The flight operating strength of an airplane is presented on a graph whose horizontal scale is based on load factor. The diagram is called a Vg diagram—velocity versus "g" loads or load factor.

Each airplane has its own Vg diagram that is valid at a certain weight and altitude. The lines of maximum lift capability (curved lines) are the first items of importance on the Vg diagram. The subject airplane in the illustration is capable of developing no more than one positive "g" at 62 m.p.h., the wing level stall speed of the airplane.

Since the maximum load factor varies with the square of the airspeed, the maximum positive lift capability of this airplane is 2 "g" at 92 m.p.h., 3 "g" at 112 m.p.h., 4.4 "g" at 137 m.p.h., and so forth. Any load factor above this line is unavailable aerodynamically; i.e., the subject airplane cannot fly above the line of maximum lift capability (it will stall). Essentially the same situation exists for negative lift flight with the exception that the speed necessary to produce a given negative load factor is higher than that to produce the same positive load factor.

If the subject airplane is flown at a positive load factor greater than the positive limit load factor of 4.4, structural damage will be possible. When the airplane is operated in this region, objectionable permanent deformation of the primary structure may take place and a high rate of fatigue damage is incurred. Operation above the limit load factor must be avoided in normal operation.

There are two other points of importance on the Vg diagram. First, is the intersection of the positive limit load factor and the line of maximum positive lift capability. The airspeed at this point is the minimum airspeed at which the limit load can be developed aerodynamically. Any airspeed greater than this provides a positive lift capability sufficient to damage the airplane; any airspeed less does not provide positive lift capability sufficient to cause damage from excessive flight loads. The usual term given to this speed is "maneuvering speed," since consideration of subsonic aerodynamics would predict minimum usable turn radius to occur at this condition. The maneuver speed is a valuable reference point, since an airplane operating below this point cannot produce a damaging positive flight load. Any combination of maneuver and gust cannot create damage due to excess airload when the airplane is below the maneuver speed.

Next, is the intersection of the negative limit load factor and line of maximum negative lift capability; any airspeed greater than this provides a negative lift capability sufficient to damage the airplane; any airspeed less does not provide negative lift capability sufficient to damage the airplane from excessive flight loads.

The limit airspeed (or redline speed) is a design reference point for the airplane—the subject airplane is limited to 225 m.p.h. If flight is attempted beyond the limit airspeed, structural damage or structural failure may result from a variety of phenomena. Thus, the airplane in flight is limited to a regime of airspeeds and g's which do not exceed the limit (or redline) speed, do not exceed the limit load factor, and cannot exceed the maximum lift capability. The airplane must be operated within this "envelope" to prevent structural damage and ensure that the anticipated service lift of the airplane is obtained. The pilot must appreciate the Vg diagram as describing the allowable combination of airspeeds and load factors for safe operation. Any maneuver, gust, or gust plus maneuver outside the structural envelope can cause structural damage and effectively shorten the service life of the airplane.

All certificate airplanes are designed to withstand loads imposed by gusts of considerable intensity. Gust load factors increase with increasing airspeed and the strength used for design purposes usually corresponds to the highest-level flight speed. In extremely rough air, as in thunderstorms or frontal conditions, it is wise to reduce the speed to the design maneuvering speed. Regardless of the speed held, there may be gusts that can produce loads that exceed the load limits.
Most airplane flight manuals now include turbulent air penetration information. Operators of modern airplanes, capable of a wide range of speeds and altitudes, are benefited by this added feature both in comfort and safety. In this connection, it is to be noted that the maximum "never-exceed" placard dive speeds are determined for smooth air only. High-speed dives or acrobatics involving speed above the known maneuvering speed should never be practiced in rough or turbulent air.

In summary, it must be remembered that load factors induced by intentional acrobatics, abrupt pull-ups from dives, high-speed stalls, and gusts at high airspeeds all place added stress on the entire structure of an airplane. Stress on the structure involves forces on any part of the airplane. There is a tendency for the uninformed to think of load factors only in terms of their effect on spars and struts. Most structural failures due to excess load factors involve rib structure within the leading and trailing edges of wings and tail group. The critical area of fabric-covered airplanes is the covering about one-third of the chord aft on the top surface of the wing.

The cumulative effect of such loads over a long period of time may tend to loosen and weaken vital parts so that actual failure may occur later when the airplane is being operated in a normal manner.

