Helicopter landing on ship

A bit confusing so I'll give it my best shot. When the helicopter matches speed with the ship, it has to accelerate or slow down. The helicopter then has inertia, and its engine is then only over coming resistance to air flow. So when the helicopter touches the deck and applies the breaks, and shuts down the engine, it will only react to the air flow acting on it, which the breaks should handle.

I hope thats right regards JD.

The helicopter isn't the one that adjusts to the ship.

It's the ships responsibility to adjust it's course and speed to create the right winds across the deck as required by the helicopter, which is requested by the helo pilot when inbound for landing.

The ship has to adjust course and speed in relation to the winds actual course and speed.

No not really. It most cases, ship relay the speed and wind direction to the helicopter. It is up to the pilot to fly the approach and landing to suit the existing conditions. The pilot in command is responsible for the safe operation of the helicopter and may request the ship come to a more suitable speed and course but if it is not tactically sound for the ship, the pilot must adjust and fly the approach that offers the most effective and safest landing given the conditions........

I dealt with CH-46 and SH-3's and 2's primarily.

CH-46's it didn't matter what course and speed the ship was going they were able land, so your statement is correct in that matter.

However for the smaller helicopters like the SH-2 is influenced by wind conditions. Being concerned for the safety of the helicopter and the ship, they request relative winds to be such so they don't get pushed into the superstructure of the ship and the ship will comply with the pilot as much as possible.

Yes such things as having to ride troughs of the waves during rough seas is a factor that can alter that but then during rough seas, helicopter transit was kept to an absolute minimum.

On an Air Craft Carrier it didn't matter for a helicopter because they have a lot of room to land, but on a small ship like the Destroyers and Cruisers, where the landing area is located at the fantail, you have superstructure close to where the helo is landing. Some have the landing pad on top and even then you still have the ships mast to contend with.

A land-based observer will see both ship an helo moving at 50 kts while the bird is in the hover and also when secured to the deck.

once,the relative speed between the helo& navy ship is zero

the touch could be smoosly

The helicopter's propulsion is on the rotor, not on it's wheels. As soon as the helicopter touches the deck it still has to compensate for the ship's speed to stay on the deck, until the helicopter has been secured to the deck. Compare it with an airplane standing with it's nose into a very strond wind. Without throttle it will go backward, but to keep it in one place, or groundspeed zero, the pilot must apply some throttle. Same with the helicopter on the ship's flightdeck. The flightdeck becomes the steady object at the moment the heli touches down, but there is a lot of headwind. So if the ship is sailing in the direction of the wind, the airspeed of the helicopter should be even more than 50 kts.

This is Einstien theory of relative motion. Ar the moment of landing the helicopter musr be going at the same speed as the ship and in the same diecrion. It is the relative speed that counts and if this matches both are going at the same relative speed. If you walk up a train ar 5 kms per hour and the train is going 50 MPH then you are travelling at 55MPH relative to the ground. If you go backward at 5MPH then you will be travelling at 45 mph relative to the ground.

If you want to go to town then the earth is moving also so to get the actual speed you would need to take this into the calculation. & so on ad infinitum - speed is always relative.

@ Hazman:

Walking up and down a train is based on that your legs (propulsion) are in contact with the moving object (train, ship, moving walkway, etc). In the case of the helicopter, the propulsion (rotor) is not in direct contact with the moving object (when they do it will give a big mess!). As stated in earlier comments, the helicopter must, as long as it is not secured to the flightdeck, keep compensating for the headwind, in this case the ship's speed plus headwind. When you stop walking in the train, you will still travel with the train, with the same speed as the train, but when you stop the helicopter as soon it touches down on the flightdeck, it will most probably roll of the stern of the ship.

Daft reply! has nothing to do with contact - there can be moments, when running when both feet are of the ground, the speed is still the speed and relative to the some other object. The rotors are in contact with the air or they would not be working. If you want to get really complicated try and work out the speed of the rotor tips in relation to the ship!

