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There are 4 arresting wires on an aircraft carrier separated by about 50 feet and usually the pilot tries to snag the 3rd one but he does have the option to snag the first or second one.

What stops the tailhook from engaging the wires in front of the airfraft as well? Is it assumed that they will also get engaged and the regulator on each arresting engine is tuned to accept it?

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    $\begingroup$ I don't have any military aviation experience, but it looks like once the tail hook snags a cable, it's pulled back and upwards, which would prevent it from snagging a second wire. $\endgroup$
    – Johnny
    Mar 25, 2015 at 15:24
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    $\begingroup$ I completely agree with @Johnny. This picture shows pretty well how it works $\endgroup$
    – Maverick283
    Mar 25, 2015 at 15:37
  • $\begingroup$ As a side note - carrier aviators never aim for the first two wires (on a 4-wire ship). The aim is almost always to tag the 3-wire. Tagging the 1-wire is considered dangerous. $\endgroup$
    – Tyler
    Mar 25, 2015 at 22:40
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    $\begingroup$ what is the purpose of the first wire then? $\endgroup$
    – user99379
    Mar 26, 2015 at 16:15
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    $\begingroup$ @user99379 The deck moves. while the 3 wire is the preferred trap, a trap beats a bolter. So if the plane comes in a bit short, catching the 1 wires still makes for a recovery. The pilot can work on better approach/technique on the next try. $\endgroup$
    – KorvinStarmast
    Oct 11, 2017 at 18:28

2 Answers 2

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The answer is quite simple:

1. When touching down the nose is in a pulled up attitude, therefore the tail is farther down then normal. As soon as the airplane touches down (on all wheels), the tail is higher, thus the hook is higher. You can see how the aircraft is in a nose up attitude, but gear and hook are on the same level. You can see how the aircraft is in a nose up attitude, but gear and hook are on the same level. If the aircraft was sitting on all its tires, the hook would actually touch the ground. (This might not even be the case on all aircraft, though!)

2. This is the much more important reason: The hook is pneumatically pushed onto the deck (Google for the "F-14 Tomcat Pilot's Flight Operating Manual Vol. 1, Volume 1". Interestingly Wikipedia (is it a source?) says there are hydraulic and pneumatic hooks) but as soon as the hook hooks to the cable, and pulls on it, that pneumatic pressure is overcome and the vectors of the forces go from where the hook is attached to the plane to where the wire comes out of the ground (and vice versa).

Note: I guess its a combination of both, hydraulic and pneumatic. As hydraulics are not compressible, a valve would be needed to release the pressure built by the yank of the cable. So air pressure (pneumatics) would probably do a better job on keeping the hook down as long as no cable is attached. The retraction of the hook is done hydraulically though, and the way it is written in the F-14 Tomcat Pilot's Flight Operating Manual Vol. 1, Volume 1 it seems like the pneumatic pressure is kept even with the hook retracted... Side view

As you can see here, the hook is actually almost parallel to the deck.

3. Last but not least: There is no space for two wires on one hook. Let's say the airplane would catch the first rope, and for some reason (it should definitely not happen, but let's just pretend it does) the hook is still on the ground where it would hook up to the second wire when crossing it, then it will maybe drag it along for a short time, but it can't really hook on as the hook is made to fit exactly one wire. This can be seen on this picture:enter image description here

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    $\begingroup$ On touchdown the nose is never pulled up, it is held at a constant AoA for the entire approach. The height of the tailhook is actually longer than the gear when sitting on all tires (the nose up attitude actually lowers the hook height even further), and it cannot be fully extended unless the aircraft is airborne. Sitting on the tires, the hook is blocked by the deck, and a little warning light illuminates in the cockpit telling the pilot that the hook is not fully extended. Also, as soon as the hook catches a wire it is yanked parallel (every time) preventing #3 from being an issue. $\endgroup$
    – Rhino Driver
    Mar 25, 2015 at 20:14
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    $\begingroup$ Okay, thanks for that input will edit accordingly $\endgroup$
    – Maverick283
    Mar 25, 2015 at 20:33
  • $\begingroup$ Thanks so much for the answer. I don't think I realized that the wires were so close to the deck to begin with. I imagined them somehow off the ground so that the hook could grab them. I see that makes no sense now since the aircraft itself would run into it. $\endgroup$
    – user99379
    Mar 26, 2015 at 16:08
  • $\begingroup$ great pictures! $\endgroup$
    – Erich
    Mar 27, 2015 at 1:21
  • $\begingroup$ The last picture is broken. $\endgroup$
    – jklingler
    Nov 9, 2015 at 12:28
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No, the hook is not capable of catching more than a single wire at a time. There is a hydraulic dampener in the hook, the snubber, that keeps the hook pressed into the deck during touchdown. This was designed to help alleviate a phenomenon known as hook skip bolters, when the force of the hook contacting the deck causes the hook to bounce; however, the hydraulic force of the snubber pressure is immediately overcome when the hook catches a wire, and the hook is drawn up almost parallel to the flight deck as the cable arrests the aircraft.

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    $\begingroup$ I've been out of the business for a few years now, but I recall that the snubber was pneumatic vs hydraulic. Because air can compress, while hydraulic fluid does not... $\endgroup$
    – Michael Hall
    Jul 12, 2018 at 0:03

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