Does anyone know much about catapults and arrestor gear?
I have tried to find some information about the sets on Ark Royal and Eagle and other RN carriers.
In there last lives was Ark Royal and Eagle equipped with the same sets of catapults. I thought i read somewhere that on Ark Royal could properly launch the F-4 Phantom and only off its waist catapult. Was this the case or were both catapults the same type? Was it the same for Eagle i heard that she didn’t get the same modernization as the Ark. Did eagle have different catapult types?
One of the stranger things i thought i read was that the arrestor gear was designed to be able to stop any weight of plane or something like that? Maybe it was in the same distance regardless of weight and that they had a big advantage compared to american arrestor gear by being able to handle any weight?
I think what confuses me is the catapults made by different companies and them all having different numbers and then to make it even more difficult they had different lengths too. The Uk should still have the ability to make catapults and arrestor gear if required i think. Companies like McTaggarts still exist today and i would think they would still have the plans. There factory is only a few miles outside Edinburgh. They are in the process of building the aircraft carrier lifts for CVF.
Also another question is were the Majestic and other classes built in WW2 and after only ever equiped with 1 catapult? This would seem a bit risky if it breaks. You see in pictures of the Canadian carrier and 25 de mayo and Melbourne and other carriers operated only 1 catapult. Also a great number of different types of catapult and length were used. Did they all originally have the same type.
Trying to find out about arrester gear is even harder. Were all ships fitted with the same design? Did these have to be upgraded or were they all strong enough from the beginning?
When i look at how EMALS are progressing i think these will be the way forward and maybe CVF will get them in 20 odd years.
I imagined the Americans have a big lead in catapult development but then someone said to me there haven’t really been any improvement’s over what ark used in the 70’s? Not sure if there is much truth in that?
The hydraulic catapult. Has technology improved in anyway to allow these to make a come back? what was the limiting factors that prevented there development any further?
Also had 1 last thought. When an aircraft is launched with a Bridle attached to the fuselage would this put less strain on the aircraft than when being launched by the nose wheel? one would think so but does the main strain for on the aircraft come from arresting or from catapulting?
By: Obi Wan Russell - 15th July 2009 at 17:42
Ok. just a quick summing up: Eagle was fitted with two BS 5 Catapults 1959-64, replacing her two bow mounted hydraulic catapults. The new portside bow catapult was 151ft stroke length and could launch fully loaded Sea Vixens and Buccaneers, the new waist catapult was 199ft stroke length, and the extra power was intended to help in low/nil wind conditions often encountered in the hot and high far east. Due to the constraints of Eagle’s (and Ark’s) deck layout, it wasn’t possible to fit the longer catapult in the bow position, hence the odd sizes. Ark received two BS4 catapults (145ft stroke length) when originally fitted out (1955) and retained these until 1967,when she was refitted for Phantoms. Again she recived a 199ft BS 5 in the waist position, whilst her port forward BS 4 was rebuilt and extended to 151ft, effectively becoming a BS 5 in all but name. Additionally Ark’s catapults were fitted with a bridle catching system as the bridles used by the Phantoms were more expensive than those used by the Buccs/Vixens/Gannets. Eagle had CALE roller positioning gear fitted to her catapults (alowing aircraft to taxi on to the cat and then be lined up correctly by the gear. These were omitted/removed from Ark in 67-70. Ark also differed in having water cooled four segment Jet Blast Deflectors to cope with the heat of the Phantom’s RR Speys in full afterburner. Eagle (and Hermes, Victorious and Centaur) had non cooled steel plate JBDs, angled to deflect the jet blast upwards and overboard sideways. The other three carriers mentioned above had BS4 catapults, Centaur had two 103ft cats, as did Hermes when completed. Hermes recieved a BS4A 145ft cat in 64-66 on the portside, whilst Victorious had two 145ft cats from 1958 onwards.
All three ships had CALE gear as well. Eagle post 64 had Direct Acting Arrestor gear (DAX I), as did the others, but in 1968 she recieved a single DAX II wire for Phantom trials. Ark recieved four DAX II wires 67-70. Both Ark and Eagle’s forward cats could launch Phantoms, but if the F-4s were fully loaded for a bombing mission the waist cat was used. For the Phantom trials in 68, Eagle only used her waist cat and the JBDs were not raised, instead a thick steel plate was chained to the deck to avsorb the heat from the Spey engines. After launch, the plate which would glow white hot was cooled down with fire hoses before the next aircraft could taxi over it. All arrestor gear systems aboard ship are designed to stop the aircraft in the same distance, but the differing weights and speeds of those aircraft are dialled into the system before each recovery to adjust the tension (a phantom hits the deck a lot harder at 130 knots than a Gannet does at 90 knots.)
When the light fleets were designed in WW2, catapult launches were still optional, most takeoffs being free rolling and into wind. The catapult’s purpose was to allow more deck to be used for ranging a strike, the first half of which would be catapulted before enough deck space was available for normal rolling takeoffs. Postwar fitting steam catapults to the light fleets was something of a squeeze, and given the reduced steam plant in these ships (40,000shp/25 knots compared to the Centaurs 80,000shp/28+knots) running two cats may have been counter productive as they would have drawn more steam than could be spared without losing speed/wind over the deck.
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July 15, 2009 at 4:25 pm