Pushing The Envelope

[Sikorsky]

Exp J3, RR90 with somewhere around 110 hp. Currently on Federal 1500AWB hydraulic skis. I’m comfortable upside down in a Cub but I have never spun a Cub on skis. For those who have done this, what are the characteristics of a draggy ski during a spin?

One can continue down the line of questioning: snow shoes tied to struts, external load, normal operation configuration of a working airplane, and how, if at all, it affects spin characteristics.

I’d like to know the full capabilities and where exactly the edge is.

Thanks

Sikorsky

[BC12D-4-85]

Don't let the bungees stretch in flight

Gary

[cubdriver2]

Don't let the bungees stretch in flight

Gary

Even if they flip down it's no big deal. Most of us who have flown Summit have had at least one or both flip down while picking up speed in a driving turn

Glenn

[BC12D-4-85]

If at speed and power and the bungees stretch you may recover if prepared. Depends on ski shape/size in front of the axle, the length of the down limit cable, and the strength of any retract bungee or spring. Ask Landes Skis about this effect.

Edit: To clarify I have no idea what forces react on skis during a spin when airspeed is low...but if recovery requires added "G's" and evolves into excessive airspeed I'd pay attention. If the ski's nose drops expect added drag from one or both.

Gary

[BC12D-4-85]

Even if they flip down it's no big deal. Most of us who have flown Summit have had at least one or both flip down while picking up speed in a driving turn

Glenn

Do you think that flip's acceptable? Just curious why you'd let it continue. Your experiment of course.

Gary

[skywagon8a]

I have never spun an airplane on skis, on floats yes, but skis no. Spins are a stall maneuver. there is no need for there to be any high speeds at any time during recovery. Added weight on an arm below the vertical CG tends to increase the rate of rotation. I would suspect with skis not as much as a set of floats. When recovering from a spin, as soon as you have stopped the rotation (breaking the stall) immediately pull back on the stick to raise the nose. This will prevent a buildup of speed which would then react in attempting to pull the skis nose down. In other words get the nose up as soon as the spin rotation is stopped. As long as the nose is left down, the speed will build rapidly. While in the spin the speed will remain very low (stall speed). During proper spin recovery the speed gain should never reach normal cruise speed. In a Cub, perhaps 70 mph?

A spin imparts the same stresses on an airplane as is done when one wing drops quickly in a stall. The only difference is the nose is pointed down in a spin while only a little bit nose low in the one wing stall.

IF you have a high airspeed while in a "spin", the airplane is not spinning even though it looks and feels like it is. That is a spiral. During a spiral the speed builds rapidly to a high number. This could be a more dangerous maneuver because of the possibility of overstressing the airplane during a recovery attempt. If your CG is not at or near the aft limit you may not be able to get a complete stall break. If this happens you will have a high speed with the nose down. This is not a spin and you should stop the maneuver before the speed gets too high. I had to ballast my Cub on floats to the aft CG limit in order to prevent spiral dives instead of a spin.

How many of you have looked at the airspeed indicator during the spin? Usually the pilot is looking out the windshield during a spin.

IF you still have reservations ... sneak up on the spin. Do a 1/2 turn and recover. Then 3/4 turn etc.

Why are you wanting to do spins? Is this just to be more informed, or are you getting a certification for your airplane? For certification you must complete one full turn in the spin before initiating recovery. Then the recovery must be completed in no more than one additional turn.

Piper would have spun the Cub when they certified skis.

[cubdriver2]

Do you think that flip's acceptable? Just curious why you'd let it continue. Your experiment of course.

Gary

Not acceptable, I rigged them just like all the others. Didn't happen first couple flights but saw something on the ground one time and turned and descended gaining speed and bang bang. Almost no change in how it flew. Added 2" to rear cable and never happened again. The 2 SC here on Summits rigged by Summit did the same thing till we added 2" ( chain repair link ) to rear cable

Glenn

[BC12D-4-85]

I did have a set of Airglas L2500's extend on a 7GCBC in winter. Once. Rolled the airplane and out they came half way around - bang bang like Glenn notes. Stopped that dumb stuff and installed AD springs. I did lots of stalls but checked this AM and didn't see spins noted, so maybe there was a placard not to or I didn't. I spun it often on tires. It could speed up quick on recovery if allowed with the clean spring gear. I could get about 130 IAS with a CS speed prop and they never extended with the springs.

