Hydraulic Upper Deck
The Martin Hydraulic Upper Deck Turret is the standard Navy installation for many flying boats. It can swing its guns a full 360° and protects the whole upper area of the plane with its deadly efficient cone of fire. There are several models, which for the most part are the same. The Martin 250CH-1 is used in a Martin "Mariner", and the Martin 250CH-3, in the Consolidated "Coronado". The Martin 250CH-2, which is almost identical with the 1 & 3, is the tail turret of the PBM-3D, and will be covered in a supplement to this section.
Facts and Figures
The turret can move 360°a full circlein azimuth.
The stowing position is 0° elevation and 180° azimuth, guns pointing straight aft.
Hydraulic Upper Deck Turret is one of the easiest to enter. First of all, before
you get in make sure that the deck turret switch has been turned to the
on position on the flight engineer's panel. Just outside the turret on a junction
box, conveniently located on a bulkhead, is a switch and a red indicator
light, which provides for turning "on" or "off" the power
to the turret. In the turret is a similar switch marked main power with
a red indicator light directly below it. In turning on the power it is
best to wait until you are in the turret, as the switch on the outside junction
box is to be used for emergency purposes only. Now enter the turret headfirst
from the rear of the ammunition box by climbing up the two steps, using a convenient
portion of the structure of the turret as a hand grip to help you. While standing
on the top of the ammunition box covers, reach down and pull the seat up until
it locks over the right hand seat support bar. Then look through the sight
to see if you are at the proper height. If you are not, get out of the turret
and adjust the seat. This is accomplished by pinching together the pins
in the seat support bars, which are located on each side of the seat, and raising
them to the next holes above or below. On completion of this, climb back into
the turret. Fasten the safety belt and you are now ready to operate.
OPERATING THE TURRET
. Where to Find the Controls
the Martin 250CH Turret into operation is a relatively simple job.
On the left side of the control panel you see another switch all by itself,
marked pump motor switch (C). Raise this to the on position. Lift
the little red plastic cover on the right side of the control panel and flick
the gun-end-sight switch (D) to the on position. The control
handles are located below and back of the breast plate in which the control
panel is mounted.
|Using Auxiliary Equipment|
The oxygen system The turret oxygen system is connected to that
of the airplane through a swivel joint in the base of the turret. The system consists
of a rebreather unit, a cannister, and a nose piece. The rebreather is mounted
on the right side of the magazine under the expended ammunition container. The
cannister is located on the outboard side of the right ejection chute casting
and is connected by a flexible hose to the oxygen mask. However, you will find
in many of the existing PBM and PB2Y airplanes that the oxygen system has been
away with, because it is not necessary for these airplanes to fly at high altitudes
while on patrol. The cord to the heating suit is plugged into an outlet
on the junction box, which is located directly above your left foot. This is turned
on at the control panel by the utility switch (E). The interphone jack
box is attached to the right ejection chute casting. This is where you plug
in your jacks for your headphones and throat microphone. On the front of the box
is the "push-to-talk" button that operates the interphone system when
you wish to speak. Two trouble lights of the spotlight type are mounted
on ribs from the top of the dome, one on either side of the escape hatch. A ball
swivel joint on each light enables you to direct the light in any direction desired.
The dome light switch (F) is located on the control panel.
|Provisions have been made for installation of a gun camera on the left
side of the sight. To put the camera into operation it is necessary to have the
camera switch (G) and the main power switch "on", and the trigger
and safety switch depressed.|
In the event that the power fails, a manual azimuth drive is provided so that you may rotate the turret. The drive crank is stowed on a spring clip mounted on the aft face of the left ejection chute casting. Remove the crank from the clip and insert it in the hole on the right inboard side next to your right knee. This ties the crank directly into the azimuth gear mechanism. Turning the crank one way or the other moves the turret in azimuth. You will find the crank extremely helpful in testing the fire interrupter and boresighting the guns when a slow, carefully controlled amount of azimuth movement is necessary.
Before going back to power operation be sure to remove this azimuth manual crank. If you have it engaged it will whirl around and may break your hand or leg.
No manual elevation mechanism is provided in this turret. However, in models which are about to be produced, manual operation will be provided for both elevation and azimuth.