Try landing a (wheeled) helicopter on your train and next try jumping onto the running train. When you cut the power to the helicopter's rotors, it will roll off, because of the headwind. When you jump onto the train (from running or whatever) and stop running as soon as you will step on the floor of the train, you will stop and continue moving with the same speed of the train. Because the helicopter does not use the ship as it's surface to move itself, this is different than walking in or on a train!

Ummmm,

No offense meant, but not the best analogy in the world. While helicopters use their rotors for movement, wheeled helicopters do have brakes and wheel steering, and can ground taxi much like a vehicle with driven axles. Skid helicopters do hover taxi'ing.

That said, I would not like to be in a helicopter trying to self maneuver on a steel plated ship with a wind blowing over the deck at 50 kts. With steel plating as slick as greased goose sh*t, I would much rather the pilot maneuver from a hover under those conditions.

Hooker

Hold on a moment! What's the problem here? The boat's velocity is 50 mph in direction X relative to let's say some fixed point Y, the helo's velocity is 50 mph in direction X relative to the same point Y, hence their relative velocity to each other is 0. Obviously, both are at the same coordinate relative to point Y.

What's the problem here?

Now, let's go on to the old problem of the folks in the free falling elevator. If they all jump up 6 inches just before impact, are they safe??

I know, I know, this has been beaten to death before, but I just had to bring it up due to the nature of the question.

Where's Vermin when you need him?

John

It's not that simple.

One person has explained the how that helo is landed on the deck. I've explained why the ship would be doing 50 knots in the first place.

Just because a ship is traveling at 20 knots on what ever course they are on doesn't mean the helo can just approach on that same course and land on the deck at that speed.

What if that helo has a a tail wind forcing it forward and added 15 knots, there is the risk of being pushed into the ship's superstructure.

A ship travels at a certain course and speed to obtain the desired winds that cross over the ship. This is to prevent the helo from going into the superstructure.

Speed is relative, even if the helo has landed on the ship, it is STILL travelling at 50 knots although it may look like it's travelling at 0 knots when we use the ship as reference point.

I think landing a chopper on a ship is easier than driving and "parking" a car inside a moving van. The car needs a braking distance because once the rear tires (assuming it's a rear wheel drive based on the old tv series "Knight Rider" hehe) touches the ramp, the reference speed would be transferred on to the ramp.

The helicopter's speed to the ship is 0 relative.

What matters to the helicopter is the apparent wind speed across the ship's deck for landing.

The ship has to alter it's course to the course and speed that the helicopter requires for landing.

This is directly influenced by the true wind. The helicopter might require the winds to be 30 degrees across the deck at 30 nautical miles per hour called desired winds. The ship's course and speed might be heading into the winds that are at 20 nautical mph so the ship has to increase speed and alter course a little achieve the desired winds across the deck.

The ship computes relative winds, which is what the winds are doing in relation to the ships course and speed. With a maneuvering board the ship factors out the ship's course and speed to produce the true winds. With the same maneuvering board they compute what the ship needs to do to created the desired winds across the deck.

Hi ronseto:

If you were on the bed of a flatbed truck traveling 30 Km/h and you were passing a flatbed truck traveling 10 Km/h likely you would not try to traverse the distance between the vehicles. The difference in relative velocities is 20 Km/h.

Now if your truck matched speed with a third truck traveling at 30 Km/h and a ramp (assume guard rails and any other safety devices required) was placed between the vehicles you could easily traverse the distance. The difference in relative velocities is 0 Km/h.

Perhaps you confusion comes into play if the ramp were say, lowered to the ground and a car intended to drive up the ramp he would match velocities with the truck so far OK (the difference in relative velocities is 0 Km/h) but when the drive wheels of the car touch the ramp which is traveling with your truck the car would attempt to instantly accelerate to 30 Km/h velocity relative to your truck.

Hope this clears up your confusion.

mechtech

Uh, no, the helicopter pilot is still flying the helicopter at 50 kts forward airspeed and the pilot must maintain flying control until the helicopter is locked to the deck and the rotor is stopped. Of course, I am presuming the 50 kt headwind because of the ship's forward speed. If the windspeed was lower, say 10 kts, the pilot could be less concerned, but is still responsible for maintaining the helicopter under control until the rotors are fully stopped.