Gary

[skywagon8a]

I did have a set of Airglas L2500's extend on a 7GCBC in winter. Once. Rolled the airplane and out they came half way around - bang bang like Glenn notes. Stopped that dumb stuff and installed AD springs. I did lots of stalls but checked this AM and didn't see spins noted, so maybe there was a placard not to or I didn't. I spun it often on tires. It could speed up quick on recovery if allowed with the clean spring gear. I could get about 130 IAS with a CS speed prop and they never extended with the springs.

Gary

If those skis were STCd on the 7GCBC, they did pass the one turn spin test. It's mandatory for all single engine airplanes for certification to complete a one turn spin with recovery prior to the completion of the second turn. Along with that there will be a placard which states "Intentional spins prohibited". IF intentional spinning was approved, the test for certification would be to prove a successful 6 turn spin with one turn to recover.

[BC12D-4-85]

The Airglas L2500A's are STC'd. I don't see anything regarding spins in their linked STC files. On floats intentional spins were prohibited in the TCDS A-759 Note 2 section, but I don't note spin restrictions on their Item 203 skis including Federal Model AWB-1500A wheel skis. So maybe they aren't placarded against spins in that application? The no-spin placard I had was apparently for the EDO 2K's that were installed.

Gary

[skywagon8a]

The Airglas L2500A's are STC'd. I don't see anything regarding spins in their linked STC files. On floats intentional spins were prohibited in the TCDS A-759 Note 2 section, but I don't note spin restrictions on their Item 203 skis including Federal Model AWB-1500A wheel skis. So maybe they aren't placarded against spins in that application? The no-spin placard I had was apparently for the EDO 2K's that were installed.

Gary

You missed my point. ALL single engine airplane have to pass the one turn spin test in order to be certified. That includes any add on STCs. THEN the FAA requires there to be a placard which states: "Intentional spins prohibited". Any paper work which a customer receives will not mention spins. The spins were done during the experimental phase.

[Cubus Maximus]

Springs are better...

[BC12D-4-85]

Perhaps like ships passing in the night we both missed the point? If so I apologize. From the factory the 7GCBC has no placard for "Intentional Spins Prohibited" except on floats per A-759, which is added upon installation. Apparently on conventional gear/landplane configuration spins are approved, as are some skis per TCDS. Airglas doesn't mention a placard that I can find for their STC'd skis, but maybe one is included. I don't recall.

But more of a circling back to the OP's question. For the factory J-3 TCDS A-691 Item Skis 310 (w). lists:

"*(w) Federal Model AWB-1500A wheel-ski, installed in accordance with Federal Aircraft Works, Minneapolis, Minnesota, Dwg. 11R560. The following placards are required on ski position selector box: "SKI CONTROL" "UP-NEUTRAL-DOWN""

What does this mean? Did Federal require a placard prohibiting spins? Did they test them beyond one turn? The OP would like to know where exactly the edge is. I don't know but maybe someone does.

Gary

[skywagon8a]

The OP has indicated his J-3 is experimental and has not yet responded. So to answer his question I am on hold for anything further. The 7GCBC has been certified a bit differently in that in some instances spins are not prohibited, so we had better not mix apples and oranges.

[courierguy]

Springs are better...

Spooky picture! I have trained myself to always block up the tips of the Datums, to unload the bungees while hangared, and out of the sun of course. Plus my attach points (the firewall) give me a lot less angle (more vertical) than going back to the gear pivot bolt.

[BC12D-4-85]

Hmmmm....after some ancient recall I think the small Federal W/S like AWB-1500A's don't use bungees. Just the external erector mechanism to change configuration, and some safety cables. If so forget the bungee concerns discussed earlier.

Gary

[mvivion]

Our Huskys on Aero 3000 sis would “go down” easily with a bit of nose down elevator, and pop right back up with aft stick. When they went over there was almost no pitch change.

But, like courier guy, we always attached fwd cables at the firewall, NOT at gear attach. I really don’t like cables attached at gear bolts.

