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Carrier landings Decceleration & Pilots Head

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Carrier landings Decceleration & Pilots Head

Old 13th Mar 2017, 17:26
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Carrier landings Decceleration & Pilots Head

Carrier landings Deacceleration approach at 160-180Knots ? or slower
Short Distance from arrestor to stop 100 metres ???
Questions
Approach speed ?
Deacceleration Distance ?
Forces on Deacceleration ?
What happens to the pilots head with a Heavy Helmet on is it restrained does it dip forward and down or can neck muscles control or restrain it ?????

Thanks
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Old 13th Mar 2017, 18:53
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I don't know the exact answer but don't forget to subtract the forward speed of the boat and any wind over the deck. That makes impact speed a little more palatable but still pretty violent.

BV
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Old 13th Mar 2017, 19:18
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All this recent research finding long term brain damage in American footballers, soccer players and boxers from the brain banging around in the skull; then you look at the forces exerted on a catapult and by a cable arrest.

Explains a lot - though not Sharky......
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Old 13th Mar 2017, 20:10
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Out of interest, how different is a carrier's cable run out and deceleration force as compared with, say, taking the approach end aerodrome RHAG in an F-4?

I didn't find RHAG engagements particularly severe - but what was it like taking a wire on the Ark Royal in an FG1 back in the days when the UK could afford real carriers?

Last edited by BEagle; 13th Mar 2017 at 22:38.
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Old 13th Mar 2017, 21:01
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TJ,

Perhaps I can help a bit.

Approach air speed will be around 150 knots. Actual 'trap speed', when the aircraft engages the arresting wires, will be reduced by the Wind Over Deck (WOD) generated by the carrier's speed through the water. I believe, (but am happy to be corrected) that maximum 'trap speed' is around 150 knots, but that they usually aim for around 130 to reduce wear and tear on the wires. I could be wrong on the figures here though.

Yes, deceleration distance is around 100 metres.

Forces - that's where i have to admit lack of detailed knowledge - these will depend on the time/distance/ force schedule of the arresting engines (the large hydraulic engines below decks that allow the arresting wires to pay out, all the while applying the braking force). The scheduling of the arresting engines is adjusted not only for the type of aircraft, but (I believe) also for the weight of the aircraft as they trap. A heavier aircraft needs more force to bring it to a halt before it falls off the deck, but a less strong aircraft (say an AEW aircraft) can't sustain as much retardation force through the hook system as, say, a fighter.

Your question about heavy helmets is a good one. A the weight of helmets has increased, especially on the F-35, I am sure that the USN Navair community will have been providing very detailed guidance and instruction on how hard the aircraft can be arrested without the pilot having excessive strain placed on his neck, shoulder and upper back.

Hope this helps, best regards as ever to all those good Navair people solving those hard naval aviation issues,

Engines
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Old 13th Mar 2017, 21:51
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Thanks 'Engines' I'll guess you were thinking about the F-35C with your reply. 'Sharkey' Ward flew the RN F-4 before transitioning to the Hairier AFAIK. Two A4G videos in slow motion - particularly the 'arrest' show how the pilot reacts to the forces being applied. In this case the A4G can be in a range of KIAS (depending on aircraft weight at Optimum Angle of Attack) whilst decelerating on arrest in less than 300 feet (the last wire No.6 from Sea Venom/Gannet era of HMAS Melbourne was removed for A4G/S2E/G because there was not enough room for arrest).

True story: An A4G pilot - not me - arrested onboard at least twice when NOT 'harness locked'. Luckily helmet visor was down preventing face injury as it hit the gunsight with force. Why was this so? A long story indeed.

IIRC USN pilots mention 3-4 lateral G for their catapulting these days down the approx. 300 foot cat track to get to flying speed at usual launch weights. VX-23 test pilots ashore using land catapults go up to 6G during testing they claim IIRC. A4G pilots rattled down the 100 foot track at 6G regularly - it is as though one is THUMPED in the chest by a closed fist with all the power one can stand - in less than two seconds.

Regarding an A4G arrest at wheelspeed of say 100 knots to zero in say 275 feet I would comment the first one was just bewildering indeed. It is nothing like a land arrest on a runway short field arrest with some 1,000 feet of run out to stop. My first arrest was followed by first catapult which is always followed by a send home for newbies because how much can a KOALA BEAR in one day. For sprog pilots such as meself this was my first arrest and catapult ever (poorly trained by RAAF crabs initially for carrier aviation).