There are ALWAYS hands on the controls and ready to respond while the rotors are turning.

Hooker

It's easy to see Hooker is right if you imagine the bird flying 0.00001" above the deck at 0 velocity wrt the ship. (I know this isn't really possible but imagine). Now, three swabbies run out (crap, watch that rotor!), OK two swabbies attach cables to the undercarriage and the pilot drops power. The heli drops 0.00001" (no pain) and the jerk from the ship taking up the extra load is spread over the time the rotor slows.

Very simply, you are talking about Va - Vb where (a) is the helicopter and (b) is the ship. You can also reverse the formula with the same result, that being Vb (50knts) - Va (50knts) = relative velocity or zero. There is one significant contingent to keep in mind with this, however, that being the vector. The forumula assumes this factor is the same for both objects - in other words, the chopper is headed in exactly the same direction of the ship. If this were not the case, the clip you viewed would have likely been aired on 'What Were You Thinking'!

Immediately before it touched down, if it was indeed matching the ship's speed of 50 knots, it had already achieved 0knots relative to the ships speed.

Once it touches down, the helo is maintaining its new 50 kts 'ground' speed from two sources. If it maintains the same exact position on the deck, the speed relationship of the landing gear to the deck is zero (or else if there was a difference it would move upon the deck). Two sources of maintaining zero relative difference are: Itself, (still flying) and coefficient of friction between the components touching the ship. The ship it transferring its speed to the helo like a car transfers speed to your body. But you are restrained in the car by the seat back and the seat bottom grabbing your pants, your pants grabbing your body, and the seat back not allowing any slippage to go past that point.

The helo can only 'grab' the ship by the friction of touching components, yet the blast of wind from the moving ship requires the helo to still fly forward or it will slide off the back. So if the ship grabs it by 15%, the helo must now fly 85% power forward until such time as the ships crew secures it to the deck to where it gets 100% forward speed from these restraints, like the seat and seat back in your car.

Experiment: Get two people. Fold a piece of 2" x 2" (5 cm x 5 cm) paper in half and stand it up on your kitchen table (helo). Have a friend blow it across the table gently with the wide section towards your friend. Remember the blowing effort. Now put that small paper (helo) on a large paper (ship) and pull it slowly across your table with the wide section pointed into 'the wind'. Maybe it stayed put since the friction of contact could overcome the mild wind resistance. Now pull it across faster until it starts to move backwards. Remember this speed of the large paper (ship) causing the small one (helo) to move backward. Now while pulling the large paper have your friend blow behind the small paper like they did before when they were moving the paper along the table without your assistance pulling it. The blowing is similar to the helo 'flying' and you pulling the paper is the ship speed. Much less effort of blowing is required to keep the paper stationary while you pull it along. If you match the blowing and pulling so that it doesn't move, you have zero relative speed (it didn't move) but your friend must still blow (fly) the paper along also. If you glued the small paper to the big one (chained the helo to the deck) you do not need your friend to blow (fly) it now. You would need great speed of the large paper to break the glue joint from wind resistance acting on the small paper. The glue increased the coefficient of friction of the helo to the deck.

If this isn't clear, ask my ex-wife as she knows everything !

Cheers !

"The helo can only 'grab' the ship by the friction of touching components, yet the blast of wind from the moving ship requires the helo to still fly forward or it will slide off the back."

One small observation, if I may. While on the deck with the rotors turning, it is most likely that the pilot will apply full negative pitch while the aircraft is being secured to the deck. This gives more "adherance" than just tire contact and aircraft weight would provide while it's being tied down.

Also, most shipboard helicopters will not be shut down until they are tied down because helicopters have a tendency to rock and roll while the blades spin down. On a slippery deck the aircraft can move around quite a lot if not restrained.

Hooker

"While on the deck with the rotors turning, it is most likely that the pilot will apply full negative pitch while the aircraft is being secured to the deck."

What kind of force / vacuum would this develop beneath the rotors? How would that affect personel trying to secure the ship? Just curious from an aerodynamics standpoint,,, never been present to see a chopper land on a navy helo pad...

