By

 Steve George BSc MSc CEng FRAeS Cdr RN

You can download this paper  here as PDF file.

 

Executive Summary

 

  1. This essay examines the requirements of generating combat aircraft capability from a base. It then compares the challenges of doing so from an aircraft carrier against an airfield, and the advantages to be gained from meeting the ‘carrier challenge’.
  2. After a short history of the development of ‘cat and trap’ technology, the mechanics of launching and recovering aircraft from an aircraft carrier are described, showing how training and expertise overcome the potential hazards to deliver combat air power from the sea. It also describes how more general aircraft operations differ on board a carrier.  It then offers a brief analysis of the ways in which carrier operations affect aircraft design, and presents a set of conclusions on the ownership of naval aviation.
  3. It does not address the operational arguments for the aircraft carrier, but complements the Phoenix Think Tank papers that will do so.

 

Introduction

 

 

In the current discussions over ownership and operation of a maritime fixed wing strike capability it has become apparent that, in some quarters, there is a lack of knowledge of how this capability is delivered. This has led to senior officers describing aircraft carriers as ‘floating airfields’ that offer ‘a useful alternative basing option’ for aircraft normally operated from land bases. Such statements imply that aircraft operate from a ship in essentially the same way as they do from an airfield. They don’t, and this essay will show how they differ.
This essay will show that operating aircraft from aircraft carriers involves entirely different techniques, disciplines and skill sets, from those ashore, that come together to deliver highly effective combat capability. And this capability is potent, flexible and, importantly in today’s society, safe. Not a single aircraft carrier has been damaged by enemy action since WW2 despite their being used in a vast range of operations. It is not generally appreciated that aircraft carriers are a main source of US close air support in Afghanistan.
There are important issues around the appreciation of air power that have always influenced the arguments about carrier aviation. Pure ‘air power’ proponents see combat aircraft as an independent and uniquely potent way of applying military coercive force through the medium of the air, rather than by land or sea. However, naval aviators see maritime air power as another (albeit hugely important) capability available to a naval task force commander. To them, an aircraft is a means of finding targets and delivering weapons at longer range than their shipboard sensors, missile systems or guns.  Maritime air power is integrated with the other weapon systems in the task force, such as anti aircraft missiles on destroyers, and the torpedoes and cruise missiles that can be delivered by submarines. At the command level, it is employed at sea in much the same way as other ship-borne weapons, its use influenced by weather, sea-state and depth of water.

 

Both of these arguments can be, and have been, powerfully argued. This essay does not attempt to compare their validity. Rather, it describes the essential differences in the way that integrated naval ‘air power’ is developed and delivered from a ship.

 

Delivering combat air power from a ship confers advantages of flexibility and the ability to position aircraft closer to the desired targets, thus increasing ‘combat mass’. But doing so requires a complete integration of the air group and the ship. To operate any ship-borne weapon satisfactorily requires the command to have a thorough knowledge of its and his ship’s requirements and limitations.  It is, therefore, part and parcel of that ship’s capability and it is the Captain’s responsibility to train his crew and achieve the highest possible standard of operational efficiency. And that includes his Air Group.

 

Generating Combat Aircraft Capability

 

 

Whether combat air power is generated on land or at sea, it must be effective, sustainable and reliable. It must deliver these qualities under the widest possible range of conditions, on demand over extended periods. Finally, and especially importantly, it must be acceptably safe to those who operate it and work around it[1].
Military aircraft operators appreciate the importance of safety, as combat aircraft like the F-35 Joint Strike Fighter are not especially safe on land or at sea. They carry high explosive weapons, have a wide range of powerful radio emitters and power systems that channel large amounts of energy in various forms around the aircraft. Their engines generate huge amounts of thrust, heat and noise, and they are filled with tons of flammable fuel. They have sharp edges, move around on the ground at high speed on small, skinny tyres, and their jet intakes can drag in a person from many feet away. They weigh tens of tons, and when shut down can only be moved with great care using special equipment.[2]  They are also extremely expensive – but essential to deliver the military capabilities that are required.

 

Delivering air combat capability is complicated from a land base. Doing it from an aircraft carrier is one of the most difficult challenges ever faced by armed forces. However, it can be done, and when done properly it delivers massively efficient air power.  Developing this expertise has taken hard work, trial and error, punctuated by flashes of brilliant innovation. This essay will set out the fundamental differences between land and sea based combat aircraft operations – the ‘particular mechanics’ – and show how naval aviation copes with these differences. It also aims to inform and guide on-going debates about the regeneration of the UK’s maritime strike capability. It starts with a comparison of airfield and carrier operations, gives a brief overview of the key elements of the development of modern naval aviation and then looks at the ‘particular mechanics’ in detail. It concludes with a brief analysis of the integration of aircraft with their parent ships to conduct effective operations.

 

The Airfield and the Aircraft Carrier Compared

 

 

Airfields are land bases designed to generate and sustain combat aircraft capability.  Long runways allow the aircraft to launch and recover effectively and safely. Hangars, bomb dumps, workshops, offices and accommodation allow specialist personnel to provide the many strands of support required to sustain the capability. All these activities influence the size of the airfield, but the main driver for the very large size of military airfields is safety. Physically separating the source of a hazard from the people at risk is a sure and effective way of mitigating those hazards, and on an airfield, size is safety’s friend.

Take off and landings are hazardous operations, so all other parts of the airfield are located well away from the runways. Aircraft are parked widely spaced out on the operating pans, and personnel are kept well away from running aircraft to avoid exposure to noise, intake suction and jet blast. Aircraft are kept clear of runways while other aircraft are taking off and landing, and aircraft are never taxied close to buildings, ground equipment, or other aircraft. Refuelling is controlled so as to reduce the chances of fire,[1]and weapon loading is usually carried out in specially separated areas, with final arming of aircraft carried out on special areas nearby the runways.

 

All this means that military airfields are built on a very large scale. They will normally be around 2 to 3 km across, centred on a main runway around 2 km long (10 to 11 thousand feet), surrounded by long taxiways that connect the runways and also the parking areas (pans). Where an airfield has more than one ‘pan’, they are often located at opposing sides of the airfield. Hangars and workshops are located outside the taxiways, with accommodation and administrative areas further out. Fuel ‘farms’ are located well away from runways and hangars, while weapons storage and preparation areas are set furthest out to mitigate the dangers of secondary damage from explosions. Finally, there are high power radio ‘antenna farms’ used for communications, and powerful radars – these are usually located over 3 km away.  Bases like these, when operated by the RAF, typically house no more than 40 aircraft.

Aircraft carriers have to contain all these facilities onboard, and so it is often assumed that they are enormous objects. Indeed, the term ‘floating airfield’ is often used to describe them, and this is understandable. With their apparently huge flight decks, towering structures and complex fittings and equipment sprouting from their sides, they can resemble the vast ‘starships’ of science fiction. Most people, if asked to compare an aircraft carrier with an airfield, would say that they are about the same size. However, this is not the case. Figure 1 compares a ‘Forrestal’ class US Naval (USN) aircraft carrier with a typical UK airfield, in this case RAF Lossiemouth.

Figure 1 – The Aircraft Carrier – Not a Floating Airfield

The airfield completely and massively dwarfs the ship. The aircraft carrier would fit comfortably on to one of the aircraft parking areas. And yet this ship is capable of taking and operating around 70 aircraft. Nearly twice as many aircraft are based in a fraction of the space along with fuel, weapons, people, hangars, workshops and communications systems and are still operated effectively and safely.  Clearly, simply ‘downsizing’ or compressing land-based operations cannot do this. The solution is a totally different way of operating very different combat aircraft – and these differences, which lead to a totally different ‘ethos’, lie at the heart of naval aviation.

