A brief history of tailhook design

An interesting blog post by Tommy Thomason.

http://thanlont.blogspot.com/2011/12/br ... esign.html

[quote="maus92"]An interesting blog post by Tommy Thomason...quote]

How strong is the tailhook system?

What a good find maus92. Tommy is an excellent source. And yes a carrier aircraft hook is very strong. Aboard HMAS Melbourne the A4G was stopped from a groundspeed of around 105 knots to nothing in less than 200 feet. One's first arrest (rather than any short field arrest in around 1,000 feet or less) is mind boggling. That first arrest and catapult day (for actual Pilot Wings confirmation in the RAN) is momentous if only for the brain scrambling effect during the first arrest. WTF? Then one has to taxi forward to the 100-110 (later) catapult to look down the track at full power wondering WTF? Then the almighty acceleration for less than two seconds (around 6G) for the first time which literally is a punch in the chest with a closed fist that takes your breath away. And then you have to do it all over again or you might be lucky to get 'bingoed' to relax ashore thinking I'll be doing that again soon but at least now I know what NavAv is all about.

The arrest forces are phenomenal - that is why a bad arrest is noticed immediately (if wire breaks for example). Probably the decel before breakage may prevent getting back to flying speed so it is no surprise to see most situations solved by ejection. One Sea Venom Observer was lost during a wire break/arrest aboard HMAS Melbourne when the pilot ejected below the angle deck whilst Observer not seen to eject before aircraft hit the water. The Venom pilot went on to be the first A4G pilot/instructor and then the last TA4G pilot (in rear seat) with a more current pilot in front seat in last flyby at NAS Nowra in mid 1984.

Salute!

Super posts, Spaz.

We flew the Navy hook design in the USAF A-7D, and the best bet was an approach end cable engagement. Once lowering the nose we had a problem.

So I only made two arrests, one at approach end like a carrier landing, the other at the far end of the runway after going too fast on a slick runway. I missed the far end cable and then pulled back hard to get a good "hook set". Engaged the "anchor chain" no sierra emergency cable at the end of the runway and came to a quick stop on the over run. WHEW!

I see a fairly simple design change, and would not worry about the distance between hook point and gear.

I also question the Navy cable design, as the BAK-13 and BAK-14 seemed to bounce up quickly when our Vipers engaged them. We had a fairly short distance from gear to hook, BTW. Our "roll out" cable engagements were really benign.

Gums sends...

It has occurred to me since reading the Tommy H. Thomason post about tailhook design that the screenshot shown below has the F-35C 'getting dirty' (lowering wheels, flaps & hook) at probably the maximun allowed airspeed so the angle of attack will be lower than the more nose high Optimum Angle of Attack (used during a carrier approach). So we see the hook tip 'higher' than usual compared to main wheels due to the flat attitude at the much higher airspeed shown (most likely).

http://attach.high-g.net/attachments/f_ ... ot_246.jpg

Maximum hook design load on early F-16s was 60,000 lb for a 35400 lb max gross weight, so hook load was about 1.7 x GW for a 1000 ft rollout. A Navy 200 ft roll out would require proportionally more hook strength, so hoisting an airplane by the hook is not a strength problem.

Maybe the Navy should experiment with higher wire preload tension to help it snap back up quicker for the F-35C. Cable shredding is a real problem, although it seems it would rarely occur. On one F-16 arrestment test at Edwards AFB in 1979, the hook sliced right through the middle of the wire, tearing the top half of the cable to shreds while the bottom half was undamaged. The airplane ended up in the lakebed overrun, luckily no damage. The hook point had been used for several roll-in engagements and was ground to a sharp edge.

Also, the maximum vertical design load on the F-16 nose gear was predicted to be arrestment, and that was demonstrated during the series of 96 arrestment runs. Max landing and taxi load was about 10,000 lb, while the max arrestment load was 19,000 lb.

johnwill, yes wire damage can be an issue with older hook designs looking a lot 'sharper' than hook designs today. One classic damaged wire arrest had an A4G on the last No.5 wire about to break it (but it was stopped by then) with only a few strands above where it would have broken completely. Other incidents caused the wire to 'snap back' with equal force dragging the A4G with it and because the nosewheel castored freely it spun around on the wet deck almost going over the side before stopping. Wide Long Decks are Good.

The maximum arrested landing weight and airspeed (Optimum Angle of Attack) are crticial and in the case of the current USN arrest equpment onboard how the aircraft are designed/modified or weight reduced (by reducing fuel / stores) to achieve that maximum. In the case of the F-35C this short 1Mb PDF will help explain a lot of the criteria (otherwise other PDFs mentioned elsewhere will explain in more detail - or posts on this forum will do the same).

