Sal C.

Hi Dick

Thanks for the very kind words. I am using a simple Futaba 7C 2.4 transmitter. I will check the mixing and see if there is a delay function. I am also going to make shims to give some down thrust in the motors. This will help significantly.
Burkhard was spot on with his youtube graphic. The model is very forgiving, very stable and turns well on both aileron and rudders.
You are also correct about being a 1 speed model, similar to the full size.
I just received notice from the Smithsonian that I have been invited the the Hazy Center in early 2017 to display the model at the League of WW1 Aviation Historians meeting. Maybe the Smithsonian will accept it for their collection.

Cheers, Sal

buzzard bait

Congratulations for your fantastic accomplishment, and thank you for the excellent video!

I have a comment on trim. From the video, your airplane is very stable in pitch and yaw, therefore it does not need any more nose weight. Looking back on the the three view, there is a lot of positive incidence in the stab, almost the same as the wing. I haven't read the whole thread, but from photos it doesn't look like all that stab incidence is there. I would just live with the down trim on the elevator. The only alternative would be re-setting the stab, which doesn't seem worth it.

I wouldn't bother with down thrust either. I think the plane has a tremendous amount of power, for it's weight and size far in excess of what the original had. If you use less power on take-off, you will not need the down thrust. The rate of climb of the full scale plane was probably two to four hundred feet per minute at best. So for a model of that scale you need to spend one or two minutes to reach a comfortable altitude, rather than a few seconds.

As you say above, it is pretty nearly a one-speed airplane. Just live with the down trim on the elevator.

Wonderful job!

Jim

UStik

Sal, this is really magnificent, again Dick finds far better words than I am able to, but I wholeheartedly agree.

And it is indeed amazing how similar the real model and the simulator model behave in flight. I hadn't expected that to such a degree. Now it turns out that the model really needs much down elevator, but other than I had expected you had no problem to find out how much. I had experimented with different incidences in the simulator until the model was trimmed.

I'd agree with Jim and not add any weight neither any down thrust. I believe that the pitch-up with power comes from increased wing lift. The stab is not hit by the propwash, and down thrust on a short lever arm wouldn't be effective, anyway. In the simulator, I had neglected (set to zero) any propwash effects because I couldn't believe what I saw. Now it seems at least possible that the simulator wasn't completely wrong because propwash let the plane pitch up extremely. Without propwash, the model didn't react to power in pitch at all, so down thrust could be ineffective. The mixer proposed by Dick should do the trick, nothing else needed.

I wish you an easy landing gear repair and hope to see more flights.
Burkhard

Sal C.

Gentlemen

It was amazing to control the Ilya Muromets model in flight. Everything that Igor did during design, Polyhedral outer wing panels, reflexed ailerons which added washout, huge lifting stab, produced a very stable platform. Other than the pitch up during power, the model was very well behaved. The model has a much higher power to weight ratio than the full size aircraft. So, I really should use less power for take off.
I will still reset the elevator trims and will program some throttle, down elevator mixing. The gear will be repaired and strengthened.
Thank you again for all your support and stay tuned for more reports.

Cheers, Sal

Sal C.

Gentlemen

Last flight of the year for the Ilya Muromets. I installed shims/wedges I made to put some down thrust in the motors. I was able to take out a bit of down elevator trim. I also removed the brake from the Speed Controllers so that the props free spin when throttle off.
Had a great flight and perfect landing. Thanks again.

UStik

Hi Sal, that looks like a GREAT landing! And the airplane is looking just gorgeous. Good you managed to do this flight before the winter.
Burkhard

UStik

Hi Sal, hope all is well with you and the behemoth.

Nothing new actually, except that I have a new PC with a powerful graphics card whose driver is able to capture high-quality video. So I just made a new video of the simulator flight, now (nearly) without jerking. It will be at YouTube soon. For what it's worth...

Burkhard

Sal C.

Hello Burkhard

It has been an amazing year with the Ilya Muromets. First meeting the Sikorsky family, then the test hop at the Old Rhinebeck Aerodrome and subsequent flights. I was invited to give a talk at the Smithsonian and it has been featured in Flight Journal, WW1 Aero, Aviation History and now Air and Space online. I just returned from the annual hobby trade show in Toledo where it came in 1st place in Designer class and Best of Show.
The Smithsonian Museum has show interest in acquiring it for their collection and I am hoping that this comes to pass.
How is everything with you?



Nikolai Sikorsky being interviewed.

CHeers, Sal

otrcman

Wonderful, Sal,

All the attention that you and the airplane are getting is fully deserved. What are you going to do for an encore ?

Dick

Sal C.

