INTRODUCTION

Boeing Vertol rolls out the H-16 helicopter, the largest copter, center, at Philadelphia International Airport. A Navy HUP-1 is in the foreground. In the background, taking off, is an H-21.

By Charles Kessler

I had just returned from Japan and been discharged from the Air Force after five years of service, the last with an emergency rescue squadron, when I joined Piasecki Helicopter Corp. as a flight test engineer in October 1947.

Frank Piasecki had formed the company in Morton, Pa., and had built the factory. The PV-2 had completed flying, the HRP Dogship had been built and test flown, when I became employee #319.

Little did I realize at that time that I would witness and be a part of helicopter development for the next 37 years.

From left, Ken Meenan, Elliot Daland, Frank Piasecki, 
D. Myers, F. Mamrol, W. Schwartz.

I have a lot of memories of unusual things that happened, some good, some not so good. At my age (88*) these memories are a little hard to remember, so I’m going to record some of these events. I have photos of some, which I will include.

I’m not going to attempt  to record the history of the company, since this was nicely accomplished in the book “The Golden Years” which was published in the year 2000.

I will only deal with incidents where I was personally involved.  In the beginning I will include some  photos of things that occurred before  my time, since I saved them all these years.

Charles Kessler

This material was written in 2007, at the age of 83.

Charles Kessler is a retired flight test engineer for Boeing’s Vertol helicopter division (formerly Piasecki Helicopter Co.). He joined Piesecki in 1947, in the company’s fourth year, and retired from Boeing in 1983. During his 37-year career he took part in the testing of prototypes and alterations of such models as the CH-47 Chinook and Sea Knight, the H-16, HRP-2, and the V-107. He taught the stability augmentation system to the German Luftwaffe. He has written about his experience in a blog called “Early Helicopter Years,” which can be found at http://helicopterstory.blogspot.com/.

 

1. HARD-TO-BELIEVE INCIDENT

An early test flight on an HUP aircraft, or could have been an XHJP, since they were basically the same, an incident occurred that I still find hard to believe. The flight was from the Morton flight ramp in front of the Quonset hut, and utilized a trailing bomb.

The device is a streamlined weighted pitot tube attached to a cable to measure airspeed in undisturbed air when extended approximately 50 feet below the helicopter.  This requires the helicopter to take off vertically and climb until the device is clear of the ground and then proceed into forward flight. It also requires a person on the ground to play out the cable as the helicopter climbs. In this case it was Jack Gordon and me.

The flight crew was pilot Jim Ryan and Test Engineer Christ Christadola.

Christ was a large Greek with very large hands (this becomes important later in this story).

Every thing was normal up to the point of lift off, when the helicopter started climbing vertically much faster than normal and transitioned to forward flight before the trailing bomb was clear of the ground. We had a mad scramble to get clear of the cable before we got caught up in it. A leg tangled in the cable would be a wild ride.

The helicopter went into a tight 360 degree right turn about the time the trailing bomb was clear of the ground and was coming back over the ramp with the trailing bomb about three feet off the ground. Jack and I went flat on the ground  to get out of the way. The bomb was swinging laterally and nearly went in the Quonset hut open door.

Our thoughts were that Jim Ryan had forgotten  about the trailing bomb and was just having some fun with us. The right turns continued and the helicopter climbed to higher altitude.

Suddenly the helicopter leveled off, stopped climbing, and was returning in a normal manner to the ramp. A normal high hover was established and we received the trailing bomb as the helicopter descended.

What Happened and Why?

It’s normal procedure for a mechanic or engineer to install a rig pin in the flight controls to lock the controls in neutral during calibration of the instrumentation on board.  The rig pins are about 3/8 inch in diameter and about 5 inches long, they pass thru all the quadrants in the control system. One is for lateral/directional control and the other for longitudinal/collective control. They have a large ring attached to the top of the pin so they would not be forgotten, and would be easy to remove. You guessed it!!

This day the rig pin for the lateral/directional control couldn’t be located so a 3/8 diameter bolt was substituted. This left only a hex head to grip and remove the pin. These pins cannot be removed unless the controls are in absolute neutral, no load, and usually require a little wiggle of the controls to pull them out.

The lateral/directional pin/bolt was not removed prior to take off. This left the pilot with no control in those axis. The right turns were not of his doing and he was climbing trying to clear the trailing bomb. It’s hard to imagine being airborne with the lateral control stick and the rudder pedals locked, and a trailing bomb hanging 50 feet below.

The location of this rig pin/bolt is between the pilot’s feet.  “Christ” who is seated in the co-pilots seat, on the other side of the console, was able to reach over between the pilot’s feet and remove the bolt pulling on the hex head. It would have been nearly impossible for Jim Ryan not to have a load on the controls while the bolt was being removed. 

Christ managed to remove the bolt and prevented what could have been a very serious accident.  It happened no one was hurt and no damage done, but we had a very angry pilot.

Bolts were no longer substituted for rig pins.  

Charles Kessler is a retired flight test engineer for Boeing’s Vertol helicopter division (formerly Piasecki Helicopter Co.). He joined Piesecki in 1947, in the company’s fourth year, and retired from Boeing in 1983. During his 37-year career he took part in the testing of prototypes and alterations of such models as the CH-47 Chinook and Sea Knight, the H-16, HRP-2, and the V-107. He taught the stability augmentation system to the German Luftwaffe. He has written about his experience in a blog called “Early Helicopter Years,” which can be found at http://helicopterstory.blogspot.com/.

