Warbird Information Exchange

A FRIEND OF MINE AND I HAVE A BET GOING SO HELP ME OUT HERE WITH THE CORRECT ANSWER. WHEN THE ARMORERS OF A FIGHTER ADJUST THE GUNS TO CONVERGE AT A CERTAIN POINT AHEAD, WHAT IS THIS CALLED????? IS THIS SYNCHRONIZING OR HARMONIZING??????
(BRAD, NO REMARKS ON WHAT THEY CALL IT IN TEXAS PLEASE!!!)
THANKS.....JACK

Synchronizing is for when the machinge gun fires through the propeller, other wise you don't need that!

_________________
Olivier Lacombe -- Harvard Mk.4 C-GBQB

I'm sitting here imagining the armorers in front of a F4U with the tail hoisted in a gun pit lined up and harmonizing like a barber shop quartet in front of the airplane. Not a pretty sight!

spare a thought then for the armourers working on beaufighters with, from memory, 6 machine guns and 4 cannons to work on then. or would the cannons be classes as the percussions section?

That's a full symphony! Awesome machine that Beaufighter. What's the progress on the one under restoration????

Hi,
It will also depend on what period you are talking about. In W.W.I, most guns were mounted on or in the fuselage / wing centre section, so there was no need to 'harmonise' the fire. However they (mostly) needed to be synchronised - in this case with the prop blades to be able to fire through the prop blade arc, but not the blades themselves!

The requirements changed in the 20s and 30s, and our skill at varying language between continents obviously has come into play. However I've only heard 'harmonise' in the Commonwealth that I can recall.

Beau. Slow but progress. It'll (as they say) fly when it's ready. And that'll be a day to look forward to!

Cheers

_________________
James K

"Switch on the underwater landing lights"
Emilio Largo, Thunderball.

www.VintageAeroWriter.com

Point of convergence is what you are really talking about. The armourer will set each gun on the aircraft with the necessary pitch and yaw offsets based on the gun location so that all the weapons fire to a single point at a specific distance from the aircraft. Then the sight is set so that a certain sized target fills a certain amount of the sight at the convergence point.

An exception is with the modern Gatlin type guns. In their case, the barrel installations have some shimming so that the firing pattern actually spreads from the muzzle rather than having a convergence point. Otherwise the Gatlin type gun would simply drill a hole through the target no larger than a couple of round diameters at the convergence point.

Craig C.

The gun on the F-15 and F-16 is offset from the centerline, so it actually is "harmonized" to a certain point. On the F-15E, our gun was set to cross the aircraft centerline at 2250'. The computerized gunsight operates in two modes -- one which computes aiming with the aid of a radar lock on the target (this is the most precise since it shows *actual* range and aspect to the target), and a second which approximates the target's airspeed and G based on ownship parameters (less accurate) and it is up to the pilot to pull the appropariate amount of lead (this is the "funnel" that you see in many of the fighter games out there). In both cases, the gun's offset location and trajectory are automatically factored into the pipper (or no-lock funnel) projected in the HUD. It's actually even more complex than that -- it even takes into consideration how the flexing of the aircraft under high G will change the physical position of the HUD with relation to the gun firing line and corrects the aimpoint accordingly.



I can't speak for other current fighter guns, but the "mil dispersion" of the M61 Vulcan is most certainly *not* intentional. Trust me, I would much rather have a gun can I could use like a "sniper rifle" instead of a "Stihl chainsaw" -- but that's not something that's possible in a hydraulically-operated gun shooting 6,000 20mm projectiles a minute. The bullet dispersion is due to the vibrations of that gun rattling around in the mounts -- mounts which allow some play because if they didn't, they would break when the gun was shot! So, the bullet dispersion is a result of the mounting requirement, and not the other way around as you suggest.