Helicopter Maintenance
Events Diary

Naval Air Test Center
1971 to 1972

The Naval Air Test Facility at Patuxent River, Maryland evaluates new aircraft and aviation systems for the Navy and Marine Corps. The Navy Test Pilot School located at Patuxent provides the pilots that fly the aircraft being evaluated. The Test Facility is the intermediate authority between civilian builders and fleet acceptance by the Navy and Marine Corps. New aircraft and aviation systems must meet government contract specifications before purchase. Project officers normally accomplished their tests by installing recording instruments in project aircraft and flying the envelope for each specification. Most of the flying is done over the adjoining Chesapeake Bay test range. The Test Facility was a busy place with lots of activity during the Vietnam War. New aircraft at that time were the UH-1N with the T400 power pack, the F-14 Tomcat and a smaller Osprey type aircraft built in Canada. New equipment being tested was the H-53 mine sweeping system, night vision technology and rigid and elastic rotor drive systems.

Experimental aircraft are designed and built by aircraft builders to compete with other aircraft builders for new government contracts. The Sikorsky aircraft below is a weapons platform built on a modified H-3 airframe. It looks a little like the AH-1 Cobra, but bigger. This aircraft was a test bed for new rotor head technology for helicopters. It demonstrated a 360 degree roll capability during tests. The other aircraft below is the H-34 with the T400 power pack. Sikorsky was importing old French Army H-34 helicopters that where supplus equipment in France. They didn't fly anymore and I'm sure Sikorsky purchased them at a good price. They rebuilt the airframes and installed new T400 power packs. It's a great commercial aircraft today. Sikorsky would run the engines at the factory in the aircraft without the blades. You test everything that way except flight. We did that once with an H-46 during the bad blade days. The crew chief gave the pilot the signal to taxi, but the aircraft didn't move.

Aircraft maintenance is important to everyone that flies. A fundamental principal of aircraft maintenance is the elimination of mechanical failure in flight. The idea is to replace or overhaul components before they fail. Many aircraft components are replaced or overhauled half way through their normal life cycle. The time it takes components to fail will vary between aircraft types. Commercial airliners have a long time between component failures because of their design and use. The opposite is true of helicopters. Helicopters live in dusty, dirty areas close to the ground where they operate a large revolving mass creating lift and directional control. Helicopters are more complicated than fixed wing aircraft when it comes to basic flight. The President of the United States flies in Marine One. This H-3 helicopter is a vintage Navy helicopter flown and maintained by Marine Corps personnel. This combination of maintenance, hardware and responsibility is the best way to eliminate mechanical failure. This is a good example of perfect maintenance. The other extreme is the detachment concept. That's where you operate one or two helicopters at some remote site and accomplish a mission from that location. This is similar to sending a helicopter cross-country with a ferry crew. It normally takes a long time and several crews changes to make it from one coast to the other. Mechanical failures, parts and getting qualified personnel to the repair site are the main problems. Maintenance on a ferry mission is normally safe because the mission is flexible and has a low priority. If you have a high priority mission like the President of the United States, you need perfect aircraft and perfect maintenance. Detachments with weak maintenance should have low priority missions of short duration.

The 53s that didn't make it on the Iranian hostage mission were the same aircraft that removed the mines from the Suez Canal a few months before. The Navy didn't experience availability problems during their mine removal mission. Their aircraft were old H-53A models equipped with extra fuel tanks and modified for the mine sweeping mission. The Navy was flying off a ship anchored in the Mediterranean Sea close to the Canal entrance and was doing most of their organizational maintenance on the hangar deck. Most of their 53s came back from the Canal in a down condition. The Navy Squadron repaired or cannibalized parts for the next launch and did most of their maintenance at night. The only aircraft that didn't make it back to the boat was one that hit a flag pole at the Alexandria International Airport. The tails fall off 53s when the main rotor has sudden stoppage. What was the differences between the hostage and mine sweeping missions? The obvious one was that the hostage mission needed perfect long range aircraft. The mine sweeping mission was successful because they didn't need perfect aircraft. They had the time and the place to repair their aircraft after every mission.

