NASA AD-1 Oblique Wing

[Pieliker96]

https://imgur.com/8WC3L7g

The NASA Ames-Dryden 1 is a fairly wack exercise in variable geometry. The real thing was limited to relatively low speeds due to aeroelastic concerns, in addition to the fact that it had been built on a shoestring budget of $240K. I've built the wing and associated actuator rather stout to counter the aeroelasticity - though, in the spirit of the real thing, most of what I'll be building it with is already available to me - I'll only be buying the EDFs and ESCs new.

Here's some pictures of the build process:


Wing going together. Note the main spar (0.25" x 0.75" birch ply) and mounting plate.


Here's the actuator, it's the same I used in the B1-B project - the Actuonix L12-R in the 100mm stroke variety. Actuation speed is rather low but isn't critical in this application.


Some pics of the glue-up of and of the completed wing pivot mechanism. It's constructed of 1/8" plywood and rides on a 1/4" diameter zinc-plated jesus bolt with a nylock nut. Total actuation range is 0 - 65° - the real thing did 0-60°, I wanted a little extra to make storage easier. It was built to the highest engineering standards of "looks strong enough, she'll be aight".


Tail assembly, empennage, and main gear. I used ES09MDs for all control surfaces along with a 10A BEC for flight control. The main gear slots into the fuselage in the traditional FT style, the fuselage is almost entirely monocoque with a good bit of paper removed to save weight.


Installed wing actuator and completed fuselage. The space behind the cockpit will serve as the battery hatch, the tray for which I have yet to make. The nose wheel is steerable and tied to the rudder channel by means of a 5g micro servo with a slot in its control arm.


Aircraft sans motor pods, EDFs, and ESCs. Wingspan (unswept) is 67". With a projected all-up weight of 1400g, Cube loading is around 9. I'm planning on using twin 50mm EDFs on 4S, which will be installed a few months from now (college being what it is). That'll give it a thrust-to-weight of around 0.8, as opposed to the real thing's abysmal TWR of 0.21 - it's easier to get away with low TWRs with highly efficient wings and miles of runway, a luxury scarce in the hobby world.

One of the interesting consequences of the oblique wing is a coupling between roll and pitch control: Applying roll deflects the ailerons in opposite directions, which, since one is aft of and one is fore of the CG, pitches the craft up or down. I've added a couple of mixes to counter this effect. In the real thing, pilots reported the coupling was manageable under 45° but became more of a nuisance as sweep approached 60°, during which the aeroelastic effects became more pronounced. There is a significant, higher-than-usual chance of this thing breaking up in-flight due to aeroelasticity and/or flutter of sorts. The easiest way to find out is to just go and fly it!

Maiden Flight NET May 2021.

 

[leaded50]

enjoy the build idea! Lets know how it fly!

 

[jfaleo1]

https://imgur.com/8WC3L7g

The NASA Ames-Dryden 1 is a fairly wack exercise in variable geometry. The real thing was limited to relatively low speeds due to aeroelastic concerns, in addition to the fact that it had been built on a shoestring budget of $240K. I've built the wing and associated actuator rather stout to counter the aeroelasticity - though, in the spirit of the real thing, most of what I'll be building it with is already available to me - I'll only be buying the EDFs and ESCs new.

Here's some pictures of the build process:

View attachment 188394
Wing going together. Note the main spar (0.25" x 0.75" birch ply) and mounting plate.

View attachment 188396
Here's the actuator, it's the same I used in the B1-B project - the Actuonix L12-R in the 100mm stroke variety. Actuation speed is rather low but isn't critical in this application.

View attachment 188395 View attachment 188397
Some pics of the glue-up of and of the completed wing pivot mechanism. It's constructed of 1/8" plywood and rides on a 1/4" diameter zinc-plated jesus bolt with a nylock nut. Total actuation range is 0 - 65° - the real thing did 0-60°, I wanted a little extra to make storage easier. It was built to the highest engineering standards of "looks strong enough, she'll be aight".

