What are the advantages of the angled flight deck layout used by some aircraft carriers? [duplicate]

Question

I've been flying aircraft carrier approaches in a flight simulator lately and noticed that the carrier has an interesting layout. I have an image below where the landing runway is in red and the takeoff runway is in blue.

I can understand the takeoff runway - taking off into the wind with the catapult so that you can get enough air flowing to take off. The part that confuses me is the position of the landing runway. It is at a slight angle to the direction of the carrier's motion, meaning that when I fly the approach I have to aim to the right of the carrier and let it move underneath me. It seems to me as though this would just complicate an already difficult procedure, particularly in rough weather conditions.

Why not just take off and land in the same direction? As far as I am aware the aircraft only take off forward of the jet blast shields i.e. at the tail of the blue arrow. This would leave plenty of room on the carrier for landing. The only time I can think this would be a problem would be when a pilot needs to abort the landing and quickly take off again when there is another jet waiting to take off ahead of him, though this would assume that aircraft were taking off at the same time as others were landing (I have no idea if this actually happens).

It would be great if someone could shed some light onto why aircraft carriers have this layout - I'm not a pilot, just been playing around in simulator.

Answer 1

This kind of layout is called the angled flight deck (also called 'skewed' or 'canted' deck) and was first used by Royal Navy. There are a number of advantages to this layout compared to using the same direction of landing and takeoffs:

• It allows concurrent landings and takeoffs.

• By having an angled deck, the aircraft which fail to connect (with the arrestor cables) during landing can go around and try again without risk of damage to other (parked and taking off) aircraft).

The main reason for the emergence of angled deck was the introduction of jet aircraft in naval operations, which due to their weight and high speeds required most of the deck available to complete an arrested landing. Also, in case of missed wires, it was possible to use a barrier in case of propeller aircraft, which was not possible in case of jet aircraft. According to Rear Admiral Dennis Campbell, the inventor of angled deck,:

But with the advent of the heavier faster jets, it soon became obvious that the dimensions of the carrier's deck would impose a limit to the standard of aircraft that could be operated. The inevitable increase in weight and landing speed of the jets would make it impracticable to retain the existing combination of arrester wires/barriers/and deck park without a drastic reallocation of the deck space required to absorb the much longer pull-out of the wires.

Prior to the application of the angled deck, this caused significant problems and requirement of complex machinery to overcome.

Ark sister ship and predecessor, the Eagle, was equipped with sixteen arrester wires and three different types of barrier (together with all their several hydraulic machines), and all this gear could only just cope with the first generation for (straight wing) jets. No way would such a layout be good enough for the newer types.

The solution was to skew the flight deck by about 10 degrees (the HMS Ark Royal first had the flight deck angled by 5 degrees, which was then increased to 10) and use it for landing. This lead to:

1. The saving in arrester gear units and barriers – Ark needed only four wires and one (emergency only) barrier. The reduction in weight and the extra space that this conferred enabled more mess-decks to be fitted in, thus reducing congestion in living spaces.

2. Since landing accidents would obviously be far less frequent, fewer aircraft and spare parts would be needed so costs would be greatly reduced.

3. Similarly, death and injuries to aircrew and deck handlers could be kept to a minimum – with a big boost to confidence and morale, not to mention the saving in training costs.

4. As experience was gained of the new scheme, less obvious advantages came to light. New areas of parking, (abaft the island for instance); an added flexibility in the relative wind speed and direction, easier and faster deck handling, less wear and tear on the command, etc.

Perhaps surprisingly, though the USN has adopted this system in its supercarriers, the RN dropped it later on.

Answer 2

An angled flight deck resolves many problems identified during WWII with carrier combat and flight operations (in addition to some of the other issues related to jet aircraft).

The first relates to the importance of not having a crash landing stop flight operations (or wreck staged/landed planes). For example, straight deck carriers often recovered planes in a fashion like this (images from Wikipedia, the USS Saratoga):

Notice the plane landing has a short distance to actually land/stop.

It is important to realize the implications of a crashed landing or an overlanding. A plane landing at this way, if it somehow jumped the barrier/missed/overshot is going to crash through many parked/staged planes. Clearing a flight deck, even with multiple elevators, is not instantaneous.

Next, let's consider the takeoff process. Again, look how many planes are staged on the flight deck:

This sort of operation was typical in the era before and during World War Two.

It's important to realize that most carrier configurations looked more like the ones here than what we think of when we think of a supercarrier when the angled flight decks were introduced. The experiences of those running WWII flight operations and the lessons learned drove the implementation of angled flight decks.

Imagine too if a plane returning to the ship suffers damages during landing or crashes. Given how the flight operations worked, this would prevent the ship from doing anything until the plane was dumped overboard/pushed out of the way. In a combat situation, precious minutes could mean the difference between a CAP being launched -- or no planes being launched.

