Our Broken Secondary Data File

which also includes known Bearing Failures

-5

2000 ?

30

-

-

Bearings failed

-

-

N728PC

300

James Karmy

MSN Site 1/18/05

Stock ship in Oregon

Obtained from MSN Site 1/18/05

-4

2000 ?

30

3 Bearing

Bearing failure

Chain

OY-HJS

120

Jorgen Skov Nielsen

MSN Site 1/18/05

Stock Rotorway ship in Denmark

Obtained from MSN Site 1/18/05

1993?

3 bearing

Chain   100

N5251B

Wiley / Idaho

1998

30 Double

Chain   250

N864KP

Barry Pinnix

The rear sproket was found wedged inbetween large frame tube and oil bath in front just short of going through the seatback on the pilots side. It also totally destroyed the oil bath.

From what I gathered in the conversation this is a common scenario on ships with an oil bath.

1992   Exec 145

30mm   3 Bearing

Chain  169 Hours

N71RF

Ronald Froberg

NO NTSB

We added this later so we just gave them a negative number
to keep from having to renumber all the data

Shaft Break # -0

3/30/94   Exec 142

30   3 Bearing

Chain  41 Hours

N71RF

Ronald Froberg

NO NTSB

We added this later so we just gave them a negative number
to keep from having to renumber all the data

Pre 97

-

-

Tom smith

Via Hans

Pre 97

-

-

Tom smith

Via Hans

July, 1997

30mm 3 Bearing

Chain  70 hours

Hans Svendsen

C-FMAP

Date: January 31, 2000 12:10 PM 

Author: Hans Svendsen (svendsen@direct.ca <mailto:svendsen@direct.ca>) 

Subject: Secondary Shaft Failures 

I must agree with Ed, that watching this forum has been an eyeopener, a waste of time, yes, but still quite entertaining!! In spite of all the messages, I'm still not sure how many failures we are talking about, so I will contribute my own experience in the hope that others will provide theirs, so we can all get a handle on the magnitude of this problem.

I was particularly upset over Tom Smith's "With continued concern for the safety of our customers..." article in Issue 30 of Sport Helicopter. From personal experience, I know that Tom did not express a similar concern when I had my failure back in the summer of 1997.

After my accident, I was told by Tom that mine was the third recorded failure of the secondary.

These other failures, to the best of my knowledge, were not publicized either. From the forum on secondary failures, it appears that there have been one or more recent failures on Rotorway factory training helicopters, again without any mention in Sport Helicopter.

My secondary failure happened on a Sunday afternoon in July, 1997.

I was returning home after a one hour flight, climbing with 25" MP at an altitude of about 300' AGL. Suddenly, without any warning whatsoever, the engine overrevved right up to the red line. I dumped the collective and began a descent. Thinking I had main belt slippage, I tried to raise the collective to see if I could get some traction, but with the same result, engine revving up and a yawing to the right from the tail rotor action.

At this time, I must have been 100' in the air, and coming down fast. I set the helicopter down hard, and with a fair amount of forward speed. Fortunately, I was over a farmer's field, and I escaped with bent skids and landing gear, and the tail rotor tips were pretty mangled.

Subsequent examination revealed that the secondary shaft was completely sheared, and the break was so clean that when I rotated the top part of the shaft, I could not even feel it grinding against the bottom part. Before removing the secondary, we checked for alignment and found it OK. None of the "tell temps" (170-200 degrees) had turned color.

 I sent the secondary back to Rotorway, and after several months and phone calls, I was informed by Tom Smith that all three bearings were undamaged, and that the final verdict was "metal fatigue" - after 70 hours flying time!!

        I was never shown any lab test reports or given any other information to explain this mishap.

Rotorway did, without any arguments, provide replacement parts free of charge.

I am concerned that Tom Smith engages in unsubstantiated and unscientific warnings to Rotorway customers. We all rely on Tom for his knowledge and expertise on the technical aspects of the Rotorway helicopters. I hope that he will, in the future, leave the innuendo, hyperbole and half-truths to the Rotorway marketing department.

So, how many failures of the secondary can be documented? Some have suggested that a new factory version of the secondary shaft has problems. Any truth to that?

Hans Svendsen Kelowna, British Columbia, Canada 
Acquired from PRA page 2/5/2000 CJ
Thanx Hans Thats the best information ive gotten so far

this is what i gathered so far. Should you be able to add anything more or should any information be wrong let me know:

 Hans Svendsen, July 97 ,Shaft Failure
hours on the shaft?   70 hours
chain drive?  Yes
Heat Dot Temps:   Under 170 degrees
Shaft Alignment:  Correct
Probabal cause:  Metal Fatigue     Per Rotorway

John Debuted the system in
July 1998 At Homers Bell's Fly In with 400 hours test time according to Rotorheads Newsletter

10/98

30mm   Double

Chain

Source  unknown

EPI SITE NO RECORD

11/99

30mm spherical

Chain

Stieg

Factory Ship

NO NTSB

November'99 Chandler, AZ
30mm Spherical bearing Secondary
(From Stieg xxxxxx need to get his last name from my log book)
Instructor at Rotorway was hovering a Rotorway factory ship at the Rotorway factory when the engine oversped and Rotor RPM was lost forcing a hover auto. Subsequent dissasembly revealed that the secondary shaft was broken.  Exact location not confirmed. This incident not reported to the NTSB.