It wouldn't be a force that would be particularly noticeable to anyone around the helicopter, certainly not like the blast from a hovering helicopter. But it would help "glue" the helicopter down.

The negative pitch is only a couple of degrees (depending on the model) and its real intent is to allow rotor rpm to build up during an autorotation (simulated engine failure).

Hooker

Thanks. Great 'extra info'. Just trying to keep it simple for general audiences. In my paper example was I going to continue with 'Now place a small weight on the folded paper until it is flat upon the big paper . . . . " but it was getting too complex and needing drawings.

BTW, I take helos (we say Hee-Lows) to work about 10-12 times a year (oil biz) and I've never asked why we have rope netting on the helidecks of offshore platforms. I had supposed this is to give some footing (friction) for the helo, the boxes, luggage, & people since the decks are made of grating to pass rain water and do not provide any friction for boxes and such, but, rubber helo tires deforming into grating sections should 'stick' better than across 1-2 large 20 mm rope section nets + grating. maybe the netting has another more technical purpose.

The wind shear and drafts on platforms makes landing interesting and VERY dicy. We add 'modules' when we upgrade platforms, like builing blocks stacking up here and there. Vortexes, channels, velocities, directional cahnges . . . . its all there ! I've stepped out from behind a module on an upper deck into a full wind and my parka became a sail and I had to 'slide into third base' to catch the 4" kick board to avoid bellying over the rail and into some 3 minute survival ice water

I've never been on an oil platform but from driving motorcycles across similar steel grate bridges I can imagine why the rope is there. It wouldn't be hard to imagine a body getting blown around by unexpected rotor wash and/or wind gusts, and scrambling to grab onto anything available.

Do you also have the safety nets draped around the sides of the landing platform like they have on navy ships that handle aircraft? Those nets are designed to catch wayward bodies that would otherwise go completely overboard.

Hooker

No 'boarding' nets like you have on ships to catch, or roll out upon demand, for boarding. If you fall over, the fall is 100-150 feet so you are likely toast from water impact, or frozen in 2 minutes in North Sea or Russia (where I was). Ever since Piper Alpha (Google it) all offshore platforms has a support vessel circling 100% of the time about half a click out. That is still several minutes away from 'man over board'. The rule is, if you fall, you are toast due to 3-4 things against you. Lace up boots (required for ankle support on the hundreds of stair cases you climb), cold water, the fall itself, panic, ice blocks (Russia, not North Sea), smashing up against platform legs, etc.

I recall the device as it was also used by the U.S. Navy. I think it was called "DASH".

It was a neat idea as long as the ship was in relatively calm seas, when it really wasn't needed.

Imagine a relatively fragile helicopter tethered to a pitching and rolling ship in a rough sea. Imagine that the ship is pitching 10 or 12 feet or more at the winch. Imagine the effect at the other end of the line. There is no way to adequately control a wildly pitching helicopter, presuming the anchoring structure isn't torn out in the meantime.

What is described is the Canadian Navy's Beartrap retrieval system. It was actually used for quite a long while, but only with relatively new helicopters with the best flight crews.

BTW, DASH was an unmanned armed anti-submarine helicopter designed to be launched and recovered from destroyers. DASH is still flying today. See Wikipedia.

Hooker

I was about to make the same comment about the tether line.

I served on Navy ships for 11 years as an Operation Specialist. Part of the job of the rate I worked in was controlling helicopters for anti submarine warfare and for underway replenisment using helos and for helo transiting.

Now the original question was how can a helo land on a ship at 50 Nautical miles per hour. Everything is Nautical at sea and a nautical mile is = to approximately 1.15 statute miles.

With the duel rotar helos, they pretty much made their own wind and can land on a ship no matter what the winds were across the deck, but for your smaller helos the winds played a critical role. The general rule of thumb is to bring the winds across the bow at 30 Nautical mph at 30 degrees. That means if the ship is heading 000 degress true, that relative winds were supposed to be from 030 degrees at 30 knots. This changes a little from each type of helo but not much and the pilot will radio ahead and give the desired winds and the ship will adjust course and speed to accommodate.

