Getting out of Big Thermals

[rmartin]

What is the proper contol input to get a RES polyhedral glider out of a whopper thermal as it gets harder and harder to see.

My main concern is folding the wings from too much speed (down input). I have no problem bringing my XL3200 down with its' crow input however my Northeast Sailplane Sandy with rudder, elevator and throttle worries me.

What do you all do when it keeps going up, up up and away?

THANKS!!

[Wildewinds]

I've been in a couple thermals that will keep the plane going up unless you point almost straight down. I've actually done continuous loops in a thermal and continued to rise. Some people may say to put the stick to the corner and go into a death spiral. While that's fine when there's no wind, it will only get you further away on a windy day.

Just the other day I was so high in such a strong thermal that I was starting to get nervous (i'm guessing about 1500' - 2000' high). While I doubt the wings of a carbon Supra would fall off if I pointed it straight down for a while, I still get nervous pulling a trick like that from so far away. Your best bet is to get the plane going in a direction where you can see the angle of descent and hold a steady, yet not kamikaze, downward angle until you're out of it.

[Bagarre]

Although I've never had this problem myself, a friend of mine flips his Bubble Dancer on it's back and flies inverted to get out of boomers.

[slopemeno]

The first solution is to know when your getting close to the end of your comfort zone, and start taking action THEN. Dont wait until the plane has winked out to start thinking about bailing.

Fly to another part of the sky. Thermals can be huge at altitude- so diving half you altitude off may put right back at the base of the same thermal. Fly to the other half of your area and see if there isnt sink there (I've never had a problem finding sink SOMEWHERE).

Dont fly a white airplane under a white cloud. Contrast will give you more ability to find your plane after you momentarily lose sight of it. Black bottoms with bright colored tips and tail will help.

A spotter is never a bad idea. Frequently the spotter can keep sight of your plane since he doesnt have the workload of flying it. A friend of mine was flying an ArtHobby "Whip-it" a few years ago in a massive thermal and I was able to see it for a few minutes when he couldnt see it at all- tan wings in a smoggy sky are hard to see.

[Peytr]

Every now and then it happens. If your plane has no brakes, flaps or spoilers you should primarily prevent panic (and panic control inputs) could try:

Inverting and putting the plane in an inverted shallow dive as Bagarre wrote, if possible fly up wind. This only works on planes with a foil with a more or less flat underside. Typically light thermal gliders do have these. Flying upwind will get you out of lift the fastest. Best method in terms of burning altitude. ;

flat spinning
(pulling gently into a stall and hard rudder to finally stall it over one side. Keep elevator pulled and rudder to one side. If you're lucky your plane can flat spin, if your not lucky you're at least loosing height, repeat it if needed and don't panic). Flat spinning will not give enough sink to overcome a real boomer. Been there :rolleyes:;

Still one could hit lift which is too strong to get you down with one of these methods. Don't fly too high to prevent the situation all together and put brakes, flaps or anything optionally dragish on your next plane. You want to loose height, the penalty is speed which you will have to bleed of :D

The routines should be practised to be at hand when the lift hits. When you have to find out how to keep your gasbag in an inverted shallow dive flying in a boomer at 1500' you're likely to fail.

[daveosoar]

I remember flying a 1:1 Salto in Spain (Ithink 1979) after a 3k aero., After 3 hours I had to get down for a d**p. Itried air brakes at 20 degrees down, no help so inverted it. That worked so well the reason became redundant.
Dave.

[OVSS Boss]

When I fly my Grand Esprit, which definately has a Vne on the airframe, is to invert and start down in that attitude. Has worked everytime and you have total control.

Marc

Also, just a has been said, do not get too far out on the limb to start with.

[dharban]

With my Bubble Dancer I give it full spoiler, full up and full rudder. It spirals down in good control at a reasonable speed.