MTV

[BC12D-4-85]

While we await the OP's return...AC 43-13-2B's ski rigging recommendations. Pay attention to page 44's diagrams and particularly angle "B" Fig. 5-5 of at 20* minimum. That's why MTV prefers the firewall or lower motor mount instead of the forward gear fitting...potentially offers a larger angle with the ski nose down which can be a stronger pull from the bungee at full deflection/high airspeed. They also recommend bungee tensions.

Gary

[cubdriver2]

https://www.facebook.com/reel/153292...&s=yWDuG2&fs=e

Glenn

[Farmboy]

https://www.facebook.com/groups/8668...ibextid=Nif5oz

Glenn

Glenn, not sure what you want to show but the link is just to the entry page (for me).

Skywagon, regarding spins I know you're the man but spin testing with floats? Not for me thanks. My EXP PA-18-95 had skis on it that worked well, but I will say that in particular once, and maybe two or three times I believe the skis blanked out some control authority in a slow descending attitude, and slow turning descent. Really got my attention.

pb

[skywagon8a]

pb, Yes, spins with idle power and full power, flaps up and flaps down, ailerons into the turn and out of the turn along with every combination possible.

I'll tell you about a flat spin sometime. A seaplane, though not on floats.

[cubdriver2]

https://www.facebook.com/reel/153292...&s=yWDuG2&fs=e

Glenn

[hotrod180]

Exp J3, RR90 with somewhere around 110 hp......

What's an "RR90"?

[skywagon8a]

https://www.facebook.com/reel/153292...&s=yWDuG2&fs=e

Glenn

Never ever attempt a snap roll at 3 feet agl.

What's an "RR90"?

Roles Royce built the Continental 0-200 under license for the Cessnas which were built under license in Europe..

[BC12D-4-85]

Also an O-240 version. There was one locally in a PA-18 for some time. Then converted to an O-320-pilot aged out-plane sold. He said the -240 was sporty.

Gary

[Farmboy]

Glenn I’m pretty sure that was the shotgun approach.
Like 12GA impact.


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[40m]

https://www.facebook.com/reel/153292...&s=yWDuG2&fs=e

Glenn

nothing like 1 1/4 ounces of steel shot

[flynlow]

pb, Yes, spins with idle power and full power, flaps up and flaps down, ailerons into the turn and out of the turn along with every combination possible.

I'll tell you about a flat spin sometime. A seaplane, though not on floats.

Skywagon.
My first spin was out of a accelerated stall in a C150 in 1978…i focused on the center the whirling field where a figured i was gonna die, shoved in full throttle and kept the yoke full back to bring the nose back until my crop duster cfi casually said “ok my airplane”
After the recovery he chuckled and remarked that full power really snugged things up. We went back up and did spins until they were fun.

He also said full power might tend to make a spin go flat. Any truth to that?


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[skywagon8a]

Skywagon.
He also said full power might tend to make a spin go flat. Any truth to that?

Not in my experience. However, I can safely say that almost anything can happen when spins are involved, all depending on what type of airplane is involved and the circumstances of that particular spin. My one flat spin happened at idle power in an airplane which usually spun with the nose pointed straight down. Sometimes it would spin slightly beyond straight down

[cubdriver2]

20 years ago I had an inverted flat one one day playing around in a Hatz biplane. I had never looped this particular aircraft but had a bunch of other ones. It flies like a Cub so it should loop like a Cub. We might have been a tad over weight and on the rear CG edge. Fell out of the top of a loop because I was entering it too slow. The seat belts got tight on my shoulders while I waited for the nose to drop like it always does. After a few more very long seconds it was still falling flat. Finally added full power and I think back stick and the nose dropped and finished the loop. The guy who owned the Hatz watching on the ground was not amused

Glenn

[skywagon8a]

20 years ago I had an inverted flat one one day playing around in a Hatz biplane. I had never looped this particular aircraft but had a bunch of other ones. It flies like a Cub so it should loop like a Cub. We might have been a tad over weight and on the rear CG edge. Fell out of the top of a loop because I was entering it too slow. The seat belts got tight on my shoulders while I waited for the nose to drop like it always does. After a few more very long seconds it was still falling flat. Finally added full power and I think back stick and the nose dropped and finished the loop. The guy who owned the Hatz watching on the ground was not amused

Glenn

You were lucky the engine was still running, or your goose would have been cooked. Power was the only thing which stopped my flat spin.

