Nerve Center of a Fortress

By Major Allen V Martini, USAAF

The instrument panel of a huge B-17 is a throbbing, pulsing register of performance for the keen eyes of the pilot and crew chief who know where to look.

One of the most intricate, complex, and interesting aspects of all flying, both to the pilot and to the layman, is the instrument panel. Probably all of you have seen the apparent maze of instruments in a four-engine bomber, and, while it seems bewildering at first glance, to an experienced pilot, those instruments tell a story — sometimes a dramatic one!

First of all, the instrument panels we have on our Flying Fortresses present four times as many problems as those on a single-engine ship. Thus, the need exists for a heavy bombardment pilot to pick up as much theoretical engineering knowledge as possible and to apply it to practical use. After becoming a first pilot in a ship such as a Fortress or a Liberator, that seemingly complex array of dials becomes as easy to read as a primer. There is a dial on that board which offers a visible report of the functions of each and every mechanical and electrical part. Probably the most important ones are the gas gauges, manifold pressure indicators and the RPM tachometer.

In order to go through the procedure necessary for the preparation and accomplishment of a bombardment mission over Europe, let's start at three-thirty some rainy, cold English morning. The crew chief, usually a tech or master sergeant who is the real "daddy" of the airplane, although he doesn't fly on a mission in it, comes out with his ground crew of instrument, radio, prop and armament specialists and mechanics. Each man knows his job thoroughly and goes ahead without any hesitation. It takes about five men on the ground for each one in the air.

The crew chief gets into the cockpit with one of his mechanics. Some of the other ground men take hold of the 12-foot blades and pull them through, to clear any oil that might be in the lower cylinder of the engine from standing over night. A portable battery or generator cart is plugged into the ship's electrical system, the props are cleared and the man in the cockpit turns the engines over one by one. They break into a powerful throaty roar. The crew chief is cautious, however, when first starting the engines so as not to exceed the manifold pressure considered maximum for first starting the engine on the ground. This is to prevent injury to the engine as the oil is still cold.

After letting the engines warm up gradually, the sergeant and his assistant check to see that cylinder head temperatures are high enough, oil pressure is up, and the oil temperature is right. On some of the indicators there are two hands, so that a single indicator can show the operation of two engines, thus eliminating two instruments.

If everything checks okay, the crew chief opens his throttle up to about 1700 rpm on the engine he is checking and checks both his magnetos for any drop in rpm. If these check correctly, he runs his prop controls down to low rpm and then back up into high rpm, changing the angle of the blade and activating the mechanism in the prop dome, bleeding out any air that might have accumulated in the system. Then the manifold pressure is further raised to the maximum allowable for ground operation, held up for a few seconds to clear the engine and check maximum pressure, and then lowered to idle speed which would be about 12 rpm. This procedure is followed through on all four engines.

In the meantime, another mechanic is checking the fuel, the hydraulic emergency system, wing and prop deicer systems, and the electrical system, but even though he is busy with his specific checks and the crew chief with his, their eyes flick across that panel and take in every dial — each tells an all-important story.

In the meantime, the other specialists are checking the radio equipment, the bomb releases, the bomb shackles, the guns, ammunition, and power turrets; and in doing so, they apply the power that will be employed under actual combat conditions to see just how well the system is regulated, in order to withstand the bleeding of the system and renewing all that power. If all these routine checks fail to disclose flaws or malfunctions in the intricate mechanism that constitutes a Boeing B-17, it shouldn't take more than forty-five minutes to an hour to prepare it for flight.

About this same time, the combat crew, the pilot, co-pilot, bombardier, navigator, radio man and the gunners are being "briefed" for the mission. First of all, they get a general briefing, which everybody attends in the main intelligence room. The target, anti-aircraft defenses, fighter defenses, weather and general information are divulged. Then each group, such as the pilots and copilots, will file into a separate room, the gunners into another and so on, and specific briefing then takes place in which the individual problems of each member of the crew are discussed and settled upon.

By this time, probably, the sun is about to rise and one can see the grotesque figures made by the men climbing into trucks or clumping down the taxi strips in their bulgy flying suits, with parachutes, head sets, life vests, escape kits and confidential radio material.

When they arrive at their ships, they immediately disperse in the various parts of the ship they regard as their own personal domain. They double-check their equipment and give it a minute inspection in order to insure a hundred per cent efficiency when an emergency arises and the fighting is hottest. The bomber had already been loaded the night before, but the men clean their own guns and load their own ammunition. They don't want anyone else touching that equipment, because it is "life insurance" to know that mechanical perfection has been attained. The bombardier installs his own bomb-sight, checks all his bomb-bay racks and equipment and then proceeds to take care of his own gun, because he is required to be a gunner when he isn't actually bombing the target.

The pilot, in the meantime, checks with all his formation leaders on the procedure for assembling, formation, attack on the target, and return to home base. Then, as daylight breaks into full glow and the hour of takeoff approaches, the crews get their last minute instructions from the pilot, help each other into the cumbersome equipment and take their places in the ship. There is an air of tense expectancy which is relieved somewhat by the first powerful roar of the engines as they start, one by one, under the hand of the pilot.

