Using a hangar winch with a DA40

Any DA40 related topics

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Lance Murray
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Re: Using a hangar winch with a DA40

Post by Lance Murray »

I don’t have my AMM handy but in the lifting and shoring section I thought the front of the airplane is supposed to be supported. I don’t remember seeing a tail tie down method in the manual.
Steve wrote: Tue Dec 03, 2019 5:16 pm
Rich wrote: Tue Dec 03, 2019 4:28 pm Consider also the stress you occasionally put on the tail tie down when the plane is put on jacks, necessitating installation of a tail-stand. A different kind of stress, of course, but considerable.
Considering the lever arms involved, you would have at least 300 pounds of vertical force on the tail skid when you pull the engine (below):
IMG_3040.jpg

Different vector than the tow cable situation, but as Rich states, considerable...
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Re: Using a hangar winch with a DA40

Post by Lance Murray »

Maybe a bit Steve. For me what comes to mind however are crashes like this one:

https://en.wikipedia.org/wiki/American_ ... Flight_191

Just to summarize the accident American Airlines used an unapproved procedure for hoisting and mounting the engine which caused fatigue cracking and eventually causing the engine mount to fail.

Steve wrote: Tue Dec 03, 2019 3:17 pm Lance, don't you think that's a bit histrionic? Winching the airplane slowly on the ground is not going to subject the airframe to anywhere near flight loads. None of the future owners or occupants of your airplane will have any idea of what you subjected the airframe to in the air either. Ever exceed Vno and get some unanticipated turbulence? I sure have.

I'm not advocating doing crazy, stupid stuff with the airplane, just using common sense. If you are concerned about loads on the tail fin when winching by it, calculating them is doable (even for folks like me who are 4+ decades distant from my E Mech and physics courses). Having said that, I use a PowerTow on my airplane, because I have a 44 foot wide hangar opening. If it were tighter, I would likely have constructed some kind of winch along the lines of others on this thread. Their likelihood of damaging the airplane is probably much higher from a wingtip strike trying to back it in using a towbar arrangement than pulling on the tail...

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Re: Using a hangar winch with a DA40

Post by MarkA »

Lance, I think you are missing the original point of this thread.

Historically there has been a lot of discussions and questions about attaching a winch to the tail strake and pulling a DA40 into a hangar. The point of this post is that it's relatively easy to create a harness that allows the hangar winch to be attached to the landing gear instead of the tail strake. When a harness is used as described, the landing gear experiences a rearward force of around 50 pounds (or less) in more or less exactly the same direction and at the same point it experiences on each normal landing when the brakes are applied. Obviously, the brakes generate a lot more rearward force than 50 lbs during a normal landing.

The objective of this post was to share a reasonably easy way for a single person to safely move a plane in and out of a hangar. There is no question that a power tow can be used to both pull the plane out as well as push it back into a hangar. Alternatively, the tow bar can be used to pull the plane out without too much effort and a floor winch can be used to pull it back in without risking damage to the plane if it is attached to the landing gear rather than the tail strake.

The winch approach is also lower cost (around $450 for a standard aircraft winch from Aircraft Spruce or less if from Harbor Freight) and from my experience, is a bit easier to use than a power tow when guiding a DA40 into a 40 ft hanger where you only have 3" or so of clearance on each side.
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Re: Using a hangar winch with a DA40

Post by Rich »

Lance Murray wrote: Wed Dec 04, 2019 6:55 pm I don’t have my AMM handy but in the lifting and shoring section I thought the front of the airplane is supposed to be supported. I don’t remember seeing a tail tie down method in the manual.
Steve wrote: Tue Dec 03, 2019 5:16 pm
Rich wrote: Tue Dec 03, 2019 4:28 pm Consider also the stress you occasionally put on the tail tie down when the plane is put on jacks, necessitating installation of a tail-stand. A different kind of stress, of course, but considerable.
Considering the lever arms involved, you would have at least 300 pounds of vertical force on the tail skid when you pull the engine (below):
IMG_3040.jpg