 

    

2. HELICOPTER TORPEDO LAUNCHER

Torpedo test

The United States Navy requested we test the effect of attaching two 500 pound  torpedoes to the sides of a HUP helicopter. The weight was not a problem, however, after launching one torpedo the lateral center of gravity would be displaced by the one remaining torpedo.

It seemed like a simple test to be performed so the aircraft was configured for the test. The pilot taxied  to the end of the ramp area and attempted to lift off  to a hover. The aircraft immediately rolled on its side, with rotor blades pieces flying in all directions.

What Happened?

The test engineer, Chuck Vandusen elected to mount a ballast box on the landing gear structure with proper weights installed to simulate the 500 pound torpedo. The landing gear incorporates an oleo strut as most heavy aircraft do. With this installation the weight was on the landing gear and not the airframe.

The pilot could not detect the displaced center of gravity as he slowly added power, but when the wheel came off the ground he suddenly encountered a roll that he was not prepared for and could not control.  As a result the helicopter crashed. No injuries, we repaired the helicopter, mounted the ballast box on the airframe and successfully completed the test program.

From thereafter Chuck was known as “Lateral Vandusen.”

Charles Kessler is a retired flight test engineer for Boeing’s Vertol helicopter division (formerly Piasecki Helicopter Co.). He joined Piesecki in 1947, in the company’s fourth year, and retired from Boeing in 1983. During his 37-year career he took part in the testing of prototypes and alterations of such models as the CH-47 Chinook and Sea Knight, the H-16, HRP-2, and the V-107. He taught the stability augmentation system to the German Luftwaffe. He has written about his experience in a blog called “Early Helicopter Years,” which can be found at http://helicopterstory.blogspot.com/.

  

3. POWER BRAKES

Power Brake test

The United States Army H-21 had been in service for some time when they reported that under some conditions the brakes were not adequate to stop the helicopter in a down hill situation when the rotors were not turning. The corrective action was to change the brake system from manual brakes to power brakes. This was accomplished and a test installation was installed.

The test program was proceeding very well, however, one of the test points was to taxi the aircraft down the runway at 60 knots and apply the brakes. The test pilot on this program was my good  friend Bob Gangwish. He performed the test as programed. The brakes worked very well, the landing gear stopped and the helicopter kept going and of course, with no landing gear it rolled over.

There was an article about the accident in the local newspaper and Bob’s age was printed  2 years older then he really was. He was not pleased about that and wondered who gave the reporter the wrong age. It was some time before I told him it was me. An honest mistake.

Charles Kessler is a retired flight test engineer for Boeing’s Vertol helicopter division (formerly Piasecki Helicopter Co.). He joined Piesecki in 1947, in the company’s fourth year, and retired from Boeing in 1983. During his 37-year career he took part in the testing of prototypes and alterations of such models as the CH-47 Chinook and Sea Knight, the H-16, HRP-2, and the V-107. He taught the stability augmentation system to the German Luftwaffe. He has written about his experience in a blog called “Early Helicopter Years,” which can be found at http://helicopterstory.blogspot.com/.

  

4. US AIR FORCE DRONE RECOVERY PROGRAM SOR-190

The Air Force had a requirement to procure some helicopters to recover the Q2C Drone from the water.  They had narrowed the selection to a Sikorsky H-3 or the Vertol V-107, establishing a competition between the two, to be held at Wright Paterson Air Force base. 

We were delivering aircraft to New York Airways at that time so we were to delay delivery of one of them to use it in the competition. My good friend Tom Green and I were to be the flight test engineers for the program.   Tom was to monitor the program flown by the Air Force  pilots and I was to supervise the crew and the maintenance.  We also were charged with the preparation of the aircraft before we went to Wright Paterson.

One of the features we advertised to the Air Force was individually interchangeable  rotor blades, as opposed  to matched sets. The rotor blades on this aircraft were not interchangeable and had to be replaced  prior to departing.  A set of interchangeable blades were supplied and we installed them on the Air Force Demo aircraft.  The first flight with these was unacceptable  because of vibration.  We tried all of our magic but could not get the vibration level down to acceptable levels. For the demonstration the vibration levels needed  to be better than just acceptable.

Tom and I had the responsibility to solve the problem. We were running out of time with only a few days before departure.  After hours we were still laboring over the problem, we decided we had to reinstall the original blades, interchangeable  or not.

The problem became compounded when we found out that those blades were used to ferry another aircraft  to Canada for a rotor blade deicing test. Different blades were to be used for the test so our blades were sitting in Canada.  Now its really decision time!  We finally decided we had to have those blades which meant chartering a cargo type aircraft that could handle the blades. We said “do it”, knowing if this failed to correct the vibration  problem we would probably be looking for new jobs.

We had the blades the next evening, installed them and flew the aircraft the next morning.  We had a smooth bird, and we departed for Wright Paterson the next day.

The Air Force had painted a yellow line down the center of a hangar, we had one side, Sikorski the other.  These  two helicopters each had 2 T-58 GE Gas

Turbine engines. Both were instrumented and when weighed in, there was only 40 pounds difference. Well matched.

We got along fine with the Sikorski guys, we ignored each other. We ran across them in a restaurant and ordered a drink for them.  They did the same for us later.  The Air Force pilots were checked out in both aircraft and the program got under way.

