An utterly daft question about aircraft carriers

[18-Wheeler]

I was just watching a documentary on WW2 aircraft carriers, and sitting near the stern were a number of piston aircraft warming their engines up.
For no particular reason I wondered if you could get a bit more speed out of the carrier if you put all the aircraft on deck, tied them down, and gave the engines a bit of power?
I mean, say each piston fighter has about 1,500hp, and you can get twenty on the deck then that's another (inefficient admittedly) 30,000hp to help move the ship.
How about jet aircraft on a modern carrier? Less likely to overheat though hot air ingestion for the aircraft near the back would be a bother.

</daft though of the day>

[henry crun]

I have seen photos of WW2 carriers using their aircraft to assist in docking, but they only appeared to be used to move the ship sideways.

[Three Wire]

Jet powered aircraft were no use, but propeller powered aircraft were considered a valuable resource by the fisheads driving the aircraft platform.

Operation Pinwheel used propeller powered aircraft strategically placed on the flightdeck and suitably tied, lashed and chained down, to aid the ship in close quarters manoeuvering. They replaced tugs which probably were on strike, or not big enough to provide motive thrust.

I last saw this in Melbourne in the early '70s when the tug company went on strike. The AEOs hated it as they saw it as an abuse of airframes/engines.

So, no they couldn't aid the ship in going faster, but could help you get alongside. Oh, and the stokers were known to burn a bit of jet fuel in the ship's boilers as well!

[stilton]

Watch 'the Bridges of Toko Ri' with William Holden for an early scene in the movie that shows this 'Pinwheel' evolution using chained down piston fighters to assist in docking.


The Co of the squadron goes over the head of the Captain to complain directly to the Admiral of the abuse to his fighters engines.


With diastrous results to his career..


A fun flick though with some great airborne scenes on and off the carrier.

[Captain Dart]

The Australian carrier HMAS Melbourne was docked on a 'stinking' hot day in 1980 or '81 at Station Pier, Melbourne, using Grumman Trackers chained to the deck for the 'pinwheel' manoeuvre (The 'wharfies' were on strike as usual). A miniature 'Bridges at Toko Ri' scene was subsequently played out between engineers, pilots, flight safety officers and ship's crew regarding alledged exceedence of aircraft engine operating temperatures. But that's naval aviation; the ship comes first (aircraft are just another weapons system).

[18-Wheeler]

Thanks gents!

[dixi188]

I had a tour of the USS Nimitz in the '70s when she was anchored in Spithead.

I recall being shown the lower hangar deck which had an engine running bay at the aft end where jets could do runs without affecting flight ops. There were shutter doors to open at the back and side and shut off the rest of the hangar.

I think an F14 or F18 at full re-heat should help the ship along, but with two neuclear reactors I doubt it needs any help.

[ReverseFlight]

On the subject of aircraft carriers, I understand that there is a time-honoured procedure (pre-GPS) which enables aircraft to locate and return to a moving mother ship without the ship having to emit signals to alert the enemy. How does this work ?

[Capot]

Intrigued by the post about finding the carrier, I rang my friend, ex RN and a helicopter pilot.

"Ah yes" he says, "I know that one. It's simple".

"Plot your circle of uncertainty centred on where you think the carrier is. 25 miles radius would usually be right for a jet, 1 mile for a chopper.

Then, find out the wind direction and speed at 5,000 ft above the sea. Plot the point on the circle's circumference precisely upwind of the centre. Then fly round from that point, clockwise and observing inwards, at 5,000 ft in ever-decreasing circles until you find the carrier. Anything else you want to know?"

"How do I find out the wind direction and speed?"

"Call the bleedin' carrier, of course."

He's retired now. He once dropped my gun* into the sea - after converting to a Wessex - when some one said "What's the time?" and he answered "Eight Bells", whatever that means. He explained later that the hook release button was where the PTT used to be.

PS That's gun as in 105mm gun, not gun as in 9mm peashooter...

[glhcarl]

Watch 'the Bridges of Toko Ri' with William Holden...