It would be difficult to make a definite statement concerning load factors in these maneuvers as both involve smooth, shallow dives and pull-ups. The load factors incurred depend directly on the speed of the dives and the abruptness of the pull-ups. Generally, the better the maneuver is performed, the less extreme will be the load factor induced. A chandelle or lazy eight, in which the pull-up produces a load factor greater than 2 G's will not result in as great a gain in altitude, and in low-powered airplanes it may result in a net loss of altitude.

The smoothest pull-up possible, with a moderate load factor, will deliver the greatest gain in altitude in a chandelle and will result in a better overall performance in both chandelles and lazy eight's.

Further, it will be noted that recommended entry speed for these maneuvers be generally near the manufacturer's design maneuvering speed, thereby allowing maximum development of load factors without exceeding the load limits.

The average light plane is not built to withstand the repeated application of load factors common to high-speed stalls. The load factor necessary for these maneuvers produces a stress on the wings and tail structure, which does not leave a reasonable margin of safety in most light airplanes.

The only way this stall can be induced at airspeed above normal stalling involves the imposition of an added load factor, which may be accomplished by a severe pull on the elevator control. A speed of 1.7 times stalling speed (about 102 knots in a light airplane with a stalling speed of 60 knots) will produce a load factor of 3 G's. Further, only a very narrow margin for error can be allowed for acrobatics in light airplanes. To illustrate how rapidly the load factor increases with airspeed, a high-speed stall at 112 knots in the same airplane would produce a load factor of 4 G's.

Since a stabilized spin is not essentially different from a stall in any element other than rotation, the same load factor considerations apply as those that apply to stall recovery. Since spin recoveries usually are effected with the nose much lower than is common in stall recoveries, higher airspeeds and consequently higher load factors are to be expected. The load factor in a proper spin recovery will usually be found to be about 2.5 G's.
The load factor during a spin will vary with the spin characteristics of each airplane but is usually found to be slightly above the 1 G of level flight. There are two reasons this is true:

1. The airspeed in a spin is very low, usually within 2 knots of the unaccelerated stalling speeds; and
2. The airplane pivots, rather than turns, while it is in a spin.

The normal stall entered from straight level flight, or an unaccelerated straight climb, will not produce added load factors beyond the 1-G of straight-and-level flight. As the stall occurs, however, this load factor may be reduced toward zero, the factor at which nothing seems to have weight; and the pilot has the feeling of "floating free in space." In the event snapping the elevator control forward effects recovery, negative load factors, those that impose a down load on the wings and raise the pilot from the seat may be produced. During the pull-up following stall recovery, significant load factors sometimes are induced. Inadvertently these may be further increased during excessive diving (and consequently high airspeed) and abrupt pull-ups to level flight. One usually leads to the other, thus increasing the load factor. Abrupt pull-ups at high diving speeds may impose critical loads on airplane structures and may produce recurrent or secondary stalls by increasing the angle of attack to that of stalling.

As a generalization, a recovery from a stall made by diving only to cruising or design maneuvering airspeed, with a gradual pull-up as soon as the airspeed is safely above stalling, can be effected with a load factor not to exceed 2 or 2.5 G's. A higher load factor should never be necessary unless recovery has been effected with the airplane's nose near or beyond the vertical attitude, or at extremely low altitudes to avoid diving into the ground.

50 Years of Malaysian Airport

It was a circular concrete landing ground 1,000 yards in diameter. It was bound by an open perimeter ditch and drained by a system of sub-soil drains. On the outside of the perimeter ditch, an annular space 200 yards wide provided extra clearance for aircraft rising from the landing ground.

This described Malaysia's first civilian airport in Bayan Lepas, Penang. It was built in 1932 at a cost of RM135,741. Three years later, it had full night landing facilities and a permanent hangar 100 feet square by 25 feet high was being built.

Penang replaced Alor Star as the transit stop for KLM and Imperial Airways that made it a port of call, where it served as the terminal port for the Penang-Hong Kong service. At the outbreak of the Second World War, Malaysia had 10 airstrips namely, Port Klang, Ipoh, Sitiawan, Taiping, Simpang Ampat, Batu Pahat, Kluang, Kota Baru, Kuching, and Bintilu.

In fact, Bintulu airport was listed in the Guiness Book of Records as the only airport in the world that is in the heart of the city. In 1933, Malaysia's first international aerodrome, the Sungai Besi Airfield, receiced its first international commercial aircraft.