The key difference is the depth of integration between the aircraft and its base. An airfield is an essentially passive supporter of the aircraft – stores, fuel and weapons are delivered to various separated areas to support missions, and the very long runways offer no more than a hard smooth surface to run along on. On board a carrier, the operation of aircraft has to be actively merged with the operation of the ship and its specialist systems, with the result that the aircraft completely depend on the ship to deliver combat capability. This is the central feature of naval aviation, and it leads to a different ‘world’, in which most of the basic tenets and assumptions of land based operation have to be discarded and replaced with different equipment and ways of operating.
The most obvious element of this ‘world’ is the necessity to replace conventional take off and landing methods with completely different ways of launching and recovering aircraft using catapults and arresting gear – often described as ‘cat and trap’, or by the less elegant acronym CATOBAR (CATapult Operation, Barrier Arrested Recovery). As will become clear, these techniques are complemented by a less obvious, but no less vital, culture of ‘naval aviation’ that successfully delivers combat power effectively, reliably, sustainably and safely. This culture drives the organisation and processes of the Royal Navy’s (RN’s) Fleet Air Arm (FAA).

 

The Development of the Modern ‘Cat and Trap’ Aircraft Carrier

 

 

From the first days of naval aviation, it was realized that launching an aircraft from a ship might need catapult assistance. Hydraulic catapults were developed by the 1930s, but the ability of WW2 propeller driven aircraft to take off without them made their use relatively rare[4]. However, jet aircraft with higher take-off speeds arrived in the late 1940s and these needed catapults[5]. As the aircraft grew ever larger, the hydraulic systems struggled to cope, and catapult power (or the lack thereof) became a major issue.

 

Getting the aircraft safely back on to the ship was an even bigger challenge. Many arresting hook and wire layouts were considered, and it took a significant amount of research (and trial and error) by the RN and the USN over many years to develop hydraulic arresting machines, wires and hooks on the aircraft that could catch an aircraft and bring it to a halt in a few hundred feet. However, these developments were not enough. By the early 1950s USN aircrew were being killed at a rate that was described at the time as ‘carnage’[6]. The main cause was landing accidents while trying to land jet aircraft. Too often, aircraft missed the wires and ran into other aircraft parked on deck, broke the wires and ran over the side, or flew into the end of the flight deck (the ‘round down’) or the ‘island’.

Figure 2 – Early USN Jet Carrier LandingsFigure 2 – Early USN Jet Carrier Landings

 

 

The reason was that the aircraft carriers were no longer viable. Their WW2 style straight decks mimicked an airfield runway, with fatal consequences.  Landing jets that missed the wires had to be caught by a steel barrier, usually suffering severe damage. But this was an unreliable solution. In many cases, aircraft jumped or broke the barrier and ran into aircraft parked forward. And this happened frequently, because jets could not catch the arresting gear with any confidence. They could not accurately ‘cut’ their engines and touch down amongst the wires in the way they had done for 35 years. Increasing the number of wires took up too much deck space on the ship. If they tried to fly more slowly, they got too close to their stalling speed[7], lost control and hit the ship or crashed into the sea. And this was with early, small jets. Larger aircraft were required to carry the atomic bomb. The USN had no way of launching these with hydraulic catapults, even if they could land them.

Frantic efforts to design huge new carriers with larger straight decks failed. The catapults were too big to fit on to the flight decks, which were being filled with more and more sets of wires to catch ever bigger and faster aircraft. After bitter wrangling between the USN and the new US Air Force[8], the cancellation in 1949 of the large carrier ‘USS United States’ signalled the potential end of USN jet aviation. In the UK, the problem of getting jets on and off the much smaller ships available to the FAA was even harder to solve. It was stated (often by USAF and RAF officers) that the age of the aircraft carrier was over, and long-range land based bombers would replace it. But the RN and the FAA saved the aircraft carrier. Between 1950 and 1953, they came up with three inventions that delivered safe and effective jet aircraft operations at sea. These were the steam catapult, the mirror landing sight and most important of all, the angled deck.

The steam catapult was a quite brilliant piece of mechanical engineering genius that allowed jets to be safely launched with a 200-foot long machine that could fit into existing and future flight decks. This reduced pressure on space at the front of the flight deck, and reduced the speeds at which the carrier had to go to generate wind over deck. The mirror landing sight, another RN invention, was a relatively simple yet ingenious device that indicated the glide slope and gave the pilot easily used information that radically increased the accuracy of his approach to the landing wires[9].

 

But it was the angled deck that made the biggest difference and allowed the full exploitation of the first two inventions. A dazzlingly bold and simple piece of FAA thinking asked the question ‘If landing along the flight deck is so dangerous, why not land across it?’ By ‘skewing’[10]the landing line across the deck at an angle, aircraft that missed the wires would be able to fly off the side of the carrier, instead of straight onwards into aircraft parked on the forward end of the flight-deck, and could safely go around and try again. This flash of brilliance created the angled deck, which effectively separated the flight deck’s launch and recovery areas. Moreover, the landing method could now be changed from the hazardous ‘cut power and flare’ to a ‘power on’ technique using no flare. This was ideal for jet aircraft and further increased landing accuracy, with the mirror landing sight providing further help.

Figure 3 – Revolution - The Straight Deck – The British ‘Skewed Deck’ - The Angled Deck

 

The angled deck, steam catapult and mirror landing sight arrived within three years of each other and quite simply revolutionised aircraft carrier design[11]. They led directly to the USN ‘super carriers’ still in service today, and also to the CVF’s flight deck design. They delivered the ability to safely and effectively operate large numbers of jet aircraft from a carrier. They remain a vivid illustration of the power of ideas, and also mark a decisive further move by naval aviators away from land based ways of flying. Most importantly, they massively increased the level of combat air power that naval aviation could deliver, a capability that remains available to most major navies today.

 

However, the invention of the new ‘cat and trap’ solutions and the angled flight decks supplied only the technology. They had to be matched by development of unique skill sets for naval aviators and carrier crews to successfully deliver aviation from a 1000-ft. long steel box instead of a 4 sq. km airfield with a 10,000 ft. runway. The next part of this essay looks at how this equipment and skill sets come together.

 

 

 

How Naval Aviation Happens – The Launch

The catapult launch seems to do no more than help the aircraft into the air from a very short runway. Apart from the amount of energy involved[12], it can look like a simple procedure. However, it is a highly complex evolution that is fundamentally different to land based launches. This section shows how the USN does it today to brilliant effect and where it differs from land based operations.

 

There is a key difference to be understood.  On airfields, an aircraft leaves the ground under the control of the pilot, and only when it can actually do so. Once the lift generated by air flowing over the wings is equal to its weight, the aircraft takes off. The pilot controls the evolution, and simple calculations allow him to check his take-off distance against runway length and adjust his weight if required[13]. The catapult launch is totally different. The pilot does not control the launch, and once the catapult is fired the aircraft leaves the ship whether it can fly or not. The pilot does not take control of the aircraft until after it has cleared the ship. In summary, a successful catapult launch depends wholly on both ship and aircraft systems working together. This success is delivered through skill, organisation and practice.