They usually did not advise us of what test they were going to do unless it involved something special. Both a/c were prepared and ready to go every morning for three weeks.  One of the tests we did, it involved hover out of ground effect with a heavy load on the cargo hook. The Air Force gave us a cable to use but we didn’t like it, so we thanked them and told them we would use our own. Sikorski used the provided cable and it failed.  Lucky  for them it failed at the upper end and snapped down.  If it failed at the lower end it could have snapped up into the rotor.

We knew we would be required to demonstrate a drone,  recovery so Vertol fabricated a scale-size mock up of the drone. The actual drone had a ring on the top to attach a cargo hook.  The water demonstration portion was performed in a rather large lake on the Air Force property.

We deposited our mockup drone in the lake for the Air Force to fly to the lake and make a recovery. This maneuver was to be accomplished with a crewman standing on the passenger steps with a long pole and a hook attached.  He directed the pilot using the inter-phone. The crewman was to hook onto the drone, but as they hovered over the drone it flipped upside down.

The crewman continued trying to reach under the drone to attach to the hook.  While doing this he was directing the pilot to move back  but he wasn’t looking  back. The banks of the lake were about 30-40 feet above the lake level and angle up at about 45 degrees.

On the top of the bank some Air Force dependents had gathered to watch the operation. If the pilot continued to back up, the blades would have hit the bank, traveled up and could have hit the dependents.  All the Vertol and some Sikorski people were running around trying to get the pilot's attention. 

As luck would have it, there was a small boat tied up on the bank (the only one on the lake) and the helicopter fuselage hit the boat. The pilot felt it, moved forward, and saw our signals.  Some damage was done to the baggage bin on our helicopter, but it could have been much worse.

One of the Sikorski engineers photographed  this near disaster, and our project engineer took his camera away from  him. The Air Force got his camera back for him less the film.

Sikorski did their demonstration with a 50-gallon drum, a welded loop and some lead weights to keep it right side up. I guess we tried too hard.

Since this aircraft was not military, it had never been seen by Air Force personnel, our project engineer decided that when the AF guys were finished for the day, we should hover the A/C along the highway on AF property so everyone could see it.  It seems we caused some accidents by people watching the helicopter and not their driving, so the AF said stop.

When the program was over we were confident we had won. We had a distinct performance advantage since we did not waste horsepower on a tail rotor but we had to wait and see.

At the end, we discovered Sikorski had removed their instrumentation, installed their troop seats and were giving rides to the high ranking officers.  We couldn’t sit still for that. Since our helicopter was an airliner, we had removed the interior to do this program so we called back to the plant and had them truck out the complete interior, seats for 25 included. We worked all night installing it. Next day we lined them up for rides. We made a water landing on each trip. We not only had the high ranking officers, we had all the secretaries; we even saw the motel manager lined up. We took them all.

We won the competition but did not get the contract.  Our production line was committed  for some time in the future, we were building V-107 aircraft for Canada at that time. Not a big loss. I think they only built a few for the Air Force.

Sharing a Shoe Shine Kit

In 2003, Tom Green sent me this letter along with a shoeshine kit we had shared during our stay at Wright Field -- 42 years earlier! I brought back great memories! 

 

Charles Kessler is a retired flight test engineer for Boeing’s Vertol helicopter division (formerly Piasecki Helicopter Co.). He joined Piesecki in 1947, in the company’s fourth year, and retired from Boeing in 1983. During his 37-year career he took part in the testing of prototypes and alterations of such models as the CH-47 Chinook and Sea Knight, the H-16, HRP-2, and the V-107. He taught the stability augmentation system to the German Luftwaffe. He has written about his experience in a blog called “Early Helicopter Years,” which can be found at http://helicopterstory.blogspot.com/.

  

5. GROUND RESONANCE - MECHANICAL INSTABILITY

H-21 Ground Resonance Accident

One of the first considerations for flight testing a new or modified helicopter is to determine it’s susceptibility to get into a ground resonance situation. This applies primarily to helicopters with a fully articulated rotor system. This was true of all our helicopters.

Without a lot of technical explanation, the condition can only occur when the helicopter is on the ground.  It involves the landing gear oleo, or shock absorbing cylinder, the rotor blade lag dampers, tire pressures and rotor blade weight. The condition may occur at various rotor RPM, collective pitch, and control motion.

When the helicopter gets into this condition, it can be stopped immediately by lifting the helicopter into the air.  The motion in this condition is a divergent lateral oscillation that can destroy the helicopter if permitted to continue. 

If the aircraft is flyable the testing can be performed and lifting off is the way to stop it. If the aircraft is new and has never flown, lifting off is not logical since you may encounter other problems and may not be able to put the aircraft back on the ground.  An alternative for testing a new or modified aircraft that has not flown is to change the frequency of it’s contact with the ground. We have done this a number of times, I will try to explain how we did that.

To change the helicopters relation with the ground, we attached heavy cables from each side of the forward and aft rotor, and from each main landing gear wheel. The cables were all joined  together and attached  to two heavy pipes about 12 foot long. With this arrangement pulling on the pipes would  pull the cables and change the frequency of the helicopters relation with the ground and stop the resonance. 

Two Problems:

1. Who’s going to pull on the pipes, if needed.  Solution: Get twelve laborers from the Employment agency to hold the pipes and pull when the pilot yells “PULL” on the PA system.
2.  If there is an accident these people could get hurt from flying debris. Solution. Build a double 12 foot cyclone fence between them and the helicopter.

This procedure worked well in the past, but not this time. We were testing  new all metal rotor (prior blades were wood). The aircraft went into resonance, the PULL command was given, the men pulled but the cable to the aft rotor failed.  The helicopter was severely damaged as shone in the following pictures.  Testing of the new metal rotor blades was discontinued.