A fun flick though with some great airborne scenes on and off the carrier.

I would hardly call the film (or book) fun. The stars Holden and Mickey Rooney both die.

[stilton]

Not to burst your bubble Glh but it was just a movie.


They didn't really die..

[PLovett]

While we are talking about aircraft carriers I have another question, with apologies to Brian Abraham who told me the answer but in my dotage I have forgotten.

The moder carrier flight deck is, I think, at 15 degree angle to the centreline of the ship. Now with the carrier doing perhaps 20 to 30 knots into a not inconsiderable headwind at times and with a jet at something like 130 knots on approach to land. Does the pilot make any allowance for crosswind? Is there any crab angle applied and if so is it removed prior to touchdown or does the undercarriage have to take some lateral strain as well as vertical?

[Intruder]

"Aim for the crotch" -- the intersection of the angle deck with the straight deck. That axiom works for normal situations, and only slight corrections need be made.

Ideally, the wind is down the angle. Often when the ship has to make its own wind, it is "axial" -- down the straight deck -- requiring more correction.

[Captain Dart]

HMAS Melbourne only had a 5 degree angle. To recover aircraft, the 'fish heads' would steer the ship so that the wind was down the angled deck. In calm winds, as Intruder alluded to, the wind would be axial causing turbulence off the ship's 'island' (and a whiff of stack gas through the open overhead hatches if you were in a Tracker). Calm conditions on a moonless night were, to my mind, the most challenging for getting back on board!

[GANNET FAN]

Captain Dart and Three Wire, I remember at the end of a day out on HMS Ocean in which my father was serving, based in Malta just prior to leaving for Korea, when the Captain angled the Fireflies and Sea Furys at the stern to assist the tight turning cricle before picking up her mooring buoy.

The sound was thunderous and spine tingling!

GF

[mm43]

Does the pilot make any allowance for crosswind? Is there any crab angle applied and if so is it removed prior to touchdownMost modern angle-deck carriers set a heading so that the true wind direction and speed, coupled with the ships true heading and speed results in a relative wind direction down the line of the flight deck, i.e. ship's heading -15 degrees. This method effectively minimizes the turbulent airflow created by the topside structure on the starboard-side of the carrier.

This results in an approach where just prior to the threshold you make a small correction that results in the wind being "right on the nose" at touchdown. If you don't, it doesn't really matter as the hook has found the arrestor cable and you have stopped! The glide slope 'crab' is slightly right, and unlike a land based crosswind approach, when you take it off there is no x-wind, rather your runway is moving 15 degrees right of heading at the ship's speed through the water.

The whole situation is unfamiliar to non carrier trained pilots, as the wind-speed into which they are landing is comprised of two components made up by the actual wind-speed and the ships speed. So your GS at touchdown will be TAS minus wind-speed, minus relative ship-speed. In this situation the cross-wind factor is maximum on a calm day with the ship steaming, but as the relative angle between the wind direction and the ships heading doesn't exceed 15 degreees, the x-wind factor is negligible.

mm43

[Captain Dart]

Further to 'The Bridges at Toko-ri', does anyone remember a scene in the original movie where the character played by William Holden stands with his nose inches away from where the below-deck component of the catapult shuttle stops after each launch? When he stopped flinching he figured he had got his nerve back. My purchased DVD of the film does not include the scene; does anyone remember it??

[ReverseFlight]

Great post, Capot. Thanks to you and your friend - actually a good friend of mine who flew in the Marines in the Vietnam war forgot the details of the procedure and I'm sure this will help jog his memory. :ok:

[D O Guerrero]

Reverseflight - the RN use something called Outhouse (at least for rotary operations). Outhouse is a moving datum which has a set course and speed - this is given to the crew before they depart. The Ship then guarantees to remain within a specified distance (I forget the numbers) of the moving datum. The helicopter crew always know, therefore, roughly where the Ship will be on their return. If not emcon silent, they can then use ESM to find the ship.