The launch procedure starts when the aircraft is signalled by a specially trained flight deck director (a ‘yellowshirt’) to move forward. It runs over a set of jet blast deflectors (JBDs), which were lowered only seconds before. As it clears the JBDs, they are raised to protect personnel and other aircraft from jet blast[14]. Next, the aircraft must be positioned on the catapult.  This requires precise steering and positioning of an aircraft weighing over 30 tons, moving under its own power, often with the deck moving about on a rough sea. Pilots cannot do this alone, and the yellowshirts therefore command and control all aircraft movements[15]. The alignment will have started as the aircraft moved over the JBDs, and continues until the aircraft hits a target guide track around two inches wide by six inches long[16].
Once positioned, a tow bar on the nose undercarriage leg of the aircraft is lowered to engage a ‘shuttle’ protruding out of the catapult track. However, the aircraft must also be attached to the ship. This is because the aircraft must be at full power to launch – flying speed is attained via a combination of engine thrust plus catapult power. The aircraft brakes cannot hold the aircraft at full thrust, so the aircraft is fitted with a ‘holdback bar’, carried in under the aircraft and clipped to the rear of the nose leg while the aircraft is moving forward on to the catapult – the other end of the bar engages in a slot in the deck[17]. Much has already happened, but there is much more to do.

 

Figure 4: Flight Deck Operations Around and Under the Aircraft

Once an aircraft starts a catapult launch, it is committed to flight – the launch cannot be aborted as on land. Therefore its ability to fly away depends on extremely complex pre-launch calculations, the results of which generate a number of settings that are applied to both aircraft and catapult. These match the weight of the aircraft (including fuel and weapons) with the correct power setting of the catapult. These calculations also depend on temperature, ship motion and especially ‘wind over deck’ or ‘WOD’. They also depend on the type of aircraft being launched, the age of the catapult (as steam catapults wear with each shot, their power drops) and any large external stores being carried. All these figures are checked and cross checked by the pilot and catapult crew, as well as other ship and squadron departments.

 

They are passed to the catapult officer and the yellowshirt launch controller on the flight deck. As the aircraft is readied for launch, deck crew positioned around the aircraft check its settings (control surfaces, engine power) and signal to the launch controller and the pilot that all are correct. The catapult crew pass the settings from their control position down to the operators in the catapult machinery space, who set the catapult and signal back that it is ready to launch. While all this is going on, the pilot spreads the aircraft’s wings (on command from the yellowshirt), and control surfaces are exercised and checked by both pilot and ground crew. But even more checks are required for a catapult launch.

 

Catapult launches can dislodge loose panels or doors, which can be ingested or blown down the flight deck, hazarding the aircraft and injuring or killing deck crews. Therefore, as the aircraft is still moving over the JBDs, technicians move around under the aircraft, checking for loose items. If the aircraft is armed, final arming checks are completed as the aircraft completes its move on to the catapult. All this activity around and under a running aircraft is utterly foreign to a land based pilot or technician, and is normally expressly forbidden on safety grounds[18]. (On RAF stations, final arming checks are always carried out on separate ‘arming pans’ located next to the runway threshold, and carried out by a separate team of ground personnel). Once cleared, the pilot sets his trim to the required settings for launch and has them checked by the ground crew.  Once all these are complete and signalled to the launch controller, he tells the pilot to set power for launch.

 

The pilot does so, conducts a final check of the engine response, puts his left hand behind the throttle, removes his right hand from the control column, signals that he is ready for launch and then rests his hand on the cockpit sill. He does so because the speed and acceleration of a catapult launch means that he is not able to reliably control the aircraft immediately after launch. Instead, he relies on the aircraft and catapult working together so that his aircraft leaves the ship and starts to climb away without control inputs. This is another major departure from land based take offs.

 

At this stage, it is worth noting that what normally happens to an aircraft alone at the end of a runway hundreds of feet from anyone or anything is now happening on a small piece of pitching, rolling and heaving steel. The noise around the aircraft is reaching around 140 decibels. (If reheat is required for launch, ground crews check that the engine nozzle petals have opened to the required setting[19]). At least 15 personnel are within 15 feet of the aircraft. Some are still under the wings. Every part of the deck is shaking and trembling with jet noise as well as the high speed of the ship. The wind will be around 30 knots and often icy cold. The JBDs are vibrating and glowing cherry red and only gallons of cold seawater stop them melting in seconds.
The launch controller sees the pilots hand signal, checks the aircraft one last time, checks that the launch area is clear, and signals to the catapult officer, located in a small control cabin set in the flight deck. Final checks of the catapult settings are carried out, and the catapult is fired. The launch controller tries to fire the catapult as the ship‘s bows lift to avoid hazarding the aircraft on a low trajectory. The holdback device breaks and the aircraft snaps forward, reaching over 140 mph in under 300 feet and two seconds. As the shuttle reaches the end of the catapult it hits a massive water brake and stops with a crash that shakes the whole ship. The aircraft’s tow bar disengages; the aircraft leaves the deck and flies away. A hugely complex and safety critical event has been successfully carried out. The entire evolution, from the time the aircraft taxied over the JBDs, will have taken around one minute. Around 20 people have been involved, and carried out a number of demanding tasks without a word being exchanged.
However, less than 2 seconds later, the deck crews rush forward, remove the spent holdback bar, and yellowshirts take position on the catapult to prepare for the next aircraft. The JBDs are coming down, and they have less than 10 seconds before the next aircraft reaches the catapult track. Behind them, another aircraft is being fired from the catapult alongside.  The benefits of this complex procedure are massive. Worked up crews can launch one aircraft per minute from each catapult, with large numbers of heavily loaded aircraft getting airborne in a very short time, with a high level of safety and reliability.
However, this is just part of the ‘carrier solution’. A few hundred feet away, aircraft are smashing into the flight deck at over 150 mph with a massive thump. They are performing the more difficult part of naval aviation – the recovery.

 

How Naval Aviation Happens – The Recovery

 

The launch illustrated an intimate linkage between the aircraft carrier and the aircraft, delivered by skilled crews working at high efficiency. Improbably, the recovery evolution is even more demanding, particularly for the pilot. Again, it appears simple at first sight. Naval aircraft are fitted with a tail hook, which is lowered as they aircraft approach the ship. The hook catches wire cables strung across the flight deck, which bring the aircraft to a stop in a successful ‘trap’. However, as for the launch, successful ‘traps’ require high skill, organisation and regular practice.

Figure 5: The ‘Trap’

The obvious challenge is getting the hook to catch one of the three wires. The end of the hook is around 20 feet below and 50 feet behind the pilot. He must bring that hook end into an imaginary ‘box’ around 30 feet long by 15 feet wide and around 4 feet high. The closing speed is around 160 mph. Failure to do so means missing the wires altogether. Left/right accuracy is vital – landing off centre could collapse the landing gear, risking collision with aircraft parked to each side of the landing area, with a separation of no more than 20 feet[20]. Up/down accuracy is vital, too. If the pilot is too low, he may collide with the ship. This target generates a precision flying task of great skill, but one that is safely and reliably delivered in all weathers.

 

 

The solution starts many miles away from the ship. During the approach to the deck, whether visual or guided by approach controllers on the ship in poor weather, the pilot lowers the hook as he selects undercarriage and flaps down. Four green indicators tell him that the hook is down and the undercarriage is down and locked. Any aircraft that cannot achieve a normal landing configuration is waved off or sent away to an airborne tanker to hold and land last. This is driven by the fact that all returning aircraft have to use the arresting gear. If this gear is damaged or made unusable, no aircraft can recover back to the ship[21].

