Ground Looping

[kgwilson]

So ... the problem here, isn't related to weakly-constructed landing gear?

 

This is a classic example of how not to land. Porpoising 8 times & the nosewheel only left the ground once after the first one. It is amazing it lasted as long as it did.

[kaz3g]

Now this is a wheeler! Done by a pilot who flew it (new) in 1961

happy days,

That’s very nicely done.

[Mike Gearon]

Motorbikes mostly fix themselves if you add power and that’s pushing from the back into whatever mess you’ve got yourself into. The props even better from the front.

[facthunter]

Not sure a comparison takes you where we need to go. Power to the rear wheel gets the weight off the front one so it's not twisting the frame, if that's the problem on the bike.. Ground looping is different.. It's not something you practice though.

Any "problem" I've had is with pupils who lose control, But I've always managed to recover it EXCEPT for ONE where the plane ground looped a full 360 degrees right in a couple of seconds at most. I don't know how the tires stayed on the rims. My neck got severely kinked but my head hit nothing such were the forces. The plane then trundled straight along the runway as if nothing had happened. I reckon the pilot landed with one brake on and the plane just went straight into it. There was really no time to do "anything" with this one. So far I've not done one solo and I hope it stays that way.. No one can really say It won't happen...The joys of tail wheeling. Nev

[Mike Gearon]

Not sure a comparison takes you where we need to go. Power to the rear wheel gets the weight off the front one so it's not twisting the frame, if that's the problem on the bike.. Ground looping is different.. It's not something you practice though.

Any "problem" I've had is with pupils who lose control, But I've always managed to recover it EXCEPT for ONE where the plane ground looped a full 360 degrees right in a couple of seconds at most. I don't know how the tires stayed on the rims. My neck got severely kinked but my head hit nothing such were the forces. The plane then trundled straight along the runway as if nothing had happened. I reckon the pilot landed with one brake on and the plane just went straight into it. There was really no time to do "anything" with this one. So far I've not done one solo and I hope it stays that way.. No one can really say It won't happen...The joys of tail wheeling. Nev

The joys of instructing as well!

 

Motorcycle very different. Only similarity is power on can fix problems where it’s a trained response and not a natural one.

[Yenn]

Watching that video clip reminded me of a similar landing at Old Station. He only did 3 bounces before it all fell apart. At the end the prop had a 90 deg bend at 50mm from the tip and another at 150mm. Plenty of damage to front of fuse.

The video clip just shows how it should not b done and I wonder how that pilot ever got to get a licence.

[SkyHigh]

OK, I'll start the ball rolling. What is the main cause of ground looping?

Sorry I'm late to the conversation but I recently watched what I felt is a very good explanation of Ground Looping, and thought it worth a share (credit to the video creator)...

 

[turboplanner]

Sorry I'm late to the conversation but I recently watched what I felt is a very good explanation of Ground Looping, and thought it worth a share (credit to the video creator)...

 

Great explanation and practical story.

[planesmaker]

I might add wheel alignment can add to a cause. I checked one recently and found left wheel toed in a lot, I would think it would make landing interesting. Ended up replacing the gear leg.

[facthunter]

While ground looping is a great embarrassment potentially and sometimes scrapes a wingtip the"Normal" tricycle configuration can be just as dangerous if not a bit more when it's landed with the weight mostly on the nosewheel when you will be going much faster and frequently end up upside down and in a quite violent manner. The thing to avoid is getting the upwind wing UP at all where the X wind can lift it further and you will be slipping downwind and if you contact the runway it will place a hell of a side force on the U/C. You can really not force a plane onto the runway when it's going too fast very safely unless you have lift destroying devices like ground spoilers. Approaching too fast is usually a feature of flying at an aerodrome far too big for your requirements and you get lazy because you CAN. Being at the approach speed a long way out is not smart either especially if it's turbulent as it's all extra work..

Heavy stuff manuals specify in the slot (stabilised) at 400 feet or even higher. I'm not going to get into specifics here and now, but certainly at some point ,significantly above where you intend to flare, the sink rate and your speed should be appropriate for you to have a good idea where and how you will touch down. Nev

[Yenn]

It sems that a lot of those heavy stuff manuals don't get the attention they need. Professional pilots seem to be getting less professional lately.