1/04/00

30 Spherical

Chain

NTSB

Factory Ship

NTSB # Identification: LAX00LA071

Rotorway Ship Ron Curry was riding in when the secondary shaft broke

 
Subj:  NTSB Preliminary Report
Date:  1/15/00 12:01:49 AM Eastern Standard Time

Accident occurred JAN-04-00 at CHANDLER, AZ
Aircraft: Rotorway EXEC 9, registration: N89678
Injuries: 2 Uninjured.

This is preliminary information, subject to change, and may contain errors.

Any errors in this report will be corrected when the final report has been completed.

On January 4, 2000, about 1400 hours mountain standard time, an amateur built experimental Rotorway Exec 90 helicopter, N89678, sustained substantial damage when the main rotor blades contacted the tail boom during an autorotation at Memorial airport near Chandler, Arizona. Rotorway International operated the helicopter under the provisions of 14 CFR Part 91. The certified flight instructor and private pilot student were not injured. The instructional flight departed Stellar Air Park near Chandler, Arizona, about 1320. Visual meteorological conditions prevailed and no flight plan was filed. The Safety Board was notified of the accident on January 12, 2000. The operator stated the flight was a familiarization for the private pilot, who was transitioning into this model of helicopter. An approach was being made to runway 03 when all engine power was lost at 100 feet. An autorotation was made to soft sand, but the main rotor blades contacted the tail boom, and the tail rotor blades contacted the ground. The operator reported that a subsequent inspection determined that the secondary driveshaft fractured.

NTSB # LAX00LA071

On January 4, 2000, about 1400 mountain standard time, an amateur built experimental Rotorway Exec 90 helicopter, N89678, sustained substantial damage when the main rotor blades contacted the tail boom during an autorotation at Memorial Airport near Chandler, Arizona. The autorotation followed a failure of a shaft in the engine to rotor drive system. Rotorway International operated the helicopter under the provisions of 14 CFR Part 91. The certified flight instructor (CFI) and private pilot student were not injured. The instructional flight departed Stellar Air Park, near Chandler, about 1320. Visual meteorological conditions prevailed and no flight plan was filed. The Safety Board was notified of the accident on January 12, 2000.

The operator stated the flight was a familiarization for the private pilot, who was transitioning into this model of helicopter. An approach was being made to runway 03 when the instructor heard a loud bang from the engine compartment behind his back at an altitude of 100 feet. He stated that it felt like all engine power was lost. When the instructor saw the rotor rpm decreasing, he took control and initiated an autorotation to a soft sandy area. During the touchdown, the main rotor blades contacted the tail boom, and the tail rotor blades contacted the ground.

The operator reported that a subsequent inspection determined that the secondary drive shaft fractured. Laboratory examination concluded that the shaft failed from fatigue, originating from galling sites introduced during the manufacturing process. The operator reported that a temperature strip on the bearing was noted to be darkened before the flight, but they were unsure if this information was determined independantly by either the CFI or the student. All other shafts in the operator's fleet were inspected and no additional suspect shafts were found.

Rotorway Ship Ron Curry was riding in when the secondary shaft broke

 
Subj:  Secondary Shaft breakage report
Date: 2/6/00 3:30:58 PM Eastern Standard Time

On Friday Tom sent me the engineering report on the secondary shaft thatbroke while I was flying it.  The conclusion of the report was essentially that the shaft broke from "metal fatigue" (well, da!).

More interesting is that it was due to improper assembly of the bearing on the shaft. The bearings are fitted to the shafts by heating the bearing (and maybe cooling the shaft) so they just slide together without a press.

Apparently, in this case, whoever assembled this one didn't get it on all the way on before the temperatures normalized and pressed it the rest of the way with a press.  This caused galling of the shaft creating stress points as well as it didn't get all the way down to the shoulder which ultimately caused the fracture.

Now the report states that this was the primary reason for the failure however, it also states that the shoulder that is machined in the new shafts may have contributed to that failure as is evident that it broke right at the shoulder.  Maybe I misunderstood the report - I'm going to reread it.

Tom says he's confident that it was due to improper assembly and they aren't going to remove the shoulder. which has me concerned.  I'm going to call him on Monday and discuss this with him because he didn't seem to think the report faulted the shoulder but I read it differently.

One thing I was very pleased with was Tom's full disclosure on this.  He was clear that it was improper assembly. I think if RW would make this their policy on everything they would be better off and build more customer trust
and less panic attacks by their customers.

Anyway, thought you all should know about this. Please don't reprint on PRA - I don't want to get tangled up in that BS over there.

Regards,
Ron

4/06/00

30mm Spherical

Chain

NTSB

Factory Ship

NTSB # Identification: LAX00LA173

Accident occurred APR-06-00 at CHANDLER, AZ
Aircraft: Rotorway EXEC 162F, registration: N21901
Injuries: 2 Uninjured.

This is preliminary information, subject to change, and may contain errors.
Any errors in this report will be corrected when the final report has been completed.