[mvivion]

Skywagon.
My first spin was out of a accelerated stall in a C150 in 1978…i focused on the center the whirling field where a figured i was gonna die, shoved in full throttle and kept the yoke full back to bring the nose back until my crop duster cfi casually said “ok my airplane”
After the recovery he chuckled and remarked that full power really snugged things up. We went back up and did spins until they were fun.

He also said full power might tend to make a spin go flat. Any truth to that?


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Thats one of the methods Airshow types use to push a spin to flat. True Flat spins are nothing to trifle with, they can become unrecoverable in many airplanes, including some approved for spins.

MTV

[frequent_flyer]

What's an "RR90"?

ref - http://all-aero.com/index.php/compon...90-o-200-o-205

"In a cooperative venture, Rolls-Royce produced these same designs in England, under separate certification, with model designations beginning RR, e.g. the Rolls-Royce RR C90-12FH is the equivalent of the Continental C90-12FH; the Rolls-Royce versions are "directly interchangeable with the equivalent models manufactured by Continental." The Rolls-Royce O-200-A powers the Beagle B.121 Pup 100, the Bölkow BO 208 C Junior, the Avions Robin DR 220, and the Morane-Saulnier MS-880."

The post with an almost correct spelling of the company name was deleted.

[flynlow]

You were lucky the engine was still running, or your goose would have been cooked. Power was the only thing which stopped my flat spin.

My instructor also mentioned that power could put us into a flat spin,it certainly increased the rotation rate. He also said power was likely the only thing to recover but likely the little Cessna didnt have enough.


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[skywagon8a]

My instructor also mentioned that power could put us into a flat spin,it certainly increased the rotation rate. He also said power was likely the only thing to recover but likely the little Cessna didnt have enough.

When I was spin testing the 185 on amphib floats using full power through the entire spin there was no tendency at all to flatten the spin. I would be interested to learn, was your instructor referring to personal experiences in the 150 or what type of airplane? Also at what CG did he experience this characteristic? I do remember years ago, a pilot was practicing solo the day before taking his private flight test when somehow he managed to spin in. What type of spin was not known.

[flynlow]

When I was spin testing the 185 on amphib floats using full power through the entire spin there was no tendency at all to flatten the spin. I would be interested to learn, was your instructor referring to personal experiences in the 150 or what type of airplane? Also at what CG did he experience this characteristic? I do remember years ago, a pilot was practicing solo the day before taking his private flight test when somehow he managed to spin in. What type of spin was not known.

Did the spin rotation increase with the application of power? It certainly did in the 150.
Sadly Alan, isn't available to answer your questions. He was my best friend and the reason I am a pilot. He hit a powerline pole a few miles from my house in a Air Tractor almost 30 years ago.

[mvivion]

The only airplane I’ve done flat spins in was a Pitts S2-B and an S-2C. With both, to flatten a spin, you could use power….with up elevator, that drives the tail down. Out spin aileron (been a while, but..) also helped flatten the spin.

the nose would rise, and stay there until you took positive corrective action, which was: Full opposite rudder, followed by elevator through neutral, and power to force the nose down. In spin aileron helped as well.

Sometimes it took a bit to recover.


Both these models of Pitts are approved for flat spins. I would NOT induce a true flat spin in any airplane that isn’t specifically approved for same.

MTV

[Farmboy]

Sadly Art Scholl didn’t like the first flat spin he did for top gun so he did another and couldn’t recover. I believe that was in a pitts.


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[Farmboy]

A good listen is episode 22 with mark Murphy in a Christen Eagle.

https://megaphone.link/AOPA4584404787


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[cubdriver2]

A good listen is episode 22 with mark Murphy in a Christen Eagle.

https://megaphone.link/AOPA4584404787


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Darn it Peter, I'm tired of Mark always coping and out doing me. Lol

Glenn