Official Freewing Twin 70mm AL37 Airliner Thread

[GliderGuy]

Thought you might be interested in reading about some of the REAL WORLD reliability aspects of an AL37 with lots of flights on it. I have flexible work hours, to some degree, so when the weather is nice (which it often is), I am able to take advantage of it. Here's the scoop...

• Pre-ordered and got the bird in late December 2019, and was up and flying within a few days
• Averaging about 200 flights per month. This is not intended to be a brag, but to let you know that 1,200+ flights are on the bird
  • I am able to leave it assembled...transport it in the bed of my pick-up...not connecting/disconnecting things every trip to the field
• Summary of failures follow. Pretty amazing performance, I'd say!
  • one engine bearing began screeching loudly after about 400 flights. This must have been a fluke because the other engine has performed flawlessly since day one
  • two main gear servos have been replaced over 6 months and at least 2400 gear cycles
    • Hint: Land gear up when one fails in the gear-up position. I learned the hard way that attempting to land with the nose wheel and one main down is a disaster waiting to happen.
      • The nacelle on the gear-up side hooked into the turf and the turf tore it off. Took some carbon fiber work to fix it, but I did fix it...rather than order a new nacelle
        • Suggesting landing gear up on a hard surface...not turf. Shaves off some foam, but at least you won't tear off a nacelle
  • Nose gear mounting box came loose and also the nose gear steering servo came loose (two different flights..not on the same flight) Fixed both of these issues with epoxy
  • Winglet pin broke on one winglet...replaced the piece of plastic into which the hold-down pins are molded as part of
  • Replaced the nose wheel tires twice, but the rubber on the mains has held up nicely. I fly off concrete exclusively except when I decided a grass turf landing might be best when the main didn't extend.
    • I am about to change the main's rubber, soon.

That's it. Again...pretty amazing reliability. None of the control servo motors has began to chatter and no control servo failures have been experienced. The top of the wing foam has a few slight wrinkles/creases from the spins, loops, snap rolls and pull-ups to vertical climbs i do at times. All around...a well designed aircraft and well worth the money!
-GG.

[The Sheriff]

Averaging about 200 flights per month. This is not intended to be a brag, but to let you know that 1,200+ flights are on the bird

Nice informative post. I wish I could fly mine that much. If my math is right, that is about 10 flights per day, 5 days per week. At 1200 flights averaging 5 minutes per flight with an average speed of 60 miles per hour you would have 100 flight hours totaling 6000 miles in distance. Enough to fly from New York to Ecuador and back with reserve for an alternate airport.

I haven't flown mine nearly as much, not even close, but also can attest to the durability of the plane. She's a beast.

[walkerm45]

Here are a few pics of my project to create The 'Spirit of Arizona'. My son has flown Kc-135R's for 20 years. I built this plane for him......

[AceMigKiller]

That's really cool man!
I grew up in Arizona and saw the Copperheads flying around all the time.
Now, as an Airline Pilot, it's neat to drop in to Sky Harbor and see that Arizona tail hanging around the flight line. Nice work!

[Alpha]

I agree with AceMigKiller what an impressive KC-135R conversion. I designed this darn AL37 and still can't figure out how you and Solt and the others are bolting on an extra pair of go-pods to my bird without folding the wings! But I love seeing the results and am not a small bit envious.

Your son flew them, and Boomer (another member here) was a boomer on them. I remember walking the flight line gawking at the 203rd's birds at Hickam. Small world!

[Slowflight]

Alpha I have to say this conversions are most impressive and give testament of a great original design , I too thought the extra turbines would weakened the wing. Perhaps this fellows can post step by step details of their modifications, actually I think it deserves and entire new thread.Amazing work guys.!!!!!!!!

[walkerm45]

I think that the channel that was created for wiring was large enough to accept an extra set of wires, this was the key, as the engineering performed by Freewing allowed the airframe to carry the extra weight. The rest was lining up the geometry, and removing the foam, with emphasis on minimum removal. As you might note, the 4 motor airframe is a lot faster.....The 2 extra motors are covering the weight of the wire, battery, and esc only, but a big OUCH on wing loading.

I wish more thought would have gone into the landing gear, but that's another topic .......Mike

[James]

Very impressive walkerm45! I like that livery a lot with the tail graphic. Spices up an otherwise "boring" (for lack of a better term) big gray plane. With the endless liveries that can be done on this aircraft, While its awesome to see the KC-135's and Poseidons etc, I love a little color on this big bird and this is a great mix. Well done

[Spinny Testaverde]

Nice informative post. I wish I could fly mine that much. If my math is right, that is about 10 flights per day, 5 days per week. At 1200 flights averaging 5 minutes per flight with an average speed of 60 miles per hour you would have 100 flight hours totaling 6000 miles in distance. Enough to fly from New York to Ecuador and back with reserve for an alternate airport.

I haven't flown mine nearly as much, not even close, but also can attest to the durability of the plane. She's a beast.

😮

[GliderGuy]

I wanted to add something to my July 6th post regarding the reliability of the AL37...

The nose gear can, though rarely, throw runway FOD into the turbine blades. In the 1200+ hours of flying, I have found on 2 occasions very minor nicks in one fan blade on each of the left motor fan and right motor fan. Since nicks act as stress concentration areas, the potential for blade separation at high RPMs is a concern. In both cases, the nick on the leading edge of the blade was very small...in the range of 0.5 mm across.

I decided to try a field repair, so I used a UV-cured glue (Bondic liquid plastic UV welding tool) to fill each tiny nick when I discovered it. Be careful to place only a small amount of the glue onto the nick...and thoroughly cure the glue with the UV source. I then used a fine grade sand paper glued to a Popsicle stick to reach in and smooth the cured glue and conform the shape of the cured glue to the surrounding blade...while being careful not to misshape the blade. A fine sandpaper (600 to 800 grit) is best suited for this process and does minimal scratching of the surrounding blade surface.

