Are attack helicopters usually more well-armored than fighters, but less armored than bombers? How so, and why?
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In general, yes. But armoring aircraft in general is usually not what people expect.
Traditionally, fighters are unarmored. Fundamentally speaking, the weapons that a fighter would be engaged by are something that no reasonable amount of armor is going to help with. Missile warheads and cannon shells (the bullets fired by the guns on fighters, typically in the neighborhood of 20mm) aren’t going to be stopped by armor unless that armor is extremely dense and fairly thick. Fighters must be very maneuverable, and maneuverability is bought by losing weight. Since armor would be of minimal usefulness anyway, it’s not an advantage to have it. Every inch of a fighter is packed with something important, which is why fighters seek to *avoid* damage rather than take it. As a result, fighters with redundant systems – backups – are more survivable than those without, but the added weight can cut into their combat performance. It’s a trade.
One noteworthy exception to that is the Fairchild Republic A-10 Thunderbolt II, better known as the Warthog. The A-10 is designed for what’s called “close air support,” which is essentially engaging ground targets like tanks at low altitude and slow speed. So low and slow, in fact, that even rifle fire from below is a threat, to say nothing of traditional antiaircraft guns. To protect the pilot, the cockpit is essentially a titanium “bathtub” that provides the pilot with an exceptional degree of protection from below – at the expense of being heavy. Additional armor protects some key components, adding more weight. But the A-10’s job is *not* to be fast and maneuverable, so given the threats it faces the additional armor weight was considered a good trade.
Helicopters, however, are in their own world. Rotorcraft do not have the lift efficiency of fixed wing aircraft: in order to fly, they have to expend much more energy on a pound-for-pound basis than a conventional plane. This makes weight even more of an enemy for the design. If you want to add arms or armor, you have to increase engine power. If you increase engine power, you have to add more fuel to feed it, and that’s more weight. So the design of any helicopter – but particularly a combat helicopter – is a massive game of trade-offs. Arms, armor, fuel, airframe: how do you spend your weight? Go too heavy and you have to make the helicopter enormous, which makes it a fuel guzzling noise machine that’s not agile at all. If it’s an attack helicopter, you need to devote weight to weapons, otherwise it can’t do its job. You have to spend weight on airframe and engine – that’s the helicopter after all – and you have to spend weight on fuel. Armor loses out unless it’s *specifically* part of the mission profile and *has* to be included.
The Boeing AH-64 Apache is one of the world’s foremost attack helicopters. It has some armor protecting the cockpit and key flight components, but most people would look at what’s there and not call it armor (even though it is). The aircraft is surprisingly tough, but it’s not a flying tank. The Mil Mi-24 “Hind” is a Russian multirole helicopter that is *both* an attack helicopter and a troop transport. It has a belly of heavy armor which, plus its load of troops and weapons, means that it needs a massive powerplant and main rotor to keep it in the air. By combat helicopter standards, it’s enormous, loud, and slow, but that’s what the design called for.
Rather than dealing with damage, helicopters tend to adopt the same strategy as fighters: don’t get hurt in the first place. Modern doctrine with helicopter combat generally emphasizes staying outside of a threat’s ability to engage the helicopter, attacking with long-range weapons. Strafing runs with guns and unguided rockets generally don’t happen in a high-threat environment. Instead, combat helicopters engaging hard targets like tanks will hit and run – a helicopter will remain “masked” behind terrain and pop up to engage threats before going back to cover. Only engagements with infantry and thin-skinned vehicles will be direct-attack, and those *do* carry an element of risk: an infantryman with a shoulder-mounted rocket is a serious threat. Helicopters generally employ active and passive jamming systems to try to reduce the danger, but no reasonable amount of armor is going to protect them from a hit. The armor they carry is designed to stop light caliber rounds, not dedicated anti-aircraft fire and missiles.
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