Monday, October 26, 2009

Navy Tech – The Launch

It sounds simple enough; launching aircraft off the ship.

First you drive the aircraft to the catapult, then you hook it to the catapult, fire catapult, plane flies. Usually, most of the time they do.

But the devil is in the details and I am here to give you some of those details. Here is how it works.

The Players:

The Director – a Yellow Shirt trained in the art of precise aircraft spotting

The Cat hookup – a Green Shirt that hooks the aircraft into the Flight Deck and onto the Catapult

Final Checkers – the last Squadron Rep's who give the aircraft a once over ensuring the aircraft is ready to go, from the outside.

The Shooter – one of the Cat 'O's his job is to accept control of the aircraft from the Director, take the salute from the aircraft pilot and then signal the launch of the catapult

The Equipment:

Zipper track – a short area at the base of each catapult track that allows each different size aircraft an anchor point for well'

the Holdback – this bar is used to attach the aircraft to the ship, the bar connects into the back of the Nose Landing Gear using a holdback fitting, the other end of the bar is sunk into the zipper track, locking the aircraft into the ship.

Below: The white bar with the Yellow cap is a Launch Bar. This one is for an F-18 which actually use a reusable link/coupling instead of a shear pin as the holdback fitting. (USN Photo)

While the S-3 Viking/War Hoover departs in the background, the foreground shows a selection of Holdback's. One for each type of aircraft and they are color coded to match the fitting in the nose wheel well. (USN Photo).

The Holdback Fitting – this is a piece of high strength steel, turned with a collar at both ends, precision turned to very precise specifications, these are very purposely built shear pins, designed to break at a specific amount of tension. That tension is usually the full thrust of the aircraft PLUS some amount of catapult tension, and then a few pounds. This fitting splits when the catapult actually fires thereby releasing the aircraft from the Holdback Bar. (See update at the bottom of this post for picture.)

The Shuttle – this is the visible part of the catapult, the part that sticks up above the catapult track. The front edge of the shuttle is shaped like a set of jaws which grip the next piece of the equipment puzzle

The Launch Bar – part of the aircraft, this retractable bar is shaped like a "T", when deployed it drops into the shuttle jaw.

This pictures shows the Launch Bar of an S-3 already lowered down to the flight deck, it is the white bar that reaches down to the flight deck. The use of the launch bar on the Nose of the aircraft give us the name of the catapult shot, a Nose Tow versus a Bridal, which are now all out of service. (USN Photo).


Directors at each catapult direct the aircraft onto each catapult. There is a lot of science in this because each aircraft width and length has to be taken into consideration. Before the aircraft gets to the shuttle and hooked into the ship it must be positioned as much as possible centered over the cat track. There are marks welded into the flight deck to give the Director some help, but most is done by eye.

Above, each aircraft is placed on the cat by a ships company Yellow Shirt or Director, the flight deck has welded marks that corelate to spots for the nose and main wheels of each type of aircraft. These marks allow for the precise positioning of each aircraft on the catapult. (USN Photos)

The Hook-Up

While the aircraft is being positioned onto the base of the catapult, the Cat Hook-Up Green shirt comes out and hooks the Holdback with holdback fitting into the aircraft landing gear at the one end and into the zipper track at the other. At this point the aircraft is basically attached into the flight deck. No more brakes.

Below. Here the Cat Hookup runs out from under the "Surburban" or EA-6B after a sucessful hookup and tension. Note the Holdback is pegged behind the nose landing gear and the launch bar engaged into the cat shuttle. (USN Photo)

Here is another good hookup, this War Hoover is pegged and the cat shuttle is engaged, the aircraft is at full military power awaiting the actual shot. (USN Photo)

Usually a Green Shirt carrying a weight board approaches the aircraft cockpit and holds up his board up to the cockpit. The Pilot reviews the numbers shown to him. If they are good, representing his launch weight he gives a thumb up. If not he shakes his head as if to erase and then he signals the appropriate direction the weight board should be dialed to. Again, once it is good he gives thumbs up and the Green Shirt with the weight board turns it and shows it to the men station inside the Integrated Catapult Control Station. They in turn set the catapult to the setting indicated.

