course, so that the movements become instinctive. The aim of this lesson is to learn how to enter autorotation, control the helicopter in the descent, and recover to the climb. The exercise is usually done well away from the airfield initially to learn the manoeuvres, and later above the airfield when the student is going to actually practice the landing. The helicopter is turned into wind, the instructor makes a pre-arranged call (normally “practice autorotation, go”) as he closes the throttle, and the collective is lowered as far as possible. It will also be necessary for the student to apply back pressure on the collective to prevent the nose dropping, and right pedal to keep the helicopter straight. An appropriate speed – usually around 65 knots – can be selected. The helicopter is now established in autorotation.

    The Landing

    The student will learn how to make turns and speed up or slow down while descending, meanwhile looking for a good place to land. A flat field is ideal, but any flat area will do in an emergency, even a flat roof if engine failure occurs over a town. At about 40 feet above the ground, the pilot starts to raise the nose of the helicopter. This slows it down, and the aim is to be level just a few feet above the ground. At this point the collective is raised to cushion the landing. Ideally the landing is gentle, but helicopter skids are designed to cushion a less than perfect autorotative landing.



    Autorotation Hints and Tips

    The student should make a conscious effort to look outside most of the time, not at the instruments. That way he will quite naturally make the correct movements of the controls.

    The student should breathe deeply. Tension causes you to forget to breathe, and this doesn’t help when it comes to autorotation practice…or flying in general.

    Autorotation practice can make beginning students very nervous. But it shouldn’t, for the engine is there if needed, and if anything goes wrong the instructor can open the throttle so that normal flight can commence. Doing one for real is of course a different matter, but it should be remembered that real engine failures are very rare indeed, and many pilots go through their whole flying careers without ever experiencing one. But you do need to be prepared….

    http://www.must-fly.com/helicopter-articles/learning-to-fly-helicopters/139-helicopter-autorotations


     
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  5. Ray

    Ray The Chairman Defence Professionals Moderator

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  6. Ray

    Ray The Chairman Defence Professionals Moderator

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    Aerodynamics of Autorotation

    During powered flight, the rotor drag is overcome with engine power. When the engine fails, or is deliberately disengaged from the rotor system, some other force must be used to sustain rotor RPM so controlled flight can be continued to the ground. This force is generated by adjusting the collective pitch to allow a controlled descent. Airflow during helicopter descent provides the energy to overcome blade drag and turn the rotor. When the helicopter is descending in this manner, it is said to be in a state of autorotation. In effect the pilot gives up altitude at a controlled rate in return for energy to turn the rotor at an RPM which provides aircraft control. Stated another way, the helicopter has potential energy by virtue of its altitude. As altitude decreases, potential energy is converted to kinetic energy and stored in the turning rotor. The pilot uses this kinetic energy to cushion the touchdown when near the ground.

    Most autorotations are performed with forward airspeed. For simplicity, the following aerodynamic explanation is based on a vertical autorotative descent (no forward airspeed) in still air. Under these conditions, the forces that cause the blades to turn are similar for all blades regardless of their position in the plane of rotation. Dissymmetry of lift resulting from helicopter airspeed is therefore not a factor, but will be discussed later.

    During vertical autorotation, the rotor disk is divided into three regions.

    [​IMG]

    The driven region, also called the propeller region, is nearest to the blade tips and normally consists of about 30 percent of the radius. The total aerodynamic force in this region is inclined slightly behind the rotating axis. This results in a drag force which tends to slow the rotation fo the blade.

    The driving region or autorotative region, normally lies between about 25 to 70 percent of the blade radius. Total aerodynamic force in this region is inclined slightly forward of the axis of rotation. This inclination supplies thrust which tends to accelerate the rotation of the blade.

    The stall region includes the inboard 25 percent of the blade radius. It operates above the stall angle of attack and causes drag which tends to slow the rotation of the blade.
    The following figure shows three blade sections that illustrate force vectors in the driven region "A", a region of equilibrium "B" and the driving region "C":

    [​IMG]

    The force vectors are different in each region, because the rotational relative wind is slower near the blade root and increases continually toward the blade tip. When the inflow up through the rotor combines with rotational relative wind, it produces different combinations of aerodynamic force at every point along the blade.

    In the driven region, the total aerodynamic force acts behind the axis of rotation, resulting in an overall dragging force. This area produces lift but it also opposes rotation and continually tends to decelerate the blade. The size of this region varies with blade pitch setting, rate of descent, and rotor RPM. When the pilot takes action to change autorotative RPM, blade pitch, or rate of descent, he is in effect changing the size of the driven region in relation to the other regions.

    Between the driven region and the driving region is a point of equilibrium. At this point on the blade, total aerodynamic force is aligned with the axis of rotation. Lift and drag are produced, but the total effect produces neither acceleration nor deceleration of the rotor RPM. Point "D" is also an area of equilibrium in regard to thrust and drag.