View attachment 188398 View attachment 188399
Tail assembly, empennage, and main gear. I used ES09MDs for all control surfaces along with a 10A BEC for flight control. The main gear slots into the fuselage in the traditional FT style, the fuselage is almost entirely monocoque with a good bit of paper removed to save weight.

View attachment 188400 View attachment 188401
Installed wing actuator and completed fuselage. The space behind the cockpit will serve as the battery hatch, the tray for which I have yet to make. The nose wheel is steerable and tied to the rudder channel by means of a 5g micro servo with a slot in its control arm.

View attachment 188403 View attachment 188404
Aircraft sans motor pods, EDFs, and ESCs. Wingspan (unswept) is 67". With a projected all-up weight of 1400g, Cube loading is around 9. I'm planning on using twin 50mm EDFs on 4S, which will be installed a few months from now (college being what it is). That'll give it a thrust-to-weight of around 0.8, as opposed to the real thing's abysmal TWR of 0.21 - it's easier to get away with low TWRs with highly efficient wings and miles of runway, a luxury scarce in the hobby world.

One of the interesting consequences of the oblique wing is a coupling between roll and pitch control: Applying roll deflects the ailerons in opposite directions, which, since one is aft of and one is fore of the CG, pitches the craft up or down. I've added a couple of mixes to counter this effect. In the real thing, pilots reported the coupling was manageable under 45° but became more of a nuisance as sweep approached 60°, during which the aeroelastic effects became more pronounced. There is a significant, higher-than-usual chance of this thing breaking up in-flight due to aeroelasticity and/or flutter of sorts. The easiest way to find out is to just go and fly it!

Maiden Flight NET May 2021.

I actually saw this very unique airplane fly at Oshkosh many years ago. It was SO small but really cool. Good luck!

 

[L Edge]

You picked a good project. If my morphing project was a bust, was going to try an offset oblique to see what happens.

Since it worked, didn't want to destroy it. If the offset oblique actually would fly, it would be something.

My initial concept that I envisioned to explore was put an EDF's under each wing so as the wing is rotated, the EDF is pivoted so it is always parallel to the fuse.l Would it reduce fluttering etc?

 

[Pieliker96]

My initial concept that I envisioned to explore was put an EDF's under each wing so as the wing is rotated, the EDF is pivoted so it is always parallel to the fuse.l Would it reduce fluttering etc?

It may do by reducing the resonant frequency of the structure through more inertia about the pivot point.

Having propulsion on each wing greatly increases magnitude and type of loading the wing pivot will experience, meaning it'll have to be built stronger (heavier). It'll also require the swivel system, which introduces further complexity and weight: The F-111 had enough trouble as it is with a couple swivelling pylons for armament, I can't imagine the nightmare that swivelling engines would be. Luckily for us, working on the hobby scale is much easier than on a full-scale aircraft, and we don't have to worry much about the practicality of things from an engineering perspective so long as it's interesting and fun. I'd say go for it!

 

[Monte.C]

https://imgur.com/8WC3L7g

The NASA Ames-Dryden 1 is a fairly wack exercise in variable geometry. The real thing was limited to relatively low speeds due to aeroelastic concerns, in addition to the fact that it had been built on a shoestring budget of $240K. I've built the wing and associated actuator rather stout to counter the aeroelasticity - though, in the spirit of the real thing, most of what I'll be building it with is already available to me - I'll only be buying the EDFs and ESCs new.

Here's some pictures of the build process:

View attachment 188394
Wing going together. Note the main spar (0.25" x 0.75" birch ply) and mounting plate.

View attachment 188396
Here's the actuator, it's the same I used in the B1-B project - the Actuonix L12-R in the 100mm stroke variety. Actuation speed is rather low but isn't critical in this application.

View attachment 188395 View attachment 188397
Some pics of the glue-up of and of the completed wing pivot mechanism. It's constructed of 1/8" plywood and rides on a 1/4" diameter zinc-plated jesus bolt with a nylock nut. Total actuation range is 0 - 65° - the real thing did 0-60°, I wanted a little extra to make storage easier. It was built to the highest engineering standards of "looks strong enough, she'll be aight".