 

 

 

The aircraft carrier marshals the returning aircraft into a tightly controlled and regularly spaced stream. Returning aircraft must arrive at a specific time to match the ship’s turn on to the flying course[22], and complete the landing as quickly as possible to minimise the time the ship spends on that flying course. Aircraft may be located in the stream according to their fuel states, and also by their serviceability, as aircraft that require maintenance will have to go to specific areas of the flight deck in a controlled order as soon as they land[23].

 

 

 

Aircraft are directed into a carefully controlled pattern to join the ship, often dumping fuel as they do so[24], to bring their landing weight to a required figure. The ship has completed its turn on to the flying course and has increased speed to bring the Wind Over Deck (WOD) to a carefully calculated figure driven by the types and weights of aircraft being recovered. The first aircraft lines up astern of the ship and starts down a precisely flown ‘glideslope’. From a handling point of view this is not unlike a land based glide slope.  But since the ship is moving forward at around 34 mph, the angle of the approach path is set at 4° relative to the ship rather than 3° (ship movement converts this 4° glideslope relative to the ship to 3° relative to the air stream). The extra degree provides an essential margin against deck movement – the ship may be pitching and heaving[25], unlike a runway. (It may also be rolling). As the approach begins, aircraft will be guided by a radar precision landing system that tells the ship where the aircraft is, and gives steering commands to the pilot via a set of ‘needles’ in his cockpit displays[26].

 

 

 

As the aircraft comes down the glideslope, more landing aids come into play. Lights on the ship help line his aircraft up laterally. He is already under the control of a Landing Signals Officer (LSO), a highly experienced and specially trained pilot, who is located on a platform at the stern of the ship close to the landing sight, and is watching the landing on a specially stabilised camera display. He gives mandatory commands to the pilot to line him up, and may at any time command him to ‘Wave Off’ and try the landing again. As the pilot closes with the ship, he starts to refer to the Optical Landing System (OLS), a direct descendant of the RN ‘mirror sight’ of the 1950s, which is fitted to one side of the landing zone. The ship has adjusted the OLS to ensure the correct ‘hook to eye’ distance[27] – a process that has to be repeated each time a different type of aircraft is recovered. The pilot adjusts power and angle of attack to align a bright yellow datum  (the ‘ball’) with a set of green horizontal reference lights, and as he nears the ship, his visual scan moves away from the ‘needles’ to focus completely on the ‘ball’. The recovery is about to enter its final phase, but in a way that is radically different from any airfield landing.

 

 

 

Pilots landing at an airfield will line up with the runway, reduce power and allow the aircraft to settle towards the runway. Near the ground, the aircraft encounters a ground cushion of air that slows its descent. The pilot ‘flares’, raising the nose, to reduce forward and vertical speed and further cushion the landing. Touching down on two wheels, power is cut, the aircraft slows down and after the nose wheel has touched down the brakes are applied[28]. Unfortunately, this technique cannot deliver the accuracy or reliability required for arrested landings[29]. As he comes over the stern, the naval pilot does not flare – that would result in the hook missing the wires. Instead, the aircraft is flown all the way down to the deck at a constant rate, hitting it at a vertical rate three or four times that considered usual for land based aircraft[30]. A loud thud, that can be heard two miles way on a land base, marks the arrival of specially inflated tyres with the flight deck and the explosive compression of the massive shock absorbers built into the landing gear as 20 tons of aircraft travelling at 160 mph hits the thick steel deck[31]. The airframe bucks and flexes up to two feet as the shock passes through the rest of the aircraft. The term ‘controlled crash’ is not far off the truth.

 

 

 

This ‘controlled crash’ takes place atop a complex machine called the ‘arresting gear’. Three thick steel wires run across the flight deck, held up by steel bow springs. Each end of these wires is attached to two longer wires that snake around a series of pulleys to be wound into the complex machinery of an ‘arresting engine’ situated below deck. These three ‘engines’ (one for each wire) are massive hydraulic devices that absorb the energy generated when an aircraft lands and pulls out over 600 feet of wire in two seconds[32]. This dissipation of energy has to be precisely applied to prevent damage to the aircraft[33], or snapping the wire, and the arresting gear team therefore adjust the settings of the engines for each separate type of aircraft being recovered, adjusted for their weapon loads or other stores they are carrying.  All is now ready.

 

 

 

The arresting hook catches the wire, and it roars out through its pulley blocks and out of the arresting engine at over 160 miles per hour. The wire whips, stretches and smashes the flight deck, and the arresting engine four decks down in the ship bucks and screams as it absorbs the thousands of horsepower generated by the aircraft through the wire. Within just two seconds, the aircraft is slowed down and comes to a halt about 300 feet up the flight deck.

Figure 6 – The Arresting Wire

Unless, of course, the hook has missed the wires. Or the hook has broken. Or the wire has parted[34]. The angled deck, coupled with a unique landing procedure and intensive training now come together to save the aircraft and the pilot. Unlike his land-based counterpart, the FAA pilot does not cut power on landing, but instead applies full power as the wheels hit the deck. He does this for each and every carrier landing, in case this event happens. Now, he carries out a ‘bolter’, another unique naval evolution. In less than a second, he switches from a landing to flying the aircraft and leaves the ship from the end of the angled deck. He can now climb away and prepare to carry out another approach and ‘trap’.
If the aircraft ‘traps’, it will come to a halt in about two seconds. The pilot is slammed forward in his straps with massive force. But he cannot pause or relax, as the next aircraft is already on the glideslope and only 45 seconds from the deck. The landing area must be cleared, and the arresting wire reset. A yellowshirt runs forward and takes control of the aircraft within two seconds. On his command, the pilot raises the hook to let the wire fall clear – specially trained ‘hook runners’ run out behind the jet exhausts and using long hooks, snare the wire off the hook if needed. More yellowshirts form a chain of command and following their orders the pilot taxis off the landing area at a fast running pace, with only 4 feet separation from other parked aircraft, folding his wings as he goes. Meanwhile, the arresting engine has been slammed into reverse to retract 600 feet of wire in 12 seconds, the wire scraping and moaning as it runs back at over 30 mph. Deck crews stay well clear – the wire will break their legs should it catch them. As soon as the wire is back in position, ‘wire runners’ run along the wire with armoured gloves, checking for any damage. Once this is reported clear, the LSO is clear to recover the next aircraft.
If the aircraft has a failure that means it cannot catch a wire (broken hook, or damaged landing gear), it will have had to wait until all other aircraft have landed, and then carry out a ‘barricade landing’. Almost all of the flight deck crew now execute a well-rehearsed drill where a complex set of nylon and wire netting (the barricade) is strung up between two large masts that emerge from the flight deck just beyond the last wire. The barricade is then attached to an arresting engine installed in the ship for this purpose.  The whole exercise, from start to finish with the barrier up and ready to receive the aircraft, takes around two minutes[35]. The aircraft comes in over the flight deck, and literally flies into the barricade, which wraps around the wings and brings it to a halt on the flight deck. If it is damaged, special recovery teams now work to clear the flight deck as soon as possible.