The rapid growth in air transportation saw the airport expanded at a cost of RM590,000. The attap shed terminal was replaced with a new terminal as well as four hangars and a 6,200-feet tall weather runway.

In 1956, the airport was declared an international airport, marked by the flight of a turbo-propeller Bristol Britannia aircraft to Europe. By 1957, the country had two international airports and six domestic airports that recorded a total of 130,000 passengers.

Within two years of independence, the federal authorities came up with a blueprint for a brand new international airport for Kuala Lumpur to be located in Subang. Six years later in 1965, the RM52 million Subang International Airport was opened with facilities, amenities and accoutrements befitting a modern international airport.

Subang served as the main gateway to the country for the next 30 years, recording exponential passenger and cargo growth. It underwent several renovations and facility upgrade to meet the growing needs including the introduction of a primary radar for air traffic control, upgrading of the main terminal and expansion of the hangar.

At the same time, airport development projects were also carried out in other parts of the country such as Penang, Kota Bharu, Kuala Terengganu, Kota Kinabalu, Pulau Langkawi, Ipoh, Miri and Sibu.

The surge of airport development projects provided Malaysians the opportunity to acquire and upgrade their airport design and construction expertise. As a result, Malaysia developed a corps of specialists who could manage, plan, design and build airports of various sizes and scale. This reservoir of local specialists formed the bedrock of the KL International Airport (KLIA) development project. KLIA represented a giant leap in Malaysian civil aviation history.

It was the solution to the congestion experience in Subang Airport.In 1991, the government privatised the development of KLIA by forming Kuala Lumpur International Airport Berhad to undertake the project management of the new airport. In the same year, Parliament passed a bill that split the functions of the Department of Civil Aviation (DCA).

While DCA continue its role as the regulatory authority, a private company, Malaysia Airports Berhad took over the responsibility of operating, managing and maintaining the country's five international, 14 domestic and 15 Short Take-Off and Landing Ports (STOL Ports).

KLIA opened in 1998 as the result of a visionary strategy to meet the needs of new large aircraft and the traffic demand of the 21st century.

The award-winning airport is able to handle 25 million passengers per annum, and ultimately 100 million by the end of the next century.

A year later, Malaysia Airports became the first airport operating company to be listedbin Asia and the sixth in the world. The company was listed on the main board of Bursa Malaysia.

The core activities of the company include the management, operation and maintenance as well as development of airports with primary importance being placed on the operational efficiency, safety and security of passengers, cargo and aircraft operations.

Besides its core business activities, Malaysian Airports has in its corporate structure, a few subsidiary companies to offer a range of aviation and non-aviation-related products and services.

Malaysia Airports' present corporate structure includes 10 operating subsidiaries; Malaysia Airports Sdn. Bhd., Malaysia Airports (Sepang) Sdn. Bhd., Malaysia Airports (Niaga) Sdn. Bhd., Malaysia Airports Management & Technical Services Sdn., Sepang International Circuit Sdn. Bhd., Malaysia Airports Technologies Sdn. Bhd., Malaysia Airports (Properties) Sdn. Bhd., K.L Airport Hotel Sdn. Bhd., MAB Agriculture-Horticulture Sdn. Bhd. and Asia Pacific Auction Centre Sdn. Bhd. Its associated company is Urusan Teknologi Wawasan Sdn. Bhd. The Group has a total staff strength of over 7,000 deployed across 39 offices nationwide.

It is currently providing training for 238 personnel assigned to the new Hyderabad international Airport in India.

It is also part of a consortium that was awarded a contract for the restructuring and modernisation of the New Delhi Airport.

In April this year, it was awarded a 10-year contract to manage, operate and maintain the Astana International Airport in Kazakhstan under a trust management. Three months later, Malaysia Airports added another airport in its portfolio when it won the bid to manage Sabiha Gokcen International Airport, the second airport for Turkey.

The airport transportation industry is dynamic and airports are in a continuous state of flux with upgrading, expansion and maintenance works. Airports in Malaysia are no different. KLIA is nearing full capacity and a new satellite building is to be constructed soon.

A new dedicated low-cost carrier terminal was built at the KLIA, which now accommodates low-cost carriers operating to Malaysia.

The introduction of the Airbus A380 and Boeing 787 is expected to herald more changes in the design and operation of airports. The challenge to Malaysia Airports is to manage the expectations of the industry, stakeholders and the nation.

Source: Fauziah Ismail, A New Straits Times Special, August 31, 2007
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