The end result was hard to see and impossible to feel, and the stress concentration area is no longer evident. This makes a proven field repair, gets you back into the air quickly, and allows you to continue to fly while you wait for your replacement fan blade to arrive in the mail.

-GG

[Bajora]

A few photos of a clubmate's (Michael Troy) AL37. He maidened it today and proceeded to log at least five beautiful flights with nary a click of trim or any issues encountered. I shot a bunch of media and hope to have a video edited down too ... soon. This is the first AL37 I have laid eyes upon and is every bit as impressive as I had expected it to be. It was the talk and focus of the field today!

[Bajora]

And a short video of today's flights.

[Hugh Wiedman]

Bajora outstanding video, loved the different angles. Excellent flight and the Alaska version is beautiful. You should be very proud of it!

[Skittercat]

A big thank you to Jon Barnes for spending a good part of his day taking photos, video and editing.

Maiden flights always produce some nervousness especially when I have put in several weeks of work on a custom paint job. I had extra confidence this time however given all the reports I read here about the plane.

I struggled with the peeling paint. When I try to feather the peeled areas around the bare foam it would just keep peeling. Sanding the mold dimples made it even more difficult. I was worried that the peeled areas would show through on the final paint job. I finally got to a place where I could do a base covering with finishing epoxy which held down the original paint. Next I applied three coasts automotive primer, sanded and painted the base white with Rustoleum and air brushed the blue and grey and Callie Graphics for the decals.

Besides the paint the only other problem I had was figuring out the delay in the gear retract. When the gear didn't work immediately I assumed something was wrong and bypassed the blue box and they worked. Derek at MRC suggested I wait five seconds to see if they worked and they did.The blue box was not the problem, it was me being too impatient to wait the five seconds for the gear to retract. Thanks Derek.

[James]

Awesome pics Bajora as always! And great customizing and flying Skittercat! Welcome to Hobby Squawk as well, that's a heck of an entrance

[Aros]

Amazing shots as always Jon! What a beauty, and great job on the maiden and welcome Skittercat!

[CurtS]

I signed up just because of this plane. Was led here by RamyRc. (Wish I had the time to do what he does) Only on page 65 now. My take aways from this thread:

- I am baffled by this plane, its only downfalls I see are maybe needing the front wheel area 3d printed brace and the white paint is touchy.

- This level of people NOT complaining is unheard of.

- I haven't even seen on person complaining about an unbalanced fan or terrible gear design. When does this ever happen?

- I am ordering one later this week before they become MIA again.

- After 12 years on rcg and fg this forum is a breath of fresh air. Its been years since I could actually enjoy or even entertain the idea of reading 80 some pages over the course of a week.

Now if I can ever find out how the two guys mounted the two outboard fans. Seems they are tight lipped. :)

[xviper]

CurtS I think the bit about the nose retract brace can be struck off the list of complaints. It's a BIG maybe. Those who seem to break the nose retract for lack of a brace are going to need one for almost any plane. I made one for a jet that was when jets were still new to me and landing them was still a learning process. I broke that retract even WITH the brace. It just broke it worse than had the brace not been there. I've learned to land better now and very rarely have nose retract breakage. I've also learned that you don't really even have to try hard to break a retract. I have since NOT incorporated a brace of any sort on any nose retract. I just don't drive (land) the thing into the grass or the rough parts of the field. Very few retracts will tolerate that very well, brace or no brace. You can land ON grass, just don't land on the smooth runway and then run it hard INTO the grass.
This AL37, at least for me, has been "bulletproof". Yes, the paint has a lot to be desired but for those who don't feel the need to mess with it and just simply apply decals and put a clear coat on it, it's NOT a problem at all. If you're into some heavy painting anyway, the stock peeling paint can be easily covered over with new paint or just peel it all off with tape.
As for the two guys who mounted the outboard fans, I don't think there's any "magic" to either one nor do I think there was any "secret" to them (referring to the "tight lipped" part). It's not difficult to imagine what or how it was done. As I recall, the first one that was posted about, I believe the two outboard engines were "dummies" and had no EDFs in them. They appeared to be mounted via a home made balsa plywood structure built into the wing, using empty engine pods bought from the parts bin. That one may have later gone on to have actual EDFs in them. The mounting structure was adequate enough to hold the "real thing". I think it was likely that the structure was similar to how the stock mounts were.

[mshagg]

I designed the AL37 nose wheel brace on thingiverse and will happily tell you it is absolutely 100% not needed. It was pretty much an exercise in seeing if I could design something that worked. If it gives guys some piece of mind that's great, but if you're coming in hard enough to bust the stock setup you're having a pretty off day.

The landing gear on this thing are tank-spec. It's the best grass ops jet in the Freewing catalogue IMO (yes even better than the avanti). Takes off of long, wet grass at 2/3 power and you can set it down like a baby even if it is coming in a little hot. It doesnt bounce, it doesnt tip over, it rumbles over grass as if it's pavement, doesnt have cheater holes to suck lawn clippings into.

[CurtS]

Now that I finally finished every page I can completely agree the nose strut brace isn't needed. Thank you both for your detailed insights.

My own personal thing that I will change is the wheels. I hate that grinding noise. Its like nails on a chalkboard. So aluminum ones it will be with the two main inners being JP Brakes. Either 65mm or 70mm depending on the clearance.

Seeing how this has plenty of power for short take offs, brakes add more places to safely fly at. If I could put brakes on my 40% I would.