NTSB Factual Report

On June 10, 2012, approximately 1100 mountain daylight time, a Griffiths Kokopelli Superpacer, N8VX, was substantially damaged during a ground loop while landing at Kremmling (K20V), Colorado. The private pilot and flight instructor were not injured. The instructional flight was being conducted under the provisions of 14 Code of Federal Regulations Part 91 without a flight plan. The cross-country flight departed Broomfield (KBJC), Colorado, and had landed at K20V.

According to the flight instructor, the purpose of the flight was to give the owner-pilot mountain flying experience. During the taxi to Broomfield’s (KBJC) runway 11L, the instructor remarked to the owner-pilot that it seemed like he was using more brakes than rudder. The pilot said that this particular airplane required brakes for steering. The windsock indicated the wind from 150 degrees at 15 knots and gusting. During the takeoff, the pilot swerved across the runway centerline several times before aerodynamic control speed was achieved.

Upon arrival at K20V, the wind sock indicated the wind to be from 250 degrees and less than 10 knots although it was gusting during the approach and landing. The owner-pilot landed the airplane and maintained runway centerline until it had slowed below aerodynamic control speed, then the airplane swerved across the centerline several times before slowing to taxi speed.

The pilot and instructor inspected the spring connections between the rudder and tail wheel. The owner said he had had some discussions with other amateur homebuilders as to what the spring tension should be. Some said low tension, others said high tension. The owner said he preferred low tension. The instructor said the springs on his Cessna 140 were tight and he maintained high tension. They both agreed, however, that the tail wheel assembly looked normal and they deemed it to be airworthy.

Before continuing to Glenwood Springs (KGWS), where the runway was shorter and narrower, the instructor offered to fly the airplane, remain in the airport traffic pattern, and land to ascertain directional control and stability. The owner agreed. During the taxi, the instructor applied full left rudder, then full left brake, in an attempt to make a left turn. Unable to do so, the owner-pilot taxied forward, turned left and right, and stopped. Both the instructor and the owner-pilot agreed that there was control continuity and everything was working properly. The instructor back-taxied from the mid-field ramp to the runway and was able to maintain directional control with rudder and brakes. During the takeoff roll, the instructor was able to maintain directional control, but it required significant rudder and brake application until aerodynamic control speed had been achieved. He flew straight and level, made some turns, and then completed a slip with full control deflection in both directions. The airplane responded normally.

Full flaps were deployed and 65 mph approach speed and 500 fpm descent were maintained to runway 27. The airplane touched down at the 1000-foot marker in a 3-point attitude and aligned with the runway. As it slowed, it began drifting to the right. The instructor applied left rudder, then applied full left rudder to the stop, then he applied left brake, followed by full left brake in three repeated applications. There was no directional response to the control inputs. As the airplane slowed, the instructor determined that if he were to power up for a go-around, the airplane would exit the runway and nose over. He determined that on the current ground track, while holding full left rudder and full left brake, the aircraft would miss the runway lights but would go off the side of the runway. The airplane exited the runway, bounced, and ground looped to the right. The left main wing, horizontal stabilizer and elevator were bent and the aft fuselage was twisted.

The instructor surmised that spring tension of the rudder and tail wheel cable was set too low. In addition, the left wheel brake was ineffective, possibly due to air bubbles in the brake line since the owner had recently bled the system.

NTSB Probable Cause

The low spring tension of the rudder and tailwheel cable, which resulted in the loss of control as the airplane decelerated after landing.