[facthunter]

" Stabilised by" doesn't tell you how to fly Yenn. When you watch a lot of "U tube on bad weather landings, you see the good and the bad TECHNIQUE being used. The Heavy stuff has "inertia" to help or impede a good result depending on your technique and co-ordination.. Hardly works at all for U/L's where the X wind just blows you away as soon as you aren't crabbing unless your wing is down. Nev

[turboplanner]

A tail wheel aircraft is dynamically unstable. The design comes from the very early times where the fine points of Engineering knowledge weren't what they are today.

Cars and trucks of that era often were also dynamically unstable.

In the 19th century wagons were built with a wheel at each corner, so the centre of gravity was located within the wheelbase but when an engine and cab were added the tray was just slid backwards overhanging the rear wheels and the early trucks were quite unstable. This was because the centr of gravity was often behind the rear axle, so the downforce was in cantilever.

A cantilever load behind the rear axle levers the front axle up, and the mass of the front axle doesn't just disappear up into the air but is added to the rear axle.

So the front tyres didn't have the same grip. If you look down on the truck in plan view going around a corner, the centre of gravity behind the rear axles is pushing outwards and if it gets the truck around at enough angle will get it to swap ends.

 

In a tail wheel aircraft the centre of gravity is behind the mains and the moment arm from the CG to the mains is very short, while the moment arm to the tail wheel is very long, and in some cases only a skid is used, other cases the tail wheel is free wheeling.

 

If we disregard wind forces on the control surfaces and just look at mass and undercarriage points, we have a big mass located behind the wheels, and very little side thrust resistance from the tiny tail wheel.

 

So if the aircraft taxis on to a slope down from right to left, the left side of the aircraft is lower than the right and the aft CG will want to turn the aircraft to the right.

 

There is always some undulation in a strip, so this cantilever effect starts to magnify as soon as the CG gets slightly out of line, hence the need to be "ahead of the aircraft". Kinetic energy then kicks in and there's a point where the CG yaws the wheels into an out of control situation.

 

There are some quite large aircraft with fore and aft single wheels or wheelsets, and outrigger balanc wheels under the wings, and this design puts the CG between the wheels and makes the aircraft dynamically stable.

 

The tricycle undercarriage allows the CG to fall inside the wheelbase (CL from wheel to CL rear wheels), a dynamically stable design without the unexpected swing of the taildragger, so much more predictable without the constant threat of a ground loop.

[facthunter]

I'd question your second last para. The U2 is like that and is a particularly difficult plane to manage on the ground.

The tricycle is the best answer for most pilots as the weight carrying wheels are behind the planes Cof G giving it a natural directional stability at touch down if it's pointing slightly differently from it's direction of travel, UNLESS the forward located nosewheel takes the weight first..

I was trained from the beginning on tailwheel and used mainly 3 pointers. When (nearly) everybody went over to tricycle a lot of "wheelbarrow effect" accidents started to happen, which having always operated from a short strip I couldn't understand as we would try to just get the stall horn before touchdown anyhow. Flying it on would use too much runway. All proves you can't make a fully foolproof plane. Maybe the instruction doesn't emphasis this as much as it should and "fast" Landings can get you into trouble in other ways and it's harder on the plane and brakes as well. Nev

[turboplanner]

I'd question your second last para. The U2 is like that and is a particularly difficult plane to manage on the ground.

The tricycle is the best answer for most pilots as the weight carrying wheels are behind the planes Cof G giving it a natural directional stability at touch down if it's pointing slightly differently from it's direction of travel, UNLESS the forward located nosewheel takes the weight first..

I was trained from the beginning on tailwheel and used mainly 3 pointers. When (nearly) everybody went over to tricycle a lot of "wheelbarrow effect" accidents started to happen, which having always operated from a short strip I couldn't understand as we would try to just get the stall horn before touchdown anyhow. Flying it on would use too much runway. All proves you can't make a fully foolproof plane. Maybe the instruction doesn't emphasis this as much as it should and "fast" Landings can get you into trouble in other ways and it's harder on the plane and brakes as well. Nev

I just wanted to show the difference in the underlying dynamics, one inherently stable, the other inherently unstable.

 

Putting the flying surfaces back on my dynamically stable machine, there should NEVER be a situation where you land a tricycle undercarriage nosewheel first, so you should never experience the wheelbarrowing and dynamic slam dunk, but................... On this site some years ago a well known instructor was teaching students to point the nose down for landing and use the yoke to lose height and the throttle to adjust speed, and defended it even as students were bouncing and writing off nose wheels.

