A/C SYS 2017

It will expand (when heated) or shrink (when cooled).

- Expandation will create a compression load

- Shrinking will create a tension load

At supersonic speed.

Positive loads: 2.9 to 3.8

Negative loads: -1.2 to -1.6

limit loads multiplied by a safety factor of 1.5

The aircraft structure can withstand the ultimate load for at least 3 seconds without failure (permanent deformations are allowed).

a relatively high wing loading and a short wing span
(-> the lighter the aircraft, the higher the load factors due to gusts)

the subject that describes the interaction of aerodynamic, inertia and elastic forces for a flexible structure and the phenomena that can result

• the angle of attack of the wing sections towards the tip will increase more than close to the root
• spanwise redistribution of lift: c.p. will move outward and the bending moment at the wing root will increase.

E = 0.5 * m * v²

During the wing upward motion, at the position of zero bending the twisting of the wing causes a positive geometric incidence and therefore an aerodynamic lift force in the same direction as the wing motion. A similar but reversed situation occurs when the wing is moving downwards.

Flutter Speed

the oscillation will diverge and destroy the wing structure

• a form of flutter associated with shock waves oscillating back and forth on the upper and lower wing surfaces and interacting with the boundary layer
• The sharp changes in pressure distribution cause a high frequency oscillation of the aileron

the most common form of buffeting is that of the tail, which can experience severe vibrations when it is invested by the turbulent wake of the stalled wing

an elastic aircraft in an accelerated flight condition may experience loads which are much greater than those predicted assuming a perfectly rigid structure. External loads, such as gust and landing loads, excite oscillations of the structure. The additional inertia forces associated with these oscillations can produce dynamic load overshoots.

1. Pressure Dome
2. Cabin Floor
3. Frame
4. Stringers
5. Skin

3.05 m/s (10 ft/s) at maximum landing weight (MLW)

the higher its value, the shorter the landing gear compression required to absorb the vertical kinetic energy at landing

• + lower weight (nose gear is much heavier)
• + less drag (if the gear is not retractable)
• + more space available in the aircraft nose (particularly if the gear is retractable)
• + better suited for operation on rough fields
• - laterally unstable when rolling
• - heavy braking may bring the danger of tipping the aircraft over on its nose

• the aircraft does not need to be aligned with the runway (a crab landing is possible)
• it is much easier for the pilot to keep it on the centreline, even with strong side gusts
• offers better visibility for the pilots during taxiing
• easier loading and unloading of the aircraft (and more comfort for the passengers) thanks to the nearly horizontal floor
• low drag during take off acceleration
• is more forgiving when landing with insufficient or no flare (the aircraft tends to reduce the angle of attack after touchdown, and is less prone to bouncing back in the air)

• + lower weight
• + less drag (when gear is extended)
• + used when not enough space for langing gear
• - difficult take-off and landing
• - In crosswind conditions, care must be taken not to land on one of the outrigger gear legs, which are not designed to take substantial landing loads.

23,000 kg (although for safety reasons it would be better to fit twin wheels)

23,000 - 68,000 kg (This configuration is sometimes found also on heavier aircraft with a take-off mass of up to 100,000 kg)

90,000 - 180,000 kg

• spring type
• bungee type
• oleopneumatic shock absorbers (oleo struts)

• gear legs are elastically deformed under load
• typical of small general aviation aircraft
• The vertical kinetic energy is transmitted gradually to the structure
• practically no damping effect, except for the energy dissipated by lateral friction of the tires (when the gear deflects, the wheels move sideways)
• aircraft tends to bounce back in a hard landing

• the main gear legs are hinged at the side of the fuselage and connected by rubber bungees (bundles of rubber
  strands packed in a cloth tube) that stretch as the gear deflects
• common in early light aircraft
• In addition to the lateral friction of the tires, some energy is dissipated by rubber internal friction and hysteresis