The large Navy ships like the Auxilleries cannot do 50 knots even with a tail wind. Many can only do about 17 knots and with the AOE's that were made to keep up with a Carrier Battle Group at high speed can do 27 knots.

The destroyers and new cruisers can do 50 knots or better. The reason for that ship to be doing 50 knots is because of special instructions from the captain to maintain a certain course as much as possible and that meant that high speeds were necessary to get the desired winds across the deck.

Military ships are required to hold a specific station when in transit and failure to hold that station meant a reprimand from the battle group commander.

They don't care about the reason why you couldn't hold station. They only care about you holding station so the Captain sets the parameters on what he wants to do in order to make this helo landing as quickly and smoothly as possible and keep the battle group commander off his case.

Heli landing gear have brakes,correct?

Navy ship at with copter pad at 50 knots?? Wow!

I mean, that's 57.5 (statute) miles per hour...by a naval ship big enough to "land" helicopters? Do they even make catamaran "copter tenders" that fast?

Most of your Naval ships are capable of landing a helo.

Some of your Destroyers have a hangor for a helo and have a helo assigned to them.

Well, ya. if you have a ship that can do, say, 25 kts., steaming into a 25 kts. headwind, that is entirely possibly.

But that entirely changes the OP question...but maybe that's just the answer looked for?

I take your post to actually mean a copter (not the ship) at 25-kt ground speed (25-kt air speed relative to a 50-kt [gale-force] headwind) pursuing a ship going forward-full into wind and seas...at which point copter is dropping to touchdown, hovering over a relatively stationary landing pad; but also over a significantly pitching, possibly pooped, ship's fan tail.

On the other hand, for a 25-kt-capable. submerged keel (non-catamaran) naval surface ship to make 50 kt ground speed equivalent (in any seas) would require following, 25-kt+, seas (i.e. current)...and that sufficient to also overcome ship's head wind; to my limited knowledge, no open-sea ocean current progresses at that rate.

Or, did I miss something?

No, you're naval destroyers and new cruisers are capable of doing over 50kts without being a catarmaran.

LCS : cruiser, destroyer, or something else?

Well, I see now that shallow-draft LCS can achieve the speed in a sprint and with just-so seas and weather; but normally in mid 40's for sprint, and mid-30's for max-fuel-efficiency cruise and range. And they (the few of them) do come with heli-pads and hangars astern.

"Aircraft Launch and Recovery Up to Sea State 5" (when copters can operate) is specified for the vessels...anyone know how "Sea State 5" is defined?

They are shallow draft hull: one a Trimaran (fundamentally based on vehicle ferry barge); the other a modified planing hull. As suggested by the name, the small-complement vessels are missioned for coastal and "up-inlet" operation...not ocean going/deep-water....like D's and C's.

As to class, I'll need to search a specific vessel to see its designation...if destroyer- or cruiser-class.

If you know of or can provide link to a cruiser-/destroyer-class hull which would make or approach the 50-kt grade, that would be a boon.

Here's more background on the Littoral Combat Ship...you might recall all of the controversy surrounding these build contracts several years back.

Thanks for your helpful input.

This from the USN site... Searches for "50 knot" returned no results.

Arleigh Burke-class destroyer — (DDG)

Touted as the most powerful surface combatant ever put to sea, the Arleigh Burke-class destroyer was named after the Navy's most famous destroyer-squadron combat commander and three time Chief of Naval Operations. This class features combat systems centered on the AEGIS weapons system and SPY-1D multi-function radar. Arleigh Burke-class warfare capabilities include the MK41 Vertical Launch System (VLS), antisubmarine capabilities, advanced antiair warfare missiles and the long-range and accurate Tomahawk cruise missile. Designed for survivability, these vessels incorporate all-steel construction and numerous damage-control features. These 500-foot-long destroyers use gas-turbine propulsion to cut through the sea in excess of 30 knots, which equals close to 35 mph.

Yes, the first of that class was just launched as I was getting out of the Navy.

Understand that top speed of all Naval ships is classified. You will not see the actual top speed of a ship printed in Jane's Bood of fighting ships.

Below is "sea state 5" - in reference to conditions (Beaufort scale) above which (LCS) (unassisted?) launch & landing operations would not normally be conducted.

