Cat shot
Aircraft carriers are the centerpiece of America’s Naval forces – the most adaptable and survivable airfields in the world.
US Navy flat tops support and operate aircraft that engage in attacks on airborne, afloat and ashore targets that threaten free use of the sea and engage in sustained power projection operations in support of US and coalition forces. Aircraft carriers must be able to launch these aircraft in such a small space. With so much chaos in such a small area, engineers have had to design catapults, simple yet effective devices to help manage the process.
Getting air moving over the deck is important, but the primary takeoff assistance comes from the carrier’s four catapults, which get the planes up to high speeds in a very short distance.
Procedures used after catapult shot (or cat shot) are based on meteorological and environmental conditions. Primary responsibility for adherence to the departure rests with the pilot. However, advisory control is given by the ship’s departure control radar operators, including when dictated by weather conditions.
In Case I* or Case II* launches, immediately after becoming airborne, aircraft raise their landing gear and turn to the right off the bow and to the left off the waist catapults.
Why is that?
Clearing turn
Robert James, Naval Aviator with 153 combat missions and Top Gun graduate, explains on Quora;
‘It’s called a clearing turn. Depending on the aircraft weight and the wind over the deck (carrier speed plus natural wind), an aircraft might take a cat shot with the desired “10 knots excess”. That means the cat crew will give you enough steam pressure to achieve the desired result and you clear the bow with plenty of flying speed. However, there is a limit to how much force they can apply to the aircraft. Back in the day, the limit was the point at which the launch bridle was attached to the airframe. These days, it’s the nose tow apparatus. But the idea is the same. You can only shoot an airplane so hard without suffering structural damage.
‘Now let’s say the ship has a boiler down and there is not any natural wind. That means the ship can’t give you the desired 30 knots over the deck. It can happen, or it used to happen, that the Cat Officer can shoot you with “zero end-speed”, a call no pilot like to hear. It means you go off the bow with no margin for error; i.e. just above stall speed. The last thing you need is to fly through the wake turbulence produced by the guy launching from the adjacent catapult when you’re barely flying.
Not afraid to die
‘So just as you clear the deck and as soon as you’re confident the airplane is flying OK, you bank away from the ship’s course to be sure your squadron mate does not hit your turbulence. Even with normal excess end speed it’s dangerous and can easily turn deadly if the other guy doesn’t have the desired excess flying speed.’
James concludes;
‘Of course, if you think you’re bullet proof and you aren’t afraid to die, you can put in a gob of aileron as you’re sitting on the cat waiting to launch. That way, you perform a snappy clearing turn immediately when you clear the bow. The cat crew loves it, the Air Boss hates it, and you take it as another data point that you indeed are impossible to kill. It worked for me.’
* Case I is the state when it’s daytime and the weather allows for good visibility around the aircraft carrier. Formally, it’s “during day VMC (Visual Meteorological Conditions) conditions (weather 3,000-5 or better)”, meaning the ceiling is no lower than 3,000 feet, and the visibility is no less than 5 nautical miles.
** Case II happens when flights may encounter instrument conditions during a daytime departure/recovery, and the ceiling or visibility in the carrier control zone are no lower than 1,000 feet or 5 nautical miles, respectively. It is used for an overcast condition.
Photo by Mass Communication Specialist Seaman Rafael Figueroa Medina and PH1 Gerwien / U.S. Navy