Catapult pilots have their heads back against the ejection seat headrest in preparation for the launch so in the case of the A4G there is no head movement. In videos we see the heads of the USN jet people bobbing up and down initially (which is an issue for the F-35C at moment when aircraft at light launch weights such as for CarQual).

Graphic from A-4E/F/G NATOPS shows relationship between Skyhawk weight and Optimum Angle of Attack airspeed for an arrested carrier approach. The MELBOURNE LSO Notes show Maximum Engage Wheelspeed for the A4G to be 107 Knots. If one follows 'Engines' explanation then Approach KIAS at a specific allowed weight with a specific WOD may be deduced. The red lines/circles show the max. arrested landing weight of 14,500 lbs with Opt AoA airspeed of 128 so if the max arrest wheelspeed is 107 then the WOD (combined ship speed [which MELBOURNE could achieve max 21 knots] and wind speed down the angle deck should be more than eleven knots. There would be a buffer for sudden reductions in wind speed. MELBOURNE at 21 knots was a sight to behold & experience - the shaking - oh the horror.



A4G Arrest HMAS Melbourne & Hook Runner Slow Motion


SLOW MOTION Catapults A4Gs 886 & 889


Last edited by SpazSinbad; 14th Mar 2017 at 01:43. Reason: add graphic then text about same
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Old 13th Mar 2017, 22:41
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From Engines post and assuming a constant deceleration

v^2=u^2+2as

130 knots is approx 66.9 m/s
distance is 100m, so deceleration is 22 (ish) m/s^2

which is 2.3g. (Various bits of rounding there).

Now I know nothing about the profiles of the arrest, but I would have thought a constant deceleration gives the minimum as any non-linear piece would (I think) imply greater deceleration at another time point.
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Old 13th Mar 2017, 22:54
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Formulae may indicate approximations of the forces felt during an arrest and catapult however the steam catapult applies more force in first stage of launch compared to later stage. EMALS will even out these forces to create less stress for all concerned. Similarly the Advanced Arrestor Gear (AAG) will even out the arresting force for all users.

In the video below CMDR Clark describes his first A4G arrest/catapult. In mid 1960s when the RAN FAA was regenerating fixed wing ops he was trained in USN with a bunch of others so he has arrests and free deck launches in the Trojan T-28C. Subsequently he went to Vietnam with the Iroquois RANHFV (hence 'shot at' references). Upon return he transitioned to the A4G Skyhawks (other pilots similarly did same). He says "under two seconds' which is clipped out in the poor quality video. In second video LCDR Ward USN famously exclaimed "HOLY SHI T!" after his first A-4B catapult (demo) from HMAS Melbourne mid 1965.

Clark A4G Skyhawk 1st Arrest & Catapult HMAS Melbourne


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Old 14th Mar 2017, 00:28
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Google HAN's device...

https://en.m.wikipedia.org/wiki/HANS_device

"A major cause of death amongst drivers during races was through violent head movements, where the body remains in place because of the seat belts but the momentum keeps the head moving forwards, causing a basilar skull fracture resulting in serious injury or immediate death.

Notable race car drivers who died from basilar skull fractures include:

Formula 1 driver Roland Ratzenberger [3] in the 1994 San Marino Formula One Grand Prix. (Ayrton Senna also sustained a basilar skull fracture that might have been lethal in this Grand Prix, but the official cause of death was brain penetration by shrapnel[citation needed])
Indy 500 drivers Scott Brayton, Bill Vukovich and Tony Bettenhausen
NASCAR drivers Adam Petty, Tony Roper; Kenny Irwin, Jr.; Terry Schoonover, Grant Adcox, Neil Bonnett, John Nemechek, Dale Earnhardt, J. D. McDuffie, and Clifford Allison
ARCA driver Blaise Alexander
CART drivers Jovy Marcelo and Gonzalo Rodríguez"
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Old 14th Mar 2017, 00:47
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Racing Car Drivers Dead in Race Car Crashes - wut? Famously (or not) carrier landing arrests are described by the MEEDJA as 'controlled crashes' - emphasis is on CONTROL! Here are some more examples from MELBOURNE in 1976. I'll RESTRAIN MEself. At end Helo view is from a plane guard Sea King I'll imagine.