The Influence of Ship Configuration on the Design of the Joint Strike Fighter

http://handle.dtic.mil/100.2/ADA399988 (1Mb)

The ground/deck speed is critical so sufficient WOD Wind Over the Deck must be generated so that this limitation is also not exceeded for the arrestor gear in use. I have read that the new Advanced Arrestor Gear ARG wires will be made of polymer strands - what this means in practice I don't know.
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Advanced Arresting Gear underway

http://www.thefreelibrary.com/Advanced+ ... 0133646031

"General Atomics has received a $95.8 million contract for system development and demonstration of a shipboard-representative Advanced Arresting Gear. The system will be installed at Naval Air Systems Command facilities in Lakehurst, N.J., beginning in 2006, and testing with unmanned test vehicles is expected to begin in 2007. Land-based aircraft testing is slated for 2009, and initial shipboard operations expected by 2014. The AAG will be retrofitted into existing Nimitz-class aircraft carriers and installed in follow-on types as they are built. Designed to meet the needs of Navy air wings through 2045, the AAG will be able to recover heavier and faster aircraft as well as unmanned aerial vehicles."
_________________________

http://atg.ga.com/EM/defense/aag/index.php

"Advanced Arresting Gear (AAG)
The Advanced Arresting Gear (AAG) program will retrofit and forward fit Navy aircraft carriers with an electric motor based system that will replace the current MK 7 hydraulic system for aircraft deceleration during recovery operations. AAG allows arrestment of a broader range of aircraft, reduces manning and maintenance, and provides higher reliability and safety margins. GA’s design replaces the mechanical hydraulic ram with rotary engines using simple, proven energy-absorbing water turbines coupled to a large induction motor, providing fine control of the arresting forces.

The system provides significant benefits over current recovery systems
Operational capability to recover projected air wing, with renewed service life margins
Full compatibility with CVN 68-class and CVN 21-class carriers
Higher availability
Self-diagnosis and maintenance alerts
Reduced manning and Total Ownership Cost (TOC)"

Hey Spazsinbad...... thanks for sharing the "The Influence of Ship Configuration on the Design of the Joint Strike Fighter" article it was an interesting read.

No aspersions being cast on anyone including the above but that particular PDF has been mentioned many times on this forum and probably multiple times on the 'very long thread' but I guess one can only read so much at any given time eh. So thanks for reading it - there are other PDFs/websites out there - often also about the ski jump for CVF deck requirements - but that is now defunct sadly. Anyhoo here is some more reading in a small PDF about AAG with only some relevant to the new 'wires' technology excerpted. The AAG is going to be good. Perhaps that was a factor in the tardy testing of the F-35C hook? But I'm only guessing.

NAVY TRAINING SYSTEM PLAN FOR THE ADVANCED ARRESTING GEAR Feb 2002

http://www.globalsecurity.org/military/ ... i_2002.pdf (122Kb)

"The AAG system consists of four units, where a unit is defined as a single recovery wire and associated equipment. It is envisioned that the AAG deck configuration will utilize a “3 + 1” recovery wire configuration, where a maximum of three recovery wires are rigged on three of the units at any given time. The remaining unit may be utilized as a spare, enabling a recovery wire to be rigged in the event one of the other units becomes unavailable....


...DESCRIPTION OF NEW DEVELOPMENT
1. Functional Description. The new AAGE will be designed to improve arresting gear structural integrity margins of safety from current MK-7 levels to values needed for future Fleet operational requirements. In addition, the new AAGE will be designed to provide a total life cycle cost savings by reducing both operational and maintenance costs when compared to the MK-7 arresting gear. The AAGE will also provide new operational capabilities, including the ability to safely and efficiently recover both heavier and/or faster aircraft and lightweight unmanned air vehicles (goal) that may enter the Fleet in the coming years.


2. Physical Description. The AAG Basic System for an aircraft carrier is composed of four AAG engines (three pendant engines and one barricade engine), and one basic operational control system. The AAG Basic System will also include the operator workstations and external interfaces that the AAG requires. The AAG system will interface with the current MK-7 sheave damper, fairlead, and deck sheave systems, as well as the purchase cable and Cross-Deck Pendants (CDP). The AAG basic System will be upgradeable to the Pre-Planned Product Improvement (P3I) System with minimal redesign.


The AAG P3I System will be comprised of the following P3I block upgrades, in order of preference:

° Option (1): Enhanced Control System for the Basic AAG system with the following
capabilities: conditioned based maintenance, automated diagnostic troubleshooting
and prognostic capability, reach-back maintenance capability, Interactive Electronic
Technical Manuals, continuous system status condition monitoring, Built-In
Test/Built-In Test Equipment (BIT/BITE), embedded operator training, and other
enhancements. The Enhanced Control System will include the capability to provide
for an Integrated Arresting Gear Control Station.

° Option (2): Redesigned sheave damper system (may be an active control system)
with capabilities compatible with the Enhanced AAG Control System.

° Option (3): New high-strength, lightweight Purchase Cable and CDP....

...3. New Development Introduction. The AAG will be developed in two blocks. Block I will meet the requirements for CVN 68 class backfit and CVNX 1. Block II will meet the requirements for CVNX 2 and follow-on ships. Block II will build upon Block I. Commonality between the two blocks will be maintained to the maximum extent....