On April 6, 2000, at 0800 hours mountain standard time, a homebuilt Rotorway Exec 162F, N21901, sustained substantial damage when the main rotor blades contacted the tail boom during an autorotation near the Memorial Airport in Chandler, Arizona. The helicopter was being operated by Rotorway International under the provisions of 14 CFR Part 91. The certified flight instructor and student pilot were not injured. The local area instructional flight originated at the Stellar Air Park near Chandler at an unknown time.  Visual meteorological conditions prevailed and no flight plan was filed. The pilot reported that while at 300 feet agl on a downwind traffic pattern leg, they heard a loud noise from the rear of the helicopter. He immediately entered an autorotative descent. During the descent, he checked the cockpit gauges and found no discrepancies. He decided to roll the throttle back on. The pilot stated that the engine rpm increased, but not the rotor rpm; the needles were not coupled. There was a barbed-wire fence in their flight path, so the pilot extended the glide, flared, and landed hard. The left landing gear skid collapsed and the main rotor blades struck the tail boom.
The Safety Board was notified of the accident on April 27, 2000.
Broken Secondary

On April 6, 2000, at 0800 hours mountain standard time, a homebuilt Rotorway Exec 162F, N21901, sustained substantial damage when the main rotor blades contacted the tail boom during an autorotation near the Memorial Airport, Chandler, Arizona. The helicopter was being operated by Rotorway International under the provisions of 14 CFR Part 91. The certified flight instructor and student pilot were not injured. The local area instructional flight originated at the Stellar Air Park near Chandler at an unknown time. Visual meteorological conditions prevailed and no flight plan was filed.

The pilot reported that while at 300 feet agl on a downwind traffic pattern leg, they heard a loud noise from the rear of the helicopter. He immediately entered an autorotative descent. During the descent, he checked the cockpit gauges and found no discrepancies. He decided to roll the throttle back on. The pilot stated that the engine rpm increased, but not the rotor rpm; the needles were not coupled. There was a barbed wire fence in their flight path, so the pilot extended the glide, flared, and landed hard. The left landing gear skid collapsed and the main rotor blades struck the tail boom.

The helicopter secondary shaft that transmits power from the engine to the main rotor, the water pump, the fan, the tail rotor, and the lower fan was examined in the Safety Board's Materials Laboratory in Washington, DC.

There were many light scratches longitudinal to the shaft axis and numerous short circumferential score marks and light scratches observed on the surface of the secondary shaft. The shaft was in two sections and exhibited a fracture surface that was on a flat transverse plane that contained multiple crack arrest positions, typical of fatigue cracking. About 20 percent of the fracture surface adjacent to the origin area contained a rust-colored discoloration. The edge of the fracture face had been mechanically damaged which had obliterated the fracture surface details directly adjacent to the origin area. The band of circumferential marks on the shaft surface was measured, adjacent to the initiation site, and was found to be 0.16 inches wide. Measurement adjacent to the initiation site showed that the first circumferential score mark was 0.09 inches from the fracture face.

8/2000

30mm  Double

Belt

Verbal

EPI SITE NO RECORD

9/00

30 Spherical

Chain

Mark Wolf

Factory Ship

NO NTSB FILE

Date:9/18/00 4:26:06 PM Eastern Daylight Time
From:jmwolf@ismi.net

I was in the Phoenix area on business last week so I stopped in to Rotorway  for my Phase One re-endorsement since my current endorsement had expired  the first of September. It was hot, very hot! 110 degrees hot! Did I mention it was hot??!!

Got 1.4 hours dual flight time and re-endorsement, courtesy of John O'Neil. 
Good instructor, John.
One interesting thing happened. I flew the new maroon and gold ship with the  ACIS. At one point during some lateral hovering maneuvers, I tried to correct  some rotor RPM droop by adding throttle but It didn't respond and eventually I hit the throttle stop without any corresponding increase in rotor RPM. The  rotor RPM was holding in the low green but it wouldn't let me increase it. I was  at a low hover so lowering the collective to bring it back was not an optimal solution. I mentioned it to John and he suggested that we just stop and hover  motionless and it would come back. I did, and it did. John said it's a  characteristic of the ACIS under heavy loads at high ambient temps. They call it "mushing out".

I also learned that the static port experiment in the tail boom didn't work out. John said that a breeze from the rear of the ship while it was sitting on the ground would indicate airspeed. So they're back to just an open static port on the back of the IAS gauge.

I saw the new test fixture/jig for testing the secondary drives. They've adapted an old engine dyno with a standard airframe and drive train. It's not yet complete so I didn't see it in action. Tom Smith said that the instrument package and brake they're using is limited as to torque limit and RPM so there's some implementation issues they dealing with.

NO NTSB FILE

And now for the bad news. 

I really hate to be the one to bring this to you, but with all deference to Rotorway, there was another secondary shaft break while I was there. While I was sitting on the taxiway, in an idling ship, waiting for fluid temps to rise,  another ship with student and instructor aboard hovered by and turned right in  front of me to align with the taxiway. I turned my eyes to my water temp guage  for a second, heard a rapid engine rev, looked up just in time to see the ship set down at 90 degrees to the original heading.

Once the rotors had spun down, a quick check by John revealed that the main rotor and tail rotor were not connected although the TR belts seemed fine. They wheeled it back into the hangar, pulled the skins to look in the oil tub window, and John immediately said it was the secondary. I looked but with all the oil smearing the inside of the window I couldn't get a clear look, although it did look as though the secondary drive sprocket was askew.