Charles Kessler is a retired flight test engineer for Boeing’s Vertol helicopter division (formerly Piasecki Helicopter Co.). He joined Piesecki in 1947, in the company’s fourth year, and retired from Boeing in 1983. During his 37-year career he took part in the testing of prototypes and alterations of such models as the CH-47 Chinook and Sea Knight, the H-16, HRP-2, and the V-107. He taught the stability augmentation system to the German Luftwaffe. He has written about his experience in a blog called “Early Helicopter Years,” which can be found at http://helicopterstory.blogspot.com/.

   

6. TRIP ON A HELICOPTER CARRIER

Sweden  purchased some V-107 aircraft from us with extended range fuel tanks. They carried so much fuel that in the event of an engine failure with full fuel tanks and some cargo they would not be able to sustain flight.  We included a fuel jettison system so that they could reduce the weight.

We tested fuel jettison in flight over New Jersey and had no impingement on the aircraft, however, we spotted up several automobiles in a Dupont parking lot.  Our insurance company passed out money for a car wash, at the gate, at quitting time. The fuel had been died  red.

We still had a requirement to test for fuel impingement when taxiing on the water.

We were going to go down to the lower end of the Delaware Bay and do the test. We made the mistake of notifying the U S Coastguard of our plan. They said no way, 50 miles at sea or no discharging fuel. The company would not permit us to go offshore that far and land on the water, so we had a problem.

The Philadelphia Navy Yard was building Helicopter Assault Carriers, had just completed the sea trails on one, and would be delivering it to Norfolk.  Thru the Chief of Naval Operations we got permission the catch a ride with them.  Our company was still a little leery, so they made us fill the helicopter with enough Styrofoam to keep it afloat in the event of a problem.

We joined them at the Philadelphia Navy Base and proceeded off the continental shelf to dispose of some WW11 decoding disks. Our test was successful and we left them about 50 miles off Virginia Beach and flew home. The crew treated us very well and we all learned some Navy tradition.

We had our meals in the officers dinning room and learned that your cloth napkin is used for a week. You replace it in your napkin ring using a special folding technique, and place it in a rack with your number on it, ready for the next meal. This was started years ago to reduce the laundry load.

Charles Kessler is a retired flight test engineer for Boeing’s Vertol helicopter division (formerly Piasecki Helicopter Co.). He joined Piesecki in 1947, in the company’s fourth year, and retired from Boeing in 1983. During his 37-year career he took part in the testing of prototypes and alterations of such models as the CH-47 Chinook and Sea Knight, the H-16, HRP-2, and the V-107. He taught the stability augmentation system to the German Luftwaffe. He has written about his experience in a blog called “Early Helicopter Years,” which can be found at http://helicopterstory.blogspot.com/.

   

7. ROTOR TEST STAND FOR THE XHRP

The rotor test stand was used to test the dynamic system used in the XHRP helicopter. All the components were the same as the helicopter except it only utilized one rotor, but since the rotors were the same, it didn’t matter.

A flywheel was installed to simulate the load of the second rotor.  The engine was a Pratt & Whitney R1340 AN-1. The test stand was built on the chassis of an old White truck, which would still run but would only make about 30 MPH.

We had to put many hours on the components so we, at times, would run it 24 hours a day. We had many noise complaints and it was not unusual to see the police car come driving up. We would shut it down and listen to the complaint. Sometimes the policeman would go to the location and listen. We would run in flat pitch and he would come back and say it wasn’t bad, go ahead and run.

The winter was pretty bad and very cold especially at night. We would cover our legs and put a heat lamp under the cover. (Visible in the attached photo)

We finally had to move it to the lot behind the Philadelphia airport.

Following the Bud Felt accident the test stand was used for part of the investigation. There was need to simulate a flare so we towed the test stand down the runway with our old fire truck at 60 knots with the rotor running.

It was a sight to behold and prompted a comment on the radio from one of the airline pilots “Tell those guys they are never going to get that three dollar bill off the ground”.

It served its purpose and I lost track of it, no idea what happened to it.

Charles Kessler is a retired flight test engineer for Boeing’s Vertol helicopter division (formerly Piasecki Helicopter Co.). He joined Piesecki in 1947, in the company’s fourth year, and retired from Boeing in 1983. During his 37-year career he took part in the testing of prototypes and alterations of such models as the CH-47 Chinook and Sea Knight, the H-16, HRP-2, and the V-107. He taught the stability augmentation system to the German Luftwaffe. He has written about his experience in a blog called “Early Helicopter Years,” which can be found at http://helicopterstory.blogspot.com/.

   

8. SOMETIMES IT JUST TAKES LUCK

As part of the certification program  to operate the New York Airways V-107 from the roof of the Pan AM building, it was necessary to test at various elevations and temperatures. Denver was one of these test sites. The aircraft had been there for a couple of weeks and had completed that portion of the tests.

The next need for this aircraft was a competition at Forbes Air Base in Topeka, Kansas.  I was not part of the Denver Tests but I would be going to Topeka, with a new crew. Some maintenance was required prior to departing for Topeka and I brought the crew to do it. The original crew departed and left us to clean up their mess. We took over the rental cars they had and the first problem was to find them.

To accomplish the required maintenance it was necessary to remove the aft rotor.  All went well up to the reinstallation of the aft rotor hub.  The large nut that secures the rotor hub to the shaft requires a very high torque.  Special tools had been built, which involved a wrench with gear reduction and a large plate that prevented the rotor from turning.  We brought this tool with us, but during the operation the backup plate portion of the tool broke.

