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Watching Jet Stream, about training to fly the CF-18 Hornet, they comment that the jet was originally certified as a Navy plane, landing on aircraft carriers with an arresting cable.
Usually, when landing on land, they land hard and fast and take a mile of runway to come to a stop; but during an emergency, they use the tailhook which brings the jet to a stop after only 1,000ft.
My question is: why don't they always use this to land?
Here's a short clip I've taken from the show:
There is a lot of stress placed on the airframe when you use the tailhoook. You can see the skin buckling in the picture below behind the landing gear. I'll admit, you probably wouldn't land intentionally with this sort of technique on land but if you catch the wire during the flare it could probably pull you down pretty hard. For these types of landing and it would be difficult to get it right every time.
(Like I wrote in the comments, I do realize that the aircraft below has not yet caught the cable. When you flare, and you might catch the cable mid-air if you have a nose-high attitude, and slam down hard as it pulls you backwards and you loose lift, or you do a non-flare like carrier pilots, also very hard. IMO I think either would end up like the landing below.)
You have no ability to control the aircraft and you end up stopping and rolling backwards on the runway. You can only be one aircraft at a time and you cannot roll off straight away, wasting time.
You'd have to have an arresting gear system and along with that more staff and maintenance.
At least on aircraft carriers, I believe the arresting cable has a limit of only 250 catches for safety reasons. Even if it the limit was greater on land, you'd have to have people changing the cables on a regular basis.
You'd still have to have conventional brakes which you could just as well use.
There are several reasons why arresting cables aren't used on land:
As Manfred noted, the stress that gets put onto a plane during landing is incredible. According to HowStuffWorks "How Aircraft Carriers Work", its not unusual for an aircraft to hit the deck at around 150 mph or about 67 mps. Since they have less than 500 feet of runway (~150 meters), they must decelerate at an incredible speed to a standstill in about 2 seconds. That equates to about 3.5 G's! In addition, Navy pilot's are taught to push the throttle to max upon hitting the deck so that if they miss one of the 4 cables, they can still have enough speed to take off and try again. This may now happen automatically as Chris S noted, I'm not certain. This means that the aircraft has to undergo even more stress. Navy planes must hit the deck so hard that its often compared to a controlled crash instead of landing and aircraft frames must be structurally modified to endure that type of stress.
According to Tom Clancy's Carrier: A Guided Tour of an Aircraft Carrier, it is extremely difficult to catch the wires. It is so difficult that Navy Pilots are often ranked on how often they hit the 2nd wire (considered to be the best).
As Manfred noted above, the machinery to slow an aircraft is not trivial. While I'm not familiar of the routine replacement rate for these cables, I would imagine that it would be something else that would have to be monitored. The cable is actually attached to a large machine which provides the cable with some give. I can't imagine that they would be cheap, but I'm not familiar with the exact machinery myself.
Fatigue basically.
A carrier landing is often referred to as a (hopefully) controlled crash. Navy aircraft are built much stronger than land-based aircraft for that reason. If you can avoid subjecting your aircraft to those sort of conditions, then why wouldn't you?
Some military runways (on land) do have arresting cables. These are not intended for routine use, but to catch aircraft in danger of running off the end of the runway due to brake failure, touching down too late, etc. Sometimes they may pop-up to snare the undercarriage rather than using a hook, Navy style.
The reasons for not using arresting cables on land have been well discussed above -- airframe and pilot stress from the high G's, maintenance costs, etc. Also, there's usually plenty of land on which to build a runway, so you don't need to stop short as on a carrier.
An additional answer not discussed yet is the effect it would have on the runway.
If you've ever seen the deck of the carrier in the impact zone, you know that it is hammered all to hell from the repeated beating by the tail-hooks coming in much steeper than a runway approach (insert controlled crash reference here). For the ship it is less of an issue, because the deck will get regular maintenance and the ship doesn't always need to be ready to fly (carriers actually spend a lot of time getting repairs compared to a runway).
If you were to start hammering away at the concrete on a runway all the time like that steel deck, it's going to tear it up pretty quick, and then you have to deal with not just the dings in the runway, but the pieces that came out of those holes AND with doing patch work on those holes.
I served USAF as a tactical aircraft (fighter jet) maintenance technician (aka Crew Chief). F-15's are a land-based aircraft, and have an arresting hook, and the runways have arresting cables. However unlike a carrier, there is only a single arresting cable, and it is for emergency use only.
In the event that a fighter jet is experiencing a hydraulic failure that may mean loss of brakes, the arresting hook will be deployed, and the pilot will land short to ensure that it will catch the cable. The cable is SLIGHTLY elevated above the runway, so the hook can properly catch it, but not so much that the wheels won't easily roll right over it.
The arresting hooks on these aircraft are not designed for frequent use. While they are attached more or less directly to the keel of the aircraft to minimize strain on the airframe, the arresting hook has a large solid aluminum pad that must be replaced every time it is used.
The cable on the runway is a drag system, NOT an active system. As I recall from my training it uses inertia reels to aid in slowing down the airplane, but there is enough cable length to allow the airplane to go a decent distance down the runway still. Compare to a aircraft carrier, which has an active restraint system and the cables stop the aircraft almost immediately.
I believe that Navy fields used to train pilots for carrier landings, actually have the full sequence of cables that a carrier has, not just a single cable for emergency use.
There is a famous incident involving an Israeli F-15 that lost a wing during a combat training accident, and was subsequently flown back using afterburner (The pilot didn't know he had lost a wing). Upon landing, he was still going at near-MIL speed and required the arresting cable and arresting hook system to stop the aircraft. Not usually mentioned in the documentaries, the arresting cable system on the runway was severely damaged by the incident.
Many air forces throughout the world in fact do use runway arresting gear during flight operations and a glance through an Airport/Facility Directory will reveal that even many large civilian airports are equipped with runway arresting gear. It is generally reserved for emergency operations, as seen in the JetStream series, where either the aircraft may have a malfunction which prevents conventional means of braking during landing or situations where portions of an active runway may be damaged, denying flight operation down their full length. For normal flight operations on long runways the arrested landing is not used, primarily as it more stressful on the airframes, resulting in more maintenance and higher operating costs.
Quick description of runway arresting gear and their use here.
Here's something really wild as well; Australian F-111 makes a wheels up landing using arresting gear after the landing gear failed to deploy.
