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/.