by Richard Sheffield
Unlike most aircraft, the chassis and skin of the Apache do more than just serve as a supporting structure and enclosure. This machine was designed to operate in the middle of a battlefield, and as such, taking hits is unavoidable. The basic structure of the AH-64A allows it to get hit and still continue to operate.
The crew area, the drive systems, and the hydraulics are covered with high-impact armor and fragmentation shields. This armor is designed to stop the 23mm High Explosive Incendiary cannon projectile fired from the feared Soviet ZSU-23-4 Shilka mobile antiaircraft gun. The rest of the aircraft is, for the most part, invulnerable to fire from .5-inch gun armor-piercing shells.
The parts of the aircraft which are not armor covered are either redundant or deliberately made oversized in order to continue to function when damaged. The main drive shaft could be three inches in size and still perform well, but by increasing the size to seven inches, it's capable of taking a direct hit and continuing to function.
Figure 2-1. An AH-64 Apache Fully Loaded with Hellfire Missiles
Figure 2-2. Impact-Resistant Armor
The crew and vital components are protected by armor composed of bonded boron carbide and Kevlar. When a projectile, such as that fired by the ZSU-23-4, hits the armor, the projectile and the boron carbide both fracture, absorbing much of the energy. The Kevlar backing then gives and expands to absorb the remaining energy and prevents the shrapnel from entering the aircraft.
An example of redundancy is the dual-engine design. Either engine can support the aircraft by itself in all flight modes, including hovering. The engines are also placed as far apart as possible to prevent both from being damaged by a single shot or by an engine explosion.
As mentioned, the crew members are protected by armor and bulletproof wind screens. They are also protected by a transparent blast screen which is located between them. This screen prevents both of them from being harmed by an explosion in the cockpit. Each crew member is flight qualified; flight controls are located in both compartments.
The aircraft is protected as much as possible because everyone understands that crashes in battle are inevitable. The Apache is built to take it. The whole structure is built to be load absorbing, and the landing gear are designed to collapse if necessary to protect the main body of the aircraft. Crash tracks run the length of the crew area to give support to the nose in the event of a crash. These tracks also contain the chain gun and keep it from damaging the fuel cells (which are also crash and damage resistant).