...5. New Features, Configurations, or Material. The AAGE program will also look at other new technology, as cost and technical risks permit, such as the use of new, high-tech materials for the purchase cable, CDP, or other new technologies and materials. Previous work has shown significant dynamic load reductions can be realized by utilizing high strength, low weight, purchase cables and/or CDPs. Higher elasticity as well as low inertia tends to reduce the magnitude of the impact generated kink wave. The primary limiting factor for these high strength, low weight materials has been life. The materials must be capable of surviving the harsh and abrasive sea environment....

...The AAGE system will also have an embedded routine that tracks hits on individual CDPs that must be changed after every 100 aircraft traps on the CDP. The AAGE will also have an embedded system for tracking any other system component that has a limited life (e.g., purchase cable, etc.)...."

Hey Spazsinbad...... thanks for sharing the "The Influence of Ship Configuration on the Design of the Joint Strike Fighter" article it was an interesting read.

+1

I thought it worthwhile to repeat this item from this thread [http://www.f-16.net/index.php?name=PNphpBB2&file=viewtopic&p=210648#210648] because it is also appropriate about the question 'how is the damage to the wire monitored'. Of course when flight deck ops finished the wires will be inspected as required both 'up and down' stairs.
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A 4 minute Utube Video shows A4G Carrier Ops from a 'level with the flight deck' viewpoint here: [This is 'carqual' carrier qualification so the first two approaches are with hook up and the third is hook down for arrest - then first catapult] See:

A brief history of tailhook design
http://www.f-16.net/f-16_forum_viewtopic-t-16571.html

A4G Skyhawk CarQual YOUTUBE VIDEO: http://youtu.be/sCo70B9sBdU

Video shows 'hook runners' at work and one incident when the A4G gets 'hung up in the wires' with a big rush of deck crew to get it fixed. Note how the A4G rolls back slightly - this is the chance to hit the brakes to allow the hook to disengage from the wire. However 'sprog' pilots are often so discombobulated by the arrest that they forget the niceties. Often they forget to put the speedbrakes in also.

Note that in this later era the PO in charge of the 'hook runners' checks the arrest wire at arrest point for damage.

All you need is a hook, some rope and a few sandbags....

TEG

[quote="That_Engine_Guy"]All you need is a hook, some rope and a few sandbags....

TEG

Ahhh TEG... I think there are a few forum members that need that surprise...Happy holidays to you, your family, and all that make F16.net what it is.

At one point chaps used to run alongside the landing aircraft on deck and catch it to bring it to a halt. Landing speed was walking pace when wind over the deck factored in. Anyhoo this is my favourite quote about USN arrest gear (lifted from the other arrest thread):

Weekend Wings #38: The F-111 Aardvark, Part 2 Saturday, December 4, 2010

http://bayourenaissanceman.blogspot.com ... art-2.html

"...Furthermore, the US Navy (with aircraft carrier operations in mind) had specified a maximum aircraft length of 55 feet, and (most important of all) a maximum weight of no more than 50,000 pounds, for its F-111B model. This was critically important. The arresting gear fitted to US aircraft carriers had to decelerate heavily-laden aircraft from flying speed to a standstill in no more than 300-400 feet of flight deck space. The gear had to absorb all the kinetic energy of the aircraft, which could be very high. (For example, the current Mark 7 Mod 3 arresting gear on USN Nimitz-class carriers can stop an aircraft weighing 50,000 pounds, traveling at a speed of 130 knots, in a distance of only 340 feet. That means absorbing kinetic energy of well over 45,000,000 [forty-five million] foot-pounds.)..."

Some esoterica: Postwar growth and arresting developments

http://www.thefreelibrary.com/Postwar+g ... 0269338956

"...The Langley included nearly everything we now take for granted in a modern carrier: aircraft, flight deck, catapult and arresting gear. The last item was, admittedly, a very clumsy, primitive arrangement that often resulted in bothersome tipovers and damaged props and wings. Almost from the beginning, refining the arresting-gear system became a priority.

A new design raised the cable over the flight deck with the help of vertically placed wooden boards, nicknamed "fiddle bridges" because of their resemblance to similar devices on violins. In August 1921, an unusual layout was constructed in Norfolk consisting of a turntable and these raised cables. Lt. Mel Pride [Alfred Melville Pride, 1897-1988] was in charge of the project. The new design would be installed in Langley after testing ashore.

One of the aircraft often used for testing early developments was the Aeromarine, a late World War I design barely able to attain 73 mph with its 100 hp Curtiss OXX engine. With the turntable pointed into the wind, the 24-year-old lieutenant. Pride taxied his Aeromarine toward the turntable, aiming for the wires, barely making 15 mph. Judging his position, he gunned the engine, becoming airborne for a few seconds before retarding the throttle and settling down into the wires with the control wheel buried in his lap. The aircraft's main gear screeched across the platform as the hooks mounted on the spreader bars scraped into the fore-and-aft wires. The tailhook then picked up the cross-mounted wires on the fiddle bridges...."