Don

[schrederman]

When I fly my Houston Hawk, I point the nose down 45 degrees and let her rip... Haven't fluttered one yet... She does whistle and comes down in a hurry. If I need to come down faster, I go vertical with full spoiler. I have gone vertical for 1000' without the spoilers, just to see if she would take it. Like I said, I haven't fluttered one yet...

Jack Womack

[torcgolf]

i flew my condor voodoo last weekend and got sucked up about 1k ft. i slowly drifted away and got really scared about diving the nose since its setup as a mild aerobatic plane. the way i got out was to fly into the wind with a little reflex and occasionally dipping the nose until i hit the sink. it was a little work but i made it out.

ive never tried rolling it and flying inverted so thats good to know.

[skipinhouston]

Back in the old days when I could actually see, I had the good luck to help a buddy of mine recover his Grand Esprit after getting sucked into the base of a cloud. He lost sight of the airlplane but I happened to spot it and I mean "spot".
It literally was a spot.
We traded airplanes and I tried to get orientationby zigging back and forth. I dropped the spoilers, put left rudder and some down trim in until I could see where it was going. Once I figured out where it was headed, I guided it back toward where we were standing.
It came home in a hurry.
Not much other control input, just spoilers, a little down trim and rudder to keep it on track.
When it passed overhead, I heard some strange noises and when we landed, the monocote had seperated from the trailing edge on the top side of the wing from root to tip.
Don't do that.
Skip in Houston

[Liberator]

Last Friday I had my Brothers EZBD up at about 1500 and decided to come down, I had to leave for the day. I tossed the spoiler to full and flew for 2 full minutes and was pretty much at the same altitude. I ended up handing him the transmitter and he finished the flight. I had it in the air for about 30 min and I'm not sure how long he was up. Great day though.

The old Maple Leaf (stick to the corner..I like the bottom left my self) imho is the best way especially at altitude. Not sure I have ever seen a day so windy that you are in a huge boomer (they tend to blow through too fast when it's that windy) and are going down wind so fast that becomes a threat to loosing the plane. My new plane wiill take the full monty dive and I am not worrind about fluttering a surface. but my SkyBird is a flat spinner in a crunch.

By the way, thats just me being kind to the SkyBird, it can take a massive dive, I just hate doing that with it.

[Fred_L]

I really don't like diving any plane at a high speed. Flutter is so often terminal. Some guys get off on the high speed sound though.

I prefer to flat spin. Spinning is nice and easy on the airframe and wings. The rapidly changing planform presentation makes it easy to keep sight of your model too.

Flying inverted is a good way to get down too and you really lose height if you do outside loops. Thermal aircraft with flat bottom airfoils tend to require quite a bit of speed in the vertical down phase in order to get enough energy to be able to complete the outside loop. An inverted airfoil trying to generate 'lift' is so draggy (that's the point) that the loop always finishes much lower than the starting altitude. Some of my aircraft make a horrible booming noise as they go around the bottom of the outside loop and I think it is the airflow separating as it is forced around the leading edge of the wing. This generates a heap of drag.

Getting really good altitude is a great feeling and makes for relaxing flying as you aren't as anxious about finding lift, but too much altitude can get the adrenalin really flowing.

I am with the other posts that recommend doing something before it gets too late. Flying to another part of the sky can get you out of strong lift. Strong lift <=> strong sink (somewhere).
F

[Curare]

I chop the throttle and drop in on a knife edge.

Oh wait, we're talking sailplanes aren't we!

One thing I have noticed is that a lot of people get 'sucked in' to a thermal that keeps them circling even when they don't want to, you're still going up, so the best thing to do is to fly upwind, fast, it'll get bumpy as hell as you exit the thermal but once you're out you should look for a way down, not in the thermal.

Thats my experience..

[Forest Flyer]

There are a many good suggestions in the above posts. It is a very good idea to explore how your R/E glider responds to the various suggested maneuvers in normal (non-boomer) thermals before you get way up into a nasty boomer. You might be surprised how poorly some of the above maneuvers work for a given glider (and how well they work in others).