Figure 7 – Barricade Set Up and Landing. (The aircraft is a Royal Navy Sea Vixen.)
If this account sounds dramatic, it is meant to be. Carrier landings are, by some margin, the most demanding flying tasks required of any military pilots. Hard by day, they are tougher by night. They take place at the end of demanding sorties, and rely not only on the highest pilot skill level, but also a synchronised ballet of mechanical violence from a highly trained crew on board the carrier, operating an array of incredibly complex machinery and systems. If any part of the system fails or is not set correctly, the consequences can be dramatic and immediate – aircraft can fall over the side, run off the end of the ship, strike other aircraft, or hurtle into the ship itself. Deck crews can be maimed or killed. But training, practice and teamwork means that this rarely happens, and USN safety levels have steadily improved year on year with better aircraft and ever more effective landing aids. The result is a highly efficient capability that allows the carrier and its air group to get back on board in a short time and begin refuelling and re-arming for the next strike.
But it is never treated as routine. Bringing 20 plus tons of metal, fuel and explosives to a moving steel box at 160 mph and then catching a one-inch wire with a hook is a simply unique exercise. Deck landings are nothing at all like an airfield landing, and are likely to stay that way[36]. They are, quite simply, a compelling demonstration of the fundamental difference between land and sea based aviation.

 

 

How the Rest of Naval Aviation Happens

So far, this essay has focussed on launch and recovery to demonstrate the ‘particular mechanics’ of carrier aviation. However, getting aircraft ready, loaded on to the catapults and off the arresting gear requires another whole set of special skills and aviation practices that are utterly alien to land based air forces. Unlike an airfield, where the hangars, pans and runways are separated and optimised for a particular phase of aircraft operation, the aircraft carrier has just two small areas – the hangar and the flight deck. The hangar is located under the flight deck, and the two are linked by large lifts. Moving aircraft around this maze has been compared to an especially abstruse form of chess, where the players have to obey hundreds of special rules and constraints as they direct large teams to move large, highly explosive, flammable and expensive pieces weighing up to 38 tons.  ‘Checkmate’ means that the aircraft cannot fly or move[37].  A wrong move can result in damaging and aircraft, or even losing it over the side[38].

 

The flight and hangar decks, although large, cannot be split into areas reserved for single activities, as is done on an airfield. Aircraft need to be parked on lifts, taxied over parking areas, launched from parking areas, and moved past one another as the flying programme demands. Weapons have to be unloaded and loaded in amongst the organised mayhem. So, unlike an airfield, the flying programme and ground

Figure 8 – Managing Space and Time – Flyco, the Ouija Board, and Yellowshirts

movements have to be carefully planned and directed to achieve the flying programme. Lack of space affects all aspects of operating aircraft at sea, and the only solution is detailed and constant management of every square foot of space on the flight and hangar decks. The plan changes constantly.

 

But managing space is only half of the task. The other item that has to be managed is time. The only way that such a complex machine can work is with speed. On land, moving aircraft in and out of hangars is done at a slow walk, with time pressures rarely permitted to drive the pace of work. On board ship, all moves are executed only on approval of the command, and are done quickly to allow the next event to happen. The same applies to maintenance operations and starting aircraft. To play this particular chess game, aircraft carriers have a number of unique workspaces, populated by uniquely trained and experienced personnel.  ‘Flyco’ (Flying Control) is a glass cabin looking out over the flight deck, from where the flying side of the operation is controlled by the Air Boss, or Commander (Air) in the RN[39]. In Hangar Control, a simple yet effective steel board with magnetic pieces (the ‘Ouija Board’) is used to plan and control all flight deck and hangar movements. ‘Yellowshirts’ make the aircraft carry out the plan.

But there are more activities and people to manage. The flight deck is fed by a huge ‘fuel farm’ that delivers aviation fuel at very high flow rates (waiting more than 10 minutes for aircraft to fill up is not a luxury a carrier deck can afford). Specially trained personnel operate the compact yet powerful deck edge pumping stations and connect heavy hoses up to the aircraft as required. Weapons have to be brought up from deep storage, assembled, tested, delivered to the flight deck, moved to aircraft, loaded and armed. For safety reasons, this complex and highly safety critical supply chain has to work on a ‘just in time’ principle, so that the time weapons spend on deck and out of storage is kept to a minimum. This means that it has to be precisely aligned and managed along with the flying programme[40]. And when the weapons get to the aircraft, deck crews cannot use the large and complex mechanical loaders used on land – completely different weapon hoisting systems have to be used[41].
Weapons safety is a serious and constant concern for an aircraft carrier. A USN aircraft carrier comprises, from top to bottom, a flight deck packed with armed and fuelled aircraft, a hangar packed with fuelled aircraft, two pressurised water nuclear reactors, and below these, large ‘magazines’ with around 2000 tons of high explosive.  Fire and explosions are not items to be added to this particular mix. Specialist fire-fighters and salvage personnel are therefore on duty at all times – in the event of a crash, the survival of the ship will depend on their split second response. However, it should be noted that each and every person on the carrier is trained as a fire fighter and will be expected to help preserve the ship if required. Finally, all the complex and powerful machinery on the flight deck (catapults, arresting gear, tractors, lights, etc.) has to be maintained and operated. Flight deck mechanics, usually on 24-hour call, do this as well as manning the catapults and cable gear.
Only a few of these personnel are linked by radio. Almost all of them use training, practice and a highly developed sense of self-preservation to stay alive and effective in what several independent observers have called ‘the most dangerous workplace on earth’. They are trained to look out for crashes, fire and explosions. They know how not to fall and crouch down so as not to get blown over the edge of the deck to almost certain death. They cannot hear an aircraft (as amazing as its sounds, even the noise of a running jet engine is drowned out by the background howl of the flight deck), so they learn the tell tale signs of a running aircraft – an open blow in door, a raised landing gear door, a flashing light. They know what arresting wires and rolling ground equipment can do. And they can do all this at night.

And in amongst the noise, the rolling deck, the wind[42], the scream of catapults, the crash of landing gear, the crackle and rumble of engines in reheat and inside a forest of tangled aircraft, weapons and equipment, they repair and maintain the aircraft. The hangar is only available for the most complex tasks, and much routine work is carried out by day and night in the open on the flight deck. Again, most tasks are required to be completed against the clock, as it is an invariable rule that whatever space one has to do a task, someone else wants that space in 20 minutes time. Or now. And unlike on land, every piece of ground equipment and every toolbox has to be lashed down to the deck to stop it falling over or running away as the deck rolls and heaves.
A final point. Although this essay has focussed on ‘cat and trap’ operations, almost all of the issues highlighted here apply to the operation of STOVL aircraft, such as the F-35B, and rotary wing aircraft, including those of the Royal Air Force, Royal Marines, the Army, and any other operator. Their effective and safe operation from the deck requires the same ‘ethos’ (and specialist knowledge) to be applied[43].All of this is wholly unlike airfield operations.  Air Forces routinely (and quite correctly) stress that maintenance ‘is not a drill’ and must not be subjected to ‘time pressures’. Hangar and pan space is optimised, usually in the direction of ‘more’, to make land based operations as efficient as possible.[44].

Figure 9 – The ‘Synchronised Ballet of Mechanical Violence’ – Flight Deck Operations

 

Aircraft do not roll away by themselves, and do not require up to 10 chains to hold them in place each time they stop. It is no surprise that the FAA carefully monitor their personnel when they go back to sea to make sure that the habits of land operations are quickly put to one side. But it must also be appreciated that this ‘adventure in time and space’ delivers combat aviation in a highly efficient way. The iron hands of limited space and available time mean that the pace of operations on a carrier is always higher than on a normal land base. More gets done in less time[45].  The end result is this quite unique ‘synchronised ballet of mechanical violence’ that generates maritime combat aviation. To the casual observer it looks easy. As in the highest levels of sport, it looks easy only because a single team of consummate professionals are performing it. It should also be realised that these ‘professionals’ are predominantly very young men and women with different specialist training serving in separate units, brought together to perform these astonishing feats. The carrier will provide the yellowshirts, the ‘greenshirts’ who operate and maintain catapults and arresting gear, the purple coated ’grapes’ who provide the fuel, and the specialist fire fighters on deck. The ship also provides the many ‘redshirts’ that build and deliver weapons to the flight deck, as well as the operations and control room staffs. They have to work seamlessly not only with each other but also with squadron personnel. Squadrons provide ‘whiteshirts’ who control flight deck maintenance and carry out pre-launch checks. They also provide their own redshirts who carry out weapon loads.