Different vector than the tow cable situation, but as Rich states, considerable...
When lifting the airplane on the jackpoints, the tail must be held UP, or it will rotate all the way to the ground. I use a jackstand with no weights at all, since all force is downward. The nosewheel lifts up. If I'm doing something more exciting with the polane whild on the jacks and removing the nosewheel, then I'd probably brace the front end somehow. The business of supporting the nosewheel is a precaution when removing it for whatever reason. I've never boithered with this. BTW, the documented way if all you want to do is lift the nosewheel (such as checking the pivot or the rotation tension) is not to pull it down by the tail tiedown, but to attach a ratcheting strap to weights an wrap it over the fuselage just forward of the vertical stabilizer and pull it down there. See section 32-20 of the AMM.
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Re: Using a hangar winch with a DA40

Post by Lance Murray »

Yes I was only responding about pulling the tail with a winch. The LDG gear strap I suppose would be ok. Braking forces would seem to be stronger than those imposed with the winch.
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Re: Using a hangar winch with a DA40

Post by Rich »

To elaborate more on my thread drift about the use of jacks, the manual shows support at the tail, the nose and the wingtip tiedowns. I could see doing this if you're lifting it up outdoors but I've never seen it done.

I ran some calculations to see what the tail tiedown downforce actually is when the plane is on the jacks. For mine, with half tanks, the tailstand needs to support something like 19 lbs. For a more representative DA40 than my very light/forward CG example, I came up with about 39 lbs. At MTOW and most aft CG (102 in.) it comes out to about 110 lbs.

As a side note, my tailstand has an inconvenient max height, so I have to lift the tail (normally 25-26 in. clearance) by about 6 inches to attach it. I have to exert somewhat more than this 19 lbs. because I'm fighting the nosegear suspension in this case. I'm in the process of building a custom tail stand and needed to have a better idea how much load it will have to handle. Now I know.

Another side note: after raising the plane on the jacks the mains swing inward by quite a bit - easily a tire-width on each side. So when I lower the plane back down it sits much higher on the mains and the jackstand then hangs in the air from the tail tiedown. :scratch: It's not particularly heavy, but something to keep in mind when building a replacement.
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Re: Using a hangar winch with a DA40

Post by pietromarx »

I am curious on the other side of all of this - whether people have seen tail damage due to the winch, using the tow kits, hitting the tail on landings, etc.

Has anyone ever seen any tail damage on a DA-40 outside of a crash? Examples: the tail skid ripped off (not scraped, but actually torn out of its mounts), cracks in the empennage, etc. Anyone ever have to make a repair to the composite structure of the empennage?

Not that one can prove anything using a lack of data, but I haven't heard of anything happening despite airplanes being dragged around by the tail, dragging (towing) other airplanes by its tail, being tied down to stakes on the ground during high winds, flying through turbulence, etc.

Also ... don't forget ... the DA-40s have a towing kit available. Having flown a lot of gliders, I can safely say that the strain of a 1200 pound glider being towed through turbulence is higher than any slow winching into a hanger. For glider tows there is a length of rope (the "weak link") used which is designed to break between 90% and TWICE the weight of the glider ... even for light gliders this can be 1500 pounds or more.

Speaking of turbulence, the airplane structure is designed to take heavy loads at cross angles. I don't have the equation handy, but it is a substantial thing. And remember that the control surface deflection speeds, etc., are all based upon this. I don't see how a winch could ever replicate these kind of loads in any normal circumstance. Even where the co-pilot "caused" the breaking as in the awful AA 587 flight where the tail broke off, it happened at a load of 1.5MN. Not that a slow winch across a flat surface is like an airliner going through wake turbulence, but it is an indicator of what it would take to break.
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Re: Using a hangar winch with a DA40

Post by Lance Murray »

I recall seeing a wrecked DA40 with the standard tail empennage snapped off mid-way. I contacted the owner about salvage and they responded that they planned to repair the airplane. I never heard if they were successful. I suppose since it is CF and Fiberglass it could technically be repaired but I would guess the factory would refuse to support the repair. I can imagine the repair added some pretty significant weight.
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Re: Using a hangar winch with a DA40

Post by Lance Murray »

The glider towing kit is a good point. Has anyone ever seen one? How is it connected to the airplane?
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Re: Using a hangar winch with a DA40

Post by Rick »

:shock: So here is proof that it IS possible to apply enough force to damage the tail!
DA40_Tail_Strike_1.jpg
Or maybe this counts as a "tail strike"??? :D
DA40_Tail_Strike_2.jpg
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