I will also echo the above statements about bailing out of boomers early. That is the best strategy with a R/E glider. Took me a while to learn that with my old R/E planes.... never lost one, but I came close a couple of times.

My current gliders can all take a steep dive out of a boomer, so I don’t worry so much about them. I still don’t push my luck, and I usually bail-out of boomers fairly early.

FF

[Andy W]

One of the first things I do when setting up a new model is program the "approach control" (be it flaps, spoiler, whatever) mix to elevator so I can use full throw without the model changing attitude significantly. In the case of my AVA, for example, it will pitch down enough to keep the model flying, but with full spoiler, it looks like it's on an elevator! :)

Now, when I need to get down in a hurry, I can put in full spoiler, and not have to worry about it diving and stressing the airframe.

I also check out the spins, as stated above - in this case, full deflection elevator and rudder, on high rates, also puts me in a good steady decent. This can be combined with full spoiler, of course..

I've never had much trouble finding sink, however!
..a

[Francesco Grandi]

It seems to me you're a bunch of lucky kids, arent'you? :) ordinary problem is TO get into a boomer :)
just kidding, obviously.
The first time it happened to me i lost my sailplane. I could not see her in the sun. luckily I found her in a (plowed, grrrr....) field some half mile away.
The second time i came out flying inverted after doing some spinning.
Spin practice has another benefit, too.
Imagine: you are flying relaxed with your slow, friendly thermal sailplane and, at a time... no elevator response, the command is stuck to full up.... so, calmly you bank one side 45-60°, begin a hard turn and compensating with the rudder you spiral down to the ground at acceptable vertical speed. With A BIT of luck... no damage, elevator servo bowden unsoldered due to local friction after two years of service.
Another day at the office :)

[histarter]

It seems to me you're a bunch of lucky kids, arent'you? :) ordinary problem is TO get into a boomer :)
just kidding, obviously.
The first time it happened to me i lost my sailplane. I could not see her in the sun. luckily I found her in a (plowed, grrrr....) field some half mile away.
The second time i came out flying inverted after doing some spinning.
Spin practice has another benefit, too.
Imagine: you are flying relaxed with your slow, friendly thermal sailplane and, at a time... no elevator response, the command is stuck to full up.... so, calmly you bank one side 45-60°, begin a hard turn and compensating with the rudder you spiral down to the ground at acceptable vertical speed. With A BIT of luck... no damage, elevator servo bowden unsoldered due to local friction after two years of service.
Another day at the office :)
Big boomer eat machines that are too light for the upper air. More mass equals lower rates of climb, and velocity to run out of trouble.
No spoilers equals inverted flght that generates good sink and steeper inverted glide angles, that become 'ushered' by high drag!

[rmartin]

Thank-you for these excellent replies.

Certainly the best advice is too get out at the appropriate time before it is an 'emergency'. Its just that I wait all week for the elusive thermal and then when I find her I can't let go!!

For me the 'inverted' suggestion would be difficult as keeping a polyhedral inverted is often quite a task especially when the plane is hard to see. I would be concerned that it would progress to a dive and the inevitable pull-out would break the wings.

I'm looking for a place to hold the stick for controlled altitude loss. I was thinking of just holding full up and the porpoising would burn altitude while being gentle on the wings. I might try it at a moderate altitude. Or I was thinking of full up and full rudder. Just thoughts.

Thank-you all for your help and contribution in making this such a great forum.

Russ

[larry vincek]

Bringing a polyhedral plane down inverted is not really difficult. Do a half loop to get inverted and then feed in down elevator and rudder to set up an inverted spiral. Keep full down elevator and use rudder to control your descent.

[Hostage-46]

When I'm at the edge of sight, with a poly ship with no spoiler like my chrysalis, I just put her in a spin. It requires no real control, makes it easy to see and will solve the problem.

