Re: Carrier Aircraft Catapault Hold-Back Bar / Mechanism ?



Jeff Crowell wrote:

"Mike Swift" <tomswift@xxxxxxxxxx> wrote in message news:tomswift-BDBE39.20585910062006@xxxxxxxxxxxxxxxxxxxx

In article <448a4c23@xxxxxxxxxxxxxxx>,
"John P. Mullen" <jomullen@xxxxxxxxxx> wrote:
snip

There is a short link that holds the traveler back. At launch, pressure
builds up in the piston until the link breaks, and woosh! The link
makes sure the traveler doesn't move unless there is sufficient pressure.


You guys! Don't post if ya don't know.

The purpose of the holdback is to keep the aircraft from moving forward
prior to the cat stroke. It holds back the AIRPLANE, not the shuttle
(what one poster called the "traveler"). If you can find a detail photo of a
carrier aircraft's nose gear, you will see, on the forward side, the nose tow
or launch bar. It is normally stowed in the 'up' position. Prior to launch,
the bar is lowered. The transverse knob on the end of the launch bar
engages with the notch at the front face of the shuttle.

In the good old days, the holdback was a machined bolt with a precisely
defined breaking strength. One end went into a socket in the aircraft
(various locations, usually in the fuselage), the other end went into a socket
on the holdback device, essentially a chain attached to the deck which
locked into a serrated track. These days, the hold back is a non-frangible
arrangement (broken pieces of holdback being a Not Good Thing on a
flight deck, not to mention one more thing to keep track of and replace).
Of course, in the good old days, there was no nose tow, the shuttle was
attached to the aircraft via a cable bridle which connected to rearward
facing hooks in the main gear wells. The non-frangible holdback is
essentially a spring-loaded socket (aircraft side) and a knob-ended
deck-side fitting with which it engages.

Whichever the design, the intent of the holdback is to keep the aircraft
from moving out of engagement with the shuttle. It goes like this:

As the aircraft taxis into the cat, the deck crew attaches the holdback
and the nose tow engages the shuttle. The aircraft comes up against the
holdback (gently! gently!), and the cat operator tensions the cat to take
out the slack. If the shuttle gets a running start at your flying machine,
you'll likely lose the nosegear. At this point it is possible for the cat to
fire at any time (not on purpose, but it can happen) so the driver comes
off the brakes and goes to military power. There's a brief process
where the pilot checks for excuses not to do this again (particularly at
night), while the deck guys check for loose panels, leaks and such, and
the cat is fired. The cat pulls the aircraft out of the holdback and away
you go. Launch power varies with aircraft type and loading.


Jeff




Well, that is that!

However, if the catapult is under power, whether the bold is frangible or not, could it prevent an underpowered launch?

Getting run over by an aircraft carrier is bound to ruin your day.

:-)

John Mullen
.