The military services would like to eliminate mechanical failure in all aircraft. The design of military helicopters and their associated reliability has improved over the years, but the machines have become more complicated. The fact that you can land a helicopter almost anywhere gives us a great military advantage, but remote maintenance on complicated aircraft will always be a challenge.

A perfect place to see the balance between aircraft maintenance and the operational mission was at the Test Facility's Helicopter Maintenance Department. Department personnel consisted of ten Navy and Marine technicians qualified in SH-2, SH-3 and CH-46 aircraft. Project officers would hire factory mechanics now and then for short periods of time if project money permitted. The Test Facility was flying models of the UH-1, AH-1, SH-2, SH-3, UH-34, CH-46 and CH-53 aircraft. The accident rate in early 1970 was one aircraft per month from all causes. The department was organized as a general pool of helicopter maintenance personnel that worked on everything. The paper work suffered from the lack of organization and they made mistakes.

As a solution to the accident problem, helicopter maintenance was reorganized into a typical aviation maintenance department with individual responsibilities assigned to different shops. Some shops only had one technician. A shop would use personnel from other shops during most maintenance events. An engine mechanic could work on an air frame discrepancy, but the primary shop was responsible for the repair procedure and the paper work. This system maintained the integrity and safety of the maintenance effort in this unusual environment. An exception to this practice was our quality assurance procedure. The Quality Assurance Department at the Test Facility was a large department that served both fixed and rotary wing aircraft. Highly qualified fixed wing inspectors unfamiliar with helicopters did helicopter inspections. This is another weakness in the small detachment concept. Inspectors should be the best individual in their field and also the best individual in their type of aircraft. The parts supply priority for the Test Facility was near zero during the Vietnam War. A stub wing OV-10 could get pilot flight time and a part for us at the same time if we could locate the right part in the supply system. Parts were a serious problem and maybe the slow parts availability matched the size of our maintenance department. It may have been a good thing. Aircraft availability was sixty five percent most of the time. Availability could have been better had we been able to cannibalize parts between aircraft. You can't cannibalize if you only one aircraft of each type.

The Department's Navy, Marine and civilian personnel were professional aircraft maintenance technicians. Doing major maintenance on a weekend for a test hop scheduled for Monday was not uncommon. Our Navy technicians were senior people that did hands on aircraft maintenance. The factory technicians would come and go and they didn't do paper work. The factory people were good with their hands and they had all the necessary skills. Our factory technical representatives didn't do maintenance, but they were a valuable source of technical information.

One project that didn't work very well was the first mine sweeping sled installed in an CH-53D. The Test Facility was using a Marine Corps CH-53D with factory technicians. A sled is deployed with a winch and cable by the crew chief. The aircraft pulls the sled through the water and then recovers the sled with the same winch. The project officer installed a hydraulic winch that was designed to anchor blimps to their mooring masts 30 years before. It was surplus equipment and the price was right. On the first test, the aircraft hovered in position 100 feet over the runway and deployed the sled. The sled crashed to the ground and was destroyed. Blimps were recovered in the old days by pulling them into their mooring masts. The winch would free wheel in the opposite direction. They solved the winch problem before testing the second sled.

Factory owned aircraft would visit the Test Facility for demonstration or test purposes from time to time. A factory H-53 was departing the air station when the aircraft declared an emergency. The pilots didn't taxi the required distance in a forward direction to position the nose wheel before retracting the landing gear. When they retracted the gear, the nose wheels wedged half way inside the aircraft. They couldn't lower the landing gear and they couldn't land. The solution to this problem is to hover 5 feet over the deck and have a technician deflate the nose wheels. When the tires are deflated, you can lower the gear and re-inflate the wheels. Doing that work on high pressure tires with a big helicopter moving up and down over your head is very difficult and a little dangerous. The Navy technician under the aircraft received a well deserved meritorious mast for his efforts.