View attachment 188398 View attachment 188399
Tail assembly, empennage, and main gear. I used ES09MDs for all control surfaces along with a 10A BEC for flight control. The main gear slots into the fuselage in the traditional FT style, the fuselage is almost entirely monocoque with a good bit of paper removed to save weight.

View attachment 188400 View attachment 188401
Installed wing actuator and completed fuselage. The space behind the cockpit will serve as the battery hatch, the tray for which I have yet to make. The nose wheel is steerable and tied to the rudder channel by means of a 5g micro servo with a slot in its control arm.

View attachment 188403 View attachment 188404
Aircraft sans motor pods, EDFs, and ESCs. Wingspan (unswept) is 67". With a projected all-up weight of 1400g, Cube loading is around 9. I'm planning on using twin 50mm EDFs on 4S, which will be installed a few months from now (college being what it is). That'll give it a thrust-to-weight of around 0.8, as opposed to the real thing's abysmal TWR of 0.21 - it's easier to get away with low TWRs with highly efficient wings and miles of runway, a luxury scarce in the hobby world.

One of the interesting consequences of the oblique wing is a coupling between roll and pitch control: Applying roll deflects the ailerons in opposite directions, which, since one is aft of and one is fore of the CG, pitches the craft up or down. I've added a couple of mixes to counter this effect. In the real thing, pilots reported the coupling was manageable under 45° but became more of a nuisance as sweep approached 60°, during which the aeroelastic effects became more pronounced. There is a significant, higher-than-usual chance of this thing breaking up in-flight due to aeroelasticity and/or flutter of sorts. The easiest way to find out is to just go and fly it!

Maiden Flight NET May 2021.

Boy that is really a piece of work. I don't mean the wing - that may or may not work for you. I mean your build techniques & build style & precision. I'm really impressed.

 

[Pieliker96]

EDFs installed, CG in the right place, taxi tests successful - Ready for flight
​

50mm EDFs are so small and cute! They're being driven by some extremely small and lightweight 45A EMAX ESCs on 4s. Duct outlet area is 93% FSA. I'm also using a 10A BEC since the ESCs don't have UBECs.


Balancing this thing with a 3000 4 cell proved impossible (the battery would have to be inside the wing sweep mechanism!) so I ended up adding some tail weight in the form of four AA cells. This is, surprisingly, the first time I've ever had to add dead weight to get the balance on point.


This plane simultaneously has the highest aspect ratio and highest cube loading (~11) of any plane I've had to date. It clocks in at a hefty 1.72kg with a 3000 4 cell - or, if battery life and discharge rate prove to be less of a concern, 1.55kg on a 2200 4 cell. I'm expecting to have to treat it like a high-performance jet, even though it may look like a glider in some regards.

 

[Pieliker96]

We've had a successful maiden flight!

Takeoff was more sudden than I was expecting due to the natural up-trim of the aircraft, which was taken out with a good bit of down-elevator. Climbout was easy as thrust-to-weight was sufficient. The high aspect ratio minimizes the effects of induced drag which makes it more difficult to perceive when one is approaching a stall or the backside of the power curve. With that said, it was much more slick in the air and cruised far better, especially at low speeds, than the draggy delta-wing EDFs I've flown in the past - the airframe felt very aerodynamically efficient in the air. I found that the mixes I set up to counter the roll-pitch coupling with wing sweep were overly aggressive, exacerbating the effect in the opposite direction as intended. I've since reduced them to compensate for the next flight. Going to full wing swing probably requires more speed than I gave it, that'll be something to test in future flights. On landing, the low induced drag made it difficult to bring the craft down on the runway, and I ended up doing multiple go-arounds. I need to practice landing at my feet, rather than crossing the threshold with gobs of altitude. The battery was at just 3.94v/cell after landing, so I'll be upping my flight timer to 6 minutes instead of the previous 3:30.

Overall the performance was good and it flew well, apart from the expected oddities with swinging the wing.

 

[Monte.C]

So floaty! That flies great. I suppose with the wing "swung", ailerons work to twist the plane in yaw. (?)