[Pontius]

On the subject of aircraft carriers, I understand that there is a time-honoured procedure (pre-GPS) which enables aircraft to locate and return to a moving mother ship without the ship having to emit signals to alert the enemy. How does this work ?

Ah, that's an easy one.

At the briefing the Fisheads would give the ship's MLA (Mean Line of Advance) and you could predict where the ship would be by taking the recipricol of the course and adding 5 knots.

Example: Cod Face says he's going to go 180 at 10 kts. Therefore, after one hour you would search 360 at 15 nms from the launch position.

A truly excellent means of locating the boat was to combine the calculation above with poor weather. If, in the example above, there was a fog bank 20 nms north of 'Mother', then you could put money on the fact that the Fisheads would have piled on a bit more speed to ensure they were cloaked in fog ready for your recovery.

[Senior Pilot]

Of course the much easier way was to have the Looker plot the thing on his radar and give you a steer ;)

Emcon we'd use the plotting board up front and always win against the back seat with his Doppler plot: the darn thing inevitably slipped enough to give us the edge :ok:

[ReverseFlight]

Great stuff, thanks to everyone for their contribution. :D

[The SSK]

Three Wire: So, no they couldn't aid the ship in going faster, but could help you get alongside. Oh, and the stokers were known to burn a bit of jet fuel in the ship's boilers as well!

I fail to see how it would *not* make the carrier go faster. Newton's Law and all that.

I once asked on the rowing newsgroup whether my old man's four could tow a warship - admittedly a small one - 100 metres in half an hour, as a publicity/fundraising stunt. Some serious mathematicians and hydrodynamicists came up with the answer that we probobly could.

The comment was also made that if you stood on the edge of the dock and pushed against the side of the Queen Mary (or the Nimitz) it would move ... eventually.

[18-Wheeler]

I fail to see how it would *not* make the carrier go faster. Newton's Law and all that.

I agree - as I mentioned in the first post, it wouldn't be all that difficult to add a good 30,000hp to the forward thrust of the carrier, that'd have to give it another knot or two.

[Tinstaafl]

Another daft question: Why is the angled deck positioned behind the superstructure, causing the approach end to be in the wake? Why not arrange the deck to be ahead of the superstructure (or move the superstructure further aft, or both) so relatively undisturbed air is presented to the landing deck?

[Capot]

Don't be silly, old boy. The Royal Navy, just like every other Navy, prefers to stick to the tried and tested ways of doing things. Carrier superstructures have always been halfway along the side of the boat. That's where they go, see?

The superstructure could in fact disappear altogether. All you really need above the flight deck is a set of remote handling controls (retractable) for docking, and perhaps a place to mount the radar aerial(s). Otherwise the ship and flight operations could easily be managed from an office somewhere in its bowels, with sponsons on each side for those who simply have to look at the sea from time to time, as they are now.

But The Royal Navy has managed its ships from raised platforms since Samual Pepys was first appointed and the telescope was the best means of target acquisition and shouting was the only way of communicating, and who would be so foolishly revolutionary as to propose a change?

[Intruder]

Another daft question: Why is the angled deck positioned behind the superstructure, causing the approach end to be in the wake? Why not arrange the deck to be ahead of the superstructure (or move the superstructure further aft, or both) so relatively undisturbed air is presented to the landing deck?
The superstructure has been moved aft. Look at pix of Midway, Forrestal, Kitty Hawk, Enterprise, and Nimitz (evolving classes).

The ship drivers also sit in the superstructure, so their needs weigh into the equation...

[nomorecatering]

Why havent they made an aircraft carrier in the form of a catamaran or even a trimeran, 3 hulls would increase the usable space. and make it harder to sink with a torpedo. And the flight deck could be as wide as they wanted and i guess more stable.

[Mike Oxbig]

Have you ever been on a carrier? I have only served on the RN CVS and getting around one of those 'baby carriers' is hard enough, without adding the extra hulls to get lost on :\! Also I would imagine the cost would be prohibitive - I think it would be cheaper to build one hull instead of two or three.

