Alert AirHogs Acro-Jet (bad review on 3 planes)

[msnyder]

Yep, sure looks the same. Boy, the Avanti's rear horizontal stabilizer is a lot smaller though.
And a bit less swept back. Hmmm, makes one think...

[crazyloadguy]

I fly all kinds of airplanes and I am very impressed with this acro jet. Without being rude, you people have to realize that you are not flying a aero ace anymore. This plane is fantastic if you fly it like a real RC plane. It turns in a way that closer emulates ailerons on a flat wing stunt plane hold it down in one derection and it will death spiral, but tap and then tap in the other derection and it will do a nice neat turn. I am very impressed with this plane. again not to be rude.

[msnyder]

Wow, I just tried pitching my horiz. stab down -- apparently I did it too much, because
even with no nose weights, it dived straight for the ground. So I readjusted it by about
half, and now it flies crazy fast! Too fast -- I can't do those lazy figure-eights in
the plaza between office buildings any more! But I'll bet it could stand up against a
10mph wind in this configuration!

I'll probably try to dial it back a bit more toward where it was originally -- what I want
is slow, sedate, stable level flight, with no porpoising (like the sport flyer).

[xlcrlee]

Then, msnyder, you should make the mods I posted earlier (heat-formed washout in front (Canard stab) and main wings, cambered rear horiz. stab, and LOTS of upthrust! [to pitch nose down]) >>


I experienced horribly uncontrollable ever-increasing stalls with my Fury (now sold in USA as AcroJet by Spin Master), greatly exascerbated by even a slight wind, and only stopped by sharply turning it or by the ground! This is a cool-looking plane (everyone seems to really like it, including me), but technically a very bad design. Decades ago NACA/NASA advised full-sized aircraft designers, that for any plane whose top speed was well below transsonic, NOT to use a swept-back horizontal stabilizer. Of course such a swept-back planform will stall BEFORE the main wing, ESPECIALLY if the main wing is not swept back. This is exactly what we don't want.

After analysis and some trial and error, I fixed the problem so that now the plane can still fly very slow, climbs even better, does not pitch up into the wind, is easily turned in a small radius, does not pitch up after leaving a tight turn, and is readily flyable by an experienced pilot in turbulent wind in a small corridor between buildings, even windy figure-eights! Here's what I did: using a hair dryer or over a toaster, bend about 7 degrees washout into both the forward stabilizers (commonly misnomered as "canards": they are technically "Canard stabilizers", the stabilizers for a Canard configuration) and the main wings, with the main wings being the more important to wash out! Try to bend the front tips of the main wings down rather than bending the tip trailing edges up. This will probably have to be done several times, as the EPP has a great memory; the surfaces must maintain the 7 degree washout when checked hours later; be sure to flatten and re-stick the decals, which also helps maintain the shape. Using the same technique, add a slight camber to the rear stabilizer, about a 1 mm or 1/16" rise about 30% back. This is a fancier way than just bending the rear down, since the latter decreases the incidence, whereas my change keeps the same effective incidence at low speed, allowing tight turns, but only at high speed lifts the tail and keeps the nose down in gusts and relative wind increases.

It is also very important to tilt the motors so that the thrustline is pointing slightly downward as it goes towards the rear. This upthrust means that the top tip of the prop is much more rearward than the bottom tip. Note that both the sticky glue-joints and the EPP wing/motor housing are flexible! The thrust will now increasingly pitch the nose more downward as you increase power, allowing MUCH better wind penetration. This REALLY works!

Note, the up-pitching momentary relative airspeed increase is explained by Einstein's General (not the Special) Theory of Relativity, which states that energy and momentum is not correlative in all frames of reference. That is, the plane is and it's momentum is attached to the Earth's mass, not the air or wind, and so it keeps its groundspeed momentarily until accelerated or deccelerated by its stabilization system to catch up to, or slow down to, its original stable airspeed. This same concept is why satellites are launched WITH the Earth's rotation (a satellite Physicist explained to me that there are two ways of looking at it, and one of them works!). Powerful airplanes with lots of drag and thrust restabilize so quickly so as not to notice this effect, but helicopters and small light underpowered models definitely show it (WWI biplane pilots called downwind turns the "death turn").