 

[Pieliker96]

So floaty! That flies great. I suppose with the wing "swung", ailerons work to twist the plane in yaw. (?)

I don't have a way of observing it clearly in flight but I tried to minimize this effect with heaps of differential aileron - deflecting the upwards aileron farther upwards than the downwards aileron to minimize adverse yaw, which in this case (hopefully) reduces torque on the pivot.

 

[Scotto]

Congrats! Very impressive building and piloting skills! WOW

 

[ThomasMartino]

Congratulations! I love how floaty it is. I bet you could thermal it on a good day. Swinging the wing back and diving down would be fun.

 

[Stress Test]

Takeoff was more sudden than I was expecting ...

I looked at your plans link, are you going to put a set for this up?

A jet that takes off like that and flies that slow has appeal!

Drop the pivot mechanism to lighten it a bit and I see a great jet trainer. (Hint, hint,hint...)

 

[Pieliker96]

I looked at your plans link, are you going to put a set for this up?

A jet that takes off like that and flies that slow has appeal!

Drop the pivot mechanism to lighten it a bit and I see a great jet trainer. (Hint, hint,hint...)

If you'd like to take the files I've got and run with them, here they are. This was another project intended to be a one-off where the "plans" and associated work files' quality was just high enough to be able to be assembled into an airplane by the designer - There's no instruction manual, they're not at all polished, and I have little reason to improve them now that the only version of them I've made has already been built. If you'd like to have a go at building one, then do so - just be aware that you'll likely have to put in a good bit more work than your average set of plans.

As for the feasibility as an EDF trainer:
Negatives:
-With calm winds, it wouldn't fly as slow as on video. The maiden flight had a significant (7-10 mph) headwind. Field members reported seeing a significant velocity delta between upwind and downwind legs on the maiden flight. Takeoff distance was much shorter than I expected due to the wind, and it's still quite heavy for its wing area on paper - nothing that couldn't be solved with some weight savings, of course.
-The low induced drag of the high aspect ratio wing makes it difficult to see the effects of the drag increase near a stall. Delta wing platforms warn of impending stalls much earlier at the cost of being less aerodynamically efficient. They also, in my opinion, give a better experience in flying "on the backside of the power curve", which I believe to be one of the most defining differences between EDFs and prop planes.
-A 67" wingspan and an even longer fuselage may be a bit too large for some people to transport. This also isn't the kind of plane you can fly at your local park - a dedicated flying field is required.
Positives:
-Battery life with the current setup is projected to be around six minutes, which is nearly twice that of the average EDF. I attribute this largely to the efficiency of the wing.
-The design is simple: No flaps, retracts, speedbrakes, etc. to worry about, just the standard 4 channels. Unless, of course, you also go for the pivoting wing.
-The electronics used are similar to other twin 50mm setups, so the guts can be reused once the airframe has served its purpose.
-High-wing conventional designs are familiar and forgiving. Using counterrotating fans nixes any small amount of torque and eliminates adverse turning tendencies. The plane seems to fly predictably and well.

Summary / TL;DR: There are "plans" which were not meant to be proper plans. It's probably not the best EDF trainer.

 

[Stress Test]

Its been a while since I looked at the first few posts, I forgot how big this is! The animation of it on the floor gives an indication.

Thanks for the plans BTW. I may never build it but then again, I might. I have another one on the bench to finish before I even think of anything new.

 

[Pieliker96]

I put three more flights on the AD-1 today and got it dialled in pretty well. Here's my new desktop background:

And some more flight footage, including significant time spent with the wing fully swept.

 

[Flightspeed]

How does that even fly!?🤯

 

[Pieliker96]

How does that even fly!?🤯

the center of lift stays in more or less the same position and the effective wing area stays the same. Cross-control coupling and the asymmetry become somewhat of an issue but less than it looks like

 

[Flightspeed]

What’s swinging the wing like that suppose to achieve?

 

[JasonK]

What’s swinging the wing like that suppose to achieve?

https://www.nasa.gov/centers/dryden/history/pastprojects/AD1/index.html

similar to other variable sweep planes - straight out for lift at low speeds, less drag a higher speeds.