Prop choice

[WWhunter]

Never argue with a wife....especially when she tells you to order the new prop while it is on sale!!!! Whirlwind had a discount valid through the 2nd of Dec. and since the spousal unit was here visiting me for Thanksgiving, she TOLD me to go ahead and order it. Called WW and they had one is stock and shipped it out that day. It arrived a few days later. WOW!!! I thought my 70" WW was a nice looking prop, this new 75" is even nicer. Carbon fiber material itself can be seen through the clear coat that is on the prop. Nice white tips, and the prop looks almost like it belongs on some kind of high speed Lancair/Glasair with an IO-550!!! Couldn't believe how much bigger just 5" of blade can appear.
I have been told size matters! I am talking props here!

I couldn't wait for more reports on the Prince or Catto, just too impatient I guess.

I will use the GSC (maybe) on the Kitfox for a while and then take the 70" WW off my RANS S7 and put it onto the KF. Put the 75" on the RANS since it has the Zipper motor and 29" AkBushwheels. I think the KF with the smaller tires (currently has the 21" Nancos) might be too close to the ground for the 75" prop. First thing is to get the plane flying I guess and go decide what I want to do.

[kitfoxnick]

You are probably aware of some of the GSC problems. I think many people have had good success with them. There have been some instances of them shedding blades. That's why GSC put a 5 year 500 hour TBO. I think most of the problems were from over torquing or corrosion.

Here is a link to the Service Bulletin http://www.ultralightprops.com/bulletins/051799_sb.pdf


May 17, 1999
GSC SYSTEMS SERVICE BULLETIN

AFFECTED MODELS All GSC Systems 2 and 3 blade ground adjustable
GSC Systems has been in the business of producing quality props for over 15 years for many types of aircraft.
Over the course of these 15 years, it is possible that the original aircraft and/or the GSC propeller may have
changed ownership several times. During the transfer of ownership often the instructions and maintenance
procedures of our propellers have been lost. To that end, many propellers receive incorrect maintenance.
The most critical assembly procedures of our propellers are that the hub and root ends not be tighten past the
recommended 100 in/lb torque specification. It is also possible that due to the over tightening of the attach
bolts, that the space between the aluminum hub halves is no longer visible. The result of this improper assembly
or maintenance could result in premature blade failure resulting in either injury or death.
If you do not presently have a set of GSC assembly instructions please contact GSC Systems and one will be
forwarded to you.
REQUIRED SERVICE Immediate inspection
1. Inspect to insure that a visible gap between the Aluminum hub halves is detected. If no gap is visible contact
GSC Systems.
2. If you are the initial and original owner of a GSC Propeller, are you certain that the hub has never been
torqued past the 100 in/lb MAX torque specification, if not contact GSC Systems.
3. If you are not the original owner of a GSC propeller can you be assured that the GSC propeller hub has
never been torqued past the 100in/lb Max torque specification, if not contact GSC Systems.
GSC SYTEMS TBO
GSC systems have documented user times of over 1000 hours but due to the nature of the exchange and selling
of our product we are implementing a 500 or 5 year TBO for all GSC propellers.
If you require further information please feel free to contact GSC Systems. Our goal is to continue the supply
of a quality and safe product.



If it were me and I was going to use this prop I think I would put some sort of cable around the motor mount and around the firewall. If a blade departs there would be a good chance that the unbalanced prop would rip the engine off. With the cable you could keep your CG and make an emergency landing.

[tommg13780]

We just had an incident (Friend) that involved a GSC 2 blade with some VW derived engine in a direct drive situation. The blades were trimmed short to stay within 80% mach 1 tip speed at around 3600, full throttle RPM. Unfortunately the blades separated form the hub after about 4 hours flying.
Fortunately both blades left the engine simultaneously. The motor mount fractured at one point but three points did not fail. The engine stayed with the airplane revving way high with no load until ignition was killed.
The pilot (300+hour student) was able to return to the field and dead stick land without damage to the Kitfox 1. As I understand it when the engine separates from the airplane the resulting imbalance will make the airplane hopelessly uncontrollable. This incident has pretty much killed my interest in direct drive VW engines along with GSC Propellors. Pobably there is an equation out there that could have told these experimenters that this was going to be risky business. Perhaps the inertia value was exceeded?
Nick's comments caught my attention because "shedding blades" is such a harmless sounding expression.

[WWhunter]

Okay, you guys have just convinced me that to remount the GSC prop to this plane could be hazardous to my health. The prop looks like new and was only test run for a couple of hours so I doubt it would have any issues but my life and the well being of the plane are more important than keeping the prop on the plane.
Since I have two other props I can use I will 'flip a coin' and see which one I will use. Most likely the 70" Whirlwind will win.

[Av8r_Sed]

This incident has pretty much killed my interest in direct drive VW engines along with GSC Propellors. Pobably there is an equation out there that could have told these experim

Tommy,
I understand your personal choice to avoid a risk. On the other hand, It wouldn't be appropriate to reject all VW direct drive derivatives and all GSC props due to one incident with a combination of the two on a Kitfox. There have been many postings here indicating direct drive VW derivatives might not be a good match for a Kitfox, while there are others like Sonex drivers who wouldn't have anything else. Many Kitfox pilots have flown behind GSC props for many hours. With good maintenance and storage they can be very reliable and smooth.

The upshot is, it would be best to work with the prop manufacturer and heed their advice on good and not so good engine/prop combinations.

[tommg13780]

Paul, I can appreciate your point of view. I've had many (200-300) trouble free hours flying with GSC on a rotax 2 stroke/gearbox application.
For some reason, possibly a naturally occurring fracture of 1 blade, I made an inquiry for replacing that one blade and the GSC representative advised me to order 3 new matching blades as the only feasible option. Of course that would cost equal or greater than a new Warp, or IVO.

I believe this "shedding of blades" incident was somewhat disturbing to me because it could be something I probably would have tried myself. Those blades were both retrieved and they both looked like they were in a vise and someone carefully ran a chainsaw vertically from the inboard end down to the thru bolt slot. I found that mental image to be rather emotional. It was kind of a "foxhole" moment when the guy next to you takes a head shot.

I'm sorry if my preference here seems irrational but to some extent perhaps it is. I really get a lot of pleasure from the Kitfox buying, selling, building and flying activities and would hate to see the whole thing spoiled by a senseless incident.

[jamesmil]

want to weigh in on this topic and give my 2ct worth. have 250+ hrs on the keiv prop with no problems and very happy with the performance on our ss7 with 912 uls and 850 tires. routinely see 1200 to 1300 ft per minute climb and 113 mph ias, at 5300 rpm and very smooth. Ted Bryant at b&b and i have become good friends and I am going to be doing some testing on the new keiv electric veritable pitch hopefully soon and will post the results here when done. that said the w/w wins the sex appeal contest hands down, best looking prop out there.