A proper spin is NOT a spiral, a steady state spill will be just that stable, stalled wing with auto rotation. A spiral is dangerous, building speed and g until things break.

[histarter]

When I'm at the edge of sight, with a poly ship with no spoiler like my chrysalis, I just put her in a spin. It requires no real control, makes it easy to see and will solve the problem.

A proper spin is NOT a spiral, a steady state spill will be just that stable, stalled wing with auto rotation. A spiral is dangerous, building speed and g until things break.

The inverted spin is just as easy to perform as upright. Very little practice is needed to go inverted, once the resistance barrier is broken to do so. One can trim in the down for airspeed control, and fly the machine as a rudder only, with turning response in phase with the stick. After the shock of discovering this simplicity, the typical pilot can take her down (comfortably) while steering her to enter into landing pattern altitude. Then with an attempt to stall her out and quickly tuck her upright with a half loop; go for the spot. ;)

[Note: Because of the increased airspeed and the full down mash (typically) with the stick in the corner of your choice, your machine will quickly descend (i.e. if it isn't ridiculously light - like a 1 lb GL, or 2 lb Bubble Dancer)] :D

[larry vincek]

I hesitated to call the maneuver I described a spin because it appears to be a spiral. It may actually be a spin but has the appearance of a spiral because of the rate of descent. I first used it years ago on a Bird of Time and and the only time it got fast was when I got sloppy on the recovery.

[schrederman]

It is actually a hard spiral... the dynamics of a poly ship make it darn near impossible to spin. In a spin, the glider's rotating on the actual CG and falling at about 40 degrees nose down...but falling straight down. I haven't seen a poly ship yet that would do that... Washout is also a great spin preventer. Many gliders with washout will do a spin entry and then degrade into a spiral dive... quickly...

Just my take on it... Heck, go build something that's strong enough to just dive out and quit worrying... Or, has enough spoiler to dive vertically like the Legionairs of old.

Jack Womack

[histarter]

It is actually a hard spiral... the dynamics of a poly ship make it darn near impossible to spin. In a spin, the glider's rotating on the actual CG and falling at about 40 degrees nose down...but falling straight down. I haven't seen a poly ship yet that would do that... Washout is also a great spin preventer. Many gliders with washout will do a spin entry and then degrade into a spiral dive... quickly...

Just my take on it... Heck, go build something that's strong enough to just dive out and quit worrying... Or, has enough spoiler to dive vertically like the Legionairs of old.

Jack Womack
Interesting; that was the basic symplicity factor for my Aquarius and Red Bird 2 ch designs that carried a 13% profile with a plate wing structure - that actually dove spoilerless down vertically for 2000 feet in contest tasks (to many folk's amazment). This simplified soaring approach was stripped off when velocity, instead of altitude, became the worlds favorite attribute. :o

Yes, the wobbling, poorly regulated tight spiral of the Poly bird is not a spin, but it gets the job done. Another chuckle is the fact that with inverted tight spiralling, we have wash-in instead of wash-out. :D

[Peytr]

My current gliders can all take a steep dive out of a boomer, so I don’t worry so much about them. I still don’t push my luck, and I usually bail-out of boomers fairly early.

That's another good advice. Modern materials (structural as well as radio equipment) allow for building light as well as strong planes. If you build your plane in such a way that it can withstand a near vertical dive for 100 or 200 meters you can get it out at any time.

It has been said that smaller polihedral planes are not very cooperative flying inverted. True, but I never felt the need to fly my poly HLG inverted. Low weight and reasonable stifness allow it to simply fly them down.

[Desert flier]

What sort of load can a bubble dancer take in a dive mine is qite heavy with a glow .25 and balsa fuse I would be more woried about the elevator coming of than the wings folding but have not tried any dives from high altatude yet but would be interested in other balsa bubble dancer comments

[Ray Hayes]

Dive straight down .... If you have one of my Sky Bench Bird Series kits. It is all about spar and sheeting design.