Here you can see this F-18 Launch Bar is deployed to engage the cat shuttle, you can see the slack between the shuttle and the launch bar. This slack will be taken up when the Cat Hookup puts the aircraft and Cat in tension. Note the Weight Board in the background. This is the Launch weight of the aircraft on the catapult. (USN Photo)

While taxing into position, the aircraft crew deploys the launch bar which when lowered rides down the cat track as the aircraft moves forward, the launch bar rides on the top of the shuttle and down into the shuttle jaw.

You can see here the Holdback pegged into the flight deck and the Launch Bar engaged into the shuttle. The F-14 Nose Landing gear will actually squats down onto the shuttle when the launch bar is deployed. (USN Photo)

Final checks

Also while taxing into position the Final Checkers deploy doing their chores one on each side of the jet. We use two so as to cover each side, they make sure all doors and panels are secured, they check landing gear, engine bays for leaking fluid or oil, they check to make sure any linkages are not binding or frozen and they confirm locks are set the folding wings. They also verify the performance of the flight controls during the "Wipeout" process done by the pilot. This is the movement of the stick and rudder in the cockpit to confirm that all is ok with the equipment. No binding, grinding or un-due resistance of the flight controls.


Once the launch bar is firmly in place in the jaw of the shuttle, the Cat Hook-Up requests that the aircraft be placed into tension. This is a sweeping hand signal made with a closed palm in the shape of a 'C'. The Director, standing off to the side signals this to the Pilot with an open fist of one hand and with the other hand he makes a sweeping motion which the Cat Operators interpret as Tension. The Pilot advances the throttles to full military power setting, the engines screams and the aircraft tugs on the Holdback Bar. If all is well the plane sits there while the Cat Operators takes up any slack in the catapult system, placing a minimal amount of pressure on the shuttle. Again, if all is well the plane sits there straining. The Cat Hook-Up man runs free and clear of the aircraft with a thumb up in the air signaling all is well. The Director then turns control of the aircraft over to the Cat 'O' or Shooter.

Here an F-18 is almost ready to go, the Cat Hookup is complete and they are calling for Tension, the outstreched hand in the form of a "C". The cat is pre-tensioned and the aircraft goes to full military power. These two cat hookup men will confirm proper engagement of the cat shuttle with the Launch bar and that the holdback is properly pegged. Then they haul ass out from under the screaming aircraft. (USN Photo)

The Shot

In the cockpit the pilot does a quick review of his launch checklist, verifying engine instrument settings, he does wipe out and checks to make sure his brakes are not set. If all is well, he sits back and salutes the Shooter and waits. The Shooter returns the salute with the one hand and waving the other in the sky he looks around, they too have a checklist that they go over in their minds, checking clearance around the jet, he verifies thumps are up from the Final checkers and he even takes a glance up to the Island to verify that he still has a Green light for launch. And they really do have signal lights on the Island, Red, Yellow and Green indicating that the Ship itself prepared for the launch. The ship has to be into the wind and it has to be up to speed. This is all relayed to the Deck crew using the lights on the Island.

Seeing everything in the positive, the Shooter drops down, touching his one hand on the deck and pointing that-a-way, signaling the command to Launch. Somewhere in the Integrated Catapult Control Station someone in Yellow pushes a button and the aircraft is shot down the flight deck.

This picture was taken right at the actual shot, you can see the holdback has seperated and the pressure from that snapping shear pin or holdback fitting shots the holdback straight back, it is actually attached to a spring loaded lug. This is a shot from one of the Waist Cat's. Also note the two missiles, one a Phoenix and the other a Sidewinder are both "war" loads as noted by the yellow band around each. If these were 'duds' they would have blue bands. (USN Photo)

The Ride

When the cat actually fires it puts about 60% of total pressure on that initial start. The modern steam catapult does not hit the aircraft with a full load of steam right at the launch, rather it builds such that about mid-way down the track it hits full power. This allows the stress on the jet to build up over time instead of all at once and it keeps the crews from blacking out or getting tunnel vision (which I experienced on each of my cat shots).

