How to Groundloop

[n2582d]

As I've browsed NTSB C-170 accident reports and looked at salvage aircraft for sale I'm struck by the number of 170's totalled because of "loss of directional control" or more succictly--groundlooping. I was taught to fly taildraggers by Cecil Davis, an ex-WWII pilot who went on to fly for MAF. Obviously we're all taught how to avoid groundlooping a taildragger but how many here were taught what to do once in a groundloop? I just reread Wolfgang Langewiesche's chapter on "The Landing Run" in Stick and Rudder and was surprised no mention was made of this. In a groundloop, the natural tendency is to apply brake and rudder to counteract the groundloop. In the illustration below one would want to input full left rudder and brake. But what Cecil taught me was that if you find yourself in this situation--like the top aircraft in the illustration shows-- before the inside wheel lifts up and the plane starts to pivot on the outside wheel, release the brake on the outside wheel and apply the brake to the wheel on the inside of the turn (right brake in the illustration below). The idea is that the plane will pivot around on the inside wheel rather than the outside wheel and thus hopefully avoid damaging the aircraft. Is this common knowledge or something different than you've been taught? Looking at the accident reports it must be news to some of us.

Groundloop1.jpg

[FredMa]

I don't think braking of any kind would be heplful once the aircraft is basically going sideways down the runway. At that point you are basically insignificant for the remainder of the event.

[voorheesh]

I believe the velocity of the aircraft has a lot to do with how it behaves during a ground loop. If it is slow or stationary, it will pivot around the inside main wheel and spin harmlessly. If it has any significant forward motion such as in landing or takeoff, it will start skidding and tipping to the outside regardless of what the pilot does. It reaches a point where the controls Brakes/rudder can not overcome the centrifugal force. Some instructors say that once it goes, just keep the yoke back and apply even brakes to slow it down. The worst damage I have seen has been when the pilot attempts to go around during a landing after a ground loop has developed. This typically results in the aircraft becoming inverted after hitting even the slightest resistence such as mud, a rut, etc. I have interviewed several pilots who have been involved in ground loops and they all remark on how suddenly the swerve develops and how quickly the total loss of control occurs. These pilots have ranged in experience from beginners to a highly experienced tailwheel instructor. The majority of the incidents I have investigated do not occur in strong cross winds and the pilots are usually at a loss to explain what or why, other than simple miss handling the controls just prior to the groundloop.

[n2582d]

I don't think braking of any kind would be heplful once the aircraft is basically going sideways down the runway. At that point you are basically insignificant for the remainder of the event.

Unless you are on ice or very wet grass, i.e. no friction, I don't think the aircraft will ever just slide sideways. (Been there, done that ). Because the center of gravity is behind the wheels the tail will continue to swing around in an ever tighter arc until the plane is pivoting on the outside tire (assuming that the inside brake is not applied).

[bagarre]

I have interviewed several pilots who have been involved in ground loops and they all remark on how suddenly the swerve develops and how quickly the total loss of control occurs. These pilots have ranged in experience from beginners to a highly experienced tailwheel instructor. The majority of the incidents I have investigated do not occur in strong cross winds and the pilots are usually at a loss to explain what or why, other than simple miss handling the controls just prior to the groundloop.

I haven't looped an airplane on the ground yet but have come real close a few times. Each time, it seemed like I came out of nowhere! Afterwards I realized it came out of somewhere I wasn't paying attention to. The only way these ground loop (mechanical issues aside) is because we let them (we don need to make them, they already want to). In my case, it's playing with the flaps or reflecting on my touchdown but the distraction prevents us from noticing it develop.

Once you're in it and can't recover, it makes some sense to apply inner brake and rudder to get it around and over with. It may not work every time (nothing will) but the idea makes sense.

[Metal Master]