Additionally, having two "runways" means multiple planes can be launched simultaneously. You get nearly twice as many launches per minute when having two runways.

The USN was already experimenting with multiple launch points with a hangar deck catapult with the Essex class:

While not wildly successful, it shows the USN was already interested in having multiple launch points for planes (don't try landing through this area!). These were all removed eventually during WWII but the need is indicated through their initial installation - six Essex carriers had hangar deck catapults installed.

Again, this indicates that there was a compelling problem to be solved with a straight flight deck and single launch/failure point.

Related to the increase in plane weights, having a longer "landing" zone allows heavier planes to actually accelerate upon landing in order to have enough airspeed to abort if needed. With either configuration as shown here, you would never want to be accelerating on landing if not required to prevent stalling - if you did you are simply increasing the risk of crashing into the other parked planes. Especially as plane weights increased and speeds increased, the risk of overshooting the barriers increased.

Another advantage is the increased ability for elevators to access the hangar deck. With a straight flight deck, you only can really have elevators that take away from your usable space. While the Essex class started this trend, having their elevators slightly sticking out from the ship, look at where the elevators were located in your image - they are completely out of the way of both flight decks. This is another advantage of the angled flight deck, because it means you can operate the elevators and use them to stage planes without significantly affecting flight operations. A straight flight deck has minimal ability for this.

Last for this mini-book, having two "flight decks" means that in a combat situation, a single bomb doesn't put your ship out of action. Many US carriers were put out of action temporarily from single hits to their flight deck. Having two "runways" means that you build in some safety in that you can use your ship to launch or recover aircraft even if you take damage (again, keep in mind that during these conversions WWII was fresh in the minds of designers/naval officers).

Answer 3

The angled part of the deck allows landing aircraft to go around if necessary as well as permitting simultaneous takeoffs and landings safely when that is necessary. As I understand it (perhaps a carrier pilot could enlarge on this), a carrier pilot wants a 4G landing impact. At the point of impact, he goes to full thrust so that if he doesn't catch a wire, he can safely fly off the end of the angled deck. If he does catch a wire, he immediately closes the thrust lever.

They don't flare. Years ago I checked out a carrier pilot in a C182. He said the hardest part of flying the 182 was having to flare the aircraft for landing. He explained that for carrier landings, they fly the airplane onto the deck with no flare. The 4G desired impact figure came from him. I seem to remember also that he said they want to catch the third wire.

Also, I believe the preferred terminology is "carrier traps" rather than landings, but I'm not certain.

Answer 4

I have heard that one additional reason for the angled landing deck is: If a plane somehow misses a landing, but does not have enough speed to take off, it will end up in the water slightly to the port side of the ship. The pilot can be picked up by a support ship. With an older straight deck, (if the deck was clear of airplanes - generally not the case), the landing plane would end up in the water directly in front of the carrier, and be run over by the carrier, and torn up by the propellers. That is not easy on the pilot. Such an overshoot has actually happened when an arresting cable slowed the plane below flying speed, but then broke. (I am not a pilot.)

Answer 5

Aeroalias covers the primary reasons the angled deck was introduced i.e. To facilitate the recovery of larger jet aircraft. Back in WWII, flight operations aboard carriers would allow for one-way-in recoveries on the stern of the ship while aircraft were parked, hangared, or were launched from the bow. Once the LSO gave you the cut signal, you pulled the throttle to idle and set it down on the deck. In order to protect the aircraft tightly packed on the bow of the ship, you were going to either snag a cross deck pendant or go into a barricade near the ship's waist. This is why the Eagle had 16 cross deck pendants and two types of barricades. This was an inefficient, cumbersome and oftentimes destructive arrangement, especially when the plane could not snag a wire with the tail hook and went into the barricade and just became impossible by the time swept wing jets entered the fleet.

So it made more sense to provide an area where a recovering aircraft could touch down and be arrested to a full stop or add power and go around; this of course comes into direct conflict with the naval architecture of the carrier i.e. ships are designed as long rectangular structures and don't offer much lateral room from that to spare. The only effective solution was to angle the landing area, giving a approaching jet a clear flight path to go around in.

And on the plus side it kept the bow clear and added extra deck real estate to launch jet aircraft from using the new and more powerful steam catapults (another British invention). Positioning of the aircraft elevators on the port and starboard sides of the ship as opposed to the center of the bow gave even more space and alleviated congestion.

Answer 6

I'd prefer to avoid bumping into any of the catapults' pits so angling your landing through the superstructure sounds just peachy, regardless of how many super-steep-angled Chuck Yeager landings in mountain foothills you've ever approached (old timer instructors will grey your hair QUICKLY!)