The Effect of the A-7 Gun

The A-7 aircraft was armed with a 20 mm Gatling gun. The gun had six barrels, which were rotated at high speed by a hydraulically powered motor. The gun was physically located on the left side of the aircraft’s nose just aft of the engine air intake.

Before production aircraft were delivered to our government customers, the guns were test-fired on Vought property into a sand bunker. This bunker, or “gun butts”, was located near the flight line. The procedure was to park the aircraft at a firing point about 30 yards from the butts. The nose of the aircraft, and the gun, pointed toward the open doors of a small shed built on the sand. The shed served to keep down flying sand and anything else that might be kicked up by the impact of the 20 mm rounds. A portable hydraulic power unit, known as a “mule”, was connected to the airplane, as was electrical power.

When all was in readiness, a red flag was run up a small pole nearby to warn anyone in the vicinity of what was about to occur. Those participating in the test-firing retreated behind a barricade about 10 yards off the left side of the aircraft and near the nose, where they could observe the gun in relative safety.

A buzzer began sounding a series of loud beeps when firing was imminent. A few seconds later, the gun was triggered from behind the barricade and approximately 100 rounds of 20 mm ammunition was sent streaking into the butts.

The first time I heard the gun being test-fired I was taken completely by surprise, since I was in the flight line area on other business and didn’t know what message the sudden loud buzzer was delivering. I happened to be walking about 40 yards distant from the gun when it fired, and was at a position on the left side of the aircraft near the tail.

The noise of the gun going off was so loud I literally jumped about six inches into the air. I must have temporarily been in a state of shock, or at least confusion. It took a while for me to comprehend what I’d heard. The noise didn’t sound like anything associated with guns that I’d ever experienced.

The best description for the noise was that it sounded like a giant ripping an enormous sheet of canvas. The gun was capable of firing very quickly, and 100 rounds were gone in a fraction of a second. The sounds of the individual rounds being fired couldn’t be heard separately. The firings all ran together so fast that you experienced a single loud RIIIIPPPP!!

When my heart finally slowed down again, and my hands stopped shaking, I realized what a powerful weapon the 20 mm Gatling gun was. If it could reduce me to a bundle of wiggling jelly just from hearing it fire, I wondered at the effect on anyone so unfortunate as to be on the receiving end of it’s lethal messengers?

! * !

Will We Make the Guarantee?

The A-7 light attack aircraft was intended to be simple and easy to maintain. This was to be true even though it also contained some of the most sophisticated and up-to-date electronics of it’s day. The electronics made it possible to navigate more accurately, and drop bombs and shoot rockets and other missiles with greater precision than ever achieved before.

Because the company believed it could design and produce such a rugged, yet effective, attack aircraft, it agreed to a set of maintenance guarantees. These guarantees were developed after considering many factors, such as the state of equipment reliability design, capabilities of Navy maintenance personnel, the environment aboard Navy aircraft carriers in which maintenance would be performed, and many others. In the end, a set of maintenance guarantee values were put into the contract between LTV and the government. Bonuses for the company were tied to successful demonstration, while penalties would be assessed if values weren’t met.

One of the key guarantee values was the number of Direct Maintenance Man-Hours per Flight Hour (DMMH/FH). What this measured was how many hours of maintenance labor was required to keep the airplane in the air and flying for one hour. It had been decided that a value of 9.5 DMMH/FH was reasonable and attainable, and that was the guarantee value put into the contract.

Only the numbers being reported back from the first Navy squadrons to get the airplane were alarming. They showed that far higher amounts of maintenance labor were being expended. LTV management eyed the reports nervously. Would we make the guarantee? Or would we be paying penalties to the government, and explaining to a skeptical public and Congress why we couldn’t make the airplane perform as advertised?

After receiving reports for the first two months of squadron operations, an evaluation was made by LTV support specialists. If classical learning-curve theory applied, it appeared that reported maintenance could be expected to decrease over time. This would reflect increasing familiarity with the aircraft and it’s systems on the part of squadron maintenance personnel, and their native genius for finding ways to make maintenance procedures more efficient and effective.

A plot of expected DMMH/FH over time was generated, based on learning curve information from the first few months of squadron operations. This became the template of predictions, and was the standard of comparison each month when maintenance data was received from the Navy. As each month of actual maintenance data was plotted on the chart and compared to predictions, and as it became more and more apparent that squadron mechanics were becoming familiar with the aircraft, LTV management slowly began to breathe again. We would make our guarantees, and the A-7 would go on to establish a reputation as a reliable, rugged, accurate, and maintainable aircraft, beloved of both pilots and mechanics.

! * !

A-7E Maintenance Guarantees

The A-7 was meant to be a simple, rugged, and reliable airplane. But it would also carry the most advanced weapons of it’s day, and deliver them with an accuracy never before achieved. All of which required more complex electronics and systems than ever used on an attack aircraft.

If the aircraft was going to remain effective during battle, it had to be designed with inherent reliability. But even the most reliable equipment will fail sooner or later, and routine maintenance is always needed. Think of changing the oil in the family car, and checking the tire pressures, as examples of routine chores needed to keep it going.

To add extra motivation to the design team at Vought, the government customer added a “carrot and stick” to the A-7E contract. If Vought could achieve a certain level of maintenance performance for the airplane (measured in terms of maintenance man-hours expended per flight hour), a bonus would be awarded the company (the carrot). If the desired levels were not achieved, a penalty would be assessed (the stick). In this way the company was encouraged to use more reliable systems and equipment, and to carefully consider how best to arrange items in the airplane so that routine maintenance could be quickly and easily performed whenever necessary.

A group of engineers was devoted to reliability and maintainability (R&M) design tasks, and worked closely with hardware designers to make sure the airplane could be taken care of in service by the average Navy technician. The R&M group also kept a running estimate of their predictions for the level of maintenance performance the airplane would actually see when it went to the Fleet. This prediction was carefully compared to the contract requirements to make sure the company got the carrot, and not the stick.

The government customer wanted to demonstrate A-7E maintenance performance before the aircraft actually entered service. This would provide an opportunity to correct any problems before they got to the Fleet. Since there were essentially no Navy technicians available who could participate in the demonstrations, it was agreed that Vought R&M engineers would “act” as maintenance technicians. The government would send teams of observers with stopwatches to carefully record the amount of time required to remove and replace various items, and to do a variety of maintenance tasks. Other tests were used to demonstrate the reliability of equipment.

The demonstrations were all successful, and Vought received the carrots and avoided the sticks. When the airplane entered Fleet service, it quickly gained a reputation for both reliability and maintainability.