My partner in our 170A is also my primary flight instructor. Between us we have both a 140A and the 170A. My tail wheel instruction began in the Citabria. Rev learned to fly in the 1940’s he was taught as a regular part of his flight instruction in conventional gear aircraft that ground looping was normal procedure to prevent overrunning a short runway or to save an aircraft from an unintentional ground loop. As a part of my training I was taught to ground loop the Citabria from a slow taxi all the way to middle landing speed about half way through the landing roll. We did this over and over again until I was calm about performing the maneuver. We also performed the same in both the 140A and the 170A.
Having rebuilt both the 170A, a Maul M220-C and a Cessna 185AF after ground loops I have some experience dealing with ground looped aircraft. The damage in all three aircraft was similar. Except of course the Maul which is steel tube structure. I bought the 170A from the previous owner who had ground looped the aircraft through E-bay. The 170A in a right rotating ground loop, tripped over the outboard gear, broke both main gear bulkheads completely in half, collapsed the gear under the fuselage collapsed both of the center cabin bulkheads and broke the door post, and then bent the wing outboard of the strut when the aircraft fell after the gear collapse. This was exactly the same done to the 185. The P-Ponk gear mod would not have saved either the 170A or the 185AF as it took the entire bulkheads with the gear. Although I recommend the P-Ponk mod.
I have saved the 170A using intentional ground loops twice. The second time the tail was in the air when it unexpectedly started to go around. I was aggressively braking trying to see what it would do and trying to control the tail lift caused by aggressive braking. I have learned what I needed to from that. The first time had to do with a failed left brake. It saved two aircraft in that intentional ground loop. My aircraft and the one I could have ran into had I not intentionally ground looped the 170A.
The procedure that you outlined is the same that I was taught with the added part of rolling the aileron into the direction of the ground loop. This puts the out board aileron down and helps keep the airplane from tipping towards the outside of the loop. The aircraft makes about a 180 degree turn in the direction of the ground loop and calmly comes to a stop.
The three aircrafts mentioned here ground loop damage was incurred on dry runways. The 170A on dry grass. The pilot’s explanation in each case was that the aircraft started to ground loop and they fought the ground loop well to the point that the aircraft was skidding sideways until the aircraft tripped over the left main gear, breaking the gear loose from the structure in the process tearing the structure. Then the wing dropped onto the runway bending the wing outboard of the strut.
My read is that the procedure I was taught works. Good luck finding an instructor that can teach it or believes in it.
Regards,
Jim

[Metal Master]

Here are a couple of pictures of the ground looped 170A.
Regards,
Jim

[bagarre]

MetalMaster, That has to be one of the best posts I've read in a long time!

I've always been taught that a groundloop puts tremendous loads on the airplane. Are you saying it can be done safely and under control without damage to the aircraft? This would be an incredible thing to be able to practice but I don't want to risk damaging the plane.

Maybe I should find a Citabria to rent

[n2582d]

MetalMaster, That has to be one of the best posts I've read in a long time!

I agree! Great post. The idea of using ailerons as well is something I hadn't considered. I used this technique one time in a Beech 18T. (It was a Hamilton conversion -- taildragger with PT6's). Going aggressively into beta I found that the throttles were not matched so I got reverse earlier on one side than the other. The resulting groundloop sure did a number to my self-esteem but didn't damage the plane at all. I'd like to think using the technique described above helped avoid damaging the plane but who knows. With the wide gear and low wing I think the Beech 18 is less likely to end up scraping a wingtip than a C-170 in a groundloop.

[DaveF]

The procedure that you outlined is the same that I was taught with the added part of rolling the aileron into the direction of the ground loop.

My first tailwheel instructor taught me this technique. He made me demonstrate taxi and takeoff with feet on the floor, using only adverse yaw for steering. It's amazingly effective, even at very low speed. The hardest part is learning to turn the yoke (or move the stick) in the direction you don't want to go.

We already do this when we put aileron into the wind to combat weathervaning when taking off or landing in a crosswind. When I was learning to fly in a tricycle gear it was never explained as yaw control and I never made the connection. Just another reason I wish I'd learned to fly in a tailwheel airplane.

[GAHorn]

I believe some groundloop accidents are inadvertently contributed as the result of subconscious "steering wheel" activity. If the airplane is turning right in a developing ground-loop, the subconscious may turn the "steering wheel" in the direction to counter that right-turn... in other words, left-bank....which actually exacerbates the wing-to-ground contact and increases adverse yaw on the right-wing (providing UP lift on the right wing.)

However, describing the technique of "deliberate" ground-looping can be misleading to someone who may be less-experienced. Applying right brake to an airplane groundlooping to the right, should only be done after that right wheel has slowed virtually to a stop, or has actually begun a rearward-rolling action as the airplane exceeds the 90-degree point in the loop. That might not be apparent to a tailwheel-newbie, and not for the faint-of-heart when done at speed.

One way to think of it is to imagine arriving at a parking place at a slow taxi and intentionally applying one brake to create a short-turn, then releasing the brake (and tapping the opposite one) when the aircraft has turned 180-degrees.. If done with finesse, the aircraft can still carry momentum which has been reversed... and the aircraft will "back down" into the parking spot. (Multi-engined sailors might be able to imagine the technique if they've ever powered a twin-engined boat into a slip by using opposite-throttles to reverse heading, then dual aft throttles and "backing down" into the slip.)

[blueldr]

Sounds like the method used to back up a B-17.

[wingnut]

Sounds like the method used to back up a B-17.

Or a D6

[blueldr]

Del,
I used to operate a Cat D6 for Sam but it had a "Johnson Bar" and was really simple to back up. Just declutch, throw the JB,
and reclutch.

[bagarre]

http://m.youtube.com/watch?v=iFvD7Ok0ghY