How it can be interpreted, if at all, in terms of the OP question is unclear; but it seems reasonable that "wind" speed imparted by ship's progress could be seen as a limiting factor: one calling either for use of backup/emergency retrieval-system measures previously mentioned, or for curtailment of operations.

For instance, regarding an hypothetical landing on an hypothetical (planing, plowing, or cutting) craft, ship's forward progress at, say, 35-kt on calm seas would impose 35 knot head wind on a (as per OP, pursuing) copter "come to" at hover. While this "excessive wind speed" is not accompanied by "Cat 5" Beaufort sea conditions (the full sea state) at which unassisted landing would be "against the manual," at some ship's speed the simulated "sea" conditions (due to planing & bounding, rising and plowing, ...) would (also) approximate operating conditions exceeding "safe state 5."

At that point the question (it seems) becomes one of: what are the sea-state limitations of the (previously described) auxiliary, ship assist landing systems (Anyone?) ... the conditions beyond which (because ship retrieval systems are no longer available) the aircraft must be abandoned to its fate (rather than threaten the ship) in hopeful prospect of later rescue/recovery. Absent countervailing air/sea factors, the 50-kt ship hypothesis seems to fall outside of safe-landing parameters above which a landing attempt becomes an extremely risky proposition.

In these regards, and whether intended as such or not, the OP question, indeed, seems to have been a loaded question.

Simple: It was going (hovering) at zero (all horizontal directions) relative to ship's progress - to ship's speed relative to seas - even before touch down. If not...problems! Airship hover is always in relation to potential landing site, irrespective of forward, sideward, or backward airship velocity.

Biggest problem is vertical velelocity...to match ship and copter rise and fall rates.

By definition, in order to land, which means go at a relative speed w/r to the ship of 0 (no relative motion), the helo needs to match the speed of the ship such that his relative speed w/r to the ship is approaching 0. In reality while he is manueuvering to land he would be +- the speed of the ship, while at the moment he sits on the ship his relative speed w/r to the ship has to be 0, otherwise it would keep on moving. Also, at that moment the helo assumes the speed of the ship at 50 knots.

What's to explain? All motion is relative. All you did was change the reference point.

Guest---A nautical mile is 1.15 statute miles.

Invert the question--If the helo is sitting on the deck of a ship moving at 50 Kts. how fast is the helo moving?

Then if the helo winds up to take off vertically--I suspect the velocity would be exponetial and it would decelerate from 50 kts. to zero at some rate, but not instantaneously(unless the ship was travelling with a 50 kt. tailwind).

The Ship and Helo are each doing 50 knots independently, when they are not in touch with each other. The instant the helo touches down on the ship's deck, it shoots a device known as a harpoon into a landing grid and thus becomes integrated with the ship. Now it can shut off its engine and depend on the ship for its transportation, like any other equipment/item being carried on board the ship. The transition from its independent flight to dependent transportation has to be as instantaneous and as short a duration as possible, to avoid turbulence buffeting or destabilising effects from the superstructure of the ship.

I have put forth a concept system for concurrent operating (Launch and Recover) multiple heavy Helicopters on board Frigates called TARDAMS (acronym for The Artec Robotic Docking And Movement System), (ref.MAST Confex 2006). Here, the principles of Robotics are used to compensate ship's motion in real time and ensure a stable docking of helo with ship, devoid of any turbulence. This is designed for operations in a sea state greater than C6. Please see animation in www.artecrobotics.com

How much does TARDAMS weigh, both above and below deck, on the frigate. Are you saying the crane will bear the full weight of the copter? What will be rotor status once docking/grappling is established?

What mods required on air ship in order to be grappled securely and stably?

What mods on frigate? Would the crane be elevator mounted for below deck stowage?

How can frigate ship (modified or otherwise) compensate during lateral movements of copter weight at top of grappling arm?

"Greater than Sea State 6" is rather vague and broad: from near gale to cyclone/typhoon/hurricane cat-5...largely conditions in which copter would not be operating. This brings marketability into question?

As to funding of development and build (assuming what your seeking is such a contract)...

