D-cell

Share your thoughts, photos and general help to all builders

Postby yankeflyer » Sun Oct 01, 2006 8:45 pm

So Russell, what's the final verdict on the plane crash? Or should I say, in the final analysis, as Shannon concluded; you put the plane in a mush stall situation within insufficient altitude and or power to recover.

I have read and reread your description and the part about being near power lines raised red flags to me and now that you have had some time to heal up and think about it, what are your thoughts on the incident.

My concern in regards to my own plans, focused mainly on increasing the power and leaving the rest of the plane alone. I haven't flown a plane without rudders. Now that I've read about your experience and others, it has me thinking that the modification to change to rudder pedals is probably a good idea.

As someone who has done just about every risky thing in a ultralight that you can do I certainly am not criticizing anybody else's flying. But I know from experience the sooner I get to 2000 feet above ground level the sooner I can relax a little bit and know that I have a little bit of breathing room or should I say a little space to make an error and be forgiven.

Anyway, I'm glad you're all right and looking at putting your plane back in the air.
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Postby russell » Mon Oct 02, 2006 10:47 am

Well, after a lot of racking my brain and talking it over with my friend who was on the ground looking on, we came up with the probable cause. I remember in the past just how easy the plane was to fly even through the summer months and on very breezy days. I had forgotten; however, that I had sat out days waiting for the wind to die down where I could fly, but sometimes it never did. Another contibuting factor was the fact that it has been 18 years since I had flown it and I felt assured that I could just take up where I left off. Wrong!
I took off fine and made several circular laps around the area of the strip and realized it was too windy for me to enjoy the flight. I was constantly making control corrections so I decided to land. The reason I was so low at the time was because I was attempting to land. As I would get within about 30 feet of the ground the plane would get very difficult to hold steady without dipping and rising quickly so I would pull up to try another pass. I did this three times then turned to try in the opposite direction and thats when things got hairy. As I was coming out of the turn towards the strip I obviously turned in the direction of the wind (at that time) and at my slower speed combined with the high temperature, the low power of the Pioneers just couldn't compensate and I started to sink. Trying to nose down slightly to possibly gain a little speed put me close to the power lines. I was forced to bank away even thou I knew I was going to strick the ground with the right wing (my direction of bank) and sure enough it did. It pivoted 180 degrees on that wing tip as the other wing kept flying around and as soon as it quit it tipped that way and the landing gear made sideways contact (to the left) with the ground. The main wheel on the left side and the nose wheel took the brunt of the force. The right wheel was untouched. I shut down the engines and climbed out with only a small bruse on my left thigh.
The conclusion.....Stupid pilot with broken plane!
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Postby JPXman » Mon Oct 02, 2006 1:57 pm

ah yes, this is what i call "induced wind shear"

if it was windy, say 10mph lets examine the situation. you are flying into wind at 25mph indicated and decide to turn around. the lazair can turn around fairly quickly. the quicker it turns though the more trouble you create for yourself.

you are basically going from 0mph of wind relative to the wings flying upwind, to a 10mph tailwind if you turn fast enough. the 0mph comes from the fact that you are flying in equilibrium upwind, lift equals weight, and thrust equals drag - everything is balanced - so if you were a piece of dirt on the wing, all you would feel is 25mph of wind, just like the ASI would read.

now you turn around. the ASI will drop to 15mph (worst case, as you turn you will carry some momentum and it'll probably drop to 18mph). this is wind shear. the relative wind has changed direction over the wing, and thus speed as well. there is still 25mph of wind going over the wing, just that its coming at an angle proportional to your turn away from the headwind. as you turn 180 degrees, it acts as a tailwind and you will lose that 10mph while your plane struggles to get back to flying speed (if serious enough, by entering a stalled condition).

this change in relative wind, coupled with the fact that load factor increases in a turn, and stall speed increases as the square root of the load factor, your 17mph stall speed in a lazair will come close to 20mph in a 30 degree turn.

so now you only have maybe 18mph of wind over the wings and a stall speed of 20mph, a recipe for a stall.

solution? in windy days, when turning downwind, always pick up the speed. this is true in the circuit especially from the turn from takeoff to crosswind, and from crosswind to downwind.

Tyler

PS: if anyone wants to convert a series I to rudder pedals, i have the controls off my series III "down stick" packed away in a shipping tube ready to ship to someone. just pay the shipping and you can copy the design and send the parts back to me. I did this for a fellow lazairhead recently and it worked well.
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Postby yankeflyer » Mon Oct 02, 2006 2:08 pm

anyone ? ah Tyler I think that would be me-

guess-ta-mate constrution time-

I hope I have the time and where with all

B)

Miles
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Postby russell » Mon Oct 02, 2006 2:58 pm

Yeah Tyler, that pretty much fits the situation I was in. In the past I have done a power-on stall intentionally and with my weight on a mild day the nose fell off at 10 mph. The only time I became frightened during this air show I was putting on was when I couldn't get the nose down and the ASI was showing 15 mph. Luckily it held that 15.

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Postby JPXman » Tue Oct 03, 2006 10:10 am

email me offline and i'll ship the stuff out. i'm out of town until the 17th now, going to ontario for a visit. karl i've got your number i think, if i'm going to get around montreal lets get a beer.

Tyler
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Postby flyalaz » Tue Oct 03, 2006 10:51 pm

Hi Tyler,

Sure thing! A couple of wobbly pops would go down well! If you make it to Montreal great. If not, maybe some middle ground in between. Maybe even brainstorm a little and come up with some new indespensible gadget that everyone must have! Perhaps gather some of the other local Lazair types and have a little reunion.

Cheers,
Karl
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Postby JPXman » Tue Oct 17, 2006 6:14 pm

karl!

so sorry to leave you hanging! i lost my cell phone at the bar on friday night and i didn't have your number when i woke up in the morning... there's always something that gets messed up when i visit ontario. i apologize big time, and promise that next time i'll buy the rounds.

just back in edmonton now catching up on the computer.

Tyler
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Postby flyalaz » Tue Oct 17, 2006 8:29 pm

Hi Tyler,

I thought to myself, what could possibly happen at a wedding bash, and that was the first thing that popped into my mind. Hope no one called China on your dime!
Such is life. Well, you know, there's always the next time!

Cheers,
Karl
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Postby russell » Thu Oct 19, 2006 11:24 am

Shannon,

About the D-cell skin overlay that you posted a photo of recently, can you go into detail about the process? Such as, did you pre-shape the "D" into the overlay skin before attaching? You must have used a hole duplicator to match holes, so what brand did you use and how well do they work in general? Pardon the "duh" questions, but I'm like that when in unfamiliar territory. If you prefer to discuss off group I'm at russell@brownautomatic.com.

Would appreciate any heads-up you can give,
Russell
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