PDA

View Full Version : Glider tow hook



Bill Rusk
07-07-2006, 11:13 PM
Gents

I am going to put a glider tow hook on my EXPERIMENTAL Smith Cub. I was thinking of connecting the tow cable to the flap cable after it goes around the bottom pulley in a Y type configuration. This would put the tow release on the flap handle so that when you pulled flaps you would also release the hook.

Thoughts

1 - I will always be towing at fairly slow speeds, less than 60 mph so yanking the flaps should not be a problem.

2 - If the whole thing failed it is not a primary flight control, (the flaps fail up) so worst case would be a no flap landing.

3 - simplifies controls, installation, cockpit clutter and weight.

4 - It would be set so that you could tow with 1 notch of flaps and the release would not activate until more than 1 notch of flap were pulled.


O.K. My flame suit is on so tell me all the bad things about this that I am overlooking. Remember....this is an Experimental airplane, so I can experiment and try new ideas. I just would like to use all the knowledge available before I try a DUMB idea.

Thanks

Bill

Chuck-Fairfax
07-08-2006, 12:00 AM
Alls I know is that when I was towing gliders in a Super Cub, the ability to bring your foot back and hit that red ball was great peace of mind. I would not want to have to use a hand motion if the engine quit and I was trying to restart but had to cut the glider loose. Same if the glider got too high and raises your tail so you can't climb. You gotta dump that guy quick, maintain speed and hope you can fly it out. You don't want flaps.

I saw it happen with a guy towing with a Stinson L-5, and a split second makes the difference. His engine blew right after take-off. He cut the glider loose, which sling-shotted right over the L-5, and he got the L-5 stopped on the runway. The glider landing was a little bumpy on the prarie overrun. Never lost an engine towing myself, but did get out of position to the side with a student glider pilot and the load broke the weak link at fairly low altitude. The short cross-wind runway at that airport saved my bacon more than once. The other time was a take-off in a T-34, where a valve stem broke right after takeoff, and power was barely enough to stay airborn. No way to get back to take-off runway either time, but the cross wind worked.
Anyway, Experimental lets you try different things, but I have reservations about this one. Just my $.02.
Chuck

Bill Rusk
07-08-2006, 12:11 AM
Chuck

Thank you for your input. I have towed and am familiar with the perils associated with kiting etc. Are you saying that the SC you flew had a foot release for the tow hook? Never heard of that. Hmmm.... something to think about......

Bill

Chuck-Fairfax
07-08-2006, 07:41 AM
Bill,
Best I can recall it was a red ball under the left forward edge of the seat. I may be wrong, but I am sure it was foot operated. Where I worked they did some things probably not too popular now, like on pattern tows landing down the runway with the cable still attached, and the glider landing behind you so they could hook right up and get another tow right away. If you couldn't slip the SC to land ahead of the glider on a pattern tow, you were considered to be a poor tow pilot. Never got a cable wrapped around electrical wires, but one of our guys did. I think he released before the weak link broke. Anyway, did not break the electrical wires. We had a winch tow also, and that was a real kick, literaly (sp?). If you didn't release the hook at just the right point in the arc, it put a tremendous pull on the bottom of the glider and when you released, the keel snapped upwards violently and all the dirt and junk in the bottom of the glider was blasted up against the top of the canopy, and up your nose! I never liked glider instruction. Soaring is fun, and I liked towing. A glider operation works out of Front Royal Virginia, where my J-3 is now, but I have not got involved in gliders again.
Chuck

FiftyNineSC
07-08-2006, 10:21 AM
Like said above, I'd just be worried about having to extend flaps when a novice glider pilot is trying to pull my tail down.

If you end up putting it on the flap handle, I would just use a "self imposed" forward stick limit while towing. Especially close to the ground. In the Ag wagon if I'm anywhere near the forward or rear stop on the stick; I'm cutting them loose. Not the time I'd want to be putting in two notches of flaps.