We only brought one tool so we were in big trouble.  It was Saturday and we had to leave for Topeka on Monday. I wasn’t sure if there was another tool available back home or if we could get it to us in time.

Now we needed luck, lots of it.  A close examination of the tool revealed a manufacturer’s name plate. Hard to believe, but the company was in Denver.  We found the location and it was close to the airport. We went to the plant, which was closed on Saturday, but had a guard at the gate. I identified us and told him we needed to talk to the president NOW!  He got the president on the phone and I explained our problem. He wasn’t sure he could help, but he would send someone to see what they could do, perhaps repair the broken plate.

We entered the plant and the gentleman with us looked up a location. We went there and there was a brand new backup plate – they had made an extra one.  We took the plate, I promised to get them paid for it and completed the job. 

The work was completed, test flight flown, and we departed for Topeka on Monday. Tom Green had gone ahead to Forbes Air Force Base, and arranged security for us. Forbes was a Strategic Air Command Base so security was extremely tight. When one of our competitors flew in without security clearance, the military police hauled them away to the lockup, and kept them there until they were cleared. 

This base has several Atlas missile sites in this area, and the crew changes are accomplished by busses. Some were several miles away. They were considering using helicopters, so they had us, Kaman, and Bell performing the crew changes for a week or so.  We also visited a missile site. There were two Air Force majors at the site with side arms. We were informed that if one of them attempted to launch the missile without authority the other one would shoot him. That never happened.

The demonstration seemed to be very successful but the Air Force  never adopted the program.

We returned home to prepare for another demonstration for the US Army at Fort Rucker, Alabama. That’s another story. 

Charles Kessler is a retired flight test engineer for Boeing’s Vertol helicopter division (formerly Piasecki Helicopter Co.). He joined Piesecki in 1947, in the company’s fourth year, and retired from Boeing in 1983. During his 37-year career he took part in the testing of prototypes and alterations of such models as the CH-47 Chinook and Sea Knight, the H-16, HRP-2, and the V-107. He taught the stability augmentation system to the German Luftwaffe. He has written about his experience in a blog called “Early Helicopter Years,” which can be found at http://helicopterstory.blogspot.com/.

   

9. FLIGHT ACCEPTANCE ENGINEERING

This Group was part of the Engineering Liaison Organization. We were based in the Production Flight Test area. Our job was to investigate and resolve problems. Our objective was to reduce our flights to one company and one customer.



Flight Acceptance Engineering



We never really achieved that, but we came close. We investigated discrepancies back to the vendor if necessary. One member of our group participated in most test flights and performed in-flight tasks such as engine topping adjustments, rotor blade tracking and balancing.

 Following acceptance by company pilots we worked with customer pilots and Quality Control through final acceptance.

Most of our activity was with the US Army and Navy, however, we also worked with British, Australian, Italian, Canadian and Spanish customers.

One member of our group was lost in a Chinook accident, another parachuted safely.

Charles Kessler is a retired flight test engineer for Boeing’s Vertol helicopter division (formerly Piasecki Helicopter Co.). He joined Piesecki in 1947, in the company’s fourth year, and retired from Boeing in 1983. During his 37-year career he took part in the testing of prototypes and alterations of such models as the CH-47 Chinook and Sea Knight, the H-16, HRP-2, and the V-107. He taught the stability augmentation system to the German Luftwaffe. He has written about his experience in a blog called “Early Helicopter Years,” which can be found at http://helicopterstory.blogspot.com/.

   

10. BIG TROUBLE AT NEW YORK AIRWAYS

New York Airways had been operating their V-107service between Kennedy, La Guardia, Newark, and Wall Street for some time when they experienced a fatal accident, The crew of three and, I think, three passengers perished. The investigation revealed that an aft transmission lubrication jet had become clogged and the lack of lubrication caused the failure.

The airline was grounded for a short period and when they resumed operation, passengers were few and far between. Since they are a scheduled commercial airline they cannot cancel a scheduled flight except for a mechanical problem or weather. Not for a lack of passengers.

They would claim mechanical for any minor item, which made things worse. Example: If someone was taking an overseas flight out of Kennedy, and planned to get there via New York Airways, they arrived at Newark only to find the flight canceled, and no other way to get to Kennedy in time to make the flight. Some of the ticket agents told me they hid behind the counter.

On thing led to another and a major dispute developed between New York Airways management and our Customer Service Department.  As a result our service representative was sent home and NYA would only talk to Engineering.  It was suggested that, since I taught  them the 107 aircraft that I would take a couple  of my guys, from flight test engineering, go up there and try to get things going.  I took Walt Davis and Archie Stalcup, two outstanding 107 flight test engineers.  This was acceptable to NYA.

We stayed with them 24/7, reviewed every discrepancy written by the pilots, and followed up on each and every item. We were there for several weeks, including  Christmas. We had our two small children at that time; my poor wife had to do it alone.  I came home at 10 p.m. Christmas Eve and went back at 2 p.m. Christmas day.

Gradually things came around and we were able to come back  home.

Charles Kessler is a retired flight test engineer for Boeing’s Vertol helicopter division (formerly Piasecki Helicopter Co.). He joined Piesecki in 1947, in the company’s fourth year, and retired from Boeing in 1983. During his 37-year career he took part in the testing of prototypes and alterations of such models as the CH-47 Chinook and Sea Knight, the H-16, HRP-2, and the V-107. He taught the stability augmentation system to the German Luftwaffe. He has written about his experience in a blog called “Early Helicopter Years,” which can be found at http://helicopterstory.blogspot.com/.