Hey Dick

How are you doing? Encore? It's all down hill for me now. I'm just gonna build some models to fly at my local field to have fun
with my friends.

Cheers, Sal

UStik

Hi Sal, that are great news, congratulations! I'm not sure what down hill means though, hope it is good for you. I'm retired now and intend to visit the US this summer. The Smithonian is on my list so I'm hoping with you.
Best wishes, Burkhard

BMatthews

https://www.youtube.com/watch?v=I-3_cXuiNQM

Sal, I lost track of this thread and just got caught up on it. A heartfelt congratulations on all you've done with the Illya Muromets both at the display events and for your first flights. I found the video above which is the one where the gear broke off on touch down. That's the only one I could find. I sure hope the damage was not hard to repair.

The model looks positively fantastic in the air. You must be as proud as a new father... . And likely were nervous as a new one as well... Just one helluva impressive job in all respects.

Out of interest where did you finally balance the model? As in % of the wing chord.

Sal C.

Burkhard

Your video is excellent. Just like the full size and the model I built, your video shows the Ilya Muromets flying nose down in level flight.
Thanks for taking such an interest in the build process and assisting with the technical information including Center of Gravity.
What I meant by "down hill" is that the Ilya Muromets is the highlight of my modeling achievements. It is doubtful that I will be able to reproduce another such model. Please keep me informed about your trip the US, maybe I can meet you.

B Matthews

Thank you for all the kind words. I am simply thrilled about the outcome and the interest this model has garnered. I balanced the model
at around 80 percent of chord. It does fly well in all axis, but wants to climb like crazy with power. The gear was easy to repair, the lower skid broke in half. I made stronger skids.
Here are a couple more vids on youtube representing the first test hop at the Old Rhinebeck Aerodrome.

https://youtu.be/qLZpc70v09M


https://youtu.be/YSihTrTcgBI https://youtu.be/bO-NhLvo_rE

Cheers, Sal

BMatthews

80%.... amazing. And from the sounds of it perhaps still too far forward if it's responding strongly to added throttle. I know it hasn't had a lot of air time but do you have a feel for how it responds to a dive in terms of how rapidly it pulls out if the stick is simply neutralized?

It's been a real treat seeing this all take place. And the guy in that one video is right. You deserve all the accolades and to take a bow for a fantastic job.

Sal C.

BMatthews

Knowing that the model may/might end up in a museum, I was gentle on the controls during flight. While I found it responsive in all axis, I did not dive the model at anytime. I did pull back on the throttle and introduced a little down elevator to drop down for a low pass.
During flight, the only thing I really noticed was lots of climb with throttle.

Cheers, Sal

UStik

In the simulator, the model showed not only lots of climb - it reared up. Downthrust didn't help much, and different balance points didn't either. Down elevator helped, but for the strong pitching-up effect it was hard to allot the right amount of it. That's why I contemplated using a gyro. But there's no gyro in my simulator, so I completely removed the effect from the simulator model to have the model's actual behavior only - so to speak. Particularly since I couldn't believe the effect shown by the simulator being realistic.

The interesting point is how the rear-up effect could be removed: by setting propwash to zero. Finding a realistic propwash speed is one of the problems with this simulator, and probably I had set too much so the simulator model reared up more than the real one. I can imagine though that, because the model (both simulator and real) is substantially heavier and has more power (both relatively) than the full-size airplane, the latter didn't show a noteworthy amount of that effect.

Anyhow, I think it's the propwash blowing over the lower wing (and under the upper) making for much lift. In the simulator, the rear-up occurred virtually without any ground roll, the airplane's front just took off, the tail still on the ground. My first experiments were with a dummy appearance (another 4-engine model) which has the stab in the propwash. That didn't rear up not nearly as much as the real configuration with the stab high above the propwash.

Perhaps would need a CFD tool to prove or disprove this interpretation.

For what it's worth...

Sal C.

Hello Burkhard

I did not experience such a rear up as you did with the simulator. On one takeoff, I did go to full throttle and she climbed out at around around 60 degrees, but I input down elevator and she leveled out nicely. It was after this flight that I put some down thrust in the motors. This did help a bit as I had to remove some down elevator for level flight. I believe you are correct, the model has far more power to weight ratio than the full size. Nevertheless, I am very happy with its flight envelope.
When are you planning a NYC trip?

Cheers, Sal

otrcman

This nose-up tendency on takeoff is interesting. Perhaps Burkhard was prescient in his post #39 two years ago when he said, in part:


"What I didn't consider so far is the IM's behavior when power is reduced to commence the landing approach. Since the whole stab is blown by the propwash and since the wing must be influenced as well and both have undercambered airfoils, it could be interesting. ........."