Welding these teams together into a cohesive and effective ‘Air Wing’ is a key task for naval aviators and the ship’s officers.  It is essential for the safe delivery of effective embarked aviation. The key is the subordination of FAA squadrons to Commander (Air), who is a ships’ officer. This provides a single point of accountability to the ship’s Captain who is ultimately responsible for all aspects of his ship’s efficiency to higher command. This single point of accountability is also especially important for safe operation of aircraft around and within the ship, where emergencies demand seamless and synchronised reactions from pilots, engineers and, not least, ships’ officers such as the Officer of the Watch[46].These factors lead to a key difference between naval and air force squadrons. Unlike Air Force ‘expeditionary’ operations, where aircraft are located at a Main Operating Base (MOB) and ‘detached’ to airfields, FAA squadrons adopt a completely reversed posture. Their normal, routine base is the carrier.  Land based operations are a break in that baseline routine. It is no accident that FAA squadrons do not go onboard a ship as ‘detachments’ – they ‘embark’ as part of that ship’s armoury and company.[47].

This is all part of the different ‘ethos’ of naval aviation. And it is an ethos that delivers safe, efficient, cost effective and highly capable military capability. And it is also flexible. The reader would be forgiven for assuming that this training and practice results in a highly drilled team that can only perform certain pre-programmed tasks. Nothing could be further from the truth. The training delivers a ship and team that can, and does, adjust and adapt with astonishing speed to changes in requirement, emergencies and non-standard Air Groups. This is, above all, the most valuable attribute of aircraft carriers – flexibility[48].

 

 

What This Means for the Aircraft

 

 

This essay is not intended to cover the design of naval aircraft in any detail, but a brief exposition of the way that it differs from land based aircraft is required. It should be obvious that a naval aircraft is subjected to loads that simply have no parallels in land based aircraft designs. Catapult launch and arrested landings generate massive stresses in fore and aft directions to the ends of the fuselage, so space must be found for large ‘keel beams’ usually made from titanium. Every other part of the fuselage will also be strengthened, including skins and frames. Aircraft systems, such as flying control rods, hydraulics and electrical installations, also have to be reinforced to take these loads.

The arrested landing demands far stronger landing gear than for land-based aircraft, and these can be three times heavier. The arresting hook for a naval aircraft will also be far stronger and more complex than the emergency landing hooks fitted to land based aircraft such as Typhoon.  And once those landing loads have passed into the airframe, the structure will be far more massive to take the vertical decelerations imposed in the ‘controlled crash’ described earlier.

To achieve low landing speeds, naval aircraft must have larger wings and more effective high lift devices. But the changes do not end there. Carrying out precision deck landings demand not only flying skill, but also very good handling qualities at speeds well below those of a land based aircraft. These do not happen by accident, and they require larger and more effective control surfaces. The naval aircraft also has to be able to launch cleanly off the end of the catapult with no pilot input. This is another non-trivial challenge. Finally, it has to be able to switch seamlessly from precision landing to full power take off in under one second to be able to carry out a ‘bolter’. It also needs a specially designed cockpit to give the pilot the required field of view over the nose so as to be able to see the OLS.

There are even more challenges, however, for the naval aircraft designer. Folding wings and noses are usually required for the confines of the flight deck and hangar. Electrical circuits have to be shielded against the intense electromagnetic radiation exerted by the communications, surveillance and weapons systems built into the ship and located just yards from the flight deck. Special tie down rings are needed so that over 35 chains can be clipped on to the aircraft to hold it on deck in winds of over 100 mph. Finally, there is the important matter of corrosion protection, as sea water is especially destructive to the light weight materials commonly used by combat aircraft designers.

All these special requirements (and there are far more) mean that naval aircraft must be designed as such from the outset to be effective.  It is instructive to note that the ‘C ‘ variant of the F-35 Lightning II is the least common of the family of three aircraft[49], and carries a weight penalty of over two tons of additional metal to allow it to survive on the flight deck[50][51].

This essay has sought to illustrate the ‘Particular Mechanics of Carrier Aviation’, and how they have been developed and perfected by experts in the USN and the FAA to allow the safe and routine delivery of combat capability from the sea. And it has also sought to show that this is an achievable and practical exercise in military organisation and teamwork.

It appears obvious that the management and command of aircraft and carriers must be carried out by a single organisation that has clear accountability for delivering an integrated, effective and safe capability. The inter-relationships between aircraft and people and ship are so close, so potentially hazardous if not perfect, and so vital to delivering the required capability, that they must be under the control of a single responsible ‘duty holder’. A single ‘ethos’, a single aim and a single ‘whole ship’ way of operating, must be achieved under command of the ship’s captain. And that is what all practitioners of naval aviation do.

This is a tried, tested, effective and above all safe way of delivering maritime fixed wing air power. It is the model now applied by all the world’s armed forces that deliver this valuable capability. The concept of split command, as briefly tested by the UK with Joint Force Harrier, was ultimately found wanting. It is clear that future UK maritime fixed wing air power should be delivered via the most effective and safest solution – single command at sea.

 

Conclusions

 

This essay has sought to illustrate the ‘Particular Mechanics of Carrier Aviation’, and how they have been developed and perfected by experts in the USN and the FAA to allow the safe and routine delivery of combat capability from the sea. And it has also sought to show that this is an achievable and practical exercise in military organisation and teamwork.

It appears obvious that the management and command of aircraft and carriers must be carried out by a single organisation that has clear accountability for delivering an integrated, effective and safe capability. The inter-relationships between aircraft and people and ship are so close, so potentially hazardous if not perfect, and so vital to delivering the required capability, that they must be under the control of a single responsible ‘duty holder’. A single ‘ethos’, a single aim and a single ‘whole ship’ way of operating, must be achieved under command of the ship’s captain. And that is what all practitioners of naval aviation do.

This is a tried, tested, effective and above all safe way of delivering maritime fixed wing air power. It is the model now applied by all the world’s armed forces that deliver this valuable capability. The concept of split command, as briefly tested by the UK with Joint Force Harrier, was ultimately found wanting. It is clear that future UK maritime fixed wing air power should be delivered via the most effective and safest solution – single command at sea.

 

 

Recommended Reading

 

 

Chesneau, R. (1998). Aircraft Carriers of the World to the Present an Illustrated Encylcopedia (3rd Editon ed.). London: Brockhampton Press, Arms and Armour Press.

Jeffrey G. Barlow, (1999). The Revolt of the Admirals- the Fight for Naval Aviation. 1945-1950. Brassey’s.

Friedman, N. (1983). U.S. Aircraft Carriers. Annapolis, Maryland: Naval Institute Press.

Friedman, N. (1988). British Carrier Aviation. Annapolis: Naval Institute Press.