Several folks have written that THEIR Furys flew very well from the start. My understanding is that the vertical stab glue joint angle depends on the worker on the assembly line and may or may not be correct or optimal. And it may be very bad on some examples. I really like my Fury now (as does everyone else, but I have to explain it did not fly like that out of the box). Lee


UPDATE: This has worked on about 10 of these bought by the factory in China I've been working in for evaluation and some parts cannibalization!
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Last edited by xlcrlee : Jan 10, 2007 at 07:34 PM.

[Bobber Bob]

Hi Jim...

Boy, those photos sure made a lier out of me.!!! I had always believed that their canards had no movable surfaces on them.

Well, you live and learn.

One thing is still correct, I still can't spell it !!!!!!!!!

Another thing is for sure, it sure is beautiful in the air.

Thanks for the pictures, Jim.

Bob
. ComeUpHere

[Peregrinari]

Well, I have read all of these posts on this plane. I love mine. All I did was the simple mod on the the tail. (cut from a business card and taped into place, it is even adjustable) and it flies more like a real R/C plane than any of the other airhogs. In fact, I like it better than my Bipe and my Jet (both of which I still love). You really don't have to do all the silly stuff with a hair drier to make this plane work extremely well. We are not reinventing the wheel here. I notice alot of people on here do that regularly. See photo.

I forgot to mention. I was flying it today in 6+ MPH winds without too many problems. Alot of work and constant adjustment but it worked reasonably well. If you want a plane that you don't have to fly then get an R/C car.

Tom

[LittleG]

I flew my acro jet today and I tell you what it flew wonderfully... It's awesome... I think that secret is not to fly it when it is really windy.... I flew mine today in no wind... boy - i tell you this plane flew and performed very well. It was great... I never had so much fun flying it... This plane is very stable unlike the bipe - porpoise galore... I did tape a dime on the nose of the plane to prevent it from porpoising... I might try taping a business card on the tail as shown in the picture that Peregrinari provided. I did, however, cut the canards off, I thought it looks better without it. Without it, the plane still flies well.... I'm thinking about buying two more. I can't wait to fly it again tomorrow... LG

[Ibanezjimjim666]

Originally Posted by Peregrinari

Well....... If you want a plane that you don't have to fly then get an R/C car.

Tom

LOL

The AcroJet looks better than any car I have ever seen......
except for maybe a Lamborghini Diablo


Cheers! Jim

[nofuelheli]

BOught my AJ at target last week. First flight was like sea world. Shoved a pebble in the nose and that cured it. But after reading this post a repositioned my tail. Trial and error was leaving tail in loose and several short hops. (without pebble) I found the sweetspot and glued it up. Now it flys very well. Fast and quiet. Death spiral can still be achieved but you have to push it. The best looking out of the Aero Ace stable yet. I remember seeing concept pictures of it when I bought my first AA bipes. I am glad to see a company that knows how to get new ideas into the market quickly and with good quality.

NFH

[crazyloadguy]

I don't think that any of the air hogs planes porpose to much... call me crazy but on all my AA and my AJ I have found that yes the planes porpose on the highest throttle setting, but that is how they gain altatude when I go to a throttle setting that is lower like the very lowest it can be, they fly strait and level. Mabey mine are different but on a low throttle setting my unmodded AJ flew perfictally.

[LittleG]

Ibanez...

