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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:

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I have no idea but I imagine it reduces the wear and tear on the airframe long-term. –  Steve V. Apr 21 at 2:06
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Another issue is an arresting system isn't maintenance free- it will require repair, inspection, personnel, supporting machinery, etc. It's cheaper to just use the runway and brakes –  CoderTao Apr 21 at 7:22
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3 Answers 3

  • 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.) stress

  • 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.
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The stress ripples in that picture have nothing to do with the tailhook. Have a close look at the cable - it's just been picked up by the hook and hasn't moved 50cm yet. It won't take any significant landing stress until the plane has pulled several meters of cable out of the blocks. More likely it's the weight of the empennage + radome on top bending the fuselage against the main gear via the wing. Same thing would happen if you slam the plane down on land. (Note: not disagreeing that carrier landings are very hard on the aircraft.) –  paul Apr 21 at 10:20
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Well, the arresting cable has a strict limit because a broken cable means a lost aircraft. If the cable breaks the aircraft already decelerated below flying speed and now has nothing to stop it, so it will fall overboard and splash down. Pilot(s) will eject (anything that ever lands on carrier has ejection seats, including the pictured E-2), aircraft will be lost. –  Jan Hudec Apr 21 at 10:28
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Modern carriers have 3 or 4 cables that can catch a plane; pilots normally aim for the last available cable. The US Navy only uses the arresting cables for 125 landings. The purchase cables (in the picture, near the block, you can see where the attesting cable quick-connects to the purchase cable) are used considerably longer (attesting cables are hemp-cored for a "softer" landing; purchase cables are straight steel). Most planes automatically go to 100% throttle upon hooking a cable to more easily recover from a mis-hook or other problem. –  Chris S Apr 21 at 13:34
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@Chris S: Some misinformation here. Pilots always aim for the middle of the cables which, if done accurately, means that they catch the 3-wire in a four wire system. Also, the planes go to 100% power on hitting the deck, they do not wait to detect a wire catch prior to throttling up. This is a routine procedure, but it is not automatic - the pilot does it. –  Skip Miller Apr 21 at 15:10
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@shortstheory very difficult and heavy for a situation that virtually never exists (complete brake failure). IMO it's better to use EMAS and/or a net at the end to catch the plane should the need arise. –  MikeFoxtrot Apr 21 at 15:54
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There are several reasons why arresting cables aren't used on land:

Stress

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 mps 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.

Difficulty

According to Tom Clancy's, Carrier: A Guided tour of an Aircraft Carrier, it is extremely difficult to catch the wires. Its so difficult that Navy Pilots are often ranked on how often they hit the 2nd wire (considered to be the best).

Price

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.

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Regarding price, I'm not certain on the cost of the cross-deck pendants (the "wire" the hook grabs) but as I recall they are life-limited at somewhere around 100 traps. The arresting mechanism (usually hydraulic) also requires maintenance (and in the case of land-based systems, needs to be set up as either a permanent or temporary installation on the runway being used). –  voretaq7 Apr 21 at 16:48
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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.

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The military runway I mentioned in the question, as well as the video do have arresting cables for emergency use - hence the question. –  Danny Beckett Apr 22 at 4:47
    
@DannyBeckett This is purely speculation, but the runway you showed might be a training runway that the Navy would use for practice. Do you know where this runway is or what is it used for? –  HardcoreBro Apr 22 at 18:38
    
@HardcoreBro It's Cold Lake in Canada. They do use it for training, but they don't normally use the arresting hook. It was used in that video due to an engine failure. –  Danny Beckett Apr 22 at 21:10
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