Gibbs-Smith, C. H. (1970). Aviation; an Historical Survey from its origins to the end of World War II. London: Her Majesty’s Stationary Office.

Heinemann, E. H., & Rausa, R. (1980). Combat Aircraft Designer; the Ed Heinemann Story. Annapolis, Maryland: United States Naval Institute.

Hobbs, D. (2005). Naval Aviation, 1930-2000. Richard. Harding (Ed.), The Royal Navy, 1930 – 2000, Innovation and Defence. Oxon: Frank Cass.

Layman, R. D. (2002). Naval Aviation in the First World War; its impact and influence. London: Caxton Editions.

Macintyre, D. (1968). Aircraft Carrier, The Majestic Weapon. London: Macdonald & Co.

Marriott, L. (2008). Jets at Sea; Naval Aviation in Transition 1945-1955. Barnsley: Pen and Sword Aviation.

Mersky, P. B. (2009). U.S. Marine Corps Aviation Since 1912 (4th ed.). Annapolis, Maryland: Naval Institute Press.

Rossiter, M. (2007). ARK ROYAL, The Life, Death and Rediscovery of the Legendary Second World War Aircraft Carrier. Great Britain: Bantam Press, Corgi.

Stille, M. (2005). Imperial Japanese Navy Aircraft Carriers 1921-45. Oxford: Osprey Publishing.

Wragg, D. (2009). A Century of British Naval Aviation: 1909-2009. Barnsley: Pen & Sword Maritime.

 

About The Author

 

Steve George is a retired Royal Navy Commander and Air Engineer Officer (AEO). In 28 years of service, he served on all three of the RN’s aircraft carriers in both helicopter and fixed wing squadrons. As with most AEOs, he held a wide range of appointments, including a unique exchange job with British Aerospace working on the T-45 Goshawk programme. He worked in the British Embassy in Washington DC, was the first AEO of the ‘Joint Force Harrier’, and was responsible for procurement of the .50 inch Heavy Machine Gun now seen on many RN helicopters, as well as the weapons now used by the ‘Apache’ helicopter. He was the AEO of 801 Naval Air Squadron, operating Sea Harriers from HMS Ark Royal. On leaving the RN in 2002, he joined the F-35 ‘Joint Strike Fighter’ programme in Fort Worth, Texas as a specialist engineer working on ship/aircraft integration. His MSc in Applied Flight Mechanics was gained at Cranfield in 1984, he was elected a Fellow of the Royal Aeronautical Society in 2003 and his expertise in aircraft weaponry was recognized in 2009 by the award of a Livery in the Worshipful Company of Gun Makers. He is still an active Engineer, and has recently led an MoD team that successfully delivered a number of key modifications to the Chinook helicopter for operations in Afghanistan.


[1] This essay intentionally omits the issues of affordability. However, post ‘Haddon-Cave’, the issue of safety is a vital one and is addressed in some detail.

[2] As an example, the F-35C is just over 50 feet long, yet weighs around 40 tons fully laden. These dimensions are, incidentally, very close to a fully laden articulated lorry.

[3] In many US bases, aircraft refuelling is carried out in separate ‘fuel pens’ located between the operating pans and the runways. Taxiing between these locations can involve journeys of miles

[4] (Friedman, U.S. Aircraft Carriers, 1983; Hobbs, 2005)

[5] (Marriott, 2008)

[6] Reliable figures indicate that over 300 USN pilots were killed in 1954. It is very probable that 1953 was even worse.

[7] An aircraft ‘stalls’ when,the air is not flowing over its wings fast enough to create lift to hold it up. As an aircraft approaches ‘the stall’, its controls become less effective.

[8] The mass retirement of USN senior officers that followed this became known as ‘the Revolt of the Admirals’. The US Air Force (USAF) had argued that the new B-36 intercontinental bomber could deliver air power (by nuclear weapons) anywhere on the globe, negating the need for shorter-range naval aircraft to carry atomic weapons. Removal of this requirement, in turn, removed the need for the new ‘United States’ class of carrier.

[9] The mirror sight replaced the 1930s style ‘batsman’. In the jet age, he could no longer be seen in time for the pilot to obey his signals.

[10] The ‘skewed deck’ was proposed in a secret UK Naval Aircraft Department document (Technical memo NA45) dated October 1951. The USN adopted the term ‘angled deck’, which has stuck.

[11] The ideas were so powerful and obvious that they were adopted with quite astonishing speed and massive international co-operation. Less than 20 months separated the first RN ‘skewed deck’ paper with sea trials aboard the modified USN carrier ‘Antietam’.  In 1954, the USS Forrestal, named after the Secretary of the Navy who resigned during the ‘revolt of the admirals’, was redesigned from a straight to angled deck configuration in a matter of weeks. US experts have estimated that the angled deck increased this carrier’s efficiency by around 240 percent.

[12] The current USN steam catapult can accelerate a 38-ton aircraft from rest to around 145 mph in under three seconds within 300 feet. It can then do that again in under a minute. The new electrical catapults (EMALS) are not small. The EMALS motor generator weighs over 80,000 pounds, and is 13.5 feet long, almost 11 feet wide and almost 7 feet tall. It delivers up to 60 mega joules of electricity, and 60 megawatts at its peak. USN carriers have four of these devices and CVF will have two.

[13] In normal operations, land based military aircraft are not limited by runway length, and fill to maximum fuel. If required, runways are lengthened. If this can’t be done, and aircraft takeoff performance is limited by runway length (as with UK Tornado operations in Afghanistan), weapon loads have to be limited. If this isn’t enough, standard safety margins have to be adjusted downwards to allow operationally viable missions to be launched (as has been done in Afghanistan). This, in turn, increases the risk of take off accidents.

[14] JBDs are massive items of equipment, comprising six slabs of steel, each six feet by ten, hydraulically powered up and down out of a pit in the flight deck. They drive up and down in around five seconds and weight several tons. They will cut a man clean in half, should deck crew be careless enough to get in their way. They don’t.

[15] Yellowshirt commands to pilots are mandatory, and no movements take place unless under ground crew control. This basic aspect of naval aviation causes cultural difficulties for RAF pilots, who are accustomed to ‘advisory’ signals rather than ‘mandatory’ ones, and being in charge of their aircraft at all times.

[16] This accuracy of positioning is simply unheard of in land operations, and drives the design of nose undercarriages on naval aircraft.

[17] This small element of the evolution requires some skill and training. The hold back bar weighs around 70 pounds and the aircraft is moving at a fast walking pace. The deck crew must move in under the moving aircraft while avoiding intake suction and other hazards.

[18] Allowing personnel under moving aircraft would never be countenanced in Air Force operations. (Until recently, RAF helicopters were still forbidden to refuel with their rotors turning, a standard shipboard procedure).

[19] They have to be around 8 feet from the nozzle to do this. The noise level they are exposed to is immense and demands several layers of hearing protection.

[20] Again, it would be unheard of to park aircraft so close to a runway on an airfield.

[21] ‘Non-diversion’ flying, where the only option available is to land on the aircraft carrier is a basic requirement for effective naval aviation. It is notable that recent experience with Joint Force Harrier showed that Air Force pilots were profoundly uncomfortable with this practice, and made availability of a land diversion a precondition for any flying from the ship.

[22] The carrier will turn so as to bring the wind down the angled landing area.

[23] The rigid ‘Charlie Time’ (time of return) for aircraft an aircraft carrier is another departure from land-based operations, where aircraft will normally land at the discretion of the pilot within 5 or 10 minutes of the time planned. Again, this is an area where Air Force pilots have had difficulties.