We had to replace an engine in our resident H-46. The H-46 was parked outside our hangar in the same position as the H-34 T400 above. The new engine was installed and we were ready for a test run. A pilot did his preflight and then started the old engine. Everything worked fine. The new engine went to the start position and then the aircraft produced a stream of fire similar to an Mig-15 on afterburner. The fire stream had a length of fifty to sixty feet and burned the grass on the hill behind the aircraft. The crew chief gave the cut signal and the pilot shut the engine down. We all had big eyes when we saw that much fire coming out of a H-46. The problem was an engine oil seal installed backwards. Pressurized engine oil bypassed the seal and was burned in the engine. We replaced the engine again and that solved the problem. Why didn't the first engine fail on the engine test stand before issue? I bet they changed the seal and didn't run the engine. Everything that's repaired by human beings should be tested before issue and use.

The Marines assigned to the Maintenance Department were all Vietnam veterans with lots of aircraft maintenance experience. They were professional mechanics and technicians that could do it all. In Vietnam they stood perimeter guard with grease guns and hand grenades one-week and then rebuilt engines and hydraulic systems the next. No mistakes or errors were acceptable. Lives depend on the quality of their work. We obtained one of these exceptional young Marines for a very important project. Sergeant Henderson came from the Marine Corps Presidential Squadron, HMX-1. He volunteered for temporary additional duty as crew chief on an old Marine Corps Reserve CH-53A. The Test Facility was doing artificial vision testing using a helicopter platform and needed an aircraft and crew. It was a joint Army, Navy and Marine Corps project that was the beginning of night vision technology for helicopters. The Marine Corps portion of the project was Sergeant Henderson and his Marine Corps Reserve CH-53A.

The aircraft looked bad and needed to be modified for the project. The aircraft had cockpit seats and a set of flight controls installed in the main cabin. A test pilot would fly the aircraft from that position using a television receiver for visibility. An external television camera was mounted in the forward nose area. Some of the receivers were very small and attached to the pilot's helmet. The project evaluated the pilot's ability to fly large helicopters using artificial vision equipment. Flying in the cabin was similar to flying under the hood without instruments. Two other pilots flew the aircraft from the normal position during routine flights. There were lots of jokes about back seat drivers.

Sergeant Henderson was the only qualified CH-53 maintenance person at the Test Facility. The pictures below were taken after the Sergeant's aircraft came back from a Naval Air Rework Facility on the West Coast. During a dog and pony show at the Pentagon, some senior personnel at the Pentagon noted a similarity between the Sergeant's paint scheme and a presidential aircraft. We removed the flag from the tail to make it less presidential. I blamed the Project Officer for initiating the non-military paint job, but everyone else including the boss blamed me.

Sergeant Henderson and one pilot died in this aircraft. I think the other pilot survived. Sergeant Henderson had just changed the main transmission and was on a test hop when his aircraft was lost. I don't know why the aircraft crashed. I don't know what errors were made. I suspect that one dedicated Marine died trying to do too much. Can one person maintain and fly a CH-53 with limited support? It all depends on the mission and the flight schedule. Sergeant Henderson did it for over a year. Lots of flight hours with limited parts and maintenance is always dangerous. From an operational standpoint, the project needed flight time to accomplish the mission.

Sergeant Henderson did not die in Vietnam and he is not listed on the Wall. Aviation Marines like Sergeant Henderson have been maintaining and flying helicopters in war and peace since the Corps first flew helicopters. Taking the machines apart and putting them back together again and then flying their handiwork is what they do. Sergeant Henderson also participated in pioneering a technology that makes our military the best in the world. We need to keep a special place in our memory for all of our heroes like Sergeant Henderson who helped make Marine Corps Aviation what it is today.