Bill

PA-12 Lover
07-08-2006, 11:47 PM
If you are serious about installing a tow release, you should seriously consider the "Tost" release. The design is far superior to the traditional Schweizer type release in that the effort required to release does not increase with pressure on the release. The old style release becomes more difficult to released when it is under pressure, which is exactly when you most want to get rid of the glider. The Tost release was available from Tim Mara at wingsandwheels.com. We have been using one for many years and several thousand tows on my PA-25/260 and would not tow with any other tow hitch.

The Bijou Boys
07-09-2006, 09:32 PM
Bill,
I'm still towing full time at the Air Force Academy so have some "recent" experience to share. We converted to the Tost releases on our Cub Crafter 180s to avoid the inability to release when the glider goes high on you. The release is a T handle mounted on the panel. I have the Schweizer type release on my Super Cub with a floor mounted release handle.
My suggestion would be to "simplify" the installation in your Smith Cub by making it separate from the flaps. I just see too many problems with dual controls in trying to combine an aerodynamic control with a safety control.
I don't think you'll save much weight by connecting the tow release cable to the flap control.
I would install a panel mounted T handle instead of the floor mounted release like I have. With my shoulder harness tight, I have trouble reaching the floor mounted release in my cub but no problem at all with the panel mounted T handle in the CC Cubs at work.
As far as the Tost - Schweizer release trade. If you know who you're towing and can depend on them to not get high on you (no students) the Schweizer release will work fine. Works great for me. Since you're putting it in an experimental I can get you a used Schweizer cheap since you won't need paper work. PM me if you need one.
Tom

cubscout
07-10-2006, 11:22 AM
Bill, excellent advice from Tom. The AFA tow operation probably has more experience with this stuff than any other in the country, with a strong emphasis on safety. I agree with all Tom's (and PA12lover2) comments, for the same reasons.

What Chuck describes sounds like the standard Schweizer floor-mounted release handle. Yes, you could move your foot off the rudder and whack it with your heel, but if the glider is kiting, it's doubtful you could get enough force to release. And of course reaching down at a critical time is a bad idea, too.

The T-handle which Tom describes is an excellent solution with a Tost release, but consider replacing the crummy bowden cable which they supply with something more substantial, like Harley Davidson clutch cable, which is avalable by the foot.

Since you're talking exp, forget the Tost factory bracket, and fabricate your own, along the lines of the Schweizer "crutch" to mount the Tost hook. Review the tow release chapter of 43.13 for criteria.

If you're seriously thinking Schweizer release, you need greater mechanical advantage than a T-handle. Dave Johnson's Supercubs mounted a bellcrank with something like 5:1 mechanical advantage, maybe more, to the lower instrument panel tube, next to the mixture, with 1/16"?? flexible cable, routed through pulleys. This puts the release by your throttle hand, which is easiest/safest to get to. I've got a picture somewhere, probably a daguerrotype..... Has anyone got a copy of a 337 for this installation?

Most of the Pawnees use the "Dump Bar" with the Tost, though I've flown one on the "money bar," again close to the throttle quadrant.

At this time, Schweizer release mechanisms are no longer available from Schweizer, and I believe Aviat installed their last new one on a Husky last year, so it's used market only now.

A word of caution, a friend near Tom was planning to put a towhook on an experimental Skybolt, and was told that it isn't legal to tow with experimental, But that's Denver FAA for you. On the other hand, a tow release is a real handy way to secure your 'Cub for hand-propping....

Bill, good luck, and keep us posted on your excellent project.

Thanks. cubscout

Bill Rusk
07-10-2006, 09:36 PM
Excellent thoughts all. I might have to check on the "no tow" restriction. That would su.... uhh...be a bummer.

Bill

StalledOut
07-10-2006, 09:57 PM
According to EAA, experimentals are not to tow gliders or banners.
One of the restrictions.

tp
07-10-2006, 10:32 PM
:oops:

cubscout
07-10-2006, 11:12 PM
tp, are the local glider tugs EXPERIMENTAL or are they RESTRICTED? Many/most Pawnees are restricted, but few experimental; and some 150/150's I've seen are also Restricted category.

Not the same animal as Experimental, but some regional FAA offices seem to be confused about the distinction these days, despite an encyclical specifically permitting glider tows with Restricted category.....