[24] Another departure from land based operations. Extra fuel means extra weight, which would increase the landing speed, possibly beyond that which the arresting wires could take.

[25] ‘Pitching’ means that the ship is moving like a seesaw. ‘Heaving’ means that the whole ship is moving up and down like a lift.

[26]The skills required to execute this approach and landing are both demanding and highly perishable. A pilot goes nowhere near a deck until they have completed a long training course. Once qualified, even when ashore, naval pilots will constantly practice deck landings using specially modified runways.

[27] Hook to eye distance is the distance between the pilot’s eye and the tip of the arresting hook. The OLS brings the pilot’s eye down a glideslope, but the hook tip is many feet below his eye. The OLS is therefore adjusted to offset the pilot’s eye line to get the hook tip to take the wires.

[28] This type of landing is familiar to any airline passenger.

[29] Carrier recoveries are strictly time limited, and it is vital that ‘traps’ are achieved as often as possible, especially if other aircraft are waiting to land. The USN imposes strict ‘trap success rates’ for day and night operations – pilots who fail to achieve these are removed from their ships and sent back for retraining before they can be declared operational again.

[30]This single feature of naval aviation causes most of the design changes in the F-35C variant. The extreme loads applied to the landing gear result in components weighing three to four times a land based design.

[31] The steel that is used to build CVN flight decks is specially toughened and treated to resist the thermal and mechanical loads without bending or cracking. Its composition is a closely guarded secret and it is made to special order only for the USN.

[32] The US Government closely controls the design and manufacture of these arresting engines – they are designed and assembled by the US Navy. US Navy technicians carry out installation and setting to work.

[33] The ‘run out’ for an arrested landing varies from aircraft to aircraft. Interestingly, it is longest for the slowest landing aircraft, the E-2 ‘Hawkeye’. This is because this aircraft has the least strong fuselage structure, and cannot take high hook loads.

[34] A breaking arresting wire will whip across a flight deck at over 75 mph, maiming or killing anyone in its path. Flight deck crews are required to be constantly vigilant and take evasive action should this happen.

[35] By this time the reader will not be surprised to learn that ‘rigging the barricade’ in that time depends on constant practice and a high degree of expertise.

[36] There has been some uninformed speculation on the advent of automatic carrier landing systems that will remove the need for this level of pilot skill and training. While the USN has had ‘autoland’ systems for many years, and is developing new systems, it is considered highly unlikely that they will ever rely completely on such systems, in case they fail or malfunction.

[37] This has happened. In the early days of aircraft operations on HMS Invincible in late 1981, as the RN was relearning the ‘particular mechanics’, a series of misjudgments by the Ships’ Commander (Air) resulted in the flight deck, lifts and landing spots all becoming completely blocked by parked and unserviceable aircraft, none of which could move. Unfortunately, a Sea Harrier was airborne and running low on fuel. Only exceptional flying skills, which allowed the pilot to land on a clear, but small, area of deck, saved the aircraft.

[38] Aircraft are routinely moved around just inches from a deck edge over 70 feet above the sea.

[39] The working relationship between Commander (Air), his Air Department and the embarked squadrons is a fundamental one to safe operations, and an intrinsic part of the required ‘ethos’. Experience with Joint Force Harrier has shown clearly that current RAF doctrine and ethos does not support that relationship. It is understood that the RAF have proposed that embarked F-35 units must be led by an RAF OF-5 level officer (in addition to the squadron commanding officers) to ensure ‘parity with the ship’s captain’. Such a move would cut across an essential chain of command from Commander (Air) to the squadrons.

[40] It is quite normal for RAF aircraft weapon loading to be carried out some time before takeoff (12 to 18 hours is not unusual) so as to leave loading crews unaffected by time pressures. On board ship, weapon loading is usually prohibited until no more than 2 hours from launch, to minimize the hazard presented by armed aircraft on the flight deck. Effective and timely weapons supply is therefore an essential skill, and one that the RN had discarded in the late 1970s. It had to be relearned and rapidly re-established as the Falklands Task force sailed south, by flying out experienced officers who were about to retire.

[41] For the simple reason that the aircraft will normally be moving about relative to the deck, as the ship rolls and pitches. Weapons must therefore be winched up on to the aircraft, instead of being offered up to it by a loader unit.

[42] As the carrier is always moving through the sea, there is always a steady wind over deck of around 25 mph. In anything but the tropics, this means that all flight deck personnel require warm and waterproof clothing and footwear. It also means that any paperwork taken on to the flight deck needs careful handling.

[43] The successful use of Apache attack helicopters from HMS Ocean during operations off Libya were the culmination of several years of dedicated trials and hard work by RN and Army engineers and pilots. It was notable that USN Combat Search and Rescue aircraft were able to embark without such effort from the UK, only because the USN had done the preparatory work over many years. Very close RN/USN relationships, built up over more than 40 years, allow such ‘cross decking’ to take place.

[44] As an example, ‘lean’ efficiency measures have reduced the number of RN Merlin helicopters stowed in hangars to be reduced to allow special ‘servicing areas’ to be used, complete with painted rectangles for every piece of ground equipment. Such methods are ‘efficient’, but impractical on board a crowded ship. Another example illustrates this point. When Joint Force Harrier aircraft were disembarked from a carrier to an Omani airfield during a major exercise, RAF weapons safety specialists at Strike Command directed that aircraft that had been parked 6 inches apart on the ship had to be a little more widely spaced on land. The required spacing was three quarters of a mile.

[45] And less people do it. This is absolutely not because carrier personnel are cleverer or better than their Air Force counterparts. It is simply because there are less beds available on a carrier than on a land base.

[46] As an example, should an aircraft go over the side of the flight deck, the ship must immediately and correctly change course to avoid running over it and killing the pilot.

[47] This was the case for many years, until the formation of Joint Force Harrier. Under RAF control, aircraft went to sea as ‘detachments’, with administrative orders written by HQ Strike Command exactly as laid down for foreign airfields. The first ‘detachment orders’ for Joint Force Harrier stipulated, in some detail (50 pages) the use of guard dogs and RAF Police on board HMS Illustrious to prevent aircraft being approached by ‘foreign personnel’.

[48] The RN and the FAA are masters of this particular skill. The Falklands war was fought with unique Air Groups on HMS Hermes and HMS Invincible that were formed as the ships sailed. Just over three weeks later, these two ships delivered a level of air power, under atrocious weather conditions, that the USN had officially assessed to be ‘impossible’. The unofficial motto of one FAA Sea King squadron at the time was, unsurprisingly, ‘Remain Rigidly Flexible’.

[49] The F-35C’s structure has less items in common with the baseline F-35 design than the other two aircraft, as well as major changes to the landing gear and flying controls.

[50] This issue has been overlooked in recent years as the F-35B STOVL variant has come under close public scrutiny. In fact, the F-35C carrier variant has always been recognized as an especially demanding design challenge, and this was why it was programmed to be the last of the three variants to complete design and enter flight test.

[51] This is not a new experience for UK aircraft designers. Converting the tough Hawk trainer into the T-45 Goshawk carrier training aircraft for the USN required over 80% of the aircraft drawings to be changed and added over a ton and a half of metal. And this was for an aircraft that carries no military payload and is operated under the most benign deck conditions. Proponents of a ‘Sea Typhoon’ should, in the author’s opinion, be much more closely questioned as to how the much more lightly built Typhoon airframe is expected to withstand maritime operations.

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