Wing Skin Separation

11-13-2009, 06:39 PM

Mike | Exclamation Wing Skin Separation

I recently received a call from Phil DeRidder. It is great to know he is out of the hospital and doing as well as can be expected. I hope I speak for all wishing Phil a speedy recovery. We touched upon his incident with the plane. Although he has not seen the plane since the incident he mentioned that he will be going to visit the plane soon and will forward or post pictures when they are available. At this point nothing definitive has been issued or published from the Canadian transportation board. From conversations I have had, there seems to be strong indications of delamination of the top wing skin from the top of the wing spar. The issue seems to focus in on the unfinished wings that were delivered from Chili. There is a possibility that wing spar(s) were shipped from Chili with peel ply on the top of the spar.

I know of three builder alerts that were issued (look below for copies);

* October 5, 1992 deals with deliveries during 1992 that may be susceptible to leaks through the roving thread of the unidirectional plies of the wing spar.

* August 1994 deals with Peel Ply on the wing rip cap strip.

*April 22, 1997 deals with Kwick Kit Owners Only and incomplete bonding of the wing top skin.

How does one check the wings? It has been suggested that the following might be a good start:

1- As noted in Builders Alert-1, April 22, 1997, check the wings for differences in sound and vibration.

2- Check for any cracks along the leading edge and top cap of the spar where the skins are attached. Open the inspection plates and check the spar and ribs.

3- Check for fuel leaks:

A- Behind the wing spar, top and bottom along the entire length.

B- Inside the wheel wells at the wing root.

This has been published to informed all of potential problems that should be checked before your next flight.

If you can add anything for testing and solutions, Please feel free to add to this post.

The following pictures are not the wings involved in the incident. They are here to get some sense of what the unfinished wing looks like.

Click on the attached files below to open them. You can save the alerts by going to File - Save

11-13-2009, 10:52 PM

tthunne | Skin separation

Mike:

Thanks for keeping us up to date with the obviously serious potential that this accident suggests may exist.

Tom Thunnell

11-16-2009, 03:24 PM

jar59nh | Wing Skin Separation

I am a little confused. Is the wing skin separation due to the forces of the accident or did it happen prior to the accident?

Normal sanding of any surface prior to bonding should tell you if you still have peel ply installed. It can 'hide' under a layer of resin and appear to be just another layer of glass. Normally the peel ply is left on until you're ready to bond as freshly removed peel ply provides a great surface to bond to.

Regards,

John

11-16-2009, 06:12 PM

Mike | Default

I recently received the following:

Here is the picture of the left hand wing we spoke about.

Most of the upper spar cap is missing and has not been recovered as yet.

Various sections of peel ply were found on the upper wing skin. The

majority is believed to be with the upper spar cap.

In the picture the upper wing skin is standing up. The white tape at

about the center of the picture is peel ply.

11-17-2009, 09:43 AM

Fred Lohr | Default

ok, so was the peel ply left attached to the entire undersurface of the rear wing skin and was unoticed, or was it attached to the top of the spar cap? The reason i ask is that it would be relatively easy to check the underside of the wing skin to see if peel ply was still attached to the entire surface, but pretty hard to check if peel ply was sandwiched in where the skin is bonded to the spar cap or rib caps.

11-17-2009, 04:59 PM

Mike | Default

It is my understanding that the separation happened in the air. I also belive the wings were shipped from Chili with peel ply on the rib cap. I do not know if the peel ply was on the skin when shipped.

01-18-2010, 12:15 AM

tthunne | Wing Skin

After examining the cap strips on my Kwick Kit wings I find it entirely plausible that someone would bond the skin over existing peel ply. My cap strips present a very shiny surface, they were evidently cut from a sheet that had been vacuum bagged. Sanding the shiny surface such that it would be ready for bonding produced no hint of the peel ply underneath. I always assumed that peel ply was present and indeed it was but if you were not of that mindset you could easily miss it. There was no hint of its presence on the edges and it required the point of a box knife to lift it away from the surface. It was an extremely light weight peel ply through which the resin had bled such that enough was present to allow relatively rough sanding without uncovering it. There was no peel ply on either the main or rear spar flanges.

T. Thunnell