Another Tomcat takes the ride. (USN Photo)

At the end of the cat track the launch bar is released from the shuttle and the aircraft can fly away if possible, sometimes it takes the great uplift of air over the bow to nudge the aircraft up into the sky.

Here a Hoover takes the ride. This is at the bitter end of the Cat track, the shuttle is behind the nose wheel and the Launch bar is in transition to it's stow position. This Hoover will leap into the air in a few moments or go swiming. (USN Photo)

A "Cold Cat" is one of those where something went wrong and the Jet most likely won't fly at the end of the cat stroke. In 5-years on the Roof I only saw this happen once. An A-7 in that case but the Escape PAC-II series ejection seat worked good!

Below: Here a War Hoover does something that is pretty rare. It was called Flying at Anchor or Flankering. The S-3's and the C-1/C-2's were capable of take off with no winds over the deck. All the other aircraft require the ship to be in movment. (USN Photo)

UPDATE: I found a picture of a Holdback Fitting. These ones are for an EA-6B the one on the left is whole and the one on the right is spent, used. You can see how it snaps. These are again attached into the back of the nose landing gear with the holdback bar that is then attached to the flight deck. These are all color coded to match both the knuckle that they attached to in the landing gear and to the actual holdback bar. The E-2 was a light blue, the S-3 was a magenta color. (Picture stolen from a website that is selling them which may be illegal, at least for the whole units, so I won't identify them, just in case.)

BT: Jimmy T sends.


Anonymous said...

An excellent description of the process. I have a question about the holdback. I understand the purpose, but I don't quite see how the holdback actually works.

One end is attached to the aircraft, and the other to the deck. That part is simple. And once the cat stroke begins the holdback shears and releases the aircraft to launch. But doesn't that leave one part attached to the aircraft, and the other attached to the deck? And doesn't that potentially create FOD?

Perhaps you have a photo, or an illistration of some kind that would help me to visualize the process.

JimmyT said...

Anonymous, I wish I could find the three holdback fitting or shear pins that I own, but I could not. The fitting looks a little like a very small bar bell. And yes, when it shears one small piece stays in the knuckle on the aircraft which is removed and tossed into the ocean upon return, the other part stays in the Holdback Bar, it too is tossed into the deep six. The three spent fittings I have are from historic flights, the first S-3 launched from the USS Independence and the first from the USS D.D. Eisenhower both of these are the part that stays in the holdback bar. The third one is the spent end that stays in the aircraft of my first cat shot in an S-3 aircraft. I just could not find them for a photo, nor could I find good ones on the internet.

BT: Jimmy T sends.

Bag Blog said...

"Then they haul ass out from under the screaming aircraft." This is my favorite part. Since I am into American Sign Language, I like the hand signals too. Acutally, I find it all pretty fascinating.

Buck said...

I'm like Lou: fascinating! Your narrative and the supporting pics are simply wonderful, Jimmy.

JimmyT said...

Lou, back in my day only a few people had radios in their helmets, today most everyone does, so back in the day we had a ton of hand signals that you had to know to communicate because once they get say 20 or 30 of those aircraft turning and burning, you were not going to using voice com's!! And thanks for the comment.

Buck, Thank you too, I will endeavor to continue the illuminating content!!

BT: Jimmy T sends.

Reese said...

All this happens in a matter of 45 seconds or so, one after another right? Swell narrative. I got more out of this than from those documentaries on History or some such.

I like how you started: "Roll the jet to the cat. Attach cat. Shoot plane into the air." That's the impression most people have. My equivalent: "Get a reactor. Hook up a steam plant. Pull rods out. Make steam. Send steam to turbines to make screws go roundy-roundy." Well, it really is that simple in both cases. It's those pesky details....

I shot off the CONNIE ca. 1987 in process of PCS (sp?) from the CALIFORNIA (CGN-36) to CAPE COD (AD-43). Didn't know it was so busy under and around that C-2. Thanks, guys, if you're out there.

Anonymous said...

Great website, Jimmy, thanks for that. What I did not get: Does the holdback fitting / shearpins shear when the aircraft is shot (i.e. in the very beginning), or when the aircraft leaves the catapult (i.e. at the end of the cat shot)? Thanks so much!

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