Now before you all go charging off waving red flags it's important to note: 
This secondary was of
the new spherical type bearings with the older smaller shaft.
We already know this particular configuration is failing so, however disturbing this fresh occurances is, this is nothing new. Rotorway is actively pursuing the solution.

There was also a failure of the main drive pulley at the top of the engine last week. Apparently this ship had suffered an upper engine clevis break some time back. The pulley had been inspected after the event and put back in service. Tom Smith speculated that the pulley may have suffered some unseen damage and ultimately failed itself. Tom showed me the pulley and the entire bottom of the pulley inside the bolt spot faces had sheared out. A very interesting failure mode! I believe this is an isolated incident, I had never heard of this type of failure before.

So everyone... be careful not to overtorque the two large lateral bolts through the upper engine clevis. And check the clevis regularly for cracks that can result in premature component failure which means the top end of the engine is free to wobble, and the main drive belts can go slack, etc. This happened to a guy in Michigan recently.  No injuries to himself or pax, but significant damages resulting from rollover after his auto.

Regards

J. Mark Wolf

3/28/00

30mm  Spherical

Belt

Joe Martin

N6291K

 Date: May 28, 2000 09:38 PM 

Author: Joe Martin (mjoelinda@cs.com <mailto:mjoelinda@cs.com>) 

Subject: Secondary shaft falure with new single bearing and Pro-Drive 

Today, while on a flight to check out the lower main mast bearing,( I had changed due to high temp readings)I had climbed to 5000ft and was monitoring the bearings temp. the main mast bearing was running at 102degrees F (thats good, the one I changed went to 155 degrees F on my last flight)and the gauge for the secondary upper bearing said all was well at 122 degrees F. Suddenly the ship started to shutter in a way I hadn't felt before. I reduced power and started a slow decent,and looking for what the problem might be. By decreasing and increasing engine rpm I could tell that the drive train was still coupled,but the shuttering was definitly RPM sensitive. More RPM higher frequency shutter.I didn't know what it was but I knew it wasn't good and could get seriously worse real quick.I've always said the only time you have to much altitude is when you are on fire,but I sure wished I was closer to the ground right then. I had a lot of altitude to lose and didn't want to make things worse,so I reduced power and kept the rotor in the low green. I was over my strip so I circled keeping myself in range for an autorotation if it came to that. Seemed to take forever,and I could swear the amplitude of the shutter was increasing.My house sits several hundred feet above my strip with 4 acres of lawn so when I came around and saw I was set up into the wind I shot for the yard instead of making another circle for the strip.I made an auto-profile approach just in case, but when I ask for power it was there and I made a normal landing from a hover. I went to idle,and hopped out to have a look.The secondary drive sprocket caught my eye. It looked like it had a wobble in it,and the cogbelt seemed to be shaking more than I had noticed before. I thought it could just be the low RPM and the normal idle shake I was seeing. I ran the RPM up to about 3300RPM and checked again. Everything looked OK!! Now I was really puzzled. A good look arround didn't reveal anything out of the ordinary. Now that I was on the ground,and didn't see anything obvious I felt a little silly about my anxiety.Determined to track down what I had felt I hopped in and brought the engine up to flying RPM. The plan was to pick up to a hover and see how it felt, and if everything seemed OK, I'd fly down to the strip,land at the hanger,shut down and have a real good look at everything.

As I pulled a little pitch to get light on the skids,a loud bang from the back,and a surge in engine RPM.Before I rolled the throtle back I knew what had happened.The secondary shaft had failed! Fearing the sprocket might have fallen where it could do some major damage,

I did a quick shutdown and hopped out for a look. Sure enough, the sprocket was gone. It had dropped and had wedged where it hadn't damaged anything else. This was a secondary unit rebuilt by RotorWay recently. It had a new shaft and the new single bearing installed. I had closely monotored the upper bearing temperature with a gauge in the cockpit. It had never shown any high readings.

In light of the recent secondary shaft failures at the factory on ships using this bearing,I would encourage anyone flying with this bearing,to stop flying their helicopter until Rotorway fixes this problem.Something must be done! I was very lucky today. In fact I have been very lucky ever since this bearing was installed on my helicopter! I fly in West Virginia over very rough, tree covered mountains with very few emergency landing sites. This could have happened at a much less desirable time. I don't want to be the pilot killed that finally gets RotorWay off the dime and addressing this as a real, serious, life threatening problem. Let's be careful out there folks!

