In-Flight Greenhouse Separation

C

cubeleo

New member
Yesterday I was flying aerobatics in my 1980 8KCAB and as I pulled from level into an immelmann, I heard a loud bang followed by vibration and wind. I slowed way down, assessed my control of the airplane, and began to return to land. I then realized my greenhouse window was completely gone. When I got on the ground, I saw the extent of things. The rear windows had blown in, with the left one shattering. Pieces of window had gone back and punched little holes and tears in the fabric along the empennage, and worst of all, a tear all the way through the stabilizer with a large dent in the trailing edge tubing. Inside the cabin were large shards of the side windows.

I've heard here and there that the greenhouse coming out has happened to people in the past. Can anyone tell me of their experiences with this, and/or what the cause is? I'm still absorbing the whole event and now I'd like to collect information and get everything fixed. Thanks for any information,

Aaron Dwyer
N345AS
 
Wow. It's too bad this board doesn't have someplace to post pictures. This is something certainly worthwhile to look at.
 
Dear Ray:

Club members can post pictures; when creating or editing a post, click on the "Upload attachment" tab at the bottom, browse for the picture, click on "add the file", insert any comments on "File comment" line, then click "Place inline"

Let me know if you have problems.

Regards,
 
ernstmfg:

I have many photos of the damage.

Robert:

The forum says in red that I do not have permission to view the photo you attached, and I don't see any controls to attach photos myself. Do I need a higher level of status?

Aaron
 
Several months ago I spoke with a gentleman who had stopped by my hangar and related a story about losing his greenhouse on a Citabria.

A friend of his had purchased a Citabria in Nebraska and as he had no Citabria time asked if he would go with him to pick it up and ferry it to his base in Western Co. He agreed.

They picked up the Citabria and on the way back his friend asked to see a loop. They did one and commented that was fun, lets do another. On the back side of the second loop the greenhouse separated along with the fabric 2/3 rds of the way to the tail. Their first reaction was to slow down and when they did the a/c became uncontrolable and went into severe gyrations which resulted in a loss of a lot of altitude. They eventually recovered with an airspeed of about 140 mph and again decided to slow down to assess things. When they reached 120 mph the gyrations started again with another loss of altitude. They were able to recover again with not much altitude left and started a slow descent with full power toward Ft. Collins airport and managed to stay above 120 mph until touch down with no further damage.

The gentleman who related this story to me said that when they approached the 120 mph point the aircraft started to get sloppy so they kept the airspeed above that number and were lucky enough to have an airport close by the had enough runway to land at that speed.

Second hand story, but one I had heard before, just not from the pilot that it had happened to.

Ron
 
Back in the early 80's I lost a green house out of a 7KACB. I was doing a low level, high speed pass and it came out on the pull up. The aircraft was controlable but did have a very different feel to it. Initially I thought I may have had a structural failure and loss of power because I could not hear the engine over the wind noise. I was next to a runway and was able to land within seconds. Only the greenhouse was missing... no other damage.
 
I know of a 8KCAB that lost the left rear window. The damage was limited to the loss of the window only. The aircraft had pulled vertical and the nose was yawed to the left when the window popped out. Our speculation was the yaw created a low pressure area that contributed to pulling the window out. The window was replaced and the aircraft has +600 hrs and a lot aerobatics since then without problem. The airplane had less than 100hrs at the time of the incident so a manufacturing flaw was assumed to be the most likely culprit.

I find it odd that both sides of your greenhouse windows failed. Do you think one blew in which caused the other to fail due to air pressure or being struck? Have you tired to develop a sequence of events from the damage or evidence remaining?
 
wpbarnar,

I am not exactly sure of the sequence of events as it all happened in a big "WHUMP", but from the looks of it, the top skylight (or greenhouse) came up and out, warping up the top wing skins and leaving behind only a tiny cracked triangle of plexiglass at the trailing edge. Then, I think the sudden drop in pressure in the cabin caused by 6 square feet of window leaving quickly caused the side rear windows to pop inward, because the left rear was half missing with lots of broken clear plexi in the rear cabin after the flight (but no tinted plexi from the skylight--only small pieces of that were found embedded inside the left horizontal stabilizer) and the right rear window was not broken but its bubble was inward instead of outward.

By the way, now that I'm replacing the skylight, has anyone here tried a non-tinted skylight? Seems like it would be wonderful for visibility but potentially annoying on a hot day.
 
I replaced the top deck wood and skylight on my 7ECA and used clear plexiglass. It is nice for the visibility but it can get very hot on a sunny day. I'd keep it clear though if I did it again.
 
ak_citabria,

Thanks for the info. The clear seems like it'd be great on all but the hottest of days. I imagine night flight with it is a joy. I've heard mention of a shade that sticks up there with static electricity that sounds nice for hot days and cross country flight.

My mechanic also said there is a new kind of plexi that is clear but with UV protection that might help block some heat.

Aaron
 
I own a share in a 1995 8KCAB and one of the fellow owners had the left rear side window pop out during a four point roll this spring. Fortunately it did not come all the way off but enough to create a lot of buffeting and a bunch of noise. Our AME was able to re-secure the original window which has remained secure since.
 
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