Good post, Wayne. I agree with all of it. I tried twice to fly with my canopy open, even making one takeoff with it open. I didn't like it! It was too damn windy, even blowing the fiberglass insulation from underneath the RH instrument panel. Most importantly , it was darn near impossible for me to get the canopy closed and locked. I tried it solo and with a buddy. Too much to do flying the airplane - even down to 75 mph- while squirming around messing with the latches. At the time, I didn't even consider that the darn thing could fly off the airplane!!Having it hit a rudder or the stabilizer could be fatal! I will not fly my ALON with the canopy open. Also, the two 2" snap ring vents on my windscreen give me quite a bit of cooling air when needed. Not always enough, but preferable to losing a canopy in flight.
Semper Fi
DON BOWEN
[EMAIL PROTECTED]
From: [EMAIL PROTECTED]
To: [EMAIL PROTECTED], [email protected]
Subject: Re: [COUPERS-TECH] ALON CANOPY LOSSES
Date: Sat, 10 Jun 2006 00:49:28 EDT
Don,Since nobody else responded, I'll pass along what I know about the Alon canopy situation.I have heard through the grape vine of two, and possibly three Alons losing their canopies in flight. I heard about these incidents third or forth hand, with no other information provided, and in fact, I don't have any real evidence that any of these incidents ever happened. No N numbers, no locations, no details. Maybe one, two or all three incidents did happen, but I personally haven't heard any details about them at all.Having said that, I have never really been comfortable flying my Alon with the canopy open because of the way it is attached to the airplane when it is in the open position. When the canopy is closed and latched from the inside, it is held in place by the two steel latches, and it is secured in the back by a metal and nylon fitting that is trapped in the metal slot in the rear window structure. This rear fitting only secures the rear of the canopy in the vertical direction, not in the aft direction. There is no way that he canopy is going anywhere when it is latched closed unless the latches are broken or the screws securing the latches fall out.With the canopy open, it's a different story. The only thing holding the canopy on the airplane with the canopy open is the fact that two small nylon rollers have a larger diameter than the slot in the canopy tracks that are mounted in the fuselage side walls. Each of these two nylon rollers is attached to the canopy frame with a single screw, a couple of washers, a spacer and a single nut. The screw acts as the axle for the roller. These nylon rollers are cylindrical in shape, and they wear over time. As they wear, the diameter of the roller gets smaller, and the length of the roller gets shorter. If the diameter gets small enough, the roller can pop out of the slot in the canopy track. If this happens in flight, the relative wind would probably rip the canopy off of the airplane, because the other roller would not be strong enough to keep the canopy in place, and the rear of the canopy is not secured in the fore-aft direction. (Although I have seen one picture of an Alon with an aft stop in the rear canopy track between the rear windows. My airplane does not have a stop in this track.)I suppose that if the screws attaching the phenolic blocks were to fall out and the phenolic blocks were to move back, then the canopy rollers would be able to come out of the tracks that way as well.On my airplane, the canopy rollers were worn enough to where the canopy was sitting lower than it was supposed to be which caused some chafing and alignment problems when moving the canopy fore and aft. I ordered a set of rollers from a supplier, and they were not made correctly (they didn't fit at all - I was not surprised at all), so I had a machinist make a set for me to my dimensions. Now the canopy sits exactly where it should and lines up properly. (If you want instructions on how to determine the proper roller diameter, let me know and I'll send you some info on how I did it.)Another concern that I have about flying with the canopy open is that any rearward force on the canopy that is caused by the relative wind is handled solely by those two screws that the rollers are mounted on. This is due to the fact that the only thing that stops the canopy from traveling further aft is that the rollers are stopped by two phenolic blocks that are mounted in the rear section of the side canopy tracks. These screws are mounted in holes drilled in the aluminum canopy frame, and the aluminum canopy frame is only about 1/8 inch thick (or maybe 3/16ths) where the screw holes are. The screw and roller assemblies are about 1 inch long, so basically you have two one inch long screws that are mounted in 1/8 inch thick aluminum keeping the canopy on the plane in a 100 mph wind. With all the dancing and vibration that the canopy is subjected to when it is open in flight, I get concerned about metal fatigue in the aluminum canopy frame around the screw holes.I would feel a whole lot better about flying the Alon with the canopy open if the canopy was positively locked in place in the open position. I just don't trust the design of the canopy attachment when the canopy is open.As a side note, on the few occasions that I have flown my plane with the canopy open, the air turbulence in the cockpit gets pretty old in a hurry. There's lots of wind, and it makes opening and closing a chart a real problem. In addition to that, I wear contact lenses, and wind and contacts don't really go together too well. My friend's 415C on the other hand is a pleasure to fly with the canopy open. With the original window setup, you can open the windows as much or as little as you want, and even with them wide open, the air turbulence in the cockpit seems to be a fraction of what I get in the Alon.My advice would be that if you plan to fly with the canopy open (and several folks do it all the time), make sure that your canopy rollers are not worn, make sure that the screws, nuts and washers are tight and in good shape, make sure that the phenolic blocks are in good shape and properly secured, and watch the canopy frame for any sign of stress or cracking around the screw holes. If you check all of that and it's all in good shape, then I'd go fly with the canopy open and not worry about it too much.As always, just my opinion, so take it for what it's worth.Best Regards,
Wayne DelRossi
Alon N5618F
Hours logged since restoration: 147.1