(http://www.rotorcraft.com/forums/Index.cfm?CFApp=2&Message_ID=23286)

Pre 2001

30 mm 3 bearing

chain

Craig Hook

-

3/01

30mm  Spherical

Belt  / 250 Hours

Craig Hook

Terrys Exec 90

March'01
30mm Spherical Bearing Secondary

(From Craig Hook)

I was flying a 90 with a friend, 300 ft 80 mph, 26 " MP when I heard that aweful sound again. ( For those that have not had the distinct pleasure of a secondary failure, there are 2 distinct sounds. The first is of an instant over-rev on the engine.  The second is the catharsis of filling your pants.)  Terry was flying.  There was an immediate yaw to the right but only about 20 degrees. He instinctively entered an auto, and we glided to the gently ground, flaired, leveled off and set it down.  Not even a scratch.  I think this is the first actual complete separation while in flight. The good news is that the shaft stayed captive in the inner race of the spherical bearing. Nothing flying around the engine compartment at head level. (Cog belt system was undamaged.)  Terry has over 200 hours on the shaft with the single spherical bearing setup. No temp monitoring installed. He has about 250 hours in this ship.  One point that should be made is that the ship autoed perfectly with full tail rotor authority via engine and pedals. A low time pilot or a pilot who says he will practice autoes LATER would probably not had the same outcome..
PRACTICE YOUR AUTOS REGULARLY.

3/01

30mm  Spherical

Chain??

Robin Burows Tazmainia

-

   
  (From Robin Burrows)
A machine has gone down in Tasmania.
I understand that the secondary failed (self aligning type).  Instructor and student OK.
I think that they dropped from about 10ft and were in the process of landing.

3/01

30mm Double

Chain

3/01  Rotorheads

Duane Grummett in Canada

3/01

30mm Double

Belt

3/01 Rotorheads

Scott and Brett Newhart's ship EPI HAD AS A BREAK

The upper Bearing Race spun on the shaft.
They had a temp rise and a vibration that alearted them of the issue

5/16/01

30mm Double

Belt

NTSB

N311RN EPI HAD AS A BREAK

Tail rotor belt came off in flight from loose lower bearing

   NTSB # CHI01LA141

On May 16, 2001, at 1110 central daylight time, a Parker Rotorway 162F helicopter, N311RM, operated by a student pilot, sustained substantial damage when it impacted into a field 15 miles northwest of Minneapolis, Minnesota, during an emergency landing. Prior to the emergency landing attempt, the helicopter experienced a tail rotor malfunction. Visual meteorological conditions prevailed at the time of the accident. The personal flight was being conducted under the provisions of 14 CFR Part 91. There was no flight plan on file. The student pilot operating the helicopter reported no injuries. The local flight originated from the pilot's residence at Rogers, Minnesota, at 1045.

In his written statement, the student pilot said that he was returning to Rogers, Minnesota, when he heard a "pop" and then the helicopter yawed left. The student pilot said that he lost pedal control and entered a turning autorotation. He said that at approximately 35 feet above the ground, he introduced some aft cyclic in an attempt to perform a run on landing. He said that the helicopter "spun violently to [the] right". The student pilot said he added full left [control pedal] and down cyclic. The helicopter dropped to the ground.

A Federal Aviation Administration inspector examined the helicopter at the student pilot's residence. The inspector observed that both skids were collapsed, the tail boom was bent upward, the bottom vertical stabilizer was crushed upward, and the tail rotor was bent aft. Control continuity was confirmed.

An examination of the helicopter's belt drive system revealed that the lower shaft bearing in the secondary drive unit to the tail rotor was loose and the tail rotor drive belt had come off.

9/27/2002

35mm  Sperical

Belt  45 hours

Rotorheads

Mclaughlin

       From: Doppler John  9/21/2003

The flight before my 35 mm secondary broke, I also noted the "black dust."  Rotorway was never able to attribute what this material was, but I suspect something was wearing prior to the failure.

Tom's 35mm Secondary Shaft

This is a shot of John's Tail boom

10 /01/01

30mm  Double

Belt 113 hours

Jerry and Linda White

N8270U

NO  NTSB
Their shaft broke in a hover
between the 2 bearings

10/07/02

30mm Double

Belt  153 hours

Mark Wolf

N1955Z

NTSB Identification: CHI03LA006

Mark's shaft broke at altitude and he was running his belt
at a lesser tension than Pro-Drive's specs call for.

Mark got 153 hours on his shaft before it broke which is more than most so maybe its a good thing and perhaps it made no difference at all.

 The docket is stored in the Docket Management System (DMS).
14 CFR Part 91: General Aviation

Accident occurred Monday, October 07, 2002 in Gregory, MI
Probable Cause Approval Date: 6/25/2003
Aircraft: Wolf Rotorway Exec-162F, registration: N1955Z
Injuries: 1 Uninjured.

While in cruise flight, the secondary drive shaft failed completely and power to the main rotor was lost. The pilot executed an autorotation to an open field. However, on landing, the forward speed was higher than planned and the helicopter flipped forward and rolled to the left. The pilot stated that on his return to the airport, the secondary shaft bearing temperature started to rise. Once the bearing temperature reached 150 degrees Fahrenheit, the "drive let go", causing the engine RPM to surge. A post-accident inspection revealed that the secondary shaft had failed at a point inside the upper bearing race. Due to a history of failures of this secondary shaft design, Rotorway had released a 35 mm diameter shaft configuration in April 2001. The preceeding shaft diameter was 30 mm. An advisory bulletin was issued by Rotorway in May 2002. The 30 mm configuration was installed on the accident aircraft. In addition, the accident aircraft incorporated an after-market cog belt drive system between the secondary shaft and the main rotor shaft. The basic Rotorway design utilizes a chain drive system.

