Witnesses Say Pilots Were Performing Aerobatics

A Christen Eagle II that went down last year in Iowa may have been overweight and at the limit of its CG envelope for aerobatic flight, according to the NTSB Factual report issued on the accident this week.

As was reported in Aero-News, the two men onboard the small biplane died when the aircraft went down southwest of Iowa City on March 27. Witnesses at the scene told authorities the pilot had been performing aerobatic maneuvers, including flips and barrel rolls, prior to the accident.

The NTSB stated the aircraft's designer specifies a published rearward CG limit for flight within the acrobatic category of 99.60 inches, at a maximum gross weight of 1,520 pounds; and 100.40 at a weight of 1,450 pounds.

Investigators studied three scenarios with differing amounts of fuel onboard, according to the report, and found the aircraft may have been as much as 97 lbs overweight when the accident occurred, depending on fuel load. In both scenarios, the CG may have been anywhere from .2 to .3 inches outside the aft limit for aerobatic flight.

With 1/4 tank of fuel onboard, the aircraft would have been barely within its gross weight restriction (by only nine pounds) -- but the CG would have been .3 outside the envelope for the Christen Eagle II.

The findings are significant, as witnesses reported the aircraft entered a flat spin prior to impacting the ground. The reported gross weight and center-of-gravity conditions would have made it very difficult to exit such a maneuver, according to the NTSB.

The Christen Eagle Airplane Flight Manual is also very empathic on the subject.

"Any particular Christen Eagle II aircraft will recover from any spin type using standard recovery techniques ONLY IF THE AIRCRAFT IS PROPERLY BALANCED," it states. "The CG of the aircraft must be within design limits to ensure safe spin recovery. Any aircraft can be dangerously loaded (CG beyond design limits) making spin recovery extremely difficult or impossible. Weight and balance considerations must be taken seriously and pilots must be absolutely certain that the flight CG of their aircraft is within design limits."

And while it's not evident if it would have made a difference, the two victims -- David Culbertson and Steven Redman -- also were not wearing parachutes. FAR 91.307 requires parachutes to be worn anytime the pilot:

1. Banks the aircraft more than 60 degrees relative to the horizon; or
2. Pitches the nose up-or-down at an attitude of 30 degrees or more relative to the horizon.

NTSB investigators stressed the report does not specify a cause of the accident, adding the Probable Cause report may not be issued until later in the year.

FMI: Read The Factual Report