1976 HMAS Melbourne Fixed Wing Carrier Qualification

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Old 14th Mar 2017, 03:14
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maybe they could use this on the f35 helmet?

https://en.wikipedia.org/wiki/HANS_device
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Old 14th Mar 2017, 03:52
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Oh well... we can't keep a good F-35C thread down eh. Already there are 'concerned' criticisms about 'look back' in the F-35 cockpit (solved by Norsk pilot saying "lean forward then look back"). Wonder you didn't mention air bags - I guess - for the arrest. The F-35 ejection seat system has a similar 'blow up' HANS helmet restraint during ejection. One can watch a long or short version of a Martin-Baker Slow Motion F-35 ejection seat video or perhaps a screen shot'll do. Dunno. My fav slomo is this one. start at if bored: https://youtu.be/DbQuaG4NfN8?t=255 4min15sec

AFAIK no NavAv pilot has complained about arresting forces - they are grateful - NavAvers/Birdies are a tuff breed.




Last edited by SpazSinbad; 14th Mar 2017 at 04:03.
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Old 14th Mar 2017, 04:16
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IIRC, the standard RN cat stroke was 100ft/1second: Ark's two cats were 180ft and 200ft, so about 2 seconds was right. The Melbourne cat certainly looks a tad shorter, I'd be interested to know just what length it was?

I only scored a night back seat ride in a Gannet AEW3 off the Ark, it seemed quite sedate after catching the wire. Nearly woke me up

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All this talk reminds me how much better it is to stop, then land, when recovering on a Grey Funnel Liner
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Old 14th Mar 2017, 04:34
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John.

My memory is poor, and I have no documentation to refer to, but I seem to remember the cat shot on the Melbourne was around 93 feet. A very (!) short run to get our end speed.

The shortest deck run in the Sea Harrier was 200 feet (i.e. just at the start of the ramp), and recall thinking how ridiculous half that distance was, for double the end speed!
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Old 14th Mar 2017, 07:05
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Spazzo, it was worth watching the whole video just for the Inna Gadda da Vida backing track!
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Old 14th Mar 2017, 07:09
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'OK4wire' has a good memory but like a piece of string - it all depends. In the Sea Venom / Gannet era the catapult stroke length was reportedly 90 feet. The Venom was limited to about 4.5 lateral G for catapulting so was limited in hot conditions, nil wind in the tropics (a familiar refrain perhaps hence SRVLs for the BeeBabies). The A4G Skyhawk was not so limited with a 9 lateral G limitation. It was said a 'warshot' could fling the A4G at max weight 24,500 lbs under any conditions except HADES. However CHLOE would have been the only bit of metal to undergo such torture.

After collision with USS Frank E. Evans in 1969 the repaired bow included a 'bridle catcher' with provision to lengthen the catapult by some ten feet. How much stroke length that meant has never been clear. Anyway by 1970-71 the actual stroke length was increased to 100 feet - some say 105 feet - with parts from HMCS Bonaventure. And I guess we can take that as stroke length. I can recall being told the catapult stroke was 100 feet long late 1971 early 1972. The slow motion film of catapulting the A4G was to see how the 'bridle catcher' was working. Centreline stores would have the fin removed so that the 'catcher wire' would not interfere with it. Aboard USS Kearsage [a wood decker] in 1969 when cross decking our one and only buddy refuel tank at that time was damaged by the arrangement of the 'bridle catcher'.

Last edited by SpazSinbad; 14th Mar 2017 at 07:42. Reason: Kearsage
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Old 14th Mar 2017, 07:14
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'Ascend Charlie' (is it not TIME? :-) ] There is another slightly less long with my actual favourite of favourite track of sound - especially appropriate at the end:

F-35 MB US16E Ejection Seat Tests 1-8 Slow Motion Long Play 10min 18sec

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Old 14th Mar 2017, 07:44
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USS KEARSARGE CV-33 with Hydraulic Catapults & WOODEN DECK
A4G 886 Cross Deck May 1969 “...on the occasion of the first launch of an Aussie A4 and as the aircraft was hauled down the rather more sluggish Hydraulic Catapult it deposited a selection of various pieces of debris which came tumbling down the timber flight deck of 'Kearsarge'. Note that she was commissioned several years prior to 'Melbourne' though larger and considerably better equipped. These foreign objects included a selection of Buddy Store scupper drains, covers and miscellaneous hardware which had been torn from it by the untidy and voluminous bundle of webbing belts which were used to prevent the catapult strop from leaving the ship....” Ray (Dutchy) Brauer
From Dutchy Brauer - HMAS Melbourne/USS Kearsarge 'Crossdeck operation '69
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Old 14th Mar 2017, 11:32
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Much talk of pilots' heads on this thread.

Dont forget, in F4's and the like there is/was the observer's/navigator's head to consider as well

Or don't they count?
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Old 14th Mar 2017, 11:49
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I believe it's the larger size of the pilots' which is of concern.....
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