Simple Release: Fill & Download for Free

The selling point of a portcullis is that it is a solid frame that is lowered. You can’t force it like you could force a gate that opens inward either by breaking the beams holding it closed or forcing the hinges. The solid frame is held at the sides by a groove in which it slides up and down. It doesn’t open inward so the only way to bypass it is to raise it upward or completely break it apart.The vertical lowering also means it can be shut by a simple release of the weights and pulleys keeping it up. Occasionally these portcullises were used when the garrison sortied out as they could be closed quickly to hinder pursuit. Other times a pair of them could be used to trap people in the gate house.The fact that the frame is grated means projectiles and weapons can be used through it. Bolt throwers such as spingalds and crossbows could be placed behind them and used to shoot the enemy as if they were fish in a barrel. Sometimes however the besieger also took pains to have one or multiple bolt throwers directed at the gate to prevent any sortieing

Caution: Never pull towards heaven in a stall. You might end up in hell.Let us get serious now.In a stall, your aim is not to gain sufficient speed, but to reduce your angle of attack. When in a stall condition, the first action is to push the control stick or control column down, and get that pitch attitude at least on the horizon of the attitude indicator or possibly lower. Then it is more of a waiting game. Depending on the situation an airliner at a high altitude may require 5000 to 9000 ft of altitude loss to fully recover. When recovering, it is essential to keep the nose lowered until you are out of the stall. It is very easy to enter a secondary stall at high altitudes.What makes things a little complex at high altitudes is the fact that the air is less dense. When it is less dense, there is very little aerodynamic damping and hence it is advisable to be smooth with the controls. Because of the lowered air density, the maximum thrust available also reduces. So, the engines would not be able to give out their maximum performance. The reason for the high altitude loss during the recovery is also because of the reduced air density. In a large airliner, altitude is required for stall recovery. If you happen to stall the aircraft at a low altitude say at like 1500 ft or so, the chances of a fair recovery is very slim.There are certain differences when it comes to stall recovery of a large jetliner when compared to a single engine aircraft or a turboprop. In our first stall lessons during flight training, we are taught to release back pressure on the controls and add full power to recover from the stall. The same applies for turboprops. When power is added in a propeller aircraft the prop wash itself accelerates air over the wings and helps in the recovery.In a jet aircraft the engine thrust does not directly affect the lift vector and as the engines are below the wings, when full power is commanded, the pitch up moment it creates, can hamper the nose down pitch applied by the pilot. So, in some certain circumstances it might even be necessary to reduce or even idle the thrust for the stall recovery. Keep in mind, it is not speed we are trying to gain. Our mission is to get the aircraft to pitch down and bring back the air flow over the wings and get them flying. Once out of the stall, the thrust can be slowly increased and the flight path stabilised. The other thing to keep in mind is, if you happen to enter a stall while in a bank, the first move should not be to get wings level, but to pitch down. Once sufficient pitch down stick forces is applied then only you try to get the wings level.The other difference is, high speed aircraft are fitted with swept wings. These wings while good for high Mach number operations have very unfavourable stall characteristics. Swept wings has a tendency to stall at the tips which moves the lift centre of pressure forwards. This creates a nose up pitch moment and the aircraft might stall and fall to the ground at a very high angle of attack. So, a simple release of back pressure like in a small aircraft would not reduce angle of attack in these airplanes. It is of paramount importance to apply physical nose down pitch by the pilot in the stall recovery.

Typically, energy -is- light, but it can take other forms as well, e.g. kinetic energy or potential energy.But, normally, it is changes in energy, or the simple release of energy that emits light.