I like to get over the field at altitude, about 5 - 10 degrees off straight up, and wait for the last minute of task time. Usually my timers are in a state of panic and start nudging me ( at 71, I do tend to nod off ) to get the decent started. It is very safe to the plane and very time predictable reaching the spot in the sky that I start my 30 second count down to landing.

The best testimonial I can give about my Big Bird's wing strength is I have been flying the same set of wings for years..... 3rd place Nats RES 2002 ( or 03 ) and 3rd place Nats RES 2006 on the same wings and lots of flying inbetween.

Ray

SkyBench.com
Home of Wood Crafters

[JimNM]

If you're flying an e-glider, just pop the prop open with a click or two of throttle... on all but the most over-powered ships the increase in drag will allow you to point the nose down quite a bit without overspeeding the wing. I use this technique to adjust my speed on final approach (before dumping spoilerons on the two ships that have them...)

I have also found that a dive willbleed off more altitude with less stress if you dive with the wind... slow down, turn into the wind and work your way back up field, dive with the wind... repeat until you can breath again.

[Desert flier]

How can the wind make any defference when in the air ????

[JimNM]

It's due to my perspective when stationary on the ground. True Air Speed is impossible to guage when flying RC - unless you have a remote pitot system that reports back to you. I overstated the above - but it comes down to this -

Flying with the wind, you will cover more ground - Flying against the wind, you'll fly through more air to cover the same ground. I dive down wind to increase my chances of NOT overspeeding the wing. It's all a matter of touch/feel. Luck to you!

[kwmtrubrit]

I needed to get out of lift twice today :D . I first time I used full spoilers but didn't feed in any up elevator. I'm lucky to have my plane, it dived straight down before I had a chance to compensate. Now there's a dilema. How much up elevator to feed in before the wings explode, or how much to feed in without pulling the wings off. The second time, I just put it into a spiral. To me, the spiral was much safer. Oh yes, my plane is a Riser 100.

[Libelle201B]

Lot's of good suggestions for sure. Depending on your flying skill I would not recomend going inverted, unless you know your plane, it's strength, and your ability to fly inverted for any length of time. It's not very easy to roll a polly ship inverted, a loop too inverted is much easier. Do you have enough down elevator travel to maintain level flight inverted? In any case you had better, along with the ability to control the plane's direction. If you don't, your plane will continue to increase it's speed and desent angle while inverted. At some point in this scenario, you may panic (unless you know how to roll your sailplane out of the situation) and pull in up elevator. Bye bye wings. My suggestion would be to get comfortable flying your plane inverted before you try this meneuver to get out of a thermal.

[bobby legue]

Question please. Is a wing weaker upside down or right side up?
Bob

[cub_flyer]

Big boomer eat machines that are too light for the upper air. More mass equals lower rates of climb, and velocity to run out of trouble.
No spoilers equals inverted flght that generates good sink and steeper inverted glide angles, that become 'ushered' by high drag!

Just a question what if its a 40oz 2m that seems pretty heavy to me and i was in a boomer that gained aprox 800ft a min at about 2000 to 2500 ft i got nervous as a dime would have covered it up in the sky but 3 lbs is still heavy for a 2 meter so if its a big enough boomer weight isnt the issue just my 2cents

Cub

[bobthenuke]

One nice trick, and a lot of fun (assuming you're flying a full house ship) is to turn it on it's side and put it in a full slip...it'll be down in a hurry with little stress to the airframe. This was actually a WWI maneuver called a "Glissade" or something like that - French word - used to quickly lose altitude without ripping the wings off.

...bob

[BigTilly]

Question please. Is a wing weaker upside down or right side up?
Bob

Bob, that is a great question. Typically, model plane wings fail at the center joint, where the bending moment from any load is the highest. If your joint is reinforced with glass on both sides, it will typically be stronger in upbending (a pull up from a dive) than in downbending, because the dihedral along the center axis tends to work the fibers on the bottom of the wing better than those on top.