What kind of plane is that next to your AJ? It looks interesting... Home-made brew with Air Hogs guts... What did you make your wings out of? And, it looks like you have a little airfoil and dihedral in the wing too...How did you accomplish them? Just bought 10 sheets of 3mm foam from RC Foam, they only sell them in 10 sheets, so I have a lot of material to build with, i.e. wings and planes, like the Ultimate Micro (Biplane) - will be building this with Air Hogs guts. LG

[LittleG]

Went to Target yesterday and found the last Aero Ace (Bipe) and got another Acro Jet... Both will be back ups and will probably stay in the box until needed... LG

[Ibanezjimjim666]

Originally Posted by LittleG

Ibanez...

What kind of plane is that next to your AJ? It looks interesting... Home-made brew with Air Hogs guts... What did you make your wings out of? And, it looks like you have a little airfoil and dihedral in the wing too...How did you accomplish them?....... LG

Hey LG. The plane you asked about I have named "Super-Hawk". Believe it or not the wing was already shaped from an Angell 2ch (the little guy in the pic below) . I just cut a shape that I liked and there you have it. The airfoil and dihedral were already there. I put a 6-7 inch carbon fiber rod on the leading edge for lightweight strength. The fuse is two pieces of balsa about a 16th of an inch spaced enough to hold the Lipo and Rx. I cut a notch on the left fuse side that houses the on/off switch. There are small pieces of foam strategically placed in between the fuse halves for lightweight structural support (plus cushion for the Lipo ).



I used CA (foam safe) to glue the fuse to the wing.
I added a 3" piece of 3/32" carbon fiber rod and a hacked AeroAce stab.
Add the guts and we have a sweet looking, sweet flying plane. The wings are about 2 1/2 mm thick so I cut out slots just wide enough to slide the motor pods in. See pic below \/


oops. Dyslexic Invasion Stripes ....

Here ya go

Looks really awesome in the sky!
Here's a close-up


Cheers! Jim

[MumblinBerk]

Flight Report on the Acro-Jet:

Maidened yesterday in light breeze. Light enough to fly the Bipe with confidence. Was surprised at the amount of porposing the Acro had. Worse than the Bipe. Now, I kind of like that with the little bi-plane. Makes it look like a demented butterfly on acid. Part of it's charm. But on the Acro-Jet, it was just annoying. Had to fight for control the whole time. Mind you, it wasn't "difficult" to fly, just annoying.

Looking at the plane, the angle of the horizontal stab is very high in the back, pushing the tail down, keeping it in high alpha all the time. Add power, or fly in wind, and it just noses up badly.

The CG looks dead-on to me, resting right at the center of lift on the wing. Adding weight to the nose would help, but to me, it would just add unnecessary weight, and increase drag from the tail by forcing it through the air at a bad angle.

Taking advice of others here, I reduced the angle of the horizontal stab. I did this by cutting a wedge of foam out of the vertical part using sissors, and glued it back together, thus lowering the back end, and bringing the horizontal stab parallel with the wings.

Back at the field, this proved to be TOO much modification. Without the stab pushing the tail down, you can not gain altitude since there is no elevator. I thought that might happen, and was prepared. I just bent the trailing edge tips of the horz. stab up a little. The depron holds the bends well, and needs no reinforcement to hold the new shape.

This fixed the high-alpha problems. A little less bend and it penetrates well, but climbs slower. I picked a happy medium, and was rewarded with WONDERFUL flights. Can now fly the whole charge out at lowest throttle for even flight, add any power and it climbs without porposing. As an added benefit, flight times increase quite a bit, and the glide was much improved as well.

Remaining issues: while it really doesn't "death spiral" unless you work at it, the Acro still drops altitude in sharp turns. (gentle turns do not). I don't think that can be fixed with out some relatively major wing modification.

Bottom Line: This plane is absolutely a great flyer, and beautiful in the sky, though I think AirHogs should address that tail angle at the factory so as not to disappoints those who wouldn't know how to alter the plane.

-MB

[msnyder]

Nice simple presentation of the stab mod.

Drops altitude in sharp turns

Tip stall? Vortex spoilers?