Preparing the Turret for
The Navy Mk 9 sight fits into the gun sight bracket directly behind a 1/2" armor plate which protects your face. To adjust the sight, as it may be sometimes necessary in harmonizing it with the guns, make the adjustments on the sight head. For full instructions see the section on the Mk 9 sight in the general introduction.
|Adjusting the Guns|
The guns are mounted in the Martin Ball to feed from the inside-the right gun feeds from the left and the left gun feeds from the right. Each gun is installed with an Edgewater E-10 adapter and is bolted to the front and rear mounts in the gun cradles.
|The guns may be adjusted up, down, or sideways in their cradles by means of an adjustment nut assembly which is locked into place by jam nuts. An elevation adjustment nut controls the up and down movement. An eccentric nut controls the sideways motion.|
|Harmonizing the Guns and Sight|
There are a number
of ways to harmonize the guns and sight in the Martin Hydraulic Deck Turret. The
exact procedure will be defined by the Squadron Gunnery Officer. A handy method
is to line up the sight and boresight the guns on some small object, such as a
tree or chimney, at least 1000 yards from your plane. To do that remove the back
plates and bolts from both guns, or use a boresight tool so that you can look
through the gun barrels without removing the parts. Turn the turret until the
guns point at the object you have selected.
method of harmonization is to line up the sight and guns on a special pattern
stand, or template, such as the one illustrated here. Set up the stand as level
as possible at least 50 yards from the side of the plane. Center the guns in their
mounts. Then boresight each gun on the pattern stand and center the sight on the
sight cross, using the standard technique described in the Sights and Sighting
section of this manual. Both methods described here are parallel harmonization.
Martin Hydraulic Upper Deck carries its ammunition in two built-in magazines,
separated by a steel partition and mounted under the feet of the gunner. These
double magazines are loaded through sliding removable doors on top and hold 600
rounds of .50 cal. ammunition for each gun. The top of the ammunition box and
the removable doors also serve as a footrest for the gunner. To load the magazines:|
1. Remove the foot plates at the top of the ammunition box. This is done by pulling the spring-like pin under the footrest panels and then skidding the foot plates aft and off.
2. Remove the forward and aft pins of the feed chute. Remove the chute.
3. Load the ammunition belts by flaking them back and forth across the magazine.
When ammunition boxes are full reinstall the feed chute and its pins.|
5. Lower a wire hook or an ammunition thread sling down the top of the booster feed and through the feed chute attaching it to the ammunition belt in the magazine.
6.. Reinstall foot plates at the top of ammunition box.
7. Pull each ammunition belt up through the chutes until one or two rounds of ammunition are engaged in the booster sprockets.
8.. Lift the cradle cover and gun cover. Pull enough ammunition to be loaded into the guns.
9. Close the gun covers and cradles.
|Removal of Empty Cartridge Cases and Links|
either side of the seat, attached under the azimuth track, are the expended ammunition
containersone for each gun. To remove the empty links and cartridge cases,
slide down the access doors on the back of each container after pushing in the
latching catches on the access doors. Clean out the empty cartridge cases and
links. Replace the access doors.
. . . FOLLOW STEP BY STEP1. Install the barrels and oil buffer groups in the gunsleaving out the bolts and back plates.
2. Check harmonization of the guns and sight by boresighting on pattern stand or some other object 1000 or more yards away.
3. Make sure the bolts are assembled properly to feed from the right for the left gun and from the left for the right gun. Install bolts and replace back plates on both guns.
4. Try to rock the guns in their mounts to make sure they are securely mounted. Check to see if the adjustment and jam nuts are properly safetied.
5. Check filler valve. It should be in the "RUN" position and safety wired.
6. With the pump in operation, operate the gun charger valve knob in both "SAFE" and "FIRE" positions.
7. Inspect the hydraulic system and lines carefully. This should be done with and without the pump operating. If there are any leaks, report them immediately.
Inspect electrical leads and flexible conduits (Breezes) to determine
if they are frayed or damaged.
Check for "line knock" (air in hydraulic system) while operating
turret in all extremes. If any is noticeable, report it to maintenance man.|
16. Operate the turret in elevation to determine if the limit stops are functioning properly.
17. With the guns completely depressed, carefully rotate the turret to determine if the structural interrupter keeps the guns from swinging into the fuselage.
18. Insert a test light in place of electric trigger control, and with triggers depressed, rotate the turret across the portions of the plane into which the guns could fire. The test light will go out in this area. With a boresighting tool, check the distance from the surface the interrupter cuts out.
19. Turn on the sight and gun switch, depress the safety switch, and rotate the sight rheostat from dim to bright to adjust the brightness of the reticle to existing light conditions. Make sure the reflector plate of the sight is clean.
Plug in your headphones and microphones to test if your crew mates can hear you
and you can hear them.