The National Transportation Safety Board determines the probable cause(s) of this accident as follows: 

Failure of the secondary drive shaft, which resulted in a complete loss of power to the main rotor, and a high forward airspeed on touchdown, causing the helicopter to flip forward.

NTSB # CHI03LA006

On October 7, 2002, approximately 1830 eastern daylight time, an amateur-built Wolf Rotorway Exec-162F helicopter, N1955Z, owned and piloted by a student pilot, was substantially damaged when it lost power to the main rotor and executed an auto-rotation into an open field near Gregory, Michigan. The flight was being conducted under 14 CFR Part 91 and was not on a flight plan. Visual meteorological conditions prevailed at the time of the accident. The pilot reported no injuries. The flight departed the Livingston County Airport (OZW), Howell, Michigan, at 1800 edt for a local flight and was returning to the airport when the accident occurred.

The pilot stated that the "secondary shaft bearing temperature started to rise." He reported that approximately one minute "elapsed from the time the [bearing] temperature increase was noted, to the time the temperature reached 150 degrees Fahrenheit," and the "drive let go", causing the engine RPM to surge. At this point, the pilot noted that all power to the main rotor was lost and he initiated an auto-rotation. He stated that, although the touchdown point was as planned, the forward speed was faster than intended and the helicopter flipped forward and rolled to the left.

Following a post-accident examination, the owner/pilot reported that the secondary drive shaft had failed completely at a point inside the upper bearing race. He noted that the shaft had been in service for approximately 155 hours at the time it failed.

Due to a history of secondary drive shaft failures, Rotorway had released a "re-designed configuration" in April 2001. This configuration increased the shaft diameter from 30 mm to 35 mm. The 30 mm shaft was installed in the accident aircraft.

According to Rotorway, owners were notified of the availability of the new shaft design by an Advisory Bulletin in May 2002. In part, this bulletin states: "The larger [35mm] secondary shaft was supplied with new aircraft and as an upgrade to existing aircraft over a year ago. ... It is the suggestion of Rotorway International that all Rotorway owners consider upgrading to the 35mm secondary shaft." The owner/builder stated that he had planned to upgrade to the 35mm shaft over the coming winter.

In addition, the accident aircraft included an after-market main rotor drive system which incorporated a cog belt in place of the chain drive.

10/19/02

30mm ?

??

Jimmy Johnson

N162AZ

NTSB Identification: LAX03LA011

14 CFR Part 91: General Aviation
Accident occurred Saturday, October 19, 2002 in Tucson, AZ
Aircraft: Rotorway 162F, registration: N162AZ
Injuries: 1 Uninjured.

This is preliminary information, subject to change, and may contain errors. Any errors in this report will be corrected when the final report has been completed.

On October 19, 2002, about 1150 mountain standard time, a homebuilt Rotorway 162F, N162AZ, landed hard during a forced landing approximately 5 miles south of Ryan Field, Tucson, Arizona. The owner/operator was operating the helicopter under the provisions of 14 CFR Part 91. The private pilot, the sole occupant, was not injured; the helicopter sustained substantial damage. Visual meteorological conditions prevailed and no flight plan had been filed. The flight originated at an unknown time from Ryan Field.

In a phone interview, the pilot stated that a mechanical failure occurred at altitude resulting in an immediate autorotation.
He further stated that the secondary drive shaft broke in half resulting in the engine disconnecting from the rotor.
During the forced landing, the aircraft rolled onto its left side after hitting a bush.

1/1/03

30mm  Double

Belt  16 hours

MSN Site

Tom Uppman

Name:  Tom Uppman

Address:  19701 261st. Avenue
City:  Belle Plaine
State:  MN
MN  zip:  56011

Registration:  N140GW
Model of Ship:  162F
Serial Number:  6300
Date Purchased:  February, 1997
Date Certified:  12/07/02

Tom is currently running a 35 mm Spherical shaft with a chain drive
because his 30 mm shaft broke at 16 hours with belt.

------------------------------------------------------------------------

Date: 12/11/2004  

It was a 2 bearing with the belt. It happened at high noon on January 1, 2003, temperature was 20 degrees. I was in a hover. Came down in my front yard and bent pilot skid. No NTSB report. Spurling has my broken shaft. See photos.

Tom Uppman

Pictures of Toms Secondary Shaft

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Secondary Status Update
Message 19 of 23 in Discussion    
From: Uppie Sent: 12/10/2004 2:28 PM 

Howdy

I am runing the factory chain and 35 mm shaft. I have 160 hours TT. Original 30 mm shaft with belt broke at 16 hours. Chain was replaced at 125 hours and at that time I installed the new factory seal on the front main shaft. 35 hours now with one chain adjustment and absolutly NO oil leaks or misting at all. So far..........So good!!

Were Assuming thats a total amount of hours on the ship less the first 16 which would make it 144 running the chain Drive setup with a new chain installed at 125 hours.

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Secondary Status Update
Message 22 of 23 in Discussion
From: Uppie Sent: 12/12/2004

Temps are ~120-145 on the temp gauge.
The 170 dot on the temp strip is popped.

I put 1 can of STP in with 1 quart of oil (80% oil and 20% Slick 50). My elevation is 850 feet and it is usually cool, i really didn't notice any perfromance difference.