In the quote, Burkhard is concerned with power reduction on landing approach, rather than power addition on takeoff. But the phenomenon is the same. It's called Propulsive Lift. When the airspeed over the wing is increased ("propwash") the wing lift is increased. The stab lift is increased a bit also, but the speed of the propwash is diminished somewhat by the time it reaches the tail. So, in effect, the airspeed of the wing becomes greater than the airspeed of the tail as you add power.

Propulsive lift is most noticeable on an airplane where multiple engines are mounted on the wing leading edges. Think B-17 or B-29. But on these airplanes, the propulsive lift effect just adds to wing lift. It doesn't make the nose pitch up or down because the added lift is pretty much acting at the CG.

The ilya is different from a B-17 or a B-29 in that the net lift of the wing is well ahead of the CG. So the increased lift generated by propwash has a lever arm to cause the nose to raise. The net effect is that large power increases cause the nose to pitch up.

In your recent post #166, Burkhard, you seem to be getting closer to the answer:


"Anyhow, I think it's the propwash blowing over the lower wing (and under the upper) making for much lift. In the simulator, the rear-up occurred virtually without any ground roll, the airplane's front just took off, the tail still on the ground. .........."


All of the indications of this rearing-up have been showing up in Burkhard's simulation, but we didn't think I was real. Now the actual model is doing the same thing to a lesser extent. We just didn't put it all together until now. The simulator knew, but we didn't appreciate what it was telling us.

Hope this makes sense.

Dick

Sal C.

Hi Dick

When I reduced the power for landing, the plane behaved quite normally, an almost flat approach, maybe a little tail high. It was really uneventful.
Hey, I dont understand all this but I am happy with the results.

Cheers, Sal

otrcman

I'm sorry, Sal. When I finally figured out an answer to the rearing up problem I got all excited and reverted to "engineer speak".

The bottom line is that the rearing up on takeoff is probably due to propwash over the wings. You can minimize the effect by limiting the power you use for takeoff. Excessive power makes the effect worse.

​​​​​​​Dick

Sal C.

Dick

Absolutely, on the last two flights, which were not video recorded, I used less power for takeoff and used throttle management once airborne for a
nice shallow climb out. No apologies necessary, although I don't understand all the "Engineer Speak", I certainly like to read it.

Cheers, Sal

Sal C.

Hi Dick, Burkhard

I hope this posting finds both of you well. Saturday, Oct 14th I was invited by the Sikorsky family, Sikorsky Archives to display the Ilya Muromets at the Sikorsky Corporation Family Day. I was told around 15,000 came through. The Sikorsky brothers were busy all day signing autographs. I was busy answering questions about the model.
It was a great day!

otrcman

Thank you for the update, Sal. I'm proud to have been even a small contributor to this effort and also bet Burkhard feels the same. Those last few pictures of the model in flight are the most realistic photos of a model airplane that I've ever seen.

​​​​​​​Dick

UStik

Yes indeed, I wholeheartedly agree! And I can add that not only the still photos are realistic but also the videos. Sal, you have perfectly flown this extraordinary behemoth so it looked like the real thing, and you didn't need help by gyros, which I had contemplated to no avail. You just flew it despite its unusual behavior.

Just in the last few days I tested a gyro flight stabilizer in my Sr. Telemaster and have to say that it wouldn't really have helped with the IM maiden-flight problem. Finding and holding the right amount of down elevator would be still up to the pilot. A lock-mode gyro would hold a certain attitude but then changing pitch for climb or descent is tricky, or at least it needs getting used to and that is not what you need on a maiden flight.

All in all, a lock-mode stabilizer is not bad but does not really help normal flying. In a turn, the airplane is banked and the turn means continuous pitch-up, which the stabilizer will fight. So you have to work the elevator in turns like you have to work the tail rotor of a helicopter with a heading-lock gyro. So much to lock-mode gyro for elevator. Damping mode is a good thing for all three controls and feels natural; it lets the airplane appear to be "bigger". Dick, thought I tell that here just for what it's worth...

Burkhard

Sal C.

Dick, Burkhard

Thanks again for all your assistance with the Ilya Muromets project. The actual building of the model was very enjoyable but the anxiety over what the first flight would be like really stressed me out. In the end, I was very pleasantly surprised how stable it is. An aircraft anyone could fly.
Just FYI, here is my next project. This model is a 1/5 scale Najakima Hayabusa (Oscar) and will be the companion to my 1/5 scale Zero. The model is built, gear installed, engine installed and primed. Next step is to add panel lines, rivets, install servos, etc.

Cheers, Sal