    Area "C" is the driving region of the blade and produces the forces needed to turn the blades during autorotation. Total aerodynamic force in the driving region is inclined forward of the axis of rotation and produces a continual acceleration force. Driving region size varies with blade pitch setting, rate of descent and rotor RPM. The pilot controls the size of this region in relation to the driven and stall regions in order to adjust autorotative RPM. For example, if the collective pitch stick is raised, the pitch angle will increase in all regions. This causes the point of equilibrium "B" to move toward the blade tip, decreasing the size of the driven region. The entire driving region also moves toward the blade tip. The stall region becomes larger and the total blade drag is increased, causing RPM decrease.

    A constant rotor RPM is achieved by adjusting the collective pitch control so blade acceleration forces from the driving region are balanced with the deceleration forces from the driven and stall regions.

    Aerodynamics of autorotation in forward flight

    Autorotative force in forward flight is produced in exactly the same manner as when the helicopter is descending vertically in still air. However, because forward speed changes the inflow of air up through the rotor disk, the driving region and stall region move toward the retreating side of the disk where angle of attack is larger:

    [​IMG]

    Because of lower angles of attack on the advancing side blade, more of that blade falls into the driven region. On the retreating side blade, more of the blade is in the stall region, and a small section near the root experiences a reversed flow. The size of the driven region on the retreating side is reduced.

    Autorotations may be divided into three distinct phases; the entry, the steady state descent, and the deceleration and touchdown. Each of these phases is aerodynamically different than the others. The following discussion describes forces pertinent to each phase.

    Entry into autorotation is performed following loss of engine power. Immediate indications of power loss are rotor RPM decay and an out-of-trim condition. Rate of RPM decay is most rapid when the helicopter is at high collective pitch settings. In most helicopters it takes only seconds for the RPM decay to reach a minimum safe range. Pilots must react quickly and initiate a reduction in collective pitch that will prevent excessive RPM decay. A cyclic flare will help prevent excessive decay if the failure occurs at thigh speed. This technique varies with the model helicopter. Pilots should consult and follow the appropriate aircraft Operator's Manual.

    The following figure shows the airflow and force vectors for a blade in powered flight at high speed:

    [​IMG]

    Note that the lift and drag vectors are large and the total aerodynamic force is inclined well to the rear of the axis of rotation. If the engine stops when the helicopter is in this condition, rotor RPM decay is rapid. To prevent RPM decay, the pilot must promptly lower the collective pitch control to reduce drag and incline the total aerodynamic force vector forward so it is near the axis of rotation.

    The following figure shows the airflow and force vectors for a helicopter just after power loss:

    [​IMG]

    The collective pitch has been reduced, but the helicopter has not started to descend. Note that lift and drag are reduced and the total aerodynamic force vector is inclined further forward than it was in powered flight. As the helicopter begins to descend, the airflow changes. This causes the total aerodynamic force to incline further forward. It will reach an equilibrium that maintains a safe operating RPM. The pilot establishes a glide at the proper airspeed which is 50 to 75 knots, depending on the helicopter and its gross weight. Rotor RPM should be stabilized at autorotative RPM which is normally a few turns higher than normal operating RPM.

    The following figure shows the helicopter in a steady state descent:

    [​IMG]

    Airflow is now upward through the rotor disk due the descent. Changed airflow creates a larger angle of attack although blade pitch angle is the same as it was in the previous picture, before the descent began. Total aerodynamic force is increased and inclined forward so equilibrium is established. Rate of descent and RPM are stabilized, and the helicopter is descending at a constant angle. Angle of descent is normally 17 degrees to 20 degrees, depending on airspeed, density altitude, wind, the particular helicopter design, and other variables.

    The following figure illustrates the aerodynamics of autorotative deceleration:

    [​IMG]

    To successfully perform an autorotative landing, the pilot must reduce airspeed and rate of descent just before touchdown. Both of these actions can be partially accomplished by moving the cyclic control to the rear and changing the attitude of the rotor disk with relation to the relative wind. The attitude change inclines the total force of the rotor disk to the rear and slows forward speed. It also increases angle of attack on all blades by changing the inflow of air. As a result, total rotor lifting force is increased and rate of descent is reduced. RPM also increases when the total aerodynamic force vector is lengthened, thereby increasing blade kinetic energy available to cushion the touchdown. After forward speed is reduced to a safe landing speed, the helicopter is placed in a landing attitude as collective pitch is applied to cushion the touchdown.

    Helicopter Aviation
     
  7. arya

    arya Senior Member Senior Member

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    haa haa great news now he know condition of iaf well i wish i feel the pain of fighter pilots in same way ,when he plane or copter in sky . we care only our blood
     
  8. Yusuf

    Yusuf GUARDIAN Administrator

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    And they don't order critical choppers required to sustain troops in Siachen and other areas.
     
  9. Ray

    Ray The Chairman Defence Professionals Moderator

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    St Anthony aka AK Anthony is not afraid of travel by air or car or train.

    He carries the medallion of St Christopher, the patron saint of travellers, to protect him till he meets his Maker in the natural way!
     

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