What happened to the Helicopter Maintenance Department? They went back to being a pool of maintenance technicians. The Helicopter Maintenance Department became less efficient and flying test aircraft in those conditions became more dangerous. The paper work alone may have killed Sergeant Henderson. Most aviation maintenance departments have a few special people that are very intelligent, well educated with lots of experience. They are the Sherlock Holmes of aviation maintenance. These technicians can see the mistakes and correct the problems before they kill people. If the maintenance department has one or more of these individuals, they should be assigned to the Quality Assurance Department. In some cases, these bright individuals are not identified by occupational specialty or rank and they may be overlooked. In small detachments, they may not exist. I pick my pilots, aircraft and maintenance department before I go flying.

Someone in most maintenance departments make life or death decisions every day. They determine if an aircraft is safe for flight or not. Most component failures in helicopters fall into the shades of gray category. Their decision is easy if its a major safety of flight issue. The aircraft is down. It is more difficult if its a minor discrepancy like metal chips in a transmission, a leaking actuator or fuselage cracks. All military and commercial aircraft fly with minor discrepancies. The individual that makes safety of flight decisions can't make mistakes. An H-53 main transmission shaft bearing ring has about 50 steel bearings. The bearings are about twice the size of the marbles we used as kids. If some of the bearings are damaged with pieces missing, should the transmission be changed? The factory thought it was flyable, but we changed the transmission anyway.

The Department's reorganization really worked. We didn't lose any aircraft to maintenance errors when we used the shop system. We did have one UH-1N accident while the aircraft was practicing an auto-rotation. The shop system identified that maintenance personnel should be assigned specific responsibilities inside an organization. That the quality of their work can be identified and managed in this manner. We idenified that the maintenance pool system lacks the necessary controls for error free maintenance. A person with a strong personality could determine maintenance policy inside a pool.

Most humans avoid working on something new if they have a choice. The availability of our resident SH-2 was very good because we had several Navy personnel that had years of experience maintaining that type of aircraft. They really wanted that aircraft to be flyable all of the time. Maintenance on the UH-34 and CH-46 was slow because we didn't have personnel with same depth of experience and motivation. The H-1 aircraft were new models and that always helps availability. Our CH-53 aircraft had the same maintenance problems and availability as the mine sweeping 53s. Fly it once and then fix it was our standard routine. The aircraft that was down the most was the CH-53. The AH-1, UH-1, and SH-2 were up the most and the SH-3, UH-34 and CH-46 were in the middle.

American military pilots are the best in the world. Pilots that graduate from the Naval Test Pilot School are the best of the best. The school provides it's students with the knowledge and techniques necessary to test the limits of aircraft performance. Our project pilots were also the eyes and ears of aircraft maintenance. Experienced aviators and pilots with an engineering backgrounds are good troubleshooters. Pilots and maintenance need to work as a team for fast, safe and efficient aircraft maintenance.

We had one Lieutenant Commander that flew everything. He was a project pilot with lots of experience. His preflight inspection was normally a walk around that lasted 5 minutes. He would kick the tires, light the fire and go. A casual observer might think he wasn't doing a proper preflight inspection. They would be wrong. If a prior flight didn't have maintenance discrepancies and if the aircraft didn't have maintenance performed since the last flight, a walk around preflight is sufficient. He researched his aircraft's preflight status and did an excellent post flight inspection. He was my pilot of choice when I went flying. We were coming back from a liaison meeting in an AH-1 Cobra when he did a mock attack on a passing Army CH-47. I think the Commander was a closet fighter pilot.

You normally can't see bad parts or components that cause accidents in helicopters. Bad bearings in transmissions, cracks in dynamic components and other conditions that cause catastrophic failure are not normally visible to the naked eye. We avoid these problems with a system of checks and balances that are connected by paper work and inspections. Getting new aircraft through their initial break in period is the most hazardous period of time. New aircraft have all kinds of unknown failure points. That's why Marine One is an old Navy H-3 helicopter.