Thanks. cubscout

Dennis Blankenbaker
07-11-2006, 02:38 AM
I flew a Scout with a release cable running under the seat in a condituit, one of the Adel clamps broke letting the cable move around some. No problem until I had an observer in the rear seat and he managed to push the cable far enough with his foot to release the glider unexpetedly. :agrue: The glider pilot was unhappy and we had to make up a new rope. :bad-words:
I normally landed with the rope in tow, land short, turn around, and hook up for the next one

leon tallman
07-11-2006, 04:46 AM
Bill I got one if your interested

Bill Rusk
07-11-2006, 12:07 PM
Leon
I think I have one lined up, but Thank You for the offer.

I will do some research on this possible restriction. If you read the list of experimental restrictions it also list day VFR only. Surely the guy with the Lancair 4P is not restricted to day VFR only? Plus what about no fly over congested areas? Guys are flying and filing IFR in experimentals, right? Straighten me out folks. I just looked at all these panels in homebuilts and assumed they were flying IFR. ( I'm feeling pretty dumb right about now.) I guess I thought that was a list of possible restrictions and that the inspector used it as required. I guess I need to get this figured out before I add the weight of a hook I can't use.

Sincerely....Thanks for the heads up folks.

Bill

supercubc37
07-11-2006, 01:45 PM
Bill the restriction will likely be in your operating limitations for your aircraft. The last one we did (Cubpylut's Murphy Rebel March 2005) had the restriction in the operating limitations No towing banners/gliders. Now depending on your FSDO you might be able to get the restriction on the glider tow lifted for towing a glider that you owned only, at least that is the way I would approach it. If they give the OK to tow your own glider they will probably want to see the same testing that would meet AC43.13-2A Chapter 8, Section 1 and 2 and give you some additional Phase I flight testing to do.

Matt

tp
07-11-2006, 05:21 PM
Cubscout I may have been hasty in what I have stated. :oops: I will make a trip out to the airport tomorrow an report back.

cubscout
07-11-2006, 06:01 PM
tp, hope you didn't interpret my question as a flame; just seeking clarification. YaHOOOO! a LeGITimate excuse to to to the aerodrome :lol:Umm, I think I need to check out something at my home aerodrome now....

Thanks. cubscout

tp
07-13-2006, 10:02 PM
Didn't make it out to the airport yesterday humidity and heat got to me. Got out there today an did alittle quality bumming. Man do I have egg all over my face. :oops: ( would have used the tomato but am have trouble with the smiles) Before clutching mouth make sure brain is in gear. The pawnee is indeed restricted and worst yet the C-150 is in Normal category. :oops: :oops: IN GEAR ANY GEAR!!!! The fellow was looking for info not misinformation cubscout I need to go delete a reply.

Chuck-Fairfax
07-21-2006, 05:30 PM
Looked at the set-up on the Pawnee tow plane at Front Royal Airport, Virginia. They have a rope on a reel and reel it back in after the glider drops off. Emergency release: there is a cutting blade back near the end of the tube the tow rope comes out of, and if the tow plane is in trouble the pilot pulls a handle on the instrument panel and it activates this blade and cuts the rope. That is what they say. The "blade" is a shearing type thing with a lever action sort of like a tree-trimmer cutter. Does not look good to me, just my opinion.
Chuck Shaw

CptKelly
10-20-2011, 10:09 AM
It is my understanding that you CAN tow using an experimental cub, you just can't charge for it.

Mike

Bill Rusk
10-20-2011, 11:18 AM
Just a heads up on this. I pushed really hard (went way up the FAA chain of command)to be able to tow gliders and was told in no uncertain terms that it was not going to happen. Charging for it or not. Even if I was the owner of both the towplane (experimental cub) and the glider. An E-LSA can but not a regular experimental. Just to make sure things are really confusing. I also asked if it would be OK as long as I only towed experimental gliders. No to that as well. It is on the list of restrictions for experimental aircraft and for whatever dumb reason they will not waive that one, unlike most of the others.

Best of luck

Bill

So Mike, if you can get approval, great, but just a heads up.

tcraft128
10-20-2011, 12:42 PM
You might be able to switch it to Restricted for towing operations. just brainstorming.