   

       

11. HRP-1 JAW CLUTCH PROBLEM

One night during the HRP testing, at the lot behind Philadelphia International Airport, we received some visitors from engineering. There had been an HRP-1 accident in the service and they wanted to do some testing. The test was to run the rotor at normal operating RPM, quickly close the throttle, which will cause the rotor to over- run the engine, then quickly open the throttle.

We did this a number of times until we had a large bang. A look outside surprised us. The ply wood from the blades was littered all over the parking lot. Very little wood was left on the blade spars.

This is exactly what happened in the service, during a landing the engine cut out then came back on and the blades came apart. The aircraft was just about to touch down so no one was hurt.  This drive system incorporates a so called jaw clutch. This device disengages the rotor from the drive system to permit the rotor to auto rotate in the event of engine failure.  The rotor will re-engage when the power is applied.  There is sometimes some free run depending on the relation of the two halves of the jaw clutch. This causes a very rapid acceleration to the rotor blades, causes the trailing edge to compress and actually explode. Sounds complicated doesn’t it.  The cause was simple, but the fix was tough!

We used one of the HRP-1 aircraft to test some fixes. We tried a shear pin in the engine shaft and destroyed 6 more blades.  We also tried a friction slip joint in the shaft and destroyed  more blades. We stopped  using real blades and made some from  2x4, not to fly. The original jaw clutch had 9 teeth, we got jaw clutches made that had 21 teeth; that cured the problem.  The new jaw clutch with smaller teeth meant that they would always be a shorter distance from engaging, so there would be less impact.

It is hard to explain but it worked.  After several runs on the ground, with normal blades, Frank Piasecki and pilot Bill Knapp lifted the aircraft into the air and while hovering turned the Magneto switch off and on again, which created hugh back fires, but that was Piasecki!

12. LOSS OF CONTROL OF A CHINOOK

While hovering one of our early Chinook aircraft at Philadelphia International Airport there appeared to be a loss of control, resulting in the loss of the right main landing gear. Initially it appeared that there was a failure in the Stability Augmentation System. The aircraft was returned to our hangar via crane and repaired.

There was a lot of discussion regarding the cause of the accident. I think there were some who felt it was pilot error and some who thought otherwise.   

The SAS system was removed and taken to the lab for examination.  I happened to be in our coffee shop when the pilot of  that aircraft was notified by the chief pilot that there was nothing wrong with the stability system. He  told the chief pilot what he could do with the job and departed.  

Charles Kessler is a retired flight test engineer for Boeing’s Vertol helicopter division (formerly Piasecki Helicopter Co.). He joined Piesecki in 1947, in the company’s fourth year, and retired from Boeing in 1983. During his 37-year career he took part in the testing of prototypes and alterations of such models as the CH-47 Chinook and Sea Knight, the H-16, HRP-2, and the V-107. He taught the stability augmentation system to the German Luftwaffe. He has written about his experience in a blog called “Early Helicopter Years,” which can be found at http://helicopterstory.blogspot.com/.

   

13. STABILITY AUGMENTATION SYSTEM (SAS)

Early helicopters all had one serious problem.  They were difficult to control, pilots had little time to look at a chart or attend to other cockpit requirements.  The flight controls required continuous but small control inputs, even to fly straight and level.  This problem persisted thru Army production of the H-21, Army & Navy production of the HUP, and other foreign customers.  It was just an accepted condition of helicopter flying.  As opposed to fixed wing aircraft, which will, for the most part, fly straight and level if controls are released.  A helicopter never wants to perform in the same manner.

Our first attempt to correct this problem was the installation of a Sperry A-12 autopilot from a fixed wing aircraft in a HUP-1 helicopter. The installation contained an electronic Joystick mounted on a bracket convenient to the pilot’s right arm.  Severe problems were encountered.  The autopilot had 100% control authority, so that a malfunction could drive a control to the stop faster than the pilot could regain control.  This is not a problem in fixed wing installations since the gain would be set much lower, resulting in slower control movements.  Also the auto pilot would only be turned on in level flight.  Helicopter installations would be needed in hover also.  So much for the A-12 autopilot.

Our next attempt was the installation of a Roll-Rate-Damper in an H-21.  The intelligence for this device was a Rate Gyro which produced a variable strength signal as a function of the helicopter roll rate.  The faster the roll, the stronger the signal.  The signal was processed and directed to a variable link in the control system.  This link would normally move with the control rod so that normal control was maintained.  The link had limited authority, about 20% of total control.  Therefore a hard over malfunction was easily controlled by the pilot since his hand was already on the control stick.  We tested up to 1 full second delay before pilot recovery was initiated.

This system performed very well, the small roll inputs were taken care of by the rate damper, while full control was maintained by the pilot.  The Roll Rate Damper worked so well, we installed the same basic system in pitch and yaw with some modifications.  We provided coordinated turn in the yaw system.  An intentional roll input produced an opposite direction signal, we reversed the signal so that it was in the same direction and provided the proper amount of directional control to coordinate the turn.  The SAS was born.

Some hardware changes were required to make the system fully operational. It had to be dual.  The H-21 flight system used hydraulic boost actuators made by a company called Waterlift.  We added one of the links to each of those actuators.  The second was an extendible link added to the control.  This provided us with Systems #1 and #2.  Both systems operated full time, each at half gain.  A single would do the same, operating at full gain.