The Martin Hydraulic Tail Turret
There is little difference between the Martin 250CH-1 and 250CH-3 Deck Turrets and the Martin 250CH-2 Turret used in the tail position of the PBM-3D airplane. Both types are operated exactly the same. The information on the following page will outline the major differences between the two types.
Facts and Figures
In elevation it can raise its guns 65° above horizontal and depress them 45° below horizontal.
MARTIN TAIL TURRET
Keep your feet on the foot brackets at all times while operating the turret or it is possible that you may get them jammed between the turret and the structure of the ship.
all times while operating the turret or it is possible that you may get them jammed
between the turret and the structure of the ship.
BEFORE-LANDING and AFTER-LANDING procedures are exactly the same.
The Consolidated Tail Turret
The Consolidated tail turret is a double stinger
in the tail of the PB2Y-3 Coronado and the
Facts and Figures
The turret moves in azimuth about 75 degrees to either side of the ship's centerline from almost straight out to the left to almost straight out to the right.
The stowing position for turret and guns is 180 degrees in azimuth and 60 degrees in elevationguns pointed back from the tail and two-thirds of the way between level and straight up.
Getting InWhen you step into the Consolidated Tail for the first time, approach it with care. Unless the turret is properly locked, it may swivel and trap a man trying to go through the doorway. The method of getting in illustrated on this page is the only safe way—follow it step by step.
And remember, as you get into the turret for your first look around, that ordinarily you would enter only after the bomber is in full flight, and would get out before the landing. Quick changes of speed during takeoffs and landings make any tail turret an extremely dangerous place to be at those times.
Opening the turret doors
Reach into the turret and make sure that the main shut off valve, a red spindle knob to the left center, is closed. The valve should be turned all the way in. If it is open, a mere touch on the control handles might set the turret moving and trap you in the doorway. Always make sure the main shutoff valve is closed before entering or leaving the turret.
Grasp the two handles just above the doorway, and, chinning yourself, swing both feet straight into the turret pit. Then get into the seat.
Pull down on the door cable, by grasping the red knob on your right, to close and lock the doors behind you. Be sure the doors are tightly latched.
OPERATING THE TURRET
. . where to find the controls
|Close at hand, as you sit in the Consolidated Tail, are all the switches, valves, and controls. They are easy to get at and easy to use. But be sure to turn on the switches and open the valves in the order shown here.|
1. Open the main shutoff valve.
Turn on the power switch (A) on the junction
Grasp the control handles directly in front of you, and you are all set to go. To move the turret, turn the handles just as you would steer a bicycleto the right to go right, left to go left. Press down on the heels of the handles to raise the guns. Pull up on them to lower the guns. The other controls you will use in combat are close at hand.
The triggers (A) are on the control handles, right under your index fingers. The push-to-talk button (B) that opens the interphone system for you to speak is on the right handle, under your thumb. A set of reset buttons (C) protecting the main electrical circuits is mounted on the side of the junction boxeach button labeled with the name of the circuit.
The charging handles are on either side of the bulletproof glass in front of you. To charge the guns, reach forward and grasp the handles cross-arm, holding the left handle with your right hand and the right handle with your left hand. Pull back on them sharply as far as they will go. Don't ride the cables on the return action. Still holding the handles, allow them to snap back on their own power.
Using the Auxiliary Units
will find a demand type oxygen regulator (A), with hose connection for your mask,
near your left shoulder. The oxygen supply is drawn from the ship's central tanks.
To change to manual operation:
Close the main shutoff valve. Open the bypass and emergency release valves.
Always push the foot-firing mechanism lock DOWN into its locked position after manual operation. Never charge the guns unless this lock is down.
When you get out of the turretbefore the landing if you are on a flightbe as careful as you were when you got in. Remember that the doors can trap a careless gunner on the way out as well as on the way in.
First move the turret to stowing positionguns pointed back and to 60 degrees elevation. Then turn off the sight, trigger, booster motor, and mam power switches on the junction box. Close the main shutoff valve, and replace the azimuth and elevation mechanism locks which you removed when you got in.
The turret is now locked in place. Open the doors by pulling the cable on your right and step out. Then close and latch the doors behind you and turn off the main power switch on the fuselage wall.
the Turret For Combat|
With the practical data in the preceding pages, you could take over the Consolidated in combat. However, that will be only part of your job. The rest of your jobharmonizing the sight and guns, and loading ammunition ready for a missionis explained in the following pages.