Even if you have adequate joint reinforcement (wing failing mid span), then you are still more likely to fail in upbending. In this case, this has little to do with the wing being stronger one way or the other, but has to do with the wings ability to generate lift. In an undercambered airfoil, you can easily generate very large lift on the upper surface, leading to large upbending loads. It is difficult to generate that much lift on the lower surface, so the negative g loads are much smaller. No matter how much you push on the stick, the loads just won't be as high as if you pull.

[schrederman]

Glissade... Well I think I did something like that with my Yardbitd a couple of weeks ago, only from about 80'... :eek: ... As hard as she hit, I thought she'd be a basket case. I can assure you I didn't say glissade... it was something more like ... never mind. Very little damage, to my surprise, and she's already flying again... that is as soon as the 40+ mph winds die off. :D

Jack

[bobby legue]

Big Tilly,
Thanks for the answer. I thought maybe that the answer was so simple no one wanted to reply. The reply seems logical and it does fit what In was thinking. I have heard of a lot of people reccomending that inverted flight was a good way to get down from a boomer. Thats what lead me to think a wing may be stronger upside down.
I thank you for your time,
Bob

[oneniner]

There is a safe and effective method for this that applies to most gliders: SPIN IT. Pull into a full stall, and holding full up elevator, crank full left or right. As long as you hold full up, most gliders should stay in a nice spin.

A spinning airplane is stalled on the inside wing, and still flying a bit on the outside wing. It is actually a rolling motion, with the nose well below the horizon. The advantages to this method are:

1. It does not place much stress on the airframe as a high speed dive will.
2. It follows a predictable path downward.
3. It is relatively easy to see what is happening when it spins, as opposed to
trying to see which way it is pointing at a long distance.
4. The fact that one wing stays stalled guarantees a high sink rate, with a moderate airspeed.
5. Most thermal types, especially those with lots of dihedral and good pitch stability will recover from the spin upon releasing the controls.

When the plane gets low enough to see well, and you think you are out of the main lift, release the controls. Then you may have to fly the plane to get it to recover to level flight after it stops spinning and pitches up.

You may want to practice this a bit when nice and high, but not so far away you lose perspective. See how your glider reacts and recovers. I have used this method to bring down specked out polyhedral floaters, an Explorer, a Chuperosa, and others. I am not sure it would work well on a combat wing type or some such with neutral pitch stability. And some, including some Zagi's may not recover from a fully developed spin.

Gary

[Desert flier]

I have tried to spin my bubble dancer and it develops into a spiral dive after 2 or 3 rotations not that good. :D

[Fred_L]

In my experience an aircraft with a forward CG will be difficult to spin. To keep the inside part of the wing in the stalled condition you need good elevator authority. ELevator authority is enhanced by a rearward CG. With insufficient elevator authority the wing will unstall itself and gather speed leading to a spiral dive. Spiral dives are not gentle on the airframe.

I have a Zagi 5C and it spins just fine. I normally fly it with the elevator on a low rate (50%) as like all wings and planks it is pitch sensitive and I want to retain the full aileron throws for a good roll rate. I switch the elevator to high rates (100%) when I want to spin. A little proverse aileron helps it to get a good rotation rate going once the spin has started. Recovery is standard, just relax the controls, the rotation stops, the aircraft accelerates due to its nose down attitude and you pull up when flying speed is obtained. I have a plank type wing and it is the same. My mini ellipse however will sometimes continue to rotate for 1.5-2 rotations, after the controls are centred, before it stops rotating. Apparently some aircraft are difficult or impossible to recover from spins due to control surface shadowing. Practice with more than sufficient height for recovery, until you know your aircraft's characteristics.
F

[Desert flier]

Maybe next time i will build a larger elevator . For general flying it is enough loops stall turns and inverted but as you say it may need more authority to hold it in the spin . But having spoilers helps to come down quicker