Mind you, you could keep all the fishheads in one hull and the wafus in the other............................:ok:

MB

[3 Point]

Take a look at the designs for the RN's new CVFs. You will see two separate islands, one forward for the fish heads and one aft for flyco.

We came up with this idea and the logic was debated back and forth within the design team and found to stand up. Basically, the fish heads preferred a forward position to see better when coming alongside and the Air Department requirements favoured a more aft position to afford a better view of the approach and landing. Questions about communicating between the two were answered by using electronic means and the ability to have an emergency ship driving position in the aft island and an emergency flyco in the forward one gave good redundancy in the event of a hit in the superstructure.

Aircraft carriers do indeed need superstructure above the flight deck; where else would you mount the various antennae? Or where would you fly an ensign to lower it so dramatically during cocktail parties??

I pitched the two islands idea to the Navy at a design review meeting and expected to be shot down in flames however they were completely content (taken in!!) and the ship design today still has two separate islands!

So, looks like the RN is not too slow to adopt new thinking after all!

Happy landings (or recoveries)

[mm43]

3 Point omitted to say that the RN CVF carrier design is for an inline flight deck, but thanks for sharing the info.:ok:

http://i846.photobucket.com/albums/ab27/mm43_af447/royalnavy-cvf.png

Obviously the design doesn't allow for multiple operations, e.g. Nimitz class angle deck landings, twin catapults fitted forward and two aft. Notwithstanding, this new class of carrier is quite a step up from the RN's current Invincible class.

I'm sure the French will come up with a bigger version!;)

mm43

[Tinstaafl]

Looking at the Nimitz class: What I was questioning could be accomplished by angling the deck to the right instead of left so that it crosses in front of the superstructure. Superstructure on the left & 'behind' the present angled deck would also do it but with the penalty of occluding the deck during a left hand circuit.

There must be some reason why they're prepared to tolerate the wake from the superstructure?

[D O Guerrero]

Unfortunately WAFU's aren't known for their knowledge of anything related to actual Ships...
The Navigation Bridge is generally positioned directly above the pivot point of the ship when under ahead propulsion. This is a useful feature when getting the thing into harbour (if you're going to navigate visually, which is often the case), which is occasionally desirable. Its nothing to do with Pepys, shouting or telescopes. Being high up is also quite nice too - you can see stuff. Which is why there are also windows. Being able to see stuff is quite good for avoiding other ships or big rocks and lighthouses.
Admittedly in carriers, the bridge is positioned by necessity in the island, which has to be displaced to one side. Moving it for'd or aft would completely bugger things up though... So its a bit of a compromise. I suppose parallel runways with the island in the centre would be the ideal solution. But then the FOD plod would really take forever, whilst being just as much a waste of everyone's time and effort.

[mm43]

@Tinstaafl

Think about the following situations:-

(a) On a calm day and the ship steaming at 20 knots, the relative wind is across the line of the flight deck and any aircraft FU's will end up in the superstructure.:eek:

(b) On a day with a 25 knot wind, the ship when steaming sets a heading to provide a relative wind down the line of the flight deck. Any FU's and the ship is still effectively heading across the intended line of flight.:\

The angle deck carriers are designed to minimize the above situations, and furthermore the superstructure is on the starboard-side because that is the 'give-way' side and the Fish Heads prefer to see everything on that side.:ok:

mm43

[Tinstaafl]

Ta. Hadn't thought about downwind effects of a crash.

[3 Point]

The design for the CVF when I worked on it could accommodate either a straight deck or an angle; at that time the decision to go STOVL or CV had not been made and the design could easily have been built either way. When we persuaded the RN to accept the two islands we argued its merits for both the CV and STOVL case.

D O Guerrero is right, us WAFUs don't know much about ship driving but what he says pretty well explains why we ended up with the bridge in the forward island and flyco much further aft. The two functions demand entirely different positions relative to the hull/flight deck and all previous designs which co-located them were a severe compromise (usually in favour of the fish-heads).