 

You are supposed to land on the same two wheela as you do with a tail dragger, so the approach is tail down, using the yoke to adjust speed and the throttle to adjust altitude, so you will be landing on the mains and the yoke will be coming back until it's all the way back and the nose wheel gently touches at slow speed.

 

I'm not a promoter of learning to fly by correspondence, so if you are doing something different, talk to your instructor and get him/her to teach you in real time with real inputs.

 

The U2 was an exception in that it landed long and fast and the stabiliser wheels were fitted by a chase car after it had landed. The link shows Area 51 and Groom Lake. You can see the U2 and Oxcart tracks off the end of the runway and following a circular pattern around the lake. The planes I was thinking of were heavy bombers where it must have had some attraction.

https://commons.wikimedia.org/wiki/File:Area_51_Groom_Lake.jpg

[facthunter]

In all fairness the U 2 s great wingspan makes it directionally "different" also with inertia effects of the wings but making it like a pushbike requires it to lean. Early planes were quite high to clear the large props of the day and consequently, with narrow undercarriages, steered like a double decker bus and used steering techniques that would seem strange to us today if we didn't analyse the situation. Ie a wing rising is lowered by turning away from the rising wing thus "tipping" the plane back level. Also planes were not on strips but all over fields so could take the "into wind" option. On windy days also they often stayed in the hangar, and a lot of the flying was done in the mornings and evenings. This was well documented at the time and a lot of this material is very interesting to students of skills and thrills of aviation. Plenty of the very basic U/Ls are not very good with coping with winds. A slow stall speed and light wing loading means wind and gust sensitivity is part of the equation... Nev

[CT9000]

I have well over a thousand hrs. in my Skyfox and can say that it is not a good idea to three point it in a crosswind. A tail low wheeler is the best option and the runway length needed is not much different to a three pointer. I always use forward stick to keep the tail up as long as possible on roll out. What happens in the flare for a three pointer is that the wing masks the rudder and you can feel the rudder getting progressively softer as the angle gets steeper. Also if you are going to rely on the tailwheel for directional control you are going to ground loop for sure. It will unlatch right when you need it the most. Rudder is king and the landing is not complete till the billy is on. I agree with Nev that some a/c are better to 3 point and others not, some don't matter either way.

I am happy flying in gusty crosswinds in the Skyfox or the CT. you just have to be awake and pay attention. Greg

[facthunter]

I remember way back at Narromine with a group of crusty old Instructors when one commented on the difference between the docile and very controllable Gazelle and the Near the same but with tailwheel, Skyfox. being a "real bastard" on the ground. . If I've tried to 3 point it wouldn't be that often. The rudder doesn't do much when it's got the tailwheel on the ground. I'm inclined to think the square fuselage is mostly the culprit putting mucked up air over it. Some speedy small finned tailwheel planes of the 30's era required you get the tail on and hold the stick firmly fully back and steer only on a well set up tail wheel as the shielded rudder couldn't be relied on. Nev

[Mike Gearon]

On 14/08/2019 at 11:21 PM, NT5224 said:

I've never ground looped yet, but have come close.  The  Rebel is surprisingly merciful  as a tail dragger,  compared to  lighter aircraft such as the Lightwing.  But its  a challenge to respond to cross wind gusts  (or bumpy uneven surfaces) with corrective rudder inputs without over-correcting  and establishing a pattern of increasing oscillations. 

 

Here's my  personal tip (which some will disagree with!).  On take off with a tail dragger I never just shove the throttle full open, because  a sudden  rudder input to correct the centrifugal yaw could establish that oscillation.  Instead I apply power steadily , and introduce the appropriate level of  rudder accordingly as we get going. I can still get off really short doing it this way. 

 

 

I’m learning tail wheel right now and we do a steady 1,2,3 count power up. Rudder accordingly. I also discovered one should not shove the throttle forward for a go around after failed wheel landing (or anytime really!) A steady 1,2,3 is plenty of time before the bounced wheel landing wants to return to the runway.

[facthunter]

"Smarties" can do the immediate tail lift but one day they will lose it. Raising the tail has a gyroscopic effect. Crosswinds can affect how much rudder you have left to correct YAW. On some tailwheels you have to run straight for a small distance to lock the steering aspect of the thing. If your plane has an undersize rudder this can be critical. to keeping straight.. A rapidly opened throttle can cause the engine to falter. It's not particularly good for them to do this. Nev