When he gets into the cockpit, the co-pilot immediately checks the fuel supply, as every ounce of gas in the tanks may make a difference going out or getting home. The pilot turns on the battery switches, the main line switch, fuel boost pumps, cracks his throttles and then indicates to the co-pilot when to energize the starter motors in each engine. In twenty to thirty seconds he signals for the copilot to engage the starter motor, the tremendous prop turns over, and the co-pilot pumps a hand primer which shoots raw gas into the cylinder and aids in igniting the charge and turning the engine over.

Then an instrument check is made as each engine is started, just as was made in the preflight runup by the crew chief; and the engines are tested in the same manner to doubly insure proper operation. Now all the ships on the field that are detailed on the mission have roared into life and seem to be champing at the bit, waiting to roll out of their revetments and line up on the runway, ready for the take-off. Finally the signal comes from the control tower and the hulking monsters trundle slowly along the taxi strips around the field. As each squadron comes into position on the runway, the crew and the ships seem to be leaning forward eagerly, expecting that first "lift" as they are freed of the encumbering ground in their element which they know so well.

When the sweep hand on the commander's watch flicks that last second the tail wheel is locked, the throttles are opened and given the initial momentum and more manifold pressure is applied by opening the throttles until the maximum pressure is reached. Throttles are then locked and the pilot concentrates on keeping the ship straight along the runway so as to avoid any unnecessary prop wash for the ship behind him. He then picks the compass course that he will hold for the formation assembly, and now comes that sudden surge by the airplane, as she seems to lift her wings and she's alive and free, doing the .job she best performs.

The lead ship goes out so many seconds and then manifold pressure and RPM are reduced to minimum cruising rate to enable the other ships to move into their appointed places. Then procedure turns are made and every fifteen seconds a wing ship slides into its position in the squadron. Once the squadron is assembled, the groups are next assembled by combination of three squadrons, each group then assembles with other groups to make up one combat wing and then into air divisions.

Normally, under good weather conditions, the assembly is completed easily and smoothly but when an overcast, or bad weather presents a problem, radio beacons are utilized and the ships can do practically the same job through the mathematical precision which is born of the confidence in each pilot and the team that a group of pilots form; plus confidence in their flight instruments and various other indicators which are necessary to the completion of this problem.

The assembly accomplished, the formation now heads out on a predetermined course to the target. The co-pilot, when not helping the pilot fly formation, is checking on the gyro-compass, the flight indicator, manifold pressure, rpm, oil pressure, oil temperature and cylinder head pressure. Also, par t of this check takes in generators, the interphones, the radio system and the outside temperature, and perhaps the automatic pilot. Also, the good copilot will continually check his fuel indicator and the consumption of the engines. The wing ships in a formation usually burn up more gas than the lead ships, because of constant changes in manifold pressure while holding their position in formation.

Of course, both the pilot and the co-pilot keep watching the clock because there's a saying, "On the way out to a target, we work for Uncle Sam; on the way back, we work for home and mother!" and the boys want to know what time to quit working for Uncle Sam!

One of the most important visual indicators comes into play as the formation climbs, because the men don their oxygen masks around nine thousand feet and it is a matter of life and death when they check that little red ball which bobs around as if in an hourglass, showing their steady and rhythmical breathing, as the oxygen flow takes care of the requirements of the lungs.

Now we approach the target area and the navigator and bombardier become the two most important members of the team. The navigator continuously checks his time and coordinates his work with the bombardier, who has pre-set all necessary data into his bomb-sight. Between the two of them, they plan the approach and the axis of attack, in regard to the target itself. Now the target is sighted and the grim business that the Fortress is built for becomes evident. The bomb-bay doors are opened, the ship swings on course for the actual attack, the bombardier synchronizes on the target and makes any last minute correction; he and the pilot exchange terse and flip words over the interphone. When the bombardier synchronizes on the target, he also turns on the pilot-direction instrument in the cockpit, immediately in front of the pilot, which will give any variations in course; the pilot corrects with the rudder, elevator, or throttles, to maintain the desired course as shown by that little needle.

Finally, the fluctuations of the needle are narrowed down; the desired course and level flight attained. One last new correction is made and, suddenly, the little red lights around the instrument flicker and the exultant shout of the bombardier is heard over the interphone, "The bombs are away!"

Quickly the bomb-bay doors are closed, the ships turn away from the target, reform their combat wing, and set out for their home base. Now they' re working for "home and mother" and although they are still alert for attack from enemy fighters, there is the general satisfaction of knowing the mission has been accomplished. If no opposition is encountered, the return home is uneventful; the ships circle their field and land at given intervals, taxi slowly with screeching brakes to their own little parking space, and then with a tired cough, the engines die as the pilot cuts the throttle and switches. A great sigh seems to come out of the ship, but immediately the ground crew swarms over it again to check her vital systems, noting any damage or malfunction, so as to regulate or repair her, and have her ready to do her job again, come another day!

This article was originally published in the February, 1944, issue of Flying Aces magazine, vol 46, no 3, pp 32-33, 66-68.
The PDF of this article [ PDF, 8 MiB ] includes a photo of the author, a photo of the cockpit of a B-17, a photo showing a B-17F with a bomb train in front, and a legended photo of the instrument panel of a B-17.
Photos credited to Acme (author), Boeing Aircraft Co (cockpit and panel); flightline photo not credited.