The SAS was installed in all subsequent aircraft including the CH-46 Sea Knight and the CH-47 Chinook.  Later Fly-by-wire systems, which are computer controlled, incorporate the stability augmentation in the program.

The first production aircraft to have the SAS installed were for the German Luftwaff.  They already had 20 H-21 Helicopters, this contract would add 5 more equipped with SAS.  This being the first aircraft with SAS and being delivered so far from home caused some concern with the company.  No one in Europe had ever seen the system.  I was assigned to go to Germany at the time of delivery to perform several tasks:  I was to check out the 5 aircraft SAS systems to be sure they functioned properly, and train mechanics at Dornier Aircraft (our German licensee), the mechanics at Bookeburg Airbase (where the aircraft would be assigned), our field reps from Sweden and France, and the sales people from Bad Godesburg.  Most of the training was done thru interpreters, some had been German prisoners of war held in the United States, who had learned English.

Everything went well, except the aircraft were late being delivered.  We were there seven weeks, much longer than expected.  After three years of operation in Germany not a single SAS problem was encountered.

And added fringe benefit on this assignment wa I could take Nancy along.  We had a great time and traveled between Munich and Minden, about 600 miles, three times.  We had a rented VW.  We always made the trip over a weekend.  Good trip but a little long for both of us to be away from the children.

Charles Kessler is a retired flight test engineer for Boeing’s Vertol helicopter division (formerly Piasecki Helicopter Co.). He joined Piesecki in 1947, in the company’s fourth year, and retired from Boeing in 1983. During his 37-year career he took part in the testing of prototypes and alterations of such models as the CH-47 Chinook and Sea Knight, the H-16, HRP-2, and the V-107. He taught the stability augmentation system to the German Luftwaffe. He has written about his experience in a blog called “Early Helicopter Years,” which can be found at http://helicopterstory.blogspot.com/.

   

14. H-16 HELICOPTER

H-16 Roll Out

Two H-16 aircraft were built, the first with two Pratt & Whitney, R-2180-11, 1,800 horse  power engines. These engines were the result of building a few engines by splitting R-4360 engines. The large engines were 4 rows of cylinders commonly called the Corn Cob.  The  result was an engine with 2 rows of cylinders. The second aircraft was equipped with two Allison YT-38 gas turbine engines.

These were extremely large aircraft, the rotor is 82 ft diameter, and the aft pylon towers 25 feet in the air. I have been told that if equipped with passenger seats the H-16 could seat 100 people.  They were built for the USAF.

The rotor blades were machined metal, clam shells joined together, 41 foot long, approximately 3 Ft cord. This was a very precise  machining operation, with tolerances down to .002. The rotor  had a very low operating RPM of 147compared to the Chinook 235.

Overall both aircraft had been very successful as far as they had been tested. I never had much involvement in the H-16 program except to fill in for someone else.

On this particular day, which was a day or two after Nancy and I adopted  Brad, I was filling in for someone.  The flight was the last of what we called bonus flights because the pilots received a bonus for flights considered  more dangerous than normal.

This flight was to an altitude where the aircraft can no longer climb.  Prior to departure, with engines and rotor running the pilots called me in.  They would be using oxygen from portable bottles, and they noticed that the pilots bottle had a little more oxygen than the co pilots. We had already checked that out when the bottles were installed.  Both were far above the minimum for the flight. They were kidding me about becoming a new dad, called me Pappy.  They departed and I went home since it was late afternoon.

A couple of hours later I received a phone call  -  The helicopter crashed and both  pilots were killed.

I was told  to be in early next morning prepared to go to the crash site.  The explanation about the accident was sketchy.  They had a fixed wing chase plane with them and the climb to 32,000 feet, every thing was okay. When descending, the helicopter was in auto rotation all the way.  The fixed wing airplane cannot descend that fast so he was making S turns above them while descending. The fixed wing pilot lost sight of the helicopter, while looking for it he noticed a small fire on the ground.  A low pass confirmed it was our H-16.

Our team flew over in a HUP at first light.  The helicopter had broken in half in flight, the two section were on opposite sides of a small road.  It was on a farm near Swedesboro, I think.  The forward section  did  not  burn , but dug in deep and was inverted.   I won’t go into the recovery of the pilots.  We feel sure they were gone before hitting the ground due to the high G’s encountered during the break up.  Some of that was recorded on our instrumentation. I will just skip ahead to the investigation.

After moving all the wreckage back to our facility and having a good idea what happened we were asked to return to the crash site and, using a metal detector try to find a bearing race and we did.  In addition one of the guys went across the road to check the area we filled in from the front section. This area had been cleaned up and raked before we left.  Lying near the top of the sand they could see the imprint of a wallet, which turned out to belong to pilot George Callahan, and it still had money in it.  Strange

Cause of the accident:  In order to record stress on the rotor system it is necessary to route instrumentation wiring thru transmissions and drive shafts.  There was such an installation in this aircraft.  To run wires to the rotor blades it is necessary  to pass through the aft transmission, thru a stand pipe inside the vertical drive shaft, to the rotor hub, through a series of slip rings and on to the rotor.

The stand pipe was the cause of the accident.  It is supported top and bottom with large bearings. One of the bearings failed and caused the stand  pipe to break and lay over against the inside of the drive shaft, machining away the wall of the drive shaft until it broke just about the time they ended the auto rotation and recovered with power.  We were finished using that instrumentation, if we were using it, we would have known about the standpipe failure. 