2/05/03

35mm Spherical

Chain  561 hours

NTSB

Factory Ship

NTSB Identification: LAX03LA084

Shaft Broke on Lower end and was Blamed on 2 Seperate Tail Rotor Strikes

From: Matt Haasen    Sent: 2/13/2003 5:32 PM

14 CFR Part 91: General Aviation
Accident occurred Wednesday, February 05, 2003 in Casa Grande, AZ
Aircraft: Cobb International Rotorway Exec 90, registration: N9876D
Injuries: 2 Minor.

This is preliminary information, subject to change, and may contain errors. Any errors in this report will be corrected when the final report has been completed.

On February 5, 2003, at 0815 mountain standard time, a Cobb Rotorway Exec 90, N9876D, made a hard landing after experiencing a loss of tail rotor authority at the Phoenix Regional Airport (A39), Casa Grande, Arizona. Cobb International operated the helicopter as an instructional flight under the provisions of 14 CFR Part 91. The helicopter was substantially damaged. The certified flight instructor (CFI) and the private pilot undergoing rotorcraft category training received minor injuries. Visual meteorological conditions prevailed for the local area instructional flight and no flight plan had been filed. The flight originated from Stellar Airpark (P19) about 0750, and was scheduled to terminate at P19.

According to the CFI, the purpose of the flight was to practice pattern work and autorotations. The CFI stated that the student had done approximately four landing approaches. During the accident approach, the CFI reported that they had made the base turn and had leveled off when they heard a "bang." The CFI took the flight controls and initiated a turn to an open area for an emergency landing. During the autorotation, he raised the collective to check for aircraft controllability. The helicopter yawed to the left, at which point he lowered the collective and decided to continue with the autorotation. As he pulled collective to "cushion the landing" the helicopter yawed to the left, landed firmly on the ground, and rolled over on to its right side.

According to a Federal Aviation Administration (FAA) inspector who examined the helicopter,
the secondary drive shaft appeared to have sheared about midspan.
The secondary drive shaft is being sent to the Safety Board for further examination.

LAX03LA084

HISTORY OF FLIGHT

On February 5, 2003, at 0815 mountain standard time, a Cobb Rotorway Exec 90, N9876D, made a hard landing after experiencing a loss of tail rotor authority at the Phoenix Regional Airport, Casa Grande, Arizona. Cobb International operated the helicopter under the provisions of 14 CFR Part 91. The helicopter was substantially damaged. The certified flight instructor (CFI) and the private pilot undergoing rotorcraft category training received minor injuries. Visual meteorological conditions prevailed for the local area instructional flight, and no flight plan had been filed. The flight originated from Stellar Airpark, Chandler, Arizona, about 0750.

According to the CFI, the purpose of the flight was to practice pattern work and autorotations. The CFI stated that the student had done approximately four landing approaches. During the accident approach they had made the base turn and had leveled off when they heard a "bang" in the aft section of the helicopter. The CFI took the flight controls, and initiated a turn to an open area for an emergency landing. During the autorotation, he raised the collective to check for controllability. The helicopter yawed to the left, at which point the CFI lowered the collective and continued with the autorotation. As he pulled collective to "cushion the landing" the helicopter yawed to the left, landed firmly on the ground, and rolled over on to its right side.

According to a Federal Aviation Administration (FAA) inspector who examined the helicopter, the secondary drive shaft appeared to have sheared about midspan.

AIRCRAFT INFORMATION

Helicopter main rotor and tail rotor drive system:

The engine and secondary drive shaft are mounted vertically and parallel to each other behind the cockpit. The engine drives four v-belts, which in turn drive the secondary drive shaft. The secondary drive shaft drives the main rotor via a chain drive on its upper end. Attached to the lower end is an engine cooling fan and a pulley that drives a series of three v-belts. The v-belts extend to two pulleys mounted in series along the interior length of the tail boom; the last belt drives the tail rotor. Two bearings, one above and one below the main drive pulleys, support the secondary drive shaft. A lock collar is attached to the shaft directly below the lower bearing. The drive shaft extends below the lower bearing where the tail rotor pulley and the engine cooling fan attach.

The secondary drive shaft fractured between the lock collar and the inner race of the lower bearing.

Examination of the helicopter's maintenance records revealed that the airframe had 2,937 operational hours,
and the secondary drive shaft had 561 hours of service.
The secondary drive shaft had been visually inspected as part of the 100-hour scheduled servicing. At 2,697 airframe hours the helicopter was in a rollover mishap.

The secondary drive shaft (315 service hours) was removed and inspected during the ensuing helicopter repair activity.

The logbook also recorded that this airframe had been in involved in two tail rotor strikes, which affected this secondary drive shaft; the first at 2,678 airframe hours and the second at 2,804 airframe hours.

Tail rotor failure procedures:

The FAA Rotorcraft Flying Handbook (FAA-H-8083-21) discusses general emergency procedures appropriate to an antitorque system failure. "If a tail rotor failure occurs, power has to be reduced in order to reduce main rotor torque. The techniques differ depending on whether the helicopter is in flight or in a hover, but will ultimately require an autorotation. If a complete tail rotor failure occurs while hovering, enter a hovering autorotation by rolling off the throttle. If the failure occurs in forward flight, enter a normal autorotation by lowering the collective and rolling off the throttle. If the helicopter has enough forward airspeed (close to cruising speed) when the failure occurs, and depending on the helicopter design, the vertical stabilizer may provide enough directional control to allow you to maneuver the helicopter to a more desirable landing site."