US DOD and its client state navy ships are fitted with a retractable crane for handling and stowage on board. Development and testing of their "manipulator" was a very protracted, very costly affair. So it seems that any prospective buyer would be very concerned with the risk-benefit of TARDAMS before investing...

And, it looks very hairy and scary for both ships and both crews.

How much does TARDAMS weigh, both above and below deck, on the frigate.

May I presume you have visited the website www.artecrobotics.com and seen the animation?Approximately 1.75 tonnes each, made of composites and honeycomb (spaceframe) stiffening. It is mounted on deck inside a special armoured stealth sliding door protected side hangar (please see animated sliding door in the Products section)and the Helo is serviced, secured on TARDAMS. I am working on a translation system which can handle the helo for below deck stowage.

Are you saying the crane will bear the full weight of the copter?

Yes ,static as well as dynamic loading arising when helo is docked with the ship in Zig Zag evasive action modes,if being chased or to avoid torpedoes or any other battle contingencies even while operating as a squadron.

What will be rotor status once docking/grappling is established?

Engine can be turned off safely unless- required to standby for a "fly-off" command.

What mods required on air ship in order to be grappled securely and stably?

Keep station with ship, for a maximum duration of 2-3 minutes.

What mods on frigate?

Frigate can maneouvre independently regardless of helos need to land or take-off,,besides disregarding wind directions/changes/gusting..The very idea of "Docking" operation is to take the "Load" off the Helo Pilot/crew.

Would the crane be elevator mounted for below deck stowage? A modified version can be combined with transfer mechanisms operable under even seismic conditions or missile impact/undex.

How can frigate ship (modified or otherwise) compensate during lateral movements of copter weight at top of grappling arm?

Shock absorbtion and dissipation is built into the TARDAMS for multiple combinations of degrees of freedom.Besides, being a dynamically controlled arm, it always seeks to assume optimal kinematic configuration, through sensing and realtime command and control-as a basic Robotic system.

"Greater than Sea State 6" is rather vague and broad: from near gale to cyclone/typhoon/hurricane cat-5...largely conditions in which copter would not be operating.

Copters will not be operating by choice in foul weather.TARDAMS takes into account a force of circumstances when in the midst of operations, there is a rapid change of weather and battle conditions/opportunities dictate staying on and continue engagement with the hostile forces. Let's see who blinks first.

This brings marketability into question?

On building a technology demonstrator prototype and with the co-operation of a potential customer (Navy) for sea trials, marketability will be a non-issue like how Airbus A380s are being sold in 100s.

As to funding of development and build (assuming what your seeking is such a contract)...

US DOD and its client state navy ships are fitted with a retractable crane for handling and stowage on board. Development and testing of their "manipulator" was a very protracted, very costly affair. So it seems that any prospective buyer would be very concerned with the risk-benefit of TARDAMS before investing...

Rightly so,but this has been overcome by my interactions with the largest manufacturer of LCS for the Deep-water program-now come to a (hopefully temporary) halt.They wanted it COTS.

If funded for India-based (with International co-operation and best of EPC) development,the whole thing will be at a fraction of cost in developed countries and also the time frame can be within 21-24 months as per my PERT/CPM projections.

And, it looks very hairy and scary for both ships and both crews.

Any first- of- its- kind has to overcome human inhibitions-quite naturally.If looked at from a pro-active mode, the advantages give a Force exponentiation, even to very poor navies, at a very low cost.

As someone who has several thousand combat helicopter hours as a crewmember, I find your idea intriguing... and scary.

A couple more question, if you don't mind:

1) I understand how you can keep your "grapple" stable relative to ships movement using well proven stabilization systems, but how do you account for helicopter movement, both pilot and environment induced, especially in less than ideal wind/turbulence conditions?

2) I would be most interested in seeing the details of your helicopter restraint. I don't see anyway a grappling system could work with standard military helicopters without fairly massive modifications to the airframes. Certainly the standard landing gear and tie-down equipment wouldn't be adequate for capture on their own. Structural mods I envision would be expensive and possibly detrimental to mission objectives laid down during helicopter conceptual design.