Adjusting the Guns
The guns are mounted in the Consolidated Tail to feed from the insidethe right gun from the left, the left gun from the right. Each gun is held in its cradle by a rear trunnion block and slide and a front trunnion stud bolted into a mounting hole in the cradle. The rear trunnion block, attached to the gun, dovetails into the slide mounted on the cradle; check to make sure the block fits. The front trunnion stud is held by a lock nut and cotter pin. Special charging units are installed on the inside plates of the guns' receivers, and link ejection chutes on the outside. Make sure that the bolts mounting the charging units are safety wired, and that the cable connections have cotter pins. Special foot-firing mechanisms are mounted on the outside of the guns and connected to two foot-firing pedals. The pedals operate plungers which trip the sears in the guns. When you assemble the bolts for the guns, make sure the square ends of the sear slides are on the outside of each gun. Mounting bolts on the foot-firing mechanisms must be safety wired. The guns are adjusted up, down, or sideways in their cradles by rear mount adjustment collar and lock nut assemblies.
|To make adjustments
on either gun:|
1. Loosen the front and rear trunnion lock nuts.
2. Turn the top lateral adjustment collar right or left to move the rear of the gun from side to side.
3. Turn the bottom vertical adjustment collar right or left to move the rear of the gun up or down.
4. Tighten the lock nuts. By means of these adjustments the guns can be centered in their mounts. Simply turn the collars to the approximate centers of their lateral and vertical adjustment movements. A little practice will enable you to do this quickly and accurately.
Harmonizing the Guns and Sight
There are a number of ways to harmonize the guns and sight in the Consolidated
Tail Turret. The exact procedure will be defined by the Squadron's Gunnery officer.
A handy method is to line up the sight and boresight the guns on some small object
such as a tree or chimney at least 1,000 yards from your plane.
|The ammunition cans, one for each gun, hold about 400 rounds each. They are outside the turret in the fuselage of the plane, and the ammunition belts feed through flexible guides up through the floor of the turret to the guns. To load the guns, first pull the ammunition belts up through the floor of the turret, double-link end up. Drape them forward over the booster motor cylinders and sprocket wheels, making|
the rounds rest evenly in the sprockets. Then twist the belts slightly and curve
them up over the feed chutes to the guns' feedways. Just before the takeoff, press
the first links of each belt into its feedway, and the guns are ready to be charged
. . . FOLLOW STEP BY STEP
Install the guns' barrel and oil buffer groups in the gunsleaving out the
bolts and back-plates.|
2. Check harmonization of the guns by boresighting the guns on some small object 1,000 yards away, or on a pattern stand.
3. While harmonizing the guns, make sure the manual system of operation is working properly.
4. Make sure the gun bolts are assembled properly, to feed from the right in the left gun and from the left in the right gun. Also make sure that the square ends of the sear slides face the outside of the guns. Then install the bolts and backplates in both guns. Replace the gun access plates.
5. Try to rock the guns in their cradles to make sure they are securely mounted. Check to make sure that the front and rear trunnion mounting studs and bolts are safety wired.
6. Check the hand charging units on the inside of the guns and the foot-firing mechanisms on the outside of the guns to make sure they are securely attached and their mounting bolts safety wired. The cable connections to the charging units must have cotter pins.
7. Inspect the hydraulic system and lines. If there are any excessive leaks, report them.
8. Inspect the electric cables. Make sure all cannon plug connections are tight. Report any frayed or damaged cables.
9. Check the oxygen connections.
Make sure the Plexiglas dome and bulletproof glass are clean.
motors by tilting the boosters toward the guns. Make sure the motors cut on and
off sharply, without lag.|
17. Turn off the trigger switch and test the foot-firing system by opening the foot-firing mechanism lock and stepping on the foot-firing pedals. Listen for a click as the plungers operate the guns' sear slides.
18. Remove the azimuth and elevation mechanism locks from the shafts and place in their clips. Make sure these locks are removed before trying to run the turret.
19. Open the main shutoff valve, turn on the power switch, and run the turret under power in azimuth and elevation, to check on ease of operation. Make sure the turret operates with either safety switch held down. Run the turret as far to the left and right as it will go to make sure the limit stops halt the guns before striking the plane. Stop the turret and check for creep.
20. Put on your oxygen mask, connect it, and test by turning on the direct flow valve. Check the gage to make sure there is proper pressure, in the tanks, as determined by your crew chief. Close valve.
21. Plug in your headphones and microphone
to test whether your
crew mates can hear you and you can hear them.
and ammunition cans.