The Rotorway Exec 90 Flight Manual states four steps for a "Tail rotor failure during forward flight."

"K. Tail rotor failure during forward flight:
1. Failure is usually associated by right or left yaw which can not be corrected by applying pedal.
2. Immediately enter a shallow descent into the wind.
3. Adjust the collective and the throttle to extend the glide if sideslip is not excessive and the aircraft does not tend to spiral. Cyclic and collective are used to limit sideslip angle.
4. Select landing site and perform a run-on landing using throttle to maintain heading."

There are no steps or discussions in the manual that addresses what to do if the sideslip is excessive or the helicopter tends to spiral.

TESTS & RESEARCH:

Secondary drive shaft:

The secondary drive shaft has been under scrutiny by the manufacturer. Before February 2000, the secondary drive shaft was on a 100-hour inspection interval and a 1000-hour recommended change out schedule. After February 2000, the manufacturer modified the recommended maintenance to a 100-hour inspection interval and a 500-hour recommended change out schedule. This was a result of previous secondary drive shaft concerns associated with the upper portion of the shaft. The 100-hour inspection procedure is a visual inspection only. The manufacturer released three Advisory Bulletins (A-32, A-34, A-38) since July 1998 addressing installation, inspection, and shaft design change issues.

The failed secondary drive shaft had a total of 561 service hours.
The manufacturer's recommended change out time is 500 service hours.

The FAA does not issue type certificates for experimental category aircraft and 14 CFR Part 43 - Maintenance, Preventative Maintenance, Rebuilding, and Alternation regulations do not apply. According to the manufacturer, the 500-hour recommended change out is over two factors of safety below the engineering analyzed operational safe life of the shaft. The manufacturer was operationally performing an expanded shaft life test program utilizing this secondary drive shaft.

The Safety Board Materials Laboratory, Washington, DC, examined the secondary drive shaft, and prepared a factual report. The secondary drive shaft fractured between the lock collar (located just above the tail rotor drive belt pulley) and the inner race of the lower bearing. The lock collar was held onto the shaft by a set screw, and the lower bearing had been assembled with Locktite between the inner race and the secondary shaft.

Examination of the shaft in
the area contacted by the lock collar (on the lower portion of the shaft)

revealed fretting and corrosion that was primarily concentrated in two circumferential bands.

One was associated with the upper edge of the lock collar, and one was associated with the lower edge of the lock collar. Examination of the mating faces of the shaft fracture revealed that almost the entire fracture surface was on a flat plane. It intersected the exterior surface of the shaft at a 90-degree angle, and most of the fracture contained crack arrest positions,

indicative of fatigue cracking.

The origin area was at the lower edge of the fretting and corrosion area on the inner race of the lower bearing.

7/03

35mm   Spherical

Belt  55  hours

Jim Liss

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7/16/04

30mm   Double

Belt  97 hours

Clell n Donna

N162FA

NO NTSB

Ours broke July 16th 04 at Homers Fly In.

The bearing temp gauge read 142 when it broke

Now heres an interesting site to behold.

If you look very close in these pictures you can see what looks like several symmetrical rows of U shaped scratches.  They seem to be in rows of 3 around the entire circumference of the shaft where the upper bearing covered the shaft.  I'm not sure but I think these marks were made upon the initial factory assembly and may have attributed to our shafts early demise.

We have no idea lol

This is what a bearing seal blow out looks like, we've no idea whos ship it is.

5/15/05

35mm   single bearing

Chain 65 hours Then the  Pro-Drive Cog Belt for 72 hours 137 TT Hours in all on shaft

Jack Elvin

RotorwayFun.MSN Site

From: Jack  (Original Message) Sent: 5/17/2005 10:05 PM 

 
Last Sunday I experienced a 35mm secondary shaft break in flight.
I was able to auto rotate into a field of tall grass with minimal damage, only to the landing gear.

My helicopter has 137 hours TT, I originally had a chain for the first 65 hours
and went to the Pro Drive belt (72 hours on the belt drive.)

I think that it is important to get this information out as there are probably people flying Execs with the same combination of components, thinking that it is safe, as I did, since there have not been any 35mm breakages for a couple of years.

I hope this doesn’t scare anyone away who is considering a Rotorway, I think they are great ships and loads of fun, I wouldn’t even consider not owning one. I will be getting a new secondary, one of the 40mm aftermarket models and some new landing gear components and will be back in the air soon.

In retrospect, in the last couple hours before the break it seemed as the belt was making a louder noise than usual. Possibly this was because of the sprocket wobbling. Another thing I noticed is that when you auto without a secondary it takes more collective, I kept finding rotor RPM in the yellow.

It is amazing how a maneuver that is so much fun to practice can bring so little pleasure when actually put into action.

Jack Elvin

Message 7 of 7 in Discussion    
From: Jack Sent: 5/20/2005 8:36 PM 
It is being examined by an expert at this time and he will have some better photos later.  I guess we already know what the problem is;  it is unwise to  use a belt with a 30mm or 35mm shaft!       

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break5.jpg

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