Happy landings

[Mike Oxbig]

Tinstaffi,

In the old days an angled deck also stops 50,000 tonnes of ship running you over when the catapult only goes whoosh instead of wwwhhhooooooossshhhhhhh!! Also if you fall off the end when landing!

Remember the Stig going over the ramp of Invincible and getting run over in his XJS?

[Senior Pilot]

In the old days an angled deck also stops 50,000 tonnes of ship running you over when the catapult only goes whoosh instead of wwwhhhooooooossshhhhhhh

Stand fast those on the bow cat ;)

3 Point,

Reminds me of all those times sitting in the stack gas on 6 Spot while Ark's Flyco forgot all about us: until released from FW recovery with the wind at Red 90, out of limits, and then cleared for take off :ugh:

[Tinstaafl]

I was aware of the angled deck's advantages. What I couldn't understand was the relative positioning of angle deck vs island, leading to turbulence for the landing.

[D O Guerrero]

Tinstaffl - I explained it above.

[Dutchy805]

I was a member of 'Melbourne' ship's company in '65 when the ship docked at Brisbane en-route to Hervey Bay for 'Heeling' trials then, New Guinea, Krakatoa and Guadalcanal.

As tugs approached to dock the ship the Captain sent them packing as he had Fairey Gannets lashed to the flight deck which he used to pull us into our berth.

This is the only occasion in 24 years of RAN/FAA service ['64-'88] on which I saw this operation utilized although I believe our S2 Trackers also performed this 'pinwheeling' procedure.

[18-Wheeler]

Thanks Dutchy, I knew it would work. :)

[Smilin_Ed]

What I couldn't understand was the relative positioning of angle deck vs island, leading to turbulence for the landing.

The "burble" as it is called in the USN is no big deal. If you know how to fly an airplane, you just fly through it.

[Centaurus]

A helicopter landing ship designed and built in Spain (I think) is now in Melbourne, Australia, undergoing extensive fitments for its role as a cargo carrier, troop carrier and helicopter carrier. The front deck part of the vessel is upturned like that used for Harrier jump-jet fighter bombers.

Can helicopters lift more weight using the ski-jump principle like Harriers?

[John Farley]

Centaurus

I suspect the ship you mention is the one previously used by the Spanish navy to fly their Harriers (Matadors to them). They used the ski-jump for all the usual Harrier reasons.

As to choppers I am no expert but they can lift more with a rolling takeoff due to translational lift from the rotor disk. Goodness knows whether all the issues of hitting 2-3 g on the ramp just to gain a bit of free time in the air while they accelerate to flying speed would be worth while I can't say but if asked for my best guess I would say a resounding no. The advantages of a ski-jump are totally dependent on being able to accelerate rapidly off the end (.7g ish - the more the better) Does not sound helicopter stuff to me.

[mike-wsm]

Melbourne's skipper may have saved a lot of money by not using tugs. They seem to charge by level of service. One regular arrival would throw a line to the dockside but never to the attendant tug. Sometimes he would let the tug nose him in by pushing with its bow, and other times he would refuse all contact, getting the tug to come up to him stern first and open up, blowing him sideways with propwash. Fine judgement required.

[mike-wsm]

Centaurus - Perhaps they were thinking ahead and making it versatile?


ps - MoD types - sorry to use terms like 'thinking ahead' and 'versatile' - alien to your culture I guess

[Centaurus]

I suspect the ship you mention is the one previously used by the Spanish navy to fly their Harriers (Matadors to them). They used the ski-jump for all the usual Harrier reasons.


Thanks for the info, John F. and others.:ok:

Cent.

[asc12]

The late Neptunus Lex had a first-hand account from CAPT Gray, the CO of the squadron whose Skyraiders were supposed to help the tugs get Essex in to port at Yokosuka.

The Bridges of Toko-ri « Neptunus Lex (http://www.neptunuslex.com/2005/12/05/the-bridges-of-toko-ri/)

[Dan Winterland]

''then you could put money on the fact that the Fisheads would have piled on a bit more speed to ensure they were cloaked in fog ready for your recovery''.


Which is why the USN insists it's carrier Captains are pilots.