       

Why a bearing failure?

The bearings used in this installation were installed horizontally between the standpipe and the drive shaft.

The bearing used was selected from a catalog and advertised as life time lubricated*

*When installed in the vertical position.

Charles Kessler is a retired flight test engineer for Boeing’s Vertol helicopter division (formerly Piasecki Helicopter Co.). He joined Piesecki in 1947, in the company’s fourth year, and retired from Boeing in 1983. During his 37-year career he took part in the testing of prototypes and alterations of such models as the CH-47 Chinook and Sea Knight, the H-16, HRP-2, and the V-107. He taught the stability augmentation system to the German Luftwaffe. He has written about his experience in a blog called “Early Helicopter Years,” which can be found at http://helicopterstory.blogspot.com/.

   

15. FORT RUCKER DEMONSTRATION

Following the demonstration at Forbes we  took the same aircraft to Fort Rucker, Alabama  to demonstrate  to the US ARMY.  Every thing was going well until we had a badly cracked engine combustion  housing. This was discovered following a morning flight. 

We had a spare engine with us (we had a spare parts truck along) but the built up engine we brought was configured for the wrong side.  There is no way we could know which side would fail, it can be converted, but it’s a lot of work.

Our problem was our company president, Don Berlin, was arriving at 10 PM and we were to pick him up at Dothan airport. We proceeded  to make the change  but not certain we could get it done in time. 

The Army guys were pulling our chain, they parked an old  Sikorski H-34 helicopter in front of the hangar and offered to pick up our president if we couldn’t get our 107 ready in time. That gave our guys a real incentive so it got ready and we made the pickup.

Don Berlin was there for two nights.  The 2^nd night we all gathered in one of our rooms at the new Daleville Inn and had a few drinks, maybe for some, more than a few. We had a night shift crew at the base so they were not a part of this.  Don turned out to be quite a party guy.

Our day shift crew normally went to the base about 6 AM. Tom Green and I started to go about 8 AM and noticed our day crew’s car was still there, they over slept.  We woke them and departed, only to find our night crew stayed over and the craft was ready to go. 

Our guys worked especially hard when on demonstrations, they really get with the program.  The demo went well but the Army did not buy the V-107.  We built 2 similar aircraft, the YHC-1A which led to the Chinook. 

Charles Kessler is a retired flight test engineer for Boeing’s Vertol helicopter division (formerly Piasecki Helicopter Co.). He joined Piesecki in 1947, in the company’s fourth year, and retired from Boeing in 1983. During his 37-year career he took part in the testing of prototypes and alterations of such models as the CH-47 Chinook and Sea Knight, the H-16, HRP-2, and the V-107. He taught the stability augmentation system to the German Luftwaffe. He has written about his experience in a blog called “Early Helicopter Years,” which can be found at http://helicopterstory.blogspot.com/.

   

   

16. RUSSIAN CUSTOMERS

One of the Russian  Premiers visited here in the United States and flew in one of the Presidential Helicopters, I can’t remember the details but they decided to buy 2 H-21 Helicopters from us and 2 H-34 Helicopters from Sikorski. When their aircraft was ready they sent their Engineers here to be trained.

We had them here for twelve weeks.  They brought their own interpreter but we could not understand his English. We had an employee in the service department who spoke  Russian (Serge Tapticoff) so he was with us all the way.

The picture taken on the flight ramp in front of one of their aircraft is the Russians and the instructors responsible for their training. They are as follows, left to right, Instructors: Charles Litz, Bruce Becker, Serge Tapticoff, Charles Kessler, Vertol Pilot  Bill Coffee, Russian Pilot Yuri, 3 Russian engineers. 

The next to last on the right was in charge, we referred to him as Papa Bear. I don’t remember the Russian  names.  I do remember the Russian  pilots first name Yuri, he was later killed doing a test flight on a fixed wing airplane in Russia.

Prior to their visit we were briefed  by our CIA that they would be seeking information on other projects we were working on. We were always to answer their questions, but don’t tell them the truth, lie to them.

We had to take turns entertaining them.  I took them to our home for a visit, it was very interesting for them to see our house.  They found it hard to believe that we had our own heating plant among other things.  One of my friends is on the School Board so we arranged for them to visit the new High School, and dinner at a local restaurant.

We got into some interesting discussions, they asked “who owns Vertol” we explained that the stock holders own it and that you couldn’t do that in Russia. They thought differently. When they came back after lunch they didn’t shake hands as was the custom, I think they were mad at us.

We had to get permission for them to go out of the immediate area. They liked to go to the Jersey Shore and that was approved for awhile, but it was October, they were going in the ocean and drawing a crowd.  Immigration said to stop.

The aircraft were delivered and they did  not want a Tech Rep , but a couple of years later we were able to send Serge over there for visit. He only found one of the helicopters and it was torn apart.  He couldn’t find out anything about the other H-21.

We think they were just looking for some new technology.  

Charles Kessler is a retired flight test engineer for Boeing’s Vertol helicopter division (formerly Piasecki Helicopter Co.). He joined Piesecki in 1947, in the company’s fourth year, and retired from Boeing in 1983. During his 37-year career he took part in the testing of prototypes and alterations of such models as the CH-47 Chinook and Sea Knight, the H-16, HRP-2, and the V-107. He taught the stability augmentation system to the German Luftwaffe. He has written about his experience in a blog called “Early Helicopter Years,” which can be found at http://helicopterstory.blogspot.com/.