3) Lastly, rotor blade restraint while spooling down or even with a rotor brake applied, especially in gusting wind conditions, is always fraught with danger, both to crews and equipment. How do you address this area of concern while transitioning the aircraft from flight to deck in ever changing wind vector/speed/gust conditions?

Thanks. I'm trying not to be negative about your system but frankly it would scare me to death to be on that aircraft in even excellent weather conditions, much less moderate to poor. And please don't think I have typical "human inhibitions". I was the crew chief onboard the first ever fully automated (ground computer controlled) flight of a helicopter, a NASA CH-47.

Thanks for listening.

Hooker

I am indeed honored to have gotten the attention of a veteran to TARDAMS.I presume you have seen the animation available on www.artecrobotics.com.

I have also had the privelege of presenting a Paper (by invitation) titled "Retrofitting the TARDAMS" at MAST Confex 2006 and had detailed interaction with the Chairman of the session- a highly experienced Sea King Pilot of the French Navy besides senior Naval/Maritime experts of the Navies from the world over and R&D engineers of the Office of Naval Research, US Navy.More than 90 helo pilots of the Indian Navy / Coast Guard have also been given a half day long interactive session with me and they were enthused enough to recommend the system to the Chief of Naval Staff, Indian Navy, for further progression and presently it is awaiting fund allocation.

As the questions you have are the very essence of what I'll be doing for detailing for the manufacture of the prototype, it could prejudice my potential for obtaining patents, I may please be excused for giving somewhat sketchy details.

"...but how do you account for helicopter movement, both pilot and environment induced, especially in less than ideal wind/turbulence conditions?"

Here, we have to go outside the conventional practices and look at the Earth/Moon orbital system wherein a virtual point (in space) becomes part of the control algorithm. The Helo and ship are the two elements being subjected to the environment albeit differently and have a constantly changing virtual point of reference in the Air/Sea space.Here is where Robotics comes in with real time computations of instant locations of Helo, Ship and the "Manipulator" arm wrt Virtual point of reference in the Air/Sea scenario.The DOCKING operation also depends on the sensing of the physical proximity of Helo and its dynamic behaviour. The Control system establishes a set of characteristic curves in the various DOF of the helo and is able to predict where the helo will be over a time frame of 30 seconds. based on this the end -of-arm system is both positioned and oriented continuously and appropriate to receiving the Helo into the "Gripper" securing system.

2) I would be most interested in seeing the details of your helicopter ...during helicopter conceptual design.

Details will have to await commercial considerations of the prototype developer, however, for your information, TARDAMS presents a normal decklike platform complete with Grid for harpoon operation and so there is no issue of structural considerations of the helo. There will be a soft gripping force on the fuselage not exceeding what a human (female) hand or lips can impose (a kissing touch).

3) "Lastly, rotor blade restraint ...."

As explained above, since the landing is as normal (with TARDAMS assistance) as on a calm deck, it is pilot's and handling crew discretion and co-ordination wrt rotor blade securing sequence.

The only way to overcome our fears is to confront them and work on unexpected problems as they arise. I am sure with experienced persons like you around, realisation of TARDAMS will not be beyond reach.

Please feel free to shoot more questions and I will do my best to reveal as much is permissible within "commercial" safety.

Thank you...and compliments for your responsiveness.

An interesting thought..................I actually lost count of the number of helicopter and fixed wing aircraft landings that I have witnessed............I served on the aircraft carrier HMAS Melbourne for three years, nearly 2 of which I was working on the arrestor gear.

I do not wish to comment further on how this is achieved.........it has been done to death.

One comment I would like to make is that mostly things work out quite OK............but, sometimes things do go wrong.............horribly wrong. Sometimes mechanical damage but, more often pilot error.............although reasons may remain a mystery, as not too many pilots survive.............I personally feel complacency may be a problem or bravado (cowboys). Here is an example that involved a Blackhawk.

Above shows point of impact

The pilot and an SAS soldier died.

Fortunately it does not occur too often. It is not unusual for carriers to loose one or two fixed wing